University of Southern California Dissertations and Theses

The creation of a novel full-coverage orthognathic surgical splint utilizing 3D printing & virtual surgical planning

(USC Thesis Other)

The creation of a novel full-coverage orthognathic surgical splint utilizing 3D printing & virtual surgical planning

PDF

Download a page range

Download transcript

Copy asset link

Request this asset

Transcript (if available)

Content

THE CREATION OF A NOVEL FULL-COVERAGE ORTHOGNATHIC SURGICAL
SPLINT UTILIZING 3D PRINTING & VIRTUAL SURGICAL PLANNING
By
Ryan Hungate

A Thesis Presented to the FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements
for the Degree MASTER OF SCIENCE (CRANIOFACIAL BIOLOGY)

May 2015

Copyright 2015 Ryan Hungate

2
Acknowledgements
I would like to give special thanks to Dr. Glenn Sameshima, Dr. Dan Grauer, and Dr.
Robert Relle. Your knowledge and guidance throughout the creation of this project has
been priceless. Together, I know we will change orthodontics and orthognathic surgery
forever. I would also like to thank my beautiful wife Lauren. Throughout my journey in
dental school and orthodontic residency, you have been my rock and my drive for
succeeding. I love you.

3
Table of Contents

Acknowledgements 2
List of Figures 4
Abstract 5
Chapter 1: Background 7
Epidemiology 7
Orthognathic Surgery Statistics 10
Traditional Surgical Planning & Surgical Splints 11
Traditional Plaster Model Surgery Protocol 12
3D Imaging 16
Virtual Modeling & 3D Printing 21
Data Acquisition 22
3D Printing in Medicine 25
Virtual Surgical Planning 30
Chapter 2: Materials & Methods 35

Chapter 3: Discussion 46
Advantages 51
Disadvantages 53
Improvements to be Made 54
Chapter 4: Conclusion & Clinical Relevance 56
References 57
Appendix 62
Provisional Patent 62
Full Coverage Splint Methodology Flowchart 73

4
List of Figures
Figure 1. Laser Surface Digitizer Schematic 24
Figure 2. Principle of Rapid Prototyping 27
Figure 3. Schematic of SLA 28
Figure 4. Intra-Oral Scanning of Dentition 36
Figure 5. Box Laser Scanning of Maxillary Arch 38
Figure 6. Box Laser Scanning of Mandibular Arch 39
Figure 7. Box Laser Scanning of Bite Registration 39
Figure 8. Box Laser Scanning of Maxillary Arch 40
Figure 9. Post Model Surgery Aligned Arches 40
Figure 10. Post Model Surgery Maxillary Arch 41
Figure 11. Post Model Surgery Mandibular Arch 41
Figure 12. Finished 3D Printed Biocompatible Splint (Occlusal View) 43
Figure 13. Finished 3D Printed Biocompatible Splint (Labial View) 44
Figure 14. Lateral View of Anterior Segment Torque 52

5
Abstract
Background: Orthognathic surgery is difficult to plan and execute for both the
orthodontist and oral surgeon. Though recent strides in technology and diagnostic tools
have been made, connecting these tools has not been accomplished in an efficient
manner. The advent of virtual surgical planning has brought a new level of detail to
surgery, but the execution is still difficult when applied in a clinical setting. By
combining 3D printing and virtual surgical planning, a better resultant surgical result
may be achieved.
Purpose: In this project, the purpose was to combine existing methods of surgical
planning to create a novel full-coverage surgical splint that allowed for better
communication between the orthodontist and oral surgeon and to enable a better
patient outcome from an increased accuracy of surgical splint and decreased patient
finishing times using clear aligner therapy.
Methods: Immediately prior to surgical workup, braces or clear aligner therapy
attachments are removed if present so that all surfaces are smooth. The novel full-
coverage splint is designed and manufactured using intraoral scanning of the pre-
surgical dentition and CAD/CAM creation on a 3D printer. Orthognathic surgery is
completed using the full-coverage splint(s) and Maxillomandibular fixation is applied by
means of skeletal anchor screws placed at the start of surgery. Post-surgery protocol is
completed using clear aligner therapy and the initial clear aligner tray is delivered 2-3
weeks post surgery.

6
Discussion: The current golden standard for orthognathic surgical planning is still
utilizing a plaster model for model surgery and then hand fabricating an acrylic splint.
Only the most forward thinking surgeons are utilizing the cutting edge technology of
virtual surgical planning and taking CBCT scans of their stone models to have an
orthognathic surgical splint wafer printed. There exist inherent flaws with both the
golden standard and cutting edge methods of splint fabrication. The advantages of
using a full-coverage 3D printed splint are: 1) Increased accuracy of post-surgical
occlusion. 2) Increase in patient comfort and acceptance of treatment. 3) Accelerated
speed in post surgical orthodontic finishing.
Conclusion: By creating a more accurate and full-coverage splint, the following was
achieved: 1) Operating room time is decreased. 2) Patient outcomes, including fewer
complications and faster rehabilitation, have been improved. 3) Increased surgical
precision. 4) Increased communication between the doctor and patient, including better
surgical predictions. 5) Better communication between the surgeon and referring
orthodontist. 6) Highly predictable surgical results.

7
Chapter 1: Background

Epidemiology
Dentofacial deformity refers to deviations from normal facial proportions and dental
relationships that are severe enough to be handicapping. The affected individuals are
handicapped in two ways. First, jaw function is compromised. Extra effort and
compensatory motions usually allow successful chewing of the current soft diet. The
patients often avoid eating certain foods in public places because they cannot manage
them in a socially acceptable manner. Speech difficulties may also be present. This is
particularly prevalent in long faced, open bite deformities. Second, dental and facial
appearance often leads to discrimination in various social interactions. Facial esthetics
can influence many aspects of a patient’s life. Examples of this are that stereotypically,
an individual with a long face and open bite is considered unintelligent; a sharply
protruding chin can have an unfortunate effect on a woman’s appearance; and a weak
chin and protruding upper incisors may adversely affect a person’s chance of job
promotion. Recent data has shown that between one third and one half of patients
referred for evaluation may have high levels of psychological distress, high enough to
predict continuing problems in interpersonal relationships and significantly affect overall
quality of life.(Proffit et al., 2003)

Dentofacial patients almost always have a severe malocclusion, but the malocclusion is
not the defining feature of the condition. Orthodontic treatment may correct teeth into
the proper dental relationships, but may not effect the underlying skeletal problems

8
enough to overcome the psychological handicaps. For this reason, surgery to
reposition the jaws (orthognathic surgery) often is required for successful treatment, and
soft tissue surgical procedures also may be required.(Proffit et al., 2003)

When asking the question “Who is a candidate for orthognathic surgery in addition to
orthodontic treatment?”, the simplest answer is if there is a severe skeletal or very
severe dentalalveolar problem, too severe to correct with orthodontics alone. If the jaw
correction is correct, crowded and malaligned teeth almost always can be corrected by
orthodontic tooth movement alone. However, there are limits to how far a tooth can be
moved, and these limits become important when bite relationships must be changed to
correct overjet, reverse overjet, crossbite, deep bite, or open bite cases. If a
discrepancy in the size or position of the jaws contributes to the malocclusion and is
reflected in improper facial proportions, there are only three possible treatment
scenarios: 1) modification of growth; 2) orthodontic camouflage (correcting the teeth to
create the correct dental relationships in spite of the jaw deformity) and produces a
dental compensation for the skeletal discrepancy; or 3) surgical repositioning of the jaws
and/or dentoalveolar segments.(Proffit et al., 2003)

In a patient too mature to grow much more, the only possibility for orthodontic treatment
alone is camouflage by displacement of the teeth relative to the jaws. Extraction of
some teeth to allow enough movement of the others will probably by required. Recent
developments in the use of implants for anchorage are a making orthodontic
camouflage an easier choice. The resulting dental compensation may produce a

9
reasonably normal dental occlusion, but as with a growing patient, the result is
satisfactory only if facial proportions as well as tooth relationships are acceptable.
Major tooth movements may correct the dental occlusion without improving dental and
facial appearance, or even make facial esthetics worse. The essence of camouflage
treatment is to improve facial appearance as well as the dental relationships.(Proffit et
al., 2003)

Once growth has stopped, surgery is the only way to correct a jaw discrepancy, when
compensation for camouflage is not desirable. The more dental compensation present,
the less the surgeon can correct the jaw relationships without producing malocclusion.
This is true whether the compensation occurred naturally or was introduced by
orthodontic treatment and explains why “reverse orthodontics,” deliberately makes the
occlusion worse initially, and is often necessary in preparing the jaw for surgery. If the
tooth relationships are not the limiting factor, it is nevertheless true that there are limits
on how far the jaws can be moved surgically, but these limits are larger than the limits of
camouflage and growth modification treatments.(Proffit et al., 2003)

It is important to note the limitations of surgery and tooth movement. It is obvious that
greater change can be produced in a growing child by a combination of growth
modification and tooth movement than could be produced in a non-growing patient by
tooth movement alone. In an adult, camouflage of a jaw deformity must be produced by
orthodontic tooth movement alone. This makes the question of the limitations for
correction of a deformity by orthodontic tooth movement alone much more clear. A

10
problem in a child is too severe for orthodontic treatment alone if it cannot be corrected
by a combination of growth modification and camouflage to the point that both dental
occlusion and facial proportions are acceptable. In an older individual, if the jaw
discrepancy is too great to compensate and camouflage by tooth movement alone,
surgery is the best way to obtain an acceptable result. This declares the concept that
correcting the occlusal relationships of the teeth alone is not an adequate description of
successful treatment and that satisfactory facial esthetics must also be produced.(Proffit
et al., 2003)

Orthognathic Surgery Statistics
Almost no data exists for the prevalence of facial characteristics, so it is necessary to
infer the presence of jaw deformities from data on dental relationships.(Proffit et al.,
2003) In the United States, it is estimated that 17 million individuals aged 12 to 50
years have malocclusions severe enough to warrant surgical correction. Congenital
anomalies of the craniomaxillofacial skeleton affect a large number of children. The
most common abnormalities include cleft lip and palate (0.06% and 0.5% of the normal
population), cranio-synostosis, and hemifacial microsomia. The majority of the
aforementioned patients will need surgery. Finally, 5-15% of the population is reported
to have symptoms of TMJ disorders and although a majority of these patients do not
need surgical treatment, patients with TMJ ankylosis, sever rheumatoid arthritis, or
osteoarthritis may require TMJ reconstruction.(Xia et al., 2006) It has been estimated
that approximately 2.5% of the U.S. population has facial disproportions and severe
malocclusions that would put those individuals into the Dentofacial deformity category.

11
It has also been estimated that 5% of those who seek orthodontic treatment fall into this
category. Since about 50% of American children are judged to need orthodontics, these
numbers appear to be correct.(Proffit et al., 2003)

Traditional Surgical Planning & Surgical Splints
There are a number of problems associated with the traditional planning methods for
orthognathic surgery.(Ellis et al., 1992; Gateno et al., 2001; Gateno et al., 2007; Sander
et al., 1998; Santler, 2000; Xia et al., 2005) Each one of these problems can result in a
less than ideal surgical outcome. In isolation, these problems may be minor, but when
added together the results can be significant.(Xia et al., 2009) One of the most crucial
parts of surgical planning is the fabrication of the surgical splint. There are two
standards for accomplishing splint fabrication: traditional plaster model surgery with
acrylic splint fabrication and virtual surgical planning with 3D CAD/CAM fabrication
utilizing 3D printing.

The combination of craniomaxillofacial anatomy and the variation encountered by the
surgeon performing the reconstruction makes orthognathic surgery a conceptually
difficult task to explain, plan, and execute. Modern improvements in hardware and
software have allowed for better viewing of 3D images and for the added analysis of
volume and distance. This has then led to accurate simulation of osteotomies and
movement of bony fragments.(Mavili et al., 2007) Surgical splints are vital to
orthognathic surgery so that predictable results are obtained. This is especially

12
important in bimaxillary surgeries because of the complex movements being performed
in three different planes.(Xia et al., 2006)

Traditionally, an acrylic splint, fabricated from plaster models, is used to transfer the
pre-operative treatment plan to the operating room. This allows for accurate positioning
of the maxilla relative to the mandible or mandible relative to the maxilla depending on
the preoperative planning that was completed. When repositioning both the maxilla and
the mandible, an intermediate splint is also fabricated to align the osteotomized maxilla
to the non-operated mandible. A final splint is then used to position the mandible to the
repositioned maxilla.(Mavili et al., 2007)

The fabricated acrylic splints assist with the positioning of the dentition and alveolar
arches. During the surgery, it is still the job of the surgeon to determine how much
impaction or downfracture is needed to create the appropriate vertical length of the face
and to control the rotational movements in the distal mandibular segments.(Mavili et al.,
2007)

Traditional Plaster Model Surgery Protocol
Model surgery is the means of anticipating and resolving occlusal problems and
predicting the amount of bone removal or addition. The following is the traditional
method for performing plaster model surgery. Prior to taking impressions of the
dentition, mark the facial midline on the gingiva above and directly on the teeth. These
lines are then reproduced on the models when cast at a later time. Impressions are

13
taken of the upper and lower arches including the lingual and buccal sulci. The centric
jaw relationship is also taken with a wax wafer. Finally, a facebow is recorded.(Anwar
and Harris, 1990)

Prior to mounting the models on the articulator, the calibration on the articulator should
be set as follows: condylar track inclination set to 30°, condylar pillars is set are then set
to 15°, the incisal pin and table should be set at 0, and the anterior top screws for the
condylar spheres should be completely screwed in. The new working models are then
trimmed and articulated on a semi-adjustable articulator using the facebow recording
and the wax bite. This orients the plaster models to the Frankfort Plane and so the
orbital pin of the facebow makes the upper mounting plate of the articulator the
equivalent of the inferior orbital margin.(Anwar and Harris, 1990)

After the newly poured models are dry, the horizontal and vertical reference points are
drawn on the mounting plaster to register the position of each maxillary and mandibular
segment. This can be done by rotating the model on a flat surface while it is mounted to
its detached mounting assembly. The first line (A) should be clear of the apices of the
teeth and no less than 15mm from the second line (B). This will be done on both the
maxillary and mandibular models. The actual distance between lines A and B is then
recorded. This can be completed by writing it directly on the plaster models. Lines A &
B will be used to plan the vertical movements that will be performed in the actual
surgery. The distance between the maxillary and mandibular B lines will also be written

14
down and will indicate any change in facial vertical height.(Anwar and Harris, 1990;
Santoro et al., 2003)

Three vertical lines (VC, VB, and VM) are drawn from the maxillary base B line to the
mandibular base B line on each buccal segment. VC is drawn from through the buccal
surface of the upper cuspid, VB is drawn through the buccal surface of the upper
bicuspid, and VM is drawn through the distal cusp of the last upper molar tooth and all
three lines (VC, VB, and VM) are extended through their occluding teeth. These lines
will indicate the antero-posterior movements achieved by the plaster model surgery.
Connect the vertical reference points that we drawn on the casts by transferring from
the patient. This will indicate the facial midline. This vertical line must be confirmed
with the patient in the chair before proceeding with the plaster model surgery.(Anwar
and Harris, 1990; Santoro et al., 2003)

The vertical distances from the tips of the buccal cusps of the three reference teeth,
designated by the VC, VB, and VM lines, and the edges of the central incisors to their B
baselines are recorded to help calculate any vertical movements. Transverse changes
are recorded by the intercanine and intermolar distances measured across the palate
and are recorded by taking reference points on the canine tips and the buccal cusps of
the last molars. The distance from the midline at the upper interincisal edge to the
incisal pin is written down. This helps to measure the maxillary forward
movement.(Anwar and Harris, 1990; Santoro et al., 2003)

15
After all reference lines have been drawn and measurements recorded, osteotomy lines
are drawn to record where the osteotomy bone cuts will be located. These lines should
be dotted so that they are noted as different from the measurement lines. The mounted
plaster casts are then cut on the dotted osteotomy lines with a sharp saw and the
segments are repositioned in the post-operative positions. The surgeon must take extra
care not to damage any of the teeth adjacent to the osteotomy cuts being sawed on the
plaster models. The segmented maxilla pieces are placed so that maximum
intercuspation is present between the maxillary and mandibular arches and so that the
maxillary canines are in class I orientation to the mandibular canines. The pieces are
then locked into place using red beading wax, which will allow manipulation of the
segments into your desired position. Some cusps might need to be ground down to
achieve the desired occlusal positions. The cusps that are ground should be noted with
a marker and written down in another location to be referenced during the actual
surgery.(Anwar and Harris, 1990; Olszewski and Reychler, 2004)

After making the horizontal cut on the maxilla, the dental midline is rotated to match the
previously noted facial midline. This will rotate the model VB and VM lines on the
deviated side forward and the contralateral VB and VM lines will move backward. Mark
the new positions on the mounted plaster casts. Any additional forward movements are
then measured from the newly recorded vertical references. This is very important
during the actual surgical procedure where a significant rotation will increase the actual
forward movement on the deviated side but may make any movement on the
contralateral side very difficult to note.(Olszewski and Reychler, 2004) Antero-posterior

16
movements should be made so that an acceptable overjet and overbite is achieved. A
small degree of over-correction may be necessary to compensate for any relapse post-
surgery. This should especially be considered in surgeries where the mandible will be
moved forward. Post surgical eruption will spontaneously correct minor discrepancies
and otherwise post-surgery orthodontics will correct the remaining needed changes.
Once the desired position of the maxillary segments is achieved, the red beading wax is
replaced by hard modeling or sticky wax to secure the once mobilized segments in their
new positions.(Anwar and Harris, 1990)

3D Imaging
In the early 1980s, the American College of Radiology and the National Electrical
Manufacturers Association standardized the coding of images obtained through
computed tomography and magnetic resonance imaging. In1993, the term digital
imaging and communications in medicine (DICOM) was adopted.

A DICOM record
consists of: 1) a DICOMDIR file, which includes patient information, specific information
about image acquisition, and a list of images that correspond to axial slices forming the
3D image; and 2) a number of sequentially coded images that correspond to the axial
slices. When the axial slices are combined in the correct order they form the 3D
image.(Grauer et al., 2009)

Once a CBCT scan has been acquired, some basic handling and measurements on the
data set can be performed with the software provided by the manufacturers. CBCT
manufacturers also offer the option, through their software, to convert their proprietary

17
formats into an exportable DICOM file. When ordering a CBCT acquisition through an
imaging laboratory, the conversion of the images to a standardized DICOM file is
normally performed at the laboratory, and the patient or the clinician is given the DICOM
file. If the clinician owns a CBCT scanner, its software allows for exporting images in
DICOM format. Further research is needed to validate the process of converting
images from a proprietary format into a DICOM format.(Grauer et al., 2009)

The tools for visualization, landmarking, measurement, registration, superimposition,
and computation of 3D images are different from those used in their counterpart 2D
images.

The information obtained through 3D visualization in orthodontics has not been
completely linked to a diagnostic or prognostic meaning. When we observe a differently
shaped mandibular condyle, it does not necessarily mean pathology. Further research
should establish the links between observed morphology, pathology, pathogenesis, and
response to treatment. The legal implications of acquiring a CBCT image are also
important. More information than the conventional diagnostic records is obtained
through a full 3D image of the head and neck, leading to responsibility and
accountability issues regarding the diagnosis of pathology outside the region of
interest.(Grauer et al., 2009)

A 3D image is composed of a stack of 2D images or slices. A 3D image is composed of
voxels in a similar way that a 2D image is composed of pixels. Each voxel has a gray-
level value based on indirect calculation of the amount of radiation absorbed or
captured by the charge-coupled device and calculated through a filtered-back projection

18
algorithm. Visualization is based on a threshold filter. This filter assigns a binary value,
either transparent or visible, to each voxel based on its gray-level value. The user
defines the critical value that splits the voxels into visible and invisible. The result is a
rendered image on the screen composed of all visible voxels. The operator can
visualize the data set by looking at the stack of slices or the rendered 3D image.
Computers can reformat the 3D image, allowing the operator to scroll through these 2D
images in any direction. The most common ones are sagittal, coronal, and axial. The
data set can also be rotated, panned, or zoomed to allow visualization of the region of
interest; at any angle, scale, or position, a rendered image can be created. Multiple
threshold filters can be applied to the same image to distinguish between tissues of
different density. Transparency can also be applied to allow visualization of hard
tissues through the soft tissues. Clipping tools are also available. These allow for
isolation and visualization of specific regions. It is crucial to understand that the
rendered image is the result of a user-entered threshold value. The visual perception of
the operator defines what is bone and what is soft tissue, and many factors can affect
this: contrast of the image, noise in the image, individual visual perception and prior
knowledge of anatomy. For a qualitative assessment, these rendered images are
appropriate, but, for a quantitative assessment, they present many challenges.(Grauer
et al., 2009)

In 2D radiographs, distances and angles are measured between landmarks. These
landmarks are defined by the superimposition of the projection of different structures.
This is a property of transmission radiographs. Landmarks can defined as an inflection

19
point in a curved line, the geometric center of a structure, superimposition of projection
of different structures, the tip of a structure, or the crossing point of 2 planes. Most
landmarks cannot be visualized or are difficult to locate on a curved surface in a 3D
image. There are no clear operational definitions for specific cephalometric landmarks
in the 3 planes of space.

A second challenge is that the rendered image depends on
many factors, including contrast of the image, movement during acquisition, presence of
metal that creates noise, overall signal-to-noise ratio of the image, and the threshold
filters applied by the operator. Because of these factors, it makes sense that the
landmarks should be located in the stack of slices rather than in the 3D rendered
volume. Many studies have assessed the accuracy and reliability of measurements on
CBCT images. Those studies can be classified based on 2 criteria. The first is whether
they use radiopaque markers or structures of known geometry. This classification
yields 2 groups: when landmark location does not need anatomic operational
definitions, and when anatomic definitions are important, and another interexaminer or
intraexaminer factor (landmark location) is introduced. The second classification,
applicable to both groups, is based on where the landmarks were located. According to
this second criterion, 3 groups are established: 1) landmarks located in the stack of
slices; 2) landmarks located on a segmented surface; and 3) landmarks located on the
rendered image. Studies from group 1 report good accuracy regardless of where the
measurements were made. For most measurements, there were no statistically
significant differences compared with the gold standard (measurements with a caliper or
structures of known geometry). Some measurements had statistically significant
differences, but those were small and not clinically significant.

Studies from group 2

20
report subclinical accuracy when landmarks were located on segmentations or in the
stack of slices, but not when they were located on the rendered image.

When all
studies are considered, regardless of their classification, reliability in measurements and
landmark identification in CBCT images was reported to be good to very good.(Grauer
et al., 2009)

The segmentation process in medical imaging could be defined as the construction of
3D virtual surface models (called segmentations) to best match the volumetric data.
The image reader must distinguish between a virtual surface and a rendered image.
The importance of having a segmentation engine in the software package is twofold.
First, it allows the user to export anatomic models in a nonproprietary format. This
information can be used in research and will always be accessible regardless of
constantly changing software applications. The second advantage is the option of
loading anatomic models in a non-proprietary format into the imaging software interface.
This allows combining different modalities with the CBCT images. An example is
combining digital models obtained through laser or optical scanners with the CBCT data
and soft-tissue meshes obtained through 3D cameras. These multimodal images are
the foundation of digital dentistry, rapid prototyping, and computer- aided design and
computer-aided manufacturing applications.(Grauer et al., 2009)

Traditionally, the best and almost only way to quantitatively assess changes in
orthodontics was cephalogram superimpositions. Stable structures are used as
registration and orientation landmarks. Changes can be described relative to those

21
reference structures.

Registration can be defined as the process of combining 2 or
more images from different time points, each with its own coordinate system, into a
common coordinate system. Today, it is possible to register CBCT records acquired at
different time points and analyze changes due to treatment, growth, aging, and relapse
in 3 dimensions.(Grauer et al., 2009)

The soft-tissue paradigm has paved the road toward 3D diagnosis, treatment planning,
and computer-aided design and computer-aided manufacturing in orthodontics.
Because of the advances in both CBCT scanners and software designed to manage
CBCT data, it is possible to take advantage of CBCT information in a clinical setting.
Clinicians should be careful in 2 areas: first, most visual information gathered with these
systems has not yet been linked to a clear diagnosis classification. Further research is
needed in the interpretation of orthodontic information from CBCT data. Second, some
available tools have not been validated yet, and studies to assess accuracy and
precision are mandatory before these applications become standard.(Grauer et al.,
2009)

Virtual Modeling & 3D Printing
Techniques have been developed to represent 2D and 3D data, utilizing sophisticated
software packages, on a 2D screen. Given this visualization, one might see the
fabrication of physical models as superfluous. However, the display of a 3D volume on
a 2D screen does not provide surgeons with a complete understanding of the patient’s
anatomy. Surgeons must learn to interpret the visual information in order to reconstruct

22
mentally the 3D geometry. Recently, head-mounted displays, stereoscopic glasses,
and holograms have been employed to complement the 2D screen to provide more
realistic representations of 3D volume models. Unfortunately, there is still no physical
feel of the area of interest, like the infection area or fracture size, until an operation is
performed.(Chelule et al., 2000) There are several visualization issues that are being
addressed but not yet resolved by virtual models. Physical models are attractive to
surgeons because they offer the opportunity to hold the model in hand and view in a
natural fashion. This provides surgeons a direct, intuitive understanding of complex
anatomic details which otherwise cannot be obtained from imaging on screen. The use
of physical models also creates improved prerequisites for planning and simulation of
complex orthognathic surgery. With a physical model in hand, a surgeon is able to
practice on the model with the usual surgical tools, enabling them to rehearse different
surgical plans realistically. Such an intensive planning of surgical procedures allows the
selection of the best technical approach. Additionally, the communication between the
surgeon and the patient before a complicated surgical procedure can be clearly
improved by the use of physical models.(Petzold et al., 1999)

Data Acquisition
Contact and non-contact methods can be used for data acquisition. Only non-contact
methods are considered here. The most common techniques used in acquiring detailed
anatomical information are computerized tomography (CT), magnetic resonance
imaging (MRI), and laser digitizing. CT is a radiographic technique for producing cross-
sectional images by scanning a slice of tissue from multiple directions using a narrow

23
fan X-ray beam. CT uses radiation in the form of a highly collimated X-ray fan beam to
slice a two-dimensional image or slice plane. An X-ray tube and a detector array travel
on a circular path around the patient collecting a complete set of data over 360
◦
. The
slice data can then be displayed in a stacked configuration, providing a “3D”
presentation based on volume rendering. In many cases, the scanned data lacks
development of the surface structure necessary to define the true 3D surface because
of the lower depth resolution. Therefore, post-processing of the scanned data is
needed. The longer scanning period required for a high-resolution scan must be
weighed against increasing the patient’s exposure to radiation, scan time and cost, and
patient discomfort. Fortunately, new cone beam CT scanning technology allows faster
acquisition and smaller slice intervals compared to traditional scanners that must
translate the patient for each transverse section.(Liu et al., 2006)

Both CT and MRI offer complete coverage of volumes and a 3D evaluation and display
of the region of interest. The data captured by these two modalities comprises not only
external data but also internal data. The file size for the scanned data of a complex
model always occupies a lot of space. There is a trade-off between file size and
resolution of the scanned data. In dental application, sometimes only the external data
is needed. The data captured by a laser surface digitizer comprises only the external
data rather than both the external and internal data. By acquiring only the external data,
it will reduce the size of the image file and the processing time to convert the scanned
data to CAD data. The heart of the technology is a laser probe, which emits a diode-
based laser beam. The beam is split into a plane of laser light that comes out of the

24
probe and shines below on the surface of the object being scanned. Thus it forms a
profile on the surface of the part. The shape of the profile is then recorded by the digital
charge coupled device (CCD) and subsequently, based on the calibration and look-up
table of the laser, a Z position is determined and stored for each pixel value. This
location, along with the positions of machine axes, is used to compute the X, Y, Z
coordinates of the points along the profiles scanned. By combining these profiles, a 3D
model can be generated. Figure 1 illustrates the schematic of a laser surface digitizer.
Figure 1. Laser Surface Digitizer Schematic(Liu et al., 2006)
The primary advantage of the laser surface digitizer is that the process is non-contact
and fast, and it results in coordinate locations that lie directly on the surface of the
scanned object. The laser scanner takes only seconds to capture images of the region
of interest, and the usual file size is less than 1 megabyte. This is much better than the
time needed to capture CT/MRI data. In addition, the patient is not exposed to
radiation. The radiation effect is substantial when the patient has to go through longer

25
periods of scanning. With the use of digitized data, it is easy to generate a mimic
impression, useful to reverse engineering, in the CAD environment.(Liu et al., 2006)

3D Printing in Medicine
Several methods can be employed to fabricate a physical prototype. These methods
can be divided into two categories: subtractive and additive. They all start with a 3D
computer aided design model of the anatomical area, which usually can be derived from
X-ray CT or MRI data. The subtractive technique used is the conventional numerically
controlled (NC) machining.(Petzold et al., 1999) The advantages to the subtractive
technique include low material costs and the possibility that these models can be
worked on with surgical instruments. This method has two limitations. One limitation
results from milling machines, which have restricted motion capability. Complex
geometries are difficult to program and can result in tool collisions. This is often the
case in medical application.(Potamianos et al., 1998) The other limitation lies in the
materials used to fabricate the physical model. The materials employed should be hard,
tough, and sterilizable.(Klein et al., 1992) Additive methods are advantageous to
fabricate the physical models of anatomical details. The main advantage of the additive
technique is that medical models can be created that have undercuts, voids, and
complex internal geometries such as neurovascular canals or sinuses. They can also
be translucent and the internal geometries can be easily seen. Common 3D printing
technologies used in medicine are selective laser sintering (SLS), fused deposition
modeling (FDM), stereolithography (SLA), and inkjet based system. The materials that
can be used are fairly diverse.(Liu et al., 2006)

26

Working with 3D printing technologies in the medical field differs radically from using
them in the manufacturing environment. In manufacturing, models are usually designed
on the computer screen, then converted to physical models. In medical applications,
the object or part often exists physically. Building medical models essentially starts with
acquiring data such as computed tomography (CT) cross sectional images. Prior to part
building, this highly complex data needs to be pre-processed to provide a format that a
CAD package or a 3D printing system can recognize. It can be seen that data scanning
and processing technologies must be linked with 3D printing technologies to obtain the
desired physical models. The data has to undergo a number of processes: data
acquisition, image processing and model fabrication.(Liu et al., 2006)

After data acquisition, the data must be processed to construct 3D images. The output
of data processing must be converted into the following formats. In the first, the
scanned data can be directly converted to a .STL file and input into a 3D printing
system. In the second, the scanned data can be converted to a format that a CAD
package can read for further design and then output to a 3D printing system to fabricate
the structure of interest. Many CAD packages available in the market can perform the
editing job (ex. Solidworks).(Chee Kai et al., 2000)

Rapid prototyping(RP), also called layered manufacturing or solid freeform
fabrication(SFF), is becoming more attractive in dental applications because a dental
model is very difficult to fabricate using the conventional subtracting method because of

27
its complexity. The basic concept of rapid prototyping is discretization and sequential
stacking as shown in Figure 2.
Figure 2. Principle of Rapid Prototyping(Liu et al., 2006)
By discretization, a complex 3D building problem can be changed into a simpler 2D
layer-building problem without part complexity limitation. By sequential stacking,
building material is precisely deposited in a pre-determined order to form the desired 3D
dental model. If a model has features like an overhang or undercut, then support layers
are needed to support the build material. This keeps the model from collapsing. For
certain RP systems, no separate support material is needed because the build material
itself can also be the support material. All rapid prototyping processes start from a 3D
CAD model, which can be derived from other CAD packages or scanned data. The
model is sliced into multiple layers along one direction (usually Z direction) with a pre-
determined layer thickness. This information is then sent to the rapid prototyping
system that controls the laser or nozzle to fabricate each layer of the physical model.
Currently, popular RP systems include stereolithography (SLA), selective laser sintering
(SLS), fused deposition modeling (FDM), laminated object manufacturing (LOM), three-
dimensional printing (3DP), and laser engineered net shaping (LENS).(Kai, 1994;

28
Webb, 2000)

SLA builds plastic parts or objects one layer at a time by tracing a laser beam on the
surface of a vat of liquid photopolymer as described in Figure 3.
Figure 3. Schematic of SLA(Liu et al., 2006)
When the UV light strikes the surface of liquid polymer, it solidifies one layer of polymer.
Once the first layer, which adheres to the platform, has been completely traced, the
elevator is lowered to the depth of the next layer. This process continues layer by layer
until the part fabrication is completed. The self-adhesive property of the material causes
the layers to bond to one another and eventually form a complete, 3D object. For some
objects having overhangs or under- cuts, they must be supported during the fabrication
process by support structures. Upon completion of the fabrication process, the object is
elevated from the vat and the supports are cut off. Some other post-processing steps
include cleaning and post cure. SLA can also produce surgical templates out of
sterilizable USP Class VI resin. Advantages of SLA process include high part-building
accuracy, smooth surface finish, fine building details, high mechanical strength, etc.

29
Disadvantages of this process include expensive equipment and material cost, wet
material handling, and post-processing.(Cooper, 2001; Hilton, 2000; Jacobs, 1992)

An RP model is of little value to dental application unless it simplifies and helps an
otherwise complicated procedure, reduces the risk to the patient owing to the accurate
surgical planning and the shortened operating time, and is less expensive than the
alternatives.(Robertson and Rhodes, 1996) This derives that the following should be
achieved when using RP models in dentistry(Kai et al., 1998):
1. Efficient surgery with reduced cost and operating room time resulted from clear
visualization and pre-surgical planning.
2. Improved patient outcome, such as fewer complications and faster
rehabilitation.
3. Increased surgical precision to reduce possible damage to healthy tissue.
4. Possibility of performing new, or previously impossible, minimally invasive
procedures.
5. Better communication between the surgeon and the patient.
6. Better communication between the surgeon and referring doctor.
7. Predictable surgical results.
All the RP systems introduced above can find a position in dental application. SLA can
achieve relatively high accuracy and a good surface finish. A suitable RP machine
needs to be chosen to satisfy various requirements based on application purpose, time
constraint, cost, materials availability, accuracy, surface finish, and so on. In surgical
planning, it would be beneficial if we could use different colors to highlight critical

30
structures within a single RP model and consequently enhance the visualization of the
complex model. SLA can be used for this purpose because it has the capability to
deposit materials with different colors.(Williams et al., 1996)

Virtual Surgical Planning
The complex anatomy of the skull and face requires extensive pre-surgical planning and
this in turn creates a plan that is reproducible in the operating room.(Aboul-Hosn
Centenero and Hernández-Alfaro, 2012; Xia et al., 2006) A new method of carrying out
this planning procedure is through virtual surgical planning (VSP) or computer aided
surgical simulation (CASS). The creation of a CAD/CAM surgical splint allows the
surgeon to plan surgery without the use of a traditional plaster surgery.(Aboul-Hosn
Centenero and Hernández-Alfaro, 2012) Surgeons can now perform virtual surgery and
view the patient outcomes as if they are actually in the operating room. This also
reduces the extensive amount of time needed for surgery planning and decreases the
manual labor involved.(Xia et al., 2006) VSP can also reduce the time of the actual
surgery.(Nadjmi et al., 2010) The digital storage of the patient data allows for easy
categorization and management. This makes retrieval a much simpler task when
recalling records. This preoperative and post-operative information can be shared with
colleagues throughout the world by utilizing the internet.(Aboul-Hosn Centenero and
Hernández-Alfaro, 2012) It has also been found that the post surgical outcomes appear
to be better than with conventional methods.(Xia et al., 2006) The high degree of
similarity found between both types of surgical splints leads to the conclusion that the

31
CAD/CAM method of splint manufacturing is a valid and reliable technique for designing
surgical splints.(Aboul-Hosn Centenero and Hernández-Alfaro, 2012)

Plaster model surgery has long been the gold standard for orthognathic surgery
planning. This involves the duplicating of a patient’s dentition in plaster and then
subsequent prediction osteotomies are completed on the models and transferred to an
articulator for completion of the model surgery. Plaster surgery is now being eliminated
and 3D simulation is taking its place.(Xia et al., 2006) The greatest downside of a
traditional plaster model surgery is that only the patient’s teeth are represented in 3D in
those models. The patient’s boney structures are not represented in these models.
The surgeon is not able to preview the modifying and mobilizing of tissues that takes
place during surgery.(Xia et al., 2006)

VSP preparation procedures can be carried out by a trained technician, therefore
freeing up valuable surgeon time. The diagnosis can also be shared with the patient
using a 3D image that can be easily explained and interpreted.(Aboul-Hosn Centenero
and Hernández-Alfaro, 2012) The preparation includes 3D model creation, landmark
digitization, and the creation of multiple routine virtual osteotomies on the computer
model. This procedure can be carried out at a central location and then the surgeon
can control the final steps of the process remotely via a secure internet connection.(Xia
et al., 2006) By utilizing telemedicine, other specialists can join in on treatment planning
for extended expertise when needed.(Aboul-Hosn Centenero and Hernández-Alfaro,
2012)

32

There’s no substitute for practicing on a reasonably precise model to educate the novice
surgeons or students and determine the course of progress of a complicated operation.
RP models are being used by surgeons to plan and explain complex operations.
Currently, RP models are frequently present in the operating room where they are used
as templates and guides. Real surgical tools can be applied on these models. This
greatly reduces the time in the operating room and after-surgery complications. RP
models can be used not only to practice surgeries, but also to aid in decision making.
With the RP model at hand, surgeons and their teams will be able to see the actual
location, size, and shape of the problem area. In the case of an extremely long and
complex operation, the surgical team can use the physical model to plan the surgery so
that the desired outcome is more ensured. Furthermore, surgeons can view the
expected outcome and can make decisions for the patient’s short- and long-term
treatment. SLA models are often chosen for such applications. The transparency of the
model and the recent development of color resins allow distinct visualization of
anatomical structure.(Combs, 2006)

One of the key goals of pre-surgical planning is to achieve a stable and optimized dental
occlusion. Without good dental occlusion, the intermediate and final position of the
maxilla relative to the mandible cannot be achieved. To achieve this, the surgeon
manually searches for a stable occlusion by hand articulating the stone models.
Although this is currently the gold standard, hand articulating models and mounting in a
semi-adjustable articulator does not allow the surgeon to see how the hard and soft

33
tissues will react to the surgery. This shows that there is a need to make the manual
procedure virtual. A virtual manner of determining good occlusion has been created. It
allows for the reliable determination of the desired occlusion and performs this by using
a rigid motion simulation engine to ensure there is an impenetrability of the virtual
models. If there is a premature interference, there is also a virtual grinding module that
may be used to reduce the interference. This virtual grinding must be replicated during
the surgery in order for the CAD/CAM surgical splint to fit correctly. One downside of
the virtual occlusion planning is the learning curve that accompanies the
software.(Nadjmi et al., 2010)

Prior to the introduction of box scanners and intraoral scanners, a major drawback of
VSP was the accuracy of the dental occlusion. This was caused by the manner in
which the dental occlusion was obtained. The stone models were created and then
placed in a CBCT for a double scanning procedure. The resultant 3D file would then be
superimposed on the actual CBCT scan of the patient’s boney structure. The double
CBCT scan’s resolution is hindered by streak artifacts caused by radio-opaque dental
restorations or orthodontic brackets. This lack of resolution would only be compounded
when determining the virtual dental occlusion.(Swennen et al., 2007) The new manner
of superimposing the dental occlusion onto the CBCT for virtual surgery includes the
use of an intraoral scanner to collect the patient’s occlusion. This method also
decreases the overall amount of radiation that the patient is exposed to.(Swennen et al.,
2007)

34
The ability to predict postoperative results is required not only because of the greater
accuracy from the VSP, but also because of the large number of patients undergoing
surgery for aesthetic reasons. There main ways that traditional plaster model surgery
can lead to errors are transferring of the models to the articulator, drawing the vertical
and horizontal reference lines on the models, and the lack of boney structures when
performing the osteotomies on the models. Articulators also maintain the same center
of rotation for the simulated condyle all patients on a semi-adjustable articulator. By
utilizing a VSP, the condyle-fossa relationship remains stable. VSP is completed using
3D images that can be manipulated, while traditional planning uses 2D images from
multiple sources that must be combined.(Aboul-Hosn Centenero and Hernández-Alfaro,
2012)

One of the greatest limitations of 3D splint fabrication and virtual surgical planning is
time and cost.(Mavili et al., 2007) Using current technology and planning procedures,
this is no longer the case. Xia et al found that not only is computer aided surgical
simulation (CASS) less money when compared to traditional planning methods for
complex cranio-maxillofacial surgery, $1900 versus $3510 respectively, but the total
surgeon hours spent planning are 5.25 hours for CASS and 9.75 hours for traditional
methods. Amortized across the year, this adds only a few dollars and a fraction of an
hour per surgery. Even in the case of a small clinic when the cost is amortized for 6
patients per year, the per surgery costs will still favor the CASS method.(Xia et al.,
2006)

35
Chapter 2: Materials and Methods
1. Decompensation in preparation for orthognathic surgery is carried out.
1.1. This can be done through traditional braces, Clear Aligner Therapy, etc.
2. When the tooth movement achieved allows for jaw relationship correction, a new
set of records is obtained (photos & models).
2.1. Desired post surgery interocclusal relationship is assessed by positioning
the models into the corrected position.
2.1.1. Transverse
2.1.2. A-P
2.1.3. Vertical
2.1.4. Individual Tooth Positions are assessed
3. Plaster or 3D models are taken to check surgical occlusion.
4. Immediately prior to surgical workup, braces are removed if present.
Attachments are removed, if present, from Clear Aligner Therapy, so that all
surfaces are smooth.
4.1. (Attachments that remain from Clear Aligner Therapy or aligner treatment
can cause increased retention when removing the splint during surgery
and this can dislodge plated osteotomies.)
5. Permanent retainers are bonded to maintain alignment during the initial healing
stage to prevent relapse.
5.1. A Lower bonded 3-3 lingual retainer and a maxillary bonded lingual
retainer using 0.0195 twisted wire are placed.

36
5.1.1. The maxillary bonded retainer should be placed mesial to the
osteotomy cuts in case of segmented maxilla surgery, and as close
vertically as possible to the incisors’ cingulum.
6. Splint Creation/Design
6.1. Method 1 (Recommended)
6.1.1. The patient’s dentition is scanned with an intraoral 3D scanner
(Figure 4).

Figure 4. Intra-Oral Scanning of Dentition
6.1.2. Dental arches are segmented at the pre-determined osteotomy
sites.
6.1.3. The newly segmented arches are repositioned by moving the jaws
into a post-surgical orientation with the correct spatial position, tip,
torque, and rotation of each one of the segments according to the
desired final occlusion. These will be called virtually repositioned
models (VRM).

37
6.1.4. The arches will then be placed so that the desired occlusion is
present.
6.1.4.1. Equilibration of premature contacts should be completed in
the software.
6.1.4.2. This equilibration should be noted so that it may be
reproduced during the orthognathic surgery procedure.
6.1.4.2.1. (Ideally, a surgical feasibility study is done and
equilibration is done prior to taking the surgical
impressions. This eliminates the need for
intraoperative equilibration.)
6.1.5. Three surfaces are then exported into the CAM (Computer Aided
Manufacturing) Software:
6.1.5.1. Virtually repositioned models (VRM) (Upper Arch + Lower
Arch)
6.1.5.2. Upper Arch only
6.1.5.3. Lower Arch only
6.2. Method 2
6.2.1. Alginate impressions are taken and poured immediately in stone.
6.2.2. Model surgery is performed using pre-determined osteotomy sites.
6.2.3. The newly segmented arches are repositioned to a post-surgical
orientation with the correct spatial positioning, tip, torque, and
rotation.

38
6.2.4. The arches will then be placed so that the desired occlusion is
present.
6.2.4.1. Equilibration should be completed in the software.
6.2.4.2. This equilibration should be noted so that it may be
reproduced during the orthognathic surgery procedure.
6.2.4.2.1. (Ideally, a surgical feasibility study is done and
equilibration is done prior to taking the surgical
impressions. This eliminates the need for
intraoperative equilibration.)
6.2.5. Using inter-occlusal bite registration PVS (Ex. Blue Mousse©), a
bite registration is recorded in the post-surgical bite orientation.
6.2.6. The upper arch (Figure 5), lower arch(Figure 6), and bite
registration(Figure 7) are 3D scanned separately.

Figure 5. Box Laser Scanning of Maxillary Arch

39

Figure 6. Box Laser Scanning of Mandibular Arch

Figure 7. Box Laser Scanning of Bite Registration

40
6.2.7. Using CAD software, a registration process is performed in order to
match the occlusal position of the pre-surgical models(Figure 8).

Figure 8. Box Laser Scanning of Maxillary Arch
6.2.8. Three surfaces are then exported into the CAM (Computer Aided
Manufacturing) Software (Ex. Preform©):
6.2.8.1. Post-model surgery aligned arches (Upper Arch + Lower
Arch) (Figure 9)

Figure 9. Post Model Surgery Aligned Arches

41
6.2.8.2. Maxillary Arch only(Figure 10)

Figure 10. Post Model Surgery Maxillary Arch
6.2.8.3. Mandibular Arch only(Figure 11)

Figure 11. Post Model Surgery Mandibular Arch
7. A virtual surgical planning session is then conducted by the oral surgeon in order
to position the jaws in the desired position relative to the patient’s cranium, face,
and soft tissue. Here, the desired skeletal corrections are made and surgical
guides are generated using CAD/CAM technology.
The
digital
models
are
registered
into
the
same
coordinate
system
of
the
patient’s

segmented
skull.

This
is
based
on
the
unaltered
position
of
the
maxilla.

The
desired

interocclusal
position
will
be
dragged
along
with
the
changes
in
position
of
the
maxilla

relative
to
the
patient’s
skull.

7.1. The intermediate splint is generated relating the position of the unaltered
jaw position to the corrected position of the mandible/maxilla depending
on which is the first jaw to be repositioned.

42
7.2. The intermediate splint is designed so that it:
7.2.1. Has complete coverage of the labial/lingual surface
7.2.2. Is festooned along the gingival margins
7.2.3. Allows for adequate occlusal clearance
7.3. The final splint is designed so that it:
7.3.1. Has complete coverage of the labial/lingual surface
7.3.2. Is festooned along the gingival margins
7.3.3. Allows for maxillary and mandibular occlusal contacts
8. The merged mid-surgical arches are exported in their corrected position (Upper
Arch + Lower Arch).
9. The merged final arches are exported in their corrected position (Upper Arch +
Lower Arch).
10. Splint design process: The following procedure is performed for both the mid-
surgical aligned arches and the final aligned arches:
10.1. Using a CAD program, a large, all-encompassing shape is merged with
the aligned arches and the arches are then subtracted from the shape.
10.2. The newly created negative of the maxillary and mandibular arches is then
shelled from the buccal face to a width of 1-2mm and from the lingual face
by 0.01mm. (These widths can be varied as desired by the oral surgeon)
This results in a 3D object with occlusal holes that allows for contact
between the upper and lower arches when fit to the patient’s occlusion.
10.2.1. This creates a rigid splint to be used during the surgery and allows
for the easy removal of the splint when needed.

43
10.2.1.1. The splint itself does not need to be completely rigid
because of its fit between the maxillary and mandibular
arches. This makes the lower arch and consequently the
mandible an extension of the fabricated splint.
11. The newly generated splint files are then 3D printed using a biocompatible
material that is suitable for operative use. (Figures 12 & 13)

Figure 12. Finished 3D Printed Biocompatible Splint (Occlusal View)

Figure 13. Finished 3D Printed Biocompatible Splint (Labial View)
12. Orthognathic surgery is completed.

44
12.1. The surgical guides are used to orient both the intermediate and final
occlusion.
12.2. When segmental maxillary surgery is planned, the definitive surgical guide
is indexed with the lower dental arch, and then the maxillary segments are
brought into the upper portion of the surgical guide.
12.3. The transparent quality of the guide ensures that the occlusion is precisely
oriented. Proper orientation of the maxillary segments is also ensured
because of the intimate fit that the guide makes with all surfaces of the
teeth (similar to how a clear orthodontic aligner embraces the complete
surface area of the teeth). Maxillomandibular fixation is applied by means
of skeletal anchor screws placed at the start of surgery. This eliminates
the possibility of extruding teeth, which will relapse after the
maxillomandibular fixation is released. Secure rigid fixation of the
osteotomies is imperative, so that very early jaw mobilization is
permissible. This will permit sufficient jaw motion within a few weeks of
surgery so that aligner trays may be placed.

13. Post-surgery Protocol
13.1. If alignment on the anterior teeth is ideal, then the bonded retainers may
remain as long term retention.
13.1.1. If alignment requires modification, bonded retainers are to be
carefully removed before insertion of the first aligner tray.

45
13.2. The orthodontist is able to fabricate the needed aligner trays to finish
orthodontic treatment prior to the patient returning from surgery using
Clear Aligner Therapy.
13.3. When patient is first seen by the orthodontist post surgery, approximately
2-3 weeks after surgery is completed, the first set of aligner trays will be
delivered.
13.4. Aligner trays could be switched on a 5-7 day basis for the first 3 weeks
and then moved to regular 2 week intervals until finished.
13.4.1. The Rapid Acceleratory Phenomenon (RAP) present from the
orthognathic surgery is taken advantage of by switching at the 5-7
day interval.

46
Chapter 3: Discussion
The greatest achievements in science over the next five years have already been
discovered; the lines of technology just haven’t been connected in the right order or
applied to the correct fields. Medicine is finally starting to catch up with the world of
engineering by utilizing tools that have been around for over three decades. This
includes CAD/CAM technology and 3D printing. The current golden standard for
orthognathic surgical planning is still utilizing a plaster model for model surgery and then
hand fabricating an acrylic splint. Only the most forward thinking surgeons are utilizing
the cutting edge technology of virtual surgical planning and taking CBCT scans of their
stone models to have an orthognathic surgical splint wafer printed. This paper has
discussed the inherent flaws with both the golden standard and cutting edge methods of
splint fabrication. These documented flaws are the reasoning for which the novel full
coverage splint method was created. It is also the goal of this method to maintain the
comfort level of practicing orthodontists and oral surgeons by utilizing and modifying
existing methods already in place in orthodontics and orthognathic surgery today.

The preparation and decompensation prior to surgery can be carried out by the doctor’s
preferred orthodontic method. It has been shown that clear aligner therapy is an
effective form of treatment when used prior to orthognathic surgery.(Boyd, 2008) It is
also well documented that traditional braces are the current method of choice for
preparing a patient for orthognathic surgery. When the tooth movement achieved
allows for jaw relationship correction, a new set of records is obtained. This can be
completed by traditional alginate impressions followed by pouring of plaster models or

47
by intraoral scanning of the dentition. Intraoral scanning of the dentition has been
shown to be more accurate because of the inherent flaws of plaster and alginate
materials.(Santoro et al., 2003)

Immediately prior to the surgical workup, braces are removed (if present) or all bonded
attachments are removed from clear aligner therapy so that all tooth surfaces are
smooth. The reasoning behind the removal is two fold: 1) The new full coverage splint
no longer needs the increased anchorage of the bonded braces or attachments
because the fabricated rigid splint utilizes the occlusal contacts and consequently the
mandibular occlusion as its anchor. 2) It has been found that patients have an
increased amount of comfort when using clear aligner therapy in orthodontics.(Djeu et
al., 2005; Joffe, 2014; Melkos, 2005) This is paramount when recovering from an
already uncomfortable orthognathic surgery. By increasing patient comfort, the surgeon
and orthodontist can increase patient acceptance pre-surgery and compliance post-
surgery. (In model surgery trials, it was found that leaving clear aligner therapy
attachments on the teeth would cause increased retention with the new full coverage
splint during removal and this could increase the chances of dislodging plated
osteotomies. Therefore, all clear aligner therapy attachments should be removed prior
to surgery.)

It has been surmised that rapid acceleratory phenomenon (RAP), caused by an
increase in cortical bone porosity because of increased osteoclastic activity and
inflammation, may be responsible for an increase in tooth mobility post surgery.(Liou et

48
al., 2011; Pfeifer, 1965) To decrease this effect, semi-permanent retainers are bonded
to the lingual surface of the maxillary and mandibular anterior teeth using an 0.0195”
twisted wire. The lower anteriors are bonded lingually 3-3 and the maxillary bonded
retainer should be placed lingually mesial to the osteotomy cuts in case of a segmented
maxilla surgery, and as close vertically as possible to the incisor’s cingulum so the
patient will not bite it off post surgery. If a segmented maxilla is not being performed,
then bond the maxillary anteriors lingually 3-3.

After the semi-permanent lingual retainers have been placed, there are two methods
that can be completed to retrieve the patient’s pre-surgical occlusion. The first method
is recommended because it is a completely digital process and studies have shown this
to be more accurate when plaster models are not involved.(Mavili et al., 2007) The
patient’s dentition is scanned using an intraoral scanner and the resulting STL file is
exported. The digital arches are then segmented at the pre-determined osteotomy
sites. The newly segmented arches are repositioned by moving the jaws into a post-
surgical orientation with the correct spatial position, tip, torque, and rotation of each one
of the segments according to the desired final occlusion. These will be called virtually
repositioned models (VRM). These new arches are then placed in the desired post
surgical occlusion and any premature contacts are noted so that they may be
equilibrated prior to the orthognathic surgery. The three resulting surfaces that are
created are then exported into the desired CAM (Computer Aided Manufacturing)
software. These STL surfaces include: 1) The VRM, which is the upper and lower

49
arches articulated in the desired post surgical occlusion as a single file. 2) The VRM
upper arch by itself. 3) The VRM lower arch by itself.

The second method differs from the first by utilizing alginate impression material to
capture the pre-surgical dental arches and then completing the model surgery on the
plaster models. The desired post-surgical occlusion is set and recorded using an inter-
occlusal bite registration. The maxillary and mandibular plaster models and bite
registration are then scanned separately using a 3D scanner. Using a CAD (Computer
Aided Design) software, a registration process is performed in order to match the pre-
surgical models with the scanned bite registration. The same three STL surfaces are
then exported as used in the first method.

A virtual surgical planning session is then conducted by the oral surgeon in order to
position the jaws in the desired position relative to the patient’s cranium, face, and soft
tissue. Here, the desired skeletal corrections are made and surgical guides are
generated using CAD/CAM technology.(Aboul-Hosn Centenero and Hernández-Alfaro,
2012; Gateno et al., 2003; Macchi et al., 2006; McCormick and Drew, 2011; Xia et al.,
2005)

Following the completion of a virtual surgical plan, the intermediate and final, full-
coverage orthognathic surgical splints are designed. Using a CAD program, a large, all-
encompassing shape is merged with the aligned arches and the arches are then
subtracted from the shape. The newly created negative of the maxillary and mandibular

50
arches is then shelled from the buccal face to a width of 1-2mm and from the lingual
face by 0.01mm. (These widths can be varied as desired by the oral surgeon) This
results in a 3D object with occlusal holes that allows for contact between the upper and
lower arches when fit to the patient’s occlusion. This occlusal contact operates on two
levels: 1) This allows for the preset final occlusion to actually exist post surgery because
the teeth do not have acrylic or 3D printed resin where occlusal contacts should exist. 2)
The resulting mandibular extension of the semi-rigid full coverage splint increases the
rigidity of the splint structure by basing its strength off of the mandibular alveolus and
attached mandible. The newly generated splint files are then 3D printed using a
biocompatible material that is suitable for operative use.

Orthognathic surgery is then completed in a typical manner with only minor changes to
arch stabilization post-surgery. The surgical guides are used to orient both the
intermediate and final occlusion. When segmental maxillary surgery is planned, the
definitive surgical guide is indexed with the lower dental arch, and then the maxillary
segments are brought into the upper portion of the surgical guide. The transparent
quality of the guide ensures that the occlusion is precisely oriented. Proper orientation
of the maxillary segments is also ensured because of the intimate fit that the guide
makes with all surfaces of the teeth (similar to how a clear orthodontic aligner embraces
the complete surface area of the teeth). The intimate fit of the splint is paramount to the
finishing process for the orthodontist. The orthodontist is guaranteed that the post-
surgical occlusion will be returned exactly as the orthodontist setup in the VRM exports.
This allows for the pre-fabrication of the finishing clear aligner therapy trays.

51
Maxillomandibular fixation is applied by means of skeletal anchor screws placed at the
start of surgery. This eliminates the possibility of extruding teeth, which will relapse
after the maxillomandibular fixation is released. Secure rigid fixation of the osteotomies
is imperative, so that very early jaw mobilization is permissible. This will permit
sufficient jaw motion within a 2-3 weeks of surgery so that aligner trays may be placed.

After 2-3 weeks post surgery, post-surgery orthodontic protocol may begin. If alignment
on the anterior teeth is ideal, then the bonded retainers may remain as long-term
retention. If alignment requires modification, bonded retainers are to be carefully
removed before insertion of the first aligner tray. The orthodontist will have
predetermined this and all finishing trays will be ready to be delivered when needed
post-surgery. This accelerates the usual waiting time of post surgical follow-up and
increases the patient’s post surgery comfort by not having a fixed appliance (standard
edgewise braces) present in the mouth.

Advantages
The advantages to using this novel full coverage orthognathic surgical splint are far
reaching and do not require an overly differentiated method from existing virtual surgical
planning using a 3D printed wafer style splint. The advantages of using a full-coverage
3D printed splint are covered in three categories: 1) Increased accuracy of post-surgical
occlusion. 2) Increase in patient comfort and acceptance of treatment. 3) Accelerated
speed in post surgical orthodontic finishing.

52
Increased accuracy of post-surgical occlusion is derived from the full-coverage splint
allowing for the orthodontist to pre-determine where the torque of the maxillary teeth will
be positioned as seen in figure 14.
Figure 14. Lateral View of Anterior Segment Torque
Prior to the full-coverage splint technology, this was not possible with traditional acrylic
splints because of the non-flexible undercuts forming during fabrication nor with the new
3D printed wafer splints because of the lack of buccal and lingual coverage of the
dentition. The open occlusal contacts in the full-coverage splint allow for the setting of
the actual desired occlusion set by the orthodontist and/or surgeon. This could only be
estimated on an articulator in the past because there needed to be acrylic or resin
present to make the splint rigid enough for surgical use.

There is also an increase in patient comfort and acceptance of treatment by removing
the patient’s braces or attachments prior to surgery. The patient will have an increased
comfort level immediately post surgery and in the finishing stages of orthodontic
treatment when utilizing clear aligner therapy for treatment. Also, when presenting a
treatment plan to a patient, letting the patient know that there will be no more braces

53
post surgery is much more appealing to a patient than finishing with the uncomfortable
and unaesthetic presence of braces and this may lead to an increase in initial patient
acceptance and surgical follow through.

Finally, using a full-coverage surgical splint may accelerate the speed of post surgical
orthodontic finishing. By creating a splint that only allows the surgeon to place the
dental arches in one very accurate orientation, the orthodontist is able to create the
finishing trays needed post surgery without having to take a post-surgical impression or
scan. Also, because of the clear aligner tray’s low profile, they can be delivered much
more quickly post surgery. This allows post surgical orthodontic treatment to begin
much quicker than when using traditional braces or clear aligner therapy with traditional
surgical planning and splints.

Disadvantages
The disadvantages to the new full-coverage splint design are typical to those that follow
a new technology in any industry: 1) Orthodontist and oral surgeon comfort with the
procedure. 2) The initial cost of the technology. Virtual surgical planning is still very new
to orthognathic surgery and oral surgeons alike. This new methodology not only takes
VSP to the next level by adding a new virtually planned dentition, but also all fixed
appliances are to be removed prior to orthognathic surgery. This will force the
orthodontist to create a much more accurate pre-surgical occlusion so that the virtually
planned dentition can be completed as desired. Orthodontists are very traditional

54
thinkers, and though they are faster movers than other branches of the dental
community, such a drastic jump forward will be difficult to grasp until fully understood.

Though the cost of intraoral scanners and/or desktop box scanners is beginning to fall in
price, they are still not to the price point where acquisition by every orthodontic and oral
surgery practice is practical. Only the most modern and forward thinking practices have
adopted this technology. More orthodontists are seeing the value of intraoral scanning
technology both from a marketing stand point and materials cost stand point, but as a
profession, orthodontics still has a long way to go before scanners are considered a
standard of care. 3D printers are becoming more and more common in dental labs
around the world and companies that can provide accurate 3D printed models are
widely available. The cost of these 3D printed models is still very high and the
acquisition costs of personal 3D printers and the required materials to create a
biocompatible splint are out of reach for the typical practicing orthodontist and oral
surgeon. Improvements are being made rapidly in cost of materials and printing
hardware and should soon be attainable by a much wider dental practitioner audience.

Improvements to Be Made
Technology is continually evolving. If it is not the hardware itself, then it is the process
to create the hardware. The process to create the full-coverage orthognathic surgery
splint is the area in which improvement needs to be made. There are too many
expensive and detailed processes that take place in the creation of the splint to allow for
easy adoption by the non-tech savvy doctor. By creating an easy to use surgery setup

55
module, an orthodontist and oral surgeon would have the opportunity to collaborate
digitally on setting up the patient’s future dentition. The orthodontist would be able to
scan the patient’s dentition and submit it through an online portal along with all other
pertinent patient details, including a CBCT and intraoral/extra-oral photos. The software
would allow the orthodontist to set up the post-surgical occlusion, suggest the required
osteotomies, and check to make sure all pre-surgical modifications needed have been
finished. The oral surgeon could then corroborate the orthodontist’s predictions and
from this portal both the full-coverage orthognathic splint and post-surgical clear aligner
therapy trays could be manufactured. This would cut down on the cost of
communication between the orthodontist and oral surgeon because of the reduction of
materials being sent back and forth as well as the decreased amount of doctor time
spent on communicating one on one about the patient’s case details. This centralized
hub concept will allow orthodontists and oral surgeons to interface and collaborate like
they never have before.

56
Chapter 4: Conclusion
This project’s goal was to increase the communication between both the orthodontist
and oral surgeon and therefore create a better patient outcome using digital treatment
planning and 3D printing technology. By creating a more accurate and full-coverage
splint, the following was achieved: 1) Operating room time is decreased. 2) Patient
outcomes, including fewer complications and faster rehabilitation, have been improved.
3) Increased surgical precision. 4) Increased communication between the doctor and
patient, including better surgical predictions. 5) Better communication between the
surgeon and referring orthodontist. 6) Highly predictable surgical results. The continued
increase in adoption of this splint technology and methodology will allow an increased
number of orthognathic surgery patients to enjoy a beautiful result from their
orthognathic surgery experience.

57
References

Aboul-Hosn Centenero, S., and Hernández-Alfaro, F. (2012). 3D planning in
orthognathic surgery: CAD/CAM surgical splints and prediction of the soft and hard
tissues results – Our experience in 16 cases. Journal of Cranio-Maxillofacial Surgery
40, 162-168.
Anwar, M., and Harris, M. (1990). Model surgery for orthognathic planning. British
Journal of Oral and Maxillofacial Surgery 28, 393-397.
Boyd, R.L. (2008). Esthetic Orthodontic Treatment Using the Invisalign Appliance for
Moderate to Complex Malocclusions. Journal of Dental Education 72, 948-967.
Chee Kai, C., Siaw Meng, C., Sin Ching, L., Seng Teik, L., and Chit Aung, S. (2000).
Facial prosthetic model fabrication using rapid prototyping tools. Integrated
Manufacturing Systems 11, 42-53.
Chelule, K., Coole, T., and Cheshire, D. (2000). Fabrication of medical models from
scan data via rapid prototyping techniques. Paper presented at: Proceedings of the
2000 Conference on Time Compression Technologies.
Combs, C.D. (2006). Startling technologies promise to transform medicine. BMJ : British
Medical Journal 333, 1308-1311.
Cooper, K. (2001). Rapid prototyping technology: selection and application (CRC
press).
Djeu, G., Shelton, C., and Maganzini, A. (2005). Outcome assessment of Invisalign and
traditional orthodontic treatment compared with the American Board of Orthodontics
objective grading system. American Journal of Orthodontics and Dentofacial
Orthopedics 128, 292-298.
Ellis, E., Tharanon, W., and Gambrell, K. (1992). Accuracy of face-bow transfer: effect
on surgical prediction and postsurgical result. Journal of oral and maxillofacial surgery
50, 562-567.

58
Gateno, J., Forrest, K.K., and Camp, B. (2001). A comparison of 3 methods of face-bow
transfer recording: implications for orthognathic surgery. Journal of Oral and
Maxillofacial Surgery 59, 635-640.
Gateno, J., Teichgraeber, J.F., and Xia, J. (2003). Method and apparatus for fabricating
orthognathic surgical splints (Google Patents).
Gateno, J., Xia, J.J., Teichgraeber, J.F., Christensen, A.M., Lemoine, J.J., Liebschner,
M.A.K., Gliddon, M.J., and Briggs, M.E. (2007). Clinical Feasibility of Computer-Aided
Surgical Simulation (CASS) in the Treatment of Complex Cranio-Maxillofacial
Deformities. Journal of Oral and Maxillofacial Surgery 65, 728-734.
Grauer, D., Cevidanes, L.S., and Proffit, W.R. (2009). Working with DICOM craniofacial
images. American Journal of Orthodontics and Dentofacial Orthopedics 136, 460-470.
Hilton, P. (2000). Rapid tooling: technologies and industrial applications (CRC Press).
Jacobs, P.F. (1992). Rapid prototyping & manufacturing: fundamentals of
stereolithography (Society of Manufacturing Engineers).
Joffe, L. (2014). Invisalign®: early experiences.
Kai, C.C. (1994). Three-dimensional rapid prototyping technologies and key
development areas. Computing & Control Engineering Journal 5, 200-206.
Kai, C.C., Meng, C.S., Ching, L.S., Hoe, E.K., and Fah, L.K. (1998). Rapid prototyping
assisted surgery planning. Int J Adv Manuf Technol 14, 624-630.
Klein, H., Schneider, W., Alzen, G., Voy, E., and Günther, R. (1992). Pediatric
craniofacial surgery: comparison of milling and stereolithography for 3D model
manufacturing. Pediatric radiology 22, 458-460.
Liou, E.J.W., Chen, P.-H., Wang, Y.-C., Yu, C.-C., Huang, C.S., and Chen, Y.-R.
(2011). Surgery-First Accelerated Orthognathic Surgery: Postoperative Rapid
Orthodontic Tooth Movement. Journal of Oral and Maxillofacial Surgery 69, 781-785.

59
Liu, Q., Leu, M.C., and Schmitt, S.M. (2006). Rapid prototyping in dentistry: technology
and application. Int J Adv Manuf Technol 29, 317-335.
Macchi, A., Carrafiello, G., Cacciafesta, V., and Norcini, A. (2006). Three-dimensional
digital modeling and setup. American journal of orthodontics and dentofacial
orthopedics 129, 605-610.
Mavili, M.E., Canter, H.I., Saglam-Aydinatay, B., Kamaci, S., and Kocadereli, I. (2007).
Use of Three-Dimensional Medical Modeling Methods for Precise Planning of
Orthognathic Surgery. Journal of Craniofacial Surgery 18.
McCormick, S.U., and Drew, S.J. (2011). Virtual model surgery for efficient planning and
surgical performance. Journal of Oral and Maxillofacial Surgery 69, 638-644.
Melkos, A.B. (2005). Advances in digital technology and orthodontics: a reference to the
Invisalign method. Medical Science Review 11, PI39-PI42.
Nadjmi, N., Mollemans, W., Daelemans, A., Van Hemelen, G., Schutyser, F., and
Bergé, S. (2010). Virtual occlusion in planning orthognathic surgical procedures.
International Journal of Oral and Maxillofacial Surgery 39, 457-462.
Olszewski, R., and Reychler, H. (2004). [Limitations of orthognathic model surgery:
theoretical and practical implications]. Revue de stomatologie et de chirurgie maxillo-
faciale 105, 165-169.
Petzold, R., Zeilhofer, H.-F., and Kalender, W. (1999). Rapid prototyping technology in
medicine—basics and applications. Computerized Medical Imaging and Graphics 23,
277-284.
Pfeifer, J.S. (1965). THE REACTION OF ALVEOLAR BONE TO FLAP PROCEDURES
IN MAN. Periodontics 20, 135.
Potamianos, P., Amis, A., Forester, A., McGurk, M., and Bircher, M. (1998). Rapid
prototyping for orthopaedic surgery. Proceedings of the Institution of Mechanical
Engineers, Part H: Journal of Engineering in Medicine 212, 383-393.

60
Proffit, W.R., White, R.P., and Sarver, D.M. (2003). Contemporary treatment of
dentofacial deformity, Vol 751 (Mosby St Louis, Mo).
Robertson, D.D., and Rhodes, M.L. (1996). Guest Editors' Introduction: Computers in
Surgery and Therapeutic Procedures. Computer 29, 0020-0023.
Sander, G., Kärcher, H., Gaggl, A., and Kern, R. (1998). Stereolithography versus
milled three-dimensional models: comparison of production method, indication, and
accuracy. Computer Aided Surgery 3, 248-256.
Santler, G. (2000). 3-D COSMOS: a new 3-D model based computerised operation
simulation and navigation system. Journal of Cranio-Maxillofacial Surgery 28, 287-293.
Santoro, M., Galkin, S., Teredesai, M., Nicolay, O.F., and Cangialosi, T.J. (2003).
Comparison of measurements made on digital and plaster models. American Journal of
Orthodontics and Dentofacial Orthopedics 124, 101-105.
Swennen, G.R.J., Barth, E.L., Eulzer, C., and Schutyser, F. (2007). The use of a new
3D splint and double CT scan procedure to obtain an accurate anatomic virtual
augmented model of the skull. International Journal of Oral and Maxillofacial Surgery
36, 146-152.
Webb, P. (2000). A review of rapid prototyping (RP) techniques in the medical and
biomedical sector. Journal of Medical Engineering & Technology 24, 149-153.
Williams, R., Komaragiri, S., Melton, V., and Bishu, R. (1996). Investigation of the effect
of various build methods on the performance of rapid prototyping (stereolithography).
Journal of materials processing technology 61, 173-178.
Xia, J.J., Gateno, J., and Teichgraeber, J.F. (2005). Three-dimensional computer-aided
surgical simulation for maxillofacial surgery. Atlas of the Oral and Maxillofacial Surgery
Clinics 13, 25-39.
Xia, J.J., Gateno, J., and Teichgraeber, J.F. (2009). A new clinical protocol to evaluate
cranio-maxillofacial deformity and to plan surgical correction. Journal of oral and

61
maxillofacial surgery: official journal of the American Association of Oral and
Maxillofacial Surgeons 67, 2093.
Xia, J.J., Phillips, C.V., Gateno, J., Teichgraeber, J.F., Christensen, A.M., Gliddon, M.J.,
Lemoine, J.J., and Liebschner, M.A.K. (2006). Cost-Effectiveness Analysis for
Computer-Aided Surgical Simulation in Complex Cranio-Maxillofacial Surgery. Journal
of Oral and Maxillofacial Surgery 64, 1780-1784.

62
Appendix
Provisional Patent

DM_US 56587805-1.094852.0045

PROVISIONAL PATENT APPLICATION
UNDER 37 C.F.R. 1.53(C)
For
APPARATUS FOR FULL COVERAGE SURGICAL SPLINT

Assignee:

University of Southern California

Applicants/
Inventors:
Dan Grauer
(Santa Monica, California)

Ryan Hungate
(Pasadena, California)

Robert J. Relle
(Calabasas, California)

MCDERMOTT WILL & EMERY LLP
Customer No. 33401
The McDermott Building
500 North Capitol Street, N.W.
Washington, D.C. 20001
Attorney Docket No. 094852-0045
Client Ref. No. USC 2015-083-01

63

094852-0045
USC 2015-083-01
- 2 -
DM_US 56587805-1.094852.0045
APPARATUS FOR FULL COVERAGE SURGICAL SPLINT
BACKGROUND
[0001] Accurate positioning of all bone segments during orthognathic surgery
has previously been addressed, for example, in U.S. Patent 6,671,539, Gateno
et al., inventors, issued December 30, 2003, entitled “Method and Apparatus for
Fabricating Orthognathic Surgical Splints,” the entire content of which is
incorporated herein by reference. This patent describes methods of choice
when fabricating orthognathic surgery splints.
DESCRIPTION
SUMMARY
[0002] The apparatus disclosed herein may facilitate orthognathic surgery by
providing an aligning intermediate and final splint that positions bony segments
(osteotomies).
[0003] The present apparatus and method of use may allow for the accurate
position of all bone segments during orthognathic surgery so as to allow for
more efficient stabilization of the maxillary and mandibular segments during
fixation and therefore creating a more accurate surgical result.
BRIEF DESCRIPTION OF DRAWINGS
[0004] FIGS. 1-5 are included and described in Exhibit 1 hereto, entitled
“Provisional Patent Application: Apparatus for Full Coverage Surgical Split,” the
entire content of which is incorporated herein by reference.
DETAILED DESCRIPTION
[0005] Illustrative embodiments are now discussed and illustrated. Other
embodiments may be used in addition or instead. Details which may be
apparent or unnecessary may be omitted to save space or for a more effective

64

094852-0045
USC 2015-083-01
- 3 -
DM_US 56587805-1.094852.0045
presentation. Conversely, some embodiments may be practiced without all of
the details which are disclosed.
[0006] In one embodiment of the present apparatus and method for its use,
the full coverage surgical splint is created from one or more digital scans
including, but not limited to, a full scan of a patient’s existing skull, upper tooth
arch, and lower tooth arch. This embodiment of the splint may then be
fabricated as a stereolithographic surgical splint and created directly from a
computer, which may therefore be highly accurate. This splint may then be
fabricated from a 3D printer and/or milling machine. The full coverage splint
may cover tooth surfaces on both the inside and outside (buccal and lingual) of
the tooth and allow for the contact, if needed, of the upper and lower arch.
[0007] It is an objective of the present apparatus and method to allow for the
accurate positioning of all bone segments during orthognathic surgery so as to
allow for a more efficient stabilization of the maxillary and mandibular segments
during fixation and therefore creating a more accurate surgical result.
[0008] Further details regarding methods, processes, materials, modules,
components, steps, embodiments, applications, features, and advantages are
set forth in the attached Exhibit 1: “Provisional Patent Application: Apparatus for
Full Coverage Surgical Split” (5 pages), the content of which is incorporated
herein in its entirety. All documents that are cited in Exhibit 1 are also
incorporated herein by reference in their entirety.
[0009] The components, steps, features, objects, benefits and advantages
which have been discussed are merely illustrative. None of them, nor the
discussions relating to them, are intended to limit the scope of protection in any
way. Numerous other embodiments are also contemplated. These include
embodiments which have fewer, additional, and/or different components, steps,
features, objects, benefits and advantages. These also include embodiments in
which the components and/or steps are arranged and/or ordered differently.

65

094852-0045
USC 2015-083-01
- 4 -
DM_US 56587805-1.094852.0045
[0010] Unless otherwise stated, all measurements, values, ratings, positions,
magnitudes, sizes, and other specifications which are set forth in this
specification are approximate, not exact. They are intended to have a
reasonable range which is consistent with the functions to which they relate and
with what is customary in the art to which they pertain.
[0011] All articles, patents, patent applications, and other publications which
have been cited are hereby incorporated herein by reference.

66

094852-0045
USC 2015-083-01

DM_US 56587805-1.094852.0045

EXHIBIT 1

67

PROVISIONAL PATENT APPLICATION
Apparatus for Full Coverage Surgical Splint
BACKGROUND
Field of the Invention:
•
The present invention is directed to facilitate orthognathic surgery by providing an
aligning intermediate and final splint that positions bony segments (osteotomies).
Description of the Related Art:
•
Current Related Art pertains to an existing patent no. US 6,671,539 B2 that was
granted on December 30, 2003. This patent pertains to current methods of choice
when fabricating orthognathic surgery splints.

68
SUMMARY
In one embodiment of the present invention, the full coverage surgical
splint is created from one or more digital scans including but not limited to a full
scan of the patient’s existing skull, upper tooth arch, and lower tooth arch. This
embodiment of the splint would then be fabricated as a stereolithographic surgical
splint and are created from directly from a computer and therefore highly
accurate. This splint may be fabricated from a 3D printer and/or milling machine.
The full coverage splint will cover tooth surfaces on both the inside and out side
(buccal and lingual) of the tooth and allow for the contact, if needed, of the upper
and lower arch.
It is an objective of the present invention to allow for the accurate position
of all bone segments during orthognathic surgery so to allow for a more efficient
stabilization of the maxillary and mandibular segments during fixation and
therefore creating a more accurate surgical result.
BRIEF DESCRIPTION OF THE DRAWINGS

2
4
6
Figure 2
Figure 1

69

Figure 3
8
10
12
Figure 4
14
Figure 5
16
18 20

70
DETAILED DESCRIPTION
1. Decompensation in preparation for orthognathic surgery is carried out.
1.1. This can be done through traditional braces, Clear Aligner Therapy, etc.
2. When the tooth movement achieved allows for jaw relationship correction, a new set of
records is obtained (photos & models).
2.1. Desired post surgery inter-occlusal relationship is assessed by positioning the
models into the corrected position.
2.1.1.Transverse
2.1.2.A-P
2.1.3.Vertical
2.1.4.Individual Tooth Positions are assessed
3. Plaster or 3D models are taken to check surgical occlusion.
4. Immediately prior to surgical workup, braces are removed if present. Attachments are
removed, if present, from Clear Aligner Therapy, so that all surfaces are smooth.
4.1. (Attachments that remain from Clear Aligner Therapy or aligner treatment can
cause increased retention when removing the splint during surgery and this can
dislodge plated osteotomies.)
5. Permanent retainers are bonded to maintain alignment during the initial healing stage to
prevent relapse.
5.1. A Lower bonded 3-3 lingual retainer and a maxillary bonded lingual retainer
using 0.0195 twisted wire are placed.
5.1.1.The maxillary bonded retainer should be placed mesial to the osteotomy
cuts in case of segmented maxilla surgery, and as close vertically as
possible to the incisors’ cingulum.
6. Splint Creation/Design
6.1. Method 1 (Recommended)
6.1.1.The patient’s dentition is scanned with an intraoral 3D scanner.
6.1.2.Dental arches are segmented at the pre-determined osteotomy sites.
6.1.3.The newly segmented arches are repositioned by moving the jaws into a
post-surgical orientation with the correct spatial position, tip, torque, and
rotation of each one of the segments according to the desired final
occlusion. These will be called virtually repositioned models (VRM)
6.1.4.The arches will then be placed so that the desired occlusion is present.
6.1.4.1.Equilibration of premature contacts should be completed in
the software.
6.1.4.2.This equilibration should be noted so that it may be
reproduced during the orthognathic surgery procedure.
6.1.4.2.1.(Ideally, a surgical feasibility study is done and
equilibration is done prior to taking the surgical
impressions. This eliminates the need for intra-operative
equilibration.)
6.1.5.Three surfaces are then exported into the CAM (Computer Aided
Manufacturing) Software:
6.1.5.1.Virtually repositioned models (VRM) (Upper Arch + Lower
Arch) [Figure 3-8]
6.1.5.2.Upper Arch only [Figure 3-10]

71

6.1.5.3.Lower Arch only [Figure 3-12]
6.2. Method 2
6.2.1.Alginate impressions are taken and poured immediately in stone.
6.2.2.Model surgery is performed using pre-determined osteotomy sites.
6.2.3.The newly segmented arches are repositioned to a post-surgical
orientation with the correct spatial positioning, tip, torque, and rotation.
[Figure 4-14]
6.2.4.The arches will then be placed so that the desired occlusion is present.
6.2.4.1.Equilibration should be completed in the software.
6.2.4.2.This equilibration should be noted so that it may be
reproduced during the orthognathic surgery procedure.
6.2.4.2.1.(Ideally, a surgical feasibility study is done and
equilibration is done prior to taking the surgical
impressions. This eliminates the need for intra-operative
equilibration.)
6.2.5.Using inter-occlusal bite registration PVS (Ex. Blue Mousse©), a bite
registration is recorded in the post-surgical bite orientation.
6.2.6.The upper arch [Figure 5-16], lower arch [Figure 5-18], and bite
registration [Figure 5-20] are 3D scanned separately.
6.2.7.Using CAD software, a registration process is performed in order to
match the occlusal position of the pre-surgical models.
6.2.8.Three surfaces are then exported into the CAM (Computer Aided
Manufacturing) Software (Ex. Preform©):
6.2.8.1.Post-model surgery aligned arches (Upper Arch + Lower Arch)
[Figure 3-8]
6.2.8.2.Upper Arch only [Figure 3-10]
6.2.8.3.Lower Arch only [Figure 3-12]
7. A virtual surgical planning session is then conducted by the oral surgeon in order to
position the jaws in the desired position relative to the patient’s cranium, face, and soft
tissue. Here, the desired skeletal corrections are made and surgical guides are generated
using CAD/CAM technology.
7.1. The digital models are registered into the same coordinate system of the patient’s
segmented skull. This is based on the unaltered position of the maxilla. The
desired inter-occlusal position will be dragged along with the changes in position
of the maxilla relative to the patient’s skull.
7.2. The intermediate splint is generated relating the position of the unaltered jaw
position to the corrected position of the mandible/maxilla depending on which is
the first jaw to be repositioned.
7.3. The intermediate splint is designed so that it:
7.3.1.Has complete coverage of the labial/lingual surface [Figure 3-12]
7.3.2.Is festooned along the gingival margins [Figure 1-4]
7.3.3.Allows for adequate occlusal clearance
7.4. The final splint is designed so that it:
7.4.1.Has complete coverage of the labial/lingual surface [Figure 3-12]
7.4.2.Is festooned along the gingival margins [Figure 1-4]
7.4.3.Allows for maxillary and mandibular occlusal contacts [Figure 2-6]

72

8. The merged mid-surgical arches are exported in their corrected position (Upper Arch +
Lower Arch).
9. The merged final arches are exported in their corrected position (Upper Arch + Lower
Arch).
10. Splint design process: The following procedure is performed for both the mid-surgical
aligned arches and the final aligned arches:
10.1.Using a CAD program, a large, all-encompassing shape is merged with the
aligned arches and the arches are then subtracted from the shape.
10.2.The newly created negative of the maxillary and mandibular arches is then
shelled from the buccal face to a width of 1-2mm and from the lingual face by
0.01mm. (These widths can be varied as desired by the oral surgeon) This results
in a 3D object with occlusal holes that allows for contact between the upper and
lower arches when fit to the patient’s occlusion. [Figure 2-6]
10.2.1.This creates a rigid splint to be used during the surgery and allows for
the easy removal of the splint when needed. [Figure 1]
11. The newly generated splint files are then 3D printed using a biocompatible material that
is suitable for operative use.
12. Orthognathic surgery is completed.
12.1.The surgical guides are used to orient both the intermediate and final occlusion.
12.2.When segmental maxillary surgery is planned, the definitive surgical guide is
indexed with the lower dental arch, and then the maxillary segments are brought
into the upper portion of the surgical guide.
12.3.The transparent quality of the guide ensures that the occlusion is precisely
oriented. Proper orientation of the maxillary segments is also ensured because of
the intimate fit that the guide makes with all surfaces of the teeth (similar to how
a clear orthodontic aligner embraces the complete surface area of the teeth).
Maxillomandibular fixation is applied by means of skeletal anchor screws placed
at the start of surgery. This eliminates the possibility of extruding teeth which
will relapse after the maxillomandibular fixation is released. Secure rigid
fixation of the osteotomies is imperative, so that very early jaw mobilization is
permissible. This will permit sufficient jaw motion within a few weeks of
surgery so that aligner trays may be placed.
13. Post-surgery Protocol
13.1.If alignment on the anterior teeth is ideal, then the bonded retainers may remain
as long term retention.
13.1.1.If alignment requires modification, bonded retainers are to be carefully
removed before insertion of the first aligner tray.
13.2.The orthodontist is able to fabricate the needed aligner trays to finish orthodontic
treatment prior to the patient returning from surgery using Clear Aligner Therapy.
13.3.When patient is first seen by the orthodontist post surgery, approximately 2-3
weeks after surgery is completed, the first set of aligner trays will be delivered.
13.4.Aligner trays could be switched on a 5-7 day basis for the first 3 weeks and then
moved to regular 2 week intervals until finished.
13.4.1.The Rapid Acceleratory Phenomenon (RAP) present from the
orthognathic surgery is taken advantage of by switching at the 5-7 day
interval.

73
Full Coverage Splint Methodology Flowchart

Orthodontic Setup for Surgery
- Traditional Braces
-Clear Aligner Therapy
Remove all Orthodontic Appliances &
Bond Permanent Lingual Retainers
(Maxilla & Mandible)
Complete Stone Model
Surgery & Scan w/
Desktop Laser Scanner
Complete Digital Model
Surgery & Create
Virtually Repositioned
Models (VRM)
Complete VSP & Generate
Intermediate & Final Full-Coverage
Surgical Splints
Manufacture Finishing Clear
Aligners (.75mm) for any
Post-Surgery Alignment
Deliver 1st Set of
Clear Aligners
Deliver .75mm Clear Holding Tray
Scan:
- Maxillary Arch
- Mandibular Arch
- PVS Bite Impression
Motionview 3D
©
Export VRM Models in STL Format for
use in Virtual Surgical Plan (VSP) &
Manufacturing of Post Surgery
Aligners
3D Print Full-Coverage
Surgical Splints
(1mm Thick)
Method 1
Method 2
Carryout Orthognathic
Surgery using Full-Coverage
Surgical Splints
2 Weeks Post-Surgery
Complete Orthodontic
Post-Surgery
Alignment using Clear
Aligner Therapy
2 Weeks Pre-Surgery
Scan Teeth Using Intra-Oral Scanner Take Alginate Impressions & Pour in Stone
Remove Bonded Lingual
Retainers if Needed

Abstract (if available)

Abstract Background: Orthognathic surgery is difficult to plan and execute for both the orthodontist and oral surgeon. Though recent strides in technology and diagnostic tools have been made, connecting these tools has not been accomplished in an efficient manner. The advent of virtual surgical planning has brought a new level of detail to surgery, but the execution is still difficult when applied in a clinical setting. By combining 3D printing and virtual surgical planning, a better resultant surgical result may be achieved. ❧ Purpose: In this project, the purpose was to combine existing methods of surgical planning to create a novel full-coverage surgical splint that allowed for better communication between the orthodontist and oral surgeon and to enable a better patient outcome from an increased accuracy of surgical splint and decreased patient finishing times using clear aligner therapy. ❧ Methods: Immediately prior to surgical workup, braces or clear aligner therapy attachments are removed if present so that all surfaces are smooth. The novel full-coverage splint is designed and manufactured using intraoral scanning of the pre-surgical dentition and CAD/CAM creation on a 3D printer. Orthognathic surgery is completed using the full-coverage splint(s) and Maxillomandibular fixation is applied by means of skeletal anchor screws placed at the start of surgery. Post-surgery protocol is completed using clear aligner therapy and the initial clear aligner tray is delivered 2-3 weeks post surgery. ❧ Discussion: The current golden standard for orthognathic surgical planning is still utilizing a plaster model for model surgery and then hand fabricating an acrylic splint. Only the most forward thinking surgeons are utilizing the cutting edge technology of virtual surgical planning and taking CBCT scans of their stone models to have an orthognathic surgical splint wafer printed. There exist inherent flaws with both the golden standard and cutting edge methods of splint fabrication. The advantages of using a full-coverage 3D printed splint are: 1) Increased accuracy of post-surgical occlusion. 2) Increase in patient comfort and acceptance of treatment. 3) Accelerated speed in post surgical orthodontic finishing. ❧ Conclusion: By creating a more accurate and full-coverage splint, the following was achieved: 1) Operating room time is decreased. 2) Patient outcomes, including fewer complications and faster rehabilitation, have been improved. 3) Increased surgical precision. 4) Increased communication between the doctor and patient, including better surgical predictions. 5) Better communication between the surgeon and referring orthodontist. 6) Highly predictable surgical results.

Linked assets

University of Southern California Dissertations and Theses

Conceptually similar

PDF

An assessment of orthognathic surgery outcomes utilizing virtual surgical planning and a patented full-coverage 3D-printed orthognathic splint

PDF

Utilizing voxel based superimposition to asses orthognathic surgical treatment

PDF

Three-dimensional quantification of post-surgical condylar displacement

PDF

Comparison of facial midline landmark and condylar position changes following orthognathic surgery

PDF

Cirtual 3D placement of temporary orthodontic anchorage implants

PDF

Classification of 3D maxillary incisor root shape

PDF

Use of digital models to assess orthodontic treatment progress

PDF

Assessment of 3D surface changes following virtual bracket removal

PDF

The long-term cephalometric and respiratory outcomes of mandibular distraction osteogenesis in infants with Pierre Robin sequence

PDF

The accuracy of intraoral scans of interproximal spaces with and without saliva: a prospective clinical study

PDF

Three-dimensional assessment of tooth root shape and root movement after orthodontic treatment: a retrospective cone-beam computed tomography study

PDF

3D ssessment of bracket position accuracy for lingual appliances using CAD/CAM technology: a pilot study

PDF

3D assessment of virtual bracket removal for modern orthodontic retainers: a prospective clinical study

PDF

A retrospective analysis of the outcome of three methods used for the treatment of multiple gingival recession defects

PDF

Cone-beam computed tomography images: applications in endodontics

PDF

Efficacy of fibrin-assisted soft-tissue promotion (FASTP) in treatment of multiple gingival recession defects: a retrospective 3-D volumetric analysis

PDF

Evaluation of the printing trueness of CAD-CAM maxillary complete denture bases fabricated by using two different DLP 3D printers

Asset Metadata

Creator Hungate, Ryan J. (author)

Core Title The creation of a novel full-coverage orthognathic surgical splint utilizing 3D printing & virtual surgical planning

School School of Dentistry

Degree Master of Science

Degree Program Craniofacial Biology

Publication Date 04/03/2015

Defense Date 03/06/2015

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag 2 piece maxilla,3 piece maxilla,3D printing,3D surgical planning,class II,class III,jaw surgery,LeForte I osteotomy,mandibular advancement,OAI-PMH Harvest,oral surgery,orthodontics,orthognathic,orthognathic surgery,splint,surgical splint

Format application/pdf (imt)

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Sameshima, Glenn T. (committee chair), Grauer, Dan (committee member), Paine, Michael L. (committee member)

Creator Email hungate@usc.edu,rjhungate@gmail.com

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c3-541149

Unique identifier UC11297521

Identifier etd-HungateRya-3248.pdf (filename),usctheses-c3-541149 (legacy record id)

Legacy Identifier etd-HungateRya-3248.pdf

Dmrecord 541149

Document Type Thesis

Format application/pdf (imt)

Rights Hungate, Ryan J.

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the a...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus MC 2810, 3434 South Grand Avenue, 2nd Floor, Los Angeles, California 90089-2810, USA