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A randomized controlled clinical trial evaluating the efficacy of grafting the facial gap at immediately placed implants in the anterior maxilla: 3D analysis of bone and soft tissue changes

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A randomized controlled clinical trial evaluating the efficacy of grafting the facial gap at immediately placed implants in the anterior maxilla: 3D analysis of bone and soft tissue changes

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A Randomized Controlled Clinical Trial Evaluating the
Efficacy of Grafting the Facial Gap at Immediately Placed
Implants in the Anterior Maxilla: 3D Analysis of Bone
and Soft Tissue Changes

Diana Sedler DDS
Master of Science in Craniofacial Biology
Candidate
Committee members
Chair: Dr. Kian Kar
Dr. Casey Chen
Dr. Mahvash Navazesh
Aug 2019
2
Table of Contents

Figure Legend 3
Abstract 5
Introduction 8
Material and methods 13
Protocol overview 13
Study population 13
Types of measurements 17
Statistical Analysis 19
Results 21
Discussion 26
Conclusion 32
References 33
Figures 41
Tables 63
3

Figure Legends

Figure 1: Surgical representation of test and control
Figure 2: Superimposition of CBCT and STL files
Figure 3: Superimposition of pre-op STL onto pre-op CBCT
Figure 4: Superimposition of the pre and post treatment CBCT and STL files
Figure 5: Superimposition of the pre and post treatment CBCT and STL files with lines
demarcating landmakes
Figure 6: Flow chart depicting the superimpostion process
Figure 7: Facial bone thickness
Figure 8: Soft tissue thickness
Figure 9: Soft Tissue height
Figure 10: Papilla height
Figure 11: Facial gap distance
Figure 12: Vertical bone loss
Figure 13: Changes in facial bone thickness bar graph
Figure 14: Vertical bone loss bar graph
Figure 15: Horizontal Implant Distance (HID) bar graph
Figure 16: Changes in soft tissue thickness bar graph
Figure 17: Changes in soft tissue height bar graph
Figure 18: Changes in papilla height bar graph
Figure 19: Correlation between 1mm below the crest pre-op and vertical bone loss scatter plot
Figure 20: Correlation between 1mm below the crest pre-op and 1mm below the crest post-op
scatter plot
4
Figure 21: Correlation between horizontal implant distance and 1mm below the crest post-op
scatter plot
Figure 22: Correlation between horizontal implant distance and vertical bone loss scatter plot
5
Abstract

Objectives:
The aim of this randomized controlled clinical trial was to evaluate the effects of grafting the
facial gap of immediately placed sloped-platform implants on the dimensional changes of the
facial alveolar bone and soft tissue.

Material and Methods:
Extraction sockets were randomized to receive a sloped-platform implant alone (control) or
implant plus anorganic bovine bone mineral (ABBM) in the facial gap (test group). CBCT
images and digitized study casts obtained at baseline and at one year post-operatively were
imported into a three-dimensional (3-D) imaging software for quantitative analysis.

Results:
Mid-facial buccal bone thickness changes at 1mm apical the bone crest demonstrated a gain of
0.30 ± 0.78 mm for the control group, and a gain of 1.20 ± 78 mm for the test group with no
statistical significance.
Mid-facial gingival/mucosal thickness changes at 1mm coronal to the pre-op mid-facial bone
crest exhibited a mean gain of 0.40 ± 0.66 mm in the control group,and a mean gain of 0.73 ±
0.43 mm for the test group.
Mid-facial gingival/mucosal thickness changes at 1mm apical to the pre-op mid-facial bone crest
had a mean gain of 0.88 ± 1.08 mm in the control group, and a mean gain of 0.15 ± 0.71 mm in
the test group with no statistical significance.
6
.
The tissue height was measured from the tissue margin to the bone crest pre-op and post-op after
one year. The mean change of soft tissue thickness was -0.11 ± 1.31 mm
The mean mesial papillae changes from the tip of the papilla to the bone crest from tooth to
implant was 0.8 ± 0.69 mm for the control group, and 0.48 ± 0.49 mm for the test group. The
mean distal papillae changes from the tip of the papilla to the bone crest from tooth to implant
was 0.20 ± 0.5 mm and 0.33 ± 0.44 mm for the control and test groups respectively with no
statistical significance.
.
The mean gap distance between the buccal plate pre-op and the implant in the control group was
1.76 ± 0.09 mm, and 2.82 ± 1.00 mm in the test group.
Correlation and p-value analyses were conducted. Statistical Significance was found in the
correlation of the test group for 1mm subcrestal facial bone thickness to the vertical bone loss
with a p-value of p<0.0001 and r=1.0.

Conclusion:
Due to small sample size minimal statistical analysis was performed, however it was observed
that after immediate implant placement with a bone graft in the facial gap the implant facial bone
was thicker on grafted sites vs non grafted sites. Also, facial soft tissue was thicker around the
implants as compared to the natural teeth in the horizontal direction. There was less recession on
grafted sited in compared to non-grafted sites. Less papillae loss was observed on grafted sites
compared to non-grafted sites. The facial gap measurements in 6 out of the 10 cases was less
7
then 2mm by a mean of 0.30mm (range 0.12 to 0.4mm). There was also more vertical bone loss
in the grafted sites then the non-grafted sites.

8

Introduction
Esthetics in the anterior maxilla is clinically challenging when restoring a tooth, but becomes a
greater challenge when the tooth is extracted. If the tooth will be replaced with an implant,
several changing factors such as hard and soft tissue remodeling, implant positioning, as well as
healing, need to be taken into consideration to achieve an ideal esthetic outcome.

When a tooth is extracted a portion of the bone, known as bundle bone, resorbs due to the
dissection of the periodontal ligament, which results in diminished blood supply and loss of the
stimulatory forces which promote osteoclastic activity (Araujo & Lindhe, 2005). There have
been several studies, both animal and clinical, that have demonstrated that the remodeling which
occurs without intervention post tooth extraction can lead to bone atrophy (Abdelhamid A, 2015;
Araujo & Lindhe, 2005; Cardaropoli, 2003 ; Min S, 2015; Omran M, 2015; Ryu K-H; Schropp,
Wenzel, Kostopoulos, & Karring, 2003). A result of this remodeling is the loss of volume both in
the buccal-lingual and the apical- coronal direction (Araujo & Lindhe, 2005; Atwood, 1963; Van
der Weijden, Dell'Acqua, & Slot, 2009; Wilderman, 1963 ). In order to limit this remodeling and
loss of volume, it is critical to have a foundation of adequate three dimensional hard tissue
volume, as well as facial bone that is intact in both thickness and in height (Buser D, 2004;
Grunder U, 2005) A recent study using three-dimensional (3D) analysis revealed that if the facial
bone in the anterior area is ≤ 1mm, which is considered a thin-wall phenotype, could resorb 3.5
times more than a thick-wall phenotype (E. O. Chappuis V, Reyes M, Shahim K, Nolte LP,
Buser D. , 2013).
9

A consensus systematic review covering the topic of management of extractions sites concluded
that the alveolar ridge undergoes a horizontal dimension loss of up to 3.8 mm and a vertical loss
of up to 1.24 mm in unassisted healing (Hammerle CHF, 2012). Another randomized controlled
clinical trial demonstrated that remodeling of the alveolar ridge continues throughout a 6 month
period and can resorb up to 6mm in the crestal area (Zadeh, 2015). Furthermore, another study
observed a resorption rate of .25mm per week in the first three months was present in extraction
sites with unassisted healing in a canine model (Ryu K-H).

In order to minimize resorption of the ridge, several approaches have been tested to evaluate the
changes. There is a systematic review that concludes that there is 1.47 mm less resorption in the
apical coronal direction and 1.83mm less resorption on the buccal lingual direction when ridge
preservation is used (Vignoletti F, 2012). The different techniques available for ridge
preservation in order to diminish the quantity of remodeling include biomaterials (A. M.
Chappuis V, Buser D. , 2017) with or without the use of a barrier membrane (Meltzer., 1995),
biomaterials with or without a free gingival punch graft (Jung RE, 2004), and extraction socket
devices (Zadeh, 2015).

Since studies have proven that there is hard tissue remodeling and resorption following
extraction of teeth, and there is evidence proving that ridge preservation reduces these
dimensional changes, several studies have evaluated if immediate implant placement also
reduces the dimensional changes that occur post extraction. Several studies have demonstrated
that immediate implant placement does not prevent resorption of the alveolar ridge, resulting in
10
loss of volume in all directions (Clementini, 2015; Covani, 2004; Ferrus J, 2010; C. D. Sanz M,
Ferrus J, Pjetursson EB, LangNP, Jan L. , 2010). One of the studies that evaluated the changes
that occur in the alveolar bone after immediate implant placement revealed that horizontal
resorption of the buccal bone had an average of 56%, and approximately 30% on the palatal bone
(Botticelli, 2004).

Several studies investigated and concluded that an increase in the horizontal gap between the
implant and the facial plate would not only prevent the quantity of resorption that occurs post
extraction, but also aids in formation of bone in the gap (Ferrus J, 2010; Tomasi, 2010). Studies
continued to build on this concept by grafting the facial gap and evaluating the dimensional
changes (Sanz M, 2016). The results of this study revealed that if the facial bone is ≤1 mm, then
grafting of the facial gap is beneficial and reduces resorption. But, if the facial bone is greater
than 1mm, then grafting adds no benefit. After a meta-analysis (Clementini, 2015), a conclusion
was drawn that immediate implants can only be placed in specific cases with bone that is ≥ 1 mm,
which is considered to be a thick-biotype, to prevent significant bone volume changes.

The concept of sloped implants was developed in order to not limit the patient population as
drastically when it comes to immediate implants. A sloped implant has a difference in shoulder
height of 1.5mm from the facial to the palatal aspect. A study was done quantifying how much
resorption takes place on the facial bone in comparison to the palatal bone. The results showed a
1.9 mm loss of vertical bone on the facial bone in contrast to the palatal bone. (Araujo,
Sukekava, Wennstrom, & Lindhe, 2005). A study that evaluated the placement of 65 sloped
implants in a healed sloped ridge after one year showed that a mean loss of 0.54 mm occurs, and
11
the sloped ridge contour is maintained (Noelken R, 2014). Similar results were found in an
animal study as well (Abrahamsson, 2014). There is a lack of data that continues to investigate
the quantity of bone remodeling of implants in extraction sites.

Soft tissue should also be taken into consideration on these specific cases. Studies show that in
most anterior cases, the gingival thickness, also known as phenotype, is between 0.5-1 mm thick
(Müller HP, 2000; Sharma S, 2014). The question then arises that if the tissue is so thin, how is it
measured reproducibly? There are several studies that investigated different modalities to
measure the phenotype. Such modalities include endodontic instruments, synesthetic needles
with a silicone disc stopper, calipers (Zucchelli, 2010), ultrasonic devices (Müller HP, 2000), and
a probe where transparency is visible through the free gingival margin (Kan, 2010). The
disadvantages of these modalities are that they are not extremely accurate and are difficult to
reproduce (Holtfreter, 2012).

Based on current literature, there is no data that studies the volumetric evaluation of both the
hard and soft tissue simultaneously pre- and post-operatively. 3D optical scanning pre- and post-
operatively superimposed with cone beam computer tomography (CBCT) pre- and post-
operatively would facilitate the precise measurement of both the hard and soft tissue, as well as
the volumetric changes that occur.

Aim of the study:
The aim of this study was to evaluate if the placement of ABBM in the facial gap following
immediate implant placement; 1) prevents hard tissue resorption, 2) prevents soft tissue loss and
12
3) if this technique of superimposing optical surface scans of tissue from pre- and post-
operatively onto CBCT scans pre- and post-operatively is a more precise and reproducible way
of measuring the soft and hard tissue remodeling.

Hypothesis:
Placement of anorganic bovine bone minerals (ABBM) in the horizontal gap following
immediate implant placement reduces peri-implant mucosal and alveolar bone dimensional
changes.

Null hypothesis:
The null hypothesis that was tested in this study was that the placement of anorganic bovine bone
minerals (ABBM) in the horizontal gap following immediate implant placement is not correlated
with peri-implant mucosal and alveolar bone dimensional changes.

13
Materials and Methods
Protocol Overview:
The protocol of this study was approved by the Western IRB. Consent was obtained from the
patients before the start of the procedures. This study report has followed the Consolidated
Standards of Reporting Trials (CONSORT) reporting guidelines (supplemental Table 1) for
randomized controlled trials (Moher D, 2011).

The present study was designed as a prospective randomized controlled parallel-arm single
center clinical trial. The primary outcome was to assess the hard and soft tissue dimensional
changes from baseline to 1 year post implant placement. The horizontal gap, between the facial
plate and the implant, post extraction and implant placement was managed by one of two ways;
in the test group the gap was filled with anorganic bovine bone mineral (ABBM) and in the
control group the gap was left without being filled with any material.
The surgical procedures were performed in one private periodontal practice in Southern
California.

Study Population:
The patients were enrolled between October 1
st
, 2011 and March 2013.
Patients planned for a single-tooth replacement in the maxillary anterior and premolar, were
enrolled in this study, if they fulfilled the following inclusion criteria:
• Have one tooth in the maxillary right first premolar to left first premolar location
requiring extraction and implant placement
• Have natural teeth adjacent to proposed site
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• Intact periodontium (<2mm of attachment loss)
• Age 18-75
• Available for one year follow-up
• Consent to clinical trial

The exclusion criteria were as follows:
• Moderate to severe periodontitis (>2mm attachment loss)
• Smoker within past six months
• ASA Class 3+ medically compromised and immunocompromised patients
• Pregnant or plan to be within six months
• Severe bruxism
• History of bisphosphonate use

Study outcome measures:
1) Mid-facial buccal bone thickness changes at increments of 1mm from 1mm, 2mm, 3mm,
4mm, and 5mm, below the bone crest.
2) Mid-facial gingival/mucosal thickness changes at 1mm coronal to the bone crest
3) Mid-facial gingival/mucosal thickness changes at 1mm apical to the bone crest
4) Mid-facial gingival/mucosal margin to the bone crest changes
5) Mesial and distal papillae changes from the tip of the papilla to the bone crest from tooth
to implant
6) True gap distance from the buccal plate to the implant
Intervention and follow-up:
15
This study included only maxillary anterior teeth that were treatment planned for extractions.
The extractions were performed with either an extraction device (Easy X-TRAC System, A.
Titan, Orchard Park, NY) or ultrasonic periotome (EX1 insert, Piezosurgery, Columbus, Ohio)
connected to an ultrasonic device (PIEZOSURGERY®) in order to make the extraction as
atraumatic as possible. The socket was then thoroughly cleansed and debrided with a curette and
was examined to assure lack of dehiscence defects. If a dehiscence was detected, the patient was
excluded from the study.

Osteotomy was performed according to the manufacturers guidelines for the placement of Astra
Tech Osseospeed Profile Tx (Astra Tech AB, Mölndal, Sweden) implant system. Based on the
randomization, using “Random allocation software”
(http://mahmoodsaghaei.tripod.com/Softwares/randalloc.html, Iran) after tooth extraction, test
sites received ABBM in the facial gap (Fig. 1 D-F), while the gap in control sites were left
unfilled (Fig.1 A-C). Once the osteotomy was performed, the final drill was placed into the
socket, the gap distance was measured with a probe to confirm it was at least 2 mm, and then and
the facial gap was then filled for the test sites with ABBM that was hydrated in sterile saline
(Figure 1D). The drill was placed in order to confirm that the bone graft was placed as apical as
possible in the gap without touching the implant with an instrument if the gap were to be grafted
after the implant placement. Following the grafting without flap elevation, implants with sloped
platform (Astra Tech Osseospeed Tx Profile, Mölndal, Sweden) were placed into the extraction
sockets. Healing abutments were placed, no sutures were needed, and the provisional restorations
that were placed were either removable appliances or bonded bridges that did not disturb the
healing process. Post-surgical instructions were given to the participants, and medications
16
prescribed included: chlorhexidine gluconate 0.12% oral rinse used twice a day for 2 weeks,
Amoxicillin 500mg once every 8 hours started 1 hour pre-operatively with a loading dose of
2000 mg and continued for one week, and analgesic Ibuprofen 800 mg as needed. A four month
healing period was allowed before the implant was restored. Implant supported provisional
restorations were made until the definitive restoration was delivered.

CBCT scans and impressions were obtained at baseline and one year after the date of
implantation.

All casts were scanned using an extra oral scanner (D250; 3Shape, Copenhagen, Denmark). The
scanned study model images were exported in a Standard Tesselation Language (STL; 3D
Systems, Rock Hill, SC) format.

CBCT images were acquired with iCAT scanner. The CBCT images were exported in a Digital
Imaging and Communications in Medicine (DICOM)

The baseline and 1 year post op DICOM and STL files were then imported to the Amira®
software (AMIRA; Materialise Inc, Leuven, Belgium) and were superimposed.

The analysis was performed blindly by one examiner (DS), who was not aware of the group
allocation until the analyses were completed. The superimpositions of the models were
performed using the adjacent teeth.

17
Linear measurements were performed to evaluate the dimensional alterations in both groups.

Superimposition was performed to allow measurements in the same cross-sectional locations
within serial CBCT images. Briefly, the pre- and post-op CBCT images were trimmed to the
maxillary arch. The maxillary arches were aligned manually to close proximity, followed by
software registration for fine-tuning of the superimposition of the pre- and post-op images (Fig.
2A). Next, the pre- and post-op STL files of surface-scanned models were imported into the
Amira software and converted into volumes. The same steps were followed for the
superimposition of the STL files by an initial manual alignment, and later, an automatic
alignment (Fig. 2B). Once the two CBCT images and the two STL images were superimposed,
the post-op CBCT and STL files were toggled off to only visualize pre-op CBCT and STL files,
to allow the superimposition of those two files using the same manual movements and program
registration process as seen in Fin 3. Following the superimposition of the pre-op CBCT and
STL files, the corresponding post-op images were toggled back on to verify proper
superimposition of all four structures as seen in Fig 4. Once all four were superimposed, a
measurement of the mesial-distal length of the treated tooth was taken in order to bisect the tooth
and get a cross-section view in order to make consistent measurements. Two-dimensional cross-
sections were used to verify superimposition was correct on the four scans and to make linear
measurements (Fig. 4 & 5). A flow chart of the process of superimposition is depicted in Fig. 6.

Types of measurements:
Horizontal hard tissue contour changes at 1, 2, 3, 4, 5 mm from the position of the pre-op bone
crest:
18
Horizontal buccal bone contour changes were assessed at 1, 2, 3, 4, 5 mm from the crest of the
bone 1 year after implant installation: Using the bone crest of the post-op CBCT scan as a
reference, a 5 mm line was drawn as a reference line. Then, a second line was drawn at 1 mm
increments to obtain a reference where the horizontal measurements would be. Another plane
was then made at each millimeter to verify the measurements were parallel. Measurements were
taken on pre- and post-op scans of the buccal bone thickness. (Fig. 7)

Horizontal soft tissue contour changes at 1mm coronal and 1mm apical from the position of the
pre-op bone crest (phenotype):
Soft tissue contour changes were measured similarly at 1mm coronal and apical to the buccal
bone crest using the pre-op bone crest as reference. A reference line was drawn 1mm coronal and
1mm apical to the bone crest on the pre-op mid-facial cross-section of the CBCT and STL. A
plane was made perpendicular to the cross-section to confirm the measurements were horizontal.
Measurements were made at the same points on the post-op CBCT and STL scans. (Fig 8)

Mid-facial vertical mucosal change:
In both the pre- and post-op scans, another measurement was taken to measure soft tissue height
changes from the bone crest to the tip of the free gingival/mucosal margin. (Fig 9)

Mesial and distal papilla height change:
Papillae height changes were made on the mesial and distal papilla. A cross-section was made at
the midsection of the papilla on the mesial and distal, and a linear measurement was taken from
the tip of the papilla until the bone crest on both pre-op and post-op scans. (Fig 10)
19

Gap distance between the buccal plate and the implant:
The gap distance was measured using the pre-op and post-op CBCT. The mid-facial cross
section of the pre-op tooth was taken with the corresponding post-op cross section, and the
distance from the platform of the implant to the pre-op junction of the tooth to the buccal bone
was recorded as the gap distance. (Fig. 11)

Vertical bone loss:
The amount of bone loss that occurred on the facial plate in the vertical direction was measured
using the pre-op and post-op CBCT. The mid-facial cross section of the pre-op tooth was taken
with the corresponding post-op cross section. The pre-op cross section was made 25%
transparent in order to visualize both scans at the same time. A measurement was taken from the
pre-op crest to the level of the post-op crest. (Fig. 12)

Statistical Analysis:
Descriptive statistics were calculated for all variables of interest. Continuous measures such as
age were summarized using means and standard deviations, whereas categorical measures were
summarized using counts and percentages. Correlations between variables of interest were
analyzed. Due to the small sample sizes, the non-parametric Spearman correlation coefficient
was used in place of the Pearson correlation. Results were reported as correlation coefficients
and their associated p-values. All analyses were run using SAS Version 9.4 (SAS Institute, Cary,
NC, USA).
20
One of the outcomes was the differences in the dimension of the the soft tissues between the
control and the study surgical procedures. The dimensions of the soft tissues (i.e., gingival tissue
before tooth extractions, and peri-implant mucosa after placement of implants) were measured at
1mm coronal and apical to the mid-buccal bone crest. G*power was used to estimate how many
patients are needed to detect a difference of 1 mm between the control and the study groups with
significance set at 0.05 and 80% power. It is acknowledged here that the calculation was made
based on the standard deviations from the limited number of patients in the preliminary study. A
summary of the sample size analysis is provided in the table.

21
Results:
Clinical characteristics of study subjects:
A total of 15 potential participants were screened for this randomized controlled clinical trial and
10 individuals met the inclusion criteria and were enrolled in this study. No subjects dropped out
during the observation period. The pre-op and 1-year post-year CBCT scans and study casts for
10 participants were of suitable quality to be included for the detailed 3D soft and hard tissue
linear analysis.

The mean age of the subjects was 51.76 ± 17.45 in the control group and 65.9 ± 12.52 in the test
group. The subjects included 1 male and 4 females in the control group, and 3 males and 2
females in the test group. All implants placed were 4.5mm in diameter. Three implants in the
control group were 13 mm long and two implants were 15mm long. In the test group, one
implant was 11 mm long, two implants were 13mm long, and two implants were 15mm long
(Table 1). All patients healed uneventfully, and were restored.

Horizontal hard tissue contour changes at 1, 2, 3, 4, 5 mm from the position of the pre-op bone
crest:
In the control group, the mean horizontal dimensional changes relative to the pre-operative mid-
facial bone crest were a gain of 0.30 ± 0.78 mm at 1mm, 0.16 ± 0.79 mm at 2mm, 0.09 ± 0.92
mm at 3mm, 0.11 ± 0.93 mm at 4 mm, 0.17 ± 0.80 mm at 5 mm. In the test group, the mean
horizontal dimensional changes in the same positions were a gain of 1.20 ± 78 mm at 1mm, 1.37
± 0.76 mm at 2mm, 1.51 ± 0.68 mm at 3mm, 1.78 ± 0.66 mm at 4mm, 1.99 ± 0.77 mm at 5mm
respectively. (Table 2, Fig.13)
22

Horizontal soft tissue contour changes at 1mm coronal and 1mm apical from the position of the
pre-op bone crest (phenotype):
At 1mm coronal to the pre-op mid-facial bone crest, there was a mean gain of 0.40 ± 0.66 mm in
the control group. At this level, the initial gingival thickness was 1.85 ± 0.49 mm and the post-op
mucosal thickness was 2.46 ± 0.34. At 1mm coronal to the pre-op mid-facial bone crest, there
was a mean gain of 0.73 ± 0.43 mm in the test group. At this level, the initial gingival thickness
was 2.24 ± 1.12 mm and the post-op mucosal thickness was 2.53 ± 0.38.
At 1mm apical to the pre-op mid-facial bone crest, there was a mean gain of 0.88 ± 1.08 mm in
the control group. At this level, the initial gingival thickness was 1.09 ± 0.48 mm and the post-op
mucosal thickness was 1.97 ± 1.34. At 1mm apical to the pre-op mid-facial bone crest, there was
a mean gain of 0.15 ± 0.71 mm in the test group. At this level, the initial gingival thickness was
2.01 ± 1.25 mm and the post-op mucosal thickness was 1.92 ± 1.52. (Table 4, Fig. 16)

Mid-facial vertical mucosal change:
The tissue thickness was measured from the tissue margin to the bone crest pre-op and post-op
after one year. The mean change of soft tissue thickness was -0.11 ± 1.31 mm (range: -1.25 to
1.5mm) for the control group and -1.73 ± 1.39mm (range: -3.24 to -0.5) for the test group. (Table
5, Fig.17)

Mesial and distal papilla height change:
23
The mean mesial papillae loss was 0.8 ± 0.69 mm for the control and 0.48 ± 0.49 mm for the test
groups. The mean distal papillae loss were 0.20 ± 0.5 mm and 0.33 ± 0.44 mm for the control
and test groups, respectively. (Table 6, Fig. 18)

Gap distance between the buccal plate and the implant:
The mean gap distance between pre-op buccal plate and the implant in the control group was
1.76 ± 0.09 mm, with a range of 1.67mm to 1.9mm. The mean gap distance between pre-op
buccal plate and the implant in the test group was 2.82 ± 1.00 mm, with a range of 1.78 to 4.04.
(Table 3, Fig 15)

Vertical bone loss:
The mean vertical bone loss between the pre-op bone crest to the post-op bone crest in the
control group was 0.78 ± 0.64mm, with a range of 0.1mm to 1.43mm. The mean vertical bone
loss between the pre-op bone crest to the post-op bone crest in the test group was 2.13 ± 1.71mm,
with a range of 0.3mm to 3.7mm. (Table 3, Fig. 14)

Correlation coefficient and p-value analysis:
Correlation coefficient and p-value analyses were performed between crestal bone thickness
1mm below the crest pre-operatively and the vertical bone loss 1 year after placement. In the
control group, a negative correlation of (r=-0.63) observed that was not statistically significant
with a p-value of (p=0.25). In the test group, there was a positive correlation of (r=1.0) with a p-
value of (p<0.0001). In the test and control group combined a positive correlation of (r=0.12)
was observed that was not statically significant with a p-value of (p=0.78). (Fig. 19)
24

Correlation coefficient and p-value analyses were performed between the crestal bone thickness
1mm below the crest pre-operatively to the post-operative crestal bone thickness 1mm below the
crest. In the control group, a positive correlation of (r=0.79) was observed that was not statically
significant with a p-value of (p=0.11). In the test group, a positive correlation was observed that
was not statically significant (r=0.63) with a p-value of (p=0.37). In the test and control group
combined there a positive correlation of (r=0.47) was observed that was not statically significant
with a p-value of (p=0.20). (Fig. 20)

Correlation coefficient and p-value analyses were performed between the horizontal implant
distance and the post-operative crestal bone thickness 1mm below the crest. In the control group,
there a positive correlation of (r=0.50) was observed that was not statically significant with a p-
value of (p=0.39). In the test group, there was a negative correlation of (r=-0.40) with a p-value
of (p=0.60). In the test and control group combined a positive correlation of (r=0.30) was
observed that was not statically significant with a p-value of (p=0.43). (Fig. 21)

Correlation coefficient and p-value analyses were performed between the horizontal implant
distance to the vertical bone loss. In the control group, a negative correlation of (r=-0.10) was
observed that was not statically significant with a p-value of (p=0.87). In the test group, there a
negative correlation of (r=-0.50) was observed that was not statically significant with a p-value
of (p=0.67). In the test and control groups combined, a positive correlation of (r=0.12) was
observed that was not statically significant with a p-value of (p=0.78). (Fig. 22)

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Power analysis:
Based on G-power analysis the sample size that is needed to have a 1mm difference in soft tissue
thickness 1mm coronal to the bone crest between the test and the control is 12 patients total with
6 patients in the test and 6 in the control. In we lower the threshold to 0.5mm difference between
the test and control a sample size of 40 patients is needed 20 in the test and 20 in the control.
(Table 7)
26
Discussion:
The present single center randomized controlled clinical trial was performed to test the null
hypothesis that placement of anorganic bovine bone minerals (ABBM) in the horizontal gap
following immediate implant placement is not correlated with peri-implant mucosal and alveolar
bone dimensional changes. Based on the protocol in the study, flapless tooth extraction was
performed using the Easy X-TRAC system or an ultrasonic periotome insert on the Piezosurgery
followed by a sloped platform implant placement with a 2mm horizontal gap present between the
implant and the bone with grafting, dimensional changes in both the hard and soft tissue were
observed.

The present study observed a mid-facial horizontal bone gain of 0.30 mm, with a range of
resorption from 1.4 mm to a gain of 0.54 mm in the control sites, and a gain of buccal bone
thickness of 0.39 mm, with a range of resorption from 1.69 mm to a gain of 2.14 mm in the test
sites. The results of this study did not seem to follow the mean trends in (Clementini M & M.,
2015) systematic reviews and meta-analyses, although the ranges that were found in this study in
the non-grafted sites were similar to the ranges found in (C. D. Sanz M, Ferrus J, Pjetursson EB,
LangNP, Jan L. , 2010) articles.

A reason that this may have not followed the typical trend is due to the gap size. Many studies
have proven that the size of the gap between the implant and the facial bone plays a role in the
esthetic outcomes of the peri-implant contours. In the clinical trial by (C. D. Sanz M, Ferrus J,
Pjetursson EB, Lang NP, Jan L. , 2010) the gap in the control group that had no grafting resorbed
2.23 mm, and if the facial bone was less then 1 mm, then it resorbed 2.25 mm. But, when the gap
27
was grafted, there was a resorption of 1.57 mm, and if the facial bone was less then 1mm, then
the bone resorbed only 0.91 mm. In a study by (Ferrus J, 2010), an immediate implant was
placed in a fresh extraction socket with a gap of 2.1 mm. In the facial bone of ≤ 1mm or
≥1mm ,the gap fill was 67% and 85% respectively.

Based on classic literature, the buccal plate receives its blood supply from the periodontal
ligament, bone marrow, and outer periosteum (Carranza, 1966), The bundle bone, consisting of
lamellar bone, has a thickness of 0.2-0.4 mm and is a tooth dependent structure (HE., 1986).
When considering that the facial bone in the maxillary anterior teeth is in most cases less then 1
mm thick (Huynh-Ba G, 2010), the bone in this site will be comprised mostly of cortical bone.
Then, when the tooth is extracted from this site removing the periodontal ligament, it causes the
bundle bone to resorb and removes a source of blood supply to the bone - the only blood supply
left for the bone will be from the periosteum. Furthermore, if a flap is elevated, then the last
source of blood supply to the bone is removed, causing further resorption. Several current studies
concluded that a thick facial wall will have significantly less resorption then a thin facial wall
that can resorb anywhere between 1.2 mm – 7.1 mm depending on the study (E. O. Chappuis V,
Reyes M, Shahim K, Nolte LP, Buser D. , 2013; Lee EA, 2014). Two studies recently evaluated
the frequency that the facial bone is less then 1 mm, and both studies found that in 85%-87% of
the time, the facial bone is thin (Huynh-Ba G, 2010; Januario AL, 2011).

With the conclusions presented in these studies (Carranza, 1966; Ferrus J, 2010; HE., 1986; C. D.
Sanz M, Ferrus J, Pjetursson EB, LangNP, Jan L. , 2010), as well as taking into consideration
that in the current study, the mean non-grafted sites gap size was 1.76mm, the mean grafted sites
28
gap size was 2.82, the average facial bone thickness pre-operatively 1mm below the crest, in
both the test and control sites were 0.96 and 1.17 respectively, it can be thought that the facial
bone present post-operatively could be thicker due to the filling of the gap when the facial bone
is over 1mm. This could also be due to the fact that when graft material is added, there is a
decrease in volume loss. Also, based on studies such as (Mazzocco F, 2017), when the volume
loss is calculated it is based on the total ridge volume from palatal to facial, not just the changes
in the facial plate. It can be speculated that even though the ridge could be losing volume due to
remodeling, when the implant is placed more palatally and the facial gap is grafted, the facial
bone itself could become wider than the bone originally present on the tooth.

The facial plate is considered to play a crucial role in determining the level in which the peri-
implant mucosa will be positioned (Lekholm U, 1996). In one study by (Kan JY, 2008) it was
concluded that immediate implant placement into sites with a dehiscence defect, 34.8% recession
was present. When there was loss of attachment in the interproximal of adjacent teeth, recession
of 1.5 mm was found 100% of the time.

The bone is shown to influence the soft tissue. In this study, we evaluated the migration of the
mucosal zenith in reference to the facial bone crest, and the results showed that the zenith
migrated apically 0.81 ± 1.5 mm, which is similar to previously published articles (Cordaro L,
2009; De Rouck T, 2009). In the De Rouck randomized clinical trial, it was evaluated whether
placement of a provisional restoration on the same day as immediate implant placement prevents
the mucosal margin from migrating apically as much. The conclusion of the study revealed that
with a provisional restoration, the margin receded 0.41 mm, whereas, without a provisional (but
29
with a healing abutment) the margin receded 1.16 mm. When the implant was completely
submerged, the recession was 2.5-3 times higher than those that were not submerged. Another
study by Cordaro et al 2009 who also evaluated immediate implants that were either submerged
or non- submerged they found that there was 0.73 mm and 0.82 mm migration of the margin,
respectively. A systematic review concluded that with immediate implant placement is correlated
with unpredictable mucosal margin recession and there is a great deal of heterogeneity among
the studies that show that recession over 1 mm is present in cases between 9- 41% as compared
to early implant placement (Chen ST, 2014).

The question then arises that if some type of apical migration is inevitable with immediate
implant placement, does phenotype influence the quantity of apical migration that will occur? In
this study, we found that the soft tissue thickness in the control and test group was 1.85 ±
0.49mm and 2.24 ± 1.12mm, respectively, but this tissue still migrated apically 0.11 ± 1.3mm in
the control and 1.73 ±1.39mm in the test. These results are in consensus with many studies such
as (Van Kesteren CJ, 2010) and (Cabello G, 2013; Evans CD, 2008) who all demonstrated that
even though a thin phenotype observes greater changes, there is no statistical significant
difference between the changes that occur between a thin and thick phenotype. But with this
taken into consideration, no study has yet evaluated the tissue phenotype the way it was
evaluated in this study with two, pre- and post-operative, soft tissue STL models superimposed
onto two, pre- and post-operative, CBCT scans. In this study, we were able to have the same
sections on both pre- and post-operative scans and models and make accurate measurements
because we were able to visualize where the bone stopped and the soft tissue started in order to
get the true horizontal measurement of the soft tissue without having to round to the nearest half
30
a mm as in previous studies. Previous studies used endodontic instruments, synesthetic needles
with a silicone disc stopper, calipers (Zucchelli, 2010), ultrasonic devices (Müller HP, 2000), and
a probe where transparency is visible through the free gingival margin (Kan, 2010). The
disadvantage of all of these modalities is that they are not extremely accurate and are difficult to
reproduce (Holtfreter, 2012).

Lastly, immediate implant placement is frequently associated with loss of papilla height (Lang
NP, 2012). In the present study, there was a linear loss on the mesial papillae of 0.8 ± 0.69 mm
and 0.48 ± 0.49 mm for the control and test groups, respectively, and on the distal papillae 0.20 ±
0.5 mm and 0.33 ± 0.44 mm for the control and test groups, respectively. The numbers in this
study are found to be minimal changes, which is in agreement with previous studies. A
randomized clinical trial found similar results with a mean loss of 0.53 mm on the mesial
papillae and 0.31 mm on the distal papillae (Van Kesteren CJ, 2010). Another study by
(Juodzbalys G, 2007) found that the papilla does not fill the interdental spaces all the way to the
contact point in 64.3% of the cases. Although this papilla loss can be attributed to tooth
extraction and immediate implant placement we also know that there are several factors that
contribute to the height of the papillae and how much it fills the interdental spaces. Some of the
factors included are the height of the contact point (Tarnow, 1992), the gingival biotype (Kan
JYK, 2003), the level of the interproximal bone (Grunder U, 2005), and the crown shape (Min-
Chieh Chen, 2010). Therefore, with this taken into consideration, many different factors can
influence the loss of papillae, but if we can control a few of these factors such as bone height by
grafting the facial gap and its possible influence on thickening of the mucosa, this might help
limit the loss of height in the papillae.
31

The present study did have several limitations: 1) small sample size, 2) restoration factors that
can influence the tissue position, 3) volumetric error in the process of taking impressions such as
shrinkage and expansion in the impression material and stone casts, and 4) the study did not have
a split mouth design. In order to obtain more definitive conclusions, all of these factors should be
taken into consideration when designing a study to evaluate all the parameters that were done in
this study.

32
Conclusion:
Due to small sample size minimal statistical analysis was performed, however it was observed
that after immediate implant placement with a bone graft in the facial gap the implant facial bone
was thicker on grafted sites vs non grafted sites. Also, facial soft tissue was thicker around the
implants as compared to the natural teeth in the horizontal direction. There was less recession on
grafted sited in compared to non-grafted sites. Less papillae loss was observed on grafted sites
compared to non-grafted sites. The facial gap measurements in 6 out of the 10 cases were less
then 2mm by a mean of 0.30mm (range 0.12 to 0.4mm). There was also more vertical bone loss
in the grafted sites then the non-grafted sites.

33

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41

Figure 1

Fig. 1. Representative control (A-C) and test (D-F) clinical cases. (A) Tooth extraction with
intact mucosa and bone. (B) Sloped platform implant inserted into the socket. (C) Palatal
position of an implant in a control site. (D) placement of xenograft in socket while the final drill
was inserted into the osteotomy. After removal of the drill, the osteotomy site was optimal for
implant placement. (E) Implant placement into grafted socket. (F) Implant position in situ with
xenograft in the facial gap.

42
Figure 2

Fig. 2. (A) Superimposition of the pre and post treatment CBCT files. (B) Superimposition of the
pre and post treatment STL files.

43
Figure 3

Fig. 3. Superimposition of the pre CGCT and pre STL with the yellow line demarcating the pre-
op soft tissue on the CBCT scan.

44
Figure 4

Fig. 4. Superimposition of the pre and post treatment CBCT and STL files. (A) Superimposition
of the pre-op CBCT with the STL. The yellow line demarcates the pre-op soft tissue. (B)
Superimposition of the post-op CBCT with the STL. The red line demarcates the post-op soft
tissue (C) Superimposition of the pre and post-op CBCT with the STL The yellow line
demarcates the pre-op soft tissue and the red line demarcates the post-op soft tissue.

45
Figure 5

Fig. 5. Superimposition of the pre and post treatment CBCT and STL files. (A) Superimposition
of the pre-op CBCT with the STL. The yellow line demarcates the pre-op soft tissue the blue
dotted line is the bone and the green solid line is the tooth (B) Superimposition of the post-op
CBCT with the STL. The red line demarcates the post-op soft tissue the orange dotted line is the
bone and the fucia is the outline of the implant. (C) Superimposition of the pre and post-op
CBCT with the STL with all the same previous lines superimosed.

46
Figure 6

Fig. 6. Flow chart depicting the superimpostion process and the resulting cross sections with soft
tissue outlines on the CBCT slices.

47
Figure 7

Fig. 7. Superimposition of the pre and post treatment CBCT and STL files with linear
measurements of the buccal bone thickness at 1, 2, 3, 4, and 5 mm. (A) Superimposition of the
pre-op CBCT with the STL. The yellow line demarcates the pre-op soft tissue the blue dotted
line is the bone and the green solid line is the tooth. Arrows in beige depict the 1mm increments
at which the measurements were taken. (B) Superimposition of the post-op CBCT with the STL.
The red line demarcates the post-op soft tissue the orange dotted line is the bone and the fucia is
the outline of the implant. The arrows in beige depict the 1mm increments at which the
measurements were taken.

48
Figure 8

Fig. 8. Superimposition of the pre and post treatment CBCT and STL files with linear
measurements of the soft tissue thickness at 1mm coronal and apical to the bone crest. (A)
Superimposition of the pre-op CBCT with the STL. The yellow line demarcates the pre-op soft
tissue the blue dotted line is the bone and the green solid line is the tooth. Arrows in pink depict
the 1mm increments at which the measurements were taken. (B) Superimposition of the post-op
CBCT with the STL. The red line demarcates the post-op soft tissue the orange dotted line is the
bone and the fucia is the outline of the implant. The arrows in pink depict the 1mm increments at
which the measurements were taken.

49
Figure 9

Fig. 9. Superimposition of the pre and post treatment CBCT and STL files with linear
measurements of the soft tissue height. (A) Superimposition of the pre-op CBCT with the STL.
The yellow line demarcates the pre-op soft tissue the blue dotted line is the bone and the green
solid line is the tooth. Arrows in yellow depict the measurement that was taken from the bone
crest to the free gingival margin. (B) Superimposition of the post-op CBCT with the STL. The
red line demarcates the post-op soft tissue the orange dotted line is the bone and the fucia is the
outline of the implant. The arrows in yellow depict the measurement that was taken from the
bone crest to the free gingival margin.

50
Figure 10

Fig. 10. Superimposition of CBCT and STL file at cross-sections of the papillae with linear
measurement of the height of the papilla. Superimposition of the pre-op CBCT with the STL.
The yellow line demarcates the pre-op soft tissue. The arrow in blue depict the measurement that
was taken from the bone crest to the tip of the papilla.

51
Figure 11

Fig. 11. Superimposition of the pre and post treatment CBCT and STL files with linear
measurements of the facial gap distance. The yellow line demarcates the pre-op soft tissue the
blue dotted line is the bone and the green solid line is the tooth. The red line demarcates the post-
op soft tissue the organge dotted line is the bone and the fucia is the outline of the implant. The
arrow in blue depict the measurement that was taken from the implant platform until the junction
of the root and bone.

52
Figure 12

Fig. 12. Superimposition of the pre and post treatment CBCT files with linear measurements of
the vertical bone loss. Superimposition of the pre-op CBCT with the post-op CBCT. The orange
lines demarcates the pre-op bone crest and the post-op bone crest. The arrows in blue depicts the
measurement that was taken from the pre-op bone crest to the post-op bone crest.

53

Figure 13

Fig. 13. Mean changes in facial bone thickness between control pre-op (yellow), control post-op
(gold), test pre-op (red), and control post-op (cardinal) at 1mm increments apical from the bone
crest.
0
0.5
1
1.5
2
2.5
3
3.5
1mm 2mm 3mm 4mm 5mm
Crestal bone thickness
1mm increments from the bone crest
Changes in facial bone thickness
Control Pre-op Control Post-op Test Pre-op Test Post-op
54

Figure 14

Fig. 14. Mean verical bone loss between control (yellow) and test (red) from the pre-op bone
crest to the post-op bone crest.
0
0.5
1
1.5
2
2.5
Vertical bone loss
Quantity of bone loss in MM
Vertical bone loss
Control Test
55

Figure 15

Fig. 15. Mean horizontal implant distance (HID) between control (yellow) and test (red) from
the implant platform until the junction of the root and bone.

0
0.5
1
1.5
2
2.5
3
Gap distance in MM
Horizontal Implant Distance (HID)
Control Test
56

Figure 16

Fig. 16. Mean changes in soft tissue thickness between control pre-op (yellow), control post-op
(gold), test pre-op (red), and control post-op (cardinal) at 1mm coronal and 1mm apical from the
bone crest.
0
0.5
1
1.5
2
2.5
3
1mm coronal to bone crest 1mm apical to bone crest
soft tissue thickness in MM
Changes in soft tissue thickness
Control Pre-op Control Pre-op Test Pre-op Test Post-op
57

Figure 17

Fig. 17. Mean changes in soft tissue height between control pre-op (yellow), control post-op
(gold), test pre-op (red), and control post-op (cardinal) measured from the bone crest to the free
gingival/ mucosal margin.
0
1
2
3
4
5
6
Height of soft tissue in MM
Changes in soft tissue height
Control Pre-op Control Post-op Test Pre-op Test Post-op
58

Figure 18

Fig. 17. Mean changes in papilla height between control pre-op (yellow), control post-op (gold),
test pre-op (red), and control post-op (cardinal) measured from the bone crest to the tip of the
papilla on both the mesial and distal papilla.

0
1
2
3
4
5
6
7
Mesial Papilla Distal Papilla
Height of papilla in MM
Changes in papilla height
Control Pre-op Control Post-op Test Pre-op Test Post-op
59

Figure 19

Figure 19: Correlation between 1mm below the crest pre-op and vertical bone loss scatter plot
with trend lines comparing the control (gold) to the test (red). There was a negative correlation of
r=-0.63 and a p-value of p=0.25 in the control, which was not significant and a positive
correlation of r=1.0 and a p-value of p=<0.0001 in the test group, which was statistically
significant.

0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 0.5 1 1.5 2 2.5
Vertical Bone Loss in MM
1mm below crest pre-op
Control
Test
Linear (Control)
Linear (Test)
60

Figure 20

Figure 20: Correlation between 1mm below the crest pre-op and 1mm below the crest post-op
scatter plot with trend lines comparing the control (gold) to the test (red). There was a positive
correlation of r=0.79 and a p-value of p=0.11 in the control, which was not significant and a
positive correlation of r=0.63 and a p-value of p=0.37 in the test group, which was not significant.

0
0.5
1
1.5
2
2.5
3
3.5
4
0 0.5 1 1.5 2 2.5
1mm below crest post-op
1mm below crest pre-op
Test
Control
Linear (Test)
Linear (Control)
61

Figure 21

Figure 21: Correlation between horizontal implant distance and 1mm below the crest post-op
scatter plot with trend lines comparing the control (gold) to the test (red). There was a positive
correlation of r=0.50 and a p-value of p=0.39 in the control, which was not significant and a
negative correlation of r=-0.40 and a p-value of p=0.60 in the test group, which was not
significant.

0
0.5
1
1.5
2
2.5
3
3.5
4
0 1 2 3 4 5
1mm below crest post-op
Horizontal implant Distance (HID)
Test
Control
Linear (Test)
Linear (Control)
62

Figure 22

Figure 22: Correlation between horizontal implant distance and vertical bone loss scatter plot
with trend lines comparing the control (gold) to the test (red). There was a negative correlation of
r=-0.10 and a p-value of p=0.87 in the control, which was not significant and a negative
correlation of r=-0.50 and a p-value of p=0.67 in the test group, which was not significant.
-1
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
4
0 2 4 6
Vertical Bone Loss in MM
Horizontal implant Distance (HID)
test
Control
Linear (test)
Linear (Control)
63

Table 1

Control (N=5) Test (N=5)
Age 51.76 ± 17.45 65.9 ± 12.52
Sex (M/F) 1/4 3/2
Implant Length
11mm/ 13mm/ 15mm
0/3/2 1/2/2
Implant Diameter
4.5/ 5.0
5/0 5/0
Smokers (Y/N) 0/5 0/5
Site
Central/ Lateral/ Canine
3/0/2 4/0/1

Table 1. Clinical characteristics of study patients, as well as sites. Demographics, implant
dimensions, sites and participants characteristicis

64
Table 2
Test A

Control B

Table 2. Measurements obtained for each patient at 1, 2, 3, 4, and 5 mm increments pre- and post
op for both (A) test and (B) control.

65
Table 3
Test A

Control B

Table 3 . Measurements obtained for each patient from pre-op bone crest to post- op bone crest
representing the vertical bone loss as well as implant plateform to the juction of the root to the
bone representing horizontal implant distance (HID) pre- and post op for both (A) test and (B)
control.

66
Table 4
Test A

Control B

Table 4. Measurements obtained for each patient at 1mm coronal and apical to the bone crest
pre- and post op for both (A) test and (B) control.

67
Table 5 A
Test

Control B

Table 5. Measurements obtained for each patient from the mucosal margin (mm) to the bone
crest (BC) pre- and post op for both (A) test and (B) control.

68
Table 6 A
Test

Control B

Table 6 . Measurements obtained for each patient from the tip of the mesial (M) papilla to the
bone crest (BC) and the distal (D) papilla to the bone crest (BC) at pre- and post op for both (A)
test and (B) control.

69
Table 7

Table 7. G-power analysis results containing 1mm difference between test and control in the top
table and 0.5mm difference in the bottom table.

Abstract (if available)

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Asset Metadata

Creator Sedler, Diana (author)

Core Title A randomized controlled clinical trial evaluating the efficacy of grafting the facial gap at immediately placed implants in the anterior maxilla: 3D analysis of bone and soft tissue changes

School School of Dentistry

Degree Master of Science

Degree Program Craniofacial Biology

Publication Date 07/25/2019

Defense Date 05/22/2019

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

Tag bone changes,bone graft,contour changes,facial gap,grafting,immediate implant,implant,OAI-PMH Harvest,profiled implant,Regeneration,scalloped implant,tissue augmentation

Format application/pdf (imt)

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Chen, Casey (committee chair), Kar, Kian (committee chair), Navazesh, Mahvash (committee chair)

Creator Email Dsedler@gmail.com,Sedler@gmail.com

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c89-191421

Unique identifier UC11663378

Identifier etd-SedlerDian-7617.pdf (filename),usctheses-c89-191421 (legacy record id)

Legacy Identifier etd-SedlerDian-7617.pdf

Dmrecord 191421

Document Type Thesis

Format application/pdf (imt)

Rights Sedler, Diana

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