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Maxillary sinus floor and alveolar crest alterations following extraction of maxillary molars: a retrospective CBCT analysis

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Maxillary sinus floor and alveolar crest alterations following extraction of maxillary molars: a retrospective CBCT analysis

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Content 1
UNIVERSITY OF SOUTHERN CALIFORNIA
OSTROW SCHOOL OF DENTISTRY

MAXILLARY SINUS FLOOR AND
ALVEOLAR CREST ALTERATIONS
FOLLOWING EXTRACTION OF
MAXILLARY MOLARS: A
RETROSPECTIVE CBCT ANALYSIS

BY
DR SABINA HAMEED

A thesis submitted in partial fulfillment of
the degree of Master of Science

Degree awarded: August 2017

2
TABLE OF CONTENTS

Authors and Affiliations.…………………………………………………… 3
Table Legend…………..…………………………………………………… 4
Figure Legend………………..………………………………..……………. 4
Abstract……………………………………………………………………… 8
1. Introduction….……………...……………………………………………. 10
2. Materials and Methods…………………………………………………… 12
3. Results…………..………..………………………………………………. 19
4. Discussion………………………………………………………………… 22
5. Conclusion………………………………………………………………… 28
6. Tables……………………………………………………………………… 29
7. Figures……………………..……………………………………………… 34
References……………………..………………………………………………. 47

3
Authors and affiliations

Sabina Hameed, BDS (Lond.), MFDS RCS (Eng.)
Graduate student, candidate for Master of Science in CBY
Division of Periodontology, Diagnostic Sciences and Dental Hygiene
Ostrow School of Dentistry, University of Southern California
925 W 34
th
St Room 4278 Los Angeles CA 90089

Homayoun H. Zadeh DDS PhD
Associate Professor
Division of Periodontology, Diagnostic Sciences and Dental Hygiene
Ostrow School of Dentistry, University of Southern California
925 W 34
th
St Room 4278 Los Angeles CA 90089

Correspondence
shameed@usc.edu

4
Table legend
Table 1. Clinical characteristics of study patients and sites.
Table 2. Mean pre-operative and post-operative measurements (in mm) for each root;
a) Reference line to sinus floor (M1 and M2)
b) Total vertical alveolar crest height (MBL1 and MBL2)
c) Reference line to crest of alveolar bone (R1 and R2)

Table 3. Height changes for individual roots.
Table 4. Pearson’s correlation results for the height changes after extraction of maxillary
molars for each root.
Table 5. Pearson’s correlation results for the root parameters and sinus floor change.
Table 6. Pairwise T- test results for periapical lesion (when present) and sinus floor
change.
Table 7. Pearson correlation results for sinus floor change and sinus membrane
thickening.
Table 8. Pearson’s correlation for the vertical height changes versus extraction healing
time and age of patient.
Figure legend
Fig. 1: Diagram illustrating radiographic landmarks used for measurements made on pre-
and post-extraction CBCT images.
1) Red lines indicate reference lines made using anatomic landmarks that were
unchanged in Pre- and Post- Operative CBCT images.
2) M1 - measured from reference (Red) line to sinus floor (Blue) line in Pre- Operative
CBCTs.
3) MBL1- measured from alveolar crest of the molar (Green) to sinus floor (Blue) line in
Pre- Operative CBCTs.
4) R1- measured from reference (Red) line to alveolar crest of the molar (Green) in Pre-
5
Operative CBCTs.
5) M2- measured from reference (Red) line to sinus floor (Purple) line in Post- Operative
CBCTs
6) MBL2- measured from alveolar crest of the molar (Yellow) to sinus floor (Purple) line
in Post- Operative CBCTs.
7) R2- measured from reference (Red) line to alveolar crest of the molar (Yellow) in
Post- Operative CBCTs.
8) SC (Sinus Change)= M1-M2
9) VHC (Vertical Height Change)=MBL1-MBL2
10) CHC (Crest Height Change) R2 - R1

Fig. 2: Anatomical parameters measured in pre-operative CBCT images.
d) Root Inclination- measured as the angle formed between the a line passing through
each root axis, with a horizontal line drawn through the inferior boarder of the
maxillary sinus

a) Root Width- measured at 2mm coronal from the radiographic apex of the root

a) Root apex-to-sinus floor distance- measured as the shortest distance from the
radiographic apex of each root to the maxillary sinus floor

d) Periapical lesion (when present)- was measured at its widest points (diameter)

e) Sinus membrane thickening (when detectable)- the sinus membrane width was
measured superior to each root apex.

Fig. 3: A representative CBCT series taken before and after extraction of a maxillary
molar, illustrating the measurements made according to the anatomic landmarks
designated in Figure 1. Thick yellow vertical line represents long axis of tooth root.

Fig. 4: Reasons for extraction of the teeth in the study.
6
Fig. 5: The total vertical height of the alveolar bone measured for individual roots before
and after extraction. Each point designates the value for the root of an individual tooth.
Horizontal lines denote mean values. Purple box denotes total vertical height of < 10mm.
Fig. 6: The changes to total vertical height, alveolar crest height and sinus floor location
measured for individual roots, when comparing the values before and after extraction are
shown. Each point designates the value for the root of an individual tooth. Horizontal
black lines designate mean and orange lines denote median.
Fig. 7: The cumulative percentage of sites showing the total vertical height change (mm)
detected after extraction of maxillary molars for individual roots within the population
analyzed.
Fig. 8: The cumulative percentage of sites showing the alveolar crest height change (mm)
detected after extraction of maxillary molars for individual roots within the population
analyzed.
Fig. 9: The cumulative percentage of sites showing the sinus floor change (mm) detected
after extraction of maxillary molars for individual roots within the population analyzed.
Fig. 10: A scatter plot showing the relationship between sinus floor change (mm) and
alveolar crest height change (mm) after extraction of maxillary molars for individual
roots.
Fig. 11: A scatter plot showing the relationship between sinus floor change (mm) after
extraction of maxillary molars and the inclination of each root to the sinus floor.
Fig. 12: A scatter plot showing the relationship between sinus floor change (mm) after
extraction of maxillary molars and the width of each root within 2mm of the apex (mm)
Fig. 13: A scatter plot showing the relationship between sinus floor change (mm) after
extraction of maxillary molars and the distance of each root apex to the sinus floor (mm).
Fig. 14. A scatter plot showing the relationship between sinus floor change (mm) after
extraction of maxillary molars and the diameter of periapical lesions (when present).
7
Fig. 15. A bar chart showing the relationship between mean sinus floor change (mm)
after extraction of maxillary molars and the presence or absence periapical lesions
Fig. 16. A scatter plot showing the relationship between sinus floor change (mm) after
extraction of maxillary molars and the thickness of the maxillary sinus membrane (when
detectable).

Fig. 17. A scatter plot showing the relationship between healing time (months) after
extraction of maxillary molars and sinus floor change (mm).

Fig. 18. A scatter plot showing the relationship between healing time (months) after
extraction of maxillary molars and alveolar crest height change (mm).

Fig. 19. A scatter plot showing the relationship between age (years) of patient and sinus
floor change (mm) after the extraction of maxillary molars.

Fig. 20. A scatter plot showing the relationship between age (years) of patient and
alveolar crest height change (mm) after the extraction of maxillary molars

8

Abstract
Objective:
Maxillary sinus pneumatization has been proposed to occur after maxillary tooth
extractions, whereas post-extraction dimensional changes in the alveolar crest have been
extensively investigated. To the best of our knowledge sinus floor and alveolar crest
height changes before and after maxillary molar extractions in the same site using CBCT
imaging modality has not been studied. Therefore, the aim of this retrospective study
was to investigate post-extraction spatial and dimensional changes in the maxillary sinus
floor and alveolar crest for non-augmented sites.

Materials and Methods:
23 pre- and post-operative CBCT images of 23 individuals who had maxillary molar
tooth extraction were analyzed using Simplant 17.0 software. Pre- and post-operative
CBCT images were oriented and aligned by utilizing coincident reference lines, and
superimposed. Linear measurements were made for mesiobuccal (MB), distobuccal (DB)
and palatal (P) roots for the height of alveolar crest, reference line to the maxillary sinus
floor, and reference line to alveolar crest. As a result, changes in the total vertical height
of the alveolar crest, in the location of the alveolar crest, and changes to the maxillary
sinus floor were obtained. Root anatomical factors including root inclination, root width
at 2mm from the radiographic apex, inter-radicular distance, periapical lesion diameter
and sinus membrane thickening were also investigated in relation to post-extraction sinus
floor change. Statistical analysis was done using SPSS software. Paired-sample t-tests,
independent sample t-tests and Pearson correlation were used. Results were reported as
means and standard deviations. Significance was sought at the p = 0.01 level.
Results:
The results revealed that there was a significant difference between the pre-extraction and
post-extraction values for the sinus floor level, alveolar crest level, and the total vertical
height of the alveolar crest. However, when the changes from pre- extraction to post
extraction were calculated, it was found that the mean for all three roots for the Vertical
9
Height Change (VHC) of the alveolar crest was 3.42 + 2.40 mm. This was largely made
up by the Crest Height Change (CHC) having a mean for all three roots of 3.07 + 2.53,
whereas the mean Sinus floor Change (SC) was only 0.47 + 0.32 mm. No statistically
significant correlation was found between the root anatomical factors and sinus floor
change. No statistically significant correlation was found between sinus floor change and
vertical alveolar crest height change or between alveolar crest height change and sinus
floor change for MB, DB and P roots at the p = 0.01 level. There was however,
significant correlation between CHC and VHC for each root (p = 0.00).
Conclusions: The results of this study challenge the commonly held concept that
substantial maxillary sinus floor changes occur after the extraction of maxillary molars.
Within the limitations of our study, it was found that only minimal sinus floor change
was seen, and that root anatomical factors did not seem to significantly effect this sinus
floor change. However, extensive crest height changes were seen and this is in agreement
with previous studies. Furthermore, no correlation was found between sinus floor change
and alveolar crest height change. Further research including animal, as well as
prospective clinical studies are needed to confirm these observations.

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1. Introduction

Physiological pneumatization is a normal process that leads to the enlargement of the
paranasal air spaces into the bony skull [1], [2]. The maxillary sinus is the first paranasal
sinus to develop at 10 days in utero, and continues to grow throughout infancy and
adolescence [3], [4]. There are three spurts of growth: from birth until 2 years, then from
7.5 years to 10 years and from 10 to 12 years. Thereafter there is a slower steady growth
until the age of 20 years old [5]. This process usually stops at the time of the completion
of the eruption of the third molars, at which time the floor of the maxillary sinus reaches
approximately 5mm inferior to the nasal floor [6], [7], [8], [9].

The etiology of sinus pneumatization is poorly understood, and has been linked to factors
such as growth hormones [10], pneumatization drive of the nasal mucous membrane [11] ,
bone density [10], craniofacial configuration [12], genetics [1], sinus air pressure [13],
[14], [15] and sinus surgery [16], and pathology. Currently, there is a paucity of evidence
on the occurrence of post-physiologic sinus pneumatization, that is the pneumatization
that occurs after the growth period. Furthermore, the relationship between the extraction
of maxillary molars and sinus pneumatization is even less clear. There are several
hypotheses relating to this, one such hypothesis is the ‘Fourth expansion phenomenon of
the maxillary sinus’ [7]. This has been explained as a type of disuse atrophy in which the
loss of a posterior maxillary tooth causes a decrease in functional forces transmitted to
the bone, leading to bone resorption and an increase in volume of the maxillary sinus at
the expense of the alveolar ridge [7], [17], [18] hypothesized that maxillary sinus
pneumatization is due to increased osteoclastic activity of the cortical walls of the sinus
and the layers of osteoid beneath it.
There have been only a few studies on maxillary sinus pneumatization after extractions.
Some have found there to be an increase in size of the sinus after extraction [19], [17],
[20], [21], [15] whilst others have found there to be no change [22]. Rosen and Sarnat
[19] reported increased sinus volume six to twelve months post-extraction of maxillary
teeth in dogs. Ariji et al [22] investigated maxillary sinus volumetric changes in relation
11
age and edentulism with CT scanning. They found no difference in edentulous and
dentate sites in maxillary molars.

Conventional panoramic radiography has many limitations with regards to accurate
identification of structures such as the maxillary sinus, and this leads to inaccuracy of
measurements. The main limitations include superimposition of the other paranasal
sinuses and skeletal structures, low resolution, distortion, vertical and horizontal
magnification and lack of cross-sectional information, [22] [23], [24]. In contrast, Cone-
Beam Computed Tomography (CBCT), which provides multi-planar views with a
uniform and low magnification [24] has the advantage of plainly demonstrating the
components of the maxillary sinus and can be used to overcome the limitations of
panoramic radiography. However, the number of studies using this imaging modality is
also scarce.
Post-extraction crestal alveolar bone changes has been well documented in the literature.
Studies in the canine model have demonstrated that there is marked dimensional changes
of the alveolar ridge in the first 2–3 months post-extraction, with the changes being more
pronounced on the buccal plate [25] Additionally, there is horizontal, as well as, vertical
bone loss. Schropp et al[26] concluded that there is substantial horizontal width loss and
this accounts for up to 50% of the original alveolar ridge width within the first 12
months. Two thirds of the reduction takes place within the first three months. Hammerle
and Araujo [27], have shown that the alveolar ridge undergoes a mean horizontal
reduction in width of 3.8 mm and a mean vertical reduction in height of 1.24 mm within
6 months after tooth extraction following the modeling /remodeling phases. Human re-
entry studies have also shown a marked horizontal bone loss of 29-63% and vertical bone
loss of 11–22% after 6 months following tooth extraction. These studies demonstrated
rapid reductions in the first 3–6 months that was followed by a gradual reduction in
dimension thereafter ([28]. CBCT analysis of alveolar bone changes in clinical studies
[29] and in the primate model [30] have investigated this further. These studies have
shown that the volumetric changes in fact occur at the most crestal 6mm of the alveolar
bone, whereas the zone 6-9mm apical to the alveolar crest is stable. Post-extraction
12
changes in the basal bone of maxillary molars as well as the alterations in the position of
the maxillary sinus floor, however, have not been fully investigated. To that end, the aim
of this retrospective study was to compare the relative position of the maxillary sinus
floor and alveolar crest pre- and post-extraction in maxillary molars in the same site using
CBCT imaging . The magnitude of sinus pneumatization through changes in the sinus
floor, as well as the vertical dimensional changes in the alveolar crest, from pre- to post
extraction in the posterior maxilla was investigated. Additionally the relationship
between sinus floor change and pre-extraction risk factors such as root inclination, root
width, proximity of the root to the sinus floor and the presence of pathology such as
periapical lesions or sinus membrane thickening was also investigated.
The null hypotheses were as follows:
Null Hypothesis 1: Following extraction of maxillary molars, there are no significant
changes to the maxillary sinus floor position.
Null Hypothesis 2: Post extraction maxillary sinus floor change is not related to pre-
operative root anatomical parameters such as root inclination, root width, root apex to
sinus distance, presence of periapical lesions, and thickening of the sinus membrane.
Null Hypothesis 3: Post-extraction sinus floor changes are not correlated with alveolar
height changes.

2. Materials and Methods
Patients. The study protocol was approved by the Institutional Review Board (IRB) of
the University of Southern California, allowing access to patients’ clinical records and
CBCT scans for the purpose of this study.
All patients had been referred for CBCT scans for diagnosis and treatment planning,
which included dental implants, maxillofacial surgery, orthodontics, endodontics, oral
pathology. No patient had been primarily referred for a CT scan of the maxillary sinus
area because of sinus symptoms or suspected diseases. Gender, age and indication for the
13
exam were recorded.
Screening and inclusion/exclusion criteria
5000 patients in the USC Dental electronic records system (Axium) from March 2009 to
December 2016 were screened for those having had extractions of maxillary molars
without bone grafting and having pre- and post-extraction CBCT scans. After inclusion
and exclusion criteria were met (see below), twenty-three patients and twenty-three
CBCT scans were identified. DICOM files of these CBCT scans were obtained from the
Redmond Imaging facility (USC School of Dentistry) and uploaded into Simplant Pro
16.0 software (Dentsply Implants, Waldham, MA, USA) for analysis.
Inclusion criteria
Adult patients aged 18-90 years old, who had undergone maxillary molar extraction
without any ridge preservation or augmentation procedures were selected. The
availability of pre and post-extraction CBCT scans was another exclusion criterion;.
Exclusion criteria
Third molar extraction
History of sinus or other dento-alveolar surgery at the extraction site
Ridge preservation or augmentation procedure

Methods
Prior to any measurements being done, patients’ pre- and post extraction CBCT scans
were meticulously and arduously matched. This was done to ensure that the same CBCT
was used for pre- and post-extraction linear measurements, therefore allowing for
accuracy in measurements. The Simplant software did not allow for the superimposition
of pre- and post operative images. Therefore at each of the steps below, the pre- and
post- operative images were screenshot on the computer, put into a Keynote presentation
and manually superimposed.
14
The following steps were taken for matching pre- and post- operative CBCT scans (Fig
1):
a) CBCT orientation:
Pre- operative CBCT scans were orientated in the coronal, axial, sagittal and frontal
views so that the Frankfort and axial planes were horizontal and the frontal view was
symmetrical. Post- Operative CBCTs were then orientated to match the Pre-op.
b) Creation of a Panoramic curve:
A panoramic curve was drawn passing through the central fossa of the teeth at the most
coronal level of the alveolar crest for the pre- operative CBCT. This was then done for
the post-operative CBCT ensuring that the curves were identical in appearance. Once the
panoramic curve was drawn, a panoramic view was obtained.
Pre- and post-operative panoramic views were then screenshot and copied into a keynote
presentation and superimposed in order to check that the images were the same. If
discrepancies were found between the two images, the post-operative CBCT was re-
orientated and a new panoramic curve was drawn until the images could be
superimposed.
c) Co-incident reference line (Red line- see Figs. 1, 2 and 3):
A reproducible and co-incident reference line was drawn on both the pre- and post-
operative CBCT scans in the panoramic view. The reference line was drawn through
fixed references such as multiple cusp tips of teeth.
d) Referencing of the extracted maxillary molar tooth:
This was done in order to accurately locate the extracted tooth site on the post-Operative
CBCT image.
On the pre- operative CBCT image (Panoramic view), the width of the tooth to be
extracted was measured from a fixed landmark such contact points. Each root
(Mesiobuccal, Distobuccal, and Palatal root) was first identified on the axial view, and
15
then on the coronal view. Once identified, a vertical line was drawn (on the Panoramic
view) bisecting the root apex and the reference line. The distance from the fixed width-
reference points and the long axis of each root was noted. A second point of reference
(per root) was done on the coronal view. This involved drawing a line bisecting the long
axis of the root (from the root apex) and measuring the distance from the sagittal
midline.
Screenshot images of each root in both the sagittal and panoramic view were taken and
put into Keynote for later superimposition.
On the post-operative CBCT image the site of the extracted tooth was identified by
reproducing both the pre-operative panoramic and coronal view reference measurements
(as described above). Screenshot images were taken of the post-operative root sites (MB,
DB and P) and superimposed with the pre-operative sites. The images were checked for
matching. If the two images were not exactly the same, the post op CBCT coronal slice
was adjusted until the same pre- and post-operative cut was identified.

Measurements:
In order to quantify the post operative maxillary sinus floor and bone changes, and
identify the effect of root anatomy and pathology on sinus pneumatization, both sinus and
bone crest, and root anatomical parameters were measured.
Root Anatomical Parameters (See Fig 2):
The following were measured on pre-operative CBCT scan images in the coronal view
per root:
a) Root Inclination:
This was measured as the angle formed between two bisecting lines. The first line was
drawn through the apex and down the long axis of the root, the second line was a
horizontal line drawn through the lowest bony point of maxillary sinus floor (pre- op
sinus floor line- see Fig 3).
16
b) Root width:
This was measured as the width in mm of the root at 2mm coronal from the radiographic
apex
c) Root apex-to-sinus floor distance:
This was measured as the shortest distance in mm from the radiographic apex to the
lowest border of the cortical boundary of the sinus floor.
d) Periapical area diameter:
If a peri-apical radiolucency was detected, its diameter (widest part) was measured in
mm.
e) Sinus membrane thickening:
The width of the sinus membrane was measured from the bony floor of the sinus
membrane. This was measured in millimeters in the mid root apex position.
f) Mean inter-radicular distance:
This was measured in the axial view by locating the first point of the apices of each root
(MB, DB and P) and then drawing a line between each root. The sum total of these
measurements was then divided by three in order to get the mean.
Sinus and bone crest parameters (See Fig 3) :
In order to quantify the changes in the pre- and post- operative bone crest and sinus floor,
three horizontal lines were drawn in the cross-sectional view per root on both the pre-
operative and post-operative CBCT scans. The distance between these lines were then
measured, and the difference between these measurements pre- and post operatively were
calculated.
Horizontal Lines on Pre- Operative CBCT Scans:
The following lines were drawn for each root on the pre- operative CBCT scans:
17
Co-incident reference (red) line – see above.
Pre- operative marginal bone level (green line)- This horizontal line was drawn at the
most coronal point of the alveolar bone level corresponding to the long axis of the root.
Pre- operative maxillary sinus floor level (blue line)- This line was drawn at the most
coronal point of the bony maxillary sinus floor level corresponding to the long axis of the
root.
Horizontal lines on Post- Operative CBCT Scans (Figure 3):
Co-incident reference (red) line – see above.
Post- operative marginal bone level (dark green line)- This horizontal line was drawn at
the most coronal point of the alveolar bone level corresponding to the long axis of the
root.
Post- operative sinus floor level (dark blue line)- This line was drawn at the most coronal
point of the bony maxillary sinus floor level corresponding to the long axis of the root.
Distances measured on Pre- Operative CBCT Scans:
M1 - measured from pre operative reference (red) line to pre- operative sinus floor (blue)
line.
MBL1- measured from pre- operative marginal bone level (green) line to pre- operative
sinus floor (blue) line.
R1- measured from reference (red) to pre-operative marginal bone level (green) line

Distances measured on Post- Operative CBCT Scans:
M2- measured from post-operative reference (red) line to post -op sinus floor (dark blue)
line.
18
MBL2- measured from post- operative marginal bone level (yellow) line to post- op
sinus floor (dark blue) line.
R2- measured from pre- operative reference (red) line to post- operative marginal bone
level (dark green) line

Calculated Sinus floor and Bone Height changes:
The following changes were calculated from the pre- and post-operative distances (see
above):
SC (Sinus Change)- calculated by subtracting M2 from M1; SC = M1-M2
This measurement (in mm) quantifies the change in the position of the sinus floor from
pre- to post-extraction.
CHC (Crest Height Change)- calculated by subtracting R2 from R1; CHC= R2 - R1
This measurement (in mm) quantifies the change in the position of the alveolar crest from
Pre- to Post-extraction.

Statistical analysis
Descriptive statistical analysis was carried out using SPSS (Version 24, IBM
Corporation, New York, USA). The pre-extraction and post-extraction measurements
were compared using paired-sample t-tests and independent sample t-tests were utilized
for intergroup comparisons. Pearson correlation was used to assess the association
between the parameters and the outcome measures. Results were reported as means and
standard deviations. Significance was sought at the p = 0.01 level.

19
3. Results
Table 1 shows the clinical characteristics of patients and their teeth included in this
study. A total of 23 patients met the inclusion criteria and exclusion criteria of this study.
Each patient contributed to only one tooth, which included first (n=16) and second (n=7)
maxillary molar teeth. The mean healing time from extraction of the maxillary molar to
the time of CBCT imaging was 11.7 + 14.9 months, with the range being from 2 to 60
months. The mean age was 70.4 years old + 11.4 years, and the age range 48-87 years
old. There were 10 male and 13 female patients. No patients were current smokers, and
only 3 had a previous history of smoking. Patients had various medical co-morbidities; 4
patients had hypothyroidism, 11 had hypertension, 2 had penicillin allergy, 2 had
osteoarthritis, 3 had diabetes mellitus and 1 patient was taking oral bisphosphonates. The
reasons for extraction of the maxillary molar teeth in the study (Table 1 and Fig. 4.) were
caries (7/23), tooth/ or root fracture (4/23), Periodontal disease (8/23), periodontal -
endodontic lesions (1/23), mal-positioning (2/23) and unspecified (1/23).
With regards to the bone parameters investigated, Fig 5 and Table 2 show that for all
subjects for all roots the total vertical height (distance from the alveolar crest to the sinus
floor) was greater pre-extraction than post-extraction. The mean total vertical height pre-
extraction (MBL1) per root was 18.1mm + 8.06, 14.2 mm + 4.33 and 13.3 mm + 6.11 for
the MB, DB and P roots respectively. Post-extraction total vertical height (MBL2) was
14.2 mm + 8.25, 10.7 mm + 5.5 and 10.6 mm + 6.05 for the MB, DB and P roots
respectively. The mean pre-operative total vertical height of the three roots was 15.2
mm + 5.0, and the mean post-operative total vertical height was 11.8 + 5.2. Pairwise
comparisons of pre- and post-operative alveolar vertical height showed significant
differences between those values (p= 0.00) for each of the roots. Fig 5 also shows that
when compared to pre-extraction values, a greater number of teeth had post extraction
total vertical height of 10mm or less. Furthermore, Table 2 shows that there was also a
significant difference between the pre-extraction and post-extraction values for the
alveolar crest level, and the total vertical height of the alveolar crest (p= 0.00).
20
Three vertical height changes were calculated; Vertical Height Change, Crest Height
Change (CHC) and the Sinus floor Change (SC), Table 3 and Fig 6. Illustrate these
changes for each patient and each root.
The Vertical Height Change (VHC), which is the change in the total vertical height from
pre- extraction to post-extraction, had a mean of 3.9 mm + 3.11, 3.5mm + 3.48 and
2.8mm + 2.19 for the MB, DB and P roots respectively. The mean for all three roots was
3.42 mm + 2.40. The minimum VHC per root was 0.10 mm, 0.15 mm, and 0.01 mm for
MB, DB and P roots, respectively. Whereas the maximum VHC was 11.27 mm, 13.55
mm and 6.73 mm for MB, DB and P roots, respectively. The median VHC was 2.73 mm,
2.87 mm and 2.50 mm for MB, DB and P roots, respectively.
The second height change was the Crest Height Change (CHC), which is the change in
the crestal level of the alveolar bone (R2 subtracted from R1). The mean crest change
was 3.31 mm + 3.40, 3.49 mm + 3.74 and 2.39 mm + 2.14 for the MB, DB and P roots
respectively. The mean for all three roots was 3.07 mm + 2.53. The minimum CHC per
root was 0.05 mm, 0.08 mm, and 0.01 mm for MB, DB and P roots, respectively.
Whereas the maximum CHC was 11.96 mm, 13.52 mm and 6.92 mm for MB, DB and P
roots, respectively. The median CHC was 2.13 mm, 2.33mm and 1.68 mm for MB, DB
and P roots, respectively.
The third change is the Sinus floor Change (SC), which is the change in the level of the
floor of the maxillary sinus from pre- to post extraction (M2 subtracted from M1). The
results show that the mean sinus change was 0.67 mm + 0.52, 0.37 mm + 0.42 and 0.38
mm + 0.47 for the MB, DB and P roots respectively. The mean for all three roots was
0.47 mm + 0. 32. The minimum SC per root was 0.04 mm, 0.00 mm, and 0.00 mm for
MB, DB and P roots, respectively. Whereas the maximum SC was 1.62 mm, 1.53 mm
and 1.74 mm for MB, DB and P roots, respectively. The median SC was 0.68 mm, 0.29
mm and 0.16 mm for MB, DB and P roots, respectively.
Furthermore, it can be seen (table 3) that the Crest Height Change contributed to 89.76 %
of the total Vertical Height Change, whilst Sinus Change accounted for only 13.74% of
the post extraction alveolar bone remodeling.
21
Fig. 7 through 9 are scatter plots showing the cumulative percentage of sites in relation to
Total Vertical Height change, Crest Height change and Sinus Height change respectively.
It can be seen (Fig 7) that with regards to cumulative percentage of sites in relation to
vertical height change 50% of sites had a total vertical height change of 2.7mm, 20% of
the sites had a total vertical height change of 1mm, whereas 80% had a total vertical
height change of 5.2mm. When this is compared to the Crest Height Change (Fig 8), it
can be seen that 50% of sites had a crest height change of 2.05 mm, 20% of the sites had
a 0.25 mm change, whereas 80% had a crest height change of 4.3 mm. When looking at
Sinus Floor Change (Fig 9), 50% of sites had a sinus floor change of 0.38mm, 20% of the
sites had a 0.09 mm change, whereas 80% had a crest height change of 0.8 mm.
No statistically significant correlations were found between sinus floor change and crest
height change for each of the MB, DB or P roots (Fig 10 and table 4) at the p = 0.01
level. Nor was it found for sinus floor change and vertical height change. However, a
statistically significant correlation at the p = 0.01 level was found between vertical height
change and crest height change R= 0.98, 0.91 and 0.89 for MB, DB and P roots
respectively per root
The root anatomical parameters investigated included those factor that were hypothesized
to influence crestal and sinus floor changes; i.e. root inclination, root width, root apex-to-
sinus distance, periapical lesion diameter, sinus membrane thickening and inter-radicular
distance. Table 5-8 and Figs. 11-14, and Fig.16 show that for each root neither root
inclination, nor root width, root apex to sinus distance, sinus membrane thickening (when
present) and inter-radicular distance had any significant correlation with sinus floor
change. Pairwise t tests (Table 6) showed that at the 0.01 significance level, there was no
difference between periapical lesion (when present) and sinus floor change for MB and P
roots. There was however, significant difference between periapical lesion (when present)
between DB root and sinus floor change. This is illustrated in Figs 14 and 15.
Healing time from tooth extraction to CBCT imaging date (months) and age of the patient
(years) were also not found to be correlated (at the p= 0.01 level) with vertical height
change, sinus floor change or crest height change for each of the 3 roots (Table 8,
Figs.17-20)
22
4. Discussion
Examination of changes to the maxillary sinus floor and alveolar crest are a significant
area of investigation due to the major impact these can have on the therapeutic choices
for our patients. To the best of our knowledge, this is the first report that compare both
the sinus floor and alveolar crest height changes pre- and post-extraction of maxillary
molars in the same site using CBCT imaging modality.

The results of our study have shown that when comparing the relative position of the
maxillary sinus floor before and after tooth extraction, there was a statistically significant
change. However, this change was very small (0.47mm + 0.32). This change in sinus
floor location may be due to a number of factors. There may actually be a true, but
minimal change in the location of the sinus floor as a biologic response to tooth
extraction. Alternatively the change detected may simply be due to a change in bone
density following tooth extraction, which may then affect the detection of the sinus floor.
The small magnitude of this post extraction sinus floor change in the present study is in
contrast to previous studies. For example, Rosen and Sarnat [19], reported that the sinus
volume was larger 6 to 12 months post extraction in 7 of the 10 dogs in their study in
which unilateral posterior maxillary teeth were removed. However, this is an animal
study, and the results may not be applicable to humans. The anatomy of teeth in dogs is
very different to human teeth. Dog teeth tend to be more difficult to extract, so there is a
possibility that greater trauma may have been introduced whilst extracting these teeth, in
turn causing possible oral-antral communications. This could have caused changes to the
maxillary sinus volume. Harorh and Bocutoglu

[20], looked at the height and width of
maxillary sinuses of dentate and edentulous subjects on Water’s radiographs. They
found a significantly greater average sinus height in the edentulous sample. Ohba et al

[21], found the maxillary sinus floors of edentulous subjects to be inferiorly positioned
compared with those of dentate subjects. However, in both of these studies the same site
pre- and post extraction was not investigated. Wehrbein and Diedrich [17], found that
after extraction and orthodontic space closure, maxillary sinus pneumatization occurred if
pneumatization was present prior to treatment. They also found that the extraction of
23
molars exhibited a greater risk to sinus pneumatization the extraction of premolars. This
study involved superimposition of tracings from panoramic radiographs. Sharan [15],
carried out a retrospective analysis of panoramic radiographs on edentulous versus
dentate, and pre and post extraction of maxillary molar teeth. They found that sinus
pneumatization occurred in the range of 1.83 to 2.18 mm. However, this study has a
major limitation in that the pre- and post extraction panoramic radiographs were not
superimposed, instead reference measurements were done in order to measure pre and
post extraction changes. Furthermore, the measurements were done on panoramic
radiographs, which have inherent superimposition of anatomical structures and
magnification. This means that the maxillary sinus cannot be accurately identified, and
this could lead to inaccuracy of the measurements. Ariji et al [22], is the only study that
investigated maxillary sinus volume changes with age and with extraction of maxillary
molars using CT scans. They found that there was an increase in the total volume of the
maxillary sinus until the age of 20, thereafter there was a decrease. They also found that
there was no correlation with maxillary volume changes and the presence or absence of
posterior maxillary teeth. However, this study looked at volume of the maxillary sinus
and not specifically the changes to the sinus floor.

The reason as to why maxillary sinus floor changes (sinus pneumatization) may occur
post extraction is unclear. There are several theories such as the ‘Fourth expansion
phenomenon of the maxillary sinus’. Misch [7]. This has been explained as a type of
disuse atrophy in which the loss of a posterior maxillary tooth causes a decrease in
functional forces transmitted to the bone, leading to bone resorption and an increase in
volume of the maxillary sinus at the expense of the alveolar ridge [7], [17], [18],
Wehrbein H and Diedrich P [17], explained this phenomenon to be due to accelerated
osteoclastic activity of the cortical walls of the sinus and the layers of osteoid inferior to
it. There is no evidence to confirm that the decreased functional forces on the bone is
transmitted to the sinus, or that the resorption of the alveolar bone crest is related any
changes occurring in the maxillary sinus floor. Our study in fact did not find any
correlation between sinus floor change and change in total alveolar crest height post
24
extraction. Our findings are also in contrast to the study studies by Nimigean et al [12],
who found there to be an inverse relation between sinus pneumatization and remaining
alveolar bone. Their study inferred that the antral floor depends upon the dental scaffold
as the main factor during development, and that this transforms in relation with the
normal/pathological status of the dento-periodontal apparatus. They concluded that post
extraction alveolar crestal bone is lost as a result of the inferior expansion of the sinus
after teeth loss. Again, there is no evidence that this occurs.

With regards to root anatomical factors, we found that none were correlated with sinus
change. It has been found that the inclination of roots affects the crestal bone resorption
post extraction [31]. However this doesn’t seem to be the case for sinus floor change. It
could also be assumed that the wider the diameter of a root, the more influence it has on
sinus, however, this was not found to be true. It can also be proposed that the closer the
root apex is to the sinus floor the greater the degree of sinus floor change due to the
greater zone of influence. However, our study did not confirm this. Similarly sinus
membrane thickening and periapical lesions when present did not seem to influence the
amount of sinus floor change. The only significant correlation was found between the
presence of a periapical lesion on the DB root and the DB sinus change. This maybe due
to ease of detection of this root and sinus floor on CBCT images.
With regards to crest vertical height change, we found that there was substantial crestal
resorption at 6 months (3.6 mm). This is in line with previous studies [27], that have
shown that the alveolar ridge undergoes a mean horizontal reduction in width of 3.8 mm
and a mean vertical reduction in height of 1.24 mm within 6 months after tooth extraction
following the modeling /remodeling phases. Human re-entry studies have also shown a
marked horizontal bone loss of 29-63% and vertical bone loss of 11–22% after 6 months
following tooth extraction. These studies demonstrated rapid reductions in the first 3–6
months that was followed by a gradual reduction in dimension thereafter [28].
There is a plethora of studies regarding alveolar bone remodeling/ modeling of the crestal
bone post extraction. We know that the alveolar process is a tooth-dependent tissue and
its shape and volume is influenced by tooth form, as well as the direction of eruption of
25
the tooth and the presence or absence of teeth. Following teeth extraction the
periodontium undergoes atrophy [26], with the complete loss of attachment apparatus
including the periodontal ligament with its Sharpey’s fiber insertion in both cementum
and bone [25]. The anatomical variation within the alveolar socket (thickness and
composition) has also been shown to contribute to the magnitude of resorption [25]. The
buccal plate is solely consisting of bundle bone and the amount of alveolar ridge volume
reduction has been shown to be correlated with the thickness of the buccal plates.
Chappuis et al. [32], showed that the pre-extraction thickness of the buccal plate was the
most important determining factor in the horizontal dimension loss. However, the sinus
membrane and the basal bone surrounding it, does not have a periodontal ligament or
bundle bone. So it is reasonable to assume that the mechanisms for sinus pneumatization
if and when it occurs would be different from the crestal bone resorption, and that sinus
pneumatization occurs independent of crestal resorption, owing to the different structures
and functions.

In our study, maxillary molars that had 6 months or less post extraction healing had a
mean (for 3 roots) sinus change of 0.47mm. Previous studies have reported that the
complete healing of the tooth socket post-extraction varies amongst individuals and is
thought to be due to the biologic variations in the population, alveolar socket size and the
extent of surgical trauma induced during the extraction procedure [31]. Radiographic
bone fill of the socket occurs between 3 and 6 months post-extraction with most of the
dimensional changes occurring during the first 3 months and remodeling continuing for
up to 1 year post extraction [26]. Complete healing of the tooth socket post-extraction
varies amongst individuals and is thought to be due to the biologic differences among
individuals, alveolar socket size and the extent of surgical trauma induced during the
extraction procedure [31].
There are several limitations to the current investigation. The first is that the sample size
was small, with only 23 teeth and patients with pre- and post- extraction CBCT images.
It is however, worthy to note that this sample size was found from 5000 patients records
that were screened. The reason for this small sample size is due to the fact that CBCT’s
are not taken routinely pre and post extractions in an attempt to reduce the exposure of
26
patients to radiation as much as practically possible. It is common for other lesser
radiation dose investigations such as intraoral radiographs to be taken instead. Therefore
the 23 patient CBCT images were those who by chance had a pre-operative and post-
operative CBCT image taken, usually due to treatment planning for implants over a
period of time. A multicenter study could help increase the sample size and therefore the
power of the study.
CBCT measurement accuracy could also affect the results. In a study by Marmulla et al
[33], mathematical distance calculations were done in order to test the geometrical
accuracy of CBCT imaging. They found a mean image deviation of 0.13 mm, which was
below the voxel size of the image. Lascala et al [34]. found that that the real
measurements on human skulls were always greater than those done on CBCTs.
However, this underestimation by CBCT imaging was not statistically significant.
Mischkowski et al [35] found that the average absolute percentage error (APE) for CBCT
imaging on the Galileos CBCT unit is 0.98%. However, with this said, the CBCT
accuracy error could actually negate the very minimal sinus floor changes seen in this
study. This could mean that there may in fact no change in the sinus floor from pre- to
post- extraction of maxillary molars.
Human errors in CBCT image orientation, superimposition, and image detection could
also affect the accuracy of the results. However, previous studies such as that by Pinsky
et al [36] looked at intra-examiner reliability in CBCT linear measurements. They found
that this varied from 0.75 to 0.99 % with a mean of 0.96%, with examiners with no
previous training in CBCT imaging analysis. They suggested that CBCT linear
measurement accuracy is not examiner dependent. In this study one examiner did all 23
CBCT image measurements. Each measurement was repeated 3 times in order to ensure
accuracy of measurements.
Error in acquisition of CBCT images such as change in position of the patient could also
affect the results. A study by Sheiki et al [37] found there to be a significant difference
between physical measurements and radiographic measurements in ideal, rotation, tilt,
and extension positions, however, the differences were not clinically significant.
27
In this study, we did not have any cases in which the roots of the teeth were protruding
into the maxillary sinus, where there was any documented trauma during extraction or
oral-antral communication post-extraction. We therefore do not know that effect of these
factors on post-extraction maxillary sinus floor alteration.
As a result of our study, we reject the first null hypothesis, and accept the second and
third null hypotheses. We found there to be a significant change to the maxillary sinus
floor position post extraction of maxillary molars. However, as the magnitude of this is
very small it may not be clinically significant. We also found that post extraction
maxillary sinus floor change was not related to pre- operative root anatomical parameters
such as root inclination, root width, root apex to sinus distance, presence of periapical
lesions, and thickening of the sinus membrane. Additionally, we found that post-
extraction sinus floor changes are not correlated with alveolar height changes.
The results of our study may have far reaching implications. Implant placement in the
maxillary molar area is limited by the floor of the maxillary sinus, and by the total
vertical height of the alveolar bone. Where the floor of the maxillary sinus is in a more
inferior position and there is insufficient alveolar bone height for implant placement, the
most common treatment is maxillary sinus augmentation. Therefore, information about
the magnitude of sinus floor changes and the changes in the maxillary sinus floor level in
relation to the amount of residual alveolar bone post extraction is vital information
needed for the treating our patients. It may be that we need to put more focus on
maintaining the alveolar crest rather than carrying out sinus augmentation post extraction
of maxillary molars.

28
5. Conclusion
The results of this study challenge the commonly held concept that substantial maxillary
sinus pneumatization occurs following extraction of maxillary molars. Within the
limitations of our study, it was found that only minimal sinus floor change was seen, and
that root anatomical factors did not seem to significantly effect this sinus floor change.
However, extensive crest height changes were seen and this is in agreement with previous
studies. Further research including animal, as well as prospective clinical studies are
needed to confirm these observations.

29
6. Tables
Table 1
Parameter Value

Population
Subjects 23
Teeth 23
Mean age 70.4 + 11.4
Age range (years) 48 - 87
Male 10
Female 13
Sites
Max right second molar 5
Max right first molar 9
Max left first molar 7
Max left second molar 2
Mean healing time of extraction site (months) 11.7 + 14.9
Healing time range (months) 2 - 60
Reason for
extraction

Caries 7
Fracture 4
Periodontal disease 8
Periodontal- Endodontic 1
Supra-eruption 2
No data 1
Medical history
Current smokers 0
Never-smoker 20
History of smoking 3
Hypothyroidism 4
Hypertension 11
Penicillin allergy 2
Osteoarthritis 2
Diabetes mellitus 3
Oral bisphosphonate 1

30
Table 2:

a) Reference line
to Sinus floor

b) Vertical
alveolar crest
height

b) Reference line to
crest of alveolar bone

MB DB P
Mean
of 3
roots
MB DB P
Mean
of 3
roots
MB DB P
Mean
of 3
roots
Mean Pre-Op
(mm)
28.2
+ 8.2
25.0
+ 4.2
23.2
+ 6.4
25.5
+ 5.2
18.1
+ 8.1
14.2
+ 4.3
13.3
+ 6.1
15.2
+ 5.0
10.07
+ 2.5
10.58
+ 2.1
9.88
+ 2.3
11.4
+ 2.3
Mean Post-
Op (mm)
27.6
+ 8.1
24.5
+ 4.1
22.8
+ 6.4
25.1
+ 3.2
14.2
+ 8.3
10.7
+ 5.5
10.6
+ 6.5
11.8
+ 5.2
13.39
+ 3.7
14.12
+ 5.0
12.28
+ 2.7
12.1
+ 3.0
Paired
sample
T test
5.99 4.15 3.50

6.01 4.86 6.02

-4.67 -4.38 -5.38

Significance
p =
*0.00
p =
*0.00
p =
*0.00

p =
*0.00
p =
*0.00
p =
*0.00

p =
*0.00
p =
*0.00
p =
*0.00

Table 3:

HEIGHT CHANGES (mm)

VERTICAL HEIGHT CHANGE (VHC)
CREST HEIGHT CHANGE
(CHC)
SINUS FLOOR CHANGE (SC)
Root MB DB P
Mean
of 3
roots
MB DB P
Mean
of 3
roots
MB DB P
Mean
of 3
roots
Mean
3.9
+ 3.11
3.5
+ 3.48
2.8
+ 2.19
3.42
+ 2.40
3.31
+ 3.40
3.49
+ 3.74
2.39
+ 2.14
3.07
+ 2.53
0.67
+ 0.52
0.37
+ 0.42
0.38
+ 0.47
0.47
+ 0.32
Min.
0.10 0.15 0.01

0.05 0.08 0.01

0.04 0.00 0.00

Max.
11.27 13.55 6.73

11.96 13.52 6.92

1.62 1.53 1.74

Median
2.73 2.87 2.50

2.13 2.33 1.68

0.68 0.29 0.16

31
Table 4:
CORRELATION
(PEARSONS)
SINUS FLOOR CHANGE (SC) CREST HEIGHT CHANGE (CHC)

MB DB P MB DB P
CREST
HEIGHT
CHANGE
(CHC)

MB
R = - 0.26
p = 0.2
DB

R = - 0.43
p = 0.04
P

R = - 0.13
p = 0.6
VERTICAL
HEIGHT
CHANGE
(VHC)
MB
R = - 0.94
p = 0.7
R = 0.98
p = 0.00**
DB

R = - 0.34
p = 0.1
R = 0.91
p = 0.00**
P

R = - 0.01
p = 0.7
R = 0.89
p = 0.00**

32
Table 5:
PEARSON

SINUS FLOOR CHANGE (SC)
CORRELATION

MB DB P
Root Inclination
MB
R = - 0.21
p = 0.3
DB

R = - 0.30
p = 0.2
P

R = 0.22
p = 0.3
Root Width
MB
R = - 0.13
p = 0.6
DB

R = 0.56
p = 0.8
P

R = 0.24
p = 0.3
Root apex to sinus
distance (mm)
MB
R = - 0.18
p = 0.4
DB

R = 0.26
p = 0.2
P

R = - 0.16
p = 0.5
Mean Interradicular
distance
R = 0.31
p = 0.2
R = 0.23
p = 0.3
R = 0.16
p = 0.5

Table 6:

MB DB P
Perapical lesion
Yes
n = 5/23
No
n = 18/23
Yes
n = 1
No
n = 22
Yes
n = 3
No
n = 20
Sinus Floor
Change (mm)
0.73 +
0.5
0.42 + 0.4 1.5 0.32 + 0.3 0.49 + 0.7 0.36 + 0.5
Paired sample
T test (Sinus
change and
Periapical lesion)
1.19 -3.51 -0.44
Significance
p = 0.3 p = 0.0** p = 0.4
** significant at the 0.01 level
33

Table 7:
PEARSON

SINUS FLOOR CHANGE (SC)
CORRELATION

MB DB P
Sinus Membrane
Thickening
MB
R = - 0.133
p = 0.5
DB

R = - 0.12
p = 0.6
P

R = 0.39
p = 0.1

Table 8:
CORRELATION ( PEARSONS)
HEALING TIME
(MONTHS)
AGE (YEARS)
VERTICAL HEIGHT CHANGE
(VHC)

MB
R = - 0.17
p = 0.4
R = - 0.40
p = 0.7
DB
R = - 0.09
p = 0.7
R = - 0.11
p = 0.6
P
R = - 0.54
p = 0.8
R = - 0.10
p = 0.6
SINUS FLOOR CHANGE (SC)
MB
R = - 0.01
p = 1.0
R = 0.17
p = 0.4
DB
R = - 0.09
p = 0.2
R = -0.23
p = 0.3
P
R = - 0.37
p = 0.9
R = 0.19
p = 0.4
CREST HEIGHT CHANGE
(CHC)

MB
R = - 0.16
p = 0.5
R = - 0.37
p = 0.1
DB
R = - 0.12
p = 0.6
R = - 0.1
p = 0.8
P
R = - 0.14
p = 0.5
R = - 0.35
p = 0.1

34
7. Figures
Figure 1:

35
Figure 2:

Figure 3:

36
Figure 4:

Figure 5:

37

Figure 6:

38

Figure 7:

39
Figure 8:

40

Figure 9:

41
Figure 10:

Figure 11:
42
Figure 12:

43
Figure 13:

Figure 14:

44
Figure 15:

Figure 16:

45
Figure 17:

Figure 18:

46
Figure 19:
Figure 20:

47
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Abstract (if available)

Abstract Objective: Maxillary sinus pneumatization has been proposed to occur after maxillary tooth extractions, whereas post‐extraction dimensional changes in the alveolar crest have been extensively investigated. To the best of our knowledge sinus floor and alveolar crest height changes before and after maxillary molar extractions in the same site using CBCT imaging modality has not been studied. Therefore, the aim of this retrospective study was to investigate post‐extraction spatial and dimensional changes in the maxillary sinus floor and alveolar crest for non-augmented sites. ❧ Materials and Methods: 23 pre‐ and post‐operative CBCT images of 23 individuals who had maxillary molar tooth extraction were analyzed using Simplant 17.0 software. Pre‐ and post‐operative CBCT images were oriented and aligned by utilizing coincident reference lines, and superimposed. Linear measurements were made for mesiobuccal (MB), distobuccal (DB) and palatal (P) roots for the height of alveolar crest, reference line to the maxillary sinus floor, and reference line to alveolar crest. As a result, changes in the total vertical height of the alveolar crest, in the location of the alveolar crest, and changes to the maxillary sinus floor were obtained. Root anatomical factors including root inclination, root width at 2mm from the radiographic apex, inter‐radicular distance, periapical lesion diameter and sinus membrane thickening were also investigated in relation to post‐extraction sinus floor change. Statistical analysis was done using SPSS software. Paired-sample t‐tests, independent sample t‐tests and Pearson correlation were used. Results were reported as means and standard deviations. Significance was sought at the p = 0.01 level. ❧ Results: The results revealed that there was a significant difference between the pre‐extraction and post‐extraction values for the sinus floor level, alveolar crest level, and the total vertical height of the alveolar crest. However, when the changes from pre‐extraction to post‐extraction were calculated, it was found that the mean for all three roots for the Vertical Height Change (VHC) of the alveolar crest was 3.42 ± 2.40 mm. This was largely made up by the Crest Height Change (CHC) having a mean for all three roots of 3.07 ± 2.53, whereas the mean Sinus floor Change (SC) was only 0.47 ± 0.32 mm. No statistically significant correlation was found between the root anatomical factors and sinus floor change. No statistically significant correlation was found between sinus floor change and vertical alveolar crest height change or between alveolar crest height change and sinus floor change for MB, DB and P roots at the p = 0.01 level. There was however, significant correlation between CHC and VHC for each root (p = 0.00). ❧ Conclusions: The results of this study challenge the commonly held concept that substantial maxillary sinus floor changes occur after the extraction of maxillary molars. Within the limitations of our study, it was found that only minimal sinus floor change was seen, and that root anatomical factors did not seem to significantly effect this sinus floor change. However, extensive crest height changes were seen and this is in agreement with previous studies. Furthermore, no correlation was found between sinus floor change and alveolar crest height change. Further research including animal, as well as prospective clinical studies are needed to confirm these observations.

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Asset Metadata

Creator Hameed, Sabina (author)

Core Title Maxillary sinus floor and alveolar crest alterations following extraction of maxillary molars: a retrospective CBCT analysis

School School of Dentistry

Degree Master of Science

Degree Program Craniofacial Biology

Publication Date 06/30/2017

Defense Date 06/01/2017

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

Tag alveolar crest changes,CBCT analysis,extraction of maxillary molars,maxillary sinus,OAI-PMH Harvest,sinus floor changes post-extraction

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Zadeh, Homayoun (committee chair), Kar, Kian (committee member), Paine, Michael (committee member)

Creator Email sabina_hameed@hotmail.com,shameed@usc.edu

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c40-392085

Unique identifier UC11264382

Identifier etd-HameedSabi-5471.pdf (filename),usctheses-c40-392085 (legacy record id)

Legacy Identifier etd-HameedSabi-5471.pdf

Dmrecord 392085

Document Type Thesis

Rights Hameed, Sabina

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