Journal of Oral Implantology Cone Beam Computerized Tomography (CBCT) Measurement of Alveolar Ridge at Posterior Mandible for Implant Graft Estimation --Manuscript Draft-Manuscript Number:
aaid-joi-D-14-00146R1
Full Title:
Cone Beam Computerized Tomography (CBCT) Measurement of Alveolar Ridge at Posterior Mandible for Implant Graft Estimation
Short Title:
CBCT measurement of posterior mandible
Article Type:
Clinical Research
Keywords:
cone beam computerized tomography; mandible; bone grafting
Corresponding Author:
Wenjian Zhang, DDS, Ph.D University of Texas School of Dentistry at Houston Houston, TX UNITED STATES
Corresponding Author Secondary Information: Corresponding Author's Institution:
University of Texas School of Dentistry at Houston
Corresponding Author's Secondary Institution: First Author:
Wenjian Zhang, DDS, Ph.D
First Author Secondary Information: Order of Authors:
Wenjian Zhang, DDS, Ph.D Justin Tullis, BS Robin Weltman
Order of Authors Secondary Information: Abstract:
Damaging the inferior alveolar nerve (IAN) is the most serious complication when harvesting an autogenous graft from posterior mandible. The objective of this study was to use cone beam computerized tomography (CBCT) to measure dimensions of the alveolar ridge in the posterior mandible for estimation of a safe graft size, and analyze how it is related to the gender, age, and dentition status of subjects. CBCT scans were screened to include 59 subjects without interfering pathologies. Alveolar height was measured from the alveolar crest to superior border of IAN, and also to the inferior border of the mandible. Alveolar width (from buccal to lingual cortical plates) and buccal bone thickness (from buccal cortical plate to mandibular molar mesial root buccal surface) were measured at the coronal, middle, and apical thirds divided from the alveolar crest to the IAN. It was found that males and dentate sites had larger alveolar dimensions than females and edentulous sites, respectively. Bone volume did not correlate significantly with age. Buccal bone thicknesses increased from coronal to apical and from the first to the third molar generally. A larger bone graft could be harvested from male than female patients, with a mean harvestable graft dimension (height X width in mm) for male was 15.5X3.2, and for female was 14.1X2.9. In conclusion, males and dentate arches demonstrate larger alveolar volumes than females and edentulous regions, respectively. Larger alveolar grafts can be harvested from males compared to the females. Age does not seem to affect alveolar dimension/graft volume.
Response to Reviewers:
The authors are very appreciative to the constructive and insightful comments from the reviewers. The whole manuscript has been revised according to the reviewers’ comments. The revisions were highlighted in yellow. A point-by-point response is listed below. The authors feel the content and formality of the manuscript have been improved significantly after the revision. Reviewer #1: see attached notes (copied here)
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Most changes are grammatical. I do have some content changes, most are minor details. Otherwise, a well performed, well written paper. Corrections are referenced by line number and include proposed changes: 4:"most likely complication" --bruising and swelling would be most likely complications. Perhaps this should be changed to "most serious complication" Answer: "most likely complication" was replaced by "most serious complication" as in lines 4 and 51. 6 grammar: "to measure (REMOVE THE) dimensions of THE alveolar ridge IN THE posterior" Answer: changes have been made as suggested in line 6. 9:grammar: "alveolar height was measured from THE alveolar" Answer: “the” was added in line 9. ABSTRACT Please define IAN and M1 and M3. Answer: “IAN” was defined as “inferior alveolar nerve” in line 4. “M1” and “M3” were deleted. “the first” and “the third molar” were used instead to keep the word count within 250 words, see lines 15-16. 29 delete "nowadays" it is superfluous Answer: “nowadays” was deleted from line 29. 36-37- what about the mandible, calvarium is not a traditional site Answer: “calvarium” was replaced by “mandible” in line 36. 55-56- please provide a reference Answer: Refs 33 and 34 have been added in line 56. 57 please rewrite for clarity Answer: The sentence in lines 56-57 has been rewritten as “In addition, a detailed understanding on how a patient’s gender and age affect ridge/graft volume is still missing.” “a patient’s gender and age” has been added for clarity. Is this a retrospective, if so please state it Answer: yes, it is a retrospective study. “Retrospective” has been added in line 58. 96 were they measured from the exterior surface or the cancellous side, please clarify Answer: they were measured from the exterior surface for both buccal and lingual cortical plates. “exterior” has been added in line 96. 101-104 these sites were dentate? Please clarify. Answer: yes, these were dentate sites. “This measurement was taken for dentate region only.” was added in line 102. 125-126 was this facial or lingual or both, please clarify Answer: the alveolar width was measured from exterior buccal to exterior lingual cortical plate, so it includes the width for both facial and lingual cortical plates and cancellous bone in between. To clarify, “measured from exterior buccal to exterior lingual cortical plate” was added in lines 125-126. 144-145 please rewrite for clarity: bone volume? Please clarify Answer: for clarify, the sentence was rewritten as “A larger size graft can be harvested from posterior mandible in male compared to female subjects in most cases.” Please see changes in lines 146-148. 153-5 - it would have been a good idea to measure the M-D dimension for a though study. Answer: the authors agree. A more thorough study could be undertaken to measure the M-D dimension of the grafts. 164-166 please provide a reference Answer: a new ref #38 was added as shown in line 168. Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation
177-8 please rewrite for clarity Answer: a more detailed explanation was given to indicate what the minimized variables were. We added “… such as recruiting comparable number of male vs. female patients, excluding patients with local and/or systemic conditions that would affect the quality and quantity of alveolar bone at posterior mandible …” in lines 179181. 184-189 would the data collected provide insight as to suggested dimensions for the surgeon in the posterior mandible, please discuss Illustration please provide a CBCT of an edentulous site Please make revisions according to the reviewer comments and resubmit this astute manuscript. Dennis Flanagan DDS MSc Sen Assoc Ed Answer: yes, the data collected would provide insight as to what sized graft may be harvested from posterior mandible. “Our data indicates a safe harvestable block graft dimension 15.5 X 3.2 and 14.1 X 2.9 (height X width in mm) for male and female, respectively, at dentate posterior mandible.” was added in lines 195-197. A new fig 3 was added to demonstrate the alveolar measurement at the edentulous sites. New fig 3 legend was added in lines 332-337. 10:grammar "border of THE mandible" Answer: “the” was added in line 10. 29:language remove the word "nowadays" it is unprofessional and will date the article Answer: "nowadays" was removed from line 29. 46:grammar: " body area OFFERS some advantages..." Answer: “offer” was replaced by “offers” in line 46. 50:grammar/clarity " of molar teeth and THE POSITION OF THE inferior alveolar..." Answer: “… the presence of molar teeth and inferior alveolar nerve canal… ” was replaced by “…the presence of molar teeth and the position of the inferior alveolar nerve canal…” in line 50. 56:grammar "...augmentation FROM THE posterior mandibular..." Answer: “… ridge augmentation at the posterior mandibular body …” was replaced by “… ridge augmentation from the posterior mandibular body …” in line 56. 72:grammar: "for the study after (remove THE) institutional review" Answer: “the” was removed from line 72. 76:grammar: "subjects had A CBCT scan" Answer: “a” was added in line 76. 86:grammar and confusing "long axis of THE alveolar ridge in the REGION OF THE posterior mandible" Answer: correction was made according to the suggestion in lines 86-87. 89:confusing "mesial root distal surface of mandibular molars"----I don't know exactly where and what you mean here. I can guess, but please rewrite to clarify. Answer: the sentence in lines 88-90 has been rewritten as “Cross-sectional views were generated along the distal surface of the mesial root of mandibular molars (see Fig 2B) or in the middle of the edentulous socket.” Please see Fig 2B for further clarification. The green line demonstrates where the cross-sectional view was taken. It was perpendicular to alveolar ridge and cut right at the distal surface of the mesial root of mandibular molar. We could not cut in the middle (furcation) of the molar, since there would be no root surface shown on the view, and the buccal bone width (from buccal cortical plate to molar root buccal surface) could not be measured. That’s why we chose to make the cross-sectional cut right at the distal surface of mesial root of the mandibular molars, which is very close to the middle of the tooth/socket.
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90:grammar "in the middle of THE edentulous socket" Answer: “the” was added in line 90. 125:grammar "width than m1 site" should be "sites" Answer: “site” was replaced by “sites” in line 126. 128:poor grammar "and so was dentate ridge compared..."---REWRITE, posibly break into multiple sentences Answer: the sentence has been rewritten as “Dentate ridge also demonstrated significantly larger alveolar width compared with edentulous region … ” as in lines 129130. 131:grammar "lingual dimension OF ~2.7mm" Answer: “by” was replaced by “of” in line 132. 143:grammar "width in mm) IN THE dentate PATIENT are...." Answer: “at dentate region” has been replaced by “in the dentate patient” in line 145. 151:grammar "THE second molar site is..." Answer: “The” has been added in line 154. 152 grammar "buccal bone COMPARED TO other molar sites" Answer: “… have the thickest buccal bone than other molar sites …” was replaced by “… have the thickest buccal bone compared to other molar sites …” as in line 155.
Reviewer #4: The article seems to be well documented and it aplicable for all clinicians to know so it is very useful to read, perhaps aplying this knowledge the author should suggest a blind study pre and post ramus grafting with ct scans before and after to see measurements with amount of complicatons, since now a days harvesitng from intraoral sites is very popular. The discussion is very poor since the work of making patients thru a comprehnsive diagnosis is important for the patient selection. Answer: see new addition to the “Discussion” section in lines 183-185: “A large blind clinical trial with CBCT scans pre- and post-ramus grafting will further validate our results and indicate potential complication risk.”
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Cone Beam Computerized Tomography (CBCT) Measurement of Alveolar Ridge at Posterior Mandible for Implant Graft Estimation Wenjian Zhang DDS, MS, Ph.D 1*, Justin Tullis BS 2, Robin Weltman DDS, MS 3 1
Department of Diagnostic & Biomedical Sciences 2
3
Second Year Dental Student
Department of Periodontics & Dental Hygiene
University of Texas School of Dentistry at Houston * Corresponding author: 7500 Cambridge Street, Suite 5366, Houston TX 77054 Phone: 713 486 4154; Fax: 713 486 4116; Email: [email protected] Running title: CBCT measurement of posterior mandible
ABSTRACT Damaging the inferior alveolar nerve (IAN) is the most serious complication when harvesting an autogenous graft from posterior mandible. The objective of this study was to use cone beam computerized tomography (CBCT) to measure dimensions of the alveolar ridge in the posterior mandible for estimation of a safe graft size, and analyze how it is related to the gender, age, and dentition status of subjects. CBCT scans were screened to include 59 subjects without interfering pathologies. Alveolar height was measured from the alveolar crest to superior border of IAN, and also to the inferior border of the mandible. Alveolar width (from buccal to lingual cortical plates) and buccal bone thickness (from buccal cortical plate to mandibular molar mesial root buccal surface) were measured at the coronal, middle, and apical thirds divided from the 1
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alveolar crest to the IAN. It was found that males and dentate sites had larger alveolar dimensions than females and edentulous sites, respectively. Bone volume did not correlate significantly with age. Buccal bone thicknesses increased from coronal to apical and from the first to the third molar generally. A larger bone graft could be harvested from male than female patients, with a mean harvestable graft dimension (height X width in mm) for male was 15.5X3.2, and for female was 14.1X2.9. In conclusion, males and dentate arches demonstrate larger alveolar volumes than females and edentulous regions, respectively. Larger alveolar grafts can be harvested from males compared to the females. Age does not seem to affect alveolar dimension/graft volume. Key words: cone beam computerized tomography; mandible; bone grafting
INTRODUCTION Bone grafts are widely used in the reconstruction of craniofacial skeletal defects and implant prosthetic rehabilitation.1-3 Successful osseointegration of the dental implant requires adequate volume of bone to support the implant.4 When alveolar atrophy impairs implant placement, ridge augmentation including guided bone regeneration and bone grafting may be considered.
5-9
Several different types of bone graft materials are available. Autogenous grafts are those obtained directly from the patient. Allografts are collected from the same species but different individuals. Xenografts are procured from different species. Alloplasts are synthetic or inorganic graft materials.10, 11 Among these different materials, autogenous bone grafts are considered the “gold standard” in repair of alveolar atrophy with regard to quantity, quality, and uneventful healing. 4, 12, 13
2
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Traditionally, the iliac crest, proximal tibia, rib, and mandible have been the principal sources of autogenous bone.
14-17
An intraoral approach is preferred for ridge augmentation, due to the
convenience of surgical access, a short operative and anesthesia time, minimal discomfort and morbidity, as well as no concerns of cutaneous scarring.8, 18-21 Bone grafts harvested from the mandible, such as those from the mandibular symphysis, external oblique ridge, and ascending ramus, have been used for alveolar repair to allow implant placement with extremely favorable results.
13, 22-24
The mandibular donor site is one of the alternative sources of intramembraneous
bone, which maintain their dense quality and undergo less resorption compared with endochondral bone.25-28
In the mandible, the ramus/posterior body area offers some advantages over the symphysis as a donor site for alveolar ridge reconstruction, which include minimal esthetic concern, lower incidence of incision dehiscence, and less postoperative neurosensory disturbances.
29-32
The
volume of harvestable bone in posterior mandible is dictated by anatomic landmarks, such as the presence of molar teeth and the position of the inferior alveolar nerve canal (IAN).
31
The
most serious complication of bone harvesting at this site is injury to the inferior alveolar neurovascular bundle.
2
Therefore, a clear understanding of applied anatomy in this area will
help maximize graft size and minimize risk of nerve and vessel damage.
In the literature, there are limited studies investigating the harvestable graft size for ridge augmentation from the posterior mandibular body and ramus area
33, 34
. In addition, a detailed
understanding on how a patient’s gender and age affect ridge/graft volume is still missing. The aim of this retrospective study is to measure the size of alveolar ridge and available bone for a 3
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block graft from the posterior mandible with cone beam computerized tomography (CBCT), and further correlate the findings with the gender, age, and dentition status of the patients.
MATERIALS AND METHODS Patient population The electronic patient records of individuals who had CBCT images taken at the Radiology Division, University of Texas School of Dentistry at Houston were screened according to the selection criteria. The exclusion criteria were: 1) systemic/endocrine diseases that influence bone
metabolism,
e.g.
osteoporosis,
hyperparathyroidism,
Paget’s
disease,
renal
osteodystrophy; 2) topical conditions that may affect bone quantity and quality at posterior mandible, e.g. moderate to severe periodontal disease, cyst, neoplasm, prior trauma or surgery (except tooth extraction). A total of 59 subjects were included in the study. All subjects were at least partially dentate in the posterior mandible. There were 28 males and 31 females, with an age range of 19-74 years old. IRB exemption was obtained for the study after institutional review.
CBCT image acquisition All the subjects had a CBCT scan covering both maxillary and mandibular arches with a field of view (FOV) of 150 x 90 mm2. The scans were acquired at 90 kV, 10 mA, 16 sec, and a 0.2 mm3 voxel size with a Kodak 9500 unit (Carestream Health, Inc, Rochester, NY). CBCT images were reconstructed with Anatomage Invivo 5.1 software at 1mm thickness. All images were displayed
4
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on a 19-inch flat panel screen (HP Development Company, Palo Alto, CA) with a 1920 X 1080 pixel resolution and viewed in a dimly lit environment.
Image measurement All measurements were performed from molar sites in the posterior right mandible. Before taking measurements, all the images were checked for the consistency of head placement. If head tilting was noticed, the image would be reoriented to ensure the long axis of the alveolar ridge in the region of the posterior mandible was perpendicular to the floor. The IAN was traced on the reconstructed panoramic view and location confirmed using cross-section views. Crosssectional views were generated along the distal surface of the mesial root of mandibular molars (see Fig 2B) or in the middle of the edentulous socket. Alveolar height, width and buccal bone thickness were measured on the cross-sectional views as detailed below (also see Fig 1-3). The first (M1), second (M2), and third (M3) molar sites were each measured separately. 1. Alveolar heights Alveolar heights were measured in two ways: 1) from alveolar crest to superior border of IAN; 2) from alveolar crest to the inferior border of mandible. 2. Alveolar width (from exterior buccal to exterior lingual cortical plate) On the cross-sectional views, the distance from alveolar crest to superior border of IAN was divided into thirds. Alveolar width was measured at the middle of each third and designated as coronal, middle, and apical width. An average was taken from the three measurements for each molar site. 3. Buccal bone thickness (from exterior buccal cortical plate to mesial root buccal surface) 5
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This measurement was taken for dentate region only. For each site with a molar present, the buccal bone thickness was measured at coronal, middle, and apical thirds, and an average was taken, similar to how alveolar width was measured.
Statistical analysis Data were presented as means ± standard deviation (SD). The statistical difference was tested using two-tailed t-test at a p value less than 0.05.
RESULTS Fifty-nine CBCT scans from subjects aged 19-74 year-old were evaluated. Among the subjects, twenty-eight were males and thirty-one were females (Table 1). Their dentation status in the posterior right mandible was listed in Table 2.
Alveolar heights There was an increase of alveolar height (border-crest and IAN-crest) from M3 to M1 site (Table 3). Males demonstrated significantly higher alveolar ridges when compared to females for both measurements (Table 3). Greater alveolar ridge heights were found in dentate vs. edentulous regions, with significance reached at the M1 sites (28.3 ± 2.8 vs. 24.9 ± 3.2 mm for border-crest, and 17.2 ± 2.7 vs. 14.5 ± 2.9 mm for IAN-crest, respectively, p
aaid-joi-D-14-00146R1
Full Title:
Cone Beam Computerized Tomography (CBCT) Measurement of Alveolar Ridge at Posterior Mandible for Implant Graft Estimation
Short Title:
CBCT measurement of posterior mandible
Article Type:
Clinical Research
Keywords:
cone beam computerized tomography; mandible; bone grafting
Corresponding Author:
Wenjian Zhang, DDS, Ph.D University of Texas School of Dentistry at Houston Houston, TX UNITED STATES
Corresponding Author Secondary Information: Corresponding Author's Institution:
University of Texas School of Dentistry at Houston
Corresponding Author's Secondary Institution: First Author:
Wenjian Zhang, DDS, Ph.D
First Author Secondary Information: Order of Authors:
Wenjian Zhang, DDS, Ph.D Justin Tullis, BS Robin Weltman
Order of Authors Secondary Information: Abstract:
Damaging the inferior alveolar nerve (IAN) is the most serious complication when harvesting an autogenous graft from posterior mandible. The objective of this study was to use cone beam computerized tomography (CBCT) to measure dimensions of the alveolar ridge in the posterior mandible for estimation of a safe graft size, and analyze how it is related to the gender, age, and dentition status of subjects. CBCT scans were screened to include 59 subjects without interfering pathologies. Alveolar height was measured from the alveolar crest to superior border of IAN, and also to the inferior border of the mandible. Alveolar width (from buccal to lingual cortical plates) and buccal bone thickness (from buccal cortical plate to mandibular molar mesial root buccal surface) were measured at the coronal, middle, and apical thirds divided from the alveolar crest to the IAN. It was found that males and dentate sites had larger alveolar dimensions than females and edentulous sites, respectively. Bone volume did not correlate significantly with age. Buccal bone thicknesses increased from coronal to apical and from the first to the third molar generally. A larger bone graft could be harvested from male than female patients, with a mean harvestable graft dimension (height X width in mm) for male was 15.5X3.2, and for female was 14.1X2.9. In conclusion, males and dentate arches demonstrate larger alveolar volumes than females and edentulous regions, respectively. Larger alveolar grafts can be harvested from males compared to the females. Age does not seem to affect alveolar dimension/graft volume.
Response to Reviewers:
The authors are very appreciative to the constructive and insightful comments from the reviewers. The whole manuscript has been revised according to the reviewers’ comments. The revisions were highlighted in yellow. A point-by-point response is listed below. The authors feel the content and formality of the manuscript have been improved significantly after the revision. Reviewer #1: see attached notes (copied here)
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Most changes are grammatical. I do have some content changes, most are minor details. Otherwise, a well performed, well written paper. Corrections are referenced by line number and include proposed changes: 4:"most likely complication" --bruising and swelling would be most likely complications. Perhaps this should be changed to "most serious complication" Answer: "most likely complication" was replaced by "most serious complication" as in lines 4 and 51. 6 grammar: "to measure (REMOVE THE) dimensions of THE alveolar ridge IN THE posterior" Answer: changes have been made as suggested in line 6. 9:grammar: "alveolar height was measured from THE alveolar" Answer: “the” was added in line 9. ABSTRACT Please define IAN and M1 and M3. Answer: “IAN” was defined as “inferior alveolar nerve” in line 4. “M1” and “M3” were deleted. “the first” and “the third molar” were used instead to keep the word count within 250 words, see lines 15-16. 29 delete "nowadays" it is superfluous Answer: “nowadays” was deleted from line 29. 36-37- what about the mandible, calvarium is not a traditional site Answer: “calvarium” was replaced by “mandible” in line 36. 55-56- please provide a reference Answer: Refs 33 and 34 have been added in line 56. 57 please rewrite for clarity Answer: The sentence in lines 56-57 has been rewritten as “In addition, a detailed understanding on how a patient’s gender and age affect ridge/graft volume is still missing.” “a patient’s gender and age” has been added for clarity. Is this a retrospective, if so please state it Answer: yes, it is a retrospective study. “Retrospective” has been added in line 58. 96 were they measured from the exterior surface or the cancellous side, please clarify Answer: they were measured from the exterior surface for both buccal and lingual cortical plates. “exterior” has been added in line 96. 101-104 these sites were dentate? Please clarify. Answer: yes, these were dentate sites. “This measurement was taken for dentate region only.” was added in line 102. 125-126 was this facial or lingual or both, please clarify Answer: the alveolar width was measured from exterior buccal to exterior lingual cortical plate, so it includes the width for both facial and lingual cortical plates and cancellous bone in between. To clarify, “measured from exterior buccal to exterior lingual cortical plate” was added in lines 125-126. 144-145 please rewrite for clarity: bone volume? Please clarify Answer: for clarify, the sentence was rewritten as “A larger size graft can be harvested from posterior mandible in male compared to female subjects in most cases.” Please see changes in lines 146-148. 153-5 - it would have been a good idea to measure the M-D dimension for a though study. Answer: the authors agree. A more thorough study could be undertaken to measure the M-D dimension of the grafts. 164-166 please provide a reference Answer: a new ref #38 was added as shown in line 168. Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation
177-8 please rewrite for clarity Answer: a more detailed explanation was given to indicate what the minimized variables were. We added “… such as recruiting comparable number of male vs. female patients, excluding patients with local and/or systemic conditions that would affect the quality and quantity of alveolar bone at posterior mandible …” in lines 179181. 184-189 would the data collected provide insight as to suggested dimensions for the surgeon in the posterior mandible, please discuss Illustration please provide a CBCT of an edentulous site Please make revisions according to the reviewer comments and resubmit this astute manuscript. Dennis Flanagan DDS MSc Sen Assoc Ed Answer: yes, the data collected would provide insight as to what sized graft may be harvested from posterior mandible. “Our data indicates a safe harvestable block graft dimension 15.5 X 3.2 and 14.1 X 2.9 (height X width in mm) for male and female, respectively, at dentate posterior mandible.” was added in lines 195-197. A new fig 3 was added to demonstrate the alveolar measurement at the edentulous sites. New fig 3 legend was added in lines 332-337. 10:grammar "border of THE mandible" Answer: “the” was added in line 10. 29:language remove the word "nowadays" it is unprofessional and will date the article Answer: "nowadays" was removed from line 29. 46:grammar: " body area OFFERS some advantages..." Answer: “offer” was replaced by “offers” in line 46. 50:grammar/clarity " of molar teeth and THE POSITION OF THE inferior alveolar..." Answer: “… the presence of molar teeth and inferior alveolar nerve canal… ” was replaced by “…the presence of molar teeth and the position of the inferior alveolar nerve canal…” in line 50. 56:grammar "...augmentation FROM THE posterior mandibular..." Answer: “… ridge augmentation at the posterior mandibular body …” was replaced by “… ridge augmentation from the posterior mandibular body …” in line 56. 72:grammar: "for the study after (remove THE) institutional review" Answer: “the” was removed from line 72. 76:grammar: "subjects had A CBCT scan" Answer: “a” was added in line 76. 86:grammar and confusing "long axis of THE alveolar ridge in the REGION OF THE posterior mandible" Answer: correction was made according to the suggestion in lines 86-87. 89:confusing "mesial root distal surface of mandibular molars"----I don't know exactly where and what you mean here. I can guess, but please rewrite to clarify. Answer: the sentence in lines 88-90 has been rewritten as “Cross-sectional views were generated along the distal surface of the mesial root of mandibular molars (see Fig 2B) or in the middle of the edentulous socket.” Please see Fig 2B for further clarification. The green line demonstrates where the cross-sectional view was taken. It was perpendicular to alveolar ridge and cut right at the distal surface of the mesial root of mandibular molar. We could not cut in the middle (furcation) of the molar, since there would be no root surface shown on the view, and the buccal bone width (from buccal cortical plate to molar root buccal surface) could not be measured. That’s why we chose to make the cross-sectional cut right at the distal surface of mesial root of the mandibular molars, which is very close to the middle of the tooth/socket.
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90:grammar "in the middle of THE edentulous socket" Answer: “the” was added in line 90. 125:grammar "width than m1 site" should be "sites" Answer: “site” was replaced by “sites” in line 126. 128:poor grammar "and so was dentate ridge compared..."---REWRITE, posibly break into multiple sentences Answer: the sentence has been rewritten as “Dentate ridge also demonstrated significantly larger alveolar width compared with edentulous region … ” as in lines 129130. 131:grammar "lingual dimension OF ~2.7mm" Answer: “by” was replaced by “of” in line 132. 143:grammar "width in mm) IN THE dentate PATIENT are...." Answer: “at dentate region” has been replaced by “in the dentate patient” in line 145. 151:grammar "THE second molar site is..." Answer: “The” has been added in line 154. 152 grammar "buccal bone COMPARED TO other molar sites" Answer: “… have the thickest buccal bone than other molar sites …” was replaced by “… have the thickest buccal bone compared to other molar sites …” as in line 155.
Reviewer #4: The article seems to be well documented and it aplicable for all clinicians to know so it is very useful to read, perhaps aplying this knowledge the author should suggest a blind study pre and post ramus grafting with ct scans before and after to see measurements with amount of complicatons, since now a days harvesitng from intraoral sites is very popular. The discussion is very poor since the work of making patients thru a comprehnsive diagnosis is important for the patient selection. Answer: see new addition to the “Discussion” section in lines 183-185: “A large blind clinical trial with CBCT scans pre- and post-ramus grafting will further validate our results and indicate potential complication risk.”
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Cone Beam Computerized Tomography (CBCT) Measurement of Alveolar Ridge at Posterior Mandible for Implant Graft Estimation Wenjian Zhang DDS, MS, Ph.D 1*, Justin Tullis BS 2, Robin Weltman DDS, MS 3 1
Department of Diagnostic & Biomedical Sciences 2
3
Second Year Dental Student
Department of Periodontics & Dental Hygiene
University of Texas School of Dentistry at Houston * Corresponding author: 7500 Cambridge Street, Suite 5366, Houston TX 77054 Phone: 713 486 4154; Fax: 713 486 4116; Email: [email protected] Running title: CBCT measurement of posterior mandible
ABSTRACT Damaging the inferior alveolar nerve (IAN) is the most serious complication when harvesting an autogenous graft from posterior mandible. The objective of this study was to use cone beam computerized tomography (CBCT) to measure dimensions of the alveolar ridge in the posterior mandible for estimation of a safe graft size, and analyze how it is related to the gender, age, and dentition status of subjects. CBCT scans were screened to include 59 subjects without interfering pathologies. Alveolar height was measured from the alveolar crest to superior border of IAN, and also to the inferior border of the mandible. Alveolar width (from buccal to lingual cortical plates) and buccal bone thickness (from buccal cortical plate to mandibular molar mesial root buccal surface) were measured at the coronal, middle, and apical thirds divided from the 1
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alveolar crest to the IAN. It was found that males and dentate sites had larger alveolar dimensions than females and edentulous sites, respectively. Bone volume did not correlate significantly with age. Buccal bone thicknesses increased from coronal to apical and from the first to the third molar generally. A larger bone graft could be harvested from male than female patients, with a mean harvestable graft dimension (height X width in mm) for male was 15.5X3.2, and for female was 14.1X2.9. In conclusion, males and dentate arches demonstrate larger alveolar volumes than females and edentulous regions, respectively. Larger alveolar grafts can be harvested from males compared to the females. Age does not seem to affect alveolar dimension/graft volume. Key words: cone beam computerized tomography; mandible; bone grafting
INTRODUCTION Bone grafts are widely used in the reconstruction of craniofacial skeletal defects and implant prosthetic rehabilitation.1-3 Successful osseointegration of the dental implant requires adequate volume of bone to support the implant.4 When alveolar atrophy impairs implant placement, ridge augmentation including guided bone regeneration and bone grafting may be considered.
5-9
Several different types of bone graft materials are available. Autogenous grafts are those obtained directly from the patient. Allografts are collected from the same species but different individuals. Xenografts are procured from different species. Alloplasts are synthetic or inorganic graft materials.10, 11 Among these different materials, autogenous bone grafts are considered the “gold standard” in repair of alveolar atrophy with regard to quantity, quality, and uneventful healing. 4, 12, 13
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Traditionally, the iliac crest, proximal tibia, rib, and mandible have been the principal sources of autogenous bone.
14-17
An intraoral approach is preferred for ridge augmentation, due to the
convenience of surgical access, a short operative and anesthesia time, minimal discomfort and morbidity, as well as no concerns of cutaneous scarring.8, 18-21 Bone grafts harvested from the mandible, such as those from the mandibular symphysis, external oblique ridge, and ascending ramus, have been used for alveolar repair to allow implant placement with extremely favorable results.
13, 22-24
The mandibular donor site is one of the alternative sources of intramembraneous
bone, which maintain their dense quality and undergo less resorption compared with endochondral bone.25-28
In the mandible, the ramus/posterior body area offers some advantages over the symphysis as a donor site for alveolar ridge reconstruction, which include minimal esthetic concern, lower incidence of incision dehiscence, and less postoperative neurosensory disturbances.
29-32
The
volume of harvestable bone in posterior mandible is dictated by anatomic landmarks, such as the presence of molar teeth and the position of the inferior alveolar nerve canal (IAN).
31
The
most serious complication of bone harvesting at this site is injury to the inferior alveolar neurovascular bundle.
2
Therefore, a clear understanding of applied anatomy in this area will
help maximize graft size and minimize risk of nerve and vessel damage.
In the literature, there are limited studies investigating the harvestable graft size for ridge augmentation from the posterior mandibular body and ramus area
33, 34
. In addition, a detailed
understanding on how a patient’s gender and age affect ridge/graft volume is still missing. The aim of this retrospective study is to measure the size of alveolar ridge and available bone for a 3
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block graft from the posterior mandible with cone beam computerized tomography (CBCT), and further correlate the findings with the gender, age, and dentition status of the patients.
MATERIALS AND METHODS Patient population The electronic patient records of individuals who had CBCT images taken at the Radiology Division, University of Texas School of Dentistry at Houston were screened according to the selection criteria. The exclusion criteria were: 1) systemic/endocrine diseases that influence bone
metabolism,
e.g.
osteoporosis,
hyperparathyroidism,
Paget’s
disease,
renal
osteodystrophy; 2) topical conditions that may affect bone quantity and quality at posterior mandible, e.g. moderate to severe periodontal disease, cyst, neoplasm, prior trauma or surgery (except tooth extraction). A total of 59 subjects were included in the study. All subjects were at least partially dentate in the posterior mandible. There were 28 males and 31 females, with an age range of 19-74 years old. IRB exemption was obtained for the study after institutional review.
CBCT image acquisition All the subjects had a CBCT scan covering both maxillary and mandibular arches with a field of view (FOV) of 150 x 90 mm2. The scans were acquired at 90 kV, 10 mA, 16 sec, and a 0.2 mm3 voxel size with a Kodak 9500 unit (Carestream Health, Inc, Rochester, NY). CBCT images were reconstructed with Anatomage Invivo 5.1 software at 1mm thickness. All images were displayed
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on a 19-inch flat panel screen (HP Development Company, Palo Alto, CA) with a 1920 X 1080 pixel resolution and viewed in a dimly lit environment.
Image measurement All measurements were performed from molar sites in the posterior right mandible. Before taking measurements, all the images were checked for the consistency of head placement. If head tilting was noticed, the image would be reoriented to ensure the long axis of the alveolar ridge in the region of the posterior mandible was perpendicular to the floor. The IAN was traced on the reconstructed panoramic view and location confirmed using cross-section views. Crosssectional views were generated along the distal surface of the mesial root of mandibular molars (see Fig 2B) or in the middle of the edentulous socket. Alveolar height, width and buccal bone thickness were measured on the cross-sectional views as detailed below (also see Fig 1-3). The first (M1), second (M2), and third (M3) molar sites were each measured separately. 1. Alveolar heights Alveolar heights were measured in two ways: 1) from alveolar crest to superior border of IAN; 2) from alveolar crest to the inferior border of mandible. 2. Alveolar width (from exterior buccal to exterior lingual cortical plate) On the cross-sectional views, the distance from alveolar crest to superior border of IAN was divided into thirds. Alveolar width was measured at the middle of each third and designated as coronal, middle, and apical width. An average was taken from the three measurements for each molar site. 3. Buccal bone thickness (from exterior buccal cortical plate to mesial root buccal surface) 5
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This measurement was taken for dentate region only. For each site with a molar present, the buccal bone thickness was measured at coronal, middle, and apical thirds, and an average was taken, similar to how alveolar width was measured.
Statistical analysis Data were presented as means ± standard deviation (SD). The statistical difference was tested using two-tailed t-test at a p value less than 0.05.
RESULTS Fifty-nine CBCT scans from subjects aged 19-74 year-old were evaluated. Among the subjects, twenty-eight were males and thirty-one were females (Table 1). Their dentation status in the posterior right mandible was listed in Table 2.
Alveolar heights There was an increase of alveolar height (border-crest and IAN-crest) from M3 to M1 site (Table 3). Males demonstrated significantly higher alveolar ridges when compared to females for both measurements (Table 3). Greater alveolar ridge heights were found in dentate vs. edentulous regions, with significance reached at the M1 sites (28.3 ± 2.8 vs. 24.9 ± 3.2 mm for border-crest, and 17.2 ± 2.7 vs. 14.5 ± 2.9 mm for IAN-crest, respectively, p
