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@#Introduction: Labial bone with adequate height and width is crucial for an implant to be successfully placed and ensure the stability of treatment outcome in the long term. The objective of this study was to employ cone-beam computed tomography (CBCT) assessment in evaluating the differences in labial alveolar bone morphology among the Kuantan population in Malaysia. Methods: A total of 60 images taken from Kulliyyah of Dentistry, International Islamic University Malaysia, between 2009 and 2019 were analysed. The root diameter, labial and palatal plate thickness, the labial bony curvature angle beneath the root apex, and the distance from the deepest point of labial bony curvature to the root apex were all measured on each of the maxillary anterior teeth. Results: At 3 mm below the cementoenamel junction, the mean (± standard deviation; SD) thickness of the labial plate for maxillary anterior teeth was 1.45 ± 0.62 mm, 1.38 ± 0.50 mm, and 1.61 ± 0.66 mm for the lateral incisor, central incisor, and canine, respectively. Below the root apex, the labial bony curvature angle was 233.63 ± 17.74 for the central incisor, 235.68 ± 17.74 for the lateral incisor and 233.81 ± 11.09 for the canine. Discussion: The result revealed a favourable labial plate in the Kuantan population when implant in the aesthetic zone is planned. Conclusion: Labial alveolar bone thickness of the Kuantan population was thin within 1.5 mm while the palatal plate was thick. Overall, labial alveolar bone was present within 3 mm below the cementoenamel junction. The labial bony curvature was highest and most curved for the central incisor compared to the lateral incisor and canine.
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@#It has been traditionally believed that a 1:1 cortical bone remodeling/tooth movement ratio has been preserved during orthodontic treatment for tooth movement, with the alveolar bone on the tension side growing and the alveolar bone on the pressure side resorbing to maintain the balance of the alveolar bone. However, recent studies have shown that alveolar bone loss has been found in patients who have undergone orthodontic treatment, suggesting that the alveolar bone does not change as the teeth change over time. Whether the morphology of the alveolar bone will change when the anterior teeth are moved has been the clinical focus. The changes of anterior alveolar bone in patients who have undergone tooth extraction after orthodontic treatment were summerized by literature review in this paper. The results of the review showed that the alveolar bone at the lingual/palatal root-cervical site of the anterior root is more prone to bone loss after extensive movement of the anterior teeth. With the development of imaging technology, CBCT is now more commonly used for analysis instead of two-dimensional images for measurement, as its results are more accurate. However, there are few multifactorial studies in which CBCT has been used to assess the morphological changes in the alveolar bone. The focus of future research is to compare the long-term changes in the anterior alveolar bone of patients of different ages based on three-dimensional imaging, and to study the correlation between different skeletal features, tooth movement patterns and alveolar bone remodeling.
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Objective@#To investigate the features of alveolar bone morphology of mandibular central incisors in high-angle adult females using cone-beam computed tomography (CBCT) and evaluate the influence of aging in these patients.@*Methods@# CBCT and lateral cephalometric images of 142 untreated adult female patients were selected and grouped by facial growth pattern. The number of high-angle cases was increased to 164 to further explore the difference within high-angle adult females who were divided into two groups according to age. The indexes of alveolar bone height and thickness in the lower incisor region and inclination of the lower incisors were measured by Dolphin software. The data was statistically analyzed.@*Results@#Compared with the average-angle group, the high-angle group had a lower alveolar bone attachment level (P < 0.05) and less bone thickness at the root apex level (P < 0.05). The thickness of lingual alveolar bone decreased with labial inclination of the lower incisors in both the high-angle and average-angle groups (r = -0.251, P = 0.025; r = -0.428, P = 0.001, respectively). In hyperdivergent female patients, the middle-aged group had a lower attachment level of alveolar bone than the young group (P < 0.05), but no significant difference in bone thickness at the root apex level (P > 0.05) was found between the two groups@*Conclusion @# High-angle adult females had thinner mandibular anterior alveolar bone with significantly lower attachment levels. Aging and inclination of lower incisors influenced bone morphology and should be taken into careful consideration.
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Objective@#To investigate the relationship between the thickness of the lateral wall of the maxillary sinus and patient age and sex at different tooth sites to provide a reference for sinus floor elevations.@*Methods @#Cone-beam CT（CBCT） imaging data were collected from 222 patients admitted to the Department of Stomatology, the First Hospital of Shanxi Medical University, from March 2020 to October 2020. The thicknesses of the maxillary sinus lateral wall of the first premolar, second premolar, first molar and second molar were observed and measured on the coronal plane of CBCT images, and the relationship between the maxillary sinus lateral wall thickness and patient sex was analyzed. The patients were divided into the following groups according to their age: ①the young group (18~29 years old), ②the middle-aged group (30~59 years old), and ③the elderly group (≥ 60 years old). The difference in the maxillary sinus lateral wall thickness was compared among these three age groups@*Results@#The mean thicknesses of the maxillary sinus lateral wall at the first premolar, second premolar, first molar and second molar were （1.61 ± 0.58） mm, （1.68 ± 0.66） mm, （2.00 ± 0.76） mm and （1.71 ± 0.71） mm, respectively. The maximum thickness of the lateral wall was located at the first molar (P< 0.05). The thickness of the maxillary sinus lateral wall in the young group was significantly thicker than that in the middle-aged group and the elderly group at the first premolar and first molar (P < 0.05). The thickness of the maxillary sinus lateral wall in males was significantly thicker than that in females at the second molar [(1.78 ± 0.80) mm vs. (1.63 ± 0.62) mm, P=0.029].@*Conclusion@#The mean thickness of the lateral wall changes at different reference points. The maxillary sinus lateral wall is the thickest at M1. The thickness of the maxillary sinus lateral wall decreased with age, and the thickness of the lateral wall was higher in males than in females.
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@#As a minimally invasive procedure, micro-osteoperforations (MOPs) achieve desired therapeutic effect with minimal surgical intervention. The operation is relatively simple, and the effect of assisted orthodontic treatment is obvious. However, due to the lack of long-term follow-up studies, there is no unified consensus on the long-term stability of the procedure. This article reviews the research status of MOPs, biological and biomechanical mechanisms, clinical applications and limitations. MOPs can shorten orthodontic treatment time and accelerate tooth movement by exerting regional acceleratory phenomena (RAP). At the same time, this procedure will not damage the health of the periodontal tissue, and the postoperative bleeding and postoperative reaction are minor. In addition, the pain and discomfort of patients were relatively mild and acceptable. However, it also has limitations, mainly including the limited time of the RAP effect of MOPs. Although this procedure is a minimally invasive surgery, there is still a risk of treating regional bone defects. At present, it is still necessary to increase the sample size and extend the follow-up time to evaluate the long-term stability of MOPs.
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BACKGROUND: With the aging of population, brittle fracture diseases have attracted more and more attention from clinicians. Bone mineral density detection cannot meet the risk assessment of brittle fracture. As one of the new directions and methods to evaluate the risk of brittle fracture, cortical thickness has been studied and discussed by more and more scholars. OBJECTIVE: To explore the correlation of bone cortical thickness values and X-ray gray values in different planes of proximal femur with hip brittle fracture in women aged over 50 years old under X-ray DR photography, so as to evaluate the most appropriate measurement plane for predicting the risk of hip brittle fracture in women among different planes of proximal femur. METHODS: According to the inclusion criteria, relevant clinical data of 100 female patients aged over 50 years old who underwent X-ray DR pelvic radiograph examination at Department of Radiology of the Ninth Affiliated Hospital of Guangxi Medical University from July 2018 to June 2019 were collected. All patients signed the informed consents and the study was approved by the ethics committee of the hospital. The measurement planes of cortical thickness of the proximal femur were designed to be the middle part of femoral neck, within 1 cm above the lesser trochanter, and within 1 cm below the lesser trochanter, with a total of three groups of measurement planes. The gray value of X-ray was measured by taking the line between the middle point of the great rotor and the small rotor as the rectangular diagonal line to take the rectangular area for measurement. RESULTS AND CONCLUSION: (1) Women aged 50-64 years were as group A (n=50) and those aged 65 years and older were as group B (n=50). (2) The cortical thickness and X-ray gray value within 1 cm below the lesser trochanter, and within 1 cm above the lesser trochanter in the group B were significantly lower than those in the group A; fracture rate was higher in group A than in group B (P 0.05). (3) On the whole, cortical thickness values were highest in the within 1 cm below the lesser trochanter, followed by within 1 cm above the lesser trochanter and lowest in the middle part of the femoral neck (P 0.05). (5) The difference of cortical thickness within 1 cm below the lesser trochanter and within 1 cm above the lesser trochanter between fracture and non-fracture groups in the group A was significant (P 0.05). At the age above 50 years, the difference of cortical thickness and X-ray gray value in each measured plane between fracture and the non-fracture groups was significant (P < 0.05). (6) To conclude, the cortical thickness becomes thinner and the gray value of X-ray becomes smaller, and the possibility of brittle fracture of hip becomes higher. When assessing the risk of hip fracture in women aged over 50 years using cortical thickness of the proximal femur, measurement within 1 cm below the lesser trochanter is recommended.
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OBJECTIVE@#To explore the correlation among gingival thickness (GT), underlying alveolar bone thickness (BT), and other periodontal biotype characteristics in the maxillary anterior.@*METHODS@#A total of 40 young volunteers with healthy periodontal were involved in this research. The periodontal probe was previously used to divide the gingiva from thick to thin. Two records were measured by cone beam CT (CBCT) GT, which was measured at the cement-enamel junction level; and BT, which was measured at 3 locations: 1, 3, 5 mm below the alveolar crest. Oral and gypsum measurements were used to analyze the associations of the crown width/crown length ratio (CW/CL), the keratinized mucosa width (KM), and the free gingival margin curvature.@*RESULTS@#Significant difference in the GT was observed between the thick and thin biotypes, which were divided by periodontal probe (P<0.01). Difference was observed in each periodontal biotype characteristic between the thick (GT≥1 mm) and thin biotypes (GT<1 mm) (P<0.05). BT was positively associated with GT (r=0.293, P=0.001), CW/CL (r=0.273, P=0.003), KM (r=0.291, P=0.001), and free gingival margin curvature (r=0.290, P=0.001).@*CONCLUSIONS@#The transparency of the probing in the sulcus could analyze the GT qualitatively. The thick and thin biotypes have different periodontal biotype characteristics. Compared with individuals with thick biotype, those with thin biotype are susceptible to risk dental aesthetic.
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Humans , Alveolar Process , Cone-Beam Computed Tomography , Gingiva , Maxilla , Tooth CrownABSTRACT
OBJECTIVES: Extraction of mandibular posterior teeth followed by immediate implant placement is considered as an optimal technique of immediate prosthetic rehabilitation. The analysis of alveolar bone dimensions with Cone Beam Computerized Tomography prior to implant placement is a prime determinant in treatment planning. Hence this preliminary study was conducted to analyze the alveolar bone dimensions in dentate mandibular posterior teeth to evaluate the available bone which can be utilized for immediate implant placements. MATERIALS AND METHODS: Retrospective data of 200 cases of full volume CBCT was procured from Riyadh Elm University (REU) database and reviewed for eligibility. Atotal of 10 cases were included in the study. Scans were assessed for thickness of buccal and lingual walls at 4mm below the CEJ (MP1) and at midroot level (MP2). Alveolar width was assessed at most coronal point on alveolar bone (BW1) and at superior border of mandibular canal (BW2). The height was be calculated by measuring the vertical distance between BW1 and BW2. Data was tabulated and statistically analyzed using unpaired t-test. RESULTS: The results of our study indicates that dimensions of buccal and lingual bone walls of all teeth at MP1 and MP2 in PM1, PM2 and M1 were statistically significant. Also only the 1st premolar (PM1) showed statistical significance with regard to dimensions at BW1 and BW2. CONCLUSION: The present study highlights the need for further studies with larger samples which can impact the immediate implant success rates in mandibular posterior teeth
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Objective@# To study the remodeling of alveolar bone after retraction of the maxillary incisors assisting with micro-implant anchorage in adult patients with maxillary protrusion by CBCT.@*Methods@#Forty patients who were treated with extraction of the maxillary first premolars with microimplant anchorage meeting the inclusion criteria were selected. The CBCT data before and after treatment were collected, and the Dolphin Imaging 3D measurement software was used to measure and analyze the height and thickness of the alveolar bone of the 80 upper central incisors and the 80 lateral incisors.@*Results @#After retraction of the incisors assisting with microimplant anchorage, the labial alveolar bone height of the maxillary central incisors decreased (0.11 ± 0.33) mm, and the lingual alveolar bone height of the maxillary central incisors decreased (0.85 ± 1.23) mm. The labial alveolar bone height of the maxillary lateral incisors decreased (0.18 ± 0.42) mm, and the lingual alveolar bone height of the maxillary lateral incisors decreased (1.13 ± 1.14 ) mm. The reduction in the lingual alveolar bone height was greater than that of the labial side, and the difference was statistically significant (P < 0.05). The labial alveolar bone thickness of the maxillary central incisors increased (the root cervix, the root media and the root apex), and the difference was statistically significant (P < 0.001). The labial alveolar bone thickness of the maxillary lateral incisors also increased (P < 0.05), while the lingual alveolar bone thickness and the total alveolar bone thickness of the maxillary central and lateral incisors decreased (P < 0.001). @*Conclusion@#In adults with maxillary protrusion, the microimplant was used to assist the reduction of the anterior teeth. The alveolar bone height of the maxillary incisors was reduced, and the palatal alveolar bone height decreased more than that of the labial side. The alveolar bone of the labrum was thickened, and the palatal alveolar bone thickness and the total alveolar bone thickness of the maxillary incisors were reduced after treatment.
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PURPOSE: It has been suggested that resonance frequency analysis (RFA) can measure changes in the stability of dental implants during osseointegration. This retrospective study aimed to evaluate dental implant stability at the time of surgery (primary stability; PS) and secondary stability (SS) after ossseointegration using RFA, and to investigate the relationship between implant stability and cortical bone thickness. METHODS: In total, 113 patients who attended the Tohoku University Hospital Dental Implant Center were included in this study. A total of 229 implants were placed in either the mandibular region (n = 118) or the maxilla region (n = 111), with bone augmentation procedures used in some cases. RFA was performed in 3 directions, and the lowest value was recorded. The preoperative thickness of cortical bone at the site of implant insertion was measured digitally using computed tomography, excluding cases of bone grafts and immediate implant placements. RESULTS: The mean implant stability quotient (ISQ) was 69.34±9.43 for PS and 75.99±6.23 for SS. The mandibular group had significantly higher mean ISQ values than the maxillary group for both PS and SS (P < 0.01). A significant difference was found in the mean ISQ values for PS between 1-stage and 2-stage surgery (P < 0.5). The mean ISQ values in the non-augmentation group were higher than in the augmentation group for both PS and SS (P < 0.01). A weak positive correlation was observed between cortical bone thickness and implant stability for both PS and SS in all cases (P < 0.01). CONCLUSIONS: Based on the present study, the ISQ may be affected by implant position site, the use of a bone graft, and cortical bone thickness before implant therapy.
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Humans , Dental Implants , Maxilla , Osseointegration , Retrospective Studies , TransplantsABSTRACT
<p><b>OBJECTIVE</b>This study aimed to explore the relationship among gingival thickness (GT), underlying alveolar bone thickness (BT), and sagittal root position in the maxillary anterior measured by cone-beam computed tomography (CBCT). The theoretical foundation was applied to aesthetic dentistry, implant treatment planning, and therapeutic effect assessment.</p><p><b>METHODS</b>A total of 40 young volunteers with healthy periodontal status were involved in this research [16 males and 24 females aged 23-34 years with a mean age of (26.30±2.29) years]. Three records were measured by CBCT. GT was measured at the cemento-enamel junction level. Buccal BT was measured at three locations: 1, 3, and 5 mm below the alveolar crest, along the sagittal angle between the long axis of teeth, and along the long axis of the respective alveolar bone.</p><p><b>RESULTS</b>The average GT and alveolar BT thicknesses were (1.08±0.34) mm and (0.79±0.29) mm, respectively. The average angle between teeth and alveolar bone was 18.01°±8.96°. BT was positively associated with GT (r=0.293, P=0.001). The BT of canine was positively associated with the angle between teeth and alveolar bone (r=0.457, P=0.003).</p><p><b>CONCLUSIONS</b>BT was relatively thin. An angle was found between the long axis of teeth and that of the alveolar bone. BT was positively associated with GT. An accurate diagnosis of GT, underlying alveolar BT, and sagittal root position in the maxillary anterior is necessary before implant surgery to devise an appropriate implant treatment plan and achieve a predictable esthetic outcome.</p>
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Objective:To compare the alveolar cortical bone density and thickness of jaw bones between teenagers (12-18 years of age) and adults(19-48 years of age).Methods:Spiral computed tomographic images of 60 cases were obtained from the subjects with the ages of 12 to 48 years(27 Males and 33 females,35 teenagers and 25 adults).Buccal cortical bone thickness and density in Hounsfield units were measured at 12 interradicular sites and to a depth of 14 mm.Results:The alveolar cortical bone thicknesses and densities of the jaw bones significantly increased from the crest to base of alveolar crest.The average cortical bone thicknesses rangedfrom 1.0 to 1.5 mm in the anterior part of the jaw bones,1.1 to 1.8 mm in maxillary posterior area and 1.5 to 2.8 mm in the mandible posterior areas.The cortical bone thickness and density were greater in the mandible than in the maxilla(P ＜ 0.05).The thickness values did not show difference between males and females,between adolescents and adults.Higher values of bone density were found in the adults than in the teenagers(P ＜0.05).The highest bone density in the mandible posterior area of adults was observed,and the lowest bone density in the maxillary posterior area of adolescents.Conclusion:Alveolar cortical bone density of adolescents is lower than that of adults,especially in the maxilla posterior region.
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Objective To adopt the cone beam computed tomography(CBCT) to analyze the bone thickness of infrazygomatic crest with different vertical skeletal facial types in teenagers.Methods Sixty teenagers of skeletal class were collected,including each 20 cases of high angle,average angle and low angle.The CBCT scanning data of oral maxillofacial region were collected.The bone thickness at different coronary slices in buccal side of infrazygomatic crest region at 13,15,17 mm above the maxillary occlusal plane was measured.The measured data were analyzed statistically.Results The bone thickness of infrazygomatic crest was gradually thinned from down to up,and the difference was statistically significant(P＜0.05);the bone thickness(except 3 points at 13 mm from maxillary plane) at each measured point in the high,average and low angle groups showed the change trend of low angle ＞average angle＞high angle,the difference was not statistically significant(P＞0.05).Conclusion In teenagers,the bone thickness of infrazygomatic crest in skeletal class Ⅱ is gradually thinned from cranial direction and rearward,the high angle is thinnest and the low angle is thickest.
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Objective@#To provide some references of using miniscrew implants in clinical orthodontic treatment, the bone thickness of maxilla and mandible of different vertical facial type in adults with cone-beam CT (CBCT) was measured.@*Methods @#57 scanned patients were selected as subjects. Among them, 20 were included in the high-angle group, 22 in the normal-angle group, and 15 in the low-angle group. On volumetric images, we measured the buccal and palatal cortical bone thickness of maxilla, the buccal cortical bone thickness of mandible from canine to the second molar teeth at heights of 4.0 mm from cemento-enamel junction (CEJ). The mean of cortical bone thickness was compared between three groups.@*Results @#There were statistical differences among three different vertical facial groups in the cortical bone thickness (P<0.05). The high-angle group has the thinnest cortical bone while the low-angle group has the thickest.@*Conclusion @#Clinicians should be aware of the probability of thin cortical bone plates and the risk of miniscrew implant failures at maxillary posterior miniscrew implant sites in high-angle patients.
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Objective:To study the relationship between gingival thickness(GT)and the underlying alveolar bone thickness(BT)in maxillary anterior region and the distance from cemento-enamel junction(CEJ)to alveolar crest.Methods:30 young volunteers with healthy gingiva were included.GT was measured at 2mm below the CEJ,buccal BT were measured at 3 locations:2,4 and 6 mm below the alveolar crest respectively,the distance from CEJ to alveolar crest were measured by CBCT and clinical direct measure respectively. Results:The correlation coefficient (r)values between GT and BT at 2,4 and 6 mm below alveolar crest were 0.493,0.383 and 0.342 (P <0.001 )respectively,the r value between GT and the distance from CEJ to alveolar crest was -0.21 3(P <0.01 ).No statistically significant difference was observed between CBCT and clinical measurements(t =-0.521 ,P =0.603).Conclusion:There is positive correlation between GT and BT at 2,4 and 6 mm below alveolar crest and negative relation between GT and the distance from CEJ to alveolar crest.
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Objective:To investigate the stress distribution surrounding an implant under different thickness of cancellous bone and cortical bone,and to analyze the influence of thickness ratio and total thickness of bone tissues on the reliability of an implant.Methods:By using the commercial finite element method software Abaqus, a simplified three-dimensional model of a jawbone consisting of a cancellous bone,a cortical bone,an implant,and a ceramic crown was constructed,and then the computation was performed.Under the condition that the system was loaded by lateral and normal stresses, the influence of thickness ratio and total thickness of cancellous bone and cortical bone in the stress distribution surrounding the implant was studied,where the thickness ratios were 3∶1, 2∶1, 1∶1, 1∶2, and 1∶3;the total thickness were 0.5, 1.0, 2.0, 3.0 and 4.0 mm, respectively. Results:The maximum stresses on the cortical bone,the cancellous bone as well as the implant were all found to decrease with the increasing of the total thickness of cortical and cancellous bones,with a higher decreasing rate in the range between 0.5-2.0 mm and a lower decreasing rate between 2.0-4.0 mm. More importantly, the maximum value of stress in the cortical bone within the neck region of the implant was observed to increase dramatically via reducing the total thickness below 2 mm, while it was increased insignificantly when the total thickness was above 2.0 mm. Conclusion:The thickness ratio and the total thickness of cancellous bone and cortical bone have strong influence in the stress distribution surrounding the implant.In dental implantation surgery, the total thickness of cancellous bone and cortical bone should be at least 2 mm, and therefore 2 mm is an optimal value.
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OBJECTIVES: The purpose of this study was to evaluate the proximity of the mandibular molar apex to the buccal bone surface in order to provide anatomic information for apical surgery. MATERIALS AND METHODS: Cone-beam computed tomography (CBCT) images of 127 mandibular first molars and 153 mandibular second molars were analyzed from 160 patients' records. The distance was measured from the buccal bone surface to the root apex and the apical 3.0 mm on the cross-sectional view of CBCT. RESULTS: The second molar apex and apical 3 mm were located significantly deeper relative to the buccal bone surface compared with the first molar (p < 0.01). For the mandibular second molars, the distance from the buccal bone surface to the root apex was significantly shorter in patients over 70 years of age (p < 0.05). Furthermore, this distance was significantly shorter when the first molar was missing compared to nonmissing cases (p < 0.05). For the mandibular first molars, the distance to the distal root apex of one distal-rooted tooth was significantly greater than the distance to the disto-buccal root apex (p < 0.01). In mandibular second molar, the distance to the apex of C-shaped roots was significantly greater than the distance to the mesial root apex of non-C-shaped roots (p < 0.01). CONCLUSIONS: For apical surgery in mandibular molars, the distance from the buccal bone surface to the apex and apical 3 mm is significantly affected by the location, patient age, an adjacent missing anterior tooth, and root configuration.
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Humans , Apicoectomy , Cone-Beam Computed Tomography , Molar , ToothABSTRACT
Objective:To investigate the labial(buccal)bone thickness at alveolar crest zone and alveolar crest height of the maxil-lary anterior teeth and premolars of young adults with normal occlusion.Methods:The alveolar bone of the anterior teeth and premo-lars of 67 eligible Han national young volunteers was scanned by CBCT.Then the facial bone thickness and the distance between the facial alveolar crest and Cemento-enamel Junction(CEJ)of the anterior teeth and premolars were measured and analyzed after recon-struction.Results:The distance between labial (buccal)crest and labial (buccal)CEJ of the maxillary first premolars was the lar-gest(P <0.05);there was a negative correlation between the labial(buccal)crest height and the facial alveolar bone thickness at 2 mm from CEJ toward root derection[(P <0.05),0.6 <|r|<0.8].Conclusion:The labial (buccal)crest of the first premolars was higher than that of other teeth in maxillary aesthetic zone.At alveolar crest zone,when the labial (buccal)bone was thinner,the dis-tance between labial (buccal)crest and labial (buccal)CEJ was larger,and the implant aesthetic risk is higher.
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Objective To quantitatively evaluate the thickness of the buccal cortical bone in the posterior region of the maxillary for orthodontic micro‐implants in children .Methods Forty children (20 males and 20 females) in permanent dentition with Class Ⅱdivision 1 malocclusion were selected .The maxillary posterior alveolar bones of the subjects were scanned and reconstructed by cone‐beam computed tomography (CBCT) .The thickness of the cortical bone between the dental roots of the second upper premolar and the first upper molar at the height of 3 ,4 ,5 ,6 ,7 ,8 ,9 mm from the alveolar crest were determined .The data were analyzed sta‐tistically .Results The thickness of the cortical bone between the second upper premolar and the first upper molar was minimum at the height of 4 mm from the alveolar crest(P<0 .05) .The thickness of the cortical bone increased along with the distance increas‐ing from the alveolar crest at the height of 5 mm .The cortical bones in male were significantly thicker than those in female at the height of 7 ,8 ,9 mm (P<0 .05) .Conclusion The thickness of the buccal corticalbone in children in permanent dentition with ClassⅡ division 1 malocclusion changes with the measured vertical position .Micro‐implant anchorage is better to be placed in the area with a distance of 5 mm from the alveolar crest .
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OBJECTIVE: To assess the labial and lingual alveolar bone thickness in adults with maxillary central incisors of different inclination by cone-beam computed tomography (CBCT). METHODS: Ninety maxillary central incisors from 45 patients were divided into three groups based on the maxillary central incisors to palatal plane angle; lingual-inclined, normal, and labial-inclined. Reformatted CBCT images were used to measure the labial and lingual alveolar bone thickness (ABT) at intervals corresponding to every 1/10 of the root length. The sum of labial ABT and lingual ABT at the level of the root apex was used to calculate the total ABT (TABT). The number of teeth exhibiting alveolar fenestration and dehiscence in each group was also tallied. One-way analysis of variance and Tukey's honestly significant difference test were applied for statistical analysis. RESULTS: The labial ABT and TABT values at the root apex in the lingual-inclined group were significantly lower than in the other groups (p < 0.05). Lingual and labial ABT values were very low at the cervical level in the lingual-inclined and normal groups. There was a higher prevalence of alveolar fenestration in the lingual-inclined group. CONCLUSIONS: Lingual-inclined maxillary central incisors have less bone support at the level of the root apex and a greater frequency of alveolar bone defects than normal maxillary central incisors. The bone plate at the marginal level is also very thin.