Identification of the mandibular landmarks in a pediatric population

Objectives: The aim of this study was to determine and compare the reliability to accomplish of common mandibular landmarks and to determine the incidence of incisive canals, anterior looping, and lingual foramina in children from panoramic and CBCT images. Study Design: Panoramic and CBCT images from 100 children and adolescent patients were randomly selected. In order to grade the visibility of mandibular anatomical landmarks, a four-point rating scale was used. Results: In panoramic images, the mandibular canal could be observed in 92.5% of cases, with good visibility in 12.0%. The mental foramen could be observed in 44.5% of cases, while none had good visibility. Anterior looping of the mental nerve was present in 16.5% of the cases, and none had good visibility. An incisive canal could be identified in 22.5% of cases, with only 1.5% showing good visibility. The lingual foramen could be visualized in 61.0% of cases, with good visibility in 6%. In CBCT images, the mandibular canal, the mental foramen, and the lingual foramen could be observed in 100% of the cases, with good visibility in 51.0%, 98.5%, and 45.0% of cases, respectively. Anterior looping of the mental nerve was present in 26% of cases, with 2% having good visibility. An incisive canal could be identified in 49.5% of cases, with only 75% showing good visibility. Conclusions: This study confirms the applicability of CBCT images to visualize critical structures in children. Key words:Panoramic radiography, cone beam computed tomography, anatomical landmark.     

Comparative analysis of mandibular anatomical variations between panoramic radiography and cone beam computed tomography

Purpose

The objective of this study is to compare the ability of panoramic radiography and cone beam computed tomography (CBCT) in detecting anatomical variations of the mandibular canal and mental foramen.

Methods

One hundred twenty-seven preoperative panoramic and CBCT images were evaluated. Two oral and maxillofacial radiologists investigated the presence of bifid mandibular canals and/or additional mental foramina on the right, left, or both sides of the mandible. Intra- and interobserver reliability was determined using Cohen’s kappa coefficient. McNemar’s test compared the prevalence of mandibular anatomical variations between panoramic radiography and CBCT. The significance level was set at 0.05.

Results

Additional mental foramen and bifid mandibular canal were detected in 1.2 and 7.4 % of the panoramic radiographs and 7.4 and 9.8 % of the CBCT images, respectively. The incidence of anatomical variations on the mandibular canal was not significantly different between both imaging modalities (P?>?0.05).

Conclusions

Although CBCT provides better viewing of anatomical structures, including location, shape, and relationship with the surrounding area, panoramic radiography is a conventional imaging modality that can be used in the study of the bifid mandibular canals.     

Evaluation of the visibility and the course of the mandibular incisive canal and the lingual foramen using cone‐beam computed tomography

Objectives: To assess the visibility and the course of the incisive canal and the visibility and the location of the lingual foramen using cone‐beam computed tomography (CBCT). Methods: In total, 100 CBCT examinations of patients for preoperative planning were used for this study. The examinations were taken using the NewTom 3G CBCT unit, applying a standardized exposure protocol. Image reconstruction from the raw data was performed using the NewTom software. Three experts were asked to assess the visibility of the incisive canal using a four‐point rating scale. The position of the incisive canal was recorded in relation to the lower, buccal and lingual border of the mandible using the application provided by the CBCT software. Results: The incisive canal was definitely visible in 83.5% of the scans and the mean endpoint was approximately 15 mm anterior to the mental foramen. The mean distance from the lower border of the mandible was 11.5 mm and its course was closer to the buccal border of the mandible in 87% of the scans. The lingual foramen was definitely visible in 81% of the scans. Conclusions: The high detection rate of the incisive canal and the lingual foramen in the anterior region of the mandible using CBCT indicates the potentional high preoperative value of CBCT scan for surgical procedures in the anterior mandible. To cite this article :
Makris N, Stamatakis H, Syriopoulos K, Tsiklakis K, van der Stelt PF. Evaluation of the visibility and the course of the mandibular incisive canal and the lingual foramen using cone‐beam computed tomography.
Clin. Oral Impl. Res. 21 , 2010; 766–771.
doi: 10.1111/j.1600‐0501.2009.01903.x     

Mandibular Incisive Canal: Cone Beam Computed Tomography

Purpose: Panoramic radiography is often used to analyze the anatomical structure of the teeth, jaws, and temporomandibular joints. Cone beam computed tomography (CBCT) imaging allows multiple axial slices of the image to be obtained through these anatomical structures. The aim of this study was to assess CBCT compared with panoramic radiography to verify the presence, location, and dimensions of the mandibular incisive canal. Materials and Methods: CBCT scan images and panoramic radiographs of 89 subjects were compared for the presence of the mandibular incisive canal, its location, size, and anterior‐posterior length. The distance between the incisive canal and the buccal and lingual plate of the alveolar bone, and the distance from the canal to the inferior border of the mandible and the tooth apex were also measured. A paired t‐test was used to calculate any significant difference between the two imaging techniques. Results: Eighty‐three percent of the CBCT scans showed the presence of the incisive canal, as did 11% of the panoramic radiographs. The range of the incisive canal diameter, as seen in the CBCT scans, was from 0.4 × 0.4 mm to 4.6 × 3.2 mm. The mean length of the canal was 7 ± 3.8 mm. The distance from the inferior border of the mandible to the canal was 10.2 ± 2.4 mm, and the mean distance to the buccal plate was 2.4 mm. The apex–canal distance (in dentate subjects) was 5.3 mm. Conclusion: The presence, location, and dimensions of the mandibular incisive canal are better determined by CBCT imaging than by panoramic radiography.     

基于锥形束CT影像对下颌管解剖变异的系统评价

目的 基于锥形束CT(cone beam computed tomography,CBCT)影像进行解剖学研究的系统评价,以评估下颌管变异及其解剖学发生率.方法 在PubMed、Cochrane、CNKI数据库中搜索2005年1月至2019年12月关于成年人群下颌管解剖变异的相关文章,并采用随机效应模型对其进行分析.通...     

Diagnostic accuracy of cone-beam CT compared with panoramic images in predicting retromolar canal during extraction of impacted mandibular third molars

Objectives: The clinical significance of the existence of a retromolar canal and of its neurovascular content is not yet clear.The aim of the present study was to assess the visibility, diameter and course of the mandibular retromolarcanal (MRC) using cone beam computed tomography (CBCT) scan -had been taken for pre-operative radiographic evaluation of impacted mandibular third molars- compared to panoramic radiographs. Study Design: Subjects eligible for study enrollment were those who underwent preoperative CBCT scan for the extraction of impactedmandibular third molars were determined to be extremely close to the mandibular canal on panoramic radiographs. Radiographs were screened for the presence and course of retromolar canals, and linear measurements. Results: 947hemimandibles in 632 patients were examined.A total of 253 MRCs (144 left, 109 right) were detected with CBCT images (26.7%). Only 29 of these canals were also seen on the corresponding panoramic radiographs. Most MRCs had a vertical course (type VI, 28.46%), followed by slightly curved (type I, 26.09%). The visibility of the MRC on the OPGs, according to the increase in the diameter, was not statistically significant for both sides (p>.05).Statistically difference were found for the width at the point of origin from the mandibular canal (p: .037), the mean distance from the MRC to the second molar (p: .042) and height of MRC when compared the gender. Conclusions: The findings suggest that the MRC isn’t a rare anatomical structure. This study therefore clearly establishes the incidence and importance of the MRC. The detection of the presence of the MRC using CBCT may be crucial for extraction of mandibular third molars. Key words:Accessory innervation, cone beam computed tomography, mandibular anatomy, panoramic radiographs, retromolar canal, retromolar foramen.     

Classification of the lingual foramina and their bony canals in the median region of the mandible: cone beam computed tomography observations of dry Japanese mandibles

Objectives  We investigated the lingual foramina and their bony canals in the median region of the mandible using cone beam computed tomography (CBCT). Methods  Sixty-eight dry Japanese mandibles were studied. The mandibles were set parallel to the inferior mandibular plane, and CBCT images of the medial region were obtained. The lingual foramina in the medial region (MLFs) were classified as being on the midline superior to the mental spine (s-MLF), on the midline inferior to the mental spine (i-MLF), or beside the midline (a-MLF). The frequency, location, and angulation of each foramen and its canal were measured from the CBCT images. Results  The s-MLF, i-MLF, and a-MLF occurred with frequencies of 86.8%, 83.8%, and 42.6%, respectively. The respective distances from the inferior mandibular plane were 11.4, 4.4, and 5.7 mm, while the vertical angulation of the canals was 77.5°, 114°, and 114°. A significant relationship was observed between the foramen height and canal angulation. On dissecting six cadaver mandibles, the sublingual artery was identified in s-MLFs and i-MLFs, while anastomosis of the sublingual and submental arteries was found in the a-MLFs. Conclusions  MLFs were observed frequently, and we confirmed that arteries passed though their canals. Since s-MLFs were the most frequent, contained the artery, and were located superior to the other MLFs, clinicians should identify such foramina from preoperative images.     

下颌神经管在CBCT与曲面体层片上的一致性评价

目的:对比分析下颌神经管在CBCT与曲面体层片上可见性的一致性,探讨影响下颌神经管在图像上可见性的非病变因素。方法:选取2013年12月~2014年2月期间在华西口腔医院同时拍摄了CBCT与曲面体层片的患者92例,由2位放射科医师同时观察患者的CBCT片与曲面体层片。把CBCT及曲面体层片上的下颌神经管从颏孔至下颌升支前缘处平分为1、2、3三个区域,分为0、1、2、3四个等级的分对下颌神经管的可见性进行评分。结果:2位医师间的内部一致性检验符合标准。CBCT上,区域1平均得分为2.120,区域2为2.337,区域3为2.533;曲面体层片上,区域1平均得分为1.772,区域2为1.973,区域3为2.207。越往后区域可见性越高。结论:CBCT对下颌神经管的可见性显著高于曲面体层片,仅有1％的下颌神经管在曲面体层片上可见,在CBCT上不可见。下颌神经管的可见性与年龄呈相关性,年龄越大,可见性越低。     

下颌管及其分支与下颌第三磨牙关系的影像学观察

目的:利用椎形束CT(CBCT)及全景片观察下颌管及其分支在下颌第三磨牙区域的情况。方法 :对179名患者的216颗第三磨牙进行CBCT及全景片检查。在全景片及CBCT上观察下颌管及其分支在第三磨牙区域走向及与第三磨牙的关系。结果:全景片上观察到有4例下颌管有分支,CBCT观察到有22例有分支;下颌管分支与第三磨牙的关系:A类有8例,B类有6例,C类有2例,D类有6例,其中,分支位于第三磨牙颊侧的有7例,舌侧的有6例,位于第三磨牙牙根下方的有9例。结论:利用CBCT可以对下颌管及下颌第三磨牙的空间位置进行更好地观察。CBCT对下颌管分支有更高的检出率。     

Are panoramic images reliable in planning sinus augmentation procedures?

Objective: The inherent deformation and two‐dimensional nature of panoramic radiographs jeopardise their interpretation and quantitative measurements. This study aims to estimate the degree of underestimation of available mesio‐distal bone in the premolar area (comparing panoramic radiographs with multi‐slice/cone‐beam computer tomography [CT]) to determine the prevalence, width, length and position of the bony canal [artery] in the lateral sinus wall and to explore the prevalence, width and length of another (newly detected) bony canal at the palatal aspect of the upper canine. Material and methods: The distance between the distal side of the canine/first premolar and the mesial side of the first molar or the anterior wall of the maxillary sinus was measured on panoramic radiographs and corresponding multi‐slice/cone‐beam CT images (65 patients). Measurements were made at apical, mid‐radicular and crestal regions, parallel to the occlusal plane. The presence and dimensions of the two above‐mentioned intra‐osseous canals were verified on multi‐slice CT scans (144 patients) using reformatted cross‐sectional images and/or axial slices. Results: For all 65 patients, panoramic radiographs underscored the mesio‐distal distance of available bone in the upper premolar region (mean 2.9 mm, range 0.1–7.5 mm). An intra‐osseous canal in the lateral maxillary sinus wall was clearly visible in 49.5% of the cases (mean diameter 1.4 mm). In the canine region, a bony canal was obvious in 32.9% of the cases, with a mean diameter of 1.23 mm. For both canals, there was no correlation between diameter and patient's age. Conclusions: Based on the present data, cone‐beam CT imaging can be recommended for visualising anatomical structures during planning of sinus augmentation procedures. To cite this article:
Temmerman A, Hertelé S, Teughels W, Dekeyser C, Jacobs R, Quirynen M. Are panoramic images reliable in planning sinus augmentation procedures?
Clin. Oral Impl. Res. 22 , 2011; 189 –194.
doi: 10.1111/j.1600‐0501.2010.02000.x     

Comparison between panoramic radiography and cone-beam computed tomography findings for assessment of the relationship between impacted mandibular third molars and the mandibular canal

Objectives

The aim of this study was to assess the relationship between the mandibular canal and impacted mandibular third molars using cone-beam computed tomography (CBCT) and to compare the CBCT findings with panoramic radiographic signs.

Methods

This study involved a retrospective radiographic review of 781 impacted third molars in 500 patients who showed a close relationship between the mandibular canal and the third molars on panoramic radiographs. Panoramic radiographic images were evaluated for interruption of the white line, darkening of the roots, diversion of the mandibular canal/roots, and narrowing of the mandibular canal/roots. The authors evaluated CBCT images to determine the course of each canal and its proximity to the roots. The statistical correlations between the panoramic radiography and CBCT findings were examined using the Chi-square test and Fisher’s exact test.

Results

Cone-beam computed tomography examination showed that darkening of the roots and deviation of the canal associated with the absence of corticalization between the mandibular third molar and the mandibular canal on panoramic radiographs were statistically significant, both as isolated findings and in association. No significant associations were observed for the other panoramic radiographic findings, either individually or in association.

Conclusions

The results of this study suggest that darkening of the roots, deviation of the mandibular canal, and interruption of the white line observed on panoramic radiographs, both as isolated findings and in association, were effective for determining the risk relationship between the roots and the mandibular canal, requiring three-dimensional evaluation of such cases.     

下颌骨颏孔前区解剖结构的锥形束CT研究

目的 通过锥形束CT（CBCT）分析下颌骨颏孔前区颌骨内的重要解剖结构,提出下颌颏孔前区种植相关手术的安全区域。方法 选取104例患者的CBCT图像资料,观察颏管、下颌切牙管、下颌舌侧管和舌侧孔。对数据进行描述性分析,计算均数和标准差。采用SPSS 19.0软件包对数据进行统计学分析。结果 颏管的发生率为55.29%,平均长度为1.12 mm。舌侧孔及舌侧管的发生率为94.23%,直径平均值为1.77 mm。从下颌第二前磨牙至中切牙,下颌切牙管距唇（颊）侧骨板的距离均小于距舌侧骨板的距离。结论 建议在颏孔前区种植手术或者颏部取骨时,以双侧颏孔前缘6 mm以上,唇侧骨厚度（取骨时）3 mm以内为安全界限;而在下颌前牙区种植时,种植体长度不超过14 mm。     

Three-dimensional images contribute to the diagnosis of mucous retention cyst in maxillary sinus

Objective: To evaluate the detection of mucous retention cyst of maxillary sinus (MRCMS) using panoramic radiography and cone beam computed tomography (CBCT). Study Design: A digital database with 6,000 panoramic radiographs was reviewed for MRCMS. Suggestive images of MRCMS were detected on 185 radiographs, and patients were located and invited to return for follow-up. Thirty patients returned, and control panoramic radiographs were obtained 6 to 46 months after the initial radiograph. When MRCMS was found on control radiographs, CBCT scans were obtained. Cysts were measured and compared on radiographs and scans. The Wilcoxon, Spearman and Kolmorogov-Smirnov tests were used for statistical analysis. The level of significance was set at 5%. Results: There were statistically significant differences between the two methods (p<0.05): 23 MRCMS detected on panoramic radiographs were confirmed by CBCT, but 5 MRCMS detected on CBCT images had not been identified by panoramic radiography. Eight MRCMS detected on control radiographs were not confirmed by CBCT. MRCMS size differences from initial to control panoramic radiographs and CBCT scans were not statistically significant (p= 0.617 and p= 0.626). The correlation between time and MRCMS size differences was not significant (r = -0.16, p = 0.381). Conclusion: CBCT scanning detect MRCMS more accurately than panoramic radiography. Key words:Mucous cyst, maxillary sinus, panoramic radiograph, cone beam computed tomography.     

Diagnostic agreement of conventional and inverted scanned panoramic radiographs in the detection of the mandibular canal and the mental foramen

The aim of this study was to evaluate the diagnostic agreement of conventional panoramic radiographs and their inverted scanned images in the detection of the mandibular canal and mental foramen. A total of 77 panoramic radiographs obtained from the files of totally edentulous patients were used. Digitization was done by means of a scanner with brightness and contrast adjustment, as well as image inversion. The extension of mandibular canal was divided into anterior, middle, and posterior regions, and the presence of a radiopaque line that characterized the mandibular canal was classified according to a 5-point confidence scale. The mental foramen was classified in 4 types: continuous, separated, diffuse, and unidentified. Both conventional and inverted scanned panoramic radiographs were evaluated by 3 calibrated implantologists at 2 distinct moments with a minimum interval of 10 days between them. Intraexaminer agreement was evaluated by Kappa statistics by point and by 95% confidence interval. Because the intraexaminer level of agreement was low, interexaminer agreements could not be carried out. The results showed a substantial (in 2 situations), moderate (in 16 situations), and fair (in 18 situations) intraexaminer agreement for mandibular canal and a substantial (in 1 situation), fair (in 1 situation), and moderate (in 10 situations) intraeaminer agreement for mental foramen. There were no statistically significant differences in most instances. In conclusion, the diagnostic agreement of conventional and inverted scanned panoramic radiographs for detection of mandibular canal and mental foramen was low.     

A retrospective radiographic evaluation of the anterior loop of the mental nerve: Comparison between panoramic radiography and cone beam computerized tomography

Objectives: To compare the prevalence and the length of mental loop, measured with panoramic radiography (PR) and cone beam computerized tomography (CBCT). Material and Methods: PG and CBCT images where analyzed by a single calibrated examiner to determine the presence and the position of the mental foramen (MF), its distance to the lower mandible border, the anterior length of the mental loop (ML) and the bone quality in 82 PR and 82 CBCT. Results: ML was identified in 36.6 % of PR and 48.8 % of CBCT. PR showed a magnification of 1.87 when compared to CBCT. The mean of anterior extension of the inferior alveolar nerve and the distance to the inferior border of the mandible was higher for PR (2.8 mm, sd 0.91 mm on the PR , range 1.5 to 4.7 mm and 1.59, sd 0.9 on the CBCT ,range 0.4 to 4.0 mm) Conclusions: There is a magnification in PR images with respect to those of CBCT. The differences between CBCT and PR with regards to the identification and length of the ML are not statistically significant. Identification and accuracy measurements of ML did not depend on the bone quality. Considering that two dimensional imaging provides less accurate and reliable information regarding the anterior loop, a CBCT scan could be recommended when planning implant placement in the anterior region. Key words:Mental loop, mental nerve, mental canal, preoperative implant planning, panoramic tomography, cone beam computerized tomography.     

Detection and characterization of the accessory mental foramen using cone-beam computed tomography

Objective: This study aimed to investigate the frequency and characteristics of accessory mental foramina (AMFs) and their bony canals in a selected Chinese population using cone-beam computed tomography (CBCT).

Materials and methods: Reconstructed CBCT images of the mandible in 784 Chinese patients (305 males and 479 females) were retrospectively analysed to identify the AMF. The presence, dimension and location of the AMF as well as the origin and course of the associated bony canal were evaluated and classified. Variations in these characteristics were analysed according to gender, side and age.

Results: A total of 66 AMFs were found in 57 (7.3%) of the 784 patients. The frequency of AMFs was significantly influenced by gender and side of the mandible (p?Conclusions: This study presents a considerable frequency of AMFs in a Chinese population. The high-position AMF and the associated bony canal coursing in the oblique upward direction appear frequently. Thus, clinicians should be alert to the presence of the AMF to avoid neurovascular complications especially when dental procedures require periosteum detachment and implant insertion in the mental region.     

Assessment of the appearance,location and morphology of mandibular lingual foramina using cone beam computed tomography

Objectives: To investigate the appearance, location and morphology of mandibular lingual foramina (MLF) in the Chinese Han population using cone beam computed tomography (CBCT). Methods: CBCT images of the mandibular body in 200 patients (103 female patients and 97 male patients, age range 10–70 years) were retrospectively analysed to identify MLF. The canal number, location and direction were assessed. Additionally, the diameter of the lingual foramen, the distance between the alveolar crest and the lingual foramen, the distance between the tooth apex and the lingual foramen and the distance from the mandibular border to the lingual foramen were examined to describe the MLF characteristics. Gender and age differences with respect to foramina were also studied. Results: CBCT can be utilized to visualise lingual foramina. In this study, 683 lingual foramina were detected in 200 CBCT scans, with 538 (78.77%) being ≤1 mm in diameter and 145 (21.23%) being >1 mm. In total, 85.07% of MLF are median lingual canals (MLC) and 14.93% are lateral lingual canals (LLC). Two typical types of lingual foramina were identified according to their relationship with the tooth apex. Most lingual foramina (74.08%) were found below the tooth apex, and those above the tooth apex were much smaller in diameter. Male patients had statistically larger lingual foramina. The distance between the lingual foramen and the tooth apex changed with increasing age. Conclusions: Determination of the presence, position and size of lingual foramina is important before performing a surgical procedure. Careful implant-prosthetic treatment planning is particularly important in male and/or elderly patients because of the structural characteristics of their lingual foramina.Key words: Lingual foramen, lingual vascular canal, mandible, cone-beam CT     

下颌阻生第三磨牙与下颌管位置的曲面体层X线片和锥形束CT观察

目的 观察分析在曲面体层x线片上人群中下颌阻生第三磨牙(impacted mandibular third molar,IMTM)与下颌管位置关系的类型,并对二者关系密切的病例行锥形柬CT(conc beam computed tomography,CBCT)检查,了解二者实际位置关系.为临床制定IMTM拔除手术方案提供参考.方法 观察390例(645侧)曲面体层X线片,将IMTM与下颌管的位置关系的影像分为3种类型:①无接触类,二者影像无任何重叠或接触;②点状接触类,二者之间影像仅为点状接触;③部分重叠类,二者影像部分重叠或有较大范围接触.统计3种类型的构成比.曲面体层X线片显示IMTM与下颌管影像呈部分重叠或较大范围接触的部分病例行CBCT检查,观察曲面体层X线片IMTM与下颌管关系密切者中,IMTM实际突破下颌管壁所占的比例.结果 390例(645侧)IMTM的曲面体层X线片影像中,无接触类441侧(68.4%);点状接触类149侧(23.1%);部分重叠类55侧(8.5%).对31例(50侧)曲面体层X线片上显示IMTM与下颌管呈部分重叠或较大范围接触的CBCT检查发现,25侧(50%)IMTM突破下颌管壁.结论 ①曲面体层X线片可以排除90%以上IMTM与下颌管关系不密切的病例;②曲面体层X线片IMTM与下颌管影像呈部分重叠或较大范围接触表现的病例有必要行CBCT进一步检查.     

The use of cone beam CT for the removal of wisdom teeth changes the surgical approach compared with panoramic radiography: a pilot study

This prospective study evaluated the role of cone beam computed tomography (CBCT) in the treatment of patients with impacted mandibular third molars at increased risk of inferior alveolar nerve (IAN) injury. Subjects with an increased risk of IAN injury, as diagnosed on panoramic radiographs, were enrolled in this study and underwent additional CBCT imaging. Two oral maxillofacial surgeons independently planned the surgical technique and estimated the risk of IAN injury on panoramic radiographs and on CBCT images. A test of symmetry and the McNemar test were executed to calculate the differences between the two imaging modalities. The study sample comprised 40 patients (mean age 27.6 years) presenting 53 mandibular third molars. Risk assessment for IAN injury based on panoramic radiography compared with CBCT imaging differed significantly (P < 0.005). After reviewing the CBCT images, significantly more subjects were reclassified to a lower risk for IAN injury compared with the panoramic radiograph assessments. This change in risk assessment also resulted in a significantly different surgical approach (P < 0.03). The results of this study show that CBCT contributes to optimal risk assessment and, as a consequence, to more adequate surgical planning, compared with panoramic radiography.     

锥形束CT中下颌第三磨牙与下颌管的关系及其与阻生类型的相关性分析

目的:研究在曲面断层片上表现为下颌管与下颌第三磨牙影像重叠的患者,其二者在锥形束CT(CBCT)上的位置关系,为临床风险评估提供参考。方法:研究184颗(146例患者)在曲面断层片上表现为与下颌神经管有影像重叠的下颌第三磨牙,在CBCT上其牙根与下颌神经管的位置关系。分析两者之间位置关系与阻生类型、性别、曲面断层片上下颌神经管骨白线是否可见的相关性。测量下颌第三磨牙与下颌神经管接触的患者其接触的长度及宽度,分析接触长度、宽度与牙根和下颌神经管相对位置的相关性。结果:CBCT图像上下颌第三磨牙与下颌神经管之间是否接触,与其在颌骨内的深度相关,低位阻生接触可能大(P=0.002),与性别相关,女性多(P=0.020);当曲面断层片中下颌神经管骨白线不可见时,接触可能大(P=0.001)。当下颌神经管与牙根舌侧接触时,接触的长度、宽度可能较大。结论:CBCT与曲面断层片相比能更好地体现下颌阻生第三磨牙与下颌神经管的关系,提供更准确的术前风险评估。