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.     

四川地区成年人群中分叉下颌管的锥形束CT研究

目的 统计分析四川地区成年人群中分叉下颌管发生概率,并总结下颌管各分叉类型及发生率与走行方式和各自形态特征。方法 根据纳入和排除标准收集500例患者（共计1 000侧下颌骨）的锥形束CT（CBCT）影像资料,对所收集的资料进行观察分析,并记录数据,对下颌神经管分支的类型及其特征进行归纳和分类。结果 500例患者中分叉下颌管的发生率为13.8%（69/500）,共发生于92侧（9.2%）的下颌骨中。其中最常见的类型为磨牙后管,其次为向牙根及颊舌向分支,最少见的类型为向前走行的分支。分支的平均直径和长度分别为0.90、9.39 mm。结论 本研究使用CBCT作为研究手段,得出的分叉下颌管在四川地区成年人群中的发生率要明显高于以前报道的使用全景片作为研究手段的研究;并且CBCT对下颌管及其分支的三维走行及形态特征的表现能力优于全景片。     

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.     

Bifid mandibular canal in Japanese

The location and configuration of mandibular canal variations are important in surgical procedures involving the mandible, such as extraction of an impacted third molar, dental implant treatment, and sagittal split ramus osteotomy. We report 3 Japanese patients with bifid mandibular canals using panoramic radiograph and multi-slice helical computed tomography (CT) images. In 2 of the 5 sides, the bifid mandibular canal was suggested on panoramic radiograph. The bifid mandibular canal had a short and narrow upper canal toward the distal area of the second molar in 4 sides, and a short and narrow lower canal toward the distal area of second molar in 1 side, as revealed on reconstructed CT images. Since the location and configuration of mandibular canal variations are important in surgical procedures involving the mandible, they should be carefully observed using reconstructed CT images.     

Prevalence of bifid and trifid mandibular canals with unusual patterns of nerve branching using cone beam computed tomography

Lack of knowledge concerning the inferior alveolar canal anatomical variations had proven to increase the incidence of surgical complications, so the study aimed to assess the configuration and prevalence of bifid and trifid mandibular canals using cone beam CT in Egyptian subpopulation. Cone beam CT scans of 278 patients (530 hemi-mandibles) were included in the study, in which bifid and trifid mandibular canals or any other branching patterns were recorded and evaluated. Bifid canals were categorized following Naitoh classification, and the diameter of the main mandibular and accessory canals was measured. Bifid canals were detected in 181 canals (34%) while trifid canals in 46 canals (8.7%). Upon classifying the bifid canals, 78 canals showed forward type, 40 retromolar type, 33 dental type, and 7 canals showed buccolingual type. Two special bifid canals subtypes were reported in 23 canals and nine distinct patterns of trifid canals were reported in our study. In addition, unusual patterns of canal branching were reported in 5 cases. The mean diameter of the accessory canals was 1.18?±?.54 mm and the main canal was 3.98?±?1.31 mm. This study reported a high prevalence (54%) of canal branching, which reinforces the importance of cone beam CT in pre-surgical planning.

     

基于CBCT的西南地区汉族人双下颌管形态学研究

目的：利用CBCT分析西南地区汉族人双下颌管发生的概率及各型双下颌管的形态学特征,为与之密切相关的口腔临床操作提供参考。方法：选择 2014-2016年期间于自贡市第四人民医院口腔科就诊拍摄CBCT的汉族患者300例,观察患者有无双下颌管,描述其形态学特征并进行统计学分析。结果：西南地区汉族人双下颌管的发生率为19.33%。其中,磨牙后管占比最高（58.75%）,其次为根尖管（23.75%）和前行管（15.00%）,颊舌向管最少（2.50%）。结论：基于CBCT的研究表明西南地区汉族人双下颌管有较高的发生率,并且各型分支存在形态学差异,临床工作中需重视其影响。     

不同角度根尖片对诊断下颌第一前磨牙多根管的作用

目的探讨联合应用平行和偏移投照根尖片在诊断下颌第一前磨牙多根管中的作用。方法选择临床上需要进行根管治疗的130人的132颗下颌第一前磨牙为研究对象,每颗患牙术前均需拍摄平行和偏移投照X线片,初步判断是否为多根管牙;术中配合使用根管显微镜用K锉探寻根管口及根管,使用手用镍钛锉进行根管预备,侧方加压技术充填根管。结果132颗下颌第一前磨牙中,术前平行和偏移投照x线片共初步诊断多根管牙41颗;平行投照诊断多根管牙16颗,偏移投照诊断多根管牙37颗,其中有12颗患牙2种投照方法均表现为多根管影像。两种投照方法诊断的下颌第一前磨牙多根管与在临床治疗中发现的多根管数一致,发现率为31．06％。结论平行和偏移投照X线片联合应用有助于提高下颌第一前磨牙多根管的发现率,从而减少临床遗漏根管的发生。     

Impacted mandibular canines

AIMS: The aim of the present study was to investigate the incidence of impacted mandibular canines, the associated pathology of these teeth, and to classify them. METHODS AND MATERIALS: This is a retrospective cohort study of 5022 panoramic radiographs taken of patients who presented to the Oral and Maxillofacial Surgery Service of the Faculty of Dentistry at Ataturk University in Erzurum, Turkey between January, 1998 and March, 2006. The panoramic radiographs and clinical data were reviewed. Observations were made on the status of missing permanent mandibular canines; retained deciduous canines; side and number of mandibular canines; sex and age of patients; and any other associated pathology or symptoms as well as treatment methods employed. RESULTS: The incidence of mandibular canine impaction is 1.29% in the 5022 individuals of this Turkish subpopulation. A total of 65 patients had impacted mandibular canines with 33 being females and 32 males. In this study 41 impacted mandibular canines were extracted. Twenty-three canines were attached to bonded buttons for orthodontic eruption purposes. After surgical exposure, one impacted canine was transplanted and the others were left in place for observation. CONCLUSIONS: Maxillary canine impaction is more frequent than mandibular canine impaction. Mandibular canine impaction incidence in this study was found higher than in the published literature to date. This result may be evidence of an actual increase of the number of impacted mandibular canine teeth among patients.     

Effect of bisphosphonate treatment on the jawbone: an exploratory study using periapical and panoramic radiographic evaluation

Objective

This cross-sectional study aimed to explore potential jawbone changes secondary to bisphosphonate (BP) treatment of osteoporosis using digital panoramic and periapical radiography.

Methods

Thirty-nine women, previously examined with dual-energy X-ray absorptiometry, were radiographed by digital panoramic and/or periapical radiography. On periapical radiographs, trabecular bone structure and fractal dimension analyses of the mandibular first molar and edentulous regions were performed. On panoramic radiographs, the mandibular cortical width (MCW) was calculated, and trabecular bone structure and fractal dimension analyses of the trabecular bone in the alveolar and basal bones were performed. The results were compared between patients treated or not treated with BP using linear regression analysis to adjust for potential confounding factors.

Results

The analyses of periapical and panoramic radiological images showed no statistical differences in the jawbones between groups after bisphosphonate use for mean intervals of 4.3 and 5 years; respectively. Although the mandibular cortical width on panoramic radiography was correlated with BP use, it was not noted to be statistically significant.

Conclusions

The trabecular parts of the alveolar and basal bones and the MCW were not significantly altered by BP treatment in patients with osteoporosis over 4.3–5 years, as detected by digital periapical and panoramic radiography. The low dosages of bisphosphonates used in the treatment of osteoporosis may explain this lack of change in MCW. Dental radiographs should not be considered as a method to monitor BP-induced jaw bone alterations among osteoporotic patients.

     

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.     

下颌管分支的锥形束CT观测研究

目的 基于锥形束CT（cone beam computed tomography，CBCT）研究下颌管分支的分布情况及相关数据，为临床实践提供指导和依据。方法 对400例（共800侧下颌骨）山西地区成年人，拍摄CBCT后对下颌管分支的出现情况及其长度、直径和角度进行测量分析，探究性别、左右侧及各年龄层对下颌管分支的影响。结果 400例患者中下颌管分支的发生率为40.75%（163/400），共发生于248侧（31.0%）下颌骨中。下颌管分支的分型中，磨牙后管、牙管、前行管和颊舌侧管的比例分别为45.97%、23.39%、28.63%和2.02%，下颌管分支的直径平均为（1.18±0.36）mm，长度平均为（12.58±4.72）mm，与下颌管主干的夹角平均为42.46°±18.14°。结论 山西地区成年人群的下颌管分支发生率较高，尤其在磨牙后区较常见，在行下颌后牙区外科手术前，建议拍摄CBCT预估风险，避免发生术中损伤导致严重的并发症。     

Variations in the normal anatomy of the inferior dental (mandibular) canal: a retrospective study of panoramic radiographs from 3612 routine dental patients.

A review of 3612 panoramic radiographys from routine dental patients indicates that the mandibular canals are usually, but not invariably, single and bilaterally symmetrical. The position of the canal varies with respect to the lower border of the mandible and the apices of the roots of the teeth and this excludes its use as a set reference point for prosthetic or orthodontic assessment. Three distinct varieties of supplemental mandibular canals, large enough to be seen on panoramic radiographs, are described.     

Prevalence of bifid mandibular condyle in a Turkish population

The aim of this study was to determine the frequency of bifid mandibular condyle (BMC) using panoramic radiographs supported by different radiographic techniques. A retrospective study was carried out by evaluating panoramic radiographs of 18,798 patients referred to the Department of Dentomaxillofacial Radiology. T-tests were used to compare the frequency of BMC between left and right sides and between female and male patients. In this study, 98 patients (0.52%) were found to have BMC. Of these patients, 51 (52%) were females and 47 (48%) were males. Of the 98 patients, 71 (72.4%) had unilateral and 27 (27.6%) had bilateral BMC. A total of 125 BMCs were found in 98 patients. No statistically significant differences were found between the right and left BMCs or between female and male patients (P > 0.05). Because symptoms associated with BMC are either absent or minimal, it is usually discovered as an incidental finding during routine radiographic examination. Different appearances of BMC can be seen on panoramic radiographs. The exact orientation of the condyles can only be determined using 3D imaging techniques. BMC may be a more frequent condition in the Turkish population.     

Bilateral bifid mandibular condyle: a case report

Bilateral bifid mandibular condyle is a rarely seen malformation. The aetiology of bifid condyle is not completely understood, although developmental anomaly, traumas, condylar fracture, teratogenic embryopathy and surgical condylectomy may all be causative factors. Although a few studies on human dried skulls tried to shed light on this entity it remains obscure. As most bifid condyle subjects have no complaint related to temporamandibular joint(TMJ), the cases are generally diagnosed through incidental radiographic findings. The case of a 54-year-old female is presented. In a panoramic radiograph obtained after a clinical examination, bilateral bifid mandibular condyle was observed. The open-closed lateral radiograph of the TMJ (obtained using the TMJ-specific program of the panoramic device) demonstrated duplication of the right and left condyles. In order to better evaluate the TMJ morphology and to eliminate pathologies such as fractures that might be missed with conventional radiographs, a computed tomography scan was also obtained. The joint head orientation was observed in the mediolateral direction. The case is discussed in the context of the relevant literature. Until large population-based studies are undertaken and further experimental studies are performed, bifid condyle will remain an incidental finding of anatomic variation rather than a clinically informative observation.     

Development and Validation of a Visually Explainable Deep Learning Model for Classification of C-shaped Canals of the Mandibular Second Molars in Periapical and Panoramic Dental Radiographs

IntroductionThe purpose of this study was to develop and validate a visually explainable deep learning model for the classification of C-shaped canals of the mandibular second molars in dental radiographs.MethodsThe periapical and panoramic images of 1000 mandibular second molars were collected from 372 patients. The diagnostic performance of the deep learning system using periapical and panoramic radiographs was investigated in respect to its ability to determine whether the second mandibular molar showed a C-shaped canal configuration. The assessment of the canal configuration of cone-beam computed tomographic volumes from 372 patients (740 mandibular second molars) was used as a gold standard.ResultsThe deep convolutional neural network algorithm model showed high accuracy in predicting the C-shaped canal variation among mandibular second molars in both periapical and panoramic images. The model demonstrated best results when using image patches including only the root portion of the tooth and when using both periapical and panoramic images for training (area under the curve [AUC] = 0.99). The model's diagnostic performance using only the root portion of the tooth (AUC: periapical = 0.98 and panoramic = 0.95) was similar to a specialist (AUC: periapical = 0.95 and panoramic = 0.96) and better than a novice general clinician (AUC: periapical = 0.89 and panoramic = 0.91). Both the specialist and general clinician showed better diagnostic performance when reading panoramic radiographs compared with periapical images.ConclusionsWith further optimization of the test data using a larger data set and improvements made in the model, a deep learning system may be expected to effectively diagnose C-shaped canals and aid clinicians in practice and education.     

经口内入路切除下颌骨良性肿瘤及同期血管化腓骨肌瓣精确重建下颌骨

目的： 首次介绍口内入路行下颌骨良性肿瘤切除和显微血管吻合的腓骨肌瓣即刻精确重建的经验。方法： 2018年1月—3月,对我科收治的4例下颌骨良性肿瘤患者行经口内入路的下颌骨节断性切除及显微血管吻合的腓骨肌瓣即刻重建术。3例术前行虚拟手术计划设计,并行钛板数字化压模成型。术中先在口内颊部显露面动、静脉并保护,按截骨导板完成下颌骨节断性切除和腓骨瓣塑形、钛板固定后,用导航验证重建下颌骨的位置。显微镜下将腓动脉与面动脉作端-端吻合,腓静脉与面静脉用微血管吻合器Coupler吻合。术后常规采用手提超声多普勒监测血管血流信号;术后1周复查全景片,检查重建下颌骨的位置。结果： 4例患者均顺利完成经口内入路的下颌骨节断性切除、腓骨重建,其中3例顺利完成口内显微血管吻合,1例因术区瘢痕、面静脉不理想而引至下颌下吻合。术后超声多普勒监测显示血流信号正常,口内及供区伤口均一期愈合。术中导航及术后全景片显示重建的下颌骨位置理想,咬合关系正常,面部外形对称,无面瘫及开口受限。结论： 经口内入路行下颌骨良性肿瘤的节断性切除及腓骨肌瓣精确重建和口内显微血管吻合是完全可行的,能够达到口外入路同样的效果,同时口外无瘢痕。     

X线曲面体层摄影下颌管显现情况的临床研究

目的 观察X线曲面体层摄影下颌神经管的显现率及冠根向直径，为种植手术提供指导。方法 选择种植义齿及牙周病曲面体层摄影片200例，反复测量曲面体层摄影片下颌神经管及孔的显现情况和冠根向直径并记录部位。结果 大部分下颌管可经曲面体层摄影显现，显现率和冠根向直径从后向前降低，双侧显现率经配对t检验无显著性差异（P＞0.05）。结论 X线曲面体层摄影下颌管及麂孔的显现率较高，适用于大部分种植义齿手术设计，少部分下颌管显现不清，应拍摄螺旋CT以明显下颌管的确切部位和走行，以减少对下牙槽神经的损伤的发生率。     

利用曲面断层片进行下颌骨测量的研究

目的 评价利用曲面断层片进行下颌骨测量的可行性.方法 分别测量51 例患者的曲面断层片和头颅侧位片上的下颌角、下颌升支长、下颌体长、下颌综合长几项指标,分析其相关性.结果 下颌角、下颌升支长、下颌体长度、下颌综合长的测量值在曲面断层片上与头颅侧位片上的相应指标呈显著相关.结论 在统一拍摄条件下,曲面断层片能够用做下颌骨的测量.     

曲面断层片在评价下颌骨生长发育时下颌骨线性指标的作用

目的 研究在X线全颌曲面断层片和头颅后前位片上下颌骨线距测量项目的相关性,探讨曲面断层片定量分析评价下颌骨发育的应用价值.方法 选取同一技师同时期拍摄的52例患者的全颌曲面断层片和头颅后前位X片,分别测量左右侧下颌骨升支高度、下颌体长度、下颌综合长度,对测量结果进行统计分析.结果 下颌骨升支高度和下颌综合长度在X线全颌曲面断层片和头颅后前位片上测量值间有明显相关性,而下颌体长度两测量值间尚未见明显相关性.结论 在严格控制拍摄条件下,曲面断层片可以进行下颌骨线性指标的测量来评价下颌骨生长发育.     

Relationship between the risk of mandibular angle fractures and the status of incompletely erupted mandibular third molars.

BACK GROUND: Several studies have shown the increased risk of mandibular angle fractures associated with incompletely erupted mandibular third molars. But only a few reports analysed in detail the relationship of the status of eruption of this tooth and this type of fracture. OBJECTIVES: The purpose of this study was to clarify the influence of the eruption status of incompletely erupted mandibular third molars on the incidence of mandibular angle fractures. METHODS: Four hundred and thirty-six mandibular halves in 218 patients with mandibular fractures, aged between 15 and 40 years old, were analysed using panoramic radiographs. RESULTS: The incidence of angle fractures in the mandibular halves with incompletely erupted mandibular third molars was 30.8% and this was statistically significantly higher than that in another group (p<0.0001). Deeply located mandibular third molars clearly showed a higher incidence of this fracture when compared with the adjacent second molar (p<0.0001). CONCLUSION: The results of this investigation showed that incompletely erupted mandibular third molars close to the inferior border of the mandible have a high risk of angle fractures.