双下颌管的CBCT观察

目的 :应用CBCT对下颌骨双下颌管情况进行观察和研究,统计其发生概率,为下颌后牙区种植及下颌第三磨牙拔除提供参考。方法:收集2012—2014年上海市第六人民医院口腔科就诊病人200例,征得患者同意登记个人信息并拍摄CBCT。观察患者有无双下颌管,描述其走行特征并进行统计学分析。结果:双下颌管发生率为29.5%,并发现三分支下颌管2例。下颌管分支根据走行方向分成3类:磨牙管、颊舌侧管、前行管。其中磨牙管发生率为20%,颊舌侧管发生率为8%,前行管发生率72%。结论:经CBCT观察发现,双下颌管有较高发生率,在下颌后区进行种植术等各种手术治疗前应拍摄CBCT,警惕双下颌管的存在,防止严重并发症的发生。     

下颌管与下颌第三磨牙牙根相对位置关系的CBCT研究

目的:对曲面断层X线片提示下颌第三磨牙与下颌管关系密切的患者,应用锥形束计算机断层扫描(CBCT)进一步观察测量,为临床制定下颌第三磨牙拔除的手术方案及预防术后并发症做参考。方法:对曲面断层X线片显示下颌阻生第三磨牙(impacted mandibular third molar,IMTM)牙根与下颌管接触或部分重叠的患者168例(210)侧进一步行CBCT检查,观察下颌第三磨牙与下颌管的相对位置。结果:下颌管壁完整者93侧(44.3%),其中72侧(77.4%)下颌管位于IMTM牙根颊侧(1.95±0.95)mm;19侧(20.0%)在其正下方(2.61±1.37)mm;1侧(1.1%)位于其舌侧3.98mm;1侧(1.1%)位于牙根间。下颌管不完整者117侧。其中有较小范围缺损者(缺损最大径≤2mm)42侧(20.2%);而下颌管相对IMTM的位置,位于颊侧有23侧(54.8%),位于正下方14侧(33.3%),位于舌侧5侧(11.9%)。有较大范围缺损者(缺损最大径>2mm)75侧(36.1%);下颌管相对IMTM的位置,位于颊侧有20侧(26.7%),平均缺损最大径(6.42±2.45)mm,平均缺损面积(12.86±10.84)mm2;位于正下方43侧(57.3%),平均缺损最大径(7.90±2.87)mm,平均缺损面积(12.73±8.75)mm2;位于舌侧12侧(16.0%),平均缺损最大径(8.06±2.14)mm,平均缺损面积(21.40±11.84)mm2。结论:对于曲面断层片上提示IMTM与下颌管关系密切的患者,有必要进行CBCT检查,进一步了解其相对位置。     

CBCT观察影像重叠的下颌第三磨牙与下颌管的位置关系

目的:观察在曲面断层片(Orthpantomography,OPG)中表现为重叠影像的下颌第三磨牙和下颌管在CBCT(cone beam CT)中的位置关系。方法:对在OPG上表现为下颌第三磨牙和下颌管影像重叠的116名患者(136颗牙)进行CBCT扫描。利用软件(I-view)对所得图像测量分类。通过SAS软件对所得数据进行x~2检验。结果:136颗牙中,在下颌第三磨牙和下颌管接触方面的概率上与性别无关(P=0.0758);而当OPG中下颌管与第三磨牙重叠时,骨白线的存在与否与两者是否接触是有关的(P=0.0003)。结论:下颌CBCT和OPG相比,可以更准确地反映下颌管和下颌第三磨牙的位置关系。     

基于CBCT的下颌神经管磨牙后区分支的影像学研究

目的通过口腔专用锥形束CT(CBCT)探讨下颌神经管位于磨牙后区的分支的存在概率及对临床应用的影响。方法利用CBCT扫描机对患者进行下颌骨的横断面连续薄层扫描及多平面重建,研究下颌神经管磨牙后区分支的分布及走行情况。结果在208例患者共416侧下颌神经管中观察到66例患者存在下颌神经管磨牙后区分支,其中单侧分支53例,双侧均有分支13例,共计79例,下颌神经管磨牙后区分支率18.99%,分支均位于主干上方,分布于下颌第三磨牙远中或根方(若下颌第三磨牙缺失,分布于下颌第二磨牙远中)。结论本研究得出的下颌神经管磨牙后区的分支的存在概率及位置,可为临床上口腔颌面外科手术提供理论依据。     

下颌管分支的锥形束CT影像学分析

目的 运用锥形束CT（CBCT）分析下颌管分支发生的概率及其类型。方法 选取拍摄CBCT影像的216例（女104 例,男112例）患者为研究对象,对CBCT的下颌管分支影像进行观测并进行分类。结果 216例（432侧）患者中,39例（18.06%）50侧（11.57%）观测到下颌管分支,其中女18例（17.31%）,男21例（18.75%）。下颌管分支分为4类,第Ⅰ类17侧（3.94%）,第Ⅱ类11侧（2.55%）,第Ⅲ类20侧（4.63%）,第Ⅳ类2侧（0.46%）。结论 CBCT对下颌管分支的检出率较高,口腔颌面外科医生在进行下颌手术时应注意下颌管分支这一解剖变异。     

下颌阻生第三磨牙与下颌管关系分型的研究

目的:探讨下颌阻生第三磨牙与下颌管密切关系的系统分型。方法:3237例下颌阻生第三磨牙的曲面体层X线摄像,其中296例阻生牙牙根与下颌管关系密切(间距≤1 mm)增摄CBCT检查,结合临床资料进行分析。结果:下颌阻生第三磨牙与下颌管密切关系有根侧型30.40%、邻管型50.33%、入管型4.72%、卧管型13.51%、骑管型1.01%、混合型0.34%六种类型。结论:下颌阻生第三磨牙与下颌管密切关系的系统分型,对口腔专业教学和临床均有实用意义。     

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。     

下颌正中舌侧管、下颌舌侧副管和下颌切牙神经管解剖关系的CBCT影像研究

目的:明确下颌前牙区血管神经管网系统的走行,提高对下颌切牙神经及其小分支的临床认识。方法:回顾性研究104例患者CBCT影像学资料,观测下颌正中舌侧管、下颌舌侧副管和下颌颊侧管三者同下颌切牙神经管的关系。纳入标准：读取矢状截面、冠状截面、水平截面、任意截面、曲面断层等多个不同的截面图像,能够明确观测到下颌切牙神经管、下颌正中舌侧管、下颌舌侧副管和下颌颊侧管的存在。结果:(1)观测到下颌正中舌侧管同下颌切牙神经管相通15例;双侧下颌切牙神经管相通22例;下颌舌侧副管或下颌颊侧管同下颌切牙神经管相通104例,共184支。结论:(1)下颌切牙神经会发出多个小分支于前磨牙、尖牙、切牙等相应牙位处的颊舌侧骨面,这些小分支的走行管道就是下颌舌侧副管和下颌颊侧管;(2)下颌正中舌侧管是从下颌骨舌侧到内部的一段趋向于消失的管道,并不与下颌切牙神经管相通,部分情况下会同下颌切牙神经吻合或者颊舌向贯穿下颌骨;(3)下颌正中舌侧管并非下颌切牙神经管发出的从下颌骨体内走行到骨面的小分支通行管道,而是来自口底区域的血管神经束发出的分支从软组织进入下颌骨体内的路径。     

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。     

下颌阻生第三磨牙与下颌管重叠时的三维位置关系与拔除方法研究

目的 探讨曲面体层X线片示下颌阻生第三磨牙根尖部与下颌管重叠时的三维位置关系分类,以指导临床采用恰当方法拔出下颌阻生第三磨牙.方法 选取在曲面体层X线片上牙根与下颌管有重叠的57颗下颌阻生第三磨牙,行锥形束CT(cone beam computed tomography,CBCT)检查,了解两者间的三维位置关系,拟定安全的拔除手术方案.结果 55例患者的57颗患牙的CBCT影像中,22颗患牙牙根(38.6％)突破下颌管壁位于下颌管内;30颗患牙(52.6％)的牙根位于下颌管的舌侧,未与下颌管发生接触;4颗患牙(7.0％)的牙根位于下颌管的颊侧,未与下颌管发生接触;1颗患牙(1.8％)的双根跨于下颌管间.57颗患牙均顺利完成拔牙手术,1例患者(1.8％)出现短暂的下唇麻木于术后1个月后恢复.结论 曲面体层X线片上下颌阻生第三磨牙根尖部与下颌管重叠的病例中,下颌第三磨牙的根尖多位于下颌管的舌侧或位于下齿槽神经管内,CBCT检查对拟定正确安全的拔除术式和降低下齿槽神经损伤发生率具有重要的意义.     

下颌阻生智齿相关第二磨牙牙根外吸收：曲面断层片与CBCT对比研究

目的 比较曲面断层片和CBCT在诊断下颌阻生智齿相关第二磨牙牙根外吸收的差异。方法 回顾性分析2019年1月—2020年12月于南京医科大学附属口腔医院就诊的832例(1 074颗)近中/水平下颌阻生智齿病例,分别应用曲面断层片和CBCT评估下颌第二磨牙远中牙根外吸收发生率,并分析曲面断层片诊断错误的相关因素。结果 以CBCT影像学结果判定为标准,下颌智齿相关第二磨牙牙根外吸收的发生率为33.15%(356/1 074),曲面断层片诊断正确率为66.39%。经多因素Logistic回归分析发现：中低位、Ⅲ类阻生智齿,下颌阻生智齿与第二磨牙牙根重叠,下颌阻生智齿与第二磨牙牙根接触是导致曲面断层片诊断错误的危险因素(P<0.05)。结论 曲面断层片诊断下颌阻生智齿相关第二磨牙牙根外吸收正确性较低,推荐选用CBCT检测。     

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.     

Radiographic study of the mandibular retromolar canal: an anatomic structure with clinical importance

Introduction

The retromolar canal is an anatomic structure of the mandible with clinical importance. This canal branches off from the mandibular canal behind the third molar and travels to the retromolar foramen in the retromolar fossa. The retromolar canal might conduct accessory innervation to the mandibular molars or contain an aberrant buccal nerve.

Methods

Patients referred for panoramic radiography were consecutively enrolled, provided a limited cone-beam computed tomography (CBCT) scan had also been taken in the area of interest. Radiographs were retrospectively screened for the presence of a retromolar canal, and linear measurements (distance to second molar, height, width) were taken.

Results

One hundred twenty-one sides in 100 patients were evaluated (100 unilateral and 21 bilateral cases). A total of 31 retromolar canals were identified with CBCT (25.6%). Only 7 of these canals were also seen on the corresponding panoramic radiographs. The existence of a retromolar canal was not statistically related to gender or side. With regard to the linear measurements, the mean distance from the retromolar canal to the second molar was 15.16 mm (±2.39 mm), the mean height of the canal was 11.34 mm (±2.36 mm), and the mean width was 0.99 mm (±0.31 mm).

Conclusions

This radiographic study documents a frequency of 25% for the presence of a retromolar canal. The clinician is advised to preserve this anatomic variation when performing surgery in the retromolar area and to consider additional locoregional anesthesia in the case of failed mandibular block anesthesia.     

Position of the impacted third molar in relation to the mandibular canal. Diagnostic accuracy of cone beam computed tomography compared with panoramic radiography

This study investigated the diagnostic accuracy of cone beam computed tomography (CBCT) compared to panoramic radiography in determining the anatomical position of the impacted third molar in relation with the mandibular canal. The study sample comprised 53 third molars from 40 patients with an increased risk of inferior alveolar nerve (IAN) injury. The panoramic and CBCT features (predictive variables) were correlated with IAN exposure and injury (outcome variables). Sensitivity and specificity of modalities in predicting IAN exposure were compared. The IAN was exposed in 23 cases during third molar removal and injury occurred in 5 patients. No significant difference in sensitivity and specificity was found between both modalities in predicting IAN exposure. To date, lingual position of the mandibular canal was significantly associated with IAN injury. CBCT was not more accurate at predicting IAN exposure during third molar removal, however, did elucidate the 3D relationship of the third molar root to the mandibular canal; the coronal sections allowed a bucco-lingual appreciation of the mandibular canal to identify cases in which a lingually placed IAN is at risk during surgery. This observation dictates the surgical approach how to remove the third molar, so the IAN will not be subjected to pressure.     

Methods of determining the relationship of the mandibular canal and third molars: a survey of Australian oral and maxillofacial surgeons

BACKGROUND: Surgical extraction of third molars is one of the most common oral and maxillofacial surgical procedures performed and may have a number of associated complications. One of these complications is inferior alveolar nerve (IAN) dysaesthesia or impairment of sensory perception (including paraesthesia and/or anaesthesia). Previous studies assume that most clinicians use various combinations of nine radiologic criteria on panoramic radiographs as indicators of the relationship and, therefore, predictors of the risk of postoperative dysaesthesia. Our study assessed both the current radiologic modalities and assessment criteria used by Australian oral and maxillofacial surgeons when determining the proximity of mandibular canal to third molars. METHODS: A survey of all surgeon members of the Australian and New Zealand Association of Oral and Maxillofacial Surgeons (ANZOMS) practising in Australia was undertaken. RESULTS: Of the 105 questionnaires sent to surgeons, 72 responses (68 per cent) were returned. All surgeons reported using the panoramic radiograph but only 25 per cent considered it sufficiently accurate in determining the relationship between the mandibular canal (MC) and the third molar root, while 61 per cent of surgeons use CT for this purpose but the average frequency of use was very low (five per cent). This study also revealed that the nine radiologic criteria on a panoramic radiograph are used to varying extents by Australian surgeons. Nearly all surgeons use 'change in MC direction' and 'MC narrowing' to determine and close relationship. Thirty-one per cent used superimposition of the MC and the root of the third molar alone and 24 per cent used appearance of contact of the root with the MC alone in the absence of any other radiologic criteria to indicate close or intimate relationship. CONCLUSION: Further research is required to determine the accuracy and observer agreement or reliability of using the nine panoramic characteristics, to determine this relationship and whether the presurgical determination of proximity and position (buccal or lingual) of the canal utilizing CT has any usefulness in determining the surgical protocol or affect on postoperative morbidity.     

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.