基于锥形束CT的下颌阻生第三磨牙与下颌管位置关系研究

目的 应用锥形束CT(cone beam CT,CBCT)分析下颌阻生第三磨牙与下颌管的三维位置关系,为下颌阻生第三磨牙拔除术前风险评估和制定手术方案提供依据。方法 选取2017年1月至2022年2月就诊于上海市松江区中心医院口腔科需行下颌阻生第三磨牙拔除术的患者732例(1063颗患牙)。所有患者曲面体层片显示下颌阻生第三磨牙牙根与下颌管接触或重叠,调整CBCT十字观察轴的位置和角度形成坐标轴,在冠状面根据下颌管在坐标中的位置,对下颌管与下颌阻生第三磨牙的位置关系进行分类,包括颊侧、颊侧偏下、下方偏颊、下方居中、下方偏舌、舌侧偏下和舌侧,每类可再分为接触、非接触亚类。测量并比较各类下颌管与下颌阻生第三磨牙的接触率和距离差异。结果 1063颗下颌阻生第三磨牙牙根与下颌管的接触率为53.6%,各类接触率比较,差异有统计学意义(χ²=352.945,P <0.001)。其中,舌侧和舌侧偏下的接触率分别为97.2%、96.7%,明显高于除下方偏舌外的其他分类接触率;下方偏舌、下方居中及颊侧的接触率分别为79.2%、70.2%、60.0%,均高于下方偏颊和颊侧偏下的...     

下颌第三磨牙阻生情况与急性冠周炎发生的关系

目的:研究下颌第三磨牙位置特征与急性冠周炎发生的关系。方法:选择122名临床诊断为下颌第三磨牙急性冠周炎患者(年龄18～31岁),分别记录下颌第三磨牙的萌出角度、软组织覆盖率、有无上颌牙列的咬合创伤及其萌出高度,然后对以上数据分别进行统计学分析。结果:发生急性冠周炎的下颌第三磨牙以垂直阻生最多见(57%),近中阻生次之(34%),水平阻生(7%)和远中阻生最少(2%),各种阻生之间的差别具有统计学意义(P<0.05)。发生急性冠周炎的下颌第三磨牙部分软组织覆盖(以75%的覆盖率最多见)多于全部软组织覆盖,差别具有统计学意义(P<0.05)。有无上颌牙列的咬合创伤与急性冠周炎的发生没有明显的统计学意义(P>0.05)。发生急性冠周炎的下颌第三磨牙萌出高度多数与(?)平面平齐,萌出高度间的差别具有统计学意义(P<0.05)。结论:垂直阻生、软组织部分覆盖、萌出高度平齐于(?)平面的下颌第三磨牙容易发生急性冠周炎,具有这些特征的下颌第三磨牙要高度重视。     

下颌阻生第三磨牙X线分析

本文就３６８颗下颌阻生第三磨牙Ｘ线牙片进行了读片分析，结果表明：下颌第三磨牙以近中阻生最多，垂直阻生次之，水平阻生居第三。三类统共占全部阻生第三磨牙的９２．６６％。牙根数目以双根最多，单根次之。牙根形态以直根最多，远中弯曲根次之。有７５．００％的下颌阻生第三磨牙根尖与下颌管关系密切。６１．４％有冠周骨组织炎性病变，其中，远中骨吸收与垂直阻生关系密切，近中骨吸收与近中和水平阻生关系密切。第二磨牙远中邻面龋坏与近中阻生关系密切。作者认为下颌第三磨牙近中、水平阻生和存在冠周炎症的垂直阻生牙原则上均应拔除。Ｘ线牙片能全面确切地了解阻生牙的骨内情况，辅助阻力分析及手术方案的制定，对下颌第三磨牙拔除术是必要的，应作为术前常规。     

下颌第三磨牙阻生类型同体两侧对称性研究

目的研究下颌第三磨牙阻生类型同体左、右对称性。方法收集186例下颌第三磨牙拔除病例数据。所有患者进行临床检查并拍摄曲面断层片。按照Pell—Gregory升支分类、Pell—Gregory牙争平面分类和Winter分类对左、右两侧下颌第三磨牙阻生类型分别进行分类。对两侧下颌第三磨牙阻生类型进行描述性统计分析和Speaman相关分析。结果三种阻生类型两侧完全对称者95例,占51．1％;任意两种阻生类型两侧均对称,另一种不对称者占19．9％;三种阻生类型中仅一种两侧对称,另两种不对称者占14．5％;三种阻生类型两侧均不对称者占14．5％。两侧下颌第三磨牙Pell—Gregory升支分类（r=0．51,P=0．01）、Pell—Gregory铪平面分类（r=0．41,P=0．01）和Winter分类（r=0．48,P=0．01）均有显著相关性,将每侧下颌第三磨牙三种阻生类型合并,两侧也具有显著相关性r=0．67,P=0．01）。结论同体两侧下颌第三磨牙阻生类型具有对称性,一侧下颌第三磨牙的阻生类型、临床病理以及治疗方案对另一侧具有指导意义。     

下颌阻生第三磨牙的x线观察

本文就1832例下颌阻生第三磨牙x线牙片进行了读片分析。结果表明:阻生牙以垂直阻生最多,近中阻生次之,水平阻生居第三。这三类阻生牙占总数98.16％。牙根形态以直根最多,弯向远中根次之,相对弯曲根及弯向近中根较少。牙根数目以双根最多,单根次之,多根较少。第二磨牙远中邻面龋坏则是与近中阻生关系最为密切。作者认为,无论何种阻生牙,只要反复引起冠周炎或邻牙龋坏者,都应拔除。而术前常规拍摄x线牙片,了解其牙根形态及数目是顺利拔除该牙的有效途径。     

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评价下颌第三磨牙引导管与阻生状态的研究

目的: 采用CBCT评价下颌第三磨牙引导管的形态,探究其与阻生状态的关系,为预测第三磨牙是否阻生提供依据。方法: 选取76例下颌第三磨牙的CBCT影像资料,测量其引导管长径、短径、长短径之比及其与牙胚长轴的角度,并对测量数据进行统计分析。结果: 不同阻生状态下颌第三磨牙的引导管之间,长径、短径和长短径之比无统计学差异,与牙胚长轴的角度:正常萌出>近中阻生>水平阻生。下颌第三磨牙引导管的长径、短径及其与牙胚长轴的角度与年龄相关。结论: CBCT可以精确评价引导管形态,不同阻生状态的第三磨牙引导管与牙胚长轴的角度不同。引导管的缺失和/或与牙胚长轴的角度异常,提示牙齿可能出现萌出异常。     

下颌阻生第三磨牙根尖距下颌管距离与邻牙结构的相关性分析

目的:通过测量数字曲面体层片,对下颌阻生第三磨牙(impacted wisdom teeth,IWT)根尖距下颌管上壁的距离及其与下颌第二磨牙(mandibular second molars,MSM)之间的结构关系进行分析,明确IWT与MSM之间的结构是否与IWT根尖距下颌管上壁距离有相关性。方法:随机选取122例有IWT人群的数字曲面体层片,用数字图像测量软件测量IWT根尖距下颌管上壁距离及其与MSM之间的结构关系数据,采用SPSS 17.0软件包对数据进行统计学处理。结果:根尖位于下颌管上壁以下的IWT占31.33%。IWT长轴与MSM长轴之间的交角大小与IWT根尖距下颌管上壁距离呈显著负相关(P<0.001)。IWT与MSM之间的重叠率为30.47%;与MSM重叠的IWT的根尖距下颌管上壁距离显著比不重叠者长(P<0.01)。近中阻生型IWT根尖与下颌管上壁距离显著比垂直阻生型短(P<0.01)。高位阻生型IWT根尖距下颌管距离显著比低位阻生型长(P<0.01)。结论:IWT与MSM之间的结构关系与IWT根尖距下颌管上壁的距离显著相关。应用数字曲面体层片对IWT与MSM之间的结构关系进行分析,可为选择适当的IWT拔除方法提供重要的观察和分析视角。     

选择性保留下颌前倾阻生第三磨牙探讨

目的 探讨下颌前倾阻生第三磨牙的保留方法和可行性。方法 选择合适病例，经牙体制备，以充填修复的手段使前倾第三磨牙重建邻间关系和咬合关系。结果 随访1年以上32例患者41颗患牙，治疗总有效率为87.8%，其中33颗修复体完好，咬合关系良好，无食物嵌塞，无继发龋，占80．49％。结论 此类患牙经过合理的治疗修复多数是可以保留的。     

以下颌神经管为参照的下颌阻生第三磨牙的分类及临床意义

目的：以下颌神经管为参照,探讨与下颌神经管(inferior alveolar canal,IAC)相交的下颌阻生第三磨牙(impacted mandibular third molars,IMTMs)的阻生类型,并观察手术拔除阻生牙后下牙槽神经损伤与阻生类型间的关系。方法：对锥形束CT(cone beam computed tomography,CBCT)确诊为下颌阻生第三磨牙与下颌神经管接触或相交的378例患者共658侧阻生牙,以下颌神经管为参照,将阻生牙分为4类：Ⅰ类位于神经管的上方,Ⅱ类位于神经管的颊侧,Ⅲ类位于神经管的舌侧,Ⅳ类下颌神经管位于牙根之间。所有病例均采用手术拔除,术后观察容易引起下牙槽神经损伤的阻生类型,统计各种类型神经损伤的例数,应用SPSS13.0软件包对数据进行χ²检验。结果：阻生牙拔除后,下牙槽神经损伤率为6.8%(45/658)。其中,第Ⅰ类15例(15/332)发生下唇麻木、第Ⅱ类19例 (19/108) 发生下唇麻木、第Ⅲ类11例(11/210)发生下唇麻木,第IV类未发生下唇麻木(0/8)。统计学分析显示,阻生牙拔除后,第Ⅰ类和第Ⅱ类、第Ⅱ类和第Ⅲ类下牙槽神经损伤率有显著差异(P<0.01),第Ⅰ类和第Ⅲ类之间无显著差异(P>0.05)。结论：以下颌神经管为参照,CBCT冠状位可将下颌阻生第三磨牙与下颌神经管相交的患者分为4类,手术拔除过程中均有损伤下牙槽神经的危险,尤其是位于下颌神经管颊侧的阻生牙。     

Vertical eruption patterns of impacted mandibular third molars after the mesialization of second molars using miniscrews

Objective:To investigate (1) whether vertical eruption of impacted third molars improves after mesialization of second molars and (2) what factors affect the vertical eruption of impacted third molars when space caused by missing molars is successfully closed by mesialization of the second molar using miniscrews.Materials and Methods:The treatment group (Group 1) included 52 patients who had (1) missing mandibular first molars (ML-6) or missing deciduous mandibular second molars (ML-E), (2) initially impacted mandibular third molars, and (3) successful space closure of the edentulous area with orthodontics. Panoramic radiographs at start of treatment (T1) and at time of space closure (T2) were collected. The control group (Group 2) included 46 nonedentulous patients with impacted mandibular third molars without molar protraction treatment. Panoramic radiographs with similar T1/T2 treatment times were selected. Nine measurements were obtained regarding horizontal available space, vertical eruption, and third molar angulation.Results:Third molars erupted vertically an average of 2.54 mm in Group 1 compared with 0.41 mm in Group 2. Age, gender, Nolla stage, and angle of the third molars did not show significant correlations with the vertical change of the impacted third molars, whereas the depth of third molar impaction and available space showed significant correlations.Conclusions:Impacted mandibular third molars vertically erupt as a result of uprighting with mesialization of the second molar, and vertical eruption is affected by the initial vertical location of impacted third molars and available space.     

Anatomic relationship between impacted third mandibular molar and the mandibular canal as the risk factor of inferior alveolar nerve injury

Our aim was to explore the relation between the site of the mandibular canal and neurosensory impairment after extraction of impacted mandibular third molars.     

冠根分次去除法在疑或累及下牙槽神经的下颌第三阻生磨牙拔除术中的应用

目的:评价应用截冠法分次拔除紧贴下牙槽神经的下颌阻生第三磨牙的效果。方法:对10例术前全景片及CT均显示牙根紧贴或接触下牙槽神经的下颌阻生第三磨牙患者采用截冠留根法,于釉-牙骨质界去除阻力牙冠,包埋牙根于牙槽骨内;术后观察,待牙根移动远离下牙槽神经后再行拔除术。结果:10例患者术后反应轻微,均无下牙槽神经损伤,无感染情况出现;仅1例牙根未能上移至远离下牙槽神经的位置,留根于牙槽骨内,牙龈创面愈合,随访1年无不适。结论:根尖紧贴或接触下牙槽神经的下颌阻生第三磨牙,经截冠留根术后,断根有上移萌出趋势,可远离下牙槽神经管,后期拔除断根,可明显降低下牙槽神经损伤的风险。     

离体单根下颌第二恒磨牙的根管特点

目的:研究单根的下颌第二磨牙的根管形态。方法:通过X线片和临床检查确定根管, 样本从根中1 /3截断以证实X线片和临床检查结果,采用Melton的方法对C形根管分类。结果: 12个牙有C形牙根并且是C形根管,其中 2个牙归为分类Ⅰ, 5个牙为分类Ⅱ, 5个牙为分类Ⅲ。结论:下颌第二磨牙的C形根管在根管的数量和形态有较大变化。     

下颌第三磨牙根管治疗的临床疗效观察

目的 观察下颌第三磨牙根管治疗的临床疗效。方法 对22例下颌第三磨牙采用改良双敞技术预备、侧方加压方法充填根管，一年后复查观察其临床疗效。结果 22例根管治疗的下颌第三磨牙，一年复查成功19例，成功率为86．36％。结论 尽管下颌第三磨牙根管形态复杂，操作难度大，掌握了不同类型患牙的特点，根管治疗仍可获得较高的成功率。     

Unerupted lower third molars and their influence on fractures of the mandibular angle and condyle

Our aim was to assess the influence of the presence and state of impaction of mandibular third molars on the incidence of fractures of the mandibular angle and condyle. We designed a retrospective study of patients who presented for the treatment of mandibular fractures from January 2006 to April 2011. The independent variables were the presence and degree of impaction of lower third molars, and the outcome variables were the incidence of fractures of the mandibular angle and condyle. The information was acquired from hospital records and panoramic radiographs. Personal data included age, sex, mechanism of injuries, and number of fractures of the mandibular angle and condyle. We studied 110 fractures of the mandibular condyle and 80 of the angle. The incidence of fractures of the mandibular angle was higher in the group with incompletely erupted third molars (37/80, p < 0.001) and that of condylar fractures was higher in the group without (67/110, p < 0.001). An incompletely erupted third molar reduces the risk of condylar fractures and increases the risk of fractures of the mandibular angle.     

Influence of adjacent teeth on impacted third molars in the upper and lower jaws

Panoramic radiographs of 1834 patients older than 21 years were evaluated for the prevalence of impacted teeth at different ages. The frequency of impacted teeth by age was constant, that is, the presence of completely impacted teeth could not be related to age.
The interrelationship between the angulation of impacted teeth and the existence of adjacent teeth was studied in individuals older than 61 years. The angulation of most of the completely impacted teeth in the upper-third molar region was horizontal when adjacent teeth were not present, whereas impacted teeth in the upper-third molar region showed vertical angulation when adjacent teeth were present, suggesting that vertically impacted teeth may become exposed by bone resorption or infection and should be removed. The angulation of impacted lower third molars was horizontal irrespective of the presence of adjacent teeth. It appears that the interrelationship between the angulation of completely impacted teeth and the presence of adjacent teeth is different between the upper and lower third molar regions. The angulation of completely impacted teeth and the presence of adjacent teeth should be included in those criteria which determine whether or not completely impacted teeth should be removed.     

Pre-operative assessment of relationship between inferior dental nerve canal and mandibular impacted third molar in Saudi population

ObjectiveTo study the correlation between the position of the inferior dental (ID) nerve canal and the angulation of impacted mandibular third molars using dental cone beam computed tomography (CBCT).Materials and methodsThe study considered 100 impactions in 85 patients (60 males, 25 females), for whom an initial panoramic radiographic assessment had revealed that the ID canal and the lower 3rd molar were in close proximity. A CBCT scan of each patient was carried out to assess how the ID nerve canal position influenced the class and position of impaction, angulation of impaction, and bone contact.ResultsClass I position B impactions were found in the majority of cases, where the position of the ID canal was approximate to the lingual plate and inferior to the 3rd molar (85.7%). The results were statistically significant (p = 0.001). 96% of the ID canals showed bone contact. Of these, 77.1% of ID canals exhibited lingual bone contact, inferior to impaction. The results were statistically significant (p = 0.001). Horizontally angulated impactions were most common in the mandible, and significantly associated with lingual and inferior positioning of the ID canal (76.2%).ConclusionsOur sample population most commonly exhibited horizontally angulated class I position B impactions of the mandible. The position of the ID canal significantly influenced the type of impaction and bone contact.