正畸治疗中磨牙的拔除和保留(二十一)——应用全颌曲面断层片对下颌磨牙冠根形态的比较研究

目的：统计分析下颌第一、第二、第三磨牙牙冠近远中宽度、牙体长度、分根情况以及相关因素。方法：选择下颌无缺失牙,下颌第三磨牙牙根发育已完成的全颌曲面断层X线片249张进行测量分析。结果：牙体长度下颌第一磨牙至第三磨牙依次递减;牙冠近远中宽度下颌第一磨牙最大,第二、第三磨牙无差别;分根率下颌第一磨牙至第三磨牙依次递减,根分叉程度下颌第一磨牙最大,第二、第三磨牙无差别;下颌第三磨牙萌出组牙体长度大于第三磨牙阻生组,并且与其牙冠近远中宽度成正相关,分根率也偏大;下颌第三磨牙相对宽度在单根、双根组间有差别;下颌第三磨牙牙冠宽度/磨牙后间隙长度比值与下颌第三磨牙相对长度比成负相关关系。结论：下颌第一磨牙冠根形态最好;第二、第三磨牙冠根形态有较大的相似性,只要有足够的空间,下颌第三磨牙牙根就能得到良好的发育。     

下颌第二磨牙近中阻生的局部牙列及颌骨形态的三维分析

目的 通过CBCT三维测量比较下颌第二磨牙近中阻生患者与非阻生患者下颌第二磨牙区域牙列及颌骨形态的差异，分析下颌第二磨牙近中阻生患者的局部牙列及下颌骨形态特征。方法 选取下颌第二磨牙近中阻生与非阻生患者总计148例，共分为三组，第一组(G1):下颌第二磨牙单侧阻生患者(50例);第2组(G2):双侧阻生患者(48例);第3组(G3):对照组(50例)。收集患者治疗前的CBCT影像，共测量15个指标并进行统计学分析，其中牙性指标10个，骨性指标5个。结果 单侧及双侧阻生患者下颌第二磨牙牙冠长度、宽度均大于对照组，而萌出间隙颌骨高度均小于对照组；双侧阻生患者萌出间隙长度及宽度均显著小于单侧阻生患者；单侧阻生患者萌出间隙长度及高度均小于非阻生侧(P<0.05)。结论 下颌第二磨牙近中阻生患者下颌第一磨牙、第二磨牙牙冠相对较大；下颌第二磨牙近中阻生患者萌出间隙不足，且双侧阻生较单侧萌出间隙不足更为严重，而下颌第三磨牙的存在及性别差异与下颌第二磨牙近中阻生无显著关联。     

运用曲面断层全景片测量下颌第三磨牙的萌出间隙

目的 :早期预测下颌第三磨牙阻生或萌出的一些客观指标 ,为临床治疗方案提供依据。方法 :随机选择 2 68例患者 (共 417颗下颌第三磨牙 ) ,将其随机分为萌出组、阻生组 ,运用曲面断层全景机对下颌第三磨牙的近中倾斜角、萌出水平、牙冠近远中径、牙根形成、磨牙后间隙、磨牙后间隙 牙冠近远中径的比值进行测量分析。结果 :阻生组中 (15 4例 ,2 18颗下颌第三磨牙 )近中倾斜角平均为 15 .64° ,性别之间在统计学上无显著性差异 (P >0 .0 5 )。阻生组磨牙后间隙比萌出组小 ,二者之间在统计学上有显著性差异 (P <0 .0 0 1)。萌出组与阻生组磨牙后间隙 牙冠近远中径的平均值分别为 1.0 5、0 .74(P <0 .0 0 1)。阻生组与萌出组的牙冠近远中径之间无显著性差异。下颌第三磨牙阻生的发生率与近中倾斜角呈正相关 (P <0 .0 1) ,而与磨牙后间隙呈负相关 (P <0 .0 1)。结论 :大多数阻生的下颌第三磨牙磨牙后间隙 牙冠近远中径比值小于 1。由于没有足够的间隙萌出 ,是导致下颌第三磨牙阻生的重要原因     

磨牙倾斜角度和萌出间隙对第三磨牙萌出的影响

目的研究影响第三磨牙阻生或萌出的一些客观因素。方法选择86例(男37例,女49例)平均年龄25.4岁,上下颌第三磨牙均存在的患者,将其分为萌出组和阻生组,利用曲面断层片对患者上下颌第三磨牙的近中倾斜角、牙冠近远中径、磨牙后间隙、磨牙后间隙和牙冠近远中径的比值进行测量分析。结果上颌萌出组萌出间隙较阻生组大1.95mm,第二磨牙和第三磨牙长轴交角相差12.53°,萌出组第三磨牙近远中径比阻生组小0.69mm,有统计学差异。下颌萌出组萌出间隙L-ES(R)较阻生组平均值大3.33mm;第三磨牙与牙合平面交角阻生组较萌出组大32.48°;萌出组与阻生组的磨牙后间隙/牙冠近远中径平均值分别为1.05、0.85,3项指标差异均有显著性(P<0.01)。下颌第三磨牙近远中径相差0.3mm,无统计学意义。结论第三磨牙萌出受萌出间隙和磨牙间交角的影响,对于上颌第三磨牙,磨牙交角影响更大,对于下颌第三磨牙无足够的间隙萌出,是导致下颌第三磨牙阻生的重要原因。     

拔除下颌第三磨牙后相邻第二磨牙远中牙周情况的早期变化

目的 :观察低位近中阻生的下颌第三磨牙拔除后,相邻第二磨牙远中牙周情况的变化。方法:58例低位阻生的下颌第三磨牙拔除前后随访观察6个月,通过全景片测量相邻第二磨牙远中牙槽嵴高度,临床检查牙周袋深度、龈缘位置和附着水平等牙周指标。结果:58例低位近中阻生的下颌第三磨牙拔除后,相邻第二磨牙远中齿槽嵴高度和龈缘位置均有不同程度的增高,差异有统计学意义。结论:对于年轻患者,应尽早拔除阻生的下颌第三磨牙,有益于增加拔牙后相邻第二磨牙远中牙槽骨的高度。     

下颌第四磨牙1例

病例报告患者,男,26岁,双侧上颌第三磨牙正常萌出,未建。右侧下颌第三磨牙前倾阻生。左侧下颌第三磨牙低位阻生,近中边缘嵴破龈。全颌曲面体层X线片示:左下颌第三磨牙垂直低位,面位于第二磨牙颈部平面。左下颌第四磨牙近似水平位,位于第三磨牙面上;牙冠近中边缘嵴突出,远中边缘嵴低平;牙根尖伸向第三磨牙牙冠后方(图1)。     

西安地区出土的2 200年前人与现代人下颌骨后段的形态学研究

目的:通过对西安地区出土的2 200年前人下颌骨标本与现代人下颌骨标本的研究,探讨人下颌骨后段形态的演化.方法:选取保存较完整的2 200年前成人男性下颌骨标本36个,现代成人男性下颌骨标本38个.按第三磨牙萌出情况进行分组,采用数显游标卡尺及万能角度尺对下颌骨进行测量,记录相关数据并进行统计学分析.结果:2 200年前人标本下颌斜长OB、磨牙后间隙BX均大于现代人标本,两者之间的比值(OB/BX)现代人大于2200年前人,均有显著性差异(P<0.05).同时期内不同分组测量结果显示,萌出组下颌斜长、磨牙后间隙长度与阻牛组、缺失组差异显著(P<0.05).结论:下颌骨长度和磨牙后间隙长度影响下颌第三磨牙的生长发育.伴随咀嚼器官的不断退化,人下颌骨总长度呈负增长趋势,且磨牙后间隙长度退化幅度尤为显著.     

应用阻生磨牙竖直器矫正下颌第三磨牙近中倾斜阻生

目的 通过临床应用阻生磨牙竖直器配合使用阻生磨牙直立牙挺辅助矫治近中倾斜阻生的下颌第三磨牙,检验其疗效.方法 选择9名下颌第三磨牙近中倾斜阻生患者使用阻生磨牙竖直器配合使用阻生磨牙直立牙挺进行正畸治疗,共有15颗下颌阻生齿需要治疗.测量矫治前后的曲面断层片下颌第二磨牙和第三磨牙的倾斜角,对比分析矫治前后倾斜角度变化,进行配对t检验.分别测量治疗前后下颌第二磨牙长轴与下颌升支后缘切线、双侧乙状切迹最下缘连线及双侧突顶点连线交角,独立样本t检验表明,矫治前后角度变化无统计学意义(P＞0.1).结果 全部患者矫治效果良好,近中倾斜阻生的第三磨牙实现直立.第二、三磨牙的夹角倾斜度平均减少(55.47±22.07)°,具有显著的统计学意义(P＜0.05).第二磨牙治疗前后倾斜度改变无统计学意义(P＞0.1).结论 阻生磨牙竖直器配合使用阻生磨牙直立牙挺是一种竖直近中倾斜阻生磨牙的简单高效的方法.     

正畸治疗中磨牙的拔除和保留(三十八)——闭下颌第一磨牙拔牙间隙后牙槽嵴高度及牙根吸收的随访研究

目的:通过对正畸关闭下颌第一磨牙拔牙间隙后牙槽嵴高度及牙根吸收情况的随访,探讨关闭磨牙间隙后牙周健康的长期稳定性.方法:共观察下颌第一磨牙拔牙间隙37处,下颌第二磨牙牙根74个.测量矫治结束及随访时的下颌第二磨牙近中牙槽嵴高度以及第二磨牙冠根比,将测量值进行配对t检验.结果:随访时下颌第二磨牙近中牙槽嵴高度以及冠根比与矫治结束时相比,均没有显著性差异.结论:采用拔除第一磨牙后的第二磨牙近中平移技术,关闭拔牙间隙的远期稳定性较好,有利于维持邻牙的牙周健康,可以充分发挥第二磨牙的咀嚼功能,以实现替代第一磨牙的作用.     

下颌前倾或水平阻生磨牙的简捷快速竖直

下颌前倾或水平阻生的磨牙临床上多予以拔除,笔者对于牙列较整齐、下颌第二磨牙阻生或经正畸减数治疗后上颌第三磨牙位置正常、下颌第三磨牙阻生者仅采用与阻生磨牙相邻的磨牙作支抗牙,黏接焊接了多曲推簧的磨牙带环,推阻生磨牙向远中、牙合向移动,引导前倾或水平阻生的下磨牙竖直、萌出.结果显示前倾或水平阻生的下颌磨牙较快地被竖直、萌出到正常的牙合平面,建立良好的牙合关系,X线曲面断层片示原阻生牙冠所占的位置为正常牙槽骨组织所代替.该方法能有效地使前倾或水平阻生的下颌磨牙产生快速的远中牙合向旋转运动,具有无须手术暴露阻生磨牙颊面、操作简单、竖直时间短、患者无明显不适和创伤小等优点.     

Radiographic evaluation of mandibular third molar eruption space.

OBJECTIVE: The purpose of this study was to investigate variables in third molar and arch dimensions among subjects with impacted and erupted mandibular third molars. STUDY DESIGN: Standardized panoramic radiographs were taken for 134 subjects (60 males and 74 females with 213 third molars) with an average age of 19.8 years. For the impacted group, only those who had mesioangular inclination of the third molars were recorded. The radiographic features studied were angulation of tooth, level of eruption, development of root, mesiodistal crown width, retromolar space, and gonial angle. RESULTS: Third molar angulation in the impacted group (69 subjects with 101 third molars) averaged 16.28 degrees (SD +/- 11.88 degrees), with no significant gender differences. The retromolar space was significantly smaller in the impacted group than in the erupted group (P < .001). This space was also the only significant variable (P < .05) associated with lateral asymmetry in the eruption/impaction status of third molars. In the impacted group, 83% of subjects had third molar space/crown width ratios less than 1, whereas in the erupted group 69% had ratios of at least 1. The average space/crown width ratios in the impacted and erupted groups were 0.78 and 1.06, respectively (P < .001). The impacted and erupted groups did not differ significantly with respect to mesiodistal crown width and gonial angle. Approximately 76% of impacted third molars had complete root formation, 20% had two thirds root formation, and only 4% displayed one third root formation. Of the impacted third molars, 66% were partially erupted and the rest were unerupted. There was a strong positive relationship between frequency of third molar impaction and degree of angulation (P < .001), but the former was inversely associated with retromolar space (P < .001). CONCLUSIONS: The most significant variable associated with third molar impaction is inadequate space. The vast majority of impacted third molars had space/crown width ratios of less than 1.     

Mandibular third molar space in different antero-posterior skeletal patterns

Retromolar space has long been identified as a major factor in the aetiology of mandibular third molar impaction. The aims of this study were to compare mandibular third molar space between the different antero-posterior (A-P) skeletal patterns, between erupted and impacted third molars in the different A-P skeletal patterns, and to report on the status of third molar eruption/impaction among the studied subjects. A total of 432 mandibular third molars in 270 subjects (132 females and 138 males) were investigated from dental pantomograms (DPTs) and lateral cephalograms (LC). The average age for the total sample was 20.80 ± 2.03 years. The subjects were divided into three groups according to their ANB angle as follows: skeletal Class I (144 third molars in 90 subjects), skeletal Class II (145 third molars in 95 subjects), and skeletal Class III (143 third molars in 85 subjects). Each group was subdivided into impacted and erupted subgroups. DPT and LC were traced and the following variables were measured: retromolar space width, third molar width and angulation, β angle, second molar angulation, mandibular length, and gonial angle. Independent t-test, analysis of variance, and chi-square test were used for statistical analysis. Retromolar space width in the Class III subjects was smaller than in the Class I subjects (P?相似文献   

Patterns of third molar impaction in a group of volunteers in Turkey

The aim of this study was to investigate the different variables in mesio-vertically positioned impacted or erupted third molars in a group of volunteers in Turkey to determine the angular changes and levels of eruption radiographically using standardised panoramic radiographs. There were 213 volunteers with impacted and erupted third molars included in this study, most of whom were dental students. Standardised panoramic radiographs were taken from all the volunteers. The radiographic parameters included angulation of tooth, level of eruption, development of root, mesiodistal crown width, retromolar space, and gonial angle. Statistical analysis was done using the t-test for independent groups. It was found that the mesiodistal angulation of third molars was significantly greater while the retromolar space of third molars was significantly smaller in the impacted group (P<0.05). There was also a significant difference in retromolar space/third molar crown width ratio (P<0.05).     

Radiographic assessment of lower third molar eruption in different anteroposterior skeletal patterns and age-related groups

Objective:To analyze radiographic predictors for lower third molar eruption among subjects with different anteroposterior skeletal relations and of different age groups.Materials and Methods:In total, 300 lower third molars were recorded on diagnostic digital orthopantomograms (DPTs) and lateral cephalograms (LCs). The radiographs were grouped according to sagittal intermaxillary angle (ANB), subject age, and level of lower third molar eruption. The DPT was used to analyze retromolar space, mesiodistal crown width, space/width ratio, third and second molar angulation (α, γ), third molar inclination (β), and gonion angle. The LC was used to determine ANB, angles of maxillar and mandibular prognathism (SNA, SNB), mandibular plane angle (SN/MP), and mandibular lengths. A logistic regression model was created using the statistically significant predictors.Results:The logistic regression analysis revealed a statistically significant impact of β angle and distance between gonion and gnathion (Go-Gn) on the level of lower third molar eruption (P < .001 and P < .015, respectively). The retromolar space was significantly increased in the adult subgroup for all skeletal classes. The lower third molar impaction rate was significantly higher in the adult subgroup with the Class II (62.3%) compared with Class III subjects (31.7%; P < .013).Conclusion:The most favorable values of linear and angular predictors of mandibular third molar eruption were measured in Class III subjects. For valid estimation of mandibular third molar eruption, certain linear and angular measures (β angle, Go-Gn), as well as the size of the retromolar space, need to be considered.     

Third molar impaction in the Jazan Region: Evaluation of the prevalence and clinical presentation

ObjectiveTo provide information on the prevalence and clinical features of impacted third molar teeth in the South-Western region of Saudi Arabia.Material and methodsIn this cross-sectional study, 1200 panoramic radiographs (50% males and 50% females) were retrieved from the electronic clinical records of patients at the College of Dentistry, Jazan University from December 2014 to December 2016, and impacted third molars were evaluated. Data on clinical and radiographic presentation were analyzed.ResultsOverall, there were 291 (24.3%) patients with impacted third molars among 1200 radiographs. The distribution of impacted third molars according to the number of impacted teeth was as follows: one impaction in 121 (41.6%); two impactions in 90 (30.9%); three impactions in 42 (14.4%); and four impactions in 38 (13.1%) patients. There was a high prevalence of all impaction types among females (54.5%). Maxillary vertical angulation was most common (50%) followed by mandibular mesioangular angulation (48.3%). The depth of impaction in maxillary teeth was higher than in mandibular teeth. Pain was uncommon (4.5% of patients).DiscussionClinically, vertical impaction in the maxilla was present in 50% of patients because of limited posterior space, and mesioangular angulation in the mandible was present in 48% of patients because of inadequate space between the ramus and the second molar. These findings are similar to other reports. Vertical impaction of the maxillary wisdom tooth is mostly related to the discrepancy between the mesiodistal size of the tooth crown and the limited retromolar space.ConclusionNoiseless presentation of an impacted third molar requires raising the population’s awareness about the need for diagnosis and treatment of the problem to avoid any further complications. The study can be to guide surgical procedures. This study documented the prevalence, pattern, and clinical features of impacted third molars in South Western region of Saudi Arabia.     

Factors associated with mandibular third molar eruption and impaction

A retrospective study, using panoramic radiographs, was conducted on 152 Taiwanese (72 males and 80 females) to investigate mandibular third molar eruption and impaction. The following measurements were made: inclinations and mesiodistal crown widths of the mandibular molars, vertical and horizontal spaces between the distal surface of the second molar and the anterior surface of the ramus, lengths and widths of the mandibular ramus and body, the ramus inclination, the mandibular plane angle, and the mandibular gonial angle. Differences between non-impaction and impaction groups were studied, and the variables were analyzed with multivariate discriminatory analysis. Significant differences between the two groups were found; variables describing spaces between the anterior of the ramus and the distal of the mandibular second molar and tooth size appeared to be the primary contributors to the differences observed.     

成人下颌磨牙后间隙与第三磨牙关系的三维研究

目的 测量成人下颌磨牙后区大小并分析其与第三磨牙状态的关系.方法 采用CBCT对86例成年骨性Ⅰ类均角患者根据第三磨牙状态进行分组,从三维方向对右侧下颌磨牙后间隙进行测量.在水平面上沿POL线(第一磨牙与第二磨牙颊尖连线)测量下颌平面(以及从下颌平面向根方2 mm的平面)处第二磨牙牙冠到升支前缘的最短距离.牙根层面...     

下颌无牙颌牙槽嵴牙位划分方法的初步探讨

目的:初步探讨下颌无牙颌牙槽嵴牙位划分方法,为测量分析下颌牙槽嵴形态及其对义齿稳定影响提供定位依据.方法:收集符合标准的下颌无牙颌患者模型302例,从中随机选取50例,通过三维激光扫描获取石膏模型牙槽嵴表面数据,运用SolidWorks软件确定咬合平面、并在牙槽嵴顶线的投影上利用各天然牙中点至中切牙近中面长度占同侧天然牙列近远中长度(正中切牙近中面至第二磨牙远中面)的百分比值确定各牙位,标记并连接各测量点:牙槽嵴顶中央点投影(A),左侧磨牙后垫前缘投影(L),右侧磨牙后垫前缘投影(R),左右磨牙后垫前缘投影连线(LR)的中点(M),连接A、M并标记AM中点C;连接C到各牙位中点标记点,并连接M到后牙区各牙位中点标记点,测量各连线与AM的夹角;统计分析测量的数据.结果:在前牙区,C点到各个牙位中点连线近似位于同心圆上,连线与AM的夹角稳定性高(C.V＜5％);在后牙区,M点到各个牙位中点连线与AM的夹角较C点连接角度的方差和极差更小,稳定性更高(C.V＜5％);同时,利用AM与LR的比值作为定位角度参数建立预测方程,可有效较正各牙位定位偏差.结论:选择下颌牙槽嵴中央线上不同的牙位划分线原点,使用划分线与矢状线的夹角平均值,并通过咬合平面上牙槽嵴顶线投影的高宽比作为参数建立牙位划分角度预测方程,可在下颌牙槽嵴顶线上较稳定地划分各牙牙位.