Assessment of asymmetry in a normal occlusion sample and asymmetric patients with three-dimensional cone beam computed tomography: A study for a transverse reference plane

Objective:To characterize symmetrical features of patients with facial asymmetry and thus to find the most reliable horizontal reference lines easily used in three-dimensional images. The hypothesis was that there is a difference in the location of bilateral landmarks of the upper skull between the normal occlusion sample and skeletal Class III patients with asymmetry.Materials and Methods:Group 1 (normal occlusion sample) was composed of 20 Korean adults with normal occlusion and no noticeable asymmetry. Groups 2 through 4 were selected from patients who were diagnosed as skeletal Class III malocclusion and grouped according to the extent of asymmetry (group 2: symmetric mandible, no maxillary cant; group 3: asymmetric mandible, no maxillary cant; group 4: asymmetric mandible, more than 4 mm maxillary cant measured at maxillary first molars). Three-dimensional cone beam computed tomography images were taken before treatment, and bilateral landmarks of the skull were located and their vertical and horizontal differences compared.Results:No statistically significant difference was noted in the position of bilateral landmarks between groups, except for AG (P < .05). AG showed significant differences in vertical dimension (P < .001) and in horizontal dimension (P < .0001) between groups. The mean of the difference was clearly greatest at FM.Conclusions:The hypothesis is rejected. All groups had a similar pattern of asymmetry in the upper third of the face. Therefore, the transverse reference line of the bilateral Z or orbitale may be used even in patients with severe asymmetry of the maxilla with reference to the clinical photos.     

成人骨性Ⅱ类错畸形上气道与上、下颌骨形态分析

目的: 应用锥形束CT（CBCT）分析骨性Ⅱ类错畸形患者上气道与上、下颌骨形态的相关关系。方法: 选择骨性Ⅱ类及骨性Ⅰ类错畸形成年患者各33例进行CBCT扫描,保存为Dicom文件,导入Mimics 19.0软件中进行三维重建,对2组患者上气道与上、下颌骨数据进行测量。采用SPSS 19.0软件包进行统计学分析,比较成人骨性Ⅱ类错与个别正常间上气道与上、下颌骨形态、结构的差异,以及骨性Ⅱ类错畸形患者上气道与上、下颌骨测量项目的相关关系。结果: 骨性Ⅱ类错组和个别正常组上气道形态与上、下颌骨测量结果比较,15个测量项目有显著差异(P<0.05)。骨性Ⅱ类错组上气道形态与下颌骨长度存在相关性的项目有10个,骨性Ⅱ类错组上气道形态与上颌骨宽度各测量项目中有显著相关性的项目有13个,骨性Ⅱ类错组上气道形态与下颌骨宽度各测量项目中有显著相关性的项目有3个。结论: 骨性Ⅱ类错畸形患者上气道与上、下颌骨之间具有相关关系。骨性Ⅱ类成人患者的上气道与上、下牙弓宽度也有一定相关关系。     

不同面部生长型正常少年的后牙近远中向倾斜度研究

目的研究恒牙列初期正常少年人群的面部生长型与后牙近远中向倾斜度的关系。方法选择163例正常少年为研究对象,根据面部生长型分为垂直、平均、水平生长型3组,均拍摄X线头颅定位侧位片并进行X线头影测量分析,研究其上下颌后牙近远中向倾斜度及上下颌后牙牙体长轴交角的差异。结果垂直生长型24例,平均生长型96例,水平生长型43例。垂直生长型与水平生长型、水平生长型与平均生长型之间的上下颌第一磨牙和第一、二前磨牙牙体长轴近远中向倾斜度均存在统计学差异（P<0.05）,但垂直生长型与平均生长型之间的差异无统计学意义（P>0.05）。3组的上下颌后牙牙体长轴交角的差异无统计学意义（P>0.05）。结论恒牙列初期正常人群中不同面部生长型有各自相协调的后牙近远中向倾斜度。     

骨性Ⅲ类与Ⅰ类错患者基骨及牙弓宽度的比较研究

目的：评价骨性Ⅲ类错合与骨性I类个别正常合上下颌第一磨牙区基骨及牙弓宽度差异。方法：选取骨性Ⅲ类错合患者与骨性I类个别正常合样本各30例。测量CBCT数据中上颌骨颧弓点和下颌第一磨牙阻抗中心对应的颊侧骨皮质点间的距离作为基骨宽度；测量模型上下颌第一磨牙中央窝之间的距离作为牙弓宽度。使用SPSS 22.0独立样本t检验。结果：上颌基骨宽度Ⅲ类组（63.96±3.78mm）小于I类组（65.67±2.76mm）；下颌基骨宽度Ⅲ类组（62.26±3.12mm）大于I类组（60.29±3.15mm）；基骨宽度差为Ⅲ类组（2.31±2.41mm）小于I类组（5.38±1.24mm）。差异均有统计学意义（P<0.05）。Ⅲ类组与I类组上下颌牙弓宽度均无组间差异（P>0.05）。结论：骨性Ⅲ类患者存在上下颌基骨横向发育不调及上下颌磨牙的颊舌向代偿。     

骨性Ⅱ类错牙合女性患者上颌磨牙近远中倾斜度的CBCT分析

目的:分析骨性Ⅱ类错牙合女性患者上颌磨牙近远中倾斜情况,以期为临床治疗提供参考。方法:选取骨性Ⅱ类错牙合30例及个别正常牙合10例治疗前CBCT数据,以眼耳平面、腭平面及牙合平面测量上颌磨牙倾斜度,并将患者测量项目与个别正常牙合数据进行单样本t检验。将骨性Ⅱ类高角、均角和低角间进行单因素方差分析,并把不同垂直骨面型间的测量项目与下颌平面角及牙合平面角进行Pearson相关性分析。结果:在FH平面、腭平面及牙合平面为参考平面时,骨性Ⅱ类U6较个别正常牙合更加远中倾斜。以腭平面及FH平面为参考时,骨性Ⅱ类低角组到高角组,U6有远中倾斜趋势。以牙合平面为参考时,U7在高角组到低角组有远中倾斜趋势。结论:为代偿上下颌骨矢状向关系不调,骨性Ⅱ类错牙合U6有远中倾斜。骨性Ⅱ类U6随下颌平面角的增加代偿性远中倾斜,但U7远中倾斜趋势不明显。无论何种骨性Ⅱ垂直骨面型,U6代偿性倾斜移动以维持咬合力沿牙齿长轴传递。     

The William Houston Gold Medal 1998

Abstract

The aetiology of asymmetric growth in the mandible is not well understood. Previous studies have indicated that the functional lateral shift of the mandible in the period of prepubertal growth may translate to a true skeletal asymmetry, exclusively in skeletal Class III malocclusion. This asymmetry develops more characteristic features during the pubertal and post-pubertal growth periods. Early correction of a functional lateral shift of the mandible is recommended. The purpose of this study was to examine the relationship between the morphology of the temporomandibular joints and asymmetry in skeletal Class III malocclusion in adult female patients.

Cephalometric and laminographic findings in 36 asymmetric skeletal Class III patients with a lateral shift of mandible (group 3) were compared to those of 25 symmetric skeletal Class I patients (group 1) and the same number of symmetric skeletal Class III malocclusions (group 2). All the patients had received no orthodontic treatment. The results showed that the TMJ of the side to which the mandible shifted showed a significantly narrower and shorter shape of the condyle head, smaller superior condylar space, and steeper eminence than those of the unshifted side.     

微型骨钉辅助上颌快速扩弓对下颌位置的影响

目的 探索微型骨钉辅助上颌快速扩弓(miniscrew-assisted rapid palatal expansion, MARPE)在治疗成人骨性Ⅰ类上颌宽度不足错牙合畸形时对下颌位置的影响。方法 本回顾性研究选取2019年7月—2022年3月,本院收治的20例采用MARPE治疗的成人骨性Ⅰ类上颌宽度不足错牙合畸形患者为研究对象,收集治疗前(T0)、扩弓结束即刻(T1)及维持6个月后(T2)三个时间点的锥形束CT(cone beam computed tomography, CBCT)资料,利用Dolphin软件将头位进行标准化校准,测量下颌骨标记点(左/右侧髁顶点,左/右侧下颌角点及颏下点),相对于冠状面、横断面、矢状面三个参考平面的线距变化,分别代表下颌骨矢状向、垂直向及水平向的位移,采用重复测量方差分析及最小显著性差异法多重比较评估各标记点的位置变化。结果 颏下点及右侧下颌角点在结束即刻(T1)发生顺时针旋转,维持6个月后(T2)复发到治疗前(T0)位置;颏下点未发现水平向移位变化。结论 MARPE在治疗骨性Ⅰ类上颌宽度不足错牙合畸形时,引起下颌位置发生短暂的顺时针旋转,长期...     

骨性Ⅲ类错（牙合）牙弓、基骨弓宽度及协调性分析

目的 探讨骨性Ⅲ类错（牙合）患者牙弓、基骨弓宽度及二者协调性,为临床诊断和治疗提供理论依据.方法 选择骨性Ⅲ类错（牙合）患者33例为实验组,47例个别正常（牙合）为对照组,利用锥形束CT扫描颌面部,将扫描后图像导入Mimics10.01图像处理软件分别测量牙弓宽度、基骨弓宽度,并计算上下颌对应宽度之差,对测量结果进行独立样本t检验.结果 骨性Ⅲ类错（牙合）组上颌牙弓宽度与个别正常（牙合）组比较无显著性差异,但下颌牙弓宽度大于正常（牙合）,其中下颌第一磨牙处平均宽度正常（牙合）为（56.26±3.09）mm,骨型Ⅲ类患者为（57.78±3.22）mm,差异有统计学意义（P＜0.05）;骨性Ⅲ类错（（牙合）上颌基骨弓宽度测量值均小于对照组,其中在上颌第二前磨牙处正常（骀）为（59.11±5.97）mm,骨型Ⅲ类患者为（56.23±5.28）mm,有统计学差异（P＜0.05）,下颌基骨弓宽度均大于对照组,其中在前磨牙及第一磨牙处分别为（47.44±2.96）mm、（59.81±3.87）mm和（76.20±4.20）mm,与正常（牙合）相比差异显著（P＜0.05）.骨性Ⅲ类错（牙合）上下颌基骨弓宽度差值均小于正常（牙合）（P＜0.01）,而牙弓宽度差值仅在尖牙处差异显著（P＜0.05）,其余牙位测量项目无统计学差异.结论 ①骨性Ⅲ类错（牙合）组上颌基骨宽度发育不足,下颌基骨宽度发育过度.②骨性Ⅲ类错（牙合）的宽度不协调表现在基骨水平,牙弓对基骨弓宽度不调有代偿.     

Morphology of the temporomandibular joint in skeletal class iii symmetrical and asymmetrical cases: a study by cephalometric laminography

The aetiology of asymmetric growth in the mandible is not well understood. Previous studies have indicated that the functional lateral shift of the mandible in the period of prepubertal growth may translate to a true skeletal asymmetry, exclusively in skeletal Class III malocclusion. This asymmetry develops more characteristic features during the pubertal and post-pubertal growth periods. Early correction of a functional lateral shift of the mandible is recommended. The purpose of this study was to examine the relationship between the morphology of the temporomandibular joints and asymmetry in skeletal Class III malocclusion in adult female patients. Cephalometric and laminographic findings in 36 asymmetric skeletal Class III patients with a lateral shift of mandible (group 3) were compared to those of 25 symmetric skeletal Class I patients (group 1) and the same number of symmetric skeletal Class III malocclusions (group 2). All the patients had received no orthodontic treatment. The results showed that the TMJ of the side to which the mandible shifted showed a significantly narrower and shorter shape of the condyle head, smaller superior condylar space, and steeper eminence than those of the unshifted side.     

女性骨性Ⅱ类高角患者牙合平面与上下颌骨矢状向位置关系的相关性研究

目的 探讨女性骨性Ⅱ类高角患者牙合平面与上下颌骨矢状向位置关系之间的相互关系。方法 选取48例成人女性骨性Ⅱ类高角患者正畸治疗前头颅侧位片,各测量27项指标。应用Pearson相关分析上下颌骨矢状向位置关系与牙合平面指标、牙合平面指标与牙齿指标的相关性。结果 ANB角与后牙牙合平面倾斜度（OPP-FH）相关性显著。OPP-FH与上颌第二磨牙垂直高度及倾斜度相关性显著。结论 女性骨性Ⅱ类高角患者上下颌骨矢状向位置关系与后牙牙合平面倾斜度关系密切。     

Dentoskeletal treatment changes in Class II subdivision malocclusions in submentovertex and posteroanterior radiographs.

The objective of this study was to evaluate the dentoskeletal changes consequent to orthodontic treatment in subjects with Class II subdivision malocclusions, treated with asymmetric extractions, compared with a normal-occlusion control group. The sample consisted of 3 groups, with 30 subjects in each: normal-occlusion subjects (group 1), untreated Class II subdivision subjects (group 2), and Class II subdivision patients treated with asymmetric extractions (group 3). All subjects had a full complement of permanent teeth at the beginning of treatment. The average ages of the subjects were 22.42, 15.76, and 18.57 years, respectively, in groups 1, 2, and 3. Measurements of relative differences in the spatial position of dental and skeletal bilateral landmarks were obtained from the submentovertex and posteroanterior cephalometric (PA) radiographs. The t test for independent samples was used to compare group 1 with groups 2 and 3 at different times. Results from the submentovertex radiograph showed that asymmetric extractions in Class II subdivision malocclusions will maintain the differences in the anteroposterior positions of right and left, maxillary and mandibular first molars, as would be expected with the treatment protocols used. There were no significant skeletal changes that could be attributed to the treatment approaches investigated or transverse collateral effects with the asymmetric mechanics used. It was also demonstrated that treatment of Class II subdivision malocclusions with asymmetric extractions produced corrections of maxillary and mandibular dental midline deviations with the midsagittal plane, without canting the occlusal plane or any other investigated horizontal plane, as seen in the PA radiograph. Treatment of Class II subdivision malocclusions with asymmetric extractions constitutes a beneficial approach to this problem.     

Retrognathic maxilla in “Habsburg jaw”: Skeletofacial analysis of Joanna of Austria (1547–1578)

Objective:To evaluate the dentoskeletal features of the “Habsburg jaw” by analyzing the skull of Joanna of Austria.Materials and Methods:The skull, the panoramic radiograph, and the lateral cephalogram of Joanna of Austria were analyzed. The cephalometric values of Joanna were compared to cephalometric standards for adult female subjects.Results:The analysis of the dentition on the dry skull and on the panoramic radiograph showed a generalized horizontal alveolar bone resorption with severe bone loss that was interpreted as a sign of severe periodontal disease with respect to the young age (31 years). The cephalometric analysis revealed the presence of a skeletal Class III disharmony associated with maxillary retrusion and normal sagittal position of the mandible. The maxilla exhibited a reduction in the sagittal dimension while the mandible presented with increased dimensions both in total mandibular length (Co-Gn) and in the mandibular body (Go-Gn). The skeletal open bite contributed to the lack of mandibular protrusion though in presence of increased mandibular sagittal dimensions.Conclusion:Joanna of Austria appeared to be affected by a peculiar type of “Habsburg jaw” as the Class III skeletal disharmony was due to a retrognathic maxilla rather than to a prognathic mandible.     

个性化上颌非对称旋转矫治上颌 平面偏斜畸形

目的评估上颌非对称旋转在矫正 平面偏斜不对称畸形患者中的应用。总结治疗面部不对称畸形患者的经验,为临床治疗面部不对称畸形提供参考。 方法选取32例 平面偏斜的面部不对称畸形患者,拍摄术前螺旋CT及术前、术后头颅正位片,术前在计算机辅助下模拟手术,设计个性化手术方案,不对称旋转上颌 平面,并将模拟数据用于手术中。采用配对t检验进行统计学分析比较术前、术后面部外形差异。 结果32例患者面部形态及功能均取得了良好的治疗效果,无术中及术后并发症发生,软硬组织取得良好对称性,面部外形协调美观。术后双侧上颌骨高度差异[（0.6 ± 0.5）mm]小于术前上颌骨高度差异[（4.7 ± 1.5）mm],差异有统计学意义（t= 15.172,P<0.001）。术后<平面偏斜度[（0.5 ± 0.5）°]小于术前<平面偏斜度[（4.4 ± 1.7）°],差异有统计学意义（t= 12.934,P<0.001）。术后非对称率[（0.7 ± 0.6）%]小于术前非对称率[（5.5 ± 1.7）%],差异有统计学意义（t= 15.640,P<0.001）。 结论（1）数字化计算机辅助外科技术能够模拟手术过程,设计手术方案,重建术后软硬组织形态并指导正颌手术的准确截骨;（2）上颌非对称旋转能够矫正上颌 平面偏斜畸形,达到面部软硬组织对称协调,改善面部不对称畸形。     

Three-dimensional evaluation of skeletal and dental asymmetries in Class II subdivision malocclusions.

The objective of this study was to determine if any significant differences existed with regard to dental and skeletal asymmetries between subjects with Angle Class II subdivision malocclusions and subjects with normal occlusions. The sample consisted of 30 subjects in each of the 2 groups. Each possessed a full complement of permanent teeth, including first molars. The average age of subjects was 15.76 years in the Class II subdivision group and 22.42 years in the normal occlusion group. Measurements were obtained with the use of submentovertex, posteroanterior, and corrected oblique cephalometric radiographs. In the submentovertex radiographs, symmetry was assessed by measuring the relative differences in the spatial positions of dental and skeletal landmarks between the right and the left sides in both anteroposterior and transverse dimensions. Coordinate systems were used to represent the mandible, cranial floor, and the maxilla. In the posteroanterior radiographs, symmetry was assessed similarly by measuring the relative differences in the spatial positions of dental and skeletal landmarks between the right and the left sides. In the corrected oblique radiographs, symmetry was assessed by measuring the differences in size of dental and skeletal structures between the right and the left sides. Variables were analyzed with multivariate logistic regression analysis. The results demonstrated that the primary contributor to the differences between the 2 groups was the distal positioning of the mandibular first molars on the Class II side in patients whose mandibles showed no unusual skeletal or positional asymmetries. A secondary contributor was the mesial positioning of the maxillary first molars on the Class II side. Furthermore, the posteroanterior radiographic analysis showed that the more frequent distal positioning of the mandibular molars on the Class II side, compared with the mesial positioning of the maxillary molars on that side resulted in mandibular dental midline deviation to the Class II side more frequently than the maxillary dental midline to the opposite side.     

Morphologic characteristics of the dentition and palate in cases of skeletal asymmetry

The purpose of this study was to clarify the three-dimensional morphological characteristics of the dentition and palate in skeletal asymmetry in patients with skeletal Class III malocclusion using a newly defined palatal reference plane in a dental cast. Twenty patients (5 males and 15 females) who had skeletal Class III malocclusion with facial asymmetry were selected. Pretreatment posteroanterior cephalometric radiographs and maxillary dental casts were used. The lateral deviation of Me was measured as the distance from a line perpendicular to Lo-Lo' that passed through CG. The angle between the Lo-Lo' plane and the J-J' plane was measured. Each maxillary dental cast was measured using a three-dimensional surface-scanning system, and the newly defined palatal reference plane was calculated. The right/left difference in the radius of curvature of the palate and right/left differences in the vertical and mesiodistal positions of the first molars were analyzed. Linear correlation and regression techniques were used. Our findings demonstrate that the lateral deviation of the mandible is closely related to the morphology of the alveolar process and to the vertical height of the dentition. In this study, the three-dimensional application of a new palatal reference plane is very useful in morphological research, and the results provide detailed information on the characteristics of facial asymmetry.     

Ⅲ类错(牙合)下颌偏斜正畸疗效的初步分析

目的 探讨Ⅲ类错(牙合)牙性、功能性和轻度骨性下颌偏斜的正畸矫治效果,为临床治疗提供参考.方法 选择Ⅲ类错(牙合)牙性、功能性和轻度骨性下颌偏斜患者共35例,男性14例,女性21例,年龄7～22岁(平均16.5岁).牙性偏斜主要通过扩大上颌牙弓,促使下颌自动复位;功能性下颌偏斜应用双颌式功能矫正器或不对称性前方牵引和Ⅲ类颌间牵引进行治疗;轻度骨性下颌偏斜行拔牙正畸掩饰性治疗.结果 通过正畸临床矫治,22例Ⅲ类错(牙合)牙性和功能性下颌偏斜患者的颜面外形和咬合均达到满意的疗效.13例Ⅲ类错(牙合)骨性下颌偏斜患者,拔牙掩饰性正畸矫治仅可改善颜面美观.结论 Ⅲ类错(牙合)牙性和功能性下颌偏斜是正畸治疗的适应证;而对于Ⅲ类错(牙合)轻度骨性下颌偏斜的患者,单纯正畸治疗仅可减轻牙(牙合)畸形的程度.     

Total maxillary arch distalization by using headgear in an adult patient:: Reconsidering the traditional strategy in modern orthodontics

Although headgear is rarely used in adult patients, its use in adults is mainly for anchorage control. In the current case report, a 24-year-old patient had a skeletal Class I relationship with a Class II tendency, brachyfacial pattern, significant facial asymmetry, and dental 3/4 cusp Class II molar and canine relationships on both sides. The patient declined surgery, and facial asymmetry was not his concern. The final treatment goal was to achieve a stable Class I dental relationship and normal occlusion without significantly compromising the patient''s profile. The patient was compliant with the use of cervical-pull headgear after he refused the options of orthodontic-orthognathic combined treatment, maxillary premolar extraction, or temporary skeletal anchorage mini-implants. A 5-mm maxillary arch distal movement was accomplished without significant distal tipping of the molar crowns. The active treatment duration was 31 months. Proper overbite and overjet, balanced occlusion, and an acceptable facial profile were achieved. The treatment results inspire reconsideration of the possibility of using headgear in dental Class II correction in adult patients.     

正颌手术对颌面硬组织对称性改变的三维评估

目的 通过锥形束CT（cone beam computed tomography,CBCT）研究正颌手术对成人骨性Ⅲ类错牙合伴颜面部不对称患者治疗的疗效。方法 选择正畸临床成人骨性Ⅲ类错牙合伴颜面部不对称患者20例,20例患者均采用正畸-正颌联合治疗的方法,在正畸前（T0）和正颌手术后6个月（T1）后使用CBCT对患者进行三维扫描获得颅面部DICOM数据,采用Dolphin 11.0对颌骨进行三维重建,选择描述颌骨骨性结构特征的20个点进行描记,测量分析20个变量。结果 20例颜面部不对称患者,正颌手术改善上颌骨下部水平向及矢状向的不对称性,双侧下颌体的长度及下颌支的倾斜度得到纠正。结论 正颌手术能有效改善成人颜面部不对称,对成人骨性Ⅲ类错牙合伴颜面部不对称患者的改善主要表现在上颌骨下部水平向及矢状向的对称性改善,以及下颌体长度不协调的纠正,正颌手术前三维测量对正颌治疗方案的制定及预后的判断至关重要。     

Early developmental traits in class II malocclusion

The occlusal traits of Class II occlusion in the deciduous dentition include distal terminal plane of the second deciduous molars, distal canine relation, large overjet, and large overbite. Other findings are narrow upper dental arch and maxillary base and poor anterior spacing. Skeletally, Class II children differ less from normal children. The cranial base, including the base flexure, and the maxilla are normal. The mandibular corpus and lower facial height are short, the gonial angle is large, and the dentoalveolar position of the mandible is retruded. The height of the ramus is normal, as is the skeletal position of the mandible, with the exception of the chin, which becomes slightly retruded after 5 years of age. As most skeletal traits of Class II occlusion develop later than the occlusal characteristics, it is suggested that no evidence can be found for a skeletal Class II growth pattern in the deciduous dentition. The deficient transversal growth of the maxilla and the sagittal growth of the mandible seem to cause the typical Class II occlusion. Further skeletal changes are likely to develop as secondary adaptations.     

Early developmental traits in Class II malocclusion

The occlusal traits of Class II occlusion in the deciduous dentition include distal terminal plane of the second deciduous molars, distal canine relation, large overjet, and large overbite. Other findings are narrow upper dental arch and maxillary base and poor anterior spacing. Skeletally, Class II children differ less from normal children. The cranial base, including the base flexure, and the maxilla are normal. The mandibular corpus and lower facial height are short, the gonial angle is large, and the dentoalveolar position of the mandible is retruded. The height of the ramus is normal, as is the skeletal position of the mandible, with the exception of the chin, which becomes slightly retruded after 5 years of age. As most skeletal traits of Class II occlusion develop later than the occlusal characteristics, it is suggested that no evidence can be found for a skeletal Class II growth pattern in the deciduous dentition. The deficient transversal growth of the maxilla and the sagittal growth of the mandible seem to cause the typical Class II occlusion. Further skeletal changes are likely to develop as secondary adaptations.