Three-dimensional morphological characterization of malocclusions with mandibular lateral displacement using cone-beam computed tomography

Objective: The purpose of this study was to evaluate the morphologic characteristics of MLD malocclusions using 3D imaging.

Materials and methods: MLD characteristics were examined using CBCT data in 40 subjects. A 3D Cephalometric analysis was developed to describe the spatial position of the mandible and temporal bones.

Results: Vertical dental heights were shorter and the posterior occlusal plane (POP) presented a steeper sagittal inclination on the shifted side (the side of the laterally displaced bony chin) than on the contralateral side. (p < 0.01). The MLD was related to a superiorly inclined POP Cant in the same direction (r = 0.82; p < 0.01). The shifted side condyle was dislocated medially and was smaller. Temporal bone sagittal inclination showed a more forward and medial inclination on the contralateral side (p < 0.01).

Conclusions: A unilateral decrease in the vertical height of the dentition and the subsequent steeper occlusal plane inclinations correlated with (1) mandibular rotational displacement and condylar lateral displacement, (2) mandibular and condylar morphologic changes (3) changes in temporal bone position.     

Evaluation of mandibular volume using cone-beam computed tomography and correlation with cephalometric values

Objective:To investigate the association between maxillofacial morphology and mandibular bone volume in patients with skeletal malocclusion.Materials and Methods:Subjects were 118 adult Japanese (58 males and 60 females). Skeletal malocclusion was classified, based on cephalometric analysis, into skeletal Classes I (−1° ≤ ANB < 4°), II (ANB ≥ 4°), and III (ANB < −1°). Using cone-beam computed tomography and three-dimensional image analysis software, the dental crowns and mandible were separated, with only the mandible extracted. This was then reconstructed as a three-dimensional model, from which the mandibular volume was measured.Results:No significant difference in mandibular volume was noted among skeletal Classes I, II, and III, nor was there any significant correlation between mandibular volume and the ANB, SNB, or mandibular plane angles. There was occasional and limited correlation between mandible volume and gonial angle and certain cephalometric distance parameters.Conclusion:We conclude that proper understanding of the three-dimensional maxillofacial morphology requires not only cephalometric radiographic tracings but also high-resolution analysis of the mandibular area, width, and volume.     

Morphological variations of mandibular first premolar on cone-beam computed tomography in a Saudi Arabian sub-population

In-depth knowledge of common and aberrant pulp morphology is essential for appropriate diagnosis and treatment planning prior to commencing root canal treatment. Radicular morphology of mandibular premolars has been extensively studied. Considerable variation in the number of canals and roots found in these teeth has been reported.AimThe purpose of this study is to investigate the root and root canal morphology of mandibular first premolar among Saudi Arabian subpopulation in Aseer using CBCT.MethodsCone-beam computed tomography images of Mandibular first premolar were taken from 166 patients which were referred to Armed Forces Hospitals Southern Region (AFHSR), Khamis Mushayt, Asir region Saudi Arabia. All the images were assessed by two Evaluators (An Endodontist and a Radiologist). Inter-examiner reliability was determined and was assessed by KAPPA value.ResultsThe mandibular first premolar (n = 216) distributed as 120 teeth in female and 96 teeth in male. Out of the 120 teeth examined in female groups one canal was seen in 95 (79.2%) teeth, two canals in 19 (15.8%) teeth and three canals in 6 (5%) teeth where as in the Male group out of 96 teeth, 52 (54.1%) teeth showed one canal, 32 (33.3%) teeth with two canals whereas 12 (12.5%) teeth showed presence of three canals.Chi-Square test for mandibular first premolars demonstrated the chance of second canal in the mandibular first premolar more in male than female and these differences was statistically significant (P ≤ 0.05).ConclusionEndodontic therapy of mandibular premolars is a challenge for clinician because of their frequent morphological and anatomical abnormalities. Proper knowledge about number of root canals and canal configuration is a key to success in Endodontic. There is a great variability in different population regarding the root canal configuration in mandibular pre-molars. However, most studies state the mandibular first premolar has one root canal. Also, the most prevalent type of root canal found was Type I vertucci.     

Evaluation of mandibular volume classified by vertical skeletal dimensions with cone-beam computed tomography

Objective:To investigate the relationship between anteroposterior and vertical differences in maxillofacial morphology and mandibular volume.Materials and Methods:Subjects comprised 213 Japanese adults (84 males and 129 females) who were divided into three groups based on mandibular basal arch (ANB) and Wits, measured in a cephalometric analysis: Class I (−1° ≤ ANB < 4°,−1 mm ≤ Wits < 0 mm), Class II (ANB ≥ 4°, Wits ≥ 0), and Class III (ANB <−1°, Wits <−1 mm). Subjects were also divided into three groups based on the mandibular plane angle (Mp), as follows: hypodivergent (Mp < 23°), normodivergent (Mp  =  23–30°), and hyperdivergent (Mp > 30°) groups. Mandibular volume was measured from cone-beam computed tomographic images that were analyzed using Analyze™ image processing software and compared among the three groups in each classification.Results:No significant differences were noted in mandibular volume among Classes I, II, and III. An inverse relationship was found between mandibular volume and Mp, and a significant difference was noted in mandibular volume between the hypodivergent and hyperdivergent groups.Conclusions:In addition to two-dimensional analysis, such as lateral cephalometry, three-dimensional information such as volume, provided by cone-beam computed tomography, contributes to a more detailed assessment of maxillofacial morphology.     

锥束CT对下颌第一磨牙远舌根发生率的研究

目的：利用锥束CT三维影像调查分析下颌第一磨牙远舌根的形态及发生率,以提高根管治疗质量。方法：至少具有一侧下颌第一磨牙的469例患者927颗下颌第一磨牙被纳入研究,采用锥束CT扫描获得患者的影像资料,利用NNT version 3．0软件三维影像重建,分析下颌第一磨牙远舌根的牙根形态及发生率。结果：119例共206颗下颌第一磨牙具有远舌根,远舌根在人群中的发生率为25．4％（男性65例,占27．2％;女性54例,占23．5％）,远舌根在所有牙齿中的发生率为22．2％（206颗／927颗）。绝大多数病例双侧同时具有远舌根（87例,占18．6％）,远舌根单侧出现32例（右侧27例,占5．8％;左侧5例,占1.1％）,远舌根在不同性别（P=0．678）,左右侧（P=0．870）之间的发生率没有显著性差异。结论：中国人下颌第一磨牙远舌根的发生率比较高,其形态复杂,在临床治疗中应仔细探查远舌根管是否存在,从而提高根管治疗的成功率。     

Evaluation of the potential of automatic segmentation of the mandibular canal using cone-beam computed tomography

We aimed to investigate the effectiveness of software for automatically tracing the mandibular canal on data from cone-beam computed tomography (CT). After the data had been collected from one dentate and one edentate fresh cadaver head, both a trained Active Shape Model (ASM) and an Active Appearance Model (AAM) were used to automatically segment the canals from the mandibular to the mental foramen. Semiautomatic segmentation was also evaluated by providing the models with manual annotations of the foramina. To find out if the tracings were in accordance with the actual anatomy, we compared the position of the automatic mandibular canal segmentations, as displayed on cross-sectional cone-beam CT views, with histological sections of exactly the same region. The significance of differences between results were analysed with the help of Fisher's exact test and Pearson's correlation coefficient. When tracings based on AAM and ASM were used, differences between cone-beam CT and histological measurements varied up to 3.45 mm and 4.44 mm, respectively. Manual marking of the mandibular and mental foramina did not improve the results, and there were no significant differences (p = 0.097) among the methods. The accuracy of automatic segmentation of the mandibular canal by the AAM and ASM methods is inadequate for use in clinical practice.     

Evaluation of condyle-fossa relationships in adolescents with various skeletal patterns using cone-beam computed tomography

Objectives:To evaluate the condyle-fossa relationship in adolescents with various skeletal patterns using cone-beam computed tomography (CBCT).Materials and Methods:CBCT images obtained in 120 adolescent patients were used for this study. The patients were divided into 3 groups according to 3 criteria: (1) age (early, middle, and late adolescence); (2) facial height ratio or Jarabak quotient (hyperdivergent, normodivergent, and hypodivergent); and (3) ANB classification (Class I, Class II, and Class III). Temporomandibular joint space (TMJS: AS, anterior space; SS, superior space; PS, posterior space; MS, medial space; LS, lateral space), width and depth of the condyle (MLT, mediolateral thickness; APT, anteroposterior thickness), articular slope (ArS) and vertical height of the fossa (VHF) were measured and compared using CBCT.Results:Differences in condyle-fossa relationships were not significantly different between male and female adolescents, but were significantly different (P < .05) between left and right sides. The mean values showed no statistical differences according to age and skeletal pattern. Most measurements in the sagittal view showed that SS was the greatest, and the mean ratio of AS to SS to PS was 1.00 to 1.27 to 1.19, respectively. The mean values of coronal MS and LS were not significantly different.Conclusions:There were almost no statistical differences in the TMJS in adolescents across various factors except between left and right sides.     

下颌第二恒磨牙牙根及根管形态的锥形束CT研究

目的 使用锥形束CT扫描评估下颌第二恒磨牙牙根和根管解剖形态.方法 收集354例患者双侧下颌第二恒磨牙的锥形束CT图像,统计下颌第二恒磨牙牙根数目、根管数目和构型,以及C形根管的发生率.结果 下颌第二恒磨牙以双根最多,发生率为57.34%,C形根的发生率为38.28%;双根者近中根多为2-2型(80.54%),远中根多为1-1型(96.06%);C形根管的发生率为25.99%,左、右下颌的发生率没有统计学差异(P>0.05).结论 下颌第二恒磨牙牙根和根管解剖形态复杂多样,锥形束CT能为根管治疗提供参考.     

Accuracy of recording horizontal condylar inclination and Bennett angle with the Cadiax compact

This study assessed the accuracy of an electronic hinge axis tracing device (Cadiax compact) in measuring the horizontal condylar inclination (HCI) and the Bennett angle. The hinge axis movements were simulated with an articulator to which the hinge axis tracer was attached. On the articulator the pre-set HCI values were 20 degrees, 40 degrees and 60 degrees, the pre-set Bennett angles were 0 degrees, 5 degrees, 10 degrees, 15 degrees, 20 degrees. The maximum measuring errors ranged from 0 to 3.4 degrees (in average 1.2 degrees ) and yielded statistically significant differences between articulator setting and Cadiax compact measurement (P < 0.05) except the HCI of 40 degrees and the Bennett angle of 0 degrees. Because of the small range of the maximum measuring error the Cadiax compact represented reasonable accuracy for clinical application in anterior guidance restorations.     

Integration accuracy of craniofacial cone-beam computed tomography images with three-dimensional facial scans according to different registration areas

ObjectivesTo evaluate the integration accuracy of cone-beam computed tomography (CBCT) images with three-dimensional (3D) facial scans according to different registration areas.Materials and MethodsTwenty-five patients (14 males and 11 females), with a mean age of 19.0 ± 11.3 years, were included in this study. Each patient underwent CBCT and facial scans on the same day in an upright position. The facial scans were integrated with the corresponding soft-tissue images of CBCT scans. Three methods were used to integrate the two imaging modalities based on the facial regions scanned: R1, only the forehead and nasal bridge area were included; R2, the right and left malar area were included; and R3, the forehead, nasal bridge, and malar areas were included. The integration accuracy between the facial scans and CBCT images was evaluated by color-mapping methods and average surface distances, calculated by measuring the 3D distances between the surface points on the two superimposed images.ResultsThe average surface differences between facial scans and CBCT images were less than 1.0 mm in all three methods. The R3 method showed fewer differences between the facial scans and CBCT images than the other methods did.ConclusionsFacial scans obtained using a low-cost facial scanner showed clinically acceptable performance. The integration accuracy of facial and CBCT scans can be increased by including the forehead, nasal bridge, and malar areas as registration areas.     

青少年单侧颞下颌关节盘前移位患者面部不对称的特征

目的: 研究青少年单侧颞下颌关节盘前移位患者面部不对称畸形的特点及其与盘前移位的关系。方法：收集经磁共振确诊为单侧颞下颌关节盘前移位的10~20岁青少年单侧盘前移位连续病例,进行X线头颅定位正位片检查并测量,采用SPSS 18.0软件包,使用独立样本t检验分析左侧移位组和右侧移位组下颌骨(颏部、下颌角、髁突)、上颌骨(前鼻棘、颧牙槽嵴)和牙列(上、下牙列中点)不对称的特点。结果：105例10~20岁(平均16.76岁)青少年单侧盘前移位患者中,下颌偏斜患者67例(63.81%)。单侧盘前移位患者移位侧下颌骨垂直向高度不足,下颌角离散度增大,颏中线和上、下颌牙列中线向移位侧偏斜(P<0.05)。左侧盘前移位患者上颌骨未见显著不对称(P>0.05),右侧盘前移位患者上颌骨显著不对称(P<0.05)。结论：青少年单侧关节盘前移位患者表现出明显的面部不对称,且与单侧盘前移位患病侧紧密相关。面部不对称以下颌骨最为明显,表现为颏部偏向移位侧,以及下颌骨整体向移位侧旋转;上颌骨则表现出移位侧垂直向发育受影响的趋势。     

髁突骨软骨瘤与髁突增生患者的CT表现特点分析

目的:比较下颌骨髁突骨软骨瘤和单侧下颌骨髁突增生的CT表现特点。方法:对2005—2010年上海交通大学医学院附属第九人民医院口腔颌面外科收治的下颌骨髁突骨软骨瘤11例和单侧下颌骨髁突增生8例患者的CT影像学资料进行评价,评价指标包括病变髁突大小、病变范围以及病变周围软硬组织改变。结果:11例下颌骨髁突骨软骨瘤病例CT显示肿瘤与病变髁突无明显分界(8/11)或与患侧髁突有蒂相连(3/11);肿瘤骨皮质及骨髓腔均与患侧髁突相续,瘤体表面均有特征性薄层软骨帽覆盖,瘤体外周密度通常高于中心;瘤体周围均有薄层软组织包绕。患侧颞骨关节面表面均有明显矿化,且因受瘤体压迫改建而较对侧平坦,患侧关节上、下腔间隙较对侧明显变窄;肿瘤生长方向不尽相同。8例单侧下颌骨髁突增生病例CT显示髁突颈部和(或)下颌支延长,髁突形状改变;增生的髁突外周骨皮质均有不同程度的骨化,硬化层厚度较对侧大;骨髓腔密度较不均匀。结论:CT检查能有效提供病变髁突及其周围软硬组织情况,为鉴别诊断下颌骨髁突骨软骨瘤和单侧下颌骨髁突增生提供良好的依据。     

健康成人下颌切牙管的锥形束CT测量分析

目的 利用锥形束CT测量下颌切牙管(mandibular incisive canal,MIC),了解其形态和特点,为临床提供参考.方法 观察2011年1月至2013年1月50名成人健康志愿者的锥形束CT图像,测量分析MIC的检出率、管径、长度及其与颌骨的关系.结果 在50例(100侧)锥形束CT图像中:MIC的检出率为100％(100/100),清晰率为71％(71/100);MIC的管径面积(唇舌径×垂直径)从起点至终点逐渐变小(左侧起点2.17 mm× 2.22 mm,终点0.82 mm× 0.92 mm;右侧起点2.14 mm×2.08 mm,终点0.87 mm×0.86 mm);MIC左右侧平均长度分别为17.84和17.73 mm;MIC在下颌骨唇舌向偏唇侧;在垂直方向MIC距下颌骨下缘较近,MIC到根尖的距离在尖牙最小.结论 锥形束CT对MIC有良好的检出率和清晰率;MIC在下颌骨的走行中偏向唇侧和下颌骨下缘.     

Analysis of sagittal condylar path inclination in consideration of Fischer's angle

This study investigated the sagittal condylar path during protrusive and lateral excursions by analysing the actually measured jaw movement data and re-evaluated the setting of the sagittal condylar path inclination in consideration of Fischer's angle. Protrusive and lateral excursions of 10 healthy subjects were measured using a three-dimensional mandibular movement analysing system. Condylar path inclinations at the hinge-axis point and the corresponding external point laterally extending from the condyle were evaluated in the sagittal plane. Fischer's angle was defined as the difference between the sagittal condylar inclinations during protrusive and lateral excursions on the non-working side, by keeping the corresponding horizontal distance from the intercuspal position (ICP) equivalent at the incisal point. Analysis was performed at three different magnitudes of excursions, where the incisal point was located at 1, 3 and 5 mm away from the ICP. There was no significant difference in the sagittal condylar path inclination or the Fischer's angle between two condylar reference points. However, they were significantly different across the three different magnitudes of excursions for both condylar reference points, i.e. sagittal condylar path inclination (P = 0.003 for protrusive excursion, and P < 0.001 for lateral excursion respectively; two-way repeated-measures anova), and Fischer's angle (P = 0.013, two-way repeated-measures anova) became smaller as the incisal point became distant from the ICP. Moreover, 3- and 5-mm eccentric positions were included in the 95% CI where Fischer's angle equals zero and were considered to be clinically acceptable to adjust the sagittal condylar inclination on the semiadjustable articulators.     

150例患者下颌中切牙根管系统的锥形束CT分析

目的：运用锥形束CT分析下颌中切牙的根管数目和形态特征,为临床治疗提供参考。方法 筛选就诊于上海交通大学医学院附属第九人民医院的150例患者的CBCT图像。其中,男79例,女71例,共295颗下颌恒中切牙,对根管的数目以及形态进行分析。结果 61%的下颌中切牙具有1个根管。具有双根管的下颌中切牙占39%,其中8.8%的牙有独立的2个根尖孔。结论 本组下颌中切牙具有双根管的比例为39%,与其他有关不同人种下颌中切牙双根管的研究结果一致。     

锥形束计算机体层摄影术观察下牙槽神经管形态及其临床意义

目的 应用锥形束计算机体层摄影术（CBCT）观测并分析下牙槽神经管在下颌骨内的走行特点,探讨其分布规律,为临床手术提供解剖学依据.方法 采用单纯随机抽样法选取具备下颌后部CBCT 扫描数据的患者60 例,应用CBCT 自带的KaVo eXam Vision 软件测量颏孔区、前磨牙区、磨牙区下牙槽神经管与牙槽嵴顶、下颌骨颊舌侧骨板及下缘的平均距离,对各组测量项目进行成组t 检验比较,并观察其走行特点.结果 下牙槽神经管距下颌下缘小于距牙槽嵴顶的距离,在第二磨牙区距离下颌骨下缘最近;颏孔区至第一磨牙区间,下牙槽神经管距颊侧骨板距离小于距舌侧骨板距离,自第二磨牙后,下牙槽神经管距颊侧骨板距离则大于距舌侧骨板距离;性别及左、右侧下牙槽神经管距离差异无统计学意义（t＝2.437,P ＞ 0.05）.结论 CBCT 扫描有利于更好了解下牙槽神经管的走行及结构特异性,对牙槽外科及种植外科手术方案的制定具有一定临床指导意义.     

Nonsurgical orthodontic correction of facial asymmetry by condylar remodeling and mandibular repositioning following occlusal cant correction with microimplants: a case report

Recently, the demand for correcting facial asymmetry has been increasing, even when the extent of asymmetry is small. This case report describes nonsurgical orthodontic treatment for facial asymmetry in a 13-year-old female patient, facilitated by moving the deviant mandible to the nondeviated side after correcting for relevant dental compensation using microimplants. Mandibular repositioning was attempted using intermaxillary elastics between the microimplants placed into each jaw and guided by resin that was bonded on the maxillary first molar of the deviated side. To enhance mandibular movement, correction of the transverse occlusal cant and buccolingual inclination of the teeth were also performed. After 65 months of gradual treatment, facial symmetry, with favorable occlusion and jaw function, was achieved. These satisfactory results, including a well-balanced face and good occlusal interdigitation, were well maintained at the 53-month follow-up. Direct and functional forces applied against deviant functional forces can reduce facial asymmetry by differential growth or modeling of the condyle.