Peridental bone changes after orthodontic tooth movement with fixed appliances: A cone-beam computed tomographic study

Objective:To quantify treatment-related changes in peridental bone height and thickness in orthodontic patients.Materials and Methods:Cone-beam computed tomographs (CBCTs) of 43 patients (24 female, 19 male; mean age: 25 years, 5 months) who underwent orthodontic treatment with multibracket appliances for at least 1 year were chosen for retrospective evaluation. Dehiscence depth and changes in bone width and tooth inclination were determined for 954 teeth.Results:There was a significant decrease in peridental bone height (dehiscence; −0.82 ± 1.47 mm) and bone thickness (−0.56 ± 0.7 and −0.69 ± 0.9 mm at 5 mm and 10 mm apical to the CEJ, respectively) during treatment (P < .001). A significantly greater dehiscence depth with increased vertical bone loss occurred in patients older than 30 years. In patients <30 years old, approximately 20% of the teeth showed defect depths >2 mm before treatment. In 90% of these patients, at least one tooth was affected. The maxillary canines and all mandibular teeth showed a higher risk for vestibular bone loss. Treatment changes in tooth inclination were correlated with horizontal bone loss.Conclusions:Based on these results, it seems reasonable to recommend that peridental bone in orthodontic patients older than 30 be evaluated on a routine basis due to the risk of increased vertical bone loss. Ninety percent of patients younger than 30 showed reduced bone height (dehiscence) of the periodontium of at least one tooth.     

Assessment of condylar changes after orthognathic surgery using computed tomography regional superimposition

This study aimed to investigate the effects of bimaxillary advancement orthognathic surgery on the condylar remodeling of the temporomandibular joint (TMJ) using voxel-based regional superimposition of cone-beam computed tomography (CBCT).In this retrospective study, the sample comprised 56 condyles from 28 healthy patients (aged from 16 to 50 years) with mandibular retrognathism treated with bimaxillary advancement. CBCT scans were taken preoperatively and at 14.3 ± 4.2 months postoperatively. The scans at the two time points were superimposed using regional voxel-based registration to assess condylar changes in the follow-up period. The linear alterations were measured in six different areas of each condyle to determine the pattern of condylar remodeling.Although no significant correlation was observed between changes in condylar surfaces, bone resorption occurred predominantly in the posterior and superior regions, while bone formation was predominantly on the anterior surface. Medial and lateral surfaces presented fewer bone changes. The overall bone changes were smaller than 1 mm bilaterally in 21 patients (75%) and, considering each condyle individually, were smaller than 1 mm in 48 condyles (85.7%).The results suggested that mild condylar remodeling in healthy patients is a common finding after orthognathic surgery. Future studies may clarify the mechanisms involved in the remodeling and help to understand the reasons for the remodeling pattern.     

Three-dimensional alterations in pharyngeal airspace,soft palate,and hyoid bone of class II and class III patients submitted to bimaxillary orthognathic surgery: A retrospective study

IntroductionThe aim of this retrospective study was to evaluate changes in pharyngeal airway space (PAS), soft palate, and hyoid bone position after bimaxillary orthognathic surgery in skeletal Class II and Class III patients.MethodsPatients were divided into Group 1: Class III patients who underwent maxillary osteotomies and mandibular setback surgery (N = 43); and Group 2: Class II patients who underwent maxillomandibular advancement surgery (N = 36). Cone beam computed tomography (CBCT) images were acquired one month before and six to eight months after orthognathic surgery. PAS area, volume and minimum axial area (MAA), soft-palate morphology, and hyoid bone position measurements obtained before and after orthognathic surgery were compared using the Gamma family test (p ≤ 0.10).ResultsIn Class II group the maxillomandibular advancement surgery significantly increased the PAS area, volume, and MAA and significantly affected hyoid bone position and soft-palate morphology. In Class III group, maxillary osteotomies and mandibular setback also showed increase in PAS area, however without statistically significant values for most of the evaluated measurements.ConclusionThe results of the present study indicate that PAS and related structures are expected to be improved in Class II patients submitted to bimaxillary surgery, and they are not negatively affected by bimaxillary surgery in Class III patients.     

正颌外科术后髁状突移位的三维CT研究

目的 探讨正颌手术后髁状突在三维方向上位置变化的规律。方法 应用3-DCT观查了正颌手术矫正的患者10例。结果 CT片上横断面双侧髁突角的变化统计学分析有显著性差异,而冠状面值变化无差异。多元逐步回归检验结果只有横断面左侧髁状突的角度变化可构成方程,入方程的变量为左右移动幅度。结论 在冠状面上髁状突内外无明显移位,而横断面上髁状突长轴发生了旋转。髁状突移位与左右移动幅度显著相关,与原下颌骨形态、下颌骨前后及上下移动幅度无关。     

Variation between natural head orientation and Frankfort horizontal planes in orthognathic surgery patients: 187 consecutive cases

The purpose of this study was to assess the relationship between the Frankfort horizontal (FH) and natural head orientation (NHO), their correlation between patients’ malocclusion, and the impact of counterclockwise rotation (CCW) on the FH-NHO angle variation after orthognathic surgery. An evaluation of 187 consecutive patients was performed at the Maxillofacial Institute (Teknon Medical Center, Barcelona). FH-NHO° was measured pre- and postoperatively at 1 and 12 months, after three-dimensional (3D) superimposition using a software (Dolphin®). Patients were classified as follows: 3.2%, 48.7% and 48.1%, class I, II and III, respectively. Baseline FH-NHO° was significantly positive for patients with dentofacial deformities (2.73° ± 4.19 (2.12–3.33°, P < 0.001). The impact of orthognathic surgery in FH-NHO° was greater in class II when compared with class III patients, with a variation of 2.04° ± 4.79 (P < 0.001) and −1.20° ± 3.03 (P < 0.001), respectively. FH-NHO° increased when CCW rotational movements were performed (P = 0.006). The results of this study suggest that pre- and postoperative NHO differs from FH in orthognathic patients. The angle between FH and NHO is significantly larger in class III than in class II patients at baseline, which converges after orthognathic surgery when CCW rotation is performed. Therefore, NHO should be used as the real horizontal plane when planning for orthognathic surgery.     

Assessment of the temporal crest canal using cone-beam computed tomography

The temporal crest canal (TCC) is a rare variant of the mandibular canal, and it is important to locate the presence and site of mandibular canals and their variants before operation. We have examined the anatomical features and prevalence of TCC with cone-beam computed tomography (CT) in south-east Anatolia. The cone-beam CT images of 1023 patients (2026 sides) referred to the Department of Dentomaxillofacial Radiology between 2015 and 2017 years were evaluated retrospectively. Sagittal, cross-sectional, and reformatted panoramic images were analysed to see if a TCC was present. The canals were grouped as Type 1 and Type 2 according to their configuration. Seven (0.7%) were found in 1023 patients. Two of them (0.2%) were in female, and five (0.5%) in male, patients. Four (0.4%) were increasingly narrow and noticeably curved (Type 1), and three (0.3%) were uniformly wide and slightly curved (Type 2). All TCC were unilateral: two on the right and five on the left. We conclude that knowledge of the presence of a TCC and its anatomical variants in the mandibular ramus is important to ensure a proper local anaesthetic nerve block for surgical operations. Cone-beam CT is an important diagnostic tool in dentistry, and clearly recognises a TCC.     

锥形束CT转化头颅侧位片定点精确性的研究

Objective In this study, we compared the precision of landmark identification using cephalograms from cone-beam computed tomographic (CBCT) volumes and conventional lateral cephalograms (Ceph). Methods Twenty pre-orthodontic patients were radiographed with conventional Ceph and CBCT techniques. CBCT data was uploaded into InvivoDental software 5.0 to generate cephalograms(CCB). Three observers plotted 23 landmarks using computer displays of CCB and Ceph views during separate sessions. Absolute differences between CCB and Ceph of all observers were measured. The absolute difference between each observer was also measured. ANOVA and paired t tests were used to analyze variability differences. Results The difference of landmark identification between CCB and Ceph were significant at P＜0.05 calculations. 8 landmarks variability was statistically greater than Ceph views. The variability of CCB for each observer was consistently greater than in Ceph. The overall correlation of CCB and Ceph measurements was excellent at 0.99.Conclusions The CCB displays of CBCT volume images provide generally more precise identification than Ceph. More precise location of basion, porion, orbitale, ANS, A point, Gonion and tooth apex overcomes the problem of superimposition of these bilateral landmarks seen in Ceph. Greater variability of certain landmarks is probably related to inadequate definition of the landmarks in the third dimension.     

锥形束CT转化头颅侧位片定点精确性的研究

Objective In this study, we compared the precision of landmark identification using cephalograms from cone-beam computed tomographic (CBCT) volumes and conventional lateral cephalograms (Ceph). Methods Twenty pre-orthodontic patients were radiographed with conventional Ceph and CBCT techniques. CBCT data was uploaded into InvivoDental software 5.0 to generate cephalograms(CCB). Three observers plotted 23 landmarks using computer displays of CCB and Ceph views during separate sessions. Absolute differences between CCB and Ceph of all observers were measured. The absolute difference between each observer was also measured. ANOVA and paired t tests were used to analyze variability differences. Results The difference of landmark identification between CCB and Ceph were significant at P＜0.05 calculations. 8 landmarks variability was statistically greater than Ceph views. The variability of CCB for each observer was consistently greater than in Ceph. The overall correlation of CCB and Ceph measurements was excellent at 0.99.Conclusions The CCB displays of CBCT volume images provide generally more precise identification than Ceph. More precise location of basion, porion, orbitale, ANS, A point, Gonion and tooth apex overcomes the problem of superimposition of these bilateral landmarks seen in Ceph. Greater variability of certain landmarks is probably related to inadequate definition of the landmarks in the third dimension.     

锥形束计算机体层摄影术在牙槽外科中的应用

牙槽外科为口腔颌面外科的一部分,但其不仅局限于颌面外科专业,而且涉及多学科的基础治疗方法。因此．牙槽外科手术越来越受到学者们的重视。锥形束计算机体层摄影术（CBCT）是当今最有前途和实用性的口腔颌面影像设备,它的应用给口腔颌面部疾病的诊断和治疗带来了革命性的变化,使口腔临床诊断变得更加容易、更加准确,其不仅克服了曲面断层片的局限,同时还避免了传统cT诸多不足．因而在牙槽外科中得到越来越广泛的应用。本文结合国内外最新研究成果．对CBCT的优势及其在牙槽外科各领域中的应用做一综述。     

锥形束CT在牙体牙髓病诊治中的临床应用

锥形束CT(CBCT)作为一种新型高分辨率X线成像系统,因扫描速度快、空间分辨率高、辐射剂量小、图像伪影少等优点,在口腔医学领域获得越来越广泛的应用.本文就CBCT在牙体牙髓病诊治中的应用作一综述.     

上颌窦内壁分隔的 CBCT 观测

目的：通过CBCT观测上颌窦内壁间隔的解剖特点及分布规律。方法：调取苏州口腔医院放射科接受CBCT扫描的汉族患者的CT图像资料360例。 Mimics 17．0软件对上颌窦进行三维重建。对上颌窦间隔的发生率、数目、形态、位置及双侧分布状况进行观测。结果：360例中,上颌窦间隔的人群总发生率为37．8％,双侧发生占34．6％,双侧相关系数tau值为0．357（P＜0.01）。分布位置常位于磨牙区。不同性别组、年龄组、牙列缺失缺损及牙列完整组间发生率的差异无统计学意义（P＞0．05）。结论：上颌窦间隔在汉族人具有较高的发生率,了解其解剖特点及分布规律具有重要的临床意义。     

锥形束CT转化头颅侧位片定点精确性的研究

目的 研究对比锥形束计算机断层扫描（Cone-beam computed tomography,CBCT）转化的头颅侧位片与传统头颅侧位片（Cephalogram,Ceph）的定点精度.方法 对20名需要正畸的患者（男7名,女13名,平均年龄18.8岁）进行锥形束CT扫描,同时拍摄Ceph作为对照.在InvivoDental 5.0软件中按统一条件将CBCT数据转化成头颅侧位片（Cephalogram from CBCT,CCB）.选择23个常用标志点,由三名操作者分别对CCB与Ceph进行定点,间隔进行两次.对CCB与Ceph上的定点误差,以及不同操作者之间的定点误差进行统计分析,采用方差分析与t检验.结果 三名操作者在CCB上定点的精度明显优于Ceph（P＜0.05）,19个定点的精度有8个点的定点误差差异有显著性（P＜0.05）.操作者之间的相关性CCB比Ceph好.操作者自身两次测量值重复性好,相关系数0.99.结论 CCB由于可以选择性生成单侧或双侧头颅侧位片,定点的精度普遍要优于Ceph,尤其是颅底点（Ba）,耳点（P）,眶点（O）,前鼻棘（ANS）点,上齿槽座点（A）,下颌角点（Go）,以及切牙及磨牙根尖点在CCB上的定点更精确.对于一些定点误差较大的点可能是由于在三维空间中点的定义还不明确.     

A novel success scale for evaluating alveolar cleft repair using cone-beam computed tomography

PurposeRadiographic scales, based on plain radiographs, for the evaluation of alveolar cleft repair, have certain weaknesses and are thought to overestimate to some degree the success of the surgical intervention. The aim of this study was the presentation of a novel success scale for evaluating alveolar cleft repair using cone-beam computed tomography (CBCT).Materials and methodsPatients treated with secondary osteoplasty for unilateral or bilateral alveolar cleft were evaluated using the Bergland and Enemark scales, as well as the novel success scale, which measures the bone height, the bone width and the level of the nasal floor.ResultsA total of 44 patients with a total of 53 alveolar cleft sites were included. According to the new scale, 60% of the cases were defined as successful, with moderate (kappa = 0.511) or substantial (kappa = 0.718) agreement, between the new scale and the Bergland or Enemark scale, respectively. Statistically significant correlation was reported between the new success scale and the closure of space of the lateral incisor, the patient's age at surgery, the graft revision and the presence of residual fistula.ConclusionsThe novel success scale for evaluating alveolar cleft repair using CBCT takes into consideration all dimensions of the bony bridge. Future application is necessary for validation of its potential value.     

Reliability of different three-dimensional cephalometric landmarks in cone-beam computed tomography: A systematic review

Objectives:Conventional two-dimensional (2D) cephalometric radiography is an integral part of orthodontic patient diagnosis and treatment planning. One must be mindful of its limitations as it indeed is a 2D representation of a vaster three-dimensional (3D) object. Issues with projection errors, landmark identification, and measurement inaccuracies impose significant limitations, which may now be overcome with the advent of cone-beam computed tomography (CBCT). A systematic review of the reliability of different 3D cephalometric landmarks in CBCT imaging was conducted.Materials and Methods:Electronic database searches were administered until October 2017 using PubMed, MEDLINE via OvidSP, EBMR and EMBASE via OvidSP, Scopus, and Web of Science. Google Scholar was used as an adjunctive search tool.Results:Thirteen articles considering CBCT scans of human subjects from preexisting data sets were selected and reviewed. Most of the studies had methodological limitations and were of moderate quality. Because of their heterogeneity, key data from each could not be combined and were reported qualitatively. Overall, in 3D, midsagittal plane landmarks demonstrated greater reliability compared with bilateral landmarks. A minimum number of dental landmarks were reported, although most were recommended for use.Conclusions:Further research is required to evaluate the reliability of 3D cephalometric landmarks when evaluating 3D craniofacial complexes.     

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。     

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.     

Masseter muscle changes following orthognathic surgery: A long-term three-dimensional computed tomography follow-up

Objective:To evaluate the long-term changes of masseter muscle morphology in skeletal Class III patients with facial asymmetry following two-jaw orthognathic surgery (Le Fort I osteotomy + intraoral vertical ramus osteotomy).Materials and Methods:Using computed tomography (CT), a longitudinal study was conducted on 17 skeletal Class III patients with facial asymmetry. Measurements from the reconstructed three-dimensional (3D) CT images were compared from T1 (before surgery), T2 (1 year after surgery), and T3 (4 years after surgery). The maximum cross-sectional area (CSA), orientation, thickness, and width of the masseter muscle were measured on both the deviated and nondeviated sides. The control group included 17 volunteers with skeletal and dental Class I relationships without dentofacial deformities.Results:At T1, there were no significant differences in CSA, thickness, or width of masseter muscle between the deviated and nondeviated sides. Masseter muscle orientation was significantly more vertical on the nondeviated side than on the deviated side at T1 (P < .01); no significant bilateral differences were noted at T2 and T3. At T1, masseter muscle measurements were significantly lower than controls (P < .01). During T1–T3, a significant increase was noted in CSA, thickness, and width (P < .01) of masseter muscle. At T3, no significant difference was noted between the study and control groups.Conclusion:After surgery, the masseter muscle measurements of skeletal Class III asymmetry patients showed no significant differences compared with the control group within the 4-year follow-up period, indicating adaptation to the new skeletal environments and increased functional demand.     

锥形束CT在治疗上颌前牙区埋伏牙中的应用

目的:探讨锥形束CT(CBCT)在治疗上颌前牙区埋伏牙中的临床应用价值。方法:收集我院2009—2010年经普通X线片确定有埋伏牙,但不易具体定位的患者11例,进行CBCT扫描和三维重建,确定埋伏牙在颌骨内的具体位置。结果:经CBCT扫描、三维重建后,所有患者均可直观再现埋伏牙的形态、数目、在颌骨中的具体位置和发育情况。11例患者共16颗埋伏牙,其中既有埋伏阻生牙又有埋伏多生牙,3例(4颗)为埋伏多生牙,1例有2颗埋伏牙;2例为倒置埋伏,2例为水平埋伏,3例为垂直埋伏,4例为斜位埋伏。根据CBCT结果制订治疗方案,获得满意的治疗效果。结论:CBCT三维重建对于上颌前牙区埋伏牙治疗方案的设计及实施具有重要意义。     

Influence of cone-beam computed tomography image artifacts on the determination of dental arch measurements

Objective:To compare dental plaster model (DPM) and cone-beam computed tomography (CBCT) in the measurement of the dental arches, and investigate whether CBCT image artifacts compromise the reliability of such measurements.Materials and Methods:Twenty patients were divided into two groups based on the presence or absence of metallic restorations in the posterior teeth. Both dental arches of the patients were scanned with the CBCT unit i-CAT, and DPMs were obtained. Two examiners obtained eight arch measurements on the CBCT images and DPMs and repeated this procedure 15 days later. The arch measurements of each patient group were compared separately by the Wilcoxon rank sum (Mann-Whitney U) test, with a significance level of 5% (α  =  .05). Intraclass correlation measured the level of intraobserver agreement.Results:Patients with healthy teeth showed no significant difference between all DPM and CBCT arch measurements (P > .05). Patients with metallic restoration showed significant difference between DPM and CBCT for the majority of the arch measurements (P > .05). The two examiners showed excellent intraobserver agreement for both measuring methods with intraclass correlation coefficient higher than 0.95.Conclusion:CBCT provided the same accuracy as DPM in the measurement of the dental arches, and was negatively influenced by the presence of image artifacts.     

Impact of orthognathic surgery on the prevalence of dehiscence in Class II and Class III surgical-orthodontic patients:: A cone beam computed tomographic study

ObjectivesThe objectives were to evaluate and compare the presence of bone dehiscence before and after orthognathic surgery.Materials and MethodsIn this retrospective study, 90 cone-beam computed tomography (CBCT) scans from 45 patients were evaluated. Class II (n = 23) and Class III (n = 22) orthodontic patients who were being prepared for orthognathic surgery were measured. CBCT scans were obtained about 30 days prior to (T0) and 6 months after (T1) double jaw orthognathic surgery. The distance between the cemento-enamel junction (CEJ) and the alveolar bone crest was assessed at the buccal and lingual surfaces of all teeth, on both sides and arches, except for the second premolars and the second and third molars. A total of 1332 sites were measured for Class II (644) and Class III (688) patients. The software used was OsiriX (version 3.3 32-bit). Data were compared with Wilcoxon and McNemar tests at the 5% level.ResultsBone dehiscence before surgery was present in 26% and 15% of the Class II and III groups, respectively. The presence of dehiscence increased to 31% in the Class II and 20% in the Class III patients after surgery (P < .05).ConclusionsThe prevalence of dehiscence increased slightly in Class II and Class III surgical-orthodontic patients after orthognathic surgery. Temporary vascular supply reduction and oral hygiene difficulties may explain these results; however, more studies are needed.