Soft tissue response to mandibular advancement using 3D CBCT scanning

This prospective longitudinal study assessed the 3D soft tissue changes following mandibular advancement surgery. Cranial base registration was performed for superimposition of virtual models built from cone beam computed tomography (CBCT) volumes. Displacements at the soft and hard tissue chin (n = 20), lower incisors and lower lip (n = 21) were computed for presurgery to splint removal (4-6-week surgical outcome), presurgery to 1 year postsurgery (1-year surgical outcome), and splint removal to 1 year postsurgery (postsurgical adaptation). Qualitative evaluations of color maps illustrated the surgical changes and postsurgical adaptations, but only the lower lip showed statistically significant postsurgical adaptations. Soft and hard tissue chin changes were significantly correlated for each of the intervals evaluated: presurgery to splint removal (r = 0.92), presurgery to 1 year postsurgery (r = 0.86), and splint removal to 1 year postsurgery (r = 0.77). A statistically significant correlation between lower incisor and lower lip was found only between presurgery and 1 year postsurgery (r = 0.55). At 1 year after surgery, 31% of the lower lip changes were explained by changes in the lower incisor position while 73% of the soft tissue chin changes were explained by the hard chin. This study suggests that 3D soft tissue response to mandibular advancement surgery is markedly variable.     

骨性Ⅲ类错正颌手术前、后面部软、硬组织变化比率的三维研究

目的 研究骨性Ⅲ类错畸形患者面部软、硬组织三维方向上变化的相关性,以及手术前、后软、硬组织的变化比率,以期更好地对术后软组织外貌进行预测。方法 对20例骨性Ⅲ类错畸形成人患者分别于术前2周及术后3个月进行颅面CT扫描和三维重建及面部软组织3D摄影成像,将采集的数据导入Dolphin软件,转换为三维面像数字化模型,建立三维测量坐标系(轴面、矢状面及冠状面),筛选19个软、硬组织标记点并进行测量、对比和配对,共12对。读取标记点的三维坐标（X、Y、Z）,进行手术前、后的定点对比测量,采用 SPSS 22.0 软件包对测量数据进行统计学分析。结果 12对软、硬组织标志点在X轴即左右方向仅Pn/A、Gn'/Gn及Me'/Me存在相关性,在Y轴即上下方向仅Gn'/Gn存在相关性,在Z轴上所有软、硬组织配对点均存在相关性。除UL'/UI及UL/SPr外,均为高度相关。手术前、后,下颌的软、硬组织测量标志点的变化比率大于上颌。结论 骨性Ⅲ类错畸形患者双颌手术前、后软、硬组织的变化主要集中于Z轴即前后向的变化,各软、硬组织配对标志点间呈线性相关关系,且下颌软、硬组织位移比率大于上颌。     

Evaluation of long-term soft tissue changes after bimaxillary orthognathic surgery in Class III patients

Objective:To assess soft tissues in the short and long term after bimaxillary surgery in Class III patients by comparing the hard tissue changes and results between time periods.Materials and Methods:Twenty-six Class III adult patients treated with bimaxillary surgery were included in the study. Cephalometric records were taken before surgery (T1) and 5 months (T2), 1.4 years (T3), 3 years (T4), and 5 years (T5) after surgery.Results:There was no significant relapse in skeletal parameters. Overjet was significantly reduced between T4-T3 time intervals (P < .01). There were significant increases in Sn-HR, ULA-HR, LLA-HR, B-B^∧ (P < .01), and B^∧-HR (P < .05) between T4-T3 time intervals. There was no significant change in the soft tissue parameters between T5-T4 time intervals.Conclusion:Soft tissue vertical relapse occurs in skeletally stabile Class III bimaxillary surgery patients in the first 3 years after surgery.     

Comparison of three different types of splints and templates for maxilla repositioning in bimaxillary orthognathic surgery: a randomized controlled trial

The selection and implementation of a plan for maxillary surgery is of the utmost importance in achieving the desired outcome for the patient undergoing two-jaw orthognathic surgery. Some splint-based and splintless methods, accompanied by computer-assisted techniques, are helpful in improving surgical plan implementation. However, randomized controlled trials focused on this procedure are lacking. This study included 61 patients who underwent bimaxillary surgeries. The patients were randomly assigned to a conventional resin occlusal splint (CROS) group, a digital occlusal splint (DOS) group, or a digital templates (DT) group, in a 1:1:1 ratio. The mean linear distance between the planned and actual postoperative positions of eight selected points on the surfaces of the maxillary teeth was selected as the outcome measure. The distance was significantly smaller in the DT group (1.17 ± 0.66 mm) when compared to both the CROS group (2.55 ± 0.95 mm, P < 0.05) and DOS group (2.15 ± 1.12 mm, P < 0.05). However, the difference between the CROS group and DOS group was not statistically significant. These findings indicate that using digital templates results in the best performance in transferring the surgical plan to the operation environment as compared to the other two types of splints. This suggests that the application of digital templates could provide a reliable treatment option.     

Differences in three-dimensional soft tissue changes after upper,lower, or both jaw orthognathic surgery in skeletal class III patients

The decision is not always straightforward as to which orthognathic procedure is best for a good aesthetic result; three-dimensional imaging has brought new insight into this topic. The aim of this prospective study was to verify objectively whether postoperative changes occur within those regions not directly affected by surgical movements of the underlying jaw bones. The study included 83 young adults with skeletal class III deformities. They were classified into three groups according to the type of surgery: bilateral sagittal split osteotomy set-back of the mandible (BSSO), Le Fort I advancement of the maxilla, or a combination of both. Pre- and postoperative optical scans were registered as regional best-fits on the areas of the foreheads and both orbits. The shell to shell differences were measured and the average distances between the observed regions were calculated. As expected, changes were greatest in the regions where the underlying bones had been moved, but regardless of the operation performed, changes were found over the whole face. Changes in the nose, cheek, and upper lip regions in the BSSO group and in the lower lip and chin region in the Le Fort I group confirmed the concept of the facial soft tissue mask acting as one unit.     

Novel methods for quantifying soft tissue changes after orthognathic surgery

Laser scanners are becoming increasingly important as a tool for quantifying the outcome of facial surgery. However, few computer algorithms have been developed for this purpose. Researchers have either measured the differences in the positions of (manually located) landmarks, or have taken radial measurements of the distances between surfaces. Neither of these techniques provides satisfactory information about the shape changes between surfaces. In this paper, alternative methods are proposed and their performance is compared with that of the radial method. Tests on two patients show that the Correspondences by Sensitivity to Movement (CSM) and closest point algorithms provide the most realistic measurements of the differences between two surfaces. The CSM method was found to be useful for pinpointing areas where the shape has changed.     

Effects of jaw movement in bimaxillary orthognathic surgery on the upper airway: Computational fluid dynamics analysis

Maxillomandibular repositioning in orthognathic surgeries has both morphologic and functional effects. These surgeries are thought to change the pharyngeal space and cause obstructive sleep apnoea syndrome, however. The primary purpose of this study is to evaluate the effects of jaw movement in bimaxillary orthognathic surgery on airway function and to identify the morphometric factors that can predict postoperative airway function. The subjects were 11 males and 12 females who had undergone orthognathic surgeries of the maxilla and mandible. The results of cephalometric analysis, cross-sectional area of the pharynx (CSA), pharyngeal volume and computational fluid dynamics (CFD) were compared. The CSA of the nasal (CSA1), total volume and total nasal volume decreased after surgery with statistical significance. Velocity at the oropharyngeal space (V2) increased after surgery with statistical significance. V2, CSA of the oropharyngeal space (CSA2) and PV were correlated with the horizontal posterior movement of point B, point Menton and overjet. V2 and CSA2 were correlated with SNB before and after surgery in all 46 analyses. Changes in pharyngeal airflow were more affected by pressure drop in the pharyngeal space (ΔPp) than by pressure drop in the nasal space (ΔPn). The relationship between the actual amount of change in the cephalometric reference point and the airway function is evident. CFD may thus be very useful as morphological analysis in preoperative treatment decision making.     

Predicting soft tissue changes after orthognathic surgery: The sparse partial least squares method

Objectives:To develop a prediction algorithm for soft tissue changes after orthognathic surgery that would result in accurate predictions (1) regardless of types or complexity of operations and (2) with a minimum number of input variables.Materials and Methods:The subjects consisted of 318 patients who had undergone the surgical correction of Class II or Class III malocclusions. Two multivariate methods—the partial least squares (PLS) and the sparse partial least squares (SPLS) methods—were used to construct prediction equations. While the PLS prediction model included 232 input variables, the SPLS method included a reduced number of variables generated by a handicapping algorithm via the sparsity control. The accuracy between the PLS and SPLS models was compared.Results:There were no significant differences in prediction accuracy depending on surgical movements, the sex of the subjects, or additional surgeries. The predictive performance with a reduced set of 34 input variables chosen using the SPLS method was statistically indistinguishable from the full set of variables with the original PLS prediction model.Conclusions:The prediction method proposed in the present study was accurate for a wide range of orthognathic surgeries. A reduced set of input variables could be selected through the SPLS method while simultaneously maintaining a prediction level that was as accurate as that of the original PLS prediction model.     

Assessing the outcome of orthognathic surgery by three-dimensional soft tissue analysis

Studies of orthognathic surgery often focus on pre-surgical versus post-surgical changes in facial shape. In contrast, this study provides an innovative comparison between post-surgical and control shape. Forty orthognathic surgery patients were included, who underwent three different types of surgical correction: Le Fort I maxillary advancement, bilateral sagittal split mandibular advancement, and bimaxillary advancement surgery. Control facial images were captured from volunteers from local communities in Glasgow, with patterns of age, sex, and ethnic background that matched those of the surgical patients. Facial models were fitted and Procrustes registration and principal components analysis used to allow quantitative analysis, including the comparison of group mean shape and mean asymmetry. The primary characteristic of the difference in shape was found to be residual mandibular prognathism in the group of female patients who underwent Le Fort I maxillary advancement. Individual cases were assessed against this type of shape difference, using a quantitative scale to aid clinical audit. Analysis of the combined surgical groups provided strong evidence that surgery reduces asymmetry in some parts of the face such as the upper lip region. No evidence was found that mean asymmetry in post-surgical patients is greater than that in controls.     

Three-dimensional analysis of nasolabial soft tissue changes after Le Fort I osteotomy: a systematic review of the literature

A systematic review was conducted to investigate the three-dimensional (3D) effect of Le Fort I osteotomy on the nasolabial soft tissues. The literature search was conducted using the MEDLINE (accessed via PubMed), Embase, and Cochrane electronic databases until January 2018. A total of 333 studies were identified (PubMed, n = 292; Embase, n = 41; Cochrane Library, n = 0). Seventeen met the inclusion criteria. The studies were essentially retrospective. The risk of bias was considered high in 15 studies, medium in one study, and low in one study. 3D soft tissue analysis was performed at least 6 months after surgery (mean 8.3 months). The main image acquisition technique reported was cone beam computed tomography (CBCT), associated or not with 3D photography. Approximately 50% of the studies performed two-jaw surgery, 25% performed maxillary surgery only, and the other 25% included heterogeneous intervention groups. The most reported nasolabial changes were anterior and lateral movements of the nasomaxillary soft tissues and upper lip, together with anterior and superior movement of the nasal tip. The alar cinch suture and V–Y closure technique seemed to have little effect in counteracting the undesirable postoperative nasolabial changes. CBCT superimposition presented a reliable 3D assessment for simultaneous measurement of skeletal and soft tissue changes.     

双颌畸形同期外科矫治术48例报道

目的:总结分析同期手术矫治双颌畸形的手术设计与效果。方法:对48例累及上、下颌骨的牙颌面畸形患者进行同期双颌手术。其中上颌后缩、下颌前突17例,同时伴有偏颌畸形5例;上颌前突、下颌后缩9例;双颌前突13例;腭裂术后上颌后缩2例;长面综合征2例。全部病例均按规范正颌手术诊治程序进行。手术设计依畸形类型而定,基本术式为:上颌骨行整体或分块的LeFortⅠ型骨切开术,同期行双侧下颌支矢状骨劈开术(SSRO)或垂直骨切开术(IVRO);上颌前部骨切开配合下颌前部根尖下骨切开术;部分病例配合颏成形术。结果:48例患者伤口一期愈合,无感染及骨段坏死,术中及术后并发症共7例,均得到及时处理,未影响最终结果。术后随访6～36个月显示,除2例复发外,其余病例外形及功能均达到术前预期效果。结论:随访结果显示,严格按照规范的诊治程序,采用外科与正畸相结合的方式,有针对性地设计并行双颌同期手术,有诸多优点,是取得功能与形态俱佳效果的最佳选择。     

A novel approach for planning orthognathic surgery: The integration of dental casts into three-dimensional printed mandibular models

A method of producing a composite model consisting of a three-dimensional printed mandible bearing plaster teeth is presented. Printed models were obtained from cone beam computed tomograms (CBCT) of dry human mandibles. The plaster casts of the teeth were obtained from impressions of the teeth of the dry mandibles. The distorted teeth of the printed models were removed and replaced by the plaster casts of the teeth using a simple transfer jig. The accuracy of the composite models obtained from six mandibles was assessed from laser scans. The scans of the dry mandibles and the composite models were superimposed and the magnitude of the discrepancies at six points on the dentition and six on the mandible were obtained. It was concluded that the errors of the method were small enough to be clinically significant. The use of the composite models is illustrated in two clinical cases.     

Analysis of soft tissue profile changes after mandibular advancement surgery

The aim of this study was to analyze changes in soft tissue profile after mandibular advancement surgery, with special emphasis on the effect of skeletal relapse and different Class II facial patterns. The cephalometric radiographs of 30 consecutive patients (24 women and 6 men, mean age 23 years) who underwent sagittal split osteotomy were studied. The radiographs were taken immediately before operation, at one week and 14 months postoperatively. To analyze the possible influence of hyper- and hypodivergent facial patterns, the patients were classified into low- (4 patients), medium- (16 patients) and high-angle (10 patients) groups according to the magnitude of the mandibulonasal plane angle. The main movement occurred in the horizontal plane. Soft tissue pogonion and mentolabial fold were found to follow the underlying skeletal structures in a nearly 1:1 ratio. On final follow-up, skeletal relapse of 1.3 mm was measured at B-point and of 1.5 mm at pogonion. Taking the skeletal relapses into account, the ratios of both corresponding soft tissue references (alternative ratios) dropped to 60%. Soft tissue pogonion is the most reliable reference for the planning of mandibular advancement. The ratio of soft tissue movement to final skeletal position at the chin amounts to 60% for a realistic prediction. However, the low-angle group differed from other groups by showing a markedly low soft-to-hard tissue ratio of only 14% at pogonion and a high ratio of 109% at the mentolabial fold. However, these differences in ratios between the groups were statistically not significant.     

正颌手术后咀嚼肌改变的研究进展

正颌手术通过打破原有的颌骨系统,重建咬合平衡来达到改善面型和咀嚼功能的目的。随着现代医学的发展和人们观念的进步,正颌外科被越来越多的患者所接受,其疗效和安全性也得到了学术界的肯定,但是也有少部分术后恢复不佳甚至治疗失败的病例存在。颌面部解剖结构复杂,影响预后的因素较多,尤其正颌术后颌面部软组织的变化难以动态观察,至今其变化过程及机制尚不明确。本文就近年来正颌术后咀嚼肌改变的研究进展作一综述。     

Accuracy of Le Fort I osteotomy in bimaxillary splint-based orthognathic surgery: focus on posterior maxillary movements

This retrospective study was performed to verify the accuracy of horizontal and vertical repositioning of the maxilla in bimaxillary osteotomy with a focus on posterior vertical displacement. Data from 39 orthognathic patients undergoing bimaxillary surgery including a one-piece Le Fort I osteotomy with pitch rotation and advancement at the University Hospitals of Leuven (Belgium), between January 2015 and April 2016, were included in the study. Preoperative and 1-week postoperative lateral cephalograms were digitized and imported into cephalometric software. Horizontal and vertical measurements of dental landmarks were used to assess the accuracy of maxillary repositioning, and errors were reported in terms of the mean and absolute mean. The horizontal advancements were randomly under- and over-corrected an average of 1.4 mm ± 1.2 mm. Vertical repositioning of the anterior maxilla followed the planning. A tendency for under-correction was found for posterior vertical intrusion of the maxilla. The same tendency towards under-correction of posterior maxillary inferior repositioning was detected when planned movements were greater than 3 mm. For all studied groups, no significant difference was found between the planning and the results achieved, validating the use of intermediate splints.     

Virtual surgical analysis: long-term cone beam computed tomography stability assessment of segmental bimaxillary surgery

The assessment of the stability of orthognathic surgery is often time-consuming, relies on manual re-identification of anatomical landmarks, and has been based on short-term follow-up. The purpose of this study was to propose and validate a semi-automated approach for three-dimensional (3D) assessment of the long-term stability of segmental bimaxillary surgery. The approach was developed and validated using cone beam computed tomography scans obtained at 2 weeks and 2 years postoperative. The stability of the surgical outcome was calculated as 3D translational and rotational differences between the short- and long-term postoperative positions of the individual bone segments. To evaluate reliability, intra-class correlation coefficients were calculated at a 95% confidence interval on measurements of two observers. Ten class II and III patients (six male, four female; mean age 24.4 years), who underwent a combined three-piece Le Fort I osteotomy, bilateral sagittal split osteotomy, and genioplasty, were included in the study. Intra- and inter-observer reliability were excellent (range 0.82–0.99). The range of the mean absolute difference of the intra- and inter-observer translational and rotational measurements were 0.14 mm (0.13)–0.44 mm (0.50) and 0.20° (0.16)–0.92° (0.78). The approach has excellent reliability for 3D assessment of long-term stability of segmental bimaxillary surgery.     

双颌手术后颜面软组织侧貌改变的研究

目的 研究下颌前突伴上颌骨发育不全患者术后颜面软组织侧貌改变.方法 对20例下颌前突伴上颌骨发育不足病例进行术前后Χ线头影测量研究,用SPSS软件对测量值进行统计分析.结果 下唇突点(LI点)、颏唇沟点(Si点)软组织颏前点(PG点)分别以下中切牙点(li点)下牙槽座点(B点)硬组织颏前点(pg点)的92%、97%、92%后移而后移,并得出了相应的回归方程.结论 上颌软硬组织改变无明显相关性,下颌软硬组织改变有非常显著相关性.     

上颌前突矫治术后软组织侧貌改变的研究

目的:分析上颌前份节段性骨切开矫治上颌前突术后软组织侧貌改变情况,探讨其稳定性。方法:对21例上颌前份节段性骨切开成年男性患者术前、术后1个月及术后1年的X线头影测量片进行对比研究。结果:术后软组织侧貌改变:上中切牙切缘点Is平均后移6.1±2.7m(mP<0.01),上唇突点Ls平均后移4.6±1.6m(mP<0.01),鼻唇角Cm-Sn-Ls平均增加6.8°±5.6(°P<0.01),上下唇间隙Stms-Stmi平均缩小4.5±3.5m(mP<0.01),露齿程度Is-Stms平均减小2.1±2.2m(mP<0.05),上唇突度减小,上唇厚度、长度及软组织面型角G-Sn-Pgss无显著改变(P<0.05)。术后1年颜面软组织侧貌改变的稳定性与术后早期相比,在水平方向上,所有指标复发率均超过10%。在垂直方向上各项指标复发率均在10%以内。结论:上颌前份节段性骨切开术矫正上颌前突,患者软组织侧貌的改善明显,效果稳定。