Three-Dimensional Soft Tissue Prediction Using Finite Elements Part II: Clinical Application

Background and Aim:   

The goal of this study was to analyze the validity and prediction accuracy of a newly-developed procedure for three-dimensional soft tissue prediction based on Finite Element Method, and to compare the results with prediction produced using an existing two-dimensional prediction program (Dentofacial Planner Plus).     

Photogrammetric assessment of the soft tissue profile in unilateral cleft lip and palate.

OBJECTIVE: To describe the soft tissue profile of children with unilateral cleft lip and palate from profile photographs and assess the reliability of this method. DESIGN: Retrospective analysis of prospectively collected data. SETTING: A national study in the United Kingdom. SUBJECTS: Caucasian children born in the United Kingdom between April 1, 1982, and March 31, 1984, and aged between 12 and 14 years at data collection. A cleft side and noncleft side profile photograph was available for each of 175 children. METHOD: Seven angular measurements were made using Dentofacial Planner Plus software, and the profile appearance was rated by an expert panel. RESULTS: Reliability for repeated measurement of the same photograph was acceptable for all but li-sm(s)-pg(s) (labiomental fold). Similar levels of reliability were found when comparing measurements from the cleft side and non-cleft side photograph. Logistic regression showed that the variables nst-sn-ls (nasolabial angle), ss(s)-n(s)-pg(s) (maxillary prominence), and g(s)-prn-pg(s) (facial convexity) were associated with the profile score. CONCLUSIONS: Soft tissue profile analysis from photographs is reliable and robust under a range of conditions. Soft tissue profile measurements are associated with panel ratings of profile.     

Cephalometric soft tissue profile in unilateral cleft lip and palate patients

Soft tissue profile analysis from cephalometric radiographs is recognized as an important part of the assessment of treatment outcome in cleft lip and palate (CLP), and has previously been found to discriminate between groups better than conventional hard tissue cephalometric analysis. Cephalometric radiographs of 182 12-14-year-old children from the UK with complete unilateral cleft lip and palate (UCLP) were available for this investigation, which aimed to describe the cephalometric soft tissue findings for this group of UK children. Seven soft tissue profile angular variables were measured using Dentofacial Planner Plus (DFP). Thirty films were re-measured two weeks later to assess the reliability of the method, which was acceptable for most of the variables, although use of landmarks related to the lips increased error. Mean nasolabial angle (97.44 degrees), facial convexity (138.02 degrees), and soft tissue ANB (2.99 degrees) compared unfavourably with previously reported data. These findings support the data given in the Clinical Standards Advisory Group study. Soft tissue profile assessment from cephalometric radiographs has acceptable reliability. The results of treatment show poor outcome in the UK compared with published data.     

Soft tissue profile changes after autogenous iliac crest onlay grafting for the extremely atrophic maxilla.

PURPOSE: The aim of this study was to evaluate profile changes in the hard and soft tissues after onlay grafting in the extremely atrophic maxilla. PATIENTS AND METHODS: Onlay grafting using autogenous iliac crest bone grafts was performed in 49 patients (42 females and 7 males) with extreme atrophy of the edentulous maxilla (vertical amount of bone: <6 mm, transverse amount of bone: <5 mm). For the assessment of the changes to the hard and soft tissues, the preoperative and postoperative cephalograms were traced and the cephalometric measuring points (44 skeletal and 25 soft tissue points) were digitalized with the aid of the Dentofacial Planner System. Evaluation of a relationship between soft tissue and hard tissue profile changes was performed by comparing the movement of the skeletal points Sub-ANS and A-point with the shift of the soft tissue point SLS. To determine significant hard tissue and soft tissue changes, the measured values were evaluated using the SPSS program system and examined for statistical significance by use of the Wilcoxon test. RESULTS: An advancement of the bony maxilla profile in the sagittal direction by an average of 2.4 mm (P < .01) was found. The soft tissue profile of the upper lip was moved forward on average by 2.3 mm (P = .0039) at the superior labial sulcus point and by 2.7 mm (P = .0018) at the labrale superius point. The ratio of the soft tissue change to hard tissue change was 0.7:1 (superior labial sulcus: skeletal point sub-ANS) or 0.9:1 (superior labial sulcus: A point). CONCLUSIONS: When planning onlay graft operations, consideration should be given to the functional and aesthetic effects of the profile changes on the upper lip.     

The predictability of maxillary repositioning in LeFort I orthognathic surgery.

Our ability to predict the outcome of any orthognathic procedure relies on the surgeon's ability to accurately reproduce the desired skeletal movements and on our understanding of the soft tissue changes associated with those movements. The purpose of this retrospective study was to evaluate the surgical accuracy of maxillary repositioning by comparing the objectives obtained from cephalometric prediction tracings with the actual skeletal changes achieved during maxillary and maxillomandibular procedures. The sample consisted of 46 patients from the files of 1 orthodontist. Presurgical and immediately postsurgical cephalometric radiographs were digitized, and the original surgical prediction was reproduced with Dentofacial Planner (Dentofacial Software, Toronto, Ontario, Canada) software. Vertical and horizontal measurements to several skeletal landmarks were used to assess the differences between the predicted maxillary position and the actual maxillary postsurgical position. Statistical differences were found for some measurements, particularly those related to the vertical placement of the posterior maxilla. Three variables were evaluated for their effect on the surgical discrepancies. The 2 surgeons with the most patients were evaluated and found to have differences in the direction of discrepancies but not the amount (absolute values). Significant differences were also found when evaluating surgical complexity (single-jaw vs bimaxillary procedures) and the direction of movement (impaction vs advancement) in direction only. To assess the overall fit of individual predictions, we calculated an average discrepancy for each patient; 80% of the actual results fell within 2 mm of the prediction, and 43% fell within 1 mm of the prediction.     

Three-Dimensional Soft Tissue Prediction Using Finite Elements

Abstract Background and Aim: The prediction of soft tissue esthetics is important for achieving an optimal esthetic outcome in orthodontic treatment planning. Applicable procedures have so far been restricted to two-dimensional profile predictions that have not proven to be very reliable. The goal of this investigation was therefore to develop a novel finite element-based procedure that allows a three-dimensional, easily visualized, quantitative analysis and prediction of soft tissue behavior for the clinician. The procedure to be developed should be easy to handle and not entail any additional radiation exposure for the patient. Material and Methods: Using a three-dimensional scanner, the facial surfaces of 20 probands were digitalized and individual FEM models were generated. Results: After reduction of data redundancy via several conversion steps, a patient-specific simulation model was prepared consisting of 20,000 to 40,000 individual elements to which specific physical properties could be assigned. The average time required for generating a virtual model was 50 minutes. Problems occurring during model generation were rare (mainly shadowing phenomena and movement artifacts). Conclusion: The procedure outlined herein makes the reliable generation of patient-specific simulation models possible for facial soft tissue prediction in orthodontics.     

Prediction of soft tissue profiles in orthodontic surgery with the Dentofacial Planner

Since the early 1990s, there have been continuous improvements in the software available for planning orthognathic surgery. This study investigates the precision of profile prediction by version 1.51 of the Dentofacial Planner (DFP). Orthognathic operations in 40 patients with different types of dysgnathia were evaluated. The preoperative and postoperative lateral cephalograms were analyzed in the DFP. The computer profiles were simulated on the basis of the skeletal alterations of the jaws observed postoperatively. The predicted soft tissue profiles were compared with the postoperative profile lines and evaluated statistically. The quality of the soft tissue prediction varied from one profile region to another. Significant differences were shown in various operation categories. Appreciable prediction errors were observed in the lip region. In particular, the upper lip revealed inadequate protrusion in bimaxillary operations. The smallest number of significant errors was found in single-jaw operations on the mandible. Significant features were not shown in the chin prediction profile, especially caudal to the superior labiomental furrow. The DFP version tested in the investigation shows some improvements in the convenience of the application compared to the previous versions. The profile prognosis is satisfactory, even in complicated bimaxillary operations. Results continue to be unsatisfactory in the lip profile prognosis. Further development of the software is necessary.     

应用有限元法预测正颌术后三维软组织形变的初步探讨

目的:基于锥形束CT(CBCT)资料建立有限元模型,预测正颌术后三维软组织形变,探讨该方法的可行性与准确性。方法:选取下颌前突患者2例,于术前行颅颌面CBCT扫描,导入Mimics10.01软件,进行软、硬组织三维重建。采用Geomagic Studio11软件进行模型处理,并按实际情况进行手术模拟截骨,导入有限元分析软件AnsysWorkbench 11.0,建立线弹性有限元模型,加载位移后,经分析得出术后软组织三维模样,将其与术后6个月及以上的软组织三维重建图像对比,并进行定性及定量评价。结果:2例患者CBCT资料顺利进行有限元建模及预测,临床定性评价显示2例患者预测结果总体观察相似度高,但在口周及颊部相似度欠佳;Geomagic Qualify11定量检测显示,病例1误差小于2mm的区域为94.98%,病例2误差小于2mm的区域为90.71%。结论:采用线弹性有限元模型预测下颌前突正颌术后的软组织形态是可行的,可为临床提供较为可靠的参考。     

三维摄影对蒙古族正常(牙合)成人面部软组织的侧貌分析

目的 应用三维测量的方法对面部软组织进行测量,研究正常(牙合)面部软组织的立体结果,建立正常(牙合)面部软组织的正常值,为错(牙合)畸形的诊断提供依据.方法 对144例受试者(蒙古族女性77例,男性70例)拍摄三维立体影像,并在软件上进行20个标志点的确定,23个角度、13个线距的测量,所得数据用SPSS 22.O统计...     

Computers and the orthodontist

Dentofacial Planner Plus (DFP) is a computerised cephalometric program that enables rapid and accurate analysis of a cephalogram to aid in treatment planning. In addition, a video image of a patient's profile can be linked to the digitised cephalogram. Manipulation of the tracing will produce corresponding changes in the video image. Simulations of orthodontic treatment or orthognathic surgery changes are therefore possible. This becomes a valuable aid in treatment planning, communication with the oral surgeon and patient education.     

Three-Dimensional Soft Tissue Prediction Using Finite Elements Part I: Implementation of a New Procedure

Background and Aim:   

The prediction of soft tissue esthetics is important for achieving an optimal esthetic outcome in orthodontic treatment planning. Applicable procedures have so far been restricted to two-dimensional profile predictions that have not proven to be very reliable. The goal of this investigation was therefore to develop a novel finite element-based procedure that allows a three-dimensional, easily visualized, quantitative analysis and prediction of soft tissue behavior for the clinician. The procedure to be developed should be easy to handle and not entail any additional radiation exposure for the patient.     

Computer-assisted three-dimensional surgical planing and simulation. 3D soft tissue planning and prediction

The purpose of this paper is to report a new technique for three-dimensional facial soft-tissue-change prediction after simulated orthognathic surgical planning. A scheme for soft tissue deformation, "Computer-assisted three-dimensional virtual reality soft tissue planning and prediction for orthognathic surgery (CASP)", is presented. The surgical planning was based on three-dimensional reconstructed CT visualization. Soft tissue changes were predicted by two newly devised algorithms: Surface Normal-based Model Deformation Algorithm and Ray Projection-based Model Deformation Algorithm. A three-dimensional color facial texture-mapping technique was also used for generating the color photo-realistic facial model. As a final result, a predicted and simulated patient's color facial model can be visualized from arbitrary viewing points.     

Soft tissue profile changes after maxillary advancement with distraction osteogenesis by use of a rigid external distraction device: a 1-year follow-up.

PURPOSE: This study was conducted to evaluate the soft tissue profile changes after maxillary advancement with distraction osteogenesis (DO). PATIENTS AND METHODS: Sixteen subjects underwent maxillary advancement with rigid external distraction after a high Le Fort I osteotomy. There were 11 male and 5 female patients, ages 5.2 to 25.7 years. The subjects included 9 with unilateral cleft lip and palate (UCLP), 4 with bilateral CLP, 2 with facial clefts and bilateral CLP, and 1 with cleft palate. Pretreatment and posttreatment lateral cephalograms were compared to evaluate the changes in soft tissue profile. A line 7 degrees below the SN plane was used as the horizontal coordinate, and a perpendicular line through Sella was used as the vertical coordinate in an XY coordinate system. RESULTS: The preoperative facial concavity (N'SnPg') was reduced by 15.59 degrees, and the nasal tip moved 3.75 mm forward and 2.05 mm upward. These changes were positively correlated with the change of ANS position. The soft-tissue-to-hard-tissue ratio was 0.53:1 for nasal tip and ANS. The ratio was negatively correlated with the age of the patient. The ratio of soft tissue A point to skeletal A point was 0.96:1 and for the incisal edge to vermilion border of the upper lip it was 0.8:1. The soft tissue B point and Pg did not change significantly with maxillary distraction. However, the nasolabial angle increased by 4.96 degrees, the upper lip curvature flattened by 0.65 mm, and the lower lip curvature was accentuated by 0.89 mm after distraction. The amount of upper incisal exposure increased from 1.1 to 5.01 mm in the rest position. CONCLUSION: Maxillary DO improved the soft tissue profile by increasing nasal projection, normalizing the nasolabial angle, and making the upper lip more prominent. More upper anterior tooth show in the rest position was obtained, but the upper lip length did not change. The concave facial profile became convex, with improved facial balance and aesthetics.     

Stability of the hard and soft tissue profile after mandibular advancement in sagittal split osteotomies: a longitudinal and long-term follow-up study

The aim of the study was to conduct a long-term follow-up investigation of the stability of hard and soft tissues after bilateral sagittal split osteotomy (BSSO) with rigid internal (RIF) fixation to advance the mandible. Sixteen consecutive patients (12 females and 4 males, mean age 21.4 years) were available for re-examination 12.7 years (T5) after surgery. The preceding follow-ups were before (T1), and 5 days (T2), 7.3 months (T3), and 13.9 months (T4) after surgery. Lateral cephalograms were traced by hand, digitized, and evaluated with the Dentofacial Planner program. The x-axis for the system of co-ordinates ran through sella (point zero) and the line NSL -7 degrees. Thus, the program determined the x- and y-values of each variable and the usual angles and distances. Statistical analysis was carried out using Wilcoxon's matched-pair signed-ranks test with Bonferroni adjustments. The relationships between the examined variables were analysed by Spearman rank correlation coefficients. The backward relapse at point B (T5) was 2.42 mm, or 50 per cent, and at pogonion 3.21 mm, or 60 per cent of the initial advancement. The mean net effect at T5 on the labial fold (soft tissue point B) was 94 per cent of the advancement at point B. For the soft tissue chin (soft tissue pogonion), it was 119 per cent of the advancement at pogonion. The net effect on the lower lip (labrale inferior) was 55 per cent of the advancement at incision inferior. The amount of the surgical advancement of the mandible was correlated with the long-term relapse in point B. Among possible reasons for this relapse are the initial soft tissue profile, the initial growth direction, and the remodelling processes of the hard tissue.     

面部软组织三维重建及测量系统的研制与应用

目的 研究和开发可应用于正畸临床诊断的数字化三维重建和测量系统,进行颌面部软组织结构的三维测量研究。方法 应用4个高精度的数码相机获取颌面部软组织的三维信息,自行研制和开发出应用于面部重建和测量的数字化立体摄影测量硬件系统,在专业计算机立体显示卡上开发面部软组织三维重建和测量软件系统,同时完成面部软组织三维测量分析和旋转观察。结果 应用研制的面部软组织三维重建和测量硬件及软件系统,可以重建出具有真实感的三维图像并在计算机中任意旋转、移动、缩放;面部软组织三维立体测量精度,左侧数码相机对为0．483mm,右侧数码相机为0．419mm。结论 本项研究所建立的面部软组织三维重建和测量系统,具有精度高、速度快、非介入性等特点,为口腔正畸学面部软组织三维结构的诊断、分析提供了一条新途径。     

软组织侧貌预测系统的建立和研究

目的：结合临床实际,建立一个正畸治疗中软组织侧貌改变的乔治预测系统。并对系统进行实用性的可行性论证。方法：自主开发侧貌预测软件HOPS-400,以所建系统对24例安氏Ⅱ类1分类错He功能矫治的软组织头影量预测结果和治疗结果进行对比分析。比较二者的一致程度。结果：在95%可信限内,3种软组织头影测量分析方法（Burstone,Holdway,Bishara)中的30项指标有19项一致。尤其是9项角度测量指标有7项一致;18项线距测量结果有10项一致;3项线距比指标也有2项一致。结论：预测结果对临床有一定的指导作用。     

新疆维吾尔族美貌女性侧貌软组织形态角度测量分析

目的：建立新疆维吾尔族美貌女性侧貌软组织角度参考值并分析角度与侧貌特征的关系,为口腔颌面相关学科医生提供临床参考数据。方法：按标准选取31名新疆维吾尔族美貌女性,在自然头位摄取其侧面数码照片,在计算机上用photoshopCS软件选择13个软组织标志点,测量15个角度值,应用SPSSl3．0统计软件包对数据进行处理,使用Dahlberg’s公式计算测量方法误差。结果：新疆维吾尔族美貌女性侧貌软组织角度测量值范围。方法误差显示了测量方法的可靠性和可重复性。结论：所测角度在侧貌软组织特征分析中具有重要作用,“美学三角”可以作为侧貌美学分析的参考平面,“种族金字塔”中的3个角度可用于分析种族的差异性。     

北京地区正常(牙合)面部软组织不对称性的三维测量研究

目的应用数字化立体摄影测量系统进行正常(牙合)面部软组织不对称性的三维测量,获得面部软组织在三维方向上的不对称向量.方法选择40例正常(牙合)成人进行面部软组织不对称性的三维测量,计算面部软组织在三维方向上的不对称向量.结果男性组和女性组都是右侧面部较大,但男女无显著性差异;面部不对称量都是在x轴上分布最多;面部越靠面下部的点和越靠外侧面的点,其不对称量越大.结论用三维摄影测量的分析方法显示面部中下部的不对称性更为明显;三维立体摄影测量是较好的研究面部软组织不对称性的方法.     

正常人群面部软组织三维测量与X线头影测量的相关性分析

目的　比较正常的面部软组织三维测量与X线头影测量结果。方法　应用面部软组织数字化立体摄影测量与X线头影测量对标准正常进行面部软组织三维测量,并进行相关性分析。结果　面部软组织三维测量项目与对应的X线头影测量项目具备相关性。结论　面部软组织三维测量结果能够部分的反映其下硬组织的情况。