The accuracy of video imaging in orthognathic surgery

Accuracy of Manual and Virtual Predictive Tracings in Patients Submitted to Orthognathic Surgery

Cephalometric tracing done manually was considered gold standard for the cephalometric analysis in the last decades. The digital radiographs began to be commonly used in order to make that in a digital way. The objective was to define the accuracy of the predictive and final cephalometric tracings performed manually and virtually. The authors selected 20 patients submitted to bimaxillary orthognathic surgery. The data were collected from lateral cephalometric radiographs, in the preoperative and postoperative periods. The interest were: points, angles (Sella-Nasion to A point angle; Sella-Nasion to B point angle; Frankfurt plane to Mandibular plane angle; Frankfurt plane to occlusal plane angle; Upper and lower central incisors long axes angle; Incisor to Mandibular plane angle; Upper incisor axis to Sella-Nasion plane angle) distances (Co-A; Co-Gn). Data were submitted to the Shapiro-Wilk, analysis of variance, and Kruskal-Wallis tests. The measurement differences were compared using a t test. Descriptive statistics were performed in Excel 2013 and SPSS software, P <0.05 being considered significant. No statistically significant difference was found between the mean values predictive and postoperative of the angles and distances within the manual and digital groups. When comparing the means of the differences between the predictive values and the final values, only the 1:1 angle presented a statistically significant difference, indicating a greater accuracy of the digital predictive tracing for this measure. In conclusion, both methods for obtaining predictive tracings are accurate, which shows that clinical results can be successfully simulated by the most accessible technique.

Prediction accuracy of Dolphin software for soft-tissue profile in Class I patients undergoing fixed orthodontic treatment

BACKGROUND

Simulation and prediction can facilitate the decision between an extraction versus nonextraction treatment plan. This study aimed to assess the accuracy of Dolphin Imaging software in predicting profile changes in class I borderline cases.

METHODS

In this retrospective study, class I borderline patients (i.e., both extraction and nonextraction treatment plans were possible for them) aged 15-35 years were enrolled. All of the cephalometric analyses were done by Dolphin Imaging software, version 11.8 Premium. The initial cephalograms were superimposed on initial photographs. The final values for the 7 angular and linear landmarks of the upper and lower incisors were extracted from post-treatment cephalograms and inserted in the "Goals" tab of the Dolphin Imaging software. Post-treatment images of patients were simulated. Final post-treatment photographs were superimposed on the simulated pictures. The differences between the real and simulated pictures were calculated in relation to the reference lines. The P value was set at 0.05.

RESULTS

A total of 70 patients (36 with tooth extraction, and 34 without tooth extraction) were included. In the extraction group, the horizontal position of both lips was predicted to be significantly more protruded than it actually was, whereas in the nonextraction group, the only difference between the simulated and actual results was that the vertical position of the lower lip, which was simulated as being more inferior than it actually was.

CONCLUSIONS

Despite the statistically significant differences between the real and simulated pictures, the differences were small and clinically insignificant. Prediction via Dolphin Imaging software can be an appropriate guide in extraction-nonextraction borderline cases.

[Surgery First : prediction for skeletal objectives through structural analysis. Comparison of Sassouni and Delaire analysis]

INTRODUCTION

The purpose of this study was to compare two structural cephalometric analysis (Delaire and Sassouni) as surgical decision tools. These two analyses do not include dental compensation for skeletal discrepancies and have been proven reliable especially for the Sendai surgery first protocol developed by Sugawara.

MATERIAL AND METHOD

The two analysis were performed on 20 surgical cases and the proposed skeletal modifications were compared in order to measure the differences and see if those differences varied according to the facial type. For 10 cases the Virtual Surgical Planning (VSP) images obtained from Dolphin 11.95 Premium software (based on the presurgical CBCT and facial photographs) allowed a comparison of the two analyses as surgical decision indicators and to the realised surgical procedure. The VSP photographs obtained were graded by two panels: one professional and the other one non professional.

RESULTS

Sassouni's analysis favored more forward movements for the maxilla (ENA +5,45) as well as more vertical modifications (Me 1,595). The facial type did not appear to have a significant effect. The quality of Dolphin VSP prediction was judged rather reliable above average (3.7/6) by the panels. The VSP photographs obtained from the two analyses were presented to the panels as well as the VSP obtained from the actual surgery. The three facial outcomes: Sassouni, Delaire and "Surgery Realised" called Dolphin showed some potentially interesting differences. The small size of the sample did not show any significant findings (t test) but a special analysis revealed a valid difference between the three outcomes. The most aesthetic being Dolphin (surgery realised) 17.4 then Sassouni 16.6 (diff 0.8) and finally Delaire 14 (diff 2.6).

CONCLUSIONS

The two structural analysis Delaire and Sassouni did not give the same surgical objectives. Sassouni favored more forward movements for the maxilla as well as more vertical modifications. The Dolphin software appeared to be the quite reliable software to predict the facial outcomes of the surgery. The VSP photographs obtained using Sassouni's analysis were more balanced than when the Delaire analysis was followed (16.4/14 = +2.6). The VSP based on the actual surgery was judged to be even more aesthetic. This shows that beyond a cephalometric analysis the facial aesthetic details and the functional analysis are very important during the phase of surgical planning.

Comparison of the Accuracy of Manual and Digital Cephalometric Prediction Methods in Orthognathic Surgical Planning: A Pilot Study

Objective

To compare and evaluate the reliability of manual and digital cephalometric prediction methods in orthognathic surgical planning.

Methods

Ten adults (5 females and 5 males) with skeletal class III malocclusion were included. The mean patient age was 21.97 years. Pre- to postoperative changes were evaluated using paired t-test. Manual surgical predictions made by tracing on acetate paper and digital predictions made using computer software were compared with actual postoperative values using intraclass correlation coefficient and root mean square.

Results

Statistically significant changes were observed in SNA, SNB, ANB, U1i-FH, and Nperp-A following bimaxillary orthognathic surgery (p<0.001). Postoperative changes in Co-A and Nperp-Pg were statistically significant (p<0.05). Comparison of manual and digital surgical predictions with actual postoperative values revealed that overbite and overjet showed the lowest agreements. Manual predictions were less accurate for points that were difficult to distinguish (Co and U6). Skeletal predictions were more accurate than dental predictions.

Conclusion

Parameters with low reproducibility (Co and U6) decrease the reliability of predictions. Dental predictions were inaccurate in both methods due to the effects of intermaxillary elastics, but both methods yielded similar predictions for skeletal parameters. The impact of applying strong elastics for postoperative intermaxillary fixation should be considered when making surgical predictions.

Improvement of facial profile by nonextraction orthodontic treatment with temporary skeletal anchorage devices and visual treatment objectives

A 15-year-old girl with a convex profile and a retrognathic chin was referred for improvement of her profile. Nonextraction orthodontic therapy with temporary skeletal anchorage devices was used to improve her facial balance in a total active treatment time of 26 months. Her occlusion and profile were significantly improved by the treatment. Posttreatment records after 12 months showed excellent results with good occlusion and facial harmony.

Orthodontic Treatment of the Patient with Complete Clefts of Lip, Alveolus, and Palate: Lessons of the past 60 Years

This review paper summarizes 60 years of progress in the orthodontic care of patients with complete clefts of the lip, alveolus, and palate. The progress and evolution of orthodontic treatment for patients with complete clefts has taken a slow and sometimes circuitous route to present-day standards. Nonetheless, in spite of this history of slow and inefficient scientific and clinical progress, review of the literature of the past 60 years does, in fact, reveal that progress has been made. This progress has not only been in the area of improved surgical and orthodontic techniques but also relative to the scientific weaknesses of past decades. The investigations of more recent years seem to be moving in a direction of better documentation, stricter methodologies, longer-term follow-up, larger sample sizes, etc. However, there remains much work to be done. Only by adopting a more critical approach will protocols be defined that can achieve optimal outcomes, while minimizing the burden of the orthodontic treatment through elimination of superfluous intervention.

Morphologic outcome of bimaxillary surgery--an anthropometric appraisal

OBJECTIVES

To adequately perform orthognathic surgery procedures, it is from basic interest to understand the morphologic changes caused by orthognathic surgery. Anthropometric analyses of standardized frontal view and profile photographs could help to investigate and understand such changes.

STUDY DESIGN

We present a pre- to postoperative evaluation of orthognathic surgery results based on anthropometric indices described by Farkas and cephalometric measurements. 30 Class III patients undergoing maxillary advancement by Le Fort I Osteotomy and mandibular setback by bilateral sagittal split osteotomy were evaluated. Preoperative as well as three and nine months postoperative lateral cephalograms as well as standardized frontal view and profile photographs were taken. On the photographs 21 anthropometric indices given by Farkas were evaluated. In cephalograms SNA and SNB angle as well as Wits appraisal were investigated.

RESULTS

The investigated anthropometric indices showed a significant increase of the vertical height of the upper lip without changing the relation of the upper vermilion to the cutaneous upper lip. The lower vermilion height increased relatively to the cutaneous lower lip without vertical changes in the lower lip. Due to maxillary advancement the upper face height increased meanwhile the lower face height decreased due to mandibular setback. SNA and SNB angle and Wits appraisal showed typical changes related to surgery.

CONCLUSIONS

The investigated photo-assisted anthropometric measurements presented reproducible results related to bimaxillary surgery.

Evaluation of the soft tissue treatment simulation module of a computerized cephalometric program

Objective:

The purpose of this study is to compare the accuracy of the treatment simulation module of Quick Ceph Studio (QCS) program to the actual treatment results in Class II Division 1 patients.

Design:

Retrospective study.

Materials and Methods:

Twenty-six skeletal Class II patients treated with functional appliances were included. T0 and T1 lateral cephalograms were digitized using QCS. Before applying treatment simulation to the digitized cephalograms, the actual T0-T1 difference was calculated for the SNA, SNB, ANB angles, maxillary incisor inclination, and protrusion and mandibular incisor inclination and protrusion values. Next, using the treatment simulation module, the aforementioned values for the T0 cephalograms were manually entered to match the actual T1 values taking into account the T0-T1 differences. Paired sample t-test were applied to determine the difference between actual and treatment simulation measurements.

Results:

No significant differences were found for the anteroposterior location of the landmarks. Upper lip, soft tissue A point, soft tissue pogonion, and soft tissue B point measurements showed statistically significant difference between actual and treatment simulation in the vertical plane.

Conclusion:

Quick Ceph program was reliable in terms of reflecting the sagittal changes that would probably occur with treatment and growth. However, vertical positions of the upper lip, soft tissue pogonion, soft tissue A point, and soft tissue B point were statistically different from actual results.

Achieving the prediction results by visualized treatment objective following anterior maxillary segmental osteotomy. A retrospective study

This study used the manual visualized treatment objectives (VTO) as a tool to evaluate the predictive value of the computer-assisted VTO. Presurgical cephalometric tracing predictions generated by oral and maxillofacial surgeons and computer-assisted VTOs were compared with the postsurgical outcome as seen on lateral cephalometric tracings. Ten measurements of the predicted and actual postsurgical hard tissue landmarks were compared statistically. A paired Student's t test showed that in nine of ten measurements, there were no statistically significant differences in the mean values of manual VTO (MVTO). Statistically significant differences were found in one of the four linear measurements (cant of upper lip P - 0.0001). For computer assisted (CAVTO) Student's t test showed that in nine of ten measurements, there were no statistically significant differences in the mean values. Statistically significant differences were found in one of the four linear measurements (nasolabial angle, P  - 0.0001). From these data, it appears that both VTOs demonstrated good predictive comparative outcome, and are equally predictive, but CAVTO is precise.

Long-term skeletal and profile stability after surgical-orthodontic treatment of Class II and Class III malocclusion

OBJECTIVE

The purpose of this perspective research was to study the long-term stability of skeletal, dentoalveolar and soft tissue after orthognathic surgery in subjects presenting with Class II and Class III malocclusions.

METHODS

The available digitized cephalometric radiographs, including pretreatment (t0), presurgery (t1), a minimum of 12 months postsurgery (t2) and at least 3 years after the orthosurgery treatment (t3) were taken between 1998 and 2010. In Group 1 mandibular advancement and in Group 2 mandibular advancement and maxillary impaction surgery were performed for correction of Class II. In Group 3 maxillary advancement and in Group 4 surgical maxillary advancement with mandibular setback, for correction of Class III.

RESULTS

In all the phases mandibular length was shorter in Group 1, and the inferior third of the face was longer in Group 2. Before the surgery there was greater maxillary deficiency in Group 3 than Group 4 and mandibular length was longer in Group 4.

CONCLUSION

In Groups 1 and 2, at retention phase, relapse occurred due to the increase in mandibular plane, whereas the surgeries performed in Groups 3 and 4 remained stable.

Soft tissue outcome after mandibular advancement--an anthropometric evaluation of 171 consecutive patients

OBJECTIVES

There is an ongoing discussion in the literature about preoperative planning and postoperative evaluation of orthognathic surgery and its impact on facial appearance and aesthetics.

MATERIALS AND METHODS

We present an anthropometric and cephalometric evaluation of orthognathic surgery results based on reference anthropometric data. In 171 Class II patients, mandibular advancement by bilateral sagittal split osteotomy was performed. Preoperative as well as 3 and 9 months postoperative standardized frontal view and profile photographs and lateral cephalograms were evaluated in a standardized manner by use of 21 anthropometric indices. In cephalograms, SNA and SNB angle as well as Wits appraisal were investigated. Results of anthropometric and cephalometric measurements were correlated.

RESULTS

Lower vermilion contour, vermilion and cutaneous total lower lip height, nose-lower face height, nose-face height, upper face-face height, upper lip- and chin-mandible height index showed significant pre- to postoperative changes as well as SNB angle and Wits appraisal. Furthermore, medial-lateral cutaneous upper lip height, vermilion and cutaneous total lower lip height and philtrum-mouth width index presented significant correlations to cephalometric measurements.

CONCLUSIONS

The investigated anthropometric indices and cephalometric measurements presented reproducible results related to surgery. The correlation of cephalometric to anthropometric measurements has been proven useful for preoperative planning and postoperative evaluation of orthognathic surgery patients.

CLINICAL RELEVANCE

The presented anthropometric measurements and their observed correlation to cephalometric measurements could lead to a better prediction and optimized planning of the soft tissue result in orthognathic surgery patients and thereby improve the aesthetic outcome.

Factors influencing the accuracy of cephalometric prediction of soft tissue profile changes following orthognathic surgery

The cephalometric prediction of orthognathic treatment outcome is an important part of the surgical planning and the process of informed consent. The orthodontic and surgical changes must be described accurately prior to treatment in order to assess the treatment's feasibility, to optimize case management and to increase patient's understanding and acceptance of the recommended treatment. The aim of the present article was to investigate on the factors that could influence the accuracy of cephalometric prediction in planning orthognathic surgery. Review of the literature revealed that, besides factors directly related to the prediction method and its use, there exist a considerable number of factors which could affect significantly the accuracy of soft tissue response. These factors could be biological ones such as relapse, centre of mandibular rotation and individual variation in response to treatment and others such as gender, race, pre-operative soft tissue thickness and data bases for mean ratios of soft to hard tissue movement changes. Some of the factors affecting the accuracy of prediction of soft tissue response following orthognathic surgery are inevitable and there are others, difficult to control and predict. However, patients should be informed that predictions are only a guide, may not represent the actual result of the surgical outcome, and as such they should be implemented.

Reliability of computerized cephalometric outcome predictions of mandibular set-back surgery

INTRODUCTION

A successful treatment outcome in dentofacial deformity patients commonly requires combined orthodontic-surgical therapy. This enables us to overcome functional, aesthetic and psychological problems. Since most patients state aesthetics as the primary motive for seeking therapy, cephalometric predictions of treatment outcome have become the essential part of treatment planning, especially in combined orthodontic-surgical cases.

OBJECTIVE

The aim of this study was to evaluate the validity and reliability of computerized orthognathic surgery outcome predictions generated using the Nemotec Dental Studio NX 2005 software.

METHODS

The sample of the study consisted of 31 patients diagnosed with mandibular prognathism who were surgically treated at the Hospital for Maxillofacial Surgery in Belgrade. Investigation was done on lateral cephalograms made before and after surgical treatment. Cephalograms were digitized and analyzed using computer software. According to measurements made on superimposed pre- and postsurgical cephalograms, the patients were retreated within the software and the predictions were assessed by measuring seven angular and three linear parameters. Prediction measurements were then compared with the actual outcome.

RESULTS

Results showed statistically significant changes between posttreatment and predicted values for parameters referring to lower lip and mentolabial sulcus position.

CONCLUSION

Computerized cephalometric predictions for hard-tissue structures in the sagittal and vertical planes, as well as the VTO parameters, generated using the Nemotec Dental Studio NX 2005 software are reliable, while lower lip and mentolabial sulcus position predictions are not reliable enough.

Finite element modelling of maxillofacial surgery and facial expressions--a preliminary study

BACKGROUND

Recent advances in diagnostic imaging and associated software have enabled the transformation of anatomical structures into finite element (FE) models facilitating computerized facial modelling. The work presented employs personalized imaging data of facial anatomical structures for use in planning and predicting the outcome of maxillofacial surgery. The current process relies on either freehand planning and/or commercial two-dimensional (2D) and three-dimensional (3D) surgical planning software packages, but the validity of these software packages has been questioned. In this paper, the finite element technique was used to predict the outcome of maxillofacial surgery.

METHODS

A finite element facial model was created, based on patient specific bone and skin image data, combined with generic muscle data. The model was used for two distinct purposes: simulation of the maxillofacial surgery and simulation of facial expressions pre- and post-surgery. This combination allowed for an improved prediction of surgery outcome. Commercial software was used for creating the FE facial model from the original image data, and LS-DYNA(®) was the analysis code used for the purpose of the FE simulation.

RESULTS

The results from the simulation of maxillofacial surgery showed an overall agreement of 85% with the patient data at 6 months post-surgery and the error was generally contained within a ± 2 mm threshold.

CONCLUSIONS

The results show that the approach of using commercial FE software tools to create a detailed and anatomically accurate patient specific model for simulation of maxillofacial surgery, as well as facial expressions, can be applied in facial surgery planning. As the study was based on data collected from one patient, further work is needed in which additional subjects can be assessed.

Comparative study of 2 software programs for predicting profile changes in Class III patients having double-jaw orthognathic surgery

INTRODUCTION

Computer software can be used to predict orthognathic surgery outcomes. The aim of this study was to subjectively compare the soft-tissue surgical simulations of 2 software programs.

METHODS

Standard profile pictures were taken of 10 patients with a Class III malocclusion and a concave facial profile who were scheduled for double-jaw orthognathic surgery. The patients had horizontal maxillary deficiency or horizontal mandibular excess. Two software programs (Dentofacial Planner Plus [Dentofacial Software, Toronto, Ontario, Canada] and Dolphin Imaging [version 9.0, Dolphin Imaging Software, Canoga Park, Calif]) were used to predict the postsurgical profiles. The predictive images were compared with the actual final photographs. One hundred one orthodontists, oral-maxillofacial surgeons, and general dentists evaluated the images and were asked whether they would use either software program to plan treatment for, or to educate, their patients.

RESULTS

Statistical analyses showed differences between the groups when each point was judged. Dolphin Imaging software had better prediction of nasal tip, chin, and submandibular area. Dentofacial Planner Plus software was better in predicting nasolabial angle, and upper and lower lips. The total profile comparison showed no statistical difference between the softwares.

CONCLUSIONS

The 2 types of software are similar for obtaining 2-dimensional predictive profile images of patients with Class III malocclusion treated with orthognathic surgery.

Evaluation of the linearity of soft- to hard-tissue movement after orthognathic surgery

INTRODUCTION

Our aim in this study was to investigate whether a linear relationship exists between soft- to hard-tissue changes for both maxillary and mandibular landmarks over a wide range of skeletal changes.

METHODS

The sample consisted of 30 Chinese patients with Class III malocclusion treated with bilateral sagittal split osteotomy and LeFort I advancement. Lateral cephalograms were taken within 2 months before surgery and at least 6 months after surgery. Soft- and hard-tissue changes were recorded by computer-supported measurements of presurgical and postsurgical lateral cephalograms. To evaluate the linear association between soft- and hard-tissue movement, a quadratic function of hard-tissue movement adjusted for sex was initially fitted to the data. The residual plots were used to examine the appropriateness of the fitted quadratic function, and the lack of fit was examined by the F test. A linear function was fitted to the data when the quadratic term was not significant.

RESULTS

Visual inspection of the scatter plots of the 5 pairs of corresponding soft- and hard-tissue landmarks showed that relationships between the soft and hard tissues were reasonably linear for both male and female subjects, except for the Sn-ANS pair that showed a curvilinear relationship. Statistical tests confirmed that the association for the Sn-ANS pair was quadratic.

CONCLUSIONS

The results of this study provide evidence of a linear relationship between soft- to hard-tissue changes for mandibular landmarks over a wide range of skeletal changes. The nonlinear response of maxillary soft tissues to underlying hard-tissue change in the Sn-ANS pair supports the use of nonlinear ratios for selected maxillary soft- to hard-tissue movements in simulation software.

The validity of a computer-assisted simulation system for orthognathic surgery (CASSOS) for planning the surgical correction of class III skeletal deformities: single-jaw versus bimaxillary surgery

The aim of this study was to assess the accuracy of the two-dimensional profile prediction produced by the computer-assisted simulation system for orthognathic surgery (CASSOS), for the correction of class III facial deformities. Correction was by maxillary advancement (n=17) or bimaxillary surgery (n=16). The mean age was 24 years (range 18-42). The surgical and dental movements obtained from the postoperative cephalogram were used to produce a CASSOS profile prediction, which was compared with the soft-tissue profile. The prediction was superimposed onto the postoperative radiograph, and a coordinate system was used to measure linear differences. For the maxillary advancement group there were statistical differences for three horizontal landmarks: superior labial sulcus (p=0.017), labrale superious (p=0.038) and labiomental fold (p=0.014). In the bimaxillary group only the landmark vertical labrale superious (p=0.002) showed a statistical difference. Generally, CASSOS produced useful profile predictions for maxillary advancement surgery or bimaxillary surgery for Class III patients, although there was considerable individual variation. The main areas of inaccuracy were the lips. The major difference between the two types of surgery was that most of the errors in the maxillary surgery group were in the horizontal direction, whilst for the bimaxillary surgery the errors were mainly in the vertical direction.

J, Medeiros PJD, Almeida MADO. Simulação computadorizada do perfil facial em cirurgia ortognática: precisão cefalométrica e avaliação por ortodontistas

OBJETIVO: verificar a precisão de um programa de simulação computadorizada na predição de alterações no perfil facial em diferentes tipos de cirurgia ortognática. METODOLOGIA: utilizou-se radiografias e fotografias de perfil das fases pré-cirúrgica e final de 32 pacientes. As movimentações esqueléticas do procedimento cirúrgico foram reproduzidas no traçado pré-cirúrgico, gerando mudanças no perfil mole, originando o traçado e a imagem predictiva de perfil. Analisou-se o perfil da amostra total e dividida em dois grupos, sem cirurgias no sentido vertical (AP) e com cirurgias de impacção ou reposicionamento inferior da maxila (V). Comparou-se cefalometricamente pontos do perfil mole dos traçados predictivo e final. As imagens predictivas computadorizadas foram comparadas com as imagens finais por 20 ortodontistas, que avaliaram cinco regiões: perfil total, nariz, lábio superior, lábio inferior e mento. RESULTADOS E CONCLUSÕES: observou-se variabilidade de posicionamento dos pontos do perfil, com mais de 60% dos erros até 2mm e 17% acima de 3mm. Diferenças significativas entre os pontos foram mais freqüentes no sentido vertical. Os ângulos nasolabial e mentolabial predictivos apresentaram-se mais agudos que os finais. As notas médias encontradas na análise subjetiva variaram de 56 para o lábio inferior a 75,42 para o nariz. As imagens predictivas não apresentaram diferenças significativas de qualidade entre os grupos. Em comparação com outros sistemas de simulação computadorizada, este programa pode ser considerado útil na prática clínica ortodôntica e cirúrgica. Entretanto, diante de algumas limitações observadas, recomenda-se cautela no planejamento e apresentação do caso, considerando que algumas predições podem exigir melhorias com ferramentas de ajuste.

Mathematical Modeling and Numerical Simulation in Maxillofacial Virtual Surgery

Computer-based surgery simulation is a rapidly emerging and increasingly important area of research that combines a number of disciplines for the common purpose of improving healthcare. The objective of this article is to provide a virtual surgery tool for accurately planning the aesthetic impact of hard and soft tissue movements in dentoskeletal malocclusions. The approach proposed here allows direct interaction with a completely three-dimensional (3D) computed tomography (CT) model of a solid, highly detailed structure of the head to obtain a realistic prediction of soft tissue behavior. We studied 25 patients who had facial malformations pre- and postoperatively with 3D hard and soft tissue CT studies, and maxillary or mandibular osteotomies were simulated. The postoperative 3D CT and facial outcomes were compared with the simulations. In 80% of the cases studied, the simulation-predicted changes, when compared with the clinical outcomes, were within the tolerance level (2 mm) established by maxillofacial surgeons.

The accuracy of computer-assisted surgical planning in soft tissue prediction following orthognathic surgery

BACKGROUND

The purpose of the present study was to evaluate the accuracy of a computer-assisted imaging system in predicting the soft tissue response following orthognathic surgery.

METHODS

The study sample consisted of 11 adult patients with a mean age of 23.5 years. The preoperative and postoperative lateral cephalograms were obtained after orthodontic preparation and immediately before surgery and at least 1 year after surgery. The computer-generated soft tissue image and the actual surgical outcome were compared to evaluate the accuracy of the imaging system.

RESULTS

In the sagittal plane, the tip of nose was the most accurate site and the largest difference was shown in the upper lip. The lower lip was noted to be the least accurate and the subnasale the most accurate region in the vertical plane. Predictions were found to be more accurate for the sagittal plane when compared with those for the vertical plane.

CONCLUSIONS

Computer-assisted visual treatment objectives was proved to be satisfactory in predicting the soft tissue outcome following orthognathic surgery.

Mathematical Modeling and Numerical Simulation in Maxillo-Facial Virtual Surgery (VISU)

Computer-based surgery simulation is a rapidly emerging and increasingly important area of research that combines a number of disciplines for the common purpose of improving healthcare. The objective of this paper is to provide a virtual surgery (VISU) tool for accurately planning the aesthetic impact of hard and soft tissue movements in dento-skeletal malocclusions. The approach proposed here allows direct interaction with a completely three-dimensional (3-D) computed tomography (CT) model of a solid, highly detailed structure of the head to obtain a realistic prediction of soft tissue behavior. We studied 25 patients who had facial malformations pre- and postoperatively with 3-D hard and soft tissue CT studies, and maxillary or mandibular osteotomies were simulated. The postoperative 3-D CT and facial outcomes were compared with the simulations. In 80% of the cases studied, the simulation-predicted changes, when compared with the clinical outcomes, were within the tolerance level (2 mm) established by maxillo-facial surgeons.

Prediction Accuracy of Computer-Assisted Surgical Visual Treatment Objectives as Compared With Conventional Visual Treatment Objectives

PURPOSE

This present study used the conventional visualized treatment objectives (VTOs) as a tool to evaluate the predictive value of the Dolphin computer-assisted VTOs.

MATERIALS AND METHODS

Presurgical cephalometric tracing predictions generated by oral and maxillofacial surgeons and the Dolphin Imaging software were compared with the postsurgical outcome as seen on lateral cephalometric tracings. Sixteen measurements of the predicted and actual postsurgical hard tissue landmarks were compared statistically.

RESULTS

A paired Student's t test showed that 7 measurements had statistically significant differences for the conventional VTOs (facial angle, P < .0001; AOC, P < .0001; SNB, P = .003; ANB, P = .004; U1-NA-degrees, P = .01; U1-NA-mm, P = .02; and N perp Pog, P < .0001), while 9 measurements were statistically significant ( P = <.0001) for Dolphin (facial angle, P = .0001; AOC, P = .005; SNB, P = .001; ANB, I = .04; U1-NA-degrees, P = .003; PogNB, P = .04; U1-NA-mm, P = .002; N perp Pog, P = .0001; UFH, P = .03; and LFH, P = .03).

CONCLUSION

From these data, it appears that both VTOs demonstrated good predictive comparative outcome and are equally precise.

Predictability of soft tissue profile changes following bimaxillary surgery in skeletal class III Chinese patients

PURPOSE

The aim of this study was to evaluate the accuracy of soft tissue profile predictions generated by a recently developed computer program (Computer-Assisted Simulation System for Orthognathic Surgery [CASSOS] 2001, SoftEnable Technology, Ltd, Hong Kong) in Chinese skeletal Class III patients treated with bimaxillary surgery.

MATERIALS AND METHODS

Presurgical and posttreatment lateral cephalograms of 35 Chinese patients who had combined 1-piece Le Fort I and bilateral sagittal split osteotomies were digitized using the CASSOS 2001 program, and a cranial base superimposition was performed. The hard tissue movements were simulated on the presurgical cephalogram until good superimposition of the hard tissues on the presurgical and posttreatment cephalograms was achieved. A customized cephalometric analysis consisting of 32 linear measurements was used to analyze the differences in the soft tissue profile between the actual posttreatment results and the computer-generated predictions.

RESULTS

Comparison of the predicted and actual changes found that 16 of the 32 soft tissue measurements were significantly different ( P <.05). Most of the significant prediction errors were observed in the upper and lower lip region. The software tended to underestimate the vertical position of both the upper and lower lip and overestimate the horizontal position of the lower lip. However, the mean differences were relatively small, with the greatest mean difference being 2 mm in the vertical position of stomium inferius. The CASSOS 2001 program produced a clinically useful prediction of soft tissue profile changes following bimaxillary surgery in skeletal Class III Chinese patients.

A comparison of current prediction imaging programs

To investigate perceived differences in the ability of current software to simulate the actual outcome of orthognathic surgery, we chose 10 difficult test cases with vertical discrepancies and "retreated" them using the actual surgical changes. Five programs--Dentofacial Planner Plus, Dolphin Imaging, Orthoplan, Quick Ceph Image, and Vistadent--were evaluated, by using both the default result and a refined result created with each program's enhancement tools. Three panels (orthodontists, oral-maxillofacial surgeons, and laypersons) judged the default images and the retouched simulations by ranking the simulations in side-by-side comparisons and by rating each simulation relative to the actual outcome on a 6-point scale. For the default and retouched images, Dentofacial Planner Plus was judged the best default simulation 79% and 59% of the time, respectively, and its default images received the best (lowest) mean score (2.46) on the 6-point scale. It also scored best (2.26) when the retouched images were compared, but the scores for Dolphin Imaging (2.83) and Quick Ceph (3.03) improved. Retouching had little impact on the scores for the other programs. Although the results show differences in simulation ability, selecting a software package depends on many factors. Performance and ease of use, cost, compatibility, and other features such as image and practice management tools are all important considerations. Users concerned with operating system compatibility and practice management integration might want to consider Dolphin Imaging and Quick Ceph, the programs comprising the second tier.

The accuracy of video imaging prediction in soft tissue outcome after bimaxillary orthognathic surgery

PURPOSE

The purpose of the present study was to evaluate the accuracy of the outcome in soft tissue prediction through use of a computer imaging system after bimaxillary orthognathic surgery.

MATERIALS AND METHODS

The study sample consisted of 30 adults who had undergone orthognathic surgery that included the Wassmund and Köle procedures and optional genioplasty to correct bimaxillary protrusion. All the patients had lateral cephalometric radiographs and profile photographs taken within 6 months before surgery and at least 6 months after surgery. The computer-generated soft tissue image and the actual postsurgical profile were compared. The accuracy of this computer-generated profile image was evaluated.

RESULTS

The results indicated that the nasal tip, soft tissue A point, and upper lip presented the least predicted errors in sagittal plane. While the nasal tip presented higher reliability. Lower lip prediction was found to be the least accurate region and it tended to be located anterior to the actual position. In the vertical plane, most of the predictions revealed higher accuracy than those in the sagittal plane. There were no statistically significant differences between the predictions of the groups with and those without genioplasty.

CONCLUSIONS

Computer-generated image prediction was suitable for patient education and communication. However, efforts are still needed to improve the accuracy and reliability of the prediction program and to include the consideration of changes in soft tissue tension and muscle strain. The accuracy of this system in soft tissue prediction should be carefully interpreted.

Predicting lower lip and chin response to mandibular advancement and genioplasty

The purposes of this retrospective study were to examine the multidimensional nature of soft tissue changes associated with mandibular advancement and genioplasty and to develop predictive models. Longitudinal lateral cephalograms of 62 nongrowing patients (27 men and 35 women) were taken in centric relation with the lips in repose within 4 weeks before surgery and at least 6 months postoperatively (median postsurgical duration was 11 months). The mandibular incisor and pogonion were advanced surgically approximately 6 mm and 11 mm, respectively. The lower lip lengthened slightly (2.5 +/- 3.8 mm), and its surface contour straightened because of thinning at labrale inferior (-2.8 +/- 2.0 mm); there was a slight thickening at the labiomental fold (1.0 +/- 2.3 mm) and a slight thinning at soft tissue pogonion (-0.8 +/- 2.2 mm). Multiple regression models (explaining from 80% to 94% and 66% to 82% of the variation for horizontal and vertical movements, respectively) showed that soft tissue response to advancement surgery depended on pretreatment tissue thickness, horizontal skeletal movement, vertical skeletal movement, and the position of the maxillary incisors. Similar amounts of variation were explained when the models were applied to an independent validation sample of 15 subjects. It was concluded that lower lip and chin response to mandibular advancement and genioplasty is multifactorial but can be accurately and reliably predicted.

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.

Introduction of a three-dimensional anthropometry of the viscerocranium. Part II: evaluating osseous and soft tissue changes following orthognathic surgery

BACKGROUND AND OBJECTIVE

Anthropometric measurements, described and assessed in Part I of this article were applied in dysgnathic patients. Diagnosis, surgical planning and follow-up were performed and soft tissue ratios quantified.

MATERIAL AND METHODS

One hundred and seventy-five anthropometric measurements and 146 cephalograms of 100 patients were included. Forty-five patients were analysed before and after surgery. Ten randomly selected patients were re-measured directly by two investigators for reliability and validity assessment.

RESULTS

Manoeuvres that expanded the facial skeleton such as maxillary or mandibular advancements or maxillary elongations generally had a greater soft tissue impact than setbacks or maxillary impactions. A 1.4% intra-observer and a 2.6% inter-observer error was apparent with anthropometry. Concordance of anthropometry with roentgenocephalometry (p<0.04) was found by paired t -test.

CONCLUSION

The anthropometry allowed reliable and objective, independent calculation of cranial bone relations and soft tissue projection. It is also sensitive to facial asymmetry. Easy application, versatility and an economic price for the assessment of facial proportions, soft tissue ratios, operation planning and follow-up were obvious.

Soft tissue profile changes following mandibular advancement surgery: predictability and long-term outcome

The objectives of this cephalometric study were to assess long-term changes in the soft tissue profile following mandibular advancement surgery and to investigate the relationship between soft tissue and hard tissue movements. The sample consisted of 61 patients treated consecutively for mandibular retrognathism with orthodontic therapy combined with bilateral sagittal split osteotomy and rigid fixation. Lateral cephalograms were taken on 6 occasions: immediately before surgery, immediately after surgery, 2 and 6 months after surgery, and 1 and 3 years after surgery. Postsurgical changes in the upper and the lower lips and the mentolabial fold were more pronounced among low-angle cases compared with high-angle cases. In accordance with other studies, the soft tissue chin and the mentolabial fold were generally found to follow their underlying skeletal structures in a 1:1 ratio. Because of the strong influence skeletal relapse has on soft tissue profile changes, alternative ratios of soft tissue-to-hard tissue movement that accounted for mean relapse were also generated. It is suggested that if a more realistic long-term prediction of the postsurgical soft tissue profile is desirable, then ratios incorporating mean relapse should be used rather than estimates based on a 1:1 relationship.

Accuracy of video imaging for predicting the soft tissue profile after mandibular set-back surgery

The purpose of this study was to compare the accuracy of two video-imaging programs for predicting the soft tissue outcomes of mandibular set-back surgery for patients with skeletal class III malocclusion. The sample consisted of 30 previously treated, nongrowing, white patients who had undergone isolated mandibular set-back surgery. An objective comparison was made of each program's cephalometric prediction using a customized analysis, as well as a subjective comparison of the predicted images as evaluated by a panel of six raters. The results showed that both programs produced similar cephalometric and video image predictions. The cephalometric visual treatment objective predictions were found to be most accurate in the horizontal plane; approximately 30% of cases showed errors greater than 2.0 mm, whereas in the vertical plane, the error rate was greater (50%). The resulting video image predictions were judged by the panel as being in the "fair" category. A particular problem was noted when significant vertical compression of the soft tissue images was required. Video imaging was suitable for patient education but not accurate enough for detailed diagnosis and treatment planning.

Presurgical profile preferences of patients and clinicians

The purpose of this study was to compare the presurgical preferences for profile change of patients seeking orthognathic surgery with the preferences of "significant others" and clinicians. In this study, five features of lateral profile images of 11 patients scheduled for orthognathic surgery limited to the mandible (ie, set-back or advancement) were animated for continuous change with the use of customized morphing software and video imaging. Each patient profile was evaluated by the patient, a significant other, three orthodontists, and three oral surgeons. As the feature animated between two extremes, the zone of acceptability was established by depressing the computer mouse when the changing feature became acceptable and releasing the button when the image was no longer acceptable. In a separate task, the participants were asked to indicate the most pleasing position. An analysis of variance was used to find a significant difference (P <.017) in the zone of acceptability for all five profile features among all groups of evaluators. From smallest to largest, the order of the mean zone of acceptability was: orthognathic patient < oral surgeon < significant other < orthodontist. No consistent differences were found, however, for either the midpoint of acceptability or most pleasing distortion among the patients, significant others, and professional groups. In conclusion, it was demonstrated that (1) patients having orthognathic surgery were able to use this new video imaging method to communicate to clinicians what they find acceptable; and (2) although all groups had similar preferences, orthognathic patients had the lowest tolerance for deviation from the preferred image.

Evaluation of video imaging prediction in combined maxillary and mandibular orthognathic surgery

The purpose of this study was to evaluate the accuracy of the soft tissue profile "line drawings" predicted by Quick Ceph Image in combined maxillary and mandibular orthognathic surgical procedures. Preoperative (mean = 27.7 days presurgical) and posttreatment (mean = 11.5 months postsurgical) lateral cephalograms of 40 white patients (10 males and 30 females) who had completed treatment that involved orthodontics, one-piece LeFort I osteotomy, and mandibular advancement by bilateral sagittal split osteotomy with or without genioplasty were used in the study. Forty-five lateral hard and soft tissue landmarks were digitized, using the "on-screen" digitizing option, for each cephalogram and for each computer predicted posttreatment tracing. A customized analysis consisting of 24 linear and 4 angular measurements was used to analyze the differences between the actual posttreatment cephalometric landmark measurements and computer predicted landmark measurements. Statistically significant differences between the posttreatment cephalometric soft tissue profiles and the computer predicted soft tissue profiles were analyzed for the total sample, patients grouped according to: magnitude and direction of maxillary movements, adjunctive genioplasty procedure, V-Y closure of the LeFort I incision, and gender and age differences. The results indicated that for some of the soft tissue landmarks, differences were found between the posttreatment and the computer predicted profiles. Differences between the predicted and actual posttreatment soft tissue profiles may be attributed to the inaccuracy of Quick Ceph Image's default soft to hard tissue ratios when predicting the soft tissue response to combined maxillary and mandibular orthognathic surgical procedures.