Dissertations / Theses on the topic 'Mandibular prognathism'

Orientador: Fausto Berzin
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: Objetivos: Avaliar os sinais e sintomas das disfunções temporomandibulares, a dor crônica, a depressão, assim como também avaliar a função muscular dos masseteres e do temporal na mastigação habitual. Todas estas variáveis foram analisadas pré e após cinco anos da cirurgia ortognática. Materiais: Foi utilizado o questionário RDC (reseach diagnostic Criteria), para avaliar e classificar o tipo de disfunção temporomandibular (DTM), assim como para observar o grau de dor crônica e depressão (eixo II), para a análise dos sinais e sintomas das DTMs foi utilizado o eixo I do RDC. Na análise do ciclo mastigatório foi utilizado o eletromiógráfo Myosystem I e software Myosystem BRI, versão 2.52 (DataHominis Tecnologia Ltda). Os músculos avaliados foram a parte anterior do temporal e a parte superficial do masseter de ambos os lados. O comportamento muscular foi avaliado em cinco períodos: pré-cirurgia 2-3 meses (T0); Pós-cirurgia 6 meses (T1), 12 meses (T2), 24 meses (T3) e 60 meses (T4). Resultados: A dor crônica e a depressão apresentaram melhoras após 5 anos do tratamento cirúrgico. Em relação às outras variáveis analisadas, observamos, que após 12, 24 e 60 meses da cirurgia, existe um aumento do tempo e do instante máximo da atividade do ciclo mastigatório. O RMS apresenta o sinal eletromiográfico mais estável após cinco anos do tratamento cirúrgico. Conclusão: A cirurgia ortognatica não é tratamento para as disfunções temporomandibulares. O ciclo mastigatório mostra melhoras no sinal eletromiográfico para pacientes prognatas que não apresentem nenhum tipo de disfunção temporo mandibular
Abstract: Objectives : To evaluate the signs and symptoms of temporomandibular disorders , chronic pain , depression , as well as evaluate the muscle function of the masseter and temporal in mastication . All these variables were analyzed before and five years after orthognathic surgery. Materials : RDC ( reseach diagnostic Criteria) questionnaire was used to assess and classify the type of temporomandibular disorders ( TMD ) , as well as to observe the degree of chronic pain and depression ( axis II ) , for the analysis of the signs and symptoms of the TMD axis I RDC was used . In the analysis of the masticatory cycle Myosystem I electromyography and software Myosystem BRI , version 2.52 ( DataHominis Technology Ltd. ) was used . The muscles tested were the anterior part of the temporal and superficial part of the masseter muscle on both sides . Muscle performance was evaluated in five periods : pre - surgery 2-3 months ( T0 ), 6 months post- surgery ( T1 ) , 12 months ( T2 ) , 24 months ( T3 ) and 60 months ( T4 ) . Results: Chronic pain and depression showed improvement after 5 years of surgical treatment . Regarding the other variables , we observe that 12 , 24 and 60 months after surgery , there is an increase in the time and the maximum moment of the masticatory cycle activity. The RMS has the most stable EMG signal after five years of surgical treatment Conclusion : orthognathic surgery is no treatment for temporomandibular disorders . The masticatory cycle shows improvement in electromyographic signal for prognathic patients without any type of temporomandibular disorders
Doutorado
Anatomia
Doutora em Biologia Buco-Dental

Orientador: Valfrido Antônio Pereira Filho, Márcio de Moraes
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: A configuração e as dimensões da via aérea superior são determinadas pelas estruturas anatômicas como: tecidos moles, musculatura e esqueleto craniofacial, que compõem ou circundam a faringe. As alterações anatômicas dos tecidos moles e/ou do esqueleto craniofacial poderão tornar a via aérea superior (VAS) mais estreita. Estes pontos são os principais fatores etiológicos de um distúrbio cada vez mais diagnosticado na população brasileira conhecida como síndrome da apnéia e hipoapnéia obstrutiva do sono (SAHOS). A cirurgia ortognática, que é utilizada na correção das deformidades dento-esqueléticas, tem se mostrado como o tratamento mais eficiente nos casos graves de SAHOS. Boa parte dos pacientes portadores da síndrome apresenta deformidade dento-esquelética. A síndrome é mais comum nos pacientes portadores de deformidade do tipo classe II. Pacientes com deformidade dento-esquelética de classe III resultante do prognatismo mandibular e/ou deficiência maxilar apresentam uma diminuição da VAS após a cirurgia ortognática de recuo mandibular, embora seja menos tratada na literatura, não deixando claras as consequências dos recuos mandibulares isolados, bem como das cirurgias combinadas de avanço maxilar e recuo mandibular na via aérea superior a longo prazo. Em vista dos fatos apresentados, o presente estudo teve como objetivo avaliar as alterações da via aérea superior em pacientes com deformidade dento-esquelética classe III submetidos à cirurgia ortognática e se há diferença na resposta da via aérea superior quando comparados os gêneros. Para tanto, foi realizada uma avaliação cefalométrica de 45 pacientes divididos em três grupos: grupo 1- cirurgia bimaxilar (23 pacientes); grupo 2- cirurgia de avanço maxilar (15 pacientes) e grupo 3- cirurgia de recuo mandibular (7 pacientes). Desses 45 pacientes, 25 são do gênero masculino e 20 do gênero feminino. A via aérea superior foi avaliada utilizando a análise cefalométrica de Arnett-Gunson FAB-Surgery e o software Dolphin Imaging 11 (Dolphing Imaging and Management Solutions, Chatsworth CA, EUA) em 3 períodos distintos: T0 - pré-operatório; T1 - pós-operatório de 1 semana e T2 - pós-operatório de no mínimo 1 ano. Nos pacientes submetidos à cirurgia bimaxilar houve alteração da VAS no pós-operatório imediato, porém, a longo prazo, a medida da orofaringe voltou ao valor pré-operatório. No grupo 2 existiu um aumento da VAS que se manteve por longo tempo. Nos pacientes submetidos ao recuo mandibular não houve alterações da VAS. Quando se comparou a VAS entre os gêneros, observou-se que tanto os homens quanto as mulheres apresentaram alteração na região da nasofaringe, porém só as mulheres apresentaram uma alteração significativa na aérea da orofaringe. Como conclusão foi possível afirmar que: nos pacientes submetidos à cirurgia bimaxilar o avanço maxilar compensou as alterações na VAS acarretadas pelo recuo mandibular; os pacientes submetidos à cirurgia de recuo mandibular não apresentaram mudanças na VAS; o grupo submetido ao avanço maxilar apresentou um ganho significativo da VAS que se manteve estável pelo período avaliado e que as mulheres registraram alterações na região da nasofaringe e orofaringe, enquanto os homens somente na região da nasofaringe.
Abstract: The configuration and dimensions of the upper airway are determined by the anatomical structures such as soft tissue, muscles and craniofacial skeleton, which comprise or surround the pharynx. Anatomic abnormalities of the soft tissue and/or the craniofacial skeleton may narrow the upper airway leading to obstructive sleep apnea. Class III patients, after orthognathic surgery frequently show a decrease in upper airway which has been less evaluated in the literature. These points are the main factors influencing a disorder increasingly being diagnoses in our population known as obstructive sleep apnea. Orthognathic surgery that is used in the correction of dento-skeletal deformities has been shown to be the most effective treatment in severe cases of obstructive sleep apnea. Many of the patients with the syndrome have dento-skeletal deformities in various degrees. The syndrome is more common in patients with class II deformity. However patients with class III deformity resulting from mandibular prognathism and/or maxillary deficiency after a mandibular setback orthognathic surgery showed a decrease in upper airway which has been less evaluated in the literature. The influence of not making clear the influenced of isolated mandibular setbacks and bimaxillary surgery on the upper airway lacks long-term evaluation. This study aimed to evaluate the changes of upper airway dimensions in patients with class III dento-skeletal deformity treated with orthognathic surgery and the difference in the response of the upper airway between genders. A cephalometric evaluation of 45 patients was performed. The subjects were divided into three groups: group 1 - bimaxillary surgery (23 patients), group 2 - maxillary advancement surgery (15 patients) and group 3 - mandibular setback surgery (7 patients). Of these 45 patients 25 were males and 20 females. The upper airway was evaluated through the cephalometric analysis of Arnett-Gunson FAB-Surgery and the software Dolphin Imaging 11 (Dolphing Imaging and Management Solutions, Chatsworth CA, EUA) in three distinct periods: T0 - preoperative, T1 - one week postoperative and T2 - at least one year postoperative. In patients undergoing bimaxillary surgery we observed changes in the upper airway in the immediate postoperative period, but long-term measures the oropharynx returned to preoperative values. In maxillary advancement there was an increase in the upper airway that remained long-term. In patients who underwent mandibular setback no changes in the upper airway was observed. When comparing the upper airway between the genders we found that both men and women showed abnormalities in the nasopharynx, but only women showed a significant change in the oropharynx area. As conclusion, it was possible to state that: in patients who underwent bimaxillary surgery the jaw advancement compensated the changes of the upper airway brought about by the mandibular setback, the patients who received mandibular setback surgery showed no changes in the upper airway, and the group submitted to maxillary advancement showed a significant increase of the upper airway and that remained stable for the evaluation period. Women had abnormalities in the nasopharynx and oropharynx while men presented abnormalities only in the nasopharynx.
Mestrado
Cirurgia e Traumatologia Buco-Maxilo-Faciais
Mestre em Clínica Odontológica

碩士
高雄醫學大學
牙醫學研究所
89
Mandibular prognathism is characterized by excessive mandibular growth, which may compromise the masticatory function and facial appearance, and this may distort the personality of the patient. Surgical correction of mandibular prognathism will generally improve both the masticatory function and dentofacial aesthetics. This study was undertaken to examine the factors that might be responsible for skeletal stability occurring during one to two years postoperative mandibular setback. Forty-four patients, treated for absolute mandibular prognathism by modified intraoral bilateral vertical ramus osteotomy, were evaluated cephalometrically at least 1-year postoperatively. A set of 7 standardized lateral cephalograms were obtained from each subject, i.e., preoperative (T1) and immediately postoperative (T2), prior to removing the maxillomandibular fixation (T3), 3 months (T4), 6 months (T5), 1-year (T6) and 2-years postoperative (T7). There were 20 patients who underwent a 2-year follow-up with cephalograms. The mean setback of the menton was 12.3mm in the horizontal direction and 0.8mm downward in the vertical direction. Relapse was defined as forward movement of the menton during the 2-year postoperative period. The average movement for 1-year follow-up (12 of 20 patients) in the horizontal direction was as follows; 4 with 2.1mm (16% = 2.1/13.1) in forward movement and 8 with 1.6mm (12.4% = 1.6/12.9) in backward movement. The average movement during the 1-year follow-up (12 of 20 patients) in the vertical direction was 7 patients with 1.5mm in upward movement and 8 with 0.7mm in downward movement. The average movement during the 2-year follow-up (20 patients) in the horizontal direction was as follows; 14 with 2mm (16.3% = 2/12.3) in forward movement and 5 with 1.4mm (12.1% = 1.4/11.6) in backward movement. The average movement during the 2-year follow-up (20 patients) in the vertical direction was as follows; 11 patients with 1.7mm in upward movement and 8 with 1.2mm in downward movement. The variables included vertical and horizontal Me (T21) distance, Rp-Cut (distance between osteotomy point and the most posterior point of inferior ramus)(T1), and area of the pterygomasseteric sling (Rp-Cut-H ×V-T1) The multiple regression showed that the vertical amount of setback (T21) that predicated the vertical relapse (T72) was significant, whereas no significant correlations were noted between the variables and horizontal relapse (T72). In patients whose distal segments were still in the backward group 2-years postoperaviely, their osteotomy positions were anterior to the forward group. This tell us: the more anterior osteotomy position the more acceptable capacity of the pterygomasseteric sling will be created and this allow the distal segment to setback more without distend the pterygomasseteric sling. These results suggest that this technique can provide greater acceptable capacity for larger amount of distal segment setback and is feasible for the correction of severe mandibular prognathism. Key Words: Postoperative Stability, Mandibular Prognathism Modified Intraoral Vertical Ramus Osteotomy

碩士
國立臺灣大學
臨床牙醫學研究所
96
Purpose The purpose of this retrospective study was to compare post-operative changes and skeletal stability between bilateral saggital split ramus osteotomy (BSSO) and intraoral vertical ramus osteotomy (IVRO) used for mandibular setback. Factors contributing to skeletal instability were also identified. Patients and Methods The study included 48 patients with mandibular prognathism, who underwent mandibular setback surgery at the Department of Oral and Maxillo-facial Surgery, National Taiwan University Hospital (NTUH) from January 2001 to December 2006. Twenty-five of them recieved with rigid internal fixation, the remaining 23 underwent IVRO with intermaxillary fixation. Lateral cephalometric radiographs were taken within 1 month before surgery (T1), immediately after the operation (within 1 week, T2), and at the time of completion of post-op orthodontic treatment (T3). The T1,T2, and T3 radiographs were traced and superimposed with “best-fit” technique and the data were digitalized to analyze the changes at T2-T1 and T3-T2. Mann-Whitney test was used to verify the differences in post-operative changes and long-term skeletal stability between the two groups. And the linear regression model was established to find the contributing factors. Results The mean amount of horizontal setback at pogonion was 6.55 mm in BSSO group and 9.68 mm in IVRO group. The mean amount of vertical movement at menton was 0.99 mm upward in BSSO group and 0.12 mm downward in IVRO group. Long-term observation (T3-T2) showed that the chin moved upward (1.10 mm) and forward (1.48 mm) after BSSO, and moved downward (0.32 mm) and backward (1.19 mm) after IVRO. Significant differences were noted between the two procedures in horizontal skeletal instability at pogonion (T3-T2, p=.002), and vertical skeletal instability at menton (T3-T2, p=.004). In BSSO group, the horizontal soft/hard tissue ratio was 1.06 at B point, 0.88 at pogonion, 1.04 at menton. And the vertical soft/hard tissue ratio was 0.97 at B point, 1.00 at pogonion, 0.57 at menton. In IVRO group, the horizontal soft/hard tissue ratio was 1.03 at B point, 0.88 at pogonion, 1.01 at menton. And the vertical soft/hard tissue ratio was 0.91 at B point, 1.00 at pogonion, 2.07 at menton. No significant difference was found in the soft/hard tissue ratio. In BSSO group, the significant predictor for the horizontal skeletal instability was age and rotation of condylar axis. For vertical skeletal instability, it was significantly correlated to change of mandibular plane angle. In IVRO group, the significant predictors for horizontal skeletal instability were gender, openbite, and jaw deviation. And vertical skeletal instability was significantly correlated to age, amount of horizontal setback, grade of openbite, and follow-up period. Discussion The patterns of post-operative instability are significantly different between BSSO and IVRO. The key factors contributing to this difference was considered be the change in condylar axis and the application of RIF or IMF. In BSSO, the tooth-bearing segment was rigidly fixed with the bilateral condylar segments. Therefore, the chin moves upward and forward as the condylar axis rotates counter-clockwise post-operatively. But in IVRO, osseous remodeling takes place at the osteotomy site. The chin may not move while the condylar axis rotates counter-clockwise post-operatively. Moreover, the application of IMF will lead to an increase of lower facial height. Thus, the chin moves downward and backward after the surgery.

Uma das questões centrais da ortodontia moderna é: como as descobertas na área da genética afetarão diretamente conceitos e abordagens no tratamento ortodôntico e de que forma os fatores genómicos e epigenéticos podem ser manipulados e introduzidos no tratamento individual de cada paciente. O objetivo deste trabalho é demonstrar a importância da genética na previsão do crescimento mandibular. Esta dissertação é de índole teórica, estando desta forma isenta de qualquer tipo de trabalho prático experimental. Trata-se de uma revisão sistemática de trabalhos que estudaram o tema. A ortodontia baseada no genoma usa a informação genética para melhorar o diagnóstico e tratamento de distúrbios dentários e deformidades dentofaciais. Nos últimos 20 anos houve uma convergência de princípios e conceitos entre a genética e a ortodontia que levará a um avanço significativo dos tratamentos ortodonticos, contudo a sua aplicação prática não será imediata.
The central question in orthodontics in this millennium is: how discoveries in the field of genetics will directly affect concepts and approaches in orthodontic treatment and how genomic and epigenetic factors can be manipulated and introduced into the individual treatment of each patient. The aim of this study is to demonstrate the importance of genetics in the prediction of mandibular growth. This dissertation is of a theoretical nature, being thus exempt of any type of practical experimental work. This is a systematic review of papers that have studied the theme. Genome based orthodontics uses genetic information to improve the diagnosis and treatment of dental disorders and dentofacial deformities. In the last 20 years there has been a convergence of principles and concepts between genetics and orthodontics that will lead to a significant advance in orthodontic treatments, however, its practical application will not be immediate.

碩士
高雄醫學大學
牙醫學研究所
86
Chin cup therapy has been commonly used and widely recognized as a method for correcting malocclusion in the growing prognatic mandible. For the last 20 years, a number of clinical and experimental studies have reported that Chin cup force has several orthopedic effects: (1)redirection of mandible growth; (2)retardation of mandible growth; (3)remodelling of mandible morphology. 　　The purpose of this study was to investigate the bone morphology change or bone remodelling process in ClassⅢ malocclusion subsequent to Chin cup therapy with finite element method analysis. The finite element method analysis has several characters that can overcome some conceptual and technical constraints of customary roentgenographic cephalometric methods. FEM provide invariant descriptions of growth kinematics that are independent of their underlying, causally related, dynamics. Since FEM utilized the principles of continnum mechanics, it (i) describes the kinematics of nodal point growth behavior of any given element mesh and, (ii) provide a field result with interpolation techniques which can not be accomplished with traditiomal approach. The two attributes above suggest that FEM provides quantitative descriptions of both the functional metrices and the skeletal units enclosed within the boundaries of a given finite element mesh. 　　The subjects in this study consisted of 25 growing girls who showed anterior crossbite and Angle Class Ⅲ malocclusion before treatment. All underwent chin cup therapy from, the beginning of treatment. The duration of chin cup therapy varied but average 1.8 years. Eighteen cephalometric points on the mandible were digitized on preteatment and posttreatment lateral cephalograms of patients whose age ranged between 6 to 12 years old. By using 18 of these digitized points, the mandible were discretized into 18 triangular finite elements representing different areas of mandible. Four parameters were used to describe changes of finite elements and compare to the control groups of 18 cases without chin cup treatment. 　　The results were described as: 　　(1)The cephalometric parameters for changes in absolute mandibular length are given by mandibular ramus length and mandibular body length. Both of these values showed decrease in percentage value from the control rate of change during active therapy. 　　(2)In the FEM results, there are two elements of treatment groups on the lower border of mandible, KLM and LMR, showed increase in size ratio (p<0.05). And from the anatomic view, the mandibular body showed decrease in size ratio of treatment groups. 　　(3)In the FEM results, there are several elements of treatment groups,including ABC, CDE, EJK, GMN, ELM, LMR, OQR, OMR elements, showed significant change in form ratio. And from the anatomic view, the chin area showed significant change in form ratio of treatment groups. 　　(4)Pre end post-adolescent period can lead to FEM results different. 　　From these results on comparing the control and therapeutic changes of the mandible, it may be assumed that orthopaedic chin cup force modify normal mandibular growth and closely associate with mandibular remodelling. However, details of the mechanism about the cellular activity inducing bone resorption and deposition are still unclear and hence further investigartion with biomechanical, histological approaches will be needed in future studies.

碩士
長庚大學
顱顏口腔醫學研究所
104
Background/Purpose: The purpose of this study was to determine the position of the mandibular canal in relation to the buccal cortical bone in Chinese patients with the three dentofacial relationships: normal dentition, retrognathism, and prognathism. Methods: Cone-beam computed tomography and lateral cephalograms of patients with normal dentation, retrognathism, and prognathism (n = 32 each group) were reviewed. Measurements of the shortest distance from the outer/buccal edge of the mandibular canal to the inner surface of the buccal cortex, and the distance from the lingula of the ramus to the distal root of the first molar were recorded. One-way ANOVA was performed to compare the three groups. Results: No significant difference was observed between the three groups in the distribution of contact or fusion of the mandibular canal, or in the course of the mandibular canal on the right or left side. When the shortest distance at the lingula on the left side was > 2.1 mm, no instances of contact or fusion were observed. On the right side, 100% of the patients had no contact or fusion when the shortest distance was > 2.7 mm at the lingual. The mandibular canal was nearest the cortical bone at the point halfway between the lingula and the anterior ramus border. Conclusions: The shortest distance from the outer/buccal edge of the mandibular canal to the inner surface of the buccal cortex, measured at the lingual, can predict contact or fusion. During sagittal split ramus osteotomy, surgeons should be very careful at the point halfway between the lingula and the anterior ramus border where the mandibular canal is nearest the cortical bone.

碩士
長庚大學
顱顏口腔醫學研究所
95
Purpose: The purpose of this study were to evaluate the difference in the surgical changes and post-surgical changes between bi-cortical osteosynthesis (BCO) and mono-cortical osteosynthesis (MCO) in the correction of skeletal class III malocclusion with bilateral sagittal split osteotomy (BSSO) in three dimension (frontal and lateral views). Materials and methods: Fifty-seven patients who underwent BSSO to setback the mandible with complete lateral and postero-anterior cephalometric radiographs, taken at the timings of before surgery, one week after surgery, and at least 6 months post-operatively (mean, 9.9 months). Of these patients, 25 patients were in BCO group, and 32 patients were in MCO group. The cephalograms were traced and measured to determine the surgical and post-surgical changes. T-test was performed to see the difference between BCO and MCO, and correlation analyses were performed to evaluate the factors related to the sagittal, vertical, and transverse changes of the mandible. Results: The sagittal relapse rate was 20.4% in BCO group and 24.8% in MCO group. There were no significant differences in sagittal and vertical changes between BCO and MCO during surgery and in post-surgical period. However, the inter-gonial width of BCO group was increased more than that of MCO group in surgical and overall changes. Conclusions: The study suggested that both methods of skeletal fixation had similar post-operative stability by 9.9 months. The choice of skeletal fixation technique therefore depends on the preference of the individual operator. The difference of transverse (width) change of mandible between two fixation methods should be concerned.

Introdução: A maloclusão Classe III de Angle caracteriza-se por uma alteração intermaxilar manifestada por um posicionamento mais anterior da mandíbula em relação à maxila e causada pelo crescimento anormal de uma ou ambos os maxilares. Pode ser devido a modificações esqueléticas e dentoalveolares que são representadas por retrognatia maxilar, prognatismo mandibular ou uma combinação de ambos. Objetivo: Contribuir para um maior conhecimento da malocclusão Classe III assim como uma melhor compreensão dos seus factores etiológicos e dos seus vários tratamentos. Metodologia: Realizou-se uma pesquisa bibliográfica, recorrendo à base de dados PubMed e Elsivier, com os termos “mandibular prognathism”, “Class III maloclusion” e o operador boleano AND com os termos : “Etiology”, “Orthodontic treatment”, “genetica” e “mastigatory muscles”, publicados nos últimos 50 anos. Conclusão: A etiologia da Classe III é multifactorial devido a influências genéticas, físicas ou ambientais. O conhecimento destes factores permite uma melhor compreensão da maloclusão e o estabelecimento precoce dos tratamentos que promovem a recuperação em pessoas com maloclusão de Classe III. A presença dos diferentes tratamentos, que já mostraram a sua eficácia ou que apareceram recentemente, mostra que a abordagem da maloclusão de Classe III está em constante evolução.
Introduction: Angle Class III malocclusion is characterized by an intermaxillary change manifested by a more anterior positioning of the mandible relative to the maxilla and caused by abnormal growth of one or both maxillae. It can be due to skeletal and dentoalveolar changes that are represented by maxillary retrognathia, mandibular prognathism or a combination of both. Objective: Contribute to a greater knowledge of Class III malocclusion as well as a better understanding of its etiological factors and its various treatments. Methodology: A literature search was conducted using the PubMed and Elsivier databases for human and animals studies, with the terms "mandibular prognathism", "Class III malocclusion" combined using the Boolean term AND with the terms: "Etiology", "Orthodontic treatment", "genetics" and "masticatory muscles". published in the last 50 years. Conclusion: The etiology of Class III is multifactorial due to genetic, physical or environmental influences. Knowledge of these factors allows a better understanding of malocclusion and the early establishment of treatments that promote recovery in people with Class III malocclusion. The presence of the various treatments, which have already shown their efficacy or have appeared recently, shows that the approach to Class III malocclusion is in constant evolution.

碩士
高雄醫學大學
牙醫學研究所
89
Mandibular prognathism due to excessive growth of mandible, varies in facial characteristics and incidences amoung the different ethnic proups. People who are seeking management of mandibular prognathism are usually disturbed by prominent lower third of the face, poor chewing function and psychological factors. In Taiwan, the high incidences and more severely dentofacial deformity in mandibular prognathism was noted and the problem could only be solved by combined orthodontic treatment and surgery. The purpose of this study was to investigate the changes in gonial region and the factors contributing to skeletal stability in mandibular prognathism treated by modified intraoral vertical ramus osteotomy. Thirty-two patients( 9 males and 23 females ), treated for absolute mandibular prognathism by modified intraoral vertical ramus osteotomy, were evaluated cephalometrically at least two-years postoperatively. A set of three standardized lateral cephalograms were obtained from each subject, i.e., preoperative (A), immediately postoperative (B1) and two-years postoperatively (B6). Some cephalometric landmarks were used for evaluating the positional and angular change postoperatively. The results showed that (1). In stability, during the postoperative period, the Me moved forward with 1.9mm in 22 patients( group I ) whose mean setback of Me was 13.96mm, and the relapse was 13.61%. In other group, the Me moved backward with 2.46mm in 10 patients( group II ) whose mean setback of Me was 11.31mm, and the backward instability rate was 21.75%( 2.46/11.31). (2). The Go moved backward with 1.35mm and upward with 1.90mm in group I, the gonial angle increased for 3.69°, and angle between palatal plane and mandibular plane was increased for 5.00°; In group II, the Go moved backward with 1.85mm and upward with 3.32mm , the gonial angle increased for 4.06°, and angle between palatal plane and mandibular plane was increased for 5.22°. Both in group I and II, there was a tread for clockwise rotation of mandibular corpus. The length of pterygomasseteric sling was mild increased due to the backward movement of Go. (3). The displacement of condylar process( forward or backward ) didn’t influence the stability, but the condyle could not return to its original position completely. The position of condyle may be controlled by bone remodeling. (4). The results of multiple regression showed that the postoperative stability was only correlated with amount of mandibular setback, and rotation of mandibualr corpus and amount of displacement of condyle could not influence the stability. The amount of Go backward movement depends on two factors, one is the position of osteotomy site in distal segment, and the other is the position of osteotomy site in distal segment immediately postoperative. The more horizontal distance between Go and osteotomy site, the less tread of posterior movement of Go postoperatively. When the distal segment setback to ideal position of occlusion and the osteotomy site was behind to Go, the more distance between osteotomy site and Go, the more tread of posterior movement of Go postoperatively. But when the osteotomy site was before to Go, we found that the horizontal position of Go postoperatively was unchanged nearly. The pterygomasseteric sling could be lengthened and distorted under the limitation and it has potential to recover the original length and position if the stretch was larger then the upper limitation. In our study, there was no relationship between the stability and positional change of Go postoperatively. But in group II, we found the distance between the Rp and osteotomy site was larger then amount of mandibular setback. We suspected that the backward movement of Me was caused by loosening the pterygomasseteric sling or other else. It needs more study cases for further examination.

碩士
長庚大學
機械工程研究所
92
The aims of the project was useing Computer Aided Surgery (CAS) and 3C/3R (CAD, CAE, CAM / RE, RP, RT ) technology applied to surgical operation dormain. This study will be proceeded by dividing into two parts, the first part was 『The Stability Analysis and In Vitro Experiment of Various Screw Rigid Intraoral Fixation for Bilateral Sagittal Split Osteotomy of Mandibular Prognathism』；the second part was 『Measuring Fixator Design for Long Bone Corrective Osteotomy』. In the first part of this study, a high proportion of normal population have been observed to have malocclusion and 5 to 10 % of them are mandibular prognathism in Taiwan. Orthognathic surgery with bilateral sagittal split osteotomy (BSSO) and setback is the treatment of choice. Rigid Intraoral Fixation (RIF) is applied using screws in different numbers and locations. This study employs techniques of finite element (FE) method and CAD system to evaluate the stability of the Rigid Intraoral Fixation methods. Computed tomography (CT) data were obtained from patients with prognathism. The data were reconstructed to display 3-dimensional imaging. A computer model was created using the morphometric characteristics of the osseous tissue, i.e., cortical vs. cancellous bone. Bilateral sagittal split osteotomy on the imaging model was performed simulating realistic operating procedure according to the planning. Six types of fixation methods for the osseous segments were applied using two to three screws on different locations avoiding injury to the inferior alveolar nerve. Detailed stress distribution of screws and alveolar bone were calculated in FE package (ANSYS). The von Mises stress values on and surrounding the screws were the least among the methods when three screws were inserted in a triangular shape across the inferior alveolar nerve. When the screws were aligned in linear setting, the stress values were 4 times higher, implying a significantly elevated loading onto the screws. A triangular shape of the screw position across the nerve presented less stress loading than the linear configuration, and hence providing better stability as the preferred fixation method for bilateral split osteotomy of the mandible. In the second part of this study, treatment for bone deformities secondary to malunited fractures usually require corrective osteotomies, and high incidence of surgical failure rates have been reported. Inaccurate corrections and loss of reductions are among the most common causes, and these technical errors ought to be improved. A new measuring fixator for humeral supracondylar corrective osteotomies in children were designed and used in clinical application. Several surgical trials were performed in vitro using rapid prototype models to simulate different bony deformities. Two patient who had sustained cubitus varus following malunited humeral supracondylar fracture were performed using proposed measuring fixtor. The results of the clinical trial showed the angle of correction was accurated, and the procedure could be carried out by the surgeon himself without additional help, with an average of 1.3 penetration of the physis per each fixating Kirschner wire ( 8 times in 6 K-wire ). The surgical time was reduced, as well as the radiation exposure.