Analysis of the importance of occlusal plane reproduction in mounting models in semi-adjustable articulator for orthognathic surgery

Orientador: Roger William Fernandes MoreiraDissertação (mestrado) - Universidade Esstadual de Campinas, Faculdade de OdontologiaResumo: Nas cirurgias ortognáticas bimaxilares o registro e a transferência da inclinação do plano oclusal prévia à montagem dos modelos em articulador semi-ajustável são obtidos a partir do emprego do arco facial. No entanto, várias publicações demonstraram falhas na fidelidade desse registro ao se comparar a inclinação do plano oclusal dos modelos em articulador com a inclinação obtida nas telerradiografias de perfil dos pacientes estudados, enfatizando que o plano de Frankfurt não apresenta coincidência com o arco facial e, conseqüentemente, não pode ser considerado paralelo ao braço superior do articulador. Nesse sentido, este trabalho se propôs a avaliar se a alteração da inclinação do plano oclusal em 6° no sentido anti-horário acarreta alterações significativas nas cirurgias de modelos submetidos a reposicionamento superior de maxila e avanço mandibular. Cada grupo foi constituído por 10 modelos maxilares idênticos e 1 modelo mandibular, apresentando excesso vertical de maxila e retrognatismo mandibular, com trespasse horizontal de 6mm e vertical de 1mm, sem assimetrias. Os modelos do grupo controle apresentavam plano oclusal com inclinação de 13°, enquanto que os modelos do grupo de estudo tiveram essa angulação modificada para 7°. Empregando-se a plataforma de Erickson, todas as medidas pré-operatórias foram realizadas de acordo com o método descrito por Ellis III (1990). Adicionalmente, outros 2 modelos maxilares foram montados seguindo as mesmas características dos modelos do grupo controle, denominados modelo no1 (M1) e modelo no2 (M2), submetidos a reposicionamento superior de maxila de 6mm e 10mm, respectivamente. Finalizada a cirurgia dos modelos, 2 guias intermediários foram confeccionados, sendo utilizados posteriormente para o reposicionamento superior dos modelos maxilares de ambos os grupos. Considerando o plano oclusal do grupo controle com angulação maior do que o real em relação ao braço superior do articulador (13°) e, empregando-se o guia cirúrgico intermediário confeccionado a partir das cirurgias do modelo M1 e M2 nas cirurgias dos modelos pertencentes ao grupo de estudo (plano oclusal de 7°, considerado correto), aplicando-se o teste t Student pareado, observou-se que as medidas verticais e médio-laterais aferidas não sofreram variações estatisticamente significantes. No entanto, a cada 6mm de intrusão maxilar, a posição ântero-posterior do incisivo central foi alterada 0,48mm posteriormente (p<0.05). Adicionalmente, ao se realizar 10mm de intrusão maxilar, uma média de reposicionamento posterior de 0,94mm foi observada (p<0.05). Diante dos resultados obtidos, é possível concluir que o erro no registro do plano oclusal no sentido anti-horário é capaz de posicionar a maxila posteriormente nos casos em que o reposicionamento superior da maxila é executado. No entanto, embora as variações encontradas sejam estatisticamente significantes, clinicamente são irrelevantes.Abstract: The face-bow is indicated to obtain the inclination of the occlusal plane in two-jaw surgeries before mounting the casts on the semi-adjustable articulator (SAA). However, there are many scientific data which shows inaccuracy of the face-bow transference when the inclination of the maxilla is compared on the articulator and on lateral cephalometric radiographs. This implies the Frankfurt horizontal plane is not parallel to the upper arm of the SAA. The aim of this study was to evaluate whether a 6° counterclockwise change in occlusal plane inclination would produce significant modifications on the final result of a maxillary impaction and mandible advancement model surgery. Four groups were used in this study. Each group had 10 identical maxillary casts mounted on the SAA and one mandibular cast. All groups were mounted on the SAA with vertical maxillary excess and mandibular retrognathism, with 6 millimeters of overjet and one millimeter of overbite, without asymmetry. The maxillary casts of the two control groups were mounted with an inclination of 13° of the occlusal plane, while the maxillary casts of the two study groups were mounted with an inclination of 7° of the occlusal plane. Two different impactions were tested, an impaction of six millimeters and an impaction of 10 millimeters. With the aid of the Erickson platform, preoperative measures of the casts were performed according to the method described by Ellis III (1990). To control the movement of the maxilla during model surgery, another two maxillary and mandibular casts were mounted on the SAA using the same references of the control group. These two SAA were used for splint fabrication. One splint for an impaction of 6 mm and another for an impaction of 10 mm. These splints were used in the study groups to simulate the proposed movement. The final measures of the maxillary casts after impaction were obtained using the Erickson platform. The results of control and study groups were compared using the t-test. There were no statistical differences between control groups and study groups in the vertical and latero-lateral movements of the models. The antero-posterior movement of the upper incisor was statistically significant for both study groups. In the 6 millimeter impaction group the mean difference was 0,48 millimeters (p<0.05) and in the 10 millimeter impaction group the mean difference was 0,94 millimeter (p<0.05). In conclusion, mistakes in cast mounting on the SAA may produce a retruded final of the operated maxillary casts. Although statistically significant, the values are small to produce differences in the final clinical result.MestradoCirurgia e Traumatologia Buco-Maxilo-FaciaisMestre em Clínica Odontológic

Mechanical And Photoelastic Analysis Of Four Different Fixation Methods For Mandibular Body Fractures.

The aim of the present study was to compare four methods of fixation in mandibular body fractures. Mechanical and photoelastic tests were performed using polyurethane and photoelastic resin mandibles, respectively. The study groups contained the following: (I), two miniplates of 2.0 mm; (II) one 2.0 mm plate and an Erich arch bar; (III) one 2.4 mm plate and an Erich arch bar, and (IV) one 2.0 mm plate and one 2.4 mm plate. The differences between the mean values were analyzed using Tukey's test, the Mann-Whitney test and the Bonferroni correction. Group II recorded the lowest resistance, followed by groups I, IV and III. The photoelastic test confirmed the increase of tension in group II. The 2.4 mm system board in linear mandibular body fractures provided more resistance and the use of only one 2.0 mm plate in the central area of the mandible created higher tension.43306-1