Análise da distribuição das tensões em próteses protocolo mandibulares com estruturas fresadas por CAD/CAM e confeccionadas pela técnica convencional: análise pela fotoelasticidade e extensometria
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Data
2016-12-12
Autores
Medeiros, Rodrigo Antonio de [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O objetivo desse estudo foi avaliar a distribuição de tensão, por meio dos métodos fotoelástico e extensometria, em próteses protocolo mandibulares (tipo Branemärk) com infraestruturas confeccionadas com diferentes materiais e técnicas, sob força de compressão. Foi confeccionado um modelo fotoelástico de uma mandíbula edêntula que recebeu cinco implantes 4x11 mm hexágono externo entre os forames mentonianos. Os grupos foram divididos em: Grupo I - infraestrutura fundida em níquel-cromo com revestimento oclusal em resina acrílica (n=7); Grupo II - infraestrutura fundida em níquel-cromo com revestimento oclusal em cerâmica (n=7); Grupo III - infraestrutura fresada em Zircônia estabilizada por óxido de ítrio com revestimento em cerâmica (n=7). Inicialmente, foi realizado o teste da fotoelasticidade e, posteriormente, a extensometria. Pela metodologia da fotoelasticidade, com auxílio de uma máquina de ensaio universal (EMIC) foram aplicadas cargas axiais de 70 N na região do implante mais anterior, entre os incisivos, e no centro do primeiro molar de cada lado. Por meio de imagens fotográficas e com o auxílio do programa Adobe Photoshop CS6, as imagens foram analisadas de acordo com o número de franjas de alta intensidade nos grupos testados. Para a metodologia da extensometria, as cargas foram aplicadas da mesma maneira da metodologia da fotoelasticidade e a medição das tensões foi realizada em duas regiões distintas. Para a primeira região, dois extensômetros elétricos de resistência foram posicionados horizontalmente na região mesial e distal dos cinco implantes, diretamente sobre a crista marginal do modelo fotoelástico. Para a segunda região, a resina fotoelástica foi removida da superfície vestibular e lingual de cada implante, sendo mantida1 mm de resina intacta, onde os extensômetros foram fixados verticalmente. Foram realizados os mesmos testes de compressão descritos anteriormente. Os valores de tensão registrados foram agrupados em tabelas e submetidas à análise de variância (ANOVA) dois fatores e ao teste de Tukey com significância de 5%. Os resultados das duas metodologias demonstraram menores valores de tensão para o Grupo I, quando comparado aos demais grupos. É possível concluir que as próteses protocolo com infraestrutura fundida em metal e revestimento oclusal acrílico demonstraram melhores resultados biomecânicos.
This study aimed to evaluate the stress distribution in full-arch fixed mandibular prosthesis (Branemärk type) with infrastructure made of different materials and techniques, and under compressive force, through photoelastic and strain gauge analysis. A photoelastic cast of an edentulous jaw was fabricated and received five external hexagon implants (4x11mm) between the mental foramen. The groups were divided into: Group I - Nickel-Chrome fused infrastructure with acrylic resin occlusal coating; Group II - Nickel-Chrome fused infrastructure with ceramic occlusal coating; Group III - Yttria-stabilized zirconia fused infrastructure with ceramic coating. First, the photoelastic analysis was performed and later the strain gauge analysis. A force of 70 N was applied by using a testing machine (EMIC) in the region of the most anterior implant, between incisors, and in the center of the first molar on each side. The images were analyzed by a blinded evaluator through images and by using Adobe Photoshop CS6, according to the number of high intensity fringes in each group. Regarding the strain gauge analysis, the stress measure was performed in two distinct regions. For the first region, two resistance strain gauges were placed horizontally in the mesial and distal regions of the five implants, directly on the marginal ridge of the photoelastic cast. For the second region, the photoelastic resin was removed on the buccal and lingual surfaces of each implant, leaving 1 mm of intact resin, where the strain gauges were placed vertically. The same compression tests described above were carried out. Data were submitted to two-way ANOVA and to the Tukey post-hoc test with 5% level of significance. The results of both methods showed lower stress values for Group I, when compared to other groups. It can be concluded that when rigid materials are used for infrastructure fabrication, the esthetic coating influences the load generated on the marginal bone around the implant. The ceramic coating showed less satisfactory results.
This study aimed to evaluate the stress distribution in full-arch fixed mandibular prosthesis (Branemärk type) with infrastructure made of different materials and techniques, and under compressive force, through photoelastic and strain gauge analysis. A photoelastic cast of an edentulous jaw was fabricated and received five external hexagon implants (4x11mm) between the mental foramen. The groups were divided into: Group I - Nickel-Chrome fused infrastructure with acrylic resin occlusal coating; Group II - Nickel-Chrome fused infrastructure with ceramic occlusal coating; Group III - Yttria-stabilized zirconia fused infrastructure with ceramic coating. First, the photoelastic analysis was performed and later the strain gauge analysis. A force of 70 N was applied by using a testing machine (EMIC) in the region of the most anterior implant, between incisors, and in the center of the first molar on each side. The images were analyzed by a blinded evaluator through images and by using Adobe Photoshop CS6, according to the number of high intensity fringes in each group. Regarding the strain gauge analysis, the stress measure was performed in two distinct regions. For the first region, two resistance strain gauges were placed horizontally in the mesial and distal regions of the five implants, directly on the marginal ridge of the photoelastic cast. For the second region, the photoelastic resin was removed on the buccal and lingual surfaces of each implant, leaving 1 mm of intact resin, where the strain gauges were placed vertically. The same compression tests described above were carried out. Data were submitted to two-way ANOVA and to the Tukey post-hoc test with 5% level of significance. The results of both methods showed lower stress values for Group I, when compared to other groups. It can be concluded that when rigid materials are used for infrastructure fabrication, the esthetic coating influences the load generated on the marginal bone around the implant. The ceramic coating showed less satisfactory results.
Descrição
Palavras-chave
Implantes dentários, Biomecânica, Prótese mandibular, Dental implants, Biomechanics, Mandibular prosthesis