Estudo comparativo das microdeformações resultantes de cargas estáticas axiais e não axiais em próteses de três elementos implantossuportadas

INTRODUÇÃO: O controle das microdeformações ao redor dos implantes é um fator que pode levar a uma melhor osseointegração e manutenção das estruturas ósseas.OBJETIVO: Avaliar a distribuição de tensões ao redor dos implantes,utilizando-se a extensometria, sob a influência da aplicação de cargas estáticas axiais e não axiais em próteses parciais fixas de três elementos, em diferentes pontos de aplicação de carga.MATERIAL E MÉTODO: Em um bloco de poliuretano, foram instalados três implantes de hexágono interno e, sobre esses implantes, pilares protéticos microunit foram conectados com torque de 20 Ncm. Cilindros plásticos foram utilizados para realização dos enceramentos padronizados que, posteriormente, foram fundidos em liga de cobalto cromo. Extensômetros foram colados na superfície do bloco ao redor dos três implantes. As estruturas metálicas foram parafusadas com torque de 10 Ncm cada. Em seguida, foram realizados carregamentos verticais estáticos de 30 kgf, durante dez segundos, em cinco pontos pré-determinados (A, B, C, D e E), utilizando um dispositivo de aplicação de cargas (DAC).RESULTADO: Os dados foram analisados pelo teste RM ANOVA, que indicou que o efeito entre o ponto de aplicação de carga e os diferentes corpos de prova não foi estatisticamente significante, enquanto que, para o efeito entre os pontos de aplicação de carga, houve diferença (p=0,0001). Em seguida, aplicou-se o teste de comparação múltipla de Tukey.CONCLUSÃO: A aplicação de carga sobre os pontos não axiais D e E produziu um aumento da magnitude de microdeformação ao redor dos implantes

Biomechanical effect of inclined implants in fixed prosthesis: strain and stress analysis

Abstract Introduction Implant inclinations can be corrected using mini abutments at different angulations. Objective To analyze the influence of external hexagon implants in different inclinations (3 levels) on the microstrain distribution generated around three implants. Method A geometric bone model was created through Rhinoceros CAD software (version 5.0 SR8, Mcneel North America, Seattle, WA, USA). Three implants (4.1 × 13 mm) were modeled and inserted inside the substrate at three different inclinations: 0º, 17º and 30º. Next, all groups received mini conical abutments, fixation screws and a simplified prosthesis. The final geometry was exported in STEP format to analysis software and all materials were considered homogeneous, isotropic and linearly elastic. An axial load (300N) was applied on the center of the prosthesis. An in vitro study was conducted with same conditions and groups for validating the tridimentional model. Result Stress was concentrated on the external area of the implants, in contact with the cortical bone and external hexagon. For the bone simulator, the strain increased in the peri-implant region according to the increase in the implant’s inclination. The difference between groups was significant (p = 0.000). The 30º group presented higher stress and strain concentration. Conclusion The microstrain and stress increase around implants directly proportional to the increase of the installation angle

Influência da angulação e desajuste vertical na avaliação de microdeformações ao redor de implantes

Objective: This in vitro study was to evaluate micro strains around of implant, under the influence of angulations and vertical misfit in three-element implant-supported fixed partial dentures during axial loading by using strain gauge analysis. Material and Methods: Three external hexagon implants with straight configuration and three external hexagon implants with angled (17°) configuration were inserted into two polyurethane blocks. To measure micro strain, four strain gauges were bonded onto the surface of each block. Plastic copings were adapted to a standard wax pattern and cast. An axial load of 30 kgf was applied on the center of each implant for 10 seconds, using a load application device. The vertical misfit was measured at six different points by using a stereo microscope with 100-X magnification. Results: The results showed that the values for different implant angulations were significant (P = 0.0086). The Pearson’s correlation test between micro-strain and vertical misfit revealed no correlation between angled configuration (P = 0.891) and straight configuration (P = 0.568). Conclusion: The micro strain was higher for angled implants; no correlation was found between the vertical misfit and the strain values

Validation of a simplified implant-retained cantilever fixed prosthesis

Purpose: To evaluate the stress and strain generated in a fixed four-element prosthesis under the application of axial and nonaxial loads using a simplified implant-supported fixed prosthesis model. Materials and Methods: A 3-dimensional model was constructed containing 3 implants with a conventional anatomical prosthesis (G1). The second model with the same implant system received the simplified prosthesis (G2). A load of 300 N was applied at an axial point and a nonaxial point through finite element analysis software. Results: The G2 group showed different values of stress concentration in the prosthesis, fixation screw, retention screw, and abutments when compared with G1. Within a limit of 10% degrees of acceptability, the stress on the implants and the bone strain were enclosed for both models of prostheses. Conclusion: The simplified fixed prosthesis evaluated presents biomechanical behavior similar to an anatomical prosthesis in the implants and in the surrounding bone structure

Effect of Framework Type on the Biomechanical Behavior of Provisional Crowns: Strain Gauge and Finite Element Analyses

The aim of this study was to evaluate the effects of different frameworks on the biomechanical behavior of implant-supported provisional single crowns to indicate or not the use of plastic framework as infrastructure. For finite element analysis, a hemi-jaw stone model was scanned and modeled with an external hexagon implant. A framework was screwed onto the implant and a crown was constructed over it. The set was made in triplicate according to framework type: plastic, cobalt-chromium (CoCr), and titanium. Models were exported in volumetric format to analysis software where structures were considered isotropic, linear, elastic, and homogeneous. Axial loads (100, 200, and 300 N) were applied to the fossa bottom, and the system's fixation occurred on the bone base. For strain-gauge analysis, the same hemi-jaw model was built in polyurethane and an implant was placed on it. Three crowns were made, each one with a different framework. Four strain gauges were glued around the implant to obtain microstrain values. The data were analyzed by three-way analysis of variance (ANOVA) and Tukey tests (P < .05). Finite element analysis exhibited microstrain results for bone, von Mises stress values for the implant and screw, and maximum principal stress values for the crown. For computational method, as the applied load increased, so did the stress generated. Titanium frameworks concentrated more stress in the crown and bone, while plastic ones concentrated more in the implant and screw. ANOVA showed that the higher the load value and the framework elastic modulus, the higher the generated microstrain in bone. It can be concluded that all evaluated framework types can be used in the manufacturing of provisional crowns

Microscopic evaluation of implant platform adaptation with UCLA-type abutments: in vitro study

Abstract Introduction The fit between abutment and implant is crucial to determine the longevity of implant-supported prostheses and the maintenance of peri-implant bones. Objective To evaluate the vertical misfit between different abutments in order to provide information to assist abutment selection. Material and method UCLA components (N=40) with anti-rotational system were divided as follows: components usinated in titanium (n=10) and plastic components cast proportionally in titanium (n=10), nickel-chromium-titanium-molybdenum (n=10) and nickel-chromium (n=10) alloys. All components were submitted to stereomicroscope analysis and were randomly selected for characterization by SEM. Result Data were analyzed using mean and standard deviation and subjected to ANOVA-one way, where the groups proved to statistically different (p=<0.05), followed by Tukey&#8217;s test. Conclusion The selection of material influences the value of vertical misfit. The group machined in Ti showed the lowest value while the group cast in Ni Cr showed the highest value of vertical misfit