Determinação das forças geradas por resinas acrílicas ativadas quimicamente durante o processo de transferência da posição de implantes: análise fotoelástica

Abstract

The great number of laboratorial phases during implant-supported prostheses may contribute to deficient passivity fit. This misalignment could lead to screws relieves and also, the loss of osseointegration. Impression technique is an important step to be observed. Many materials and techniques are involved in this stage and acrylic resin is the most frequently material employed. There are two impression techniques, direct and indirect, used with open and closed trays, respectively. The aim of this study was to evaluate the dimensional stability of three direct impression techniques and four commercial acrylic resins by photoelastic method. Three photoelastic casts with two implants each had two squared transfers screwed over the implants. Acrylic resin (Duralay I, Duralay II, GC Pattern and Dencrilay) was used to splint the transfers by three different forms: with metallic bars, prefabricated acrylic resin bars and dental floss. A circular polariscope was used for the photoelastic analysis in four different times (20min, 3, 24 and 36h). The distortion energy (E) and the tension generated in the implant apical region in each experiment were calculated. Data was statistically analyzed (p < 0,05). Significant difference was verified for all acrylic resins when the prefabricated acrylic resin bars (p=0,000) and dental floss technique (p=0,001) were used. However the metallic bars technique did not show statistical difference (p=0,116). The Dencrilay acrylic resin presented the greatest dimensional alterations, except for the metallic bar technique. Duralay II and GC presented the lower values when prefabricated acrylic resin bars were used and Duralay I and GC showed the same results for the dental floss technique. When comparing the techniques, metallic bars presented the lowest values for the resins Duralay I, GC and Dencrilay. For the prefabricated acrylic resin bars, Duralay II resin presented the lowest values. For all resins, dental floss technique showed the worst results. The most appropriate impression technique seems to be the use of metallic bars with the resins Duralay I, Duralay II and GC Pattern.