AVALIAÇÃO DA INFLUÊNCIA DA CICLAGEM TÉRMICA E MECÂNICA NA EFETIVIDADE DA INTERFACE ADESIVA

Abstract

The aim of this study was to evaluate in vitro the adhesive effectiveness in class V cavities using four different adhesive systems, being submit to thermocycling and occlusal load cycling. The cavities had a dimension of 3x2x1.8 mm3 and were made on amelo-cement junction on buccal and lingual of 80 human premolars (n=160). The used adhesive systems were Adper Single Bond 2, AdheSE, Adper Prompt LPop and One Coat 7.0. The used composite was Synergy® D6. The adhesive and photopolymerization (600 mW/cm2) proceedings were made conventionally and following the manufacturer recommendations. The specimens were divided in 4 groups (n=40) according to adhesive system used. Each group was divided in 4 subgroups (n=10) according to applycated stress (thermocycling, occlusal load cycling and thermocycling+occlusal load cycling). Each subgroup included 1 control group without stressing. The thermocycling was made using 500 cycles, with 5-55 C, dwell time of 15 seg and transfer time of 5 seg. The occlusal load cycling was made applying a force of 40-70 N during 50000 cycles with 2 Hz of frequency. Later, the specimens were impermeabilited and immersed in tracer agent of 50 % silver nitrate solution by 2 hours. Finally, the specimens were prepared for adhesive effectiveness evaluation through optic microscopy 40X (marginal microleakage occurrence) and scanning electronic microscopy 1000X (gaps formation). The tracer agent microleakage was measured qualitative (score) and quantitatively . The gap width was measured on 3 points of center of axial wall. The Kruskal-Wallis and post-hoc de Dunn, and ANOVA two-way and post-hoc Bonferroni tests were used on statistic analysis. Despite of few differences found in used adhesive system performance, the tendency could be observed to the increase of the marginal microleakage in the submitted groups specifically to thermocycling. On the other hand, the axial gaps formation presented progressively higher width in the submitted groups to thermocycling, occlusal load cycling and thermocycling+occlusal load cycling. It was concluded that the used adhesive system presented similar adhesive effectiveness when were submitted to thermal and mechanical stress.