Interação adesiva e tensão de contração de resinas convencionais ou resina bulk fill de viscosidade regular associada à resina bulk fill fluida.

Abstract

Bulk-fill Flow resin composites are frequently used in association with a conventional composite resin on the occlusal surface. The effectiveness of the interaction of these two formulations of Bulk-fill resin composites is uncertain. To analyze the shrinkage stress, bonding interaction and failure modes between different flowable bulk-fill resin composites with conventional resin composites produced by the same manufacturing or with a bulk fill regular resin composite used to restore the occlusal layer in posterior teeth. Three flowable bulk fill composite resins (FBF- Filtek Bulk Fill Flow, 3M-ESPE; SDR- Surefill SDR, Dentsply; OPUS- Opus Bulk Fill Flow, FGM) were associated with the conventional composite resins made by the same manufacture (Z350- Filtek Z350 XT, 3M-ESPE; TPH3- TPH3 Spectrum, Dentsply; OPAL- Opallis, FGM) or with bulk fill regular composite resin (POST- Filtek Bulk Fill Posterior, 3M-ESPE) resulting into 6 groups (n=10). The bonding interaction between both composite resin was tested using microshear bond strength (μSBS). The samples were thermocycled and were tested with 1mm/min crosshead speed and the failure mode was evaluated. The post-gel shrinkage (Shr) of all composite resins was measure using strain-gauge (n=10). The elastic modulus (E) and hardness (KHN) (n=10) were measure using Knoop microhardness. Two-dimensional finite element models were created for analyzing the stress caused by shrinkage and contact loading. The μSBS, Shr, E and KHN data were analyzed using t-Student test and one-way analysis of variance. The failure mode data were subjected to Chi-square test (a=0.05). Stress distribution was analyzed qualitatively. No significant difference was verified for μSBS for all or bulk fill regular paste conventional composite resin for restoring occlusal layer (P=0.349). Cohesive failure of bulk fill flowable composite resins was the most frequent failure mode. The SDR showed lower Shr than FBF and OPUS. POST and TPH3 had lower Shr than FZ350 and OPAL. POST, OPAL and TPH-3 had higher KHN values than SDR, FBF and OPUS. The SDR showed higher E value than FBF and OPUS. TPH3 and Z350 had higher E value than OPAL and POST. POST used on occlusal layer reduced the stress on the enamel interface at the occlusal surface. The use of bulk-fill regular composite resin as occlusal layer for flowable bulk fill composite resins to restore the posterior teeth can be a viable alternative showing similar bonding interaction than conventional composite resin and lower shrinkage stress at enamel margin.