Objectives: Evaluate the volumetric shrinkage and microtensile bond strength (mTBS) of different resin composites in class I restorations perfomed by incremental or bulk technique.
Methods: Values of polymerization shrinkage of composites [Venus (V), Heraeus Kulzer; Filtek Z-250 (Z) and Filtek P90 (P), 3MESPE] were determined (n=5) using a video monitoring device (Acuvolª, Bisco) 10 minutes after light-activation (Olsen light-curing unit, 20 seconds at 800mW/cm²). Class I cavities (8mm x 6mm x 2mm depth) with enamel margins were prepared in eighteen sound human third molars using daimond bur KG Sorensen #3131. The cavities were randomly assigned to 3 groups according to the restorative protocols: G1) Z+Adpter Single Bond 2, 3MESPE; G2) V+Adpter Single Bond 2, G3) P+ P90 System Adhesive, 3MESPE. The groups were subdivided by the number of increments used to perform the restoration: single increment of 2mm (i) and two increments of 1mm (ii) (Olsen light-curing unit, 20 seconds at 800mW/cm²). To facilitate the specimens handling, samples roots were seccionated and the pulp chambers were filled with resin composite. The specimens were made by sectioning with a low speed diamond saw under water cooling in the two long axis (0.7mmx0.7mm) obtaining 20 sticks per group. The specimes were stored in destilated water for 24h-37°C. The sticks were fixed on Geraldeli's device with cyanoacrylate glue and tested by a universal machine with a crosshead speed 0.5mm/min. Data were analysed statistically by analysis of variance one-way ANOVA (shrinkage) and two-way ANOVA (mTBS) and a detailed through the test of Tukey HSD(r²0.05).
Results: There was statistically significant
differences for volumetric shrinkage between resins: Z2.73(0.04)
Conclusions: Independent of the restorative protocol, the composite Filtek P90 showed the lowest volumetric polymerization shrinkage and the lowest bond strength values.