Effect of different repair methods on the bond strength of resin composite to CAD/CAM materials and microorganisms adhesion: An in situ study

Objective: To evaluate the influence of different repair protocols andin situ aging on colony forming units (CFU) and shear bond strength (SBS) between CAD/CAM materials and resin composite. Methodology: 150 blocks (6 x 5 x 2.5 mm) were made out of each restorative material (CAD/CAM resin composite -RC), polymer-infiltrated ceramic - PIC and glass ceramic (VS), totaling 450 blocks. Fifty blocks of each material were submitted to a 60-day in situ aging by fixing the blocks into cavities prepared in the posterior region of the base of complete dentures. The aged and non-aged blocks were randomly divided into 30 groups of 10 (N = 300) according to the following factors: "Restorative material", "Surface Treatment", and "Aging". Z350 resin composite cylinders were made on the surface of the blocks, and the specimens were submitted to thermocycling, shear test, failure mode analysis, and complementary analyses of roughness, fungal and bacterial CFUs, SEM, and EDS. The SBS (MPa) and CFU/mL data were statistically analyzed by ANOVA and Tukey's test (5%). The other variables were analyzed by qualitative analyzes. Results: The "aging" factor was significant for RC and VS and the "surface treatment' factor was significant for the three restorative materials. Hydrofluoric (HF) acid etching followed by silanization was the best protocol for PIC and VS and diamond bur + SBU was the best protocol for RC. CFU/mL was similar among the restorative materials. Conclusion: In situ aging reduced the bond strength between the resin composite repair and RC and VS materials. Clinical Significance: The repair protocol for each restorative material is different and may be influenced by the time of clinical use.