The longevity of restorations with composites is a matter of great importance in restorative dentistry, as it is directly related to the success of esthetic treatment. The life of the restorations may be affected by several factors: as the material used and the time of clinical use. Moreover, recently admitted that the dentin matrix degradation by matrix metalloproteinases (MMPs) can affect the integrity of the adhesive interface, making the bonding dentin / adhesive is compromised. MMPs are enzymes able to degrade the extracellular matrix components, including collagen. The effect of the use of inhibitors of MMPs, such as doxycycline and chlorhexidine (CHX) has been investigated both in vivo and in vitro. Seeking better results in the durability of adhesive restorations, the aim of this study is to verify the bond strength of dentin / adhesive substrate dentin treated with two concentrations of chlorhexidine (0.12% and 0.2%) and doxycycline (30 mg / ml) and submitted to artificial accelerated aging.Block restorations will be made with composite (Filtek Z350 - 3M ESPE) on exposed dentin surfaces of 96 healthy human molars previously separated into five groups according to surface treatment received: Group I-Phosphoric acid + adhesive system ( Adpter Scotchbond Multi-Purpose - 3M ESPE), Group II - phosphoric acid + 0.12% CHX + adhesive system, Group III - Phosphoric acid + 0.2% CHX + adhesive system, Group IV - doxycycline + Phosphoric acid 30mg/ml + adhesive system. After fabricating the restorations block, the bodies of the test piece will be cut with diamond discs (SYJ - 150 Digital Low Speed Diamond Saw 4, MTI Crystal, Richmond, CA, USA -) in stick format (1.0 x 1.0 mm), according to the technique of light emitting diode "non-trimming". Then again be separated into four subgroups (n = 20) according to which aging will be subjected: Group A - AAS for 480 hours, corresponding to 1 year of clinical use, Group B: EAA of 1440 hours, corresponding to 3 years of clinical use, Group C: EAA by 2400 hours, corresponding to 5 years of clinical use, Group D: No aging (control). Then the samples are coupled to a universal testing machine (Emic - 0.5 mm / min) to perform the microtensile test. The fracture modes are analyzed by Scanning Electron Microscope (Jeol JSM 7500 - IBS, Sony, Tokyo, Japan). Assessments of the nano-infiltration and the hybrid layer will also be carried out through SEM in fold increase in 1000-5000. The results obtained, the data will be analyzed statistically.
News published in Agência FAPESP Newsletter about the scholarship: