RESUMO
Introduction: Matrix metalloproteinases enzymes (MMPs) can degrade the hybrid layer which can cause failure of composite restorations. Chlorhexidine gluconate 2% can reduce MMPs activity and increase the bond strength of the resin to dentin. Purpose: This study aims to determine the role of the duration of chlorhexidine gluconate 2% application on shear bond strength of a total-etch bonding agent. Methods: A total of 36 freshly extracted maxillary premolars were removed occlusally by one-third of the crown using a carborundum disc until the dentin was exposed. Specimens were divided into four groups n(9). The dentin surfaces were etched for 5s. Group A is the control group. In group B, chlorhexidine gluconate 2% was applied for 30s. In group C, chlorhexidine gluconate 2% was applied for 60s. In group D, chlorhexidine gluconate 2% was applied for 90s. The universal adhesive was applied afterwards and then followed by composite to the dentin surface. All specimens were stored in artificial saliva at 37°C for 24 hours. The shear bond strength was tested using a universal testing machine. Results: There was an increase in the shear bond strength of the bonding agent along with the additional application duration of chlorhexidine gluconate 2%. All groups gave higher MPa values than the control group. The shear bond strength in group A (control) was 12.64 MPa; Group B (30s of chlorhexidine) was 16.93 MPa; Group C (60s chlorhexidine) was 18.23 MPa; group D (90s of chlorhexidine) was 18.47MPa. Conclusion: Duration of chlorhexidine gluconate 2% application affects the shear bond strength of the bonding agent with the total-etch system. The effective duration of chlorhexidine gluconate 2% for the restorative procedure is 60 seconds.
