Effect of Alkaline Vs Acid Surface Treatment on Bond Strength of Adhesives Used for Amalgam Repair

Objective: To assess the effect of alkaline versus acid surface treatment on bond strength of adhesives used for amalgam repair. Materials and Method: Sixty cylindrical samples were prepared by condensing amalgam into plastic tubes of 4mm diameter and 10mm length. Tubes were filled up to 5.0mm with admixed amalgam. They were allowed to set hard for three months. The samples were divided into A1, A2 and A3. A1 and A2 had 25 samples each and A3 had 10 samples. Flat exposed surfaces of the samples in A1 were treated with 35% Phosphoric acid for 3 minutes. The samples in A2 were treated with 10% solution of Ca (OH)2. A dentine adhesive containing 4 – META, Amalgabond was applied on the treated surfaces. The adhesivecoated surfaces, with the help of a probe were pushed inside the tubes such that uncoated surfaces came in level with the margins of the tubes on the other end. Samples in A3 were not treated with acid or alkali and were kept as control group. Freshly mixed amalgam was packed against the coated surfaces to completely fill the transparent tubes. The samples were subjected to electromechanical testing machine at the crosshead speed of 10mm/minute to collect the data. Result: Mean bond strength of the control samples was 3.0 MPa. It decreased with 35% phosphoric acid and increased with 10% Calcium Hydroxide in the range of 4.5 MPa. Conclusion: The results of the present study revealed that alkaline treatment brings more hardness to the sample surface, whereas acid softens the surface.