EFFECT OF ACID ETCHANT COMPOSITION AND ETCH DURATION ON ENAMEL LOSS AND RESIN COMPOSITE BONDING

Purpose: To investigate the effects of different acid etchants' abilit y to condition enamel as gently as possible to remove a minimum of sub stance only, to produce a highly retentive pattern, and finally to ens ure frosty appearance of the etched enamel for clinical control of the procedure. Materials and Methods: Two commercial unietch gels, Gluma 2000-1 and Scotchbond Multi-Purpose Etchant, were studied together wit h gels of 5, 10, 20 and 35% phosphoric acid and varying amounts of thi ckening agents in the 20% gel. Enamel loss was measured with a contact -free method by materials and etch duration, and the shortest etching times for dull frosty enamel appearance were determined. Shear bond st rength (SBS) was measured after 24 hours' storage in water. Results: E namel loss was very low with the commercial agents and increased with H3PO4 concentrations and with etch duration. While the commercial comp ounds produced no frosty enamel even after 120-second etch duration, t he phosphoric acids produced frosted enamel after 15, 30, 60 and 120-s econd application of 35, 20, 10 and 5% acids, respectively. All etchan ts and etch durations tested produced effective retentive patterns. No differences in SBS were noted, and the failure modes were consistentl y cohesive in resin.