Bonding of composite resin using different enamel etchants.

Bonding systems make use of different types and concentrations of enamel etchants. The purpose of this in vitro investigation was to determine the shear bond strength of composite resin to etched enamel using different enamel etchants. The following etchants were used: 35 per cent phosphoric acid for 30 seconds, (Group 1, control), 10 per cent phosphoric acid for 20 seconds (Group 2), 10 per cent maleic acid for 15 seconds (Group 3), 65 per cent phosphoric acid for 30 seconds (Group 4) and 10 per cent citric acid/3 per cent ferric chloride for 30 seconds (Group 5). Composite (Z100) stubs were bonded to the adhesively treated etched enamel surfaces using a rubber split mould. The bonded specimens were stored in distilled water for 24 hours before they were stressed to failure using a shear load in an instron testing machine. Data were analysed statistically (Student-t-test). The micromorphology of the enamel etched with the different etchants was also evaluated in a SEM. Shear bond strength (MPa) for the different groups were as follows: group 1 (23.9), group 2 (18.9), group 3 (18.0), group 4 (20.4) and group 5 (15.6). Ten per cent maleic acid, 10 per cent phosphoric acid and 10 per cent citric acid/3 per cent ferric chloride demonstrated lower enamel bond strengths than conventional 35 per cent phosphoric acid.