Effects of saliva contamination and phosphoric acid composition on bond strength

The purpose of this study was to determine the effects of a phosphoric acid gel and solution, and saliva contamination of etched enamel on the tensile bond strength (TBS) of a posterior composite resin to etched enamel. Ninety-six extracted human permanent maxillary canines were used in this study. The test system developed by Kemper and Kilian was used to determine the TBS of a posterior composite resin (P-10) to enamel. The ground enamel surfaces were etched with 37% H₃PO₄ gel for 60 sec and washed for 15 sec or 30 sec, and with 37% H₃PO₄ solution for 60 sec and washed for 15 sec or 30 sec, respectively. The ground enamel surfaces were also etched with H₃PO₄ gel for 60 sec, washed for 15 sec and rewashed for 15 sec after saliva contamination of the etched enamel for 15 sec, 60 sec and 60 min, respectively. Etched enamel surfaces contaminated with saliva for 15 sec were re-etched for 15 sec and washed for 15 sec. The test specimens were mounted in an Instron machine and subjected to a tensile load at 0.02 inch. min⁻¹. The force required to break a test specimen was recorded, and the bond strengths were calculated and expressed in MN.m⁻². The data were analyzed by ANOVA and Duncan's multiple range test at the 5% level of significance. The H₃PO₄ composition (gel vs solution) and wash times had no significantly different effect on TBS. Only a 60 min saliva contamination significantly reduced TBS. In this study the TBS was determined 24 h after specimen preparation. It is possible that salivary contamination of etched enamel may have an adverse effect on bond strength only after prolonged immersion of the test specimens prior to testing.