Effects of removing residual peroxide and other oxygen radicals on the shear bond strength and failure modes at resin-tooth interface after tooth bleaching.

PURPOSE

To investigate the effects of removing residual peroxide on the bond strength and the failure mode at the interface of resin-based composite and enamel after tooth bleaching.

METHODS

Standard-sized light-cured resin cylinders were formed on, and bonded to the flattened bleached enamel surfaces of 60 human canine and premolars which had previously been subjected to three different surface treatments for 3 minutes: (1) catalase; (2) 70% ethanol; (3) sprayed water. For each experimental group (n=12), non-bleached teeth and 2-week post-bleached teeth without any surface treatment were used for negative and positive control respectively. Specimens were thermocycled, tested in shear until failure, and the results statistically analyzed. All fractured specimens were examined by scanning electron microscopy.

RESULTS

Pretreatment of bleached surface with the catalase and the ethanol prior to bonding significantly improved the composite-enamel bond strength compared to the water-sprayed group (P< 0.05). However, the bond strength level of the ethanol group did not return to the level recorded for the non-bleached negative control group. Scanning electron microscopic examination of randomly selected, fractured specimens indicated that the peroxide-induced reduction in bond strength was related to alterations in both attachment-surface area at the resin-enamel interface and resin quality.