Purpose: To evaluate the bonding performance of a coating material "White Coat" (Kuraray) to enamel.
Methods: Effect of surface treatment on bonding, durability of bonding, as well as re-bonding as a repeated treatment were investigated using extracted human incisors. To evaluate the effect of surface treatment, intact or ground enamel surfaces were treated using White Coat primer for 20 seconds or 40% phosphoric acid (K-etchant) for 10 or 60 seconds, as well as combination usage of White Coat primer and 40% phosphoric acid. Small resin cylinders of the base-coat of White Coat were bonded to the treated surfaces and irradiated for 30 seconds. For the durability test, small resin cylinders of base coat were bonded to intact enamel using White Coat primer and stored in 37 degrees C saline for 1 day, 1 week, 1, 3, and 6 months. Furthermore, to investigate the effect of re-bonding after the removal, re-bonding was done after various removal regimens. A micro-shear test was used to assess the bond strength of all specimens.
Results: Application of the primer for 20 seconds to intact enamel produced a mean micro-shear bond strength of 28 MPa for intact and ground enamel. Values were similar to 10 seconds phosphoric acid etching to ground enamel (P> 0.05). The bond strength of the primed intact enamel did not decrease up to 3 months (P> 0.05), but decreased significantly by 6 months (P< 0.05). The removal and rebonding of the coating, as well as the storage time showed no significant influence on the bonding of the coat (P> 0.05). Consequently, White Coat was considered an acceptable temporary coating material for no longer than 3 months.