Bonding performance of a temporary tooth coating material to enamel

This study aimed to evaluate the bond characteristics of 6-MHPA monomer-based primer in a temporary tooth coating material set (BeautiCoat, Shofu, Kyoto, Japan), applied to various conditioned enamels. The buccal enamel of thirty premolars was ground flat and the teeth were divided into six groups. This research bleached two groups, acid-etched two groups, and did not condition the remaining two groups. BeautiCoat primer was applied alone, or with activator on the ground and bleached enamel. BeautiCoat primer and FL-Bond were applied on the acid-etched enamel. FL-Bond adhesive on acid-etched enamel served as the control. BeautiCoat flowable resin was then piled on the enamel surfaces and light-cured. The microtensile bond strength (μTBS) was measured and the superficial demineralization, the resin–enamel interface, and failure mode were evaluated with a scanning electron microscope. The μTBS obtained in the non-acid-etched groups was more than half of that obtained in the acid-etched groups (p < 0.05). FL-Bond adhesive on acid-etched enamel showed the highest μTBS values. Marked improvements in μTBS were not observed when activator was combined with primer. No significant difference in μTBS could be found between BeautiCoat primer and FL-Bond adhesive on acid-etched enamel, or among BeautiCoat primer applied with/without activator on the ground and bleached enamel. The cohesive enamel failure ratio was low with the BeautiCoat primer or in the primer and activator groups but high in the FL-Bond group. The adhesive of BeautiCoat provided favorable bond strength with minimal risk of damage to the enamel.