Effect Of Microabrasion During Tooth Whitening On Enamel Bonding

Objective:The objective of this study was to assess effects of enamel microabrasion during tooth bleaching on enamel bonding properties.Method:49 extracted human teeth were divided into three groups. 28 of the teeth were left with their natural surface intact while 21 were polished by 50μm Al2O3 pond to form a flat surface.7 of the teeth with natural surface were stored in artificial saliva solution at 37℃. The left 42 teeth (21 with polished surface and 21 with natural surface) served as the experimental side and received the Opalescence (10% carbamide peroxide) whitening product for 3 weeks,6 hours every day. Post-bleaching intervals include:day 1 (7 polished surface and 7 natural surfaced),1 week (7 polished surface and 7 natural surfaced), and 2 weeks (7 polished surface and 7 natural surfaced). All of the teeth were bonded with EmpressⅢceramics by RelyX Veneer cement. All the specimens were stored in 37℃normal saline for 24 hours and tested under shear loading until fracture on the universal testing machine.Result:No significant difference exited between natural surface and polished surface teeth for all groups at both day 1, week 1 and week 2 (P>0.05). On day 1, both treated groups had significant lower bond strength than control group (P<0.05). One week later, both treated groups also had significant lower bond strength than control group (P<0.05). After two weeks, no significant difference exited between any groups (P>0.05). The resin-enamel interface was the most common site for fracture.Conclusion:1. Opalescence bleaching product (10% carbamide peroxide) can increase the surface fineness of enamel.2. Bleaching significantly decreased bond strength initially. On the other hand, after two weeks, bleaching had no significant effect on bond strength. However, there was no difference between natural surface and surface with microabrasion treatment.3. The resin-enamel interfaces in bleached enamel exhibited more defects.