Bleaching Sensitivity Reduction with a Nano-hydroxyapatite Paste

Objective: Bleaching-related sensitivity is believed to be associated with microscopic enamel defects and sub-surface pores which allow peroxide to readily access the pulp. We investigated the ability of a paste containing nano-sized hydroxyapatite (nHAP) crystals [Renamel AfterBleach® (RAB); Sangi] to repair these defects and thus reduce tooth sensitivity. Methods: A randomized double-blind clinical trial was conducted. 42 people were randomly assigned to use either a placebo which didn't contain the active ingredient, G-zeroHAP, or to the commercial product, G-RAB. Participants used 7% HP w/o desensitizer twice daily for 14 days. Applications were 30 minutes. RAB or zeroHAP was applied for 5 minutes following each application of bleach. There were six appointments. V1: screening; V2: impressions;V3: baseline evaluation; V4: week one bleaching; V5: week two bleaching; and V6: one week post bleaching. Starting one week prior to bleaching and ending one week after bleaching stopped, a daily log was used to record use of the bleach twice daily, presence/absence of sensitivity, and to rate sensitivity using a visual analog scale (VAS). Results: For G-zeroHAP vs.G-RAB respectively, the days of sensitivity at each period were: V3= 9 v7; V4= 50 v 20; V5= 26 v 16; V6= 16 v 14. As a group people in G-RAB experienced fewer days sensitivity (Chi Square; p = 0.001). VAS data were non-normal. The 25th scores were 0 for all groups and evaluations. For G-zeroHAP vs.G-RAB respectively, median (75th) scores were: V3= 0(0) v 0(0); V4= 2.1(7.3) v 0(1.2); V5= 0(.8) v 0(0); V6= 0(.1) v 0(0). Variance was high and statistical power was below accepted standards. The data did not support any reliable statistical conclusion. Conclusion: Use of a paste containing nHAP following bleaching resulted in significantly fewer days of sensitivity. Study supported by Sangi Co., Ltd.; Tokyo; Japan.