Purpose: To evaluate the relative frequency of sensitivity from hot, cold and soft tissue, in order to determine if there is a pattern of sensitivity during active bleaching.

Materials and Methods: Nite White Excel 2Z and 8 10% carbamide experimental low sensitivity whitening agents were tested. The experimental agents varied slightly in the percentage of KNO3, NaF and/or water content. 171 participants were randomly assigned. For each participant, a scalloped stent was carefully fitted. Participants were supplied with gel, instructed on use and asked to bleach nightly for two weeks. Which day during bleaching (1 to 14) and sensitivity were primary outcomes. Hard tissue (hot and cold), and soft tissue (gingival; tongue; throat) were tracked separately. Use of the tray and the presence of sensitivity were recorded daily.

Results: Of the 171 participants; 90 experienced no sensitivity at any time, 38 only soft tissue sensitivity, 22 only hard tissue sensitivity, and 21 reported both. Although more people noted soft tissue sensitivity, hard tissue sensitivity resulted in more days of sensitivity. Cold resulted in the most days, gum sensitivity was next, and hot was third. Hard versus soft tissue and day were compared (Two-Factor ANOVA). Day was not significant but source was (p < 0.02). Hard tissue (22.4 days) was significantly higher than soft tissue (15.1 days); (Tukey; p < 0.05). Several positive correlations were noted: 1) day of the bleaching cycle and hot (p < 0.023); 2) hot and cold sensitivity (p < 0.0002); 3) gingival & throat (p <0.02). There was a negative correlation between day and tongue (p < 0.02; all tests Pearson Correlation).

Conclusions:. Hot and cold sensitivity occur together, and later in the bleaching cycle. Gingival and throat sensitivity occur together. Tongue sensitivity occurs earlier in the bleaching cycle. Supported by Ultradent Products, Inc.