Effect of temperature and storage time on dental bleaching effectiveness.

OBJECTIVE: To evaluate the effect of storage time and temperature on the effectiveness of bleaching agents. METHODS: Enamel slabs were randomly allocated according to the concentration of carbamide peroxide (CP): 10% (CP10) and 16% (CP16). Shade evaluations were conducted at baseline and then after 3 and 12 months of storage at 3 different temperatures: 10 degrees C (+/-2 degrees C), 25 degrees C (+/-2 degrees C), and 35 degrees C (+/-2 degrees C). Objective color evaluation was performed (spectrophotometer CIEL*a*b* system and CIEDE2000) to calculate the color change (DeltaE(00) ). Subjective evaluation was performed using the VITA classical shade guide followed by shade variation (DeltaS). RESULTS: The bleaching effect of different CP concentrations (10% and 16%) at baseline showed no differences with regard to objective (DeltaE(00) ) and subjective parameters (DeltaS) (P > .05). No differences were observed between CP concentrations stored for the same length of time and at the same temperature for either parameter (P > .05). In terms of objective measurement (DeltaE(00) ), a reduction in the bleaching effect was shown for both CP concentrations (10% and 16%) when stored for 12 months at 35 degrees C, and compared with the baseline (P < .05). As regards the subjective parameters (DeltaS), after 12 months, both CP concentrations (10% and 16%) stored at 35 degrees C showed a decrease in bleaching capacity compared to baseline (P < .05). CP10 and CP16 stored at 10 degrees C and 25 degrees C did not suffer any loss in bleaching ability, even after 12 months (P > .05). CONCLUSIONS: The storage of bleaching agents for long periods at high temperatures can reduce the bleaching effectiveness of CP at 10% and 16%. CLINICAL SIGNIFICANCE: Clinicians must be made aware that they should store their bleaching products under proper temperature conditions and use them within an appropriate time frame; otherwise, the bleaching effect could be lost.