Development & evaluation of an in-vitro whitening model

OBJECTIVE: To develop a simple and rapid in-vitro whitening model for evaluating bleaching performance of various whitening agents. METHOD: Extracted, sectioned human teeth were stained internally with a concentrated tea solution. Exposed dentin surfaces were sealed. Baseline L*a*b* and classic Vita shade scale measurements were taken using a Vita Easyshade® clinical spectrophotometer. Crest Whitestrips® Premium (CWSP, 10%w/w HP) strips were applied to tooth segments (n=5) for 14, 30 minute treatment periods (30 minutes - twice daily). The whitening formulation was removed (between treatments) by brushing under running water. L*a*b* and classic Vita shade units were re-measured at designated treatment times. Change in Vita shade units was assessed based on a value-based arrangement of Vita shades. A one-way ANOVA (95% LSD) test was performed. RESULTS: Day 1, Day 3, Day 5, and Day 7, respectively (± s.d.):

Mean Delta SVUs:0.6(0.89,3.4(0.55),3.6(0.55),4.0(0.35)

Mean Delta L*:6.66(3.6),9.94(7.34),9.98(6.41),10.36(5.10)

Mean Delta a*:-4.55 (2.50),-6.1(3.58),-6.52(2.73),-6.67(2.85)

Mean Delta b*:-9.21(3.33),-11.69(2.04),-13.09(3.22),-13.31 (2.52)

Tea-stained tooth segments responded to the CWSP product in a time-dependent manner. The model demonstrated statistically significant differences (p<0.05) between various time-points. By day 3 to 5, some color measurement parameters appear to have plateaued; differences between 5 and 7 days results were reduced. Day 7 changes in SVUs and L* correlate to prior published results. Appropriate use of internal controls may allow relative bleaching performance to be assessed. CONCLUSION: This artificial, intrinsic-staining model demonstrated potential for evaluating bleaching performance.