Objective: Tooth whitening or bleaching is a popular and established means for removing extrinsic stain, through either professional treatment or take-home kits. The aim of the present in vitro study was to investigate the effects of an experimental whitening formulation (EWF) on enamel surface hardness compared with commercially available products and a positive control.
Methods: Polished enamel specimens were prepared from human teeth and were randomised into treatment groups based on their baseline Vickers hardness number (VHN). Specimens were incubated in pooled human saliva overnight before the first and in between treatments. Treatments were applied twice daily for 7 days. VHN was measured before and after 7 and 14 treatments. EWF was formulated at 11.2% w/w H2O2 and tested against Crest Whitestrips Premium (CWP), DI water and artificial orange juice (AOJ, 1% citric acid, pH 3.75) as a positive control. Specimen treatment times were EWF-45min, CWP-30min, DI water-45min, AOJ-1min and 45min.
Results: All treatments, apart from AOJ, caused no statistically significant decrease in VHN after 7 and 14 treatments (p<0.05). AOJ-45min caused statistically significantly more softening than any other treatment at all time points measured (p<0.05). AOJ-1min caused statistically significantly more softening than EWF and CWP after 7 and 14 treatments (p<0.05).
Conclusion: The results of this in vitro study support the safety of the experimental tooth whitening formulation to enamel.