Abstract
Tooth whitening efficacy can be influenced by several factors, of which concentration and application time are two of the most important. This in vitro study aimed to evaluate the initial content and release kinetics of the hydrogen peroxide (HP) content, or the carbamide peroxide (CP) content as converted to its HP equivalent, of four tooth whitening products with different concentrations (6% HP, 16% CP, 10% CP, and 5% CP). Titrations with Cerium Sulphate IV were performed to determine HP concentration. HP release kinetics were evaluated by a spectrophotometric technique. The results were expressed as the mean values and 95% confidence interval of the percentage of hydrogen peroxide content during release kinetics. One sample t-test, one-way ANOVA, Tukey post hoc testing, and Pearson correlation testing were used, as appropriate, with a significance level of α = 0.05. The concentration of titrated HP was higher than that indicated by the manufacturers in all tested products (p < 0.01). At the minimum application times indicated by the manufacturers, all products released at least 85% of HP content; the gel containing 10% CP registered the lowest release at 85.49 (81.52–89.46). There was a significant HP release in all products during the application times indicated by the manufacturers. Further studies are needed to assess in vitro release kinetics.
Highlights
The number of dental whitening treatments performed worldwide has increased in recent years due to public demand, and the number of tooth whitening products available on the market has increased [1,2]
The results show that the products exhibit an exponentially fast release of hydrogen peroxide into the aqueous medium during the initial 30 min, after which the release is attenuated to a plateau phase
Previous studies reported that HP and carbamide peroxide (CP) concentrations decrease over shelf time, due to chemical degradation, with a greater effect in hydrogen peroxide-based products [10,29,30]
Summary
The number of dental whitening treatments performed worldwide has increased in recent years due to public demand, and the number of tooth whitening products available on the market has increased [1,2]. The free radicals released split the cyclic carbon rings of pigmentation molecules with high molecular weight into linear ones that are simpler to remove from tooth structure [10,11]. These molecules, in turn, condition a greater reflection of light, giving the perception of brighter teeth [11,12]. The selection of a bleaching product depends on efficacy, release rate, or the potential to cause damage to surrounding structures, and on the differential diagnosis of tooth discoloration and the choice of technique [13,14,15,16]
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