The Influence of Different Bleaching Protocols on Dentinal Enzymatic Activity: An In Vitro Study

Abstract

This study aimed to investigate matrix metalloproteinase (MMP) activity in human dentin using in-situ and gelatin zymography, after at-home and in-office bleaching, related to their clinical exposure times. Dentin specimens (n = 5) were treated with 35% hydrogen peroxide (50 min per session/4 sessions), 10% carbamide peroxide (180 min/21 sessions), or no treatment. All were subjected to in-situ zymography. Dentin slices were, subsequently, obtained, covered with fluorescein-conjugated gelatin, and examined with confocal laser-scanning microscopy. The fluorescence intensity was quantified and statistically analyzed using one-way ANOVA and Bonferroni tests (α = 0.05). Furthermore, gelatin zymography was performed on protein extracts obtained from dentin powder (N = 8 teeth), treated with hydrogen peroxide or carbamide peroxide, with different exposure times (10/50 min for hydrogen peroxide; 252/1260 min for carbamide peroxide). The results of the in-situ zymography showed no statistical differences between the bleached specimens and the control group, with a medium level of gelatinolytic activity expressed in the dentin tubules. The results of gelatin zymography showed an increased expression of pro-MMP-9 in carbamide peroxide groups. The expression of pro-MMP-2 decreased in all the experimental groups. The bleaching treatments performed on the enamel of sound teeth do not influence dentinal enzymatic activity. However, when unprotected dentin tissue is bleached, matrix metalloproteinases are more expressed, particularly when carbamide peroxide is used, proportional to the exposure time.

Treatment Durations and Whitening Outcomes of Different Tooth Whitening Systems

“…The concentration of HP influences the amount of reactive oxygen species available to oxidize the organic structure of dental tissues [ 2 ], which in turn affects the effectiveness and speed of the whitening process. For at-home whitening protocols, a concentration of 10% CP is an equivalent of 3.5% HP [ 21 ]. The low concentration of active ingredient in the CP formulation means that a much longer treatment duration, up to 10 h per day [ 5 ], is required to achieve the desired whitening outcomes, as compared to higher concentrations of HP products.…”

Assessing the Viability of Laser-Activated Dental Bleaching Compared to Conventional In-Office Bleaching Methods: A Systematic Review of Clinical and In Vitro Studies

“…The potential advantages of laser activation of bleaching materials have not been widely embraced by the scientific community, even though numerous studies have been performed over many years [11,12,[44][45][46]. Acceleration of the bleaching procedure, shortening of the gel-tissue interaction time, and a more efficient and targeted production of ROS, along with reductions in side effects, are some of the possible benefits declared [1,47]. There is inconsistency of study findings which can be attributed to the diverse study designs, variations in whitening materials utilized, and the usage of differential activating lights [40].…”