# Assessment of changes in optical and mechanical properties and adverse effects of over-the-counter bleaching agents: An in vitro study

## TL;DR

This study compares over-the-counter tooth bleaching products to in-office treatments, finding similar effectiveness in whitening without affecting orthodontic bracket bond strength.

## Contribution

The study evaluates the effectiveness and safety of OTC bleaching agents on tooth color and orthodontic bond strength in an in vitro setting.

## Key findings

- OTC bleaching agents achieved similar color change to in-office treatments, except for dentifrices.
- No significant differences in gloss or shear bond strength were found between OTC and in-office groups.
- OTC products did not compromise orthodontic bracket bond strength.

## Abstract

This in vitro study evaluated the impact of over-the-counter (OTC) products on the optical properties (color and gloss changes) and mechanical properties (shear bond strength) of tooth enamel subjected to a simulated orthodontic treatment.

80 bovine teeth were selected and subjected to a staining protocol and initial color assessments. Then, orthodontic brackets were bonded on the center of the clinical crown of each sample, and teeth underwent the bleaching protocols. The samples were allocated to five groups (n=16): Conventional in-office bleaching 35% Hydrogen peroxide - positive control (HP35); Dentifrice with 2% HP (DHP); Mouthwash with 2.5% HP (MouHP); Paint-on with 6% HP (PON); Conventional dentifrice without HP - negative control (DWHP). After receiving the bleaching protocol, the samples underwent the shear bond strength test for orthodontic bracket removal. The remaining resin was then removed from the sample surfaces using multi-blade burs. Data was analyzed with Kruskal-Wallis test or one-way ANOVA, with 5% significance.

Regarding color change, multiple comparison analyses showed significant differences (p< 0.05). The HP35 and MouHP groups showed a significantly greater color change compared to the DWHP and DHP groups for both ΔE00 and ΔEab values, while the PON group did not differ significantly from the other groups. The statistical test did not detect a significant difference in post-bleaching gloss increase between the experimental groups (p=0.20). In addition, it did not detect a significant difference between the experimental groups for shear assessment (p=0.14).

Except for dentifrices, the color change outcomes of the evaluated OTC bleaching treatments were as satisfactory as in-office bleaching, without differences between groups for gloss change. The study suggests that the evaluated OTC products did not influence the bond strength of orthodontic brackets to teeth.

Key words:Hydrogen Peroxide, In Vitro Technique, Tooth Bleaching, Tooth Bleaching Agents.