In Situ and In Vitro Effects of Two Bleaching Treatments on Human Enamel Hardness

Abstract

The aim of this study was to evaluate in vitro and in situ the effects of two bleaching treatments on human enamel surface microhardness. Sixty enamel slabs from recently extracted thirty molars were used. The specimens were polished with sandpapers under water-cooling. The enamel samples were randomly divided in four groups, treated with 10% hydrogen peroxide (HP) or Whitening Strips (WS) containing 10% hydrogen peroxide and using two conditions: in vitro or in situ model. For in situ condition, six volunteers wore an intra-oral appliance containing enamel slabs, while for in vitro condition the specimens were kept in deionized water after the bleaching protocols. The bleaching treatments were applied one-hour daily for 14 days. Similar amounts of bleaching agents were used in both conditions. Before and after bleaching treatments, microhardness was measured. Statistical analysis (ANOVA and Tukey test) showed that in the in situ condition there was no statistically significant microhardness reduction in the bleached enamel (p>0.05). Significant decrease in hardness was observed for enamel slabs bleached with both treatments in the in vitro condition (p<0.05). Regarding the bleaching agents, in situ results showed no difference between HP and WS, while in vitro WS produced the lowest hardness value. It could be concluded that there was no deleterious effect on enamel produced by any of the bleaching protocols used in the in situ model. The reduction of hardness was only observed in vitro.

Use of 35% hydrogen peroxide in tooth bleaching in different clinical time intervals: how long does sensitivity last, and at what times is it more exacerbated?

“…Various researches have evaluated the effectiveness in relation to color change, tooth sensitivity and safety of bleaching gels, by means of diverse techniques (mediate and immediate); concentrations of diverse hydrogen peroxide, carbamide peroxide, with and without sources of light activation for potentiating the bleaching gel (PAULA et al, 2015;DAWSON et al, 2011;BERGER et al, 2012;KEMALOGLU et al, 2014;HENN-DONASSOLLO et al, 2016). However, in this study, we sought to analyze two different bleaching gels with the same concentration of hydrogen peroxide, using the same bleaching technique, with the only difference being the clinical time of treatment.…”

Antioxidant potency of mangosteen peel extract topical application in reversing reduced orthodontic brackets tensile strength after bleaching

“…Previous studies have shown that there is a change in the structure of enamel and the bond strength when the teeth are exposed to bleaching agents. 2,3 The reduction in bond strength has been related to morphological changes in mineralized tissues. Bleaching agents also affect the collagen network of dentin, resulting in denaturing and relative instability of the dentin organic matrix, thereby decreasing the bond strength.…”

“…1 Tooth whitening or bleaching has become one of the most common procedures in this branch of dentistry, adopted by numerous dentists and their patients as the method of choice to improve tooth appearance due to its being minimally-invasive, easy, efficient and effective. 2,3 The number of patients seeking orthodontic treatment who might have a history of tooth bleaching is increasing because, following previous procedures, they usually tend to be conscious of orthodontic problems and desire treatment. 4 Unfortunately, bleaching may lead to a reduction in orthodontic bracket bond strength.…”

A swift, easy and cheap protocol to evaluate the tooth bleaching in vitro

“…Most of the available in vitro dental whitening protocols perform the dental whitening procedure at times greater than 96 hours, making them more time consuming ( 17 , 18 ). This study aims to develop a protocol that performs dental bleaching procedures in vitro in a cheap, fast and accessible manner.…”