Influence of pH Value of Bleaching Gels on Surface Roughness of Bovine Enamel

Abstract

Objective: The purpose of this study was to evaluate the influence of the pH levels of three in-office bleaching gels on the surface roughness of bovine enamel, after the bleaching protocol. Materials and methods: 36 samples of bovine enamel were obtained, which were cut and divided into three groups (n=12): 40%hydrogen peroxide (Opalescence Boost40%), 35% hydrogen peroxide (Whiteness HP AutoMixx) and 35% hydrogen peroxide (Whiteness HP Blue), receiving a 40-minute application of bleaching. The average pH values were determined using a pH meter during the initial and final application of the gel. A roughness meter was used to assess surface roughness (Ra) before and after bleaching. Data were analyzed with the Friedmann and wilcoxon test (difference between groups); the Kruskall Wallis and U Mann test (difference in each group), as well as Pearson or Spearman test for correlation. Results: There is an increase in pH values from the beginning to the end of bleaching in all groups, except for the 35% hydrogen peroxide group (Whiteness HP Automixx). For surface roughness results there is an increase in all groups. No correlation was found between pH values of the bleaching gels and the surface roughness of the enamel after bleaching. Conclusions: Hydrogen peroxide bleaching gels with high concentrations that have a high or low pH could cause alterations in the surface of the tooth enamel, such as increase in surface roughness.

Effects of bleaching gel containing TiO2 and chitosan on tooth surface roughness, microhardness and colour

“…Although a significant increase in surface roughness values after bleaching with 40% HP was found in the study by Lugo‐Varillas et al ., 28 in other studies, 38,40 as well as in ours, surface roughness values increased but no significant differences were observed.…”

“…The concentration, 28,31 pH, 32,33 application time 34 and content 35–37 of the bleaching agent have been shown to affect microhardness and surface roughness values. However, in these studies, where microhardness and surface roughness measurements were evaluated, the results were not compatible with each other.…”

“…While HP causes mineral changes in dental tissue, it can also cause morphological changes such as increased roughness of the enamel surface and decreased microhardness. 28 In studies where samples were kept in saliva, it was shown that through ion exchange from saliva, the decrease in microhardness resulting from bleaching might be reversed, and lost calcium and phosphate can be regained. 29 In studies with distilled water, it was reported that there is no ion exchange in the dental tissue.…”

“…30 Therefore, in our study, the samples were kept in distilled water instead of saliva so that the side effects of bleaching agents could be detected more clearly. The concentration, 28,31 pH, 32,33 application time 34 and content [35][36][37] of the bleaching agent have been shown to affect microhardness and surface roughness values. However, in these studies, where microhardness and surface roughness measurements were evaluated, the results were not compatible with each other.…”