Effect of repeated bleaching by low hydrogen peroxide regimens – with and without MI Paste Plus – on enamel hardness and composition

Abstract

Objectives: The aim of the present study was to test the following hypotheses: 1. In-vitro repeated bleaching by low hydrogen peroxide (HP) regimens eat 2-month interval-will affect enamel hardness and composition. 2. The use of MI Paste Plus, GC Co. (MIPP) during bleaching treatments will reduce these possible enamel changes. Methods: Two 14-day bleaching regimens; 1 h/day of 10% carbamide peroxide (CP) gel; Opalescence PF (OpPF) and 30 min/day of 9.5% HP strips; Crest Whitestrips Advanced Seal (CWAS) were evaluated. Each bleaching regimen was applied on enamel three times, separated by 2 months of artificial saliva with or without MIPP regimen. Surface treatment groups (n ¼ 10/group) included:(1) Artificial saliva (control) (2) OpPF, (3) CWAS (4) OpPF-MIPP, and (5) CWAS-MIPP. Vicker Hardness (VH) was repeatedly measured for all groups; at baseline and after 2, 12 and 22 weeks (after each bleaching treatment). The final enamel surface of each group was chemically analyzed using Fourier Transform Infrared Spectroscopy (FTIR). Results: The median VHs (Kg/mm 2 ) were: (1) 310, 312, 330, 343; (2) 299, 272, 283, 264; (3) 320, 277, 271, 255; (4) 300, 311, 304, 316, and (5) 305, 315, 309, 320, respectively. Friedman repeated measures ANOVA on ranks (Dunnett method) indicated that enamel VH was significantly reduced after the third OpPF treatment and after the second and third CWAS treatments. Within OpPF-TMP and CWAS-TMP groups, no significant differences were found among VHs measured at different time intervals (p < 0.05). FTIR of the final enamel surfaces revealed decreased phosphate group intensity; enamel mineral content, for all groups except OpPF-MIPP group where its intensity increased. Significance: Repeating of low HP bleaching regimens e at short intervals e may reduce enamel hardness and mineral content. Daily over-night use of MIPP may preserve enamel hardness and mineral content only if the OpPF regimen is used.

Comparative Evaluation of the Effect of Various Remineralizing Agents on Bleached Enamel Surface: An in Vitro Study

“…This is in agreement with studies by Hala M Abass et al, Se abo hammar et al, Sule Bayrak et al, Asmaa Alkhtib et al [22][23][24][25] and can be due to the fact that the peptides in the CPP-ACP may diffuse into the inter-crystallite spaces, (as the size of the peptide complex is small [~2 nm]) created by bleaching. It localises and increases the bioavailability of calcium and phosphate ions and may enhance the potential for remineralization and deposition of minerals around the "freshly cleaned" enamel crystallites, leading to an increase in hardness thus regaining the prebleaching enamel physical properties.…”

The Effect of Casein Phosphopeptide-Amorphous Calcium Phosphate on the Microhardness of Carbamide Peroxide Bleached Enamel (An in Vitro Study)

“…On the other hand conversely, these results were in contrast with researches done by Abo-Hamar and Etman [33] found that bleaching with 10% carbamide peroxide 1h/day for 14 days or by 9.5% HP 30 min/day for 40 days didn't significantly decrease enamel VH and they explained that by Licensed Under Creative Commons Attribution CC BY it may be due to the balance between the demineralization and remineralization that was performed by artificial saliva.…”

The effect of in-office bleaching materials with different pH on the surface topography of bovine enamel

“…As pH 5.5 is slightly acidic, it can be the reason for dissolution of enamel and increased Ra. Some studies have reported that the pH of bleaching agent has a direct relationship with the surface roughness 36,37) . Acidic bleaching gels can demineralize the enamel and cause increase of surface roughness 36,37) .…”

“…Some studies have reported that the pH of bleaching agent has a direct relationship with the surface roughness 36,37) . Acidic bleaching gels can demineralize the enamel and cause increase of surface roughness 36,37) . Previous studies have revealed that 30-35% H2O2 can increase surface roughness and reduce the calcium-phosphorus ratio [38][39][40] .…”