Influence of Enamel Thickness on Bleaching Efficacy: An In-Depth Color Analysis

Abstract

This study evaluated the influence of different enamel thicknesses and bleaching agents on treatment efficacy in-depth by spectrophotometry color analysis. Eighty bovine dental fragments were previously stained in black tea solution and randomly assigned into eight groups (n=10), 1.75mm dentin thickness and different enamel thicknesses as follows: 0.5mm, 1.0mm planned, 1.0mm unplanned (aprismatic enamel), and absence of enamel. The 10% carbamide peroxide (CP) and 35% hydrogen peroxide (HP) bleaching gels were applied on the enamel surface following the manufacturer's recommendations. Color of underlying dentin was evaluated at four times: after staining with tea (baseline) and after each one of the three weeks of bleaching treatment, by CIE L*a*b* system using reflectance spectrophotometer (CM 700d, Konica Minolta). The ΔE, ΔL, Δa, and Δb values were recorded and subjected to repeated measures ANOVA and Tukey’s test (α=0.05). The results showed an increase on lightness (L*), with decreased redness (a*) and yellowness (b*). At first and second week, bleaching with CP showed higher whitening effectiveness compared to bleaching with HP and the presence of aprismatic enamel significantly reduced ΔE for bleaching with CP. After three weeks of bleaching, few differences were observed between CP and HP groups, and outer enamel layer caused no influence on bleaching effectiveness. Overall, both at-home and in-office bleaching treatments were effective and the presence of aprismatic enamel did not interfere on the whitening efficacy.

Effect of surface removal following bleaching on the bond strength of enamel

“…Moreover, human and bovine teeth have been reported to exhibit similar behaviors during bleaching treatments [39]. Thus, the present study used bovine teeth as the testing substrates, in accordance with the previous studies [20, 28, 29, 40].…”

Impact of Bleaching before or after Veneer Preparation on Color Masking Ability of Laminate Veneers: An In Vitro Study

“…The bleaching agent applied to the surface of enamel must, in order to bring about the whitening effect, penetrate sufficiently through the enamel layer to the dentine to alter the color of the dentine immediately below the enamel, as bleaching through the enamel does not penetrate the entire depth of the dentine [ 16 ]. In addition, the data from a previous study demonstrated that the presence of at least 0.5 mm of enamel reduced the bleaching efficacy, and the presence of aprismatic enamel resulted in less color change in comparison to the group without aprismatic enamel [ 7 ].…”

“…However, the final results may be unpredictable [ 1 ]. In severely discolored teeth that are not responsive to routine vital bleaching, it may be necessary either to extend bleaching time [ 5 ] or to reduce the enamel surface for veneering without exposing underlying dentine to encourage penetration of bleaching agents into the stained dentine [ 6 , 7 ]. In attempting to treat severely discolored teeth by veneering, there is a considerable risk that the dark shade of the tooth tissue substrate will shine through relatively thin and translucent ceramics.…”

https://www.sciencerepository.org/association-of-in-office-and-supervisoned-in-office-bleaching-protocols-in-molar-incisor-hypomineralization_DOBCR-2-101

“…Considering it, the use of bleaching systems composed only by hydrogen or carbamide peroxide on hypomineralized teeth by itself is not recommended. This is due because despite their ability to disintegrate pigmented molecules in tooth structure, the unstable free radicals generated during the oxide-reduction reaction of these agents are also able to decompose both organic and inorganic contents [9][10][11]. The consequences of this process may worsen the mechanical properties of hypomineralized affected teeth and yet highlight the appearance of MIH opacities [2].…”