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

Juliana do Carmo Públio1, Maria Beatriz Freitas D’Arce1, Anderson Catelan1, Gláucia Maria Bovi Ambrosano2, Flávio Henrique Baggio Aguiar1, José Roberto Lovadino1, Débora Alves Nunes Leite Lima1, *
1 Department of Restorative Dentistry, Piracicaba Dental School, University of Campinas, Av. Limeira, 901, Areião, 13414-903, Piracicaba, SP, Brazil
2 Department of Community Dentistry, Piracicaba Dental School, University of Campinas, Av. Limeira, 901, Areião, 13414-903, Piracicaba, SP, Brazil

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© Públio et al.; Licensee Bentham Open

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution-Non-Commercial 4.0 International Public License (CC BY-NC 4.0) (, which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

Correspondence: Address correspondence to this author at the Department of Restorative Dentistry, Piracicaba Dental School, UNICAMP, Areião, P.O. Box 52, Zip code 13414-903 Piracicaba, SP, Brazil; Tel: +55 19 2106-5339; Fax: +55 19 2106-5218; E-mail:


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.

Keywords: Bleaching agents, Color, Dentin, Enamel, Spectrophotometry, Tooth discoloration.