Do different bleaching protocols affect the enamel microhardness?

ABSTRACT

Objective: Tooth bleaching tends to increase enamel roughness and porosity, in addition to reducing surface microhardness. The aim of this in vitro study was to evaluate the effects of bleaching treatments using different hydrogen peroxide (HP) concentrations, with and without light activation on bovine enamel microhardness. Materials and Methods: The buccal surfaces of sixty bovine incisors were flattened and polished and the enamel specimens were divided into six groups: G1: Control, exposed to artificial saliva; G2: 35% HP applied in two sessions (45’ each); G3: 35% HP applied in two sessions (3 × 15’ each); G4: 35% HP applied in one session (3 × 7’30”) plus hybrid light (HL); G5: 25% HP applied in one session (3 × 7’30”) plus HL; and G6: 15% HP applied in one session (3 × 7’30”) plus HL. After the treatment, the enamel specimens were stored in artificial saliva. The surface microhardness (Knoop) was measured at the baseline, 24 h and 7 days after bleaching. The data was analyzed using the ANOVA test, followed by the Tukey–Krummer test (P < 0.05). Results: All bleaching procedures lead to a decrease in surface microhardness when compared with the control group after 24 h. The lowest change in surface microhardness was found in the specimens treated with 15% HP plus HL. However, 35% HP plus HL induced the highest decrease in surface microhardness. After 7 days of remineralization, the surface microhardness returned to normal levels for all bleached specimens. Conclusion: Therefore, it can be concluded that the bleaching protocols caused a slight enamel surface alteration. However, the remineralization process minimized these effects.

Key words:

Hardness - tooth bleaching agents - tooth remineralization

• REFERENCES

• 1 Borges A, Zanatta R, Barros A, Silva L, Pucci C, Torres C. Effect of Hydrogen Peroxide Concentration on Enamel Color and Microhardness. Oper Dent. 2014 Ahead of print. Doi: 10.2341/13-371-L
• 2 Cervantes A, Bolanho A, Valera MC, Araújo MA. Microhardness study of bovine enamel to bleaching treatment activated for different sources of light. Brazilian Dental Science 2006; 9: 78-86
• 3 Mondelli RF, Azevedo JF, Francisconi AC, Almeida CM, Ishikiriama SK. Comparative clinical study of the effectiveness of different dental bleaching methods - Two year follow-up. J Appl Oral Sci 2012; 20: 435-43
• 4 Giannini M, Silva AP, Cavalli V, Paes LemeAF. Effect of carbamide peroxide-based bleaching agents containing fluoride or calcium on tensile strength of human enamel. J Appl Oral Sci 2006; 14: 82-7
• 5 Tam L. Vital tooth bleaching: Review and current status. J Can Dent Assoc 1992; 58: 654-5 659
• 6 Attin T, Schmidlin PR, Wegehaupt F, Wiegand A. Influence of study design on the impact of bleaching agents on dental enamel microhardness: A review. Dent Mater 2009; 25: 143-57
• 7 Joiner A. Review of the effects of peroxide on enamel and dentine properties. J Dent 2007; 35: 889-96
• 8 Joiner A. The bleaching of teeth: A review of the literature. J Dent 2006; 34: 412-9
• 9 Lewinstein I, Fuhrer N, Churaru N, Cardash H. Effect of different peroxide bleaching regimens and subsequent fluoridation on the hardness of human enamel and dentin. J Prosthet Dent 2004; 92: 337-42
• 10 Sulieman M, Addy M, Macdonald E, Rees JS. A safety study in vitro for the effects of an in-office bleaching system on the integrity of enamel and dentine. J Dent 2004; 32: 581-90
• 11 Soldani P, Amaral CM, Rodrigues JA. Microhardness evaluation of in situ vital bleaching and thickening agents on human dental enamel. Int J Periodontics Restorative Dent 2010; 30: 203-11
• 12 Akal N, Over H, Olmez A, Bodur H. Effects of carbamide peroxide containing bleaching agents on the morphology and subsurface hardness of enamel. J Clin Pediatr Dent 2001; 25: 293-6
• 13 Pinto CF, Paes LemeAF, Cavalli V, Giannini M. Effect of 10% carbamide peroxide bleaching on sound and artificial enamel carious lesions. Braz Dent J 2009; 20: 48-53
• 14 Araujo FdeO, Baratieri LN, Araújo E. In situ study of in-office bleaching procedures using light sources on human enamel microhardness. Oper Dent 2010; 35: 139-46
• 15 Mondelli RF, Azevedo JF, Francisconi PA, Ishikiriama SK, Mondelli J. Wear and surface roughness of bovine enamel submitted to bleaching. Eur J Esthet Dent 2009; 4: 396-403
• 16 Tezel H, Ertas OS, Ozata F, Dalgar H, Korkut ZO. Effect of bleaching agents on calcium loss from the enamel surface. Quintessence Int 2007; 38: 339-47
• 17 Josey AL, Meyers IA, Romaniuk K, Symons AL. The effect of a vital bleaching technique on enamel surface morphology and the bonding of composite resin to enamel. J Oral Rehabil 1996; 23: 244-50
• 18 Götz H, Duschner H, White DJ, Klukowska MA. Effects of elevated hydrogen peroxide ‘strip’ bleaching on surface and subsurface enamel including subsurface histomorphology, micro-chemical composition and fluorescence changes. J Dent 2007; 35: 457-66
• 19 Al-Salehi SK, Wood DJ, Hatton PV. The effect of 24h non-stop hydrogen peroxide concentration on bovine enamel and dentine mineral content and microhardness. J Dent 2007; 35: 845-50
• 20 Basting RT, Rodrigues Jr AL, Serra MC. The effects of seven carbamide peroxide bleaching agents on enamel microhardness over time. J Am Dent Assoc 2003; 134: 1335-42
• 21 Elfallah HM, Swain MV. A review of the effect of vital teeth bleaching on the mechanical properties of tooth enamel. N Z Dent J 2013; 109: 87-96
• 22 Jiang T, Ma X, Wang Y, Tong H, Shen X, Hu Y. et al. Investigation of the effects of 30% hydrogen peroxide on human tooth enamel by Raman scattering and laser-induced fluorescence. J Biomed Opt 2008; 13: 014019
• 23 Wang W, Zhu Y, Li J, Liao S, Ai H. Efficacy of cold light bleaching using different bleaching times and their effects on human enamel. Dent Mater J 2013; 32: 761-6
• 24 Parreiras SO, Vianna P, Kossatz S, Loguercio AD, Reis A. Effects of light activated in-office bleaching on permeability, microhardness, and mineral content of enamel. Oper Dent 2014; 39: E225-30
• 25 Araujo NC, da Costa SoaresMU, Nery MM, Sales WS, Gerbi ME. Effect of pH values of two bleaching gels on enamel microhardness. Gen Dent 2013; 61: 55-8
• 26 Mellberg JR. Hard-tissue substrates for evaluation of cariogenic and anti-cariogenic activity in situ . J Dent Res 1992; 71 Spec No 913-9
• 27 Potocnik I, Kosec L, Gaspersic D. Effect of 10% carbamide peroxide bleaching gel on enamel microhardness, microstructure, and mineral content. J Endod 2000; 26: 203-6
• 28 Alexandrino L, Gomes Y, Alves E, Costi H, Rogez H, Silva C. Effects of a bleaching agent with calcium on bovine enamel. Eur J Dent 2014; 8: 320-5
• 29 Chen X, Chen Z, Lin Y, Shao J, Yin L. Effects of tooth whitening agents and acidic drinks on the surface properties of dental enamel. Hua Xi Kou Qiang Yi Xue Za Zhi 2013; 31: 530-2
• 30 Yesilyurt C, Sezer U, Ayar MK, Alp CK, Tasdemir T. The effect of a new calcium-based agent, Pro-Argin, on the microhardness of bleached enamel surface. Aust Dent J 2013; 58: 207-12
• 31 Salomão D, Santos D, Nogueira R, Palma-Dibb R, Geraldo-Martins V. Acid demineralization susceptibility of dental enamel submitted to different bleaching techniques and fluoridation regimens. Oper Dent 2014; 39: E178-85