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Effect of CO2 and Nd:YAG laser irradiation associated or not with fluoride on sound and eroded enamel and dentine when submitted to erosion in vitro

Grant number: 09/12326-2
Support type:Scholarships in Brazil - Master
Effective date (Start): March 01, 2010
Effective date (End): May 31, 2011
Field of knowledge:Health Sciences - Dentistry - Pediatric Dentistry
Principal researcher:Daniela Rios Honório
Grantee:Maisa Camillo Jordão
Home Institution: Faculdade de Odontologia de Bauru (FOB). Universidade de São Paulo (USP). Bauru , SP, Brazil


This study aimed to evaluate the in vitro effect of different irradiation power densities of CO2 and Nd:YAG lasers on enamel and dentine when subjected to erosion and then evaluate the effect of fluoride associated with the best parameter able to reduce dental erosion considering enamel and dentine healthy and previously eroded. Furthermore, the application of an absorbing photo dye was evaluated on the performance of Nd:YAG. In phase 1, 130 blocks of enamel and 130 blocks of dentine, were equally and randomly divided into 13 groups (n = 10): C -untreated (control), Nd1 and Nd5 - irradiation with Nd:YAG laser (42.45 J/cm2), Nd2 and Nd6 - irradiation with Nd:YAG laser (56.6 J/cm2), Nd3 and Nd7 - irradiation with Nd:YAG laser (84.9 J/cm2), Nd4 and Nd8 - irradiation with Nd:YAG laser (99.05 J/cm2), CO1 - CO2 laser irradiation (enamel: 7.2 J/cm2; dentin: 3.6 J/cm2), CO2 - CO2 laser irradiation (enamel: 21.4 J/cm2; dentin: 10.7 J/cm2), CO3 - CO2 laser irradiation (enamel: 21.4 J/cm2; dentin: 10.7 J/cm2) and CO4 - CO2 laser irradiation (enamel: 28.8 J/cm2, dentin: 14.4 J/cm2). In groups Nd5 to 9 coal-based dye was applied before Nd:YAG laser irradiation. Before irradiation 2/3 of the blocks surfaces were protected with nail varnish for performing profilometry. After irradiation, the blocks were subjected to erosive cycling, consisting of four daily immersions in acid beverage for 2 minutes followed by immersion in artificial saliva for 2 h for 5 days. Blocks of enamel and dentin were evaluated by profilometry after laser application and after 1 and 5 days of erosive cycling. In the second phase, the group that obtained the best result of numerical or statistical wear reduction was used. So 120 blocks of each substrate type were divided into 12 groups (n = 10): C - control without prior erosion; C+EP - control with prior erosion; Nd:YAG - laser irradiation with Nd:YAG (enamel: 56.6 J/cm2 and dentin: 42.45 J/cm2); EP+Nd:YAG - prior erosion followed by Nd:YAG irradiation; F - AmF (1% F) application; F+EP - erosion prior subsequent AmF (1% F) application; Nd:YAG+F - irradiation with Nd:YAG laser and subsequent AmF (1% F) application; EP+Nd:YAG+F - prior erosion followed by Nd:YAG irradiation and subsequent AMF (1% F) application; CO2 - CO2 laser irradiation (enamel: 28.6 J/cm2 and dentin: 10.7 J/cm2); EP+CO2 - prior erosion followed by CO2 laser irradiation , F+CO2 - CO2 laser irradiation and subsequent AMF (1% F) application; F+EP+CO2 - erosion prior CO2 laser irradiation and subsequent AMF (1% F) application. As in stage 1, before irradiation, the blocks were protected (2/3) and after the treatments, the blocks were subjected to erosive cycling as previously described. The blocks were evaluated by profilometry as described. The lasers were analyzed separated. The results were submitted to ANOVA or Kruskal Wallis (as passed or not in the normal curve) and Tukey (p<0.05). The various parameters of Nd:YAG laser did not present effect in relation to dental erosion regardless of the use of photo absorbent dye. In relation to CO2 laser only the energy densities of 28.8 J/cm2 for enamel and 10.7 J/cm2 for dentin showed preventive effect. The previously eroded substrate resulted in greater wear when compared to healthy one. The use of fluoride in most situations had effect in relation to erosion. However the combination of fluoride to the laser showed no synergistic effect, since it was observed a decrease in fluoride preventive effect. (AU)

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Academic Publications
(References retrieved automatically from State of São Paulo Research Institutions)
JORDÃO, Maisa Camillo. Efeito da irradiação do laser de CO2 e Nd:YAG sobre dentina e esmalte hígidos e erodidos quando submetidos a ciclagem erosiva in vitro. 2011. Master's Dissertation - Universidade de São Paulo (USP). Faculdade de Odontologia de Bauru Bauru.

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