Analysis in vitro of acid resistance and permeability of primary tooth enamel after Nd:YAG laser irradiation, associated or not with fluoride

Author(s)

Danielle Torres Azevedo

• Document type: Master's Dissertation
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Odontologia de Ribeirão Preto (PCARP/BC)
• Defense date: 2011-06-03

Examining board members

Regina Guenka Palma Dibb; Daniela Rios; Natanael Barbosa dos Santos

• Advisor: Regina Guenka Palma Dibb

Abstract

The efficiency of lasers associated or not with fluorides, in increasing the acid resistance and decrease of enamel solubility of dental enamel has been confirmed by several studies. Several wavelengths have been used for such purpose, providing good results and representing a simple and non-invasive preventive approach. Although the preventive action of Nd:YAG laser is well known, studies on primary teeth are scarce, especially those that establish safe and efficient parameters, when the laser is either associated with fluoride or used alone. Therefore, the aim of this study was to evaluate the acid resistance and permeability of primary tooth enamel. Sixty-nine human primary molars were used, providing 132 specimens. The quantitative response variables were enamel longitudinal microhardness, demineralization depth and permeability, while the qualitative response variables were surface morphology, presence of fluoride ions and analysis of the chemical components of enamel. Sixty buccal/lingual fragments were used for analysis of acid resistance and microhardness (n=10). After being prepared and treated, thee specimens were subjected to a des-remineralization cycle for artificial caries lesion formation. For analysis of permeability (48 fragments, n=8), SEM and EDX (18 fragments, n=3) and DRX (6 teeth, n=1), only surface treatment was performed in 6 levels: C- Control: no treatment; APF: application of 1.23% acidulated phosphate fluoride gel; APFL: application of 1.23% acidulated phosphate fluoride gel + Nd:YAG laser 0.5W/10Hz in mode contact; FV: application of 5% fluoride varnish; FVL: application of 5%fluoride varnish + Nd:YAG laser; L: application of Nd:YAG laser. Microhardness data (%VM) were analyzed by the Kruskal-Wallis test and demineralization depth (DD) and permeability (P) were analyzed by ANOVA and Fisher′s LSD test (α=5% for all tests). APFL and APF presented the lowest microhardness variation of all groups; lower extension of demineralization was observed in groups APF, APFL, FV, FVL and L, and lower permeability was observed in groups APF, APFL, FV, FVL and L compared to group C. The SEM analysis revealed absence of fissures, craters or any other undesirable surface alteration. The EDX analysis revealed fluoride incorporation in all experimental groups (APF, APFL, FV, FVL), except for the group L. No new compound was found in the DRX analysis when fluoride was associated with the laser. Laser alone or associated with fluoride produced ultrastructural alterations on enamel surface, which might have caused the increase of acid resistance and decrease of permeability, thus indicating that, under the conditions of this study, the Nd:YAG laser used alone or associated with fluoride was capable of inhibiting the demineralization of primary tooth enamel. (AU)

• FAPESP's process: 09/07018-7 - Permeability evaluation and acid resistance of primary enamel after Nd:YAG laser application associated or not with fluor
• Grantee: Danielle Torres Azevedo
• Support Opportunities: Scholarships in Brazil - Master