520 Microhardness of CO2 Lased Enamel after Brushing and Cariogenic Challenge

Thursday, March 22, 2012: 3:30 p.m. - 4:45 p.m.
Presentation Type: Poster Session
A. CORRÊA-AFONSO1, L. BACHMANN2, C.G. ALMEIDA1, S.A.M. CORONA3, R.G. PALMA-DIBB3, and M.C. BORSATTO1, 1Department of Pediatrics Clinics, Preventive and Social Dentistry, Ribeirão Preto School of Dentistry, University of São Paulo, Ribeirão Preto, Brazil, 2Department of Physics and Mathematics, Faculty of Sciences and Letters of Ribeirão Preto, Ribeirão Preto, Brazil, 3Department of Restorative Dentistry, Ribeirão Preto School of Dentistry, University of São Paulo, Ribeirão Preto, Brazil
Objective: The purpose of this study was to assess in vitro the brushing action on the microhardness of CO2 laser irradiated enamel after cariogenic challenge.

Method: Twenty sound human molars were selected to obtain forty fragments of 4x4mm. The fragments were randomly assigned to 4 groups (n=10) according to the enamel surface treatment:  G1- no treatment – control, G2 – CO2 laser irradiation, G3 – no treatment + brushing and G4 – CO2 laser irradiation + brushing. The laser device emitting at 10.6 mm wavelength was used, the parameter settings used were: power 0.5W, energy per pulse 0.05mJ, frequency of 10KHz. At G3 and G4 specimens were brushed for 80,000 strokes in a reciprocal action brushing simulator using toothpaste. After surface treatment, the samples were submitted to challenge with acid consisting of a 5-day immersion in demineralizing (6 h) and remineralizing solution (18 h). Next, the specimens were longitudinally sectioned and polished and the enamel demineralization was quantitatively evaluated by cross-sectional microhardness tests. Three indentations were made at 10, 30, 50, 90 and 110 μm from the outer enamel surface. Microhardness indentations were made using a Knoop diamond under a 25-gram load for 5 s. The mean values at all 5 measuring points were then averaged. The area under the curve (KHNxμm) was calculated by numerical integration using the trapezoidal rule. ANOVA one-away and Fisher’s test were performed for the statistical analysis (p<0.05). 

Result: The group G2 (31,185 ±4,706) was statistically different from the groups G1 (26,723 ± 2,446), G3(28,194 ±1,376) and G4(28,207 ±2,234)  which were statistically similar. 

Conclusion: From the results of the present in vitro study it may be concluded that the time of brushing used probably promote a wear in the CO2 lased enamel and them the prevention of demineralization was not observed at brushed group.

This abstract is based on research that was funded entirely or partially by an outside source: FAPESP Grant number 2010/06861-0

Keywords: Cariology, Demineralization, Enamel and Lasers