Influence of pulse emission mode of CO2 laser and the acidulated phosphate fluoride in the control of enamel demineralization - Analysis in vitro and in situ.

Author(s)

Ana Barbara de Araujo Loiola

• Document type: Master's Dissertation
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Odontologia de Ribeirão Preto
• Defense date: 25 jan. 2013

Examining board members

Silmara Aparecida Milori Corona; Maria Cristina Borsato; Vivien Thiemy Sakai

• Advisor: Silmara Aparecida Milori Corona

Abstract

Due to the importance and prevalence of dental caries, and the absence of studies in the literature about the influence of pulse emission mode of CO2 laser to control enamel demineralization, the purpose of this study was to evaluate in vitro and in situ different pulse emission mode of CO2 laser with or without 1.23% acidulate phosphate fluoride, in the control of enamel demineralization. The factors studied were the CO2 laser pulse mode (λ = 10.6 μm, 1 W, in a non-contact, blurry at a distance of 4 mm) at 4 levels (A. continuous B. repeated pulse, C. ultra-pulse, D. absence of irradiation - control) and surface treatment at 2 levels (A. 1.23% acidulated phosphate fluoride gel, B. placebo gel - control). For the in vitro study, 120 bovine enamel slabs were subjected to cariogenic challenge (demineralizing solution pH 5.0 for 6 h and remineralizing solution pH 7.0 for 18 h at 37°C) and randomly assigned into groups according to the treatment. The subsurface microhardness was measured at 30μm from surface, performing three steps of 100 micrometers away from one another, in 4 moments: 1 - initial (to select the specimens),2 - after initial cariogenic challenge, 3 - after surface treatment and 4 - after final cariogenic challenge. Scanning electron microscopy was employed to obtain representative images. Analysis of Variance (ANOVA) evaluated the microhardness data and found that there was no statistically significant difference between groups (0,3864). The in situ study design featured a 2x2 cross-over, double-blind, with two phases of 14 days and a 14 day washout. For this, 11 volunteers (n = 11) wore palatal appliances containing bovine enamel blocks that were previously subjected to pH cycling and then received one of the treatments: 1.23% acidulated phosphate fluoride (APF) + CO2 laser, 1.23% acidulated phosphate fluoride, placebo gel (PLA) + CO2 laser and placebo gel (PLA). Biofilm was accumulated on the blocks and 8 times a day the volunteers trickled sucrose solution, simulating a cariogenic challenge. In 14 days the biofilms formed on the enamel blocks were collected for microbiological analysis. The subsurface microhardness was measure at 2 moments: 1 - Initial and 2 - Final. Scanning electron microscopy was used for qualitative analysis of the enamel surfaces. Analysis of Variance (ANOVA) evaluated the microhardness data and showed no statistically significant difference between groups (p=0.3017). For microbiological analysis, Kruskal-Wallis test showed no statistically significant difference between the count of Streptococcus mutans (p=0.9521) and lactobacilli (p=0.8552). Thus, it can be concluded that in this study the CO2 laser and the APF did not control tooth enamel demineralization and the formation of biofilm in situ, regardless of the pulse emission mode of CO2 laser used. (AU)

• FAPESP's process: 11/05363-9 - Influency of mode emission pulse of CO2 laser and acidulated phosphate fluoride in the control of enamel demineralization: in vitro and in situ analysis
• Grantee: Ana Bárbara de Araújo Loiola
• Support type: Scholarships in Brazil - Master