Influence of Laser Irradiation on Root Caries Prevention

Objectives: The aim of this study was to evaluate the parameters of different lasers (Er:YAG, Nd:YAG and CO2), associated or not to fluoride, on root dentin caries prevention. Methods: Seventy dentin samples obtained from 35 human molars were randomly divided in 7 groups (n=10). A 3X3mm-area on dentin of each sample was irradiated (scanning mode) using the following parameters: G1- Er:YAG- 60mJ/2Hz; water flow (2.0mL/min); G2- similar to the G1, after fluoride application; G3- Nd:YAG- 0.5W/10Hz (contact mode), no water; G4- similar to the G3, after fluoride application; G5- CO2- 0.2W/20Hz, no water; G6- similar to the G5, after fluoride application; G7: no treatment (control). Then, the samples were subjected to a 2-week cariogenic challenge (pH cycling), consisted of the daily immersion in de-remineralizing solutions for 6 and 18h, respectively. After that, samples were sectioned (150µm), polished, analyzed in light microscopy and measured % demineralization lesion. The obtained data were evaluated by Kruskal-Wallis test (p<0.05). Results: The percentage of demineralization lesion observed on control group (G7: 19.08%) was only different from G5 (CO2 without fluoride: 14.48%), that presented the better results (the lowest percentage of demineralization). G2 (22.83%) showed similar to G1 (20.00%) and G7 (19.08%), but was higher than G3 (15.96%), G4 (15.72%), G5 (14.48%) and G6 (17.50%). Er:YAG groups (21.26%) was higher than Nd:YAG groups (15.84%) and CO2 groups (15.91%). Conclusions: It can be concluded that Nd:YAG and CO2 lasers presented better results than Er:YAG, independently of previous fluoride application. Only CO2 increased the acid resistance of dentin, however any treatment can promote a caries preventive effect.