Inhibition of Secondary Caries in Dental Enamel by Er:Yag Laser

Although several studies have demonstrated the caries protective effect of lasers to inhibit subsequent artificial caries-like challenge, the optimum sets of parameters for Er:YAG laser, employed on cavity preparation, that will effectively inhibit secondary caries formation and the possibility to use of bovine instead of human enamel to evaluate the anticariogenic effect on laser studies are not established yet. OBJECTIVES: The aim of the current study was to examine the role of parameters (pulse repetition rate and water flow) in the prevention of in vitro secondary caries formation in human and bovine enamel by means of a pH-cycling model. METHODS: Twelve caries-free human third molars and bovine incisors were sectioned, selected and divided into ten subgroups (n=5) according to cavity preparation (I. Er:YAG laser 2Hz, 2.0mL/min; II. Er:YAG laser 4Hz, 2.0mL/min; III. Er:YAG laser 6Hz, 2.0mL/min; IV. Er:YAG laser 2Hz, 5.0mL/min; V. Er:YAG laser 4Hz, 5.0mL/min; VI. Er:YAG laser 6Hz, 5.0mL/min; VII. Er:YAG laser 2Hz, 8.0mL/min; VIII. Er:YAG laser 4Hz, 8.0mL/min; IX. Er:YAG laser 6Hz, 8.0mL/min; X. high speed handpiece/diamond bur – control group). The specimens of the laser-treated groups were irradiated with 300mJ output. All teeth were restored with resin composite and they were subjected to pH-cycling to produce secondary artificial caries-like lesions. Results were assessed by cross-sectional microhardness testing and statistically analyzed (ANOVA, Tukey's, p<0.01). RESULTS: Regardless the substrate, the cavities prepared with conventional bur (control) demonstrated lower statistically significant microhardness (p<0.01) than that prepared by Er:YAG laser with all parameters tested. CONCLUSION: All parameters tested of Er:YAG laser were able to decrease demineralization in vitro of dental enamel and the bovine teeth constitutes an alternative substrate to be used on studies about anticariogenic effect of Er:YAG laser.

Financial support: FAPESP (grant # 2006/05691-8)