Compositional and crystallographic changes on enamel when irradiated by Nd:YAG or Er,Cr:YSGG lasers and its resistance to demineralization when associated with fluoride

D. M. Zezell; P. A. Ana; C. Benetti; V. P. Goulart; L. Bachmann; C. P. M. Tabchoury; J. A. Cury

doi:10.1117/12.842967

5 March 2010 Compositional and crystallographic changes on enamel when irradiated by Nd:YAG or Er,Cr:YSGG lasers and its resistance to demineralization when associated with fluoride

D. M. Zezell, P. A. Ana, C. Benetti, V. P. Goulart, L. Bachmann, C. P. M. Tabchoury, J. A. Cury

Author Affiliations +

Proceedings Volume 7549, Lasers in Dentistry XVI; 75490G (2010) https://doi.org/10.1117/12.842967
Event: SPIE BiOS, 2010, San Francisco, California, United States

Abstract

This study investigated the compositional and crystallographic changes on enamel when irradiated by Er,Cr:YSGG (λ=2.7μm, 8.5J/cm²) or Nd:YAG (λ=1064nm, 84.9J/cm² associated with black coating), its resistance to demineralization when irradiation is associated with fluoride (APF-gel), and CaF₂-like material formation and retention. Sample surfaces were analyzed by ATR-FTIR (4000-650cm^-1, 4cm^-1) resolution. Irradiation with Er,Cr:YSGG laser promoted a significant decrease on carbonate content of enamel. After Nd:YAG irradiation, it was observed a significant decrease of carbonate and amides I and II. X-ray diffraction showed that both laser irradiations promoted formation of α-tricalcium phosphate and tetracalcium phosphate, and a significant increase on the crystal growth of the enamel apatite (ANOVA, p<0.05 was used for all analysis). These changes can explain the improved resistance of enamel to demineralization observed in the second part of the study, in which 240 enamel slices were divided in 8 groups, received 4 min of professional fluoride gel (APF-gel 1.23%F^-) applied before or after irradiation. After treatments, the formation of calcium fluoride (CaF₂) was determined. The remaining slabs of each group were submitted to a 10-day pH-cycling model and, subsequently, enamel demineralization was evaluated by cross-sectional microhardness. Both lasers significantly reduced enamel demineralization (ANOVA, p<0.05), and the previous APF-gel application followed by laser showed the higher reduction of enamel demineralization. CaF₂ formed before pH-cycling was significantly higher in groups were APF was associated with laser irradiation. After demineralization, these groups also presented higher CaF₂ retention in respect to isolated treatments (only APF or only laser), suggesting its anticaries potential.

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D. M. Zezell, P. A. Ana, C. Benetti, V. P. Goulart, L. Bachmann, C. P. M. Tabchoury, and J. A. Cury "Compositional and crystallographic changes on enamel when irradiated by Nd:YAG or Er,Cr:YSGG lasers and its resistance to demineralization when associated with fluoride", Proc. SPIE 7549, Lasers in Dentistry XVI, 75490G (5 March 2010); https://doi.org/10.1117/12.842967

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