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

Author(s)

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

• Document type: Journal article
• Source: LASERS IN DENTISTRY XVI; v. 7549, p. 12-pg., 2010-01-01.

Abstract

This study investigated the compositional and crystallographic changes on enamel when irradiated by Er,Cr:YSGG (lambda=2.78 mu m, 8.5J/cm(2)) or Nd:YAG (lambda=1064nm, 84.9J/cm(2) 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 alpha-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. (AU)

• FAPESP's process: 05/51689-2 - Optics and Photonics Research Center at UNICAMP
• Grantee: Hugo Luis Fragnito
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC
• FAPESP's process: 06/06746-0 - Methodology to evaluate the effects of laser irradiation in root caries prevention.
• Grantee: Patricia Aparecida da Ana
• Support Opportunities: Scholarships in Brazil - Post-Doctoral