Fax +41 61 306 12 34 E-Mail karger@karger.ch www.karger.com Original Paper Caries Res 2009;43:261–268 DOI: 10.1159/000217858 CO 2 Laser (10.6 m) Parameters for Caries Prevention in Dental Enamel M. Esteves-Oliveira a, c D.M. Zezell d J. Meister a R. Franzen a S. Stanzel b F. Lampert a C.P. Eduardo c C. Apel a a Department of Conservative Dentistry, Periodontology and Preventive Dentistry and b Institute of Medical Statistics, RWTH Aachen University, Aachen, Germany; c Restorative Dentistry Department, School of Dentistry, University of São Paulo, and d Centro de Lasers e Aplicações, Instituto de Pesquisas Energéticas e Nucleares, São Paulo, Brazil 9 s (2,036 overlapping pulses) increased caries resistance by up to 81% compared to the control and was even significant- ly better than fluoride application (25%, p ! 0.0001). Scan- ning electron microscopy examination did not reveal any obvious damage caused by the laser irradiation. Copyright © 2009 S. Karger AG, Basel The possibility of making dental enamel more resis- tant to caries attack by irradiation with a CO 2 laser has been described for all its main wavelengths [Featherstone et al., 1998]. The 9.6- m wavelength has 10 times higher absorption in enamel (8,000 cm –1 ) than the 10.6- m wavelength (825 cm –1 ) and has therefore been considered the most promising for use in caries prevention [Zuerlein et al., 1999]. However, the lower absorption of the 10.6- m wavelength results in a higher penetration depth and can therefore affect a thicker enamel layer. For this rea- son, it has been suggested that the caries-preventive effect obtained with 10.6 m could be longer-lasting [Fox et al., 1992]. Furthermore, the most recent studies have demon- strated that the irradiation of dentin with a 9.3- m CO 2 laser failed to show any statistically significant increase in acid resistance [Le et al., 2008], whereas a continuous- wave 10.6- m CO 2 laser was able to decrease the acid dis- solution rate at higher power settings [Featherstone et al., 2008]. Therefore, it may be possible that the 10.6- m Key Words Bovine enamel  Caries prevention  CO 2 laser  Demineralisation Abstract Although CO 2 laser irradiation can decrease enamel demin- eralisation, it has still not been clarified which laser wave- length and which irradiation conditions represent the opti- mum parameters for application as preventive treatment. The aim of the present explorative study was to find low- fluence CO 2 laser (  = 10.6 m) parameters resulting in a maximum caries-preventive effect with the least thermal damage. Different laser parameters were systematically evaluated in 3 steps. In the first experiment, 5 fluences of 0.1, 0.3, 0.4, 0.5 and 0.6 J/cm 2 , combined with high repetition rates and 10 s pulse duration, were chosen for the experi- ments. In a second experiment, the influence of different pulse durations (5, 10, 20, 30 and 50 s) on the demineralisa- tion of dental enamel was assessed. Finally, 3 different irra- diation times (2, 5 and 9 s) were tested in a third experiment. In total, 276 bovine enamel blocks were used for the experi- ments. An 8-day pH-cycling regime was performed after the laser treatment. Demineralisation was assessed by lesion depth measurements with a polarised light microscope, and morphological changes were assessed with a scanning elec- tron microscope. Irradiation with 0.3 J/cm 2 , 5 s, 226 Hz for Received: September 8, 2008 Accepted after revision: February 18, 2009 Published online: May 8, 2009 Dr. Marcella Esteves-Oliveira Department of Conservative Dentistry, Periodontology and Preventive Dentistry RWTH Aachen University, Pauwelsstrasse 30 DE–52074 Aachen (Germany) Tel. +49 241 808 8111, Fax +49 241 808 2468, E-Mail marcella@usp.br © 2009 S. Karger AG, Basel 0008–6568/09/0434–0261$26.00/0 Accessible online at: www.karger.com/cre