Action Spectrum of Erosion Prevention Using Low Power Laser Energy

Erosion is the loss of dental hard tissues, from an acidic challenge, resulting in loss of tooth structure by dissolution and hypersensitivity to environmental stimuli. LAF therapy with 488 nm laser energy has been shown previously to increase the resistance of human enamel and dentine to acid dissolution in laboratory models of dental caries. Objective: The aims of this study were to investigate the action spectrum of laser-activated fluoride (LAF) therapy on tooth enamel, and any associated intra-pulpal temperature change. An in-vitro model of erosion of human dental enamel was used to assess whether LAF therapy provides enhanced fluoride protection to enamel. Methods: Buccal and lingual surfaces of extracted sound, molar and premolar teeth were used to prepare matched pairs of enamel slabs (N=10 per treatment group). After application of 1.23% neutral sodium fluoride gel, slab surfaces were lased (energy density 15 J/cm-2; spot size 5 mm, wavelength 488, 514.5, 532, 633, 670, 830 or 1064 nm), then exposed to an erosive challenge (1.0 M HCl for 5 min). The Vicker’s Hardness Number (VHN) was recorded before fluoride gel application and again following acid challenge. Negative controls did not receive laser exposure. Results: All wavelengths of laser light examined provided an effective LAF effect, compared with the unlased negative control surfaces. Visible red wavelengths (633 and 670 nm) provided the greatest effect. ConclusionS: From these findings, we conclude that the action spectrum of the LAF effect extends across the visible spectrum, and peaks in the 633 nm wavelength region.