Effects of CO2 laser and fluorides application on root demineralization

Koichi Shinkai, DDS, PhDa and Shiro Suzuki, DDS, PhDb

aDepartment of Operative Dentistry, The Nippon Dental University School of Life Dentistry at Niigata, Niigata, Japan, and bDepartment of Prosthodontics, School of Dentistry, University of Alabama at Birmingham, AL, USA

Purpose: The effects of CO2 laser irradiation and fluoride application on the acid resistance of tooth root surfaces were evaluated.
Materials and Methods: A total of 35 extracted human premolar roots were completely coated with acid-resistant varnish except for a window (2×3 mm) on the proximal surface. The roots were assigned to one of seven treatment groups as follows: CO2 laser irradiation at 17 J/cm2 (Group 1); irradiation at 25 J/cm2 (Group 2); irradiation at 41 J/cm2 (Group 3); 200-minute soak in 0.05% NaF solution (Group 4); 50-minute soak in 0.2% NaF solution (Group 5); 5-minute application of 2.0% NaF solution (Group 6); and no treatment (control). The specimens were subjected to a 2-day pH-controlled cyclic demineralization/remineralization process. The lesion depth on each sample was measured using polarized-light microscopy.
Results: The lesions in groups 3, 4, 5, and 6 were significantly shallower than the lesions in the control specimens (p<0.01), but there were no significant differences between groups 1 and 2 and the control, or between groups 1, 2, 3, and 4 (p>0.05). The lesions in groups 5 and 6 were significantly shallower. Group 3 exhibited significantly reduced lesion depth compared to the control.
Conclusion: Fluoride application significantly improved the acid resistance of the root surface. CO2 laser irradiation at an energy density of 41 J/cm2 improved the acid resistance of the root surface, while CO2 laser irradiation at energy densities of 15 and 27 J/cm2 had no beneficial effect.
(Asian Pac J Dent 2014; 14: 1-6.)
Key Words: fluoride, laser, tooth demineralization/remineralization, tooth root