In vitro study of the effect of a pulsed 10.6μm CO 2 laser and fluoride on the reduction of carious lesions progression in bovine root dentin

Abstract

The aim of the present study was to evaluate the combined in vitro effects a pulsed 10.6 μm CO 2 laser and fluoride on the reduction of carious lesion progression in root dentin. Sixty five slabs of previously demineralized bovine root dentin were assigned into five groups (n=13): control (no treatment), acidulated phosphate fluoride gel 1.23% (FFA), CO 2 Laser (L), FFA+L, L+FFA. The lasered groups were irradiated with 4.0J/cm2. After a 7 day pH cycling regime, the knoop hardness number (KHN) was determined by cross-sectional microhardness testing (5g, 5s, 10-60 μm, 10 μm interval). The data was analyzed by ANOVA and Student's t-test (α= 0.05). A significant interaction between KHN and the indentation depths was found (p<0.05). At 10-20 μm, FFA+L (KHN:12.12±0.95/13.07±1.03) and FFA (KHN:12.86±4.54/12.60±3.93) inhibited caries progression when compared to control group (KHN:8.76±0.95/9.50±1.03) (p 0.05). At 30 μm, the KHN was significantly higher than the control only in the FFA group (KHN:15.35±1.16). At 40 μm, the groups FFA (KHN: 15.87±3.76), L (KHN: 15.57±5.71) and L+FFA (KHN:15.50±5.08) were capable of significantly inhibiting caries progression, however they did not differ each other (p>0.05). At depths of 50-60 μm, only group L (KHN:17.05±1.29/18.26±1.30) differed statistically from the control (KHN:13.43±1.24/13.81±1.25), but not from the other groups. In conclusion, CO 2 laser alone was able to inhibit caries progression in the deepest layers. However, no synergistic effect was obtained when CO 2 laser irradiation and FFA application and were combined.