Validity-Reproducibility of QLF on Occlusal Caries under Clear Sealants

Sealants are a very effective caries preventive and management strategy, but some dentists are still reluctant to use them. The main concerns expressed are the possibility of sealing active caries and the difficulty of detecting caries under the sealant. Objectives: The aims of this in vitro study were to evaluate the severity of dental caries under a clear sealant using quantitative light fluorescence (QLF), and to determine if this evaluation was affected by aging, sealant thickness and surface roughness from toothbrush abrasion. Methods: One hundred human molars, with a range from sound to small cavitated occlusal caries lesions (0-4 ICDAS II criteria code), were selected by visual inspection by 3 trained examiners. Teeth were mounted on Plexiglas rods, and randomly and blindly evaluated using radiographs and QLF before sealant placement. Teeth were then sealed (Helioseal Clear Chroma sealant; Ivoclar Vivadent), a second QLF image taken, and were divided into four groups: Group 1 received no additional treatment (control); Group 2 was aged by thermocycling (2,500 cycles); Group 3 was subjected to toothbrush abrasion (40,000 strokes under a 250g tension); and Group 4 had a second layer of sealant placed. A third QLF image was taken and QLF measurements [fluorescence loss in the lesion (ΔF); size of the lesion (mm²), and ΔQ (mm² x ΔF)] were obtained. In addition, Diagnodent readings were obtained for Group 1. Results: Before and after sealant placement QLF was able to significantly (p<0.05) differentiate all ICDAS severity scores, except 1 and 2 (0 < 1&2 < 3 < 4). However, after sealant placement, lesions were consistently significantly less fluorescent, respective of ICDAS severity category. After sealant placement there were strong correlations between ICDAS and Diagnodent (r=0.71) and between Diagnodent and QLF (r=0.81). However, there were no significant differences between groups for QLF readings. Conclusion: QLF and Diagnodent were able to evaluate occlusal caries under clear sealants. The ability of the QLF to detect and differentiate between caries lesions of varying severity was not affected under the conditions of this study by sealant thickness, aging and abrasion.