ABSTRACT
<p><b>OBJECTIVE</b>To compare the penetration abilities of resin infiltration into natural initial caries lesions with those of adhesive in vitro.</p><p><b>METHODS</b>Thirty-six extracted human molars and premolars showing proximal white spot lesions were selected. Teeth roots were removed, and the crowns were cut across the caries lesions perpendicular to the surface. Corresponding lesion halves were etched for 2 min with 15% hydrochloric acid gel and were subsequently treated with either adhesive or resin infiltration. Specimens were observed with confocal laser scanning microscopy (CLSM) in dual fluorescence mode. In confocal microscopic images, penetration depth (PD) and lesion depth (LD) were defined as the distance from the surface to the deepest point of red and green fluorescence, respectively. The penetration percentages (PP) were calculated.</p><p><b>RESULTS</b>At the same level of caries, mean maximum lesion LD were comparable for both lesion halves (P > 0.05). But mean maximum PD and PP of the resin infiltration were significantly higher than those of the adhesive (P < 0.01).</p><p><b>CONCLUSION</b>Penetration of enamel caries lesions is observed in the adhesive and the resin infiltration. But the resin infiltration is capable of penetrating almost completely into enamel parts of natural caries lesions.</p>