Caries-like lesion formation around Class V preparations restored with fluoride-releasing sealant, glass ionomer and conventional sealant materials was evaluated with polarized light microscopy following lesion initiation and progression periods. Significant differences (P < 0.05) were found among the three treatment groups for mean surface lesion depth following lesion initiation and progression and between the conventional sealant and fluoride-containing material groups for incremental increase in surface lesion depth following lesion progression. Surface lesion depths were significantly reduced in both the fluoride-releasing sealant and glass ionomer groups when compared with the conventional sealant group. The glass ionomer material provided the greatest degree of caries protection at the enamel-restorative interface and had the least number of wall lesions (7.5%); in contrast, the conventional sealant group had the greatest number of wall lesions (17.5%). The incorporation of fluoride from a dental material into adjacent tooth structure may provide enhanced resistance to caries initiation and progression.