Inhibition of enamel mineral loss by fissure sealant: An in situ study

Objectives: This study evaluated the effect of fluoride and non-fluoride sealants on hardness decrease (HD) and marginal adaptation (MA) on enamel substrates after cariogenic challenge. Methods: Occlusal enamel blocks, from human third molars, were randomly divided into six groups (n = 12), according to occlusal fissures condition (S - sound; C - caries-like lesion; CF - caries-like lesion + topical fluoride) and sealants (F - FluroShield; H - Helioseal Clear Chroma). Lesion depths were 79.3 +/- 33.9 and 61.3 +/- 23.9 for C and CF groups, respectively. Sealants were placed on occlusal surface and stored at 100% humidity (37 degrees C; 24 h/d). HD was measured by cross-sectional microhardness analysis at the sealant margin distances: -1 (under sealant), 0 (sealant margin), 1, 2 (outer sealant). Sealant MA was observed by polarized light microscopy and scored according to: 0 - failure (no sealant MA or total sealant loss); 1 - success (sealant MA present). MA and HD were analysed by ANOVA-R and mixed model analysis, respectively. Results: For HD (Delta S), F values (6900.5 +/- 3686.6) were significantly lower than H values (8534.6 +/- 5375.3) regardless of enamel substrates and sealant margin distances. Significant differences were observed among sealant margin distances: -1 (5934.0 +/- 3282.6) < 0 (8701.5 +/- 6175.7) = 1 (8473.2 +/- 4299.4) = 2 (7761.5 +/- 4035.1), regardless of sealant and substrate. MA was similar for all groups (p >= 0.05). Conclusion: MA was not affected by sealant type or substrate condition, whereas enamel HD was favourably impacted by fluoride in the sealant. In addition, sealants were more effective as a physical barrier than as its chemical potency in reducing enamel HD. Clinical significance: Sealing with a fluoride material is a recommended procedure to prevent caries of occlusal permanent molars in high-caries-risk patients, even though those exhibiting white spot lesions, since the enamel hardness decrease when fluoride sealant was used in vitro. (C) 2012 Elsevier Ltd. All rights reserved.