Resistance of occlusal fissures to demineralization after loss of glass ionomer sealants in vitro.

Seventy-one caries-free human occlusal fissures were used for this study. Twenty-two fissures were sealed with a glass ionomer sealant (Fuji Ionomer Type III--G-C Dental Industrial Corp., Tokyo, Japan), 24 were widened with a diamond bur and sealed with the glass ionomer sealant, and 25 were left unsealed. After one week, the sealants were removed as completely as possible with a probe. All fissures were demineralized for seven weeks. Sections made from the fissures were examined with a polarizing microscope, and the depths of the fissure lesions were measured. The mean lesion depths for controls, sealed natural fissures, and sealed widened fissures were 143, 93, and 75 microns, respectively. A statistically significant difference was noted between the two experimental groups and the control group (no sealant). The results suggest that fissures sealed with glass ionomer are more resistant to demineralization than control fissures, even after macroscopic sealant loss. This may be the result of the combined effect of fluoride released by glass ionomer and residual material in the bottom of the fissures.