Tooth Micro-hardness Changes After Applying Bioactive Glass-containing, Anti-microbial Sealants

The AAPD recommends placement of dental pit and fissure sealants on surfaces that are high risk or that already exhibit incipient carious lesions. Protection provided by sealants may be enhanced by the addition of ion-releasing, anti-microbial filler particles of bioactive glass.

Objective: We prepared novel dental pit and fissure sealant materials containing bioactive glass (BAG) fillers and tested their ability to prevent tooth demineralization in a bacterial broth.

Method: Two types of BAG were synthesized in our lab: BAG1 (61 wt% silica - 31 wt% calcia - 4 wt% phosphate - 4 wt% flouride); and BAG2 (81 wt% silica - 11 wt% calcia - 4 wt% phosphate - 4 wt% flouride). Ultraseal XT (USXT) resin without filler was supplied by the manufacturer (Ultradent Products, Inc. South Jordan, UT). BAGs were individually incorporated into the resin (25 wt%) and provided handling properties similar to USXT. Caries-free teeth (n=5 each) were randomly assigned to three groups (BAG1-sealant, BAG2-sealant,or USXT) and sealants were placed by the same practitioner. Acid-resistant nail polish was used to cover half of the tooth surface. Teeth were immersed in a bacterial culture system of sucrose-rich brain-heart infusion (BHI) media containing Streptococcus mutans strain #25175, an acid-producing microbe and incubated at 37˚C, 5%CO₂; media was changed every other day. Bacterial growth was confirmed throughout the test period. At two weeks, teeth were sectioned sagitally and microhardness testing compared changes in hardness as a function of location on the tooth.

Result: Overall, the BAG2-sealant samples were significantly (up to 20%) harder than the BAG1-sealant or USXT samples. Areas directly adjacent to the BAG2-sealant were up to 40% harder than the original tooth surface. (ANOVA/Tukey's; α=0.05).

Conclusion: The inclusion of anti-bacterial, ion-releasing BAG as a filler component results in a harder tooth that may be better able to resist demineralization.