Method: AgNPs were generated in situ in UltraSeal XT® Hydro™ (XT; Ultradent Products, Inc.) pit and fissure sealant using different concentrations of silver benzoate (AgBz; 0, 0.01, 0.05, 0.1, 0.25wt%) and Bis-GDMP (0, 2.5, 5, 7.5, 10wt%). Controls included XT and the same sealant formulated in-house (UT-Seal). Resins were tested for degree of cure (Rockwell15T hardness), color stability (digital colorimetry), mechanical properties (3-point bending), and in vitro Ag+ion release (atomic absorption spectrometry). The same groups without filler were also made to better determine effects of bis-GDMP on color.
Result: In general increasing bis-GDMP lightened color especially when filler was not present, with resins with 0.01-0.05% Ag and 10% bis-GDMP having comparable color to controls. Mechanical tests showed that XT and UT-Seal had similar hardness and moduli. However, XT had significantly higher ultimate transverse strength (UTS), probably due to the different methods of filler incorporation. In general, increasing bis-GDMP increased hardness and modulus, but not UTS. Also, low concentrations of Ag decreased UTS and high concentrations increased UTS. Ag+ion release was observed for all AgNP-loaded groups for up to 4 months with increase in AgBz concentration increasing release.
Conclusion: A novel antimicrobial pit and fissure sealant with in situ-generated AgNP was developed with comparable or greater mechanical properties than those of UT-Seal. The use of Bis-GDMP to control the color generated by the AgNPs was less effective than originally hypothesized when filler was present. Nonetheless, several non-filler groups had comparable color to controls, and our other work shows that color can be further reduced by adding bismuth oxychloride. In vitro antimicrobial activity is currently being assessed.