Effect of surface treatments on the mechanical properties and antimicrobial activity of desiccated glass ionomers

Objectives The purpose of this study was to evaluate the effect of various surface treatments on the mechanical properties and antibacterial activity of desiccated glass-ionomer (GI) and resin-modified glass-ionomer (RMGI) materials. Methods One hundred GI and RMGI specimens were fabricated in a mold, stored in 100% humidity for 24 h, placed in air to desiccate for 24 h, and then stored for one week in one of the five media [casein phosphopeptide–amorphous calcium phosphate (CPP–ACP), chlorhexidine (CHX), sodium fluoride (NaF), cetylpyridinium chloride (CPC), or 100% humidity (control)]. Fifty GI and RMGI specimens were tested in flexure to determine flexural strength and modulus, with the fragments used for Knoop hardness testing. The remaining 50 GI and RMGI specimens were covered with a suspension of Streptococcus mutans and incubated for 24 h. The bacterial suspension was removed and the specimens were washed. Sterile saline was added, vortex mixed, serially diluted, and plated. CFU/mLs were calculated after 3 days of incubation. Results Compared to the 100% humidity control group, surface treatment of the desiccated GI and RMGI materials had a variable effect on the mechanical properties. In general, NaF provided the greatest improvement in flexural strength and modulus. Surface treatment of the desiccated GI or RMGI specimens with CHX or CPC resulted in no growth of the S. mutans. NaF resulted in significantly lower CFU/mL than CPP–ACP, which was significantly lower than the control group. Significance Surface treatment with 5% NaF provides improved antimicrobial and strength properties of desiccated GI or RMGI materials.