Influence of the incorporation of sodium trimetafosfate nanoparticles associated or not with chlorhexidine on the microbiological, physical-mechanical and enamel demineralization reduction properties of glass ionomer cement

Objectives: The aim was to evaluate the influence of the association of sodium trimetaphosphate nanoparticles (TMP) and chlorhexidine (CHX) on the microbiological, physical-mechanical and enamel demineralization reduction of glass ionomer cement (GIC)
Methods: Nine groups of the study were defined: control-GIC Fuji LII; GIC+ 1.25% CHX; GIC + 2.5% CHX; GIC + 7%TMP; GIC+ 1.25% CHX + 7%TMP; GIC + 2.5% CHX + 7%TMP; GIC+ 14%TMP; GIC + 1.25% CHX + 14%TMP; GIC+ 2.5% CHX + 14% TMP. The antimicrobial activity was determined by agar diffusion test against: Streptococcus mutans, Lactobacillus acidophilus, Actinomyces israelii and Candida albicans. GIC specimens were prepared using specific stainless steel molds in order to evaluate the following physical-mechanical properties for each material group: compressive and diametral tensile strength and superficial hardness. Eighty enamel blocks were prepared from bovine incisors and selected through the initial surface hardness test (SH1). GIC specimens were adjusted to the enamel blocks and submitted to pH-cyclings. After that, final superficial hardness (SH2) was determined in order to obtain the percentage of superficial hardness loss (%SHL) and observe the capacity of the materials in reducing enamel demineralization. Data were submitted to ANOVA and Bonferroni or Student-Newman-Keuls statistical tests, considering p≤0.05.
Results: The results showed that the addition of chlorhexidine increased the antimicrobial activity of GIC for all groups. The physical-mechanical properties of GIC, especially compressive strength, were jeopardized by the association of CHX and TMP after 24h of the specimen’s preparation, however, after 7 days, improvements on these properties were observed. Considering superficial hardness analysis after pH-cycling, groups containing 14% TMP, regardless of the CHX concentration, have the lowest superficial hardness loss.
Conclusions: It was concluded that the GIC containing 1.25% CHX and 14%TMP presented the most promising results, presenting positive effect on the demineralization, increasing antimicrobial activity, with minimal interference on the physical-mechanical properties.