Antimicrobial activity of a remineralizing paste containing Strontium doped Nano hydroxyapatite (Sr-nHAp) with Non Collagenous Protein (NCP) analogue Chitosan – An in vitro study

Dental caries is an infectious multifactorial disease. Biomimetic remineralisation of non-infected carious dentine helps in retaining tissues to a maximum degree during vital pulp treatment. However micro gaps and residual bacteria below restorations lead to microleakage, degradation of tooth structure and secondary caries. Remineralizing agent with anti-bacterial efficacy would help contain secondary caries and its sequelae. The aim of the study was to evaluate the antimicrobial activity of remineralizing paste containing Strontium doped Nano hydroxyapatite (Sr-nHAp) with Non Collagenous Protein (NCP) analogue, Chitosan. In this study dentin slabs, 200 µm thick obtained from freshly extracted premolars were demineralised and inoculated with Streptococcus mutans to simulate artificial carious lesion. The specimens were divided in to six groups based on the reminerlising regimen, Group 1–10 wt%Sr-nHAp, Group 2–20 wt%Sr-nHAp, Group 3–10 wt%Sr-nHAp + Chitosan and Group 4–20 wt%Sr-nHAp + Chitosan, Group 5 Positive control – Calcium hydroxide and Group 6, negative control, no treatment. The dentin specimens were homogenised and assessment of bactericidal effects was done by counting the number of viable bacteria after 48 h of incubation. Agar well diffusion test was performed to measure the zone of inhibition. Results were tabulated and analysed statistically using, ANOVA and Post – hoc Bonferroni tests (P = 0.05). All experimental groups except Group 1, exhibited antibacterial properties observed by Zone of Inhibition and reduced colony forming units. Antibacterial efficacy of the remineralizing paste was enhanced by the addition of Chitosan and its antimicrobial efficacy was comparable to calcium hydroxide.