Glass ionomer cements with milled, dry chlorhexidine hexametaphosphate filler particles to provide long-term antimicrobial properties with recharge capacity

•Milled, dry chlorhexidine hexametaphosphate (CHX-HMP) was incorporated into a GIC.•CHX release was dose-dependent and sustained for at least 660days.•GICs could be recharged with CHX and CHX-HMP.•1% CHX-HMP did not affect compressive, tensile or biaxial flexural strength.•CHX-HMP GICs inhibited growth of cariogenic microorganisms in an agar diffusion model. Glass ionomer cements (GICs) are a versatile material, offering the opportunity for ion exchange with the oral environment. The aim of this study was to develop a GIC that delivers a controlled, rechargeable dose of chlorhexidine (CHX) over an extended period without compromising mechanical properties. GICs were supplemented with finely milled particles of chlorhexidine hexametaphosphate (CHX-HMP). CHX release into artificial saliva was measured over 660 days, and recharge with CHX and CHX-HMP was investigated. Mechanical properties were investigated, and an agar diffusion test was carried out to assess antimicrobial properties using Streptococcus mutans and Scardovia wiggsiae. Dose-dependent CHX release was observed, and this was ongoing at 660 days. Compared with related studies of GICs containing CHX-HMP, the fine, dry particles resulted in fewer adverse effects on mechanical properties, including tensile, compressive and biaxial flexural strength, with 1% CHX-HMP GICs indistinguishable from control specimens. The GICs could be recharged with CHX using both a conventional CHX digluconate solution comparable to commercial mouthrinses, and a suspension of CHX-HMP of equivalent concentration. Recharging with CHX digluconate increased subsequent CHX release by 50% compared with no recharge, and recharging with CHX-HMP increased subsequent CHX release by 100% compared with no recharge. The GICs inhibited growth of St. mutans and Sc. wiggsiae in a simple agar diffusion model. These materials, which provide sustained CHX release over clinically relevant timescales, may find application as a restorative material intended to inhibit secondary caries as well as in temporary restorations and fissure sealants.