Antimicrobial agents in dental restorative materials: Effect on polymerization, short-term drug release and biological impact.

With the aim to design bioactive dental restorative material, the present study investigated the influence of the antimicrobial agents chlorhexidine diacetate (CHX) and octinidine (di)hydrochloride (ODH) when incorporated in two different materials. Selected parameters were polymerization enthalpy, short-term drug release, and the effect on Streptococcus mutans as well as human gingival fibroblasts. Samples were made by mixing a nano-hybrid ormocer (O) and a methacrylate-based nano-hybrid composite (C), each with a mass fraction of 2% CHX or ODH. Release profiles and concentrations of active agents from the resins were assessed, and the cell proliferation of human gingival fibroblasts as well as Streptococcus mutans cultured with the eluates were evaluated. The influence on polymerization was assessed by means of differential scanning calorimetry. Both drugs, especially ODH, showed a decreasing effect on polymerization enthalpies associated with a lowered crosslinking degree. At the same time ODH appeared to be released more persistently than CHX. Moreover, ODH was more efficient with regard to bacteria growth inhibition but also more cytotoxic in terms of reduction of cell viability. ODH is deemed more appropriate for application in a dental resin-based drug delivery system, because of the more persistent drug release than seen for CHX.

Antimicrobial agents in dental restorative materials: Effect on long-term drug release and material properties.

The present study reports on the long-term drug release and mechanical properties of bioactive dental filling materials based on chlorhexidine diacetate (CHX) or octinidine (di)hydrochloride (ODH) incorporated in a composite based on dimethacrylates or an ormocer. CHX or ODH were added to a nano-hybrid ormocer (O) and a nano-hybrid composite (C) with the amount of 2 wt% to achieve four matrix-drug combinations: O-CHX, O-ODH, C-CHX, and C-ODH. Drug extraction and release were measured using high-performance liquid chromatography with diode-array detection (HPLC-DAD), while drug distribution was assessed by using energy dispersive X-ray spectroscopy (EDX). Drug release in water at 37°C was observed over 87 d. To determine the material properties, the water absorption, water solubility, flexural strength and hardness were measured and compared to the reference materials. Persistent drug release over 87 d was observed for both ODH-based systems and both ormocer-systems, with the longest duration of activity seen for the O-ODH combination. Persistent drug release was achieved via the loosening of the polymer network indicated via decreasing polymerization enthalpies, enhanced water absorption, and water solubility. As a consequence, the flexural strengths of the materials were reduced. However, surface hardness was hardly reduced. ODH seems to be more adequate than CHX for the design of bioactive dental filling materials based on nano-hybrid ormocer and composites.