The antibacterial, cytotoxic, and flexural properties of a composite resin containing a quaternary ammonium monomer

Abstract

Statement of problem: The use of composite resin to restore teeth has increased substantially during the last decades. However, secondary caries and the fracture of restorations are the leading reasons for clinical restoration failure. Mechanically strong composite resins with caries-inhibition capabilities are needed. Although antibacterial dimethacrylate quaternary ammonium monomers have been synthesized, composite resin containing dimethacrylate quaternary ammonium monomers and glass fillers has rarely been reported.

Purpose: The purpose of this in vitro study was to evaluate the possibility of the clinical use of an experimental composite resin containing urethane dimethacrylate quaternary ammonium compound (UDMQA-12) by investigating its antibacterial activity, cytotoxicity, flexural strength, and flexural modulus.

Material and methods: Antibacterial activity against Streptococcus mutans was investigated by means of direct contact test. The antibacterial activity of specimens after water immersion and saliva treatment was also tested. These were compared with a commercially available composite resin, Z250, and a glass ionomer cement, Fuji VII. Effects of the eluent from the experimental composite resin on the metabolic activity of human dental pulp cells were quantified. Disks of 1 mm in thickness and 15 mm in diameter were used in the antibacterial and cytotoxic tests. Flexural strength and flexural modulus were measured with a 3-point bend test with bars of 2×2×25 mm. Three commercially available composite resins (Filtek Z250, G-aenial Anterior, and G-aenial Posterior) were used as controls in the flexural test.

Results: Bacterial growth was inhibited on the experimental composite resin. After water immersion or saliva treatment, the experimental composite resin showed significant antibacterial effect compared with the conventional composite resin (P<.05). No significant difference was found in cytotoxicity between the experimental composite resin and the conventional composite resin (P＞.05), and a significantly higher cytotoxicity was shown by glass ionomer cement compared with the experimental composite resin and the conventional composite resin (P<.05). The conventional composite resin had the highest flexural strength and flexural modulus (P<.05), followed by the experimental composite resin, then G-ænial Posterior and G-ænial Anterior.

Conclusions: The antibacterial experimental composite resin was biocompatible and had mechanical properties similar to those of some commercially available composite resins. It might, therefore, be useful in preventing the occurrence of secondary caries.