Water sorption and colour stability of composites containing the antibacterial monomer MDPB

Objectives: Previously, we have reported that composites incorporating the newly developed antibacterial monomer methacryloyloxydodecylpyridinium brom ide (MDPB) inhibited bacterial growth and plaque accumulation on their surf aces without releasing antibacterial components, and that the antibacterial effect was not lost even after ageing in a wet environment for a long peri od. The purpose of this study was to investigate the influence of the incor poration of MDPB on the water sorption characteristic and colour stability of Bis-GMA based composites. Methods: Cured disc-shaped specimens of composites containing 0.4% or 0.5% MDPB were fabricated, and water uptake, the diffusion coefficient and the s urface contact angle for water were determined. Discoloration of MDPB-conta ining composites was evaluated after immersion in water at 37 degrees C and 60 degrees C for 4 weeks and compared with that of the control composite w ithout MDPB. Results: There were no significant differences in water uptake, diffusion c oefficient and contact angle between the control and MDPB-containing compos ites. Although composites incorporating MDPB showed greater discoloration t han the control when maintained at 37 degrees C, no difference was found af ter 4 weeks of immersion in water at 60 degrees C. Conclusions: Incorporation of small amounts of the antibacterial monomer MD PB showed no influence on the water sorption characteristic and affected a little the colour stability of the Bis-GMA based composite, causing rapid d iscoloration (C) 1999 Elsevier Science Ltd. All rights reserved.