Abstract
Dental composites are commonly used restorative materials; however, secondary caries due to biofilm acids remains a major problem. The objectives of this study were (1) to develop a composite containing quaternary ammonium dimethacrylate (QADM), nanoparticles of silver (NAg), and nanoparticles of amorphous calcium phosphate (NACP), and (2) to conduct the first investigation of the mechanical properties, biofilm response and acid production vs water-ageing time from 1 day to 12 months. A 4 × 5 design was utilized, with four composites (NACP-QADM composite, NACP-NAg composite, NACP-QADM-NAg composite, and a commercial control composite), and five water-ageing time periods (1 day, and 3, 6, 9, and 12 months). After each water-ageing period, the mechanical properties of the resins were measured in a three-point flexure, and antibacterial properties were tested via a dental plaque biofilm model using human saliva as an inoculum. After 12 months of water-ageing, NACP-QADM-NAg had a flexural strength and elastic modulus matching those of the commercial control (P>0.1). Incorporation of QADM or NAg into the NACP composite greatly reduced biofilm viability, metabolic activity and acid production. A composite containing both QADM and NAg possessed a stronger antibacterial capability than one with QADM or NAg alone (P<0.05). The anti-biofilm activity was maintained after 12 months of water-ageing and showed no significant decrease with increasing time (P>0.1). In conclusion, the NACP-QADM-NAg composite decreased biofilm viability and lactic acid production, while matching the load-bearing capability of a commercial composite. There was no decrease in its antibacterial properties after 1 year of water-ageing. The durable antibacterial and mechanical properties indicate that NACP-QADM-NAg composites may be useful in dental restorations to combat caries.
Highlights
Dental caries is a prevalent worldwide problem,[1] and tooth cavity restorations cost the United States more than $46 billion annually.[2]
After water-ageing for 3, 6, 9, or 12 months, there was no noticeable difference in the biofilms compared with that at 1 day of water-ageing. These results indicate that the antibacterial activity of nanoparticles of amorphous calcium phosphate (NACP)+quaternary ammonium dimethacrylate (QADM), NACP+NAg, and NACP+QADM+NAg composites was durable and not lost during the water-ageing for 12 months
The biofilm metabolic activity was similar from 1 day to 12 months of water-ageing (P40.1), and the lactic acid production from 1 day to 12 months was not significantly changed over this period (Po0.05). These results demonstrate that incorporating QADM and NAg into the NACP composite a a a a a
Summary
Dental caries is a prevalent worldwide problem,[1] and tooth cavity restorations cost the United States more than $46 billion annually.[2] Resin composites are increasingly used as direct filling materials for tooth cavity restorations, because of their excellent aesthetics and improved load-bearing properties.[3,4,5,6,7,8] Extensive studies have significantly improved the microstructure, chemical composition, and physical and mechanical properties of resin composites.[9,10,11,12,13] dental resin composites tend to accumulate more biofilms/plaques than other restorative materials.[14,15] Previous studies have demonstrated that the two main challenges facing composite restorations are secondary caries and bulk fracture.[16] Replacing the failed restorations accounts for 50%–70% of all tooth cavity restorations performed.[17,18]
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