Preparation of new low viscosity urethane dimethacrylates for dental composites

Abstract

Urethane-based polymers are very biocompatible in many biomedical applications. This study reports the synthesis of new low viscosity urethane dimethacrylates and evaluation of the formed composites. New urethane dimethacrylates were synthesized and formulated to form the composites. Compressive strength was used as a primary tool to evaluate the mechanical property. Water sorption, solubility, degree of conversion, flexural strengths and shrinkage were also investigated. It was found that liquid urethane dimethacrylates could be synthesized by derivatizing isocyanates with asymmetrical methacrylates. By eliminating diluent triethylene glycol dimethacrylate, the new urethane dimethacrylate-composed composites showed significantly higher modulus, lower water sorption, lower solubility and lower shrinkage, as compared to commercial BisGMA- and UDMA-based ones.     

Synthesis and characterization of new dimethacrylate monomer and its application in dental resin

In this study, a dimethacrylate monomer, 1,4-Bis[2-(4-(2′-hydroxy-3′-methacryloyloxy-propoxy)phenyl)-2propyl]benzene (BMPPB) was synthesized to replace 2,2-bis[4-(2′-hydroxyl-3′-methacryloyloxy-propoxy)phenyl]propane (Bis-GMA) as one component of dental restorative materials. The structure of BMPPB and its intermediate product 1,4-bis[2-(4-(oxiranylmethoxy)phenyl)-2propyl]benzene (BOPPB) were confirmed by Fourier transform infrared (FTIR) spectroscopy, proton nuclear magnetic resonance spectroscopy (¹H-NMR), and elemental analysis. In order to evaluate the possibility of replacing Bis-GMA with BMPPB in dental resin, double bond conversion (DC), polymerization shrinkage, contact angle, water sorption (WS) and solubility (SL), and flexural strength (FS) and modulus of BMPPB/tri(ethylene glycol)dimethacrylate (TEGDMA) (50/50?wt) resin system and Bis-GMA/BMPPB/TEGDMA (25/25/50?wt) resin system were studied. Commercially used Bis-GMA/TEGDMA (50/50?wt) dental resin system was used as reference. The results showed that BMPPB-contained copolymer had higher DC, higher WS and SL than the copolymer that only contained Bis-GMA (p?<?0.05). All of the copolymers had nearly the same contact angle (p?>?0.05). BMPPB/TEGDMA resin system had lower polymerization shrinkage, higher FS and modulus (p?<?0.05) than Bis-GMA/TEGDMA resin system. There was no significant difference on polymerization shrinkage, FS and modulus (p?>?0.05) between Bis-GMA/BMPPB/TEGDMA resin system and Bis-GMA/TEGDMA resin system. Before and after water immersion, both FS and modulus of every copolymer did not change significantly (p?>?0.05). Therefore, BMPPB had potential to be used to replace Bis-GMA as base resin in dental restorative materials, but many studies should be undertaken further.     

On the design of dental resin-based composites: a micromechanical approach

Adhesive resin-based restorative materials have the potential to considerably strengthen teeth and offer more economically viable alternatives to traditional materials such as gold, amalgam or ceramics. Other advantages are direct and immediate placement and the elimination of the use of mercury. However, polymerization shrinkage during curing of an adhesive restoration and mismatch in mechanical properties can lead to the initiation and development of interfacial defects. These defects could have a detrimental effect on the longevity of the restored tooth. The current study is focused on some design issues of resin-based composites affecting the longevity of the tooth-restoration interface. The theoretical approach is based on self-consistent micromechanical modelling that takes into account the effect of the material properties, volume concentration of the dispersed particle phase as well as the shape of these particles on the overall thermomechanical properties of the composite. Results obtained for resin-based composites reinforced with spherical, disc and short fibre particles highlight the advantages of disc shaped and short fibre particles.     

Static and dynamic moduli of posterior dental resin composites under compressive loading

Dental resin composites are commonly used as restorative materials for dental treatment. To comprehend the static and dynamic moduli of dental resin composites, we investigated the mechanical behaviors of resin composites under static and dynamic loading conditions. Four commercially available resin composites for posterior restorations were evaluated. The percentages, by weight, of inorganic fillers of resin composites were examined by the ashing technique. The static compressive tests were undertaken with a constant loading speed of 1.0 mm/min using a computer-controlled INSTRON testing machine. The dynamic properties of composites were determined using the split Hopkinson pressure bar (SHPB) technique. When inorganic filler content was increased, a remarkable increase in the static modulus and dynamic modulus were observed. Furthermore, there was a strong relationship between the static modulus and dynamic modulus (r²=0.947). The SHPB technique clearly demonstrated the dynamic properties of composites, and was a useful technique for determining the mechanical behavior of composites under dynamic compressive loading.