MECHANICAL AND TRIBOLOGICAL PROPERTIES OF DENTAL COMPOSITE RESIN

Composites resin is extensively applied in dental restorative materials due to their easy operating performance and lower toxicity. The major factors influencing the clinical longevity of composites resin are discussed. The median longevity of composites resin restorations may be less than 8 years. To avoid the early failure, it is necessary to develop the mechanical and tribological properties of dental composite resin. It was found that to obtain higher compressive strength and hardness for the composite resin, the gradually strong mode of light curing should be utilized. The compressive strength was improved by increasing the curing time from 20 to 40 seconds. Besides, strong curing mode for 80 seconds gave the highest Shore hardness. It is essential to apply proper combinations of light intensity and curing time to enhance the mechanical properties of composite resin. Friction coefficient decreased with increasing curing time. In addition, nanoparticles and nanofibers as filling materials controlled the friction coefficient and provided favourable clinical performance in restorations by improving the biocompatibility and antibacterial activity. High curing times gave high wear resistance. Filling composite resin by silicon carbide (SiC) and titanium oxide (TiO2) developed wear resistance. Pulsed curing light showed lower fiction and wear compared to continuous one. Composite resin cured in two and three layers treated by continuous curing, displayed relatively lower wear rather than bulk-fill. It is recommended to combine both the curing mode and layering technique together to get favourable longevity of composite restorations by getting proper polymerization. The thickness of 2 mm is recommended to get the best the mechanical properties. The voltage generated from the sliding of composite resin on teeth showed higher values for pulsed light cured specimens than that observed from specimens treated by continuous light, where water wet sliding displayed higher voltage. Sliding of composite resin on bovine teeth showed that light pulsed cured specimens generated higher voltage than that measured for continuously cured ones. It seems that pulsed curing allowed longer time during curing process that facilitates the free monomers to be linked to other ones, forms longer polymer chains and increases the degree of polymerization.