FRICTIONAL BEHAVIOR OF THE SLIDING OF COMPOSITE RESIN ON TEETH

Composite resins are considered the major material of dental restorations. due to their superior aesthetics and conservative application. The behavior of the restorations is affected by curing method such as continuous and pulsed modes. The test specimens have been prepared by bulk-fill and incremental layering.The present study investigates the effect of filling and curing techniques on frictional properties and electrification of the tested composite resin. Sliding tests were performed at 8, 10 and 12 N load to simulate oral masticatory forces. Because the friction of materials is accompanied by electrification, it necessary to measure the voltage generated from the sliding of composites resin on the teeth.It was revealed that specimens of three layers displayed the highest friction coefficient followed by specimens of two layers and bulk-fill, while specimens of four layers showed lowest friction. Besides, water wet sliding displayed lower values of friction coefficient with the same trend compared to the dry sliding. Specimens treated by pulsed light curing gave relatively higher friction displayed by specimens of three layers while bulk-fill showed the lowest friction of higher values than that shown for specimens cured by continuous light. It was observed that pulsed treated specimens had higher hardness than continuous treated ones. It is recommended to increase the hardness of composite resin to increase friction to guarantee proper mastification.Specimens continuously light cured of two layers displayed the highest voltage in dry sliding. While, water wet surfaces showed relatively higher voltage than dry ones. Voltage generated from dry sliding of pulsed light cured specimens was higher than that observed from specimens treated by continuous light and water wet sliding displayed higher voltage values. It seems that in pulsed light curing, the monomers have the chance to be linked to other monomers forming longer polymer chains, increasing the degree of polymerization and modifying the toughness that increases the values of the generated voltage caused by the piezoelectric effect.