HEAT TREATMENT OF POLYMETHYL METHACRYLATE DENTURE BASE

It is known that fracture of the polymethyl methacrylate (PMMA) denture base is critical clinical problems. It is essential to develop the mechanical properties of the denture base. One of the methods to improve the mechanical properties is the heat treatment. Heat treatment includes annealing, normalizing and quenching. The influence of heat treatment of PMMA denture on the friction and wear is studied in the present work. PMMA has been heated up to 80 °C for 4 hours then air, water and furnace cooled. Adhesive and scratch wear tests have been performed to investigate the wear resistance of the heat treated PMMA.It was found that annealed PMMA showed the lowest values of friction coefficient, while quenched PMMA in water displayed the lowest values. Besides, annealed PMMA showed the lowest wear values, where annealing enhanced the crystallization of PMMA so that the resistance to wear increased. When the crystallinity of the polymer increases, the strength and brittleness increases. Annealing of PMMA increases crystallinity and decreases plasticity. Friction and wear of water quenched PMMA showed the highest values due to the hardness decrease.