The Study of the Properties of Three Kinds of Thermoplastic Material for Invisible Bracketless Appliance

摘要

The purpose of this experimental study were to research and compare the properties of three kinds of thermoplastic materials: thermoplastic polyurethane(TPU), polycarbonate (PC), poly (ethylene terephthalate) modified glycol (PETG), which were used in the preparation of invisible bracketless appliance. The experiment was performed at room temperature of 23°C, the transmittance and haze of three different thermoplastic materials with thickness of 0.8mm were tested, the weight of saliva absorption were researched, the yield stress, elongation at break and elastic modulus were measured before treatment and after stored in 37°C artificial saliva for two weeks, and their fracture surface were analyzed by scanning electron microscope (SEM). The results revealed that the transmittance of three kinds of thermoplastic materials is more than 80%, while the haze is less than 0.3%, that is to say, the three kinds of thermoplastic materials are all meeting the condition of invisibility for the preparation of invisible bracketless appliances. The weight of saliva absorption of three kinds thermoplastic materials increases firstly and then tends to a certain amount, and the weight of saliva absorption of TPU is the biggest. TPU has the highest yield stress and the smallest modulus of elasticity before and after stored in 37°C artificial saliva, and has high elongation at break and excellent toughness. It means TPU has the best comprehensive properties in the three kinds of thermoplastic materials and is best suitable for the preparation of invisible bracketless appliance.