FIBER-REINFORCED THERMOPLASTIC COMPOSITES FOR DENTISTRY .1. HYDROLYTIC STABILITY OF THE INTERFACE

Clinical implementation of fibre-reinforced composites (FRCs) for treatment of misaligned teeth requires a stability of the material under stress in a moist environment. The performance of the material is strongly dependent on its resistance to hydrolytic deterioration of the components. Of particular concern are the quality and durability of the interfaces between the fibres and the matrix. Scanning electron microscopy (SEM) was utilized to evaluate qualitatively the effect of water immersion on the interfaces between constituents in a variety of E-glass fibre-reinforced thermoplastics. A particular series of organosilane-coated fibres embedded in polycarbonate (PC) were chosen for further quantitative study of the residual shear strength of the interfaces using an embedded-single-fibre test. Annealed PC and maleated polypropylene (MPP) reinforced with bare E-glass fibres have an appropriate combination of mechanical properties and environmental stability for potential orthodontic applications. The usual sizing agents used for commercial E-glass fibres interfere with the bonding of the fibres to the matrix and the usual silane treatments used to promote bonding could lead to problems of hydrolytic stability under extreme conditions of stress and moisture.