Statement of the Problem: Despite its popularity as a denture-base material, poly-methyl methacrylate exhibits inherently low resistance to impact and fatigue failure. This is reflected in the analyses of the prevalence of denture fracture which suggests that prosthesis failure remains an unsolved problem. Consequently, various approaches to improve the physical and mechanical properties of denture-base polymers have been proposed. These include incorporation of solid metal forms and various types of fibers to provide reinforcement to fracture prone areas. In recent years there has been considerable interest in glass fiber reinforcement of polymeric denture resins. Partial fiber reinforcement using glass fiber has been shown to improve the mechanical properties of removable prostheses. However, adequate impregnation of fibers often requires the use of excessive methyl methacrylate monomer which has a deleterious effect on the mechanical properties of the fiber composite material. Purpose: The aim of the present study was to determine the effect of glass fiber polysulphone composite reinforcement on the flexural characteristics of two commonly used denture-base polymers. Materials and methods: Prefabricated E-glass fiber polysulphone composite rods, ± 3mm in diameter, with a continuous, unidirectional, non-silanized fiber concentration of ± 55 vol %, were employed as strengtheners. The reinforcement was incorporated axial to the neutral axis in standardized cylindrical heat polymerizing conventional and high impact resin test specimens 6mm in diameter and 28mm in length. The two reinforced pattern groups (n = 10) were compared with unreinforced resin control groups. A three point loading test was performed in air after storage of the specimens in water at 37°C for a period of 8 weeks. The following values were measured : flexural modulus and flexural strength. The obtained data were subjected to relevant statistical analysis. Results: The flexural modulus of the glass fiber polysulphone reinforcement was 14,106 MPa and the flexural strength 546.6 MPa. The flexural modulus of conventional denture-base resin was 1746 MPa, reinforcement increased it to 2328 MPa, and the flexural strength increased from 164 MPa to 209 MPa. The flexural modulus of high impact polymer was 1684 MPa and reinforcement increased it to 2067 MPa. The flexural strength was increased from 171 MPa to 242 MPa with reinforcement. Statistical analysis using t test showed that reinforcement affected the flexural modulus and flexural strength of polymer brands (p < : 05). Conclusion: Novel glass fiber polysulphone composite reinforcement may considerably enhance the flexural properties of multi phase denture-base polymers.
Dissertation (MSc (Prosthetic Dentistry))--University of Pretoria, 2005.