Reinforcement of polymethylmethacrylate (PMMA) resin with perforated metal plates

Abstract

Background: Full dentures show a high rate of fractures under clinical use. Therefore strengthening of the denture base is expected to be beneficial with respect to reducing the fracture risk. Preformed perforated thin metal plates seem to be a simple tool for reinforcement. Objective: To test the strengthening effect of perforated metal plates incorporated into a PMMA based resin as a function of the bonding strategy. Materials and Methods: Preformed gold plated stainless steel grid strengtheners were purchased, pressed flat and embedded in wax and processed as dentures using the Ivobase hybrid injection moldable material (Ivoclar Vivadent, Schaan, Liechtenstein). Prior to processing the surfaces were either not treated or treated with a primer (Monobond Plus, Ivoclar Vivadent, Schaan, Liechtenstein) and grit blasted and primed. They were then sectioned into beams for three point bending test. Resin beams of identical dimensions without reinforcement were used as control. Flexural strength and modulus were calculated based on the load to fracture determined by an Instron universal testing machine. The data were analyzed with ANOVA and Tukey's test. Results: Flexural strength: control beams fractured at 78.8 ± 5.9 MPa, while, with the exception of the grit blasted samples, the experimental groups showed significantly higher strength (97.2 respect. 95.4 MPa). Flexural Modulus: The control group yielded 2261.7 ± 261.4 MPa, while all experimental groups had a significantly higher modulus (3239.1-3952.4 MPa) The surface treatments did not show significant differences. Conclusions: The grid strengtheners tested had a significant effect on strengthening. Under the conditions of this study, surface priming did not increase the mechanical properties of the reinforced bars.