THE EFFECT OF TWO PACKING TECHNIQUES ON ADAPTATION OF RESIN DENTURE BASE MATERIALS

Abstract

Background: Acrylic resin denture bases undergo dimensional changes during polymerization. Injection molding techniques are reported to reduce these changes and thereby improve physical properties and adaptation of denture bases. The aim of this study was to compare denture base adaptation processed by conventional and injection-molding techniques. Materials and Methods: Twenty one accurate denture bases with the same dimension were fabricated and divided into three groups. For the first group, seven polymethyl methacrylate denture bases were made using conventional compression moulding technique and for the other two groups, two different injection moulding units were used to produce seven polyamide bases (thermo-plasticized) and seven polymethyl-methacrylate (PMMA) bases (themo-polymerized). The adaptation accuracy was examined using universal measuring microscope. The gap between the resin base and stone cast was measured at posterior palatal area at five points, corresponding to the right and left residual ridge crests, the midline, and the right and left marginal limits of the flanges. Results: Injection molded bases showed significant lower total gap scores at the crest and the palate compared to the conventional compression molded ones. However, there was no statistically significant difference between both groups at the vestibular gap. Injection molded polyamide resin denture bases showed significant difference compared to PMMA injected molded ones. Conclusion: Injection moulded polyamide resin has superior dimensional accuracy and adaptation compared to conventional pressure packed or injection moulded PMMA resin.