Influence of Heating Rates and Residual Monomer on Dimensional Changes of Acrylic Resin Denture Base

Abstract

Background: Most of spaces between the denture base and master cast produced by shrinkage of the base material during polymerization and by the difference in coefficient of thermal expansion of the cast and acrylic resin. The aim of this study is to evaluate the effect of the different heating rates and the presence of residual monomer on the accuracy different curing denture base by recording the gap space between the cast and the denture
Materials and methods: 18 maxillary edentulous stone cast were prepared then divided into three main groups, denture bases were constructed. In Group A, using Biostar plates (free of monomer) in the pressure champers. In group B, using short curing cycle while group C, using long curing cycle . The gap space between the cast and denture base was recorded using traveling microscope measuring device.
Results: Biostar curing resin (group A) showed significantly the highest dimensional changes among groups (short and long curing resins). There was no significant difference between group B ( short curing resin) and group C (long curing resin). The lowest gap space values were obtained in long curing resin. All samples showed maximum discrepancy in mid palatal reign and minimum dimensional changes at the crest of ridge. Minimum gap space values were shown in the canine reign for record bases cured with short and long curing cycles, while minimum gap space values were shown in the posterior palatal seal for record base cured with Biostar machine.
Conclusion: The dimensional changes of record bases mainly depend on the amount of heat applied during processing rather than the amount of residual monomer. Greater distortion was shown in record base processed by Biostar machine (Free of monomer), while the least distortion in record base processed by long curing cycle. All samples showed maximum discrepancy in the mid palatal region and minimum dimensional changes at the crest of ridge.