The Effect of Autoclave and Heat Polymerization Techniques of Internal Adaptation of Acrylic Resins

Abstract

Aim: Polymerization shrinkage of the resin and distortion of the denture base due to thermal stress is virtually unavoidable during the processing of dentuRes These adverse effects increase the gap between the denture base and underlying mucosa, resulting in an illfitting denture. A variety of methods have been used to evaluate the dimensional changes and/or adaptation accuracy of a denture base. This study compared the adaptation accuracy of maxillary complete denture bases processed using different polymerization techniques; conventional compression-molding technique and autoclave polymerization techniques. Material and Methods: 42 resin specimens were fabricated from three heat polymerizing denture base acrylics (Meliodent, Paladent, QC-20). The specimens were divided into six groups (n=7). Three of them were polymerized in a conventional water bath and other three were polymerized in autoclave. Internal adaptation was evaluated immediately after finishing by weighting a silicone film between the resin base and the metallic master model (silicone copy technique). Statistical analyses were performed with the SPSS Windows for 15.0. Data were submitted to ANOVA and Tukey's post hoc tests at a significance level of 0.05. Results: Comparisons are made among groups submitted to the different polymerization procedure. Interaction of material and polymerization procedure had a statistically significant effect on the final adaptation of the denture bases. When comparing the internal adaptation within each group, all groups of autoclave polymerization had significant decrease of weight of impression materials of mean values (meliodent water bath 2.03±0.17, meliodent autoclave 1.29±0.92; paladent water bath 2.14±0.18, paladent autoclave 1.31±0.94; QC-20 water bath 2.20±0.17, QC-20 autoclave 1.45±0.12). Better internal adaptations were observed when the samples were autoclave polymerized comparing to the conventional heat-polymerized group (p<0.05) Conclusion: Increasing the internal adaptation of resin bases may be achieved by using autoclave polymerization technique, this would markedly contribute to the longevity of denture bases.

Impact of Polymerization Technique and ZrO2 Nanoparticle Addition on the Fracture Load of Interim Implant-Supported Fixed Cantilevered Prostheses in Comparison to CAD/CAM Material

“…Considering that monomer has a boiling point of 100.8 °C, during the conventional polymerization process, the monomer can evaporate and produce bubbles in the resin matrix, resulting in pore formation and deterioration in the PMMA mechanical characteristics. To avert this during autoclave polymerization, radical initiated polymerization is carried out, first at 60 °C to absorb all the free monomer, then at 100 °C or higher to crosslink the polymer [ 22 ]. Durkan et al [ 10 ] investigated the impact of autoclave polymerization on the transverse strength of PMMA in comparison to the conventional water bath method; their results showed that the transverse strength of specimens significantly increased with autoclave polymerization.…”