Evaluation of IvoBase(RTM) automatic injector denture processing system residual monomer reduction function
Cagino, Catherine G.
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Purpose: The purposes of this study were: 1. To determine residual methyl methacrylate (MMA) levels in 3 denture base resins processed with the IvoBase automated injector unit using the standard processing program and the reduction of monomer residue program (RMR). 2. To compare residual MMA values to those reported by the manufacturer. Methods: Eighteen discs (d=50 mm, h=2 mm) were fabricated using (1) IvoBase High Impact, (2) IvoBase Hybrid and (3) IvoCap High Impact (Ivoclar Vivadent, Amherst, New York) following manufacturer's instructions. Three discs were fabricated for each acrylic resin via processing by the standard program and three additional discs were fabricated for each acrylic resin using the RMR function. Each disc was fractured to yield three separate samples weighing approximately 650 mg each (n=9 per acrylic resin, per processing method: total 54 samples). Specimens were stored at -18°C for eight weeks after which monomer was extracted according to ISO 20795-1. Gas chromatography/mass spectroscopy (Model GCMS-QP2010, Shimadzu Corporation, Tokyo, Japan) was utilized to determine residual MMA. IBM SPSS (Version 22, IBM Corp, 2013) was used to analyze data. One sample t-tests were used to compare residual MMA to manufacturer's reported values. Two-way ANOVA and Tukey multiple comparison post-hoc tests evaluated interaction effects of acrylic resin and processing method. Results: Mean residual MMA processed with standard and RMR for IvoBase High Impact was 1.24% and 0.9%, for Hybrid 1.36% and 0.6% and for IvoCap 0.86% and 0.7% respectively. All samples tested fulfilled the ISO 20795-1 residual monomer limit for both auto cure (4.5%) and heat cure (2.2%) denture base resins. Conclusions: IvoBase High Impact processed with standard processing yielded expected values of residual MMA (p=0.48); however, when processed with RMR the values were significantly higher than expected (p<0.001 [manufacturer RMR 0.7%]). IvoBase Hybrid acrylic resin processed with standard and RMR functions resulted in expected residual MMA levels (p=0.649, p=0.420). However, IvoCap acrylic resin processed with standard and RMR functions yielded lower residual MMA than expected (p<0.0005 [manufacturer standard 1.5%, RMR 1.0%]). IvoBase High Impact and Hybrid had significantly lower levels of residual MMA when the RMR function was utilized over standard processing (p<0.05); IvoCap acrylic resin did not (p>0.05).