Evaluation of residual monomer in autopolymerizing acrylic resins: spectroscopy analysis

Roberto ROCHA FILHO, Lylian Vieira de PAULA, Vilma Conceição COSTA, Paulo Isaias SERAIDARIAN

Aim: Two comercial brands of auto polymerizing acrylic resins (one for orthodontics use, Orto Cril®, and the other for prosthetics use, Jet®) were analyzed concerning the amount of methyl methacrilate (MMA) monomer dissolved in solution, processed under and not under pressure, in different intervals (0.083; 0.25; 1; 1.25; 2.17; 5; 9; 14 and 21 days). Methods: The ultra-violet absorption spectroscopy was used in the analysis of aqueous solutions of MMA, with known concentrations, in order to determine the calibration curve. Aqueous solutions containing samples made with the acrylic resins described above were submitted to ultra-violet absorption spectroscopy analysis. Results and Conclusions: The results were compared to the calibration curve data, in order to establish the MMA concentration. These results led to the conclusion that the residual MMA level dissolved in the solution was higher in the first twenty-four hours, tending to stability from this period on. Auto polymerizing acrylic resins processed under pressure showed higher levels of MMA, even though it was not noticed an interaction effect between the resins brand and the presence of pressure in the level of MMA concentration measured throughout the intervals. In spite of that, the three variables (time, resins and pressure) were of noticeable importance.

Keywords: Acrylic resins. Residual monomer. Methyl methacrilate. Spectroscopy.

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