Effect of Pressure, Post-Pressing Time, and Polymerization Cycle on the Degree of Conversion of Thermoactivated Acrylic Resin

Abstract

Herein, the effect of different post-pressing times and pressure in two cycles of polymerization on the degree of conversion (DC) of thermally activated acrylic resin (TRRA) is analyzed to optimize the polymerization of this material. After post-pressing for 0, 6, or 12 h, polymerization was performed with or without a pressure of 60 psi (0.41 MPa) in a short (4 h) or a long (11 h) cycle, totaling 12 groups. To determine the DC, PMMA specimens were analyzed by Fourier transform infrared spectroscopy. The influence of each factor alone on the DC was studied by experimental planning. The statistical tests used were three-way ANOVA, t-test, Tukey's test, and Levene's test, with a margin of error of 5%. Two groups prepared with post-pressing times of 12 h had the lowest DC (p < 0.001). Post-pressing times of 0 and 6 h did not yield statistically different results. Pressure increased the DC in only one group (long cycle +12 h, p=0.001). The short cycle resulted in a higher DC than the long cycle in 2 groups (with pressure +0 h, p=0.002; without pressure +6 h, p=0.015), while the long cycle yielded a statistically higher DC in only one group (with pressure +12 h, p < 0.001). The polymerization showed satisfactory DC in all 12 groups. Small differences found among the specimens indicate that the pressure, post-pressing time, and polymerization cycles herein were not influential factors for the DC of PMMA.

Mechanical Properties of the Modified Denture Base Materials and Polymerization Methods: A Systematic Review

“…High-pressure polymerization is a new technique that positively influences the conversion of the monomers into high-molecular-weight polymers by increasing the Dc [ 60 ]. In free-radical polymerization, high pressures greatly increase Dc, with an enhanced propagation rate constant and reduced termination rate constant [ 30 ].…”

Dental Poly(methyl methacrylate)-Based Resin Containing a Nanoporous Silica Filler

“…This suggests that the infiltrated resin inside the filler particles can be polymerized under light irradiation. The degree of conversion for the PMMA-based resins is close to that of commercial heat-polymerized PMMA-based resin (≈92–97%) [ 39 ], whereas it is higher than that of commercial photo-polymerized resin composites for dental bulk-filled applications (≈30–80%) [ 40 ]. Hence, PMMA-based resins are considered acceptable as photocurable resins.…”

Chemical Structure and Physical Properties of Heat-cured Poly(methyl methacrylate) Resin Processed with Cycloaliphatic Comonomer: An In Vitro Study

“…The obtained powder was then sieved to obtain uniform particle size. 18 All the polymeric specimens (powder/solid) were prepared by a single investigator to avoid bias. The study groups and their abbreviations are tabulated in Table 1.…”

“…To prepare the uncured material, the prepolymerized resin powder was heated at 70°C for 30 hours. 18 This led to degradation of benzoyl peroxide and eschewed polymerization reactions of the material after mixing with the monomer. After mixing, the resin paste was placed between two polyethylene films, pressed to form a very thin film, and the infrared beam was passed.…”