Water sorption of heat-polymerized acrylic resins processed in mono and bimaxillary flasks

Abstract

This study evaluated water sorption in heat-polymerized acrylic resins processed in monomaxillary flasks by water bath and in bimaxillary flasks by microwave energy and water bath. Fifty heat-polymerized acrylic resin specimens were fabricated according to the 12th specification of the American Dental Association and assigned to 3 groups: group 1 was processed by water bath in monomaxillary metallic flask; group 2 was processed by microwave energy in bimaxillary PVC flask; and group 3 was processed by water bath in bimaxillary metallic flask. Specimens were submitted to water sorption test, means were calculated and analyzed statistically by Student's t-test. Means (in g/cm 3 ) were: group 1 -0.024085, group 2 -0.025312 and group 3 -0.022098. Microwave energy processing and the amount of stone and resin used in the bimaxillary PVC flask did not influence water sorption; specimens processed in bimaxillary metallic flask by water bath presented lower water sorption means, suggesting an inadequate polymerization of the acrylic resin mass.

The Use of Microwave Energy in Dental Prosthesis

“…The reduction in residual monomer promoted by water bath and microwave post-polymerization treatments could improve the mechanical properties and biocompatibility of the relining and denture base materials. Meloto et al (2006) Vipi Cril heatpolymerized acrylic resin (73ºC for 9 h) and Vipi Wave microwave resin (20 min/90 W and 5 min/450 W) Specimens (m1) were stored in distilled water at 37 ± 1ºC during 30 days (m2), and weighed. Water sorption (g/cm3) was calculated using the formula: WS = (m2 -m1)/ V.…”

“…Acrylic resin also presents water sorption that is directly related to the polar properties of resin molecules, the physical process of water diffusion through intermolecular space (Takahashi et al, 1998), and the amount of residual monomer in the polymerized mass (Wong et al, 1999). Thus, polymerization degree is directly related to resin's ability of absorbing water (Meloto et al, 2006). Polymerization takes place as the free radicals open the double bonds of the methyl-methacrylate, creating a chain reaction where the monomer attaches to polymer free radicals.…”

“…Dimensional changes and distortion of the denture due to the investing stone mold and the heating of acrylic resin can promote tooth movement and, consequently alterations in the occlusal contacts and occlusal vertical dimension (OVD). (Rizzatti- Barbosa et al, 2006;Rizzatti-Barbosa et al, 2005). Acrylic resin processing methods do not avoid displacement of artificial teeth during denture inclusion and processing, which might increase occlusal vertical dimension due to production of premature contacts (Barbosa et al, 2002).…”

“…Simultaneous polymerization of maxillary and mandibular complete dentures with the teeth in occlusion by means of a special double flask (DF), has been described as a more rapid and simple method for investing and polymerizing prostheses (Rizzatti- Barbosa et al, 2005). This inclusion technique was claimed to save time and decrease occlusal alteration during denture processing (Meloto et al, 2006). It may be an easier and faster method of investing and polymerizing prostheses.…”

Padronização da metodologia para análise de sorção de água e solubilidade de materiais resilientes temporários para base de prótese

“…É bem estabelecido na literatura que, na resina acrílica, a absorção de água causa uma ligeira expansão da massa polimerizada e ao mesmo tempo interfere no entrelaçamento da cadeia polimérica agindo como um plastificante, o que altera as características físicas do material (ANUSAVICE; ZHANG; SHEN, 2006;MELOTO et al, 2006). Nos materiais resilientes à base de resina acrílica, sobretudo os temporários, cuja resiliência é atribuída à alta concentração de plastificantes e solventes, a perda desses componentes para o meio aquoso é muito superior ao efeito plastificante da água (BRADEN; WRIGHT, 1983).…”