Evaluation of porosity in microwave-processed acrylic resin using a photographic method

Yannikakis, S; Zissis, A; Polyzois, G; Andreopoulos, A

dc.contributor.author	Yannikakis, S	en
dc.contributor.author	Zissis, A	en
dc.contributor.author	Polyzois, G	en
dc.contributor.author	Andreopoulos, A	en
dc.date.accessioned	2014-03-01T01:17:52Z
dc.date.available	2014-03-01T01:17:52Z
dc.date.issued	2002	en
dc.identifier.issn	0022-3913	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/14686
dc.subject.classification	Dentistry, Oral Surgery & Medicine	en
dc.subject.other	acrylic acid resin	en
dc.subject.other	article	en
dc.subject.other	heat	en
dc.subject.other	mathematical computing	en
dc.subject.other	microscopy	en
dc.subject.other	microwave radiation	en
dc.subject.other	photography	en
dc.subject.other	polymerization	en
dc.subject.other	porosity	en
dc.subject.other	thickness	en
dc.title	Evaluation of porosity in microwave-processed acrylic resin using a photographic method	en
heal.type	journalArticle	en
heal.identifier.primary	10.1067/mpr.2002.124490	en
heal.identifier.secondary	http://dx.doi.org/10.1067/mpr.2002.124490	en
heal.language	English	en
heal.publicationDate	2002	en
heal.abstract	Statement of problem. The effect of microwave polymerization on the porosity of denture base resin has not been fully determined. Purpose. This study investigated the effect of microwave energy on the porosity of 2 heat-activated denture base resins. Material and methods. Two heat-activated denture base resins, one conventional (Paladon 65) and one designed for microwave polymerization (Acron MC), were used to prepare 50 test specimens. Five groups of 10 specimens each were established: Group A (Paladon 65, water bath); Group B1 (Paladon 65, short microwave cycle); Group B2 (Paladon 65, long microwave cycle); Group C1 (Acron MC, short microwave cycle); and Group C2 (Acron MC, long microwave cycle). Half of the specimens in each group were 3 mm thick, the other half 6 mm thick. After being polymerized, specimens were cut so that 3 cross-sectional areas were formed (S1, S2, and S3). These surfaces were polished and photographed under a microscope at x100 magnification. On the developed photographs, the area of each pore was measured with a digital planimeter, and the total area of pores per surface was calculated in percentage form. The total number of pores on each surface and the topographical distribution of the pores also were recorded. A 3-factor repeated-measures analysis of variance was used to compare porosity data, and a 1-way analysis of variance was performed to determine possible interactions between groups based on material and specimen thickness (P<.05). The effect of surface area on porosity data was analyzed with the use of contrasts. Results. Group A specimens exhibited no pores. In the thicker specimens of Groups B1 and B2, giant pores (area as great as 3.69 mm2) and small, gaseous pores of almost uniform shape and size were found. In Groups C1 and C2, only the smaller pores were found; these were not clinically significant. Of the observed surfaces, 75.3% were free of pores and 24.7% contained at least one pore. In a selected group of pore-bearing surfaces, the majority (81%) had pores located near the center. The thicker specimens in Group B exhibited the greatest amount of porosity (P<.0001); Group C specimens exhibited the least porosity. Repeated-measures analysis of variance showed that polymerization cycle had no effect on porosity (P=.19). The 3 other factors (material, specimen thickness, and surface) and all possible interactions among them were significant (P<.05). Among the surfaces, S1 and S2 exhibited the highest total mean value of porosity (0.71% and 0.74%, respectively) and S3 the lowest (0.025%). S3 showed a different pattern of porosity than S1 and S2. Conclusion. Within the limitations of this in vitro study, minor porosity was identified in thin and more severe porosity in thicker areas of conventional resin specimens that underwent microwave polymerization. The resin designed specifically for microwave polymerization exhibited no clinically significant porosity. Copyright © 2002 by The Editorial Council of The Journal of Prosthetic Dentistry.	en
heal.publisher	MOSBY, INC	en
heal.journalName	Journal of Prosthetic Dentistry	en
dc.identifier.doi	10.1067/mpr.2002.124490	en
dc.identifier.isi	ISI:000177074100005	en
dc.identifier.volume	87	en
dc.identifier.issue	6	en
dc.identifier.spage	613	en
dc.identifier.epage	619	en