05). … Table 6. Mean, standard deviation and P values of data (mm) obtained from linear measurements of distances between 4 references points (A,B,C, and D) in rounded PF01367338 palatal vault rounded groups 24 h after polymerization and after 30 days of water storage. According to data of statistical analyses, the results of the present study are as follows. Not any significant distance difference was found at acrylic resin/stone cast interfaces measured at 7 marked regions in sagittal sections, 24 hours after polymerization and after 30 days of water storage, in any of the experimental groups (P>.05) (Table 2). Not any significant linear dimensional difference was found in acrylic resin/stone cast interfacial distances measured at 5 marked regions in frontal sections, 24 hours after polymerization and after 30 days of water storage, in any of the experimental groups (P>.
05) (Table 3). In U-SHAPED groups; significant differences were found between linear measurements performed 24 h after polymerization and after 30 days of water storage in all groups (U/NOF, U/WOF, U/ROF) P<.01 (Table 4). In V-SHAPED groups; significant differences were found between linear measurements performed 24 h after polymerization and after 30 days of water storage in all groups (V/NOF, V/WOF, V/ROF) (P<.01) (Table 5). In ROUNDED groups; significant differences were found between linear measurements performed 24 h after polymerization and after 30 days of water storage in all subgroups (ROUNDED/NOF, ROUNDED/WOF, ROUNDED/ROF) (P<.01) (Table 6).
DISCUSSION Polymerization shrinkage and water sorption, in other words, the parameters affecting the dimensional stability of acrylic resins denture base materials have been the subject of numerous studies.2�C7 Thickness of the denture, thermal expansion and contraction of the acrylic resin and the gypsum, structural variations between polymer and monomer systems, polymer/monomer ratios, packing pressure, polymerization shrinkage, investments, separators, internal stresses, water sorption and desorption and water content of the gypsum were reported as other parameters influencing the dimensional stability of an acrylic resin denture.2�C10 Two methods were mostly used for the determination of dimensional alterations in acrylic resin denture base materials: Determination of the present closeness (adaptation) of acrylic resin base to the definitive stone cast surface,6,7,18 and distance measurement between determined reference points on an acrylic resin denture base.
3,5,8 Both methods were used in the present study to provide reliable results. This method provided real-time direct dimensional changes of the denture base resin during the fabrication process, as reported by Kawara et al.22 Heat polymerized acrylic resin denture base material GSK-3 and conventional flasking technique were used in the present study due to the ease of processing and to minimize the complications faced during the impregnation of glass fibers into the acrylic resin bulk.