Abstract
Aims: To determine the suitability of new modified Iraqi plaster and modified Plaster of Paris as a cast in microwave curing of acrylic denture base material, and microwave and open air drying methods on the surface roughness and dimensional accuracy of the cast. Materials and methods: Two types of gypsum products were used in this study {(Iraqi plaster, Plaster of Paris) with the combined additives (Gum Arabic 0.5%, calcium oxide 0.75%, and ferric oxide 0.2%), and Type III stone Plaster/Stone 3:1} that incorporated within the two gypsum products. The effects of drying method and combined additives on the surface roughness and dimensional accuracy of the experimental gypsum products, and acrylic denture base pro-duced from the modified gypsum casts have been evaluated. Mean, standard deviation, variance (ANOVA), and Duncan's multiple range tests were used to analyze the measurements. Results: ANOVA test showed that there was a significant difference in the surface roughness and dimensional accuracy between Iraqi plaster and plaster of Paris with or without additives dried in open air and microwave techniques. Conclu-sion: There was slight dimensional change in the gypsum cast with additives of clinical importance to compensate the polymer shrinkage of the acrylic denture base after cooling. There was no significant dif-ference in the average roughness of acrylic resin cured by microwave oven as a curing method. Keywords: acrylic, roughness, dimensional accuracy.
