Comparison of The Surface Roughness of Gypsum Models

Objectives: The purpose of this study was to evaluate the effects of (1) various impression materials, (2) different storage time periods and (3) different gypsum products on the surface roughness of gypsum models. Methods: Three alginates (Algiace Z, CAVEX and Jeltrate), four silicones (Aquasil LV, Coltex fine, Exaflex injection, Take 1 wash) and three gypsum materials (MG Crystal rock, SH stone and MS plaster) were used. Impression materials were mixed following the manufacturers' instructions and poured into a plastic ring (20 mm in diameter with 2 mm height) which was on a glass slab. After an impression material had set, gypsum product was immediately poured into the negative impression surface, and waited for 1 hour to ensure complete model setting. The second and third rounds were made 1 hour and 24 hours later, respectively. The surface of set gypsum models were measured by Surfcorder. Because each impression was used to make three rounds, three-factor with interaction ANOVA was used. Results: The results showed that: (1) Most of the surface roughness (Ra) of specimens made by alginate material (from 2.72 ± 0.45 µm to 7.42 ± 0.66 µm) are rougher than silicone materials (from 1.86 ± 0.19 µm to 2.75 ± 0.44 µm). (2) The surface roughness of the specimens were least influenced by various storage time periods. (3) Different brands of gypsum products had clearly effect on the alginate materials group (the surface roughness were SH stone > MG Crystal rock > MS plaster), than silicone materials group does. Conclusions: The surface roughness of gypsum products models was affected more by using alginate or silicone impression materials than the storage time factor. The surface roughness of poured gypsum models was affected by different brands of gypsum product when using alginate impression materials.