Comparison of the Surface Roughness of Gypsum (Dental Stone) with three Types of Tissue Conditioner Impression Materials over Time

Statment of Problems: Although the primary use of tissue conditioners is for healing the damaged mucosa but they can also be used as functional impression; it seems that its effeicasy depends on its viscoelastic features such as compatibility with gypsum and surface roughness. The aim of this study is to compare the surface roughness of gypsum with several tissue conditioner impression materials avaliable in the market. In this experimental study, three tissue conditioners (Acrosoft, viscogel & GC) were used. Pars dental gypsum moldano Type III and a polyvinyl siloxane impression were used for the controls. The tissue conditioners powder liquid ratio was mixed according to the manufacturer’s recommendation and immediately poured in a mold with an internal diameter of 18 mm and depth of 2mm. The mold was completely filled. Then, a glass block with the mean roughness of 0.8 µm was placed on its surface for two hours. Then, the 5 samples were immediately placed in 37oC water for 0-24 hrs, 3, 7, and 14 days. After that, the specimens were beaded, boxed and poured with pars dental gypsum type III. The gypsum sample’s surface roughness was measured with profilometer with the length of 2.5 mm and cut-off of 0.8 mm. The results were analyzed using ANOVA and Tukey tests. The results showed that surface roughness of Acrosoft in different storage times did not change significantly and there was no significant difference between Acrosoft and the control group. Viscogels surface roughness was significantly different with all other groups at zero time; with the increase of storage time the surface roughness decreases. The control group showed a significant difference with viscogel at zero time and with GC at 24 hrs and 3 days but it revealed no difference with the other groups. The least surface roughness belonged to GC at zero and 14 days and the highests surface roughness belonged to viscogel at zero time. Surface roughness depends on the chemical structure of the material. The best time for pouring with tissue conditioners for functional impression is 24 hrs to 3 days after making impression. Acrosoft had no significant difference with the control groups at any time.