Dimensional Accuracy and Surface Roughness From Three Alginate Surface Treatments

There is no standardized method for preparing the surface of alginate before taking impressions; however, several techniques are used. OBJECTIVES: This study evaluated three different alginate surface treatments on impression dimensional accuracy and surface roughness. METHODS: Identic alginate (Dux Dental) was used in this study. Impressions were made of a polished 4.5x2x1cm stainless steel block mounted to an acrylic sheet. Ten impressions were taken for each three different treatment groups, the alginate was: 1) smoothed with water, 2) smoothed without water, and 3) roughened before taking impressions. In the water smoothed group the operator dipped his hand in a running faucet and smoothed the surface. The smoothed without water group was smoothed with the spatula and operator fingers. In the rough group, 1/4inch hardware cloth screen coated with acrylic was placed into the loaded tray to roughen the surface. The casts were immediately poured up with vacuum-mixed die stone (Whip Mix) and allowed to set for 1hour before removal. For each cast, three length and three width measurements were recorded and averaged using micrometers with 0.00005 inch resolution. The surface of each cast was scanned at three locations with a Surfanalyzer 5400 (Federal). Differences in dimensions and surface roughness between the three treatments were tested using ANOVA and Tukey tests with α=0.05. RESULTS: No differences were found in dimensions between the three treatment groups (p>0.24). We found a very small and statistically insignificant increase in length and width of casts from all three treatments as compared to the stainless steel block. In addition, differences in surface roughness (Ra and Rt) between the three treatments were not statistically significant (p>0.14) although the stainless steel block showed significantly lower Ra and Rt. CONCLUSION: The three alginate treatments did not lead to statistically significant differences in either dimensions or surface roughness.