Abstract: PURPOSE: The effect of clockwise mixing method and clockwise combined eight-shaped mixing method on the accuracy of alginate impression was compared. METHODS: From march to April 2018, 40 dental restoration cases in the Department of Stomatology, Zhoupu Hospital, Pudong District, Shanghai were selected. Two nurses and the same doctor treated 40 patients with single crown porcelain restoration. Two sets of models were taken by two kinds of mixing methods, which were divided into experimental group and control group. Clockwise manual mixing method was used in the control group to take the model, while clockwise combined eight-shaped mixing method was used in the experimental group to take the model. SPSS 24.0 software package was used for Mann-Whitney rank sum test. RESULTS: The same high-grade technician used a magnifying glass to observe the prepared impression, recorded the shoulder print, the sulcus wing and bubble generation, and comprehensively evaluated the impression quality. A comparison was made between the two groups, Z=-4.634, P<0.001, and the difference was statistically significant. Among them, the ratio of excellent quality of the clockwise combined eight-shaped mixing method (77.5%) was significantly higher than that of the clockwise mixing method (10%), and the proportion of level IV unqualification (2.5%) was significantly lower than that of the clockwise mixing method (27.5%). CONCLUSIONS: The quality of impression using clockwise combined eight-shaped mixing method is higher than that of the clockwise method, which improves the success rate of the mold and reduces the discomfort caused by repeated impression. Application of this technique is helpful to the promotion of occult knowledge among nurses.

Key words: Mixing method, Accuracy, Alginate, Dental impression model, Tacit knowledge