[Effect of three mixing methods on air bubbles and solidification state of alginate impression materials].

Purpose: To evaluate the effect of full-automatic mixing machine method, clockwise manual mixing and combined eight-shaped manual mixing on air bubble content, flowability, temperature, working time and setting time of alginate impression materials.

Methods: With the same condition, alginate impression materials were mixed by three different methods. The number of bubbles, area, flowability, temperature, working time and setting time were evaluated with SPSS 24.0 software package.

Results: The number of bubbles in the automatic mixing group was (2.30±2.50), and the area was (0.17±0.18) mm2, which was less than the number of clockwise manual mixing group (59.60±14.19), and the total area (7.41±2.24) mm2 (P＜0.01). The flowability of the clockwise manual mixing group [(39.52±0.85) mm] was less than that of the full-automatic mixing group [(50.78±0.90) mm] and the combined eight-character manual mixing group [(50.36±1.75) mm](P＜0.01).The setting time of the material mixed by three methods was eligible for clinical use.

Conclusions: The mixing method of alginate impression material has an effect on material's bubble content, flowability and temperature changes. The impression materials mixed by full-automatic mixing method are better in terms of bubble content, flowability and other properties. If manual mixing is used, combined eight-shaped manual mixing method can help reduce impression bubbles and deformation, and improve flowability.