Objective To evaluate the air bubble formation and mechanical properties of alginate impression material mixed manually, by a fully automatic mixing machine, and by a semi-automatic mixing machine. Methods Alginate impression materials were mixed by three different methods under the same conditions(room temperature, water/powder ratio, and distilled water temperature). The number and area of air bubbles, compression strain, elastic recovery, and rheological property were evaluated. Results The number and area of air bubbles were statistically different between the materials mixed by three different methods. Material sections from the manual group had the most air bubbles, whereas material sections from the fully automatic group had the least. The manual group had lower elastic recovery compared with the fully automatic and semi-automatic groups. The impression materials were mixed by different methods according to national criteria. The fully automatic group had the best rheological property. Conclusion Mixing methods affected the air bubble content and mechanical properties of alginate material. The mechanical properties of the material mixed by different methods were eligible for clinical use in accordance with national criteria. The alginate mixed with the fully automatic machine showed the best performance.
