The influence of different mixing methods on the dimensional stability and surface detail reproduction of two different brands of irreversible hydrocolloids

Purpose: Irreversible hydrocolloid impression materials are some of the most common impression materials in dentistry. Preparation of alginate is critical for dental appliance fabricated upon the cast made directly from the impression. This study compared the effect of two mixing methods i.e. hand mixing or device mixing on the physical properties of two different brands of irreversible hydrocolloid. Materials and Methods: Two alginate impression materials: Cavex Tulip (Tulip, Cavex Holland BV, Haarlem, Holland) and Hydrogum Soft (Zhermack, Rovigo, Italy), were mixed according to manufacturers instroductions with two mixing methods. Mixing was performed at room temperature using tap water. The material was allowed to set in a water bath at 35°C (±1°C), simulating intra-oral setting conditions. For each tested material, nine standardized samples were used. The first method was hand mixing; the other method was with a device. Detail reproduction and dimensional changes of impressions were compared. One-way analysis of variance was performed to compare the dimensional differences between the four groups. Results: The device mixed speciemens showed better surface detail than hand-mixed samples. Cavex alginate demonstrated better surface detail than Hydrogum. Cavex Tulip alginate showed better dimensional stability than Hydrogum Soft in both hand-mixed and device-mixed samples. Furthermore, all device mixed samples were better than hand-mixed in terms of dimensional stability. A two-way analysis of variance and Fisher's protected least significant difference test at the 0.05 level of significance were used to analyze the data. Conclusion: Of the two mixing methods, the vacuum mixer had the best performance overall in reducing the number, percent and volume of porosities in the mixed alginate.