Mixing quality of static and dynamic mixers for impression materials

Objectives: One distinctive requirement of dental impression materials consisting of two components (base and catalyst) is the homogeneity of their mixture. Only a homogenous mix guarantees the material properties necessary for precise impressions. Goal of this study is to compare the mixing quality offered by static and dynamic mixing tips used for automixable VPS and polyether impression materials. Methods: A common impression material (3M ESPE, Permadyne Penta L) was mixed with a dynamic mixing tip (3M ESPE, Mixing Tip Red; D) and with a static mixing tip (MixPac, white mixer; S). Three samples each were generated with a mixing device (3M ESPE, Pentamix2). S – instead of D normally not used with Pentamix - was mounted at the mixing device by an adapter. The distribution of the two paste components (catalyst and base paste) having different colors was measured with a spectrometer (Ocean Optics, S2000) and a lens system enabling a spacial resolution of 0,1mm after setting. The samples were moved in the focus of the lens system on a zigzag course in an area of 2x8mm by two linear axis. During this movement the b-value of the Lab color system was recorded by a data logger (85 values per run and sample). The standard deviation of the b-value of each sample is used as metric for the mixing quality. Results: The mean of the standard deviations of color values of each group of samples was (mean, SD in brackets): D: 0,671 (0,059) and S: 1,757 (0,121). As shown by ANOVA (p<0,05) the standard deviation of the color value of the samples mixed with S is significantly higher than the ones mixed with D. Conclusion: With respect to the deviation of the measured color value D enables a more homogenous mix than S does.