Extrusion speed and performance of automated mixing units

Objectives: Dental professionals expect an automatic mixing unit to quickly deliver an impression material to either a tray or an intraoral syringe. Speed is important as impression materials have a finite amount of working time. The objective of this study is to compare the extrusion speed and the drive performance of common automated mixing units to determine if there is speed loss when dispensing high viscosity impression materials.

Methods: Five samples of a type 2 (3M ESPE; Impregum Penta Soft Quick; M1) and a type 0 impression material (3M ESPE; Express 2 Penta Putty; M2) were mixed with Pentamix 3 (3M ESPE; P3), Pentamix 2 (3M ESPE; P2), Plug & Press Dispenser (Kettenbach; PP), Dynamix (Heraeus Kulzer; DM) and with MixStar (DMG; MS) for exactly 30sec. After the materials had polymerized the weight of the samples was measured using a scale. The obtained values were used to calculate the average extrusion speed in ml/min.

Results: The mean of extruded impression material in ml/min and standard deviations (in brackets) for M1 and M2 by device was: P3: 156.15 (3.97) and 153.58 (0.49); P2: 83.18 (2.02) and 76.05 (1.07); PP: 102.48 (2.66) and 80.00 (3.44); DM: 74.93 (2.86) and 71.15 (0.84); MS: 46.85 (0.81) and not applicable. ANOVA (p<0.05) showed significant differences of extrusion speed for the following units (value in brackets): P2 (8.57); PP (21.94); DM (5.04); MS (not applicable).

Conclusion: Compared to the other automated mixing devices tested, P3 showed the highest extrusion speed and no significant difference when dispensing a type 0 and type 2 impression material. MS was not able to extrude a type 0 impression material. The time it takes to dispense a material depends on the type of the automated mixing device and may vary with the viscosity of the impression material.