Practice-based PREP Panel handling evaluation of a new impression mixing device and the associated material.

AIMS: To evaluate the handling of a new impression mixing device and the associated impression material by general dental practitioner members of the PREP Panel. DESIGN: By means of a questionnaire, the participating practitioners recorded their views on the mixing machine and impression materials, having used these for ten weeks. SETTING: UK general dental practices. PARTICIPANTS: General dental practitioner members of a UK practice-based research group. METHODS: A questionnaire was designed to elicit views on the performance of the mixing device and impression material under test. This was distributed to the practitioners who had used the test materials for 10 weeks and the data thereby obtained collated and presented, principally in the form of VAS scales. OUTCOME MEASURES: Rating of various parameters of the mixing device and impression materials on VAS scales. RESULTS: The Pentamix 3 machine scored well for ease of initial use [4.8 on a visual analogue scale (VAS) where 1 = very difficult to use and 5 = very easy to use]. In a range of criteria (including cleanliness, easy handling, time to fill the tray and overall convenience) the Pentamix scored highly on VAS scales. A maximum score of 5 (on a VAS where 1 = very dissatisfied and 5 = very satisfied) was achieved for reproducible mixing quality. The appreciation of the Pentamix 3 mixing machine was demonstrated by the fact that 85% (n = 11) of evaluators stated that they would recommend it to colleagues. Regarding the impression material under evaluation, 85% (n = 11) of the evaluators stated that they would recommend Impregum Quick impression materials to their colleagues. CONCLUSIONS: Within the limitations of this study, the Pentamix 3 automatic impression mixing device scored highly in this assessment, together with the impression materials assessed.

Investigation of a new approach to measuring contact angles for hydrophilic impression materials.

PURPOSE: The purpose of this investigation was to examine the initial water contact angles of seven unset impression materials using commercially available equipment, in an effort to determine whether polyether impression materials (Impregum) have lower contact angles and are, therefore, more hydrophilic than VPS impression materials. MATERIALS AND METHODS: The hydrophilic properties of unset polyether and VPS impression materials were analyzed with respect to their water contact angle measurements using the commercially available Drop Shape Analysis System DSA 10. Twenty-five data points per second were collected via video analysis. There was no delay from start of measurement and data collection. Data was collected for approximately 12 s. Droplet size was determined on the thickness of canula. If the droplets became too small in volume, the water that evaporated during the measurement was large in comparison to the volume of the droplet. Therefore, 5 microl was chosen as the lowest volume. Five trials were conducted per series for each featured material. Contact angles were calculated using the circle fitting method. Three tests using this technique were designed to control the variables of contact angle measurement with regard to time, the varying amount of fluid in contact with impression material during clinical use, and material thickness. Sample thickness of impression material was controlled by stripping the paste flat on a glass plate using a marking template to ensure a constant film thickness. Tests were conducted in a climatized room at 24 degrees C +/- 1 degree C. Deionized water was used as the fluid. The device was calibrated according to manufacturer's instruction for Young-Laplace fitting prior to the measurements. Results were analyzed using One-Way ANOVA, Tukey test, and t-test, as appropriate. RESULTS: Comparing the fast setting impression materials by One-Way ANOVA and Tukey tests (p < .05) revealed the initial contact angles to range from 66.2 +/- 1.5 degrees to 127.5 +/- 4.4 degrees , of which the polyether material was the lowest after 45 s (66.2 +/- 1.5 degrees ), 120 s (70.3 +/- 2.8 degrees ), and 24 h (80.3 +/- 1.0 degrees ) after start of the mix. The selected times represent the different stages of unset material, ranging from 45 s as the earliest practical data collection time to 24 h, at which a stone model would be poured. The polyether materials tested exhibited lower contact angles and, thus, significantly higher initial hydrophilicity than all measured VPS materials. Additionally, Impregum impression materials are more hydrophilic in the unset stage than in the set stage. VPS may show a stepwise development of hydrophilicity in the set stage that was not observed in the unset stage. CONCLUSIONS: The polyether impression materials tested were significantly more hydrophilic before, during, and after setting than that of VPS impression materials. Regardless of the amount of water in contact with the impression material, the polyether impression materials showed a significantly higher hydrophilicity in the unset stage than the VPS materials. The initial contact angle was not dependent on the thickness of the material. All parameters, including variation of time, volume of water droplet, and thickness of material, resulted in different absolute contact angles, but did not lead to a dramatic change in the ranking of the materials with regard to their hydrophilic behavior.