Dimensional Stability of Zinc Oxide Eugenol Impression Material

Methods: The investigated material was zinc oxide-eugenol impression paste (White Impression Paste, S.S White Manufacturing, Gloucester, England). 12 standard horseshoe-shaped trays of 2.5mm thickness were fabricated with self-curing acrylic resin (Vertex SC, Dentimex, Zeist-Holland). After a 24h waiting time, standard 2 mm thick zinc oxide-eugenol impressions were made of the horseshoe trays using the prepared trays. The dimensional measurements were made between four reference points at four different time intervals.(10 min, 30 min, 24 h, 48 h). For reliabilty the measurements were repeated 3 times. Two different measuring systems were used: 1) Digital caliper (±0.01mm), and 2) Computer aided measuring of digitalized images (±0.0001mm).

Results: The results were analysed statistically using Friedman test and the comparison between two measuring methods was made by Kruskal-Wallis test. It was found that there were no statistically significant dimensional changes in the first 3 time interval groups (Sample t-test: p>0.05). The 48 hour test group was statistically significant in terms of dimensional changes (Sample t-test: p<0.05). No significant differences were found between the findings of the two test methods and the data indicate that the two measuring methods provide comparable and reliable measurements of dimensional changes (Kruskal-Wallis: p<0.05).

Conclusion: Dimensional change will occur in zinc oxide impression materials after 24h impression taking.