The Accuracy of Different Combinations of Dental Materials

Objective: To assess the accuracy and reproducibility of casts obtained from different combinations of impression materials and dental stones Methods: Eight different impression materials (Aquasil™, Aquasil™ DECA, Affinis™, Express™, Extrude™, Impregum™, President™ and Take 1™) and two dental stones (Moonstone™ and Fuji Rock™) were tested in this study. All materials were mixed according to the manufacturers' instructions. Six impressions from each material were taken of a custom standard having similar dimensions to a dentate jaw with machined cylinders resembling teeth prepared for fixed restorations. After a 24 hour delay, three impressions from each material were poured in either of the two dental stones. Each of the 48 impressions were scanned on a non contacting laser profilometer (NCLP - Taicaan® technologies – Southampton UK) accurate to 0.1 µm and precise to 0.3 µm. The mean step height from the top of each cylinder to the base was measured using surface metrology software. Further to this, the custom standard was scanned directly on the NCLP and the same measurements from the top of the cylinders to the base were obtained. This allowed for comparisons from measurements obtained from the casts to those obtained directly from the standard. Results: The range of measurements for casts poured in Moonstone™ was 7.26mm to 7.29mm and for Fuji Rock™ they were 7.20mm to 7.29mm. There was no statistically significant differences in measurements for different impression materials or dental stones (ANOVA p<0.05). There was high level of agreement between measurements obtained from the gold standard and compared to those obtained from the casts (ICC r=0.99) Conclusions: All combinations of materials were accurate. This technique may be used to validate other software, such as surface matching. This study was supported by the Guy's and St Thomas' Charity and the Royal College of Surgeons of England.