Contact Angle of Water on Silicone Containing Impression Materials

Objectives: To measure and compare the contact angle of water on two different impression materials; vinyl polysilicone (VPS) and vinyl polyether silicone (VPES). A bisacryl composite for provisional restorations was used as a non- silicone reference material.
Methods: The following impression materials were measured. VPS materials, Aquasil Ultra LV (AQLV), Heavy (AQH), and XLV (AQXLV)) (Dentsply/Caulk) . VPES materials: EXA’lence Light body (ELB) and Heavy body (EHB) (GC America). A bisacryl composite was used as a non-silicone material , Structur Premium A3 ( Voco). Each material specimen was made from a small circular mold of 25mm diameter and 18 mm thick. Each specimen was placed into a Ramé-Hart Drop Image Goniometer. One drop of water was dispensed on the surface, and an initial image was captured. After 15 seconds, another image was captured and repeated for a total of 4 images per material. The contact angle for each image was measured using a hand held protractor for initial angle measurements.
Results: A graph was generated to show the different contact angles of each material over time. (Figure 1) As the drop expands over time, the drop diameter increased, creating an advancing contact angle. This trend was the seen for all impression material.
Conclusions: Advancing contact angle is lower than the initial contact angle over time. We see this phenomenon in all impression material. There were no significant angle differences between the vinyl silicon vs vinyl polyether silicon based blend. The reduction in advancing contact angle was less for the bisacryl material.