Bonding properties and dimensional stability of hydrocolloid impression systems in fixed prosthodontics.

Four hydrocolloid impression systems for fixed prosthodontics and one conventional alginate were tested for bonding properties between the syringe and the tray materials of the systems. Their dimensional stability was tested also after the impressions were kept in a humidor for 1, 3, and 24 hours before casts were poured. Findings showed that there was a true bond between the syringe and the tray materials for all combinations. The precision tests gave a mean percent difference between the master model and the cast of less than 0.15 for all material combinations at both the 1- and 3-hours observations. The same was true at the 24-hours observation, except for one combination. From a clinical point of view, all the materials can be used for fixed prosthodontic impressions even if kept for 1 and 3 hours in 100% humidity before pouring the casts; however one material was unsuitable if kept for 24 hours before pouring.