Type IV Gypsum Compatibility of 5 Addition-Cured Silicone Impression Materials

Statement of the Problem: There is little information available on compatibility between addition-cured silicone impression materials and type IV dental stones. Objective: The purpose of this study was to compare surface detail reproduction between various combinations of contemporary addition-cured silicone impression materials and type IV dental stones. Materials and Methods: Under standardised conditions, 300 impressions were made of a ruled test block (ADA specification 19), using five addition cured silicones namely; Examix™-NDS, Doric-Es Flo-Light, Panasil® Contact Plus, Extrude Wash and President Plus Jet. In groups of 15, the impressions were poured with type IV dental stones namely ; Silky Rock, Fuji Rock, Suprastone and Vel-Mix. Two independent examiners at 12x magnification scored the entire 20µ (micron) line. Results: (1) All impression materials could fully reproduce the 20µ line. (2) Different impression materials showed different compatibility with different stones. (3) Only 25% of the casts poured from type IV dental stones used could fully reproduce the resultant 20µ line with fine margins, 88% of the fully reproduced casts were Suprastone. Conclusion: Not all combinations of impression material and type IV dental stone used exhibited similar compatibility. Clinical Implications: For optimal compatibility clinicians and technicians should carefully select the combination of silicone impression material and type IV stone that they use.