Clinical Comparison of Two Impression Materials-Effectiveness for Inexperienced Operators

Clinical success of fixed restorations greatly depends on the accuracy of the final impression. Objectives: This study evaluated the ability of a new polyvinyl siloxane (PVS) impression material (Imprint 3, 3M ESPE, St. Paul, MN) (Material-A) to obtain void-free final impressions for indirect fixed full-coverage restorations compared to a hydrophilic PVS impression material (Aquasil Ultra LV, LD Caulk, Milford, DE) (Material-B) when used by inexperienced clinicians (pre-doctoral dental students/junior and senior classes). Methods: 300 patients were enrolled in the study at the University of Alabama in Birmingham/School of Dentistry. Those meeting the inclusion criteria were randomly assigned to one of two treatment groups A or B. Calibrated examiners evaluated the first impression of prepared posterior teeth at a magnification of 10X for acceptability (no voids or bubbles) according to the data collection sheet. Criteria evaluated and recorded were: position of tooth, type of preparation, preparation finish line (Class I-V), and gingival bleeding score. All impressions were made using a heavy tray material and a light body syringe material. Only the first impression of each patient was evaluated since multiple interventions (additional impressions, cord packing etc.) could have caused varying conditions influencing the ability to obtain an acceptable impression. The Fisher-Freeman-Halton test was used to test for associations between material and gingival bleeding score. Logistic regression was used to assess the effect of material on success of the impression (acceptable/unacceptable) (p=0.05). Results: There was no difference in the ability of the third year class (junior) or the fourth year class (senior class) in their ability to make an accurate impression the first time using both materials. There was no difference between the two impresson materials (p>0.05). Conclusion: PVS materials tested in this study give accurate impressions when inexperienced clinicians take the impressions. Supported in part by 3M ESPE.