Selected characteristics of a new polyvinyl siloxane impression material - A randomized clinical trial

Objectives: This study evaluated the ability of a new polyvinyl siloxane impression material (Affinis, Coltène/Whaledent, material A) to obtain final impressions free of bubbles and voids for indirect fixed cuspal-coverage restorations. The results were compared to a control polyvinyl siloxane impression material (material B). Both materials were handled by inexperienced clinicians (undergraduate dental students) in student clinics. Method and Materials: One-hundred and thirty patients who were treated in the Louisiana State University School of Dentistry Junior Student Clinic for indirect fixed cuspal-coverage restorations and who met the inclusion criteria were randomly assigned to either one of two treatment groups, group A (n = 65) or group B (n = 65). Two calibrated examiners evaluated the first impression of prepared posterior teeth at a magnification of 10 for acceptability (no voids or bubbles). Position of tooth, type of preparation, preparation finish line (Class I-V), and gingival bleeding scores were recorded. All statistical tests were performed with the level of significance set at .05. Results: The Fisher-Freeman-Halton test did not reveal significant associations between material and gingival bleeding score (P = .492). Significant differences in the location of the preparation finish line between materials were observed (P = .0096); material A was more frequently used in cases where the preparation finish line was located at least 2 mm subgingivally. Logistic regression was used to assess the effect of the material on the success of the impression (acceptable/ unacceptable). Material was highly significant in the logistic model (P .001) with an odds in favor of an acceptable impression being eight times higher with material A than with material B (odds ratio = 8.00; 95% confidence index for odds ration: 2.832, 22.601). The 60/65 (92.3%) impressions made with material A and 39/65 (60%) impressions made with material B were rated "acceptable." Conclusion: The new polyvinyl siloxane impression material provided a significantly higher proportion of impressions free of bubbles and voids than the control polyvinyl siloxane material. Keywords: accuracy, final impression, fixed restoration, impression material, randomized clinical trial