Objective: To compare the fit of an implant bar prepared from a master model to the fit on ten working casts, constructed from two elastomeric impression materials. Methods: Master and working models were used to simulate a case with five transmucosal abutment analogues in the anterior mandibular region. The implant component used was Paragon® System. A silver palladium alloy implant bar was constructed and seated upon the master model until an excellent fit was achieved. The marginal fit was evaluated on ten working models fabricated from polyether (Impregum®) and silicone (Aquasil®). The implant bar was seated on each working model and sectioned to provide four bar lengths. Four experts evaluated the bars for passive fit. Fit was evaluated by: direct vision, 20x stereomicroscope, and digital movements. Results: All four experts accepted the four-implant bar lengths on the master model. All evaluations of working models obtained from hydrophilic addition silicone materials yielded a higher percentage of acceptance, 75% (60/80), than those obtained from polyether impression material. A total of 99% (79/80) of the working models obtained from polyether were rejected by the experts; one working model using digital movement evaluation was accepted. Kappa Statistics were calculated to determine the reliability of the evaluation techniques: direct visual versus stereomicroscope (.96), direct visual versus digital movement (.85) and digital movement versus stereomicroscope (.81). Odds ratio were calculated to determine the effect of bar lengths on the evaluator's acceptance. The longer the bar length, the higher the probability to be rejected when compared to the reference length; bar lengths >25mm, p=0.065. Conclusion: A statistically significant difference was obtained for fit p=0.009 in favor of the models from silicone over polyether impression materials. We recommend a maximum bar length of approximately 25mm in order to decrease the need for bar sectioning procedure.

Back to the Prosthodontics Research Program
Back to the IADR/AADR/CADR 82nd General Session (March 10-13, 2004)

Top Level Search