In vivo Performance of an Experimental Core Ceramic for Posterior FPDs – 2-t-year Evaluation

Objectives: To test the hypothesis that three-unit fixed partial dentures (FPDs) of a high-strength core ceramic will exhibit good-to-excellent clinical performance (based on 11 evaluative criteria) and they will adequately resist fracture in posterior situations (excluding third molars) if fabricated with the proper connector size (4 mm x 4 mm). Methods: Baseline data were obtained for selected patients. Thirty ceramic FPDs were designed and then processed using the heat-pressed technique and the experimental core (EXC) ceramic. Connector heights and widths were measured for each FPD. The cement was selected based on a random table and was either a reinforced glass ionomer cement (Protec CEM, Vivadent) or a dual cure resin cement (Variolink, Vivadent). Patients were recalled after cementation (one year and two years) and evaluated using 11 clinical criteria. FPDs were examined by two independent clinicians and rankings for each criteria were made from 1 to 4 with 4=excellent and 1=unacceptable. Results: Two out of the thirty ceramic FPDs fractured within the two-year evaluation period representing a 93.3% success rate. One FPD fracture was associated with the subject having the greatest clenching force (1031N) while the other had a connector height of only 2.9 mm. All criteria were ranked good to excellent during the second year recall for all the remaining FPDs except for one where there was some sensitivity to cold and percussion. Poor tissue health for one patient during the first year recall resolved during the second year possibly because of more detailed oral hygiene instructions. Conclusion: The performance of the EXC is promising with a 6.7% fracture rate. Further evaluation with a larger sample size and longer duration is necessary to determine the success rate of the EXC ceramic. This study was supported by Ivoclar, Vivadent Corporation.