Marginal Adaptation and Failure Load of Hybrid Ceramic Crowns with Shoulder and Feather-Edge Margin Designs After Thermomechanical Fatigue

Authors

1 Assistant Lecturer of Fixed Prosthodontics, Faculty of Dentistry, Sinai University, Egypt

2 Professor of Crowns and Bridges, Faculty of Dental Medicine for Girls, AlAzhar University, Cairo, Egypt

3 Lecturer of Crowns and Bridges, Faculty of Dental Medicine for Girls, AlAzhar University, Cairo, Egypt

4 Postdoctoral Research Fellow at the Department of Forest Resources Management, Faculty of Forestry, University of British Columbia, Canada

Abstract

Purpose : To estimate the marginal adaptation and failure load of hybrid ceramic “Vita Enamic” crowns with two margin designs; shoulder and feather-edge after thermomechanical fatigue. Materials and Methods: A typodont mandibular first molar was selected. Exocad software was used to perform standard preparations of Vita Enamic ceramic crowns with two different margin designs; the first was prepared with a shoulder margin configuration, group (S) and the second was prepared with a featheredge margin configuration, group (FE). Each prepared design was duplicated 15 times to form a total of 30 epoxy resin replicas ["n=15" for shoulder (S) group and "n=15" for the feather-edge (FE) group]. A total of 30 Vita Enamic crowns (N=30) were designed and constructed using CAD/CAM machine. All crowns were adhesively bonded to their corresponding epoxy resin dies by using self-adhesive resin cement and then subjected to thermomechanical fatigue. Finally, perpendicular marginal space and failure load were gauged. Results: Shoulder margin "group S" registered lower average perpendicular marginal space (68.075±5.60μm) as well as a higher average failure load value (1676±80.34N) compared to feather-edge margin "group FE'' (84.138±2.78μm) (1355.39±274.85N) respectively. Conclusion: For Vita Enamic ceramic crowns; both marginal adaptation and failure load of different margin designs conform to the range that is clinically approved.

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