| 0392 Fatigue Analysis of Individualized Zirconia Implant-Abutments and Crowns | ||
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M. CABRERA, E. HEGENBARTH, V.P. THOMPSON, E.D. REKOW, and C.F. STAPPERT, New York University, USA Objectives: To investigate the failure modes and reliability of individualized Y-TZP abutments* and zirconia-crowns* using mouth-motion step-stress fatigue and to determine the influence of manual grinding adjustments of zirconia abutments on fatigue resistance. Methods: 20 similar Y-TZP-abutments* indicated for a maxillary central incisor were CAD/CAM fabricated. 10 abutments remained original machined (Group-OR), whereas 10 abutments (Group-IN) received a standardized grinding-adjustment (diamond-burs, grit-80-µm) to mimic in-vivo preparation adaptation of the abutment-collar to the marginal-gingival-contour. All abutments were scanned individually and Y-TZP-Procera*-copings were produced. Zirconia-crowns (NobelRondo*-veneered) were cemented conventionally (KetacCem, 3M-ESPE) on abutments screwed to Replace-Select-Tapered* implants (RP4.3x16mm) (*NobelBiocare). A single load to failure test was performed to estimate initial fracture resistance. Mouth motion (1.5-2Hz) step-stress accelerated fatigue testing (ELF-3300, Bose) was employed with three stress-time-varying profiles. Ultimate failure was defined by abutment or screw fracture. Specimens were inspected (polarized-specular-reflection-light-microscopy) at regular intervals to visualize crack propagation and failure mode. Reliability software (Alta Pro, Reliasoft) was employed. Preliminary results: Off-axis single-load-test resulted in porcelain delamination and abutment fracture (~660N). Radial crack propagation occurred in the veneering porcelain during fatigue. Ultimate failure occurred by abutment (A) or screw (S) fracture; ratio Group-OR A=5/S=4, Group-IN A=3/S=6. During fatigue specimens resisted max loads as follows: Group-OR-300-to-600N, Group-IN-400-to-575N. Weibull-stress-level-probability-curves were calculated and the reliability (2-sided at 90.0 % confidence bounds) for 50K cycles and a 300N load indicated a value of 0.73(0.91/0.40) for all specimens (n=20). Confidence bounds for the two test groups overlapped and therefore, did not demonstrate a significant difference. Conclusion: Based on current data, implant-supported zirconia crowns and abutments exhibit appropriate fatigue resistance, even after abutment-grinding-adjustments. Supported by Nobel Biocare, Goteborg, Sweden. christian.stappert@nyu.edu | ||
| Seq #72 - Ceramics: Mechanical Properties and Fracture Behavior 2:00 PM-3:15 PM, Thursday, March 22, 2007 Ernest N. Morial Convention Center Exhibit Hall I2-J | ||
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