In vitro performance of implant-supported monolithic zirconia crowns: Influence of patient-specific tooth-coloured abutments with titanium adhesive bases.

OBJECTIVE: To investigate the influence of the combination of patient-specific abutments and titanium adhesive bases on the long-term in vitro performance of anterior crowns. METHODS: Ten systems of screw-retained implant and adhesive base combinations (n=8/group) were restored with zirconia or polyetherketone (PEEK) abutments and identical full-anatomical zirconia crowns. For simulating clinical anterior loading, implants were fixed at an angle of 135 degrees and submitted to prolonged thermal cycling and mechanical loading (TC: 6x3000 cycles, 5 degrees C/55 degrees C; ML: 100N, 3.6x10(6) cycles) to cause and register fatigue failure. Failed restorations were examined by means of scanning electron microscopy. Surviving restorations were loaded to fracture. Data (mean+/-standard deviation) were statistically analyzed (ANOVA; Bonferroni; Kaplan-Meier-Log-Rank; alpha=0.05). RESULTS: Seven systems survived TCML without any failure. The other three systems showed loosening and fracturing of the screw (0.4-1.6x10(6) loadings) or debonding between base and abutment (0.002-3.4x10(6) loadings). None of the systems showed any fracture of the crown or failed bonding between abutment and crown. The Log-Rank test showed significant (p=0.000) differences. Fracture data significantly varied (ANOVA p=0.000) between the individual systems (minimum: 371N; maximum: 763N). Failures were mostly caused by bending or fracturing of the screw and in three cases by fracture of the abutment. CONCLUSIONS: Anterior implant-supported zirconia crowns on titanium adhesive bases and bonded patient-specific zirconia abutments provided good in vitro performance and high fracture resistance. Sufficient high torque moments and early re-screwing may be advised. CLINICAL RELEVANCE: Most adhesive base and abutment combinations may be appropriate for anterior application. Individual improvements may contribute to enduring success.