Do strength of zirconia-abutment-interfaces depend on cement, zirconia type and titanium abutment dimensions?

OBJECTIVES: Part 1 of this study investigates the influence of zirconia types, chimney heights, and gingival heights on the strength of the zirconia-abutment-interface. Part 2 extends the analysis to include adhesive brands and macro-retentions. METHODS: In Part 1, the study utilized three zirconia types (700 MPa, 1000 MPa, 1200 MPa) to fabricate 234 screw-retained zirconia crowns with varying chimney heights (3.5 mm, 4.1 mm, 5 mm) and gingival heights (0.65 mm, 1.2 mm, 3 mm) of the titanium abutments. All adherend surfaces underwent sandblasting with aluminum oxide before cementation with a specific resin cement. In Part 2, the investigation of 240 screw-retained zirconia crowns focused on a single zirconia type (1000 MPa) with chimney heights of 3.5 mm and 5 mm and a gingival height of 0.65 mm of the titanium abutments, cemented with three different resin cements. All adherent surfaces underwent sandblasting with aluminum oxide before cementation, whereas 120 out of 240 abutments received additional macro retentions. Storage in water at 37 degrees C for 24 h preceded the tensile test. RESULTS: The study revealed a substantial impact of chimney height and zirconia type on the bond strength of the zirconia-abutment-interface. Neither adhesive brands nor macro retentions significantly impacted the bond strength. Fracture incidence was significantly influenced by gingival height and zirconia type in part 1, whereas in part 2 smaller chimney heights correlated with a higher fracture incidence. SIGNIFICANCE: This study contributes insights into the complex interplay of factors influencing the zirconia-abutment-interface. The results provide a foundation for refining clinical approaches, emphasizing the importance of chimney height and zirconia type in achieving successful anterior gap implant restorations.