The aim of the present in-vitro study was to assess the modes of failures under static load among titanium (Ti) and one- and two-piece zirconia abutments. The one- and two-piece zirconia abutment specimens were fabricated from pre-scanned Ti abutments. Twenty-one implant abutments and 21 implant replicas were equally divided into 3 groups as follows: (a) Group-1 (Titanium group); (b) Group-2 (one-piece zirconia abutment group); and (c) Group-3: two-piece zirconia abutment group). A 250,000-cycle linear fatigue load ranging between 10 N and 210 N was applied to all specimens using an all-electric dynamic test instrument. The specimens were loaded until they fractured. In all groups, assessment of mode of fracture was done on visual assessment by a trained and calibrated investigator. Prior sample-size estimation was performed; and sample distribution was assessed using the Kolmogorov and Shapiro tests. Screw fracture (n=7) and abutment bending at the apical part (n=7) occurred in the Ti group. In the one-piece zirconia group, screw and abutment fractures occurred in 7 and 7 cases, respectively. In the two-piece zirconia screw fracture (n=7) above the Ti zirconia junction (transgingival segment) and abutment fracture (n=7) were determined as the failure modes. In-vitro , the one-piece zirconia abutments are more fracture resistant than Titanium and two-piece zirconia abutments. From a clinical perspective, further studies are needed to determine the minimum static load value required to induce fracture of the one- and two-piece zirconia abutments.

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