Fracture Strength and Failure Mode of Maxillary Implant-Supported Provisional Single Crowns: A Comparison of Composite Resin Crowns Fabricated Directly Over PEEK Abutments and Solid Titanium Abutments

Background: Polyetheretherketone (PEEK) temporary abutments have been recently introduced for making implant-supported provisional single crowns. Little information is available in the dental literature on the durability of provisional implant-supported restorations. Purpose: The objectives of this study were to evaluate the fracture strength of implant-supported composite resin crowns on PEEK and solid titanium temporary abutments, and to analyze the failure types. Material and Methods: Three types of provisional abutments, RN synOcta Temporary Meso Abutment (PEEK; Straumann), RN synOcta Titanium Post for Temporary Restorations (Straumann), and Temporary Abutment Engaging NobRplRP (Nobel Biocare) were used, and provisional screw-retained crowns using composite resin (Solidex) were fabricated for four different locations in the maxilla. The specimens were tested in a universal testing machine at a crosshead speed of 1 mm/minute until fracture occurred. The failure types were analyzed and further categorized as irreparable (Type 1) or reparable (Type 2). Results: No significant difference was found between different abutment types. Only for the position of the maxillary central incisor, composite resin crowns on PEEK temporary abutments showed significantly lower (p < 0.05) fracture strength (95 +/- 21 N) than those on titanium temporary abutments (1,009 +/- 94 N). The most frequently experienced failure types were cohesive fractures of the composite resin crowns (75 out of 104), followed by screw loosening (18 out of 104). According to reparability, the majority of the specimens were classified as Type 1 (82 out of 104). Type 2 failures were not often observed (22 out of 104). Conclusions: Provisional crowns on PEEK abutments showed similar fracture strength as titanium temporary abutments except for central incisors. Maxillary right central incisor composite resin crowns on PEEK temporary abutments fractured below the mean anterior masticatory loading forces reported to be approximately 206 N.