Effect of different surface pretreatments and adhesives on the load-bearing capacity of veneered 3-unit PEEK FDPs

Statement of problem. Polyetheretherketone (PEEK) can be used as a framework material for fixed dental prostheses (FDPs). However, information about the fracture load of veneered PEEK FDPs is still scarce. Purpose. The purpose of this in vitro study was to investigate the influence of different PEEK surface pretreatments and adhesive systems on the fracture load of 2 differently veneered FDPs. Material and methods. Four hundred eighty anatomically shaped 3-unit PEEK frameworks were milled, airborne-particle abraded with 50 pm alumina powder, and divided into 4 groups according to the following surface pretreatment (n=120): plasma treatment, etching with either sulfuric acid or piranha solution, and no further treatment. All groups were then allocated to 4 conditioning groups: visio.link, Ambarino P60, Signum PEEK Bond, or no conditioning. They were veneered with Signum Composite (n=15) or Signum Ceramis (n=15). Upon completion, the FDPs were thermally aged, and fracture loads and failure types were determined. Statistical analysis was performed with 3/2/1-way ANOVA with the post hoc Tukey HSD test (alpha=.05). Results. The highest fracture loads were achieved without treatment in combination with visio.link (737 +/- 138 N). The lowest values were obtained after piranha acid etching and conditioning with visio.link (277 +/- 71 N); both groups were veneered with Signum Composite. The results,. however, indicated no clear influence of either pretreatment or conditioning. With few exceptions, FDPs veneered with Signum Composite showed higher fracture load values compared to Signum Ceramis. After thermocycling, all FDPs showed cracks in the veneering composite resin material in the pontic region, regardless of the PEEK pretreatment or the adhesive system used. After loading, no fractures of the PEEK frameworks were evident in any FDPs, but chipping of the veneering material was observed. Conclusions. With respect to the fracture types after thermocycling, pretreatment, conditioning, or veneering resin cement did not affect the fracture results.