###### Abstract
Another study has confirmed the ability of PEKK to restore temporary crowns and bridges; PEKK not only offers comparable results to cobalt-chrome (CoCr) restoration but also has an esthetic advantage [10]. [PERSON] et al. reported on a case of an implant-fixed prosthetic restoration with a framework fabricated using PEKKTON(r) in a patient with a fully edentulous maxilla and partially edentulous mandible, though they also considered it suitable for long-term provisional restoration [1]. Thus, there are doubts as to whether the PEKK framework is durable enough for a definitive implant-supported fixed partial prosthesis. A previous study reported that the fracture load resistance of PEEK-made three-unit FDPs is 1383 N, indicating that PEEK might be an appropriate alternative material for FDPs, especially in load-bearing areas [11]. In 2016, [PERSON] reported similar results in a study that examined the fracture strength of three-unit implant-supported FDPs with excessive crown height fabricated from different materials. The mean fracture loads for Ni-Cr, zirconia, and PEEK prostheses were 5591, 2086, and 1430 N, respectively. The authors concluded that although the PEEK framework presented the lowest structural strength, it was still capable of withstanding bite force in the molar region, thus being sufficient for clinical application [12]. The fracture strength of three-unit posterior unveneered bridges made of PEKK presented a value greater than 1100 N; on the other hand, veneered bridges had a value greater than 2500 N. However, as these results were presented by the manufacturer, further laboratory and clinical studies are required to determine whether this framework is suitable for clinical use. Marginal adaptation is another important factor that determines the longevity of dental restorations. A misfit between the framework prosthetic and implant platform or abutment could result in improper stress distribution or a higher amount of stress on the bone-implant interface and underlying structures, leading to mechanical and/or biological complications [13]. As has been reported by many authors, polymer base materials may show creep deformation related to temperature, time, and loading due to their mechanical properties [14]. Applying PEKK as a structural material may lead to deformation under long-term loading and compromise the fit of the framework to the implant. Clinical studies are typically time-consuming and expensive, and the standardization of the test parameters is difficult. However, static fracture strength tests in isolation do not represent a clinical situation, as the restoration service in an oral cavity is generally subjected to dynamic, repetitive loading. Therefore, in vitro dynamic loading tests allow for the evaluation of dental restorative systems under clinically relevant conditions while saving evaluation time. The purpose of this in vitro study was to investigate the fractural strength of three-unit fixed partial prosthesis frameworks fabricated from PEKK as well as the marginal integrity of the PEKK framework after a simulation of five years of clinical service. The null hypothesis is that PEKK is suitable for use as a framework material with comparable durability to the metal-based gold standard; thus, mechanical loading would not affect the marginal fit of a restoration formed from PEKK.