In vitro comparison between some mechanical properties of CAD/CAM polyetheretherketone and conventional cobalt chromium frameworks in removable partial denture

Objective: To evaluate the fitting, flexure strength and clasp retentive force and deformation of RPD frameworks made from cobalt chromium and polyetheretherketone. Materials and Methods: Mandibular cast with a unilateral bounded saddle was fabricated, scaned and transferred to Exocad software. Twenty frameworks were fabricated and divided into two groups, group I for PEEK fabricated by CAD/CAM milling technique and group II for Co-Cr fabricated by conventional lost wax technique from 3-D printed resin pattern. Framework fitness was evaluated by replica technique and weighing by a digital analytical balance. Retention was measured by applying withdrawal force to frameworks by a universal testing machine. Deformation of clasps was evaluated by measuring the distance between 2 reference points on the tips of the retentive and reciprocal arms before and after repeated insertion/removal cycles by a chewing simulator. Biaxial flexure strength was determined using a piston-on-3points technique. Results: PEEK material group showed more adaptation than metal. For retention and deformation, metal group recorded higher retention mean value than PEEK but due to the higher deformation in metal there was no significant difference in retention after one year of use simulation. Metal group recorded higher flexure strength than PEEK. Conclusions: Within the limitations of this study, it could be concluded that milled PEEK frameworks have better tissue surface adaptation, totally acceptable retention forces reaches between 9 and 12N, and flexure strength between 137 and 144MPa. which is valid for clinical use.