Objective: To evaluate the effect of bar constructed from conventional Cr-Co and digitally fabricated milled PEEK one ( subtractive method) on the retentive quality of tooth supported mandibular overdenture after predetermined insertion and removal cycles resembling patient daily cycles of usage. Materials and methods: A stone model for mandibular arch with remaining two canines was used . The canines were prepared into a dome shaped abutment. The prepared cast was duplicated into ten clear heat cured acrylic resin casts (5 casts in each group). Over-dentures were fabricated in the conventional way. The acrylic casts were digitally scanned using an extraoral 3D scanner. Virtual bar was designed on the Exocad software. the pattern was printed with 3D printer into the castable resin. The bar pattern was then conventionally cast into Cr-Co alloy. The virtual 3D (STL) file was sent to the milling machine to start milling of PEEK bar. the retention measured and 10 readings were taken for each model (3, 6, 9 and 12 months) respectively. Results: The values of retention were higher in case of PEEK bar compared to Metal one, in both groups there was gradual decrease in the retention values through the follow up period in both groups. Conclusion: Milled PEEK bar showed better retention values as compared to metal bar thus it can be widely used in CAD-CAM fabricated removable dental prostheses and dental attachments .
Keywords: Bar overdenture, Retentive clip, Milled PEEK bar, Cr-Co alloys, digital force gauge