Purpose: to evaluate bone height changes around distal abutments (canines) with two different framework materials for extracoronal attachment mandibular bilateral distally extended removable dental prosthesis (RDP) and compare patient satisfaction .
Materials and methods:

Twenty-eight mandibular Kennedy class I partially edentulous patients with remaining 6 anterior teeth were selected. For all patients splinting of remaining anterior abutments by porcelain fused to metal crowns, the RDP frameworks were designed by CAD and printed into 3-D resin pattern. The patients were randomly divided into two groups. Patients in group I received extracoronal attachment RDP framework fabricated from milled BioHPP PEEK while patients in group II received extracoronal attachment RDP framework fabricated from Cobalt -Chromium (Co-Cr) material. Digital radiography was used for vertical bone loss (VBL) assessment around canines at insertion, 6 and 12 months. Patient satisfaction was measured after 6 months using visual analog scale (VAS). Statistical analysis was done by t-test and Mann-Whitney.
Results: VBL significantly increased from T6 to T12 for both groups where (p=0.038 and 0.021) for PEEK and Co-Cr framework respectively. there was a significant difference in VBL between two groups at T12 only (p=0.012) where Co-Cr framework recorded significant higher VBL at T12 than PEEK. As for patients satisfaction, patients who received PEEK RDP frameworks were more satisfied as regards esthetic and comfort than patients who received Co-Cr RDP frameworks
Conclusion: Extracoronal attachment RDPs with PEEK frameworks showed less VBL than those with Co-Cr frameworks. Patients with PEEK frameworks were more satisfied than patients with Co-Cr frameworks