Abstract
Aim: This study purposed to evaluate the effect of partial denture framework material on both abutments' supporting structures and bone supporting residual ridge of bilateral free edentulous areas through evaluating CAD-CAM milled PEEK framework and PEKK one compared with the conventional cast Cobalt-chromium framework. Materials and methods: The study included eighteen participants with mandibular bilateral free end saddle. The abutments were evaluated clinically through measuring the probing depth. Cone beam Computed Tomography (CBCT) was used to evaluate radiographically the bone height supporting the abutments . Also, the bone height and bucco-lingual width of residual ridge at the area of missed 1st and 2nd molars were measured.
Results: The gr1 generally showed the highest value of probing depth that became significant from gr 2 and gr 3 at 12 and 18 months, however gr 2 and gr 3 expressed insignificant values from each other. Regarding bone height reduction of residual ridge, there was no significance between the three groups, however gr 2 showed the greatest reduction followed by gr 3 that was comparable to that of gr 1. But gr 2 expressed significant reduction bone width BL along all follow up periods, followed by values of gr 3 that were insignificant from gr 1.

Conclusions: Pekk RPD framework could be recommended as an alternative for cobalt –chromium preserving the bone of residual ridge and at the same time it looks like Peek is providing good esthetics with reduction of stresses on abutments .

Keywords: PEEK, PEKK, cobalt chromium, CAD-CAM