Aim:evaluating the retention, measuring the amount of stresses transmitted to the principal and pier abutments and ridge in mandibular Kennedy class II restored by milled (PEKK) partial telescopic over-denture as compared to that of milled chrome cobalt.Methodology: Both abutments were reduced to receive telescopic Co-Cr primary crowns and the usual preparation for class II partial denture was made on intact side. Twelve partial telescopic overdentures (PTO) frameworks were milled from two materials. Group I (GR I), six PTO frameworks were milled using Co-Cr, while the other six PTO frameworks of group II (GR II) were milled using poly –ether ketone ketone (PEKK). Each PTO was seated on its cast to be placed within chewing simulator where PTO was exposed to insertion/removal and loading cycles Retention was evaluated.Strains induced within both abutments and supporting ridge were measured using five strain gauges.Results: For chrome-cobalt PTO had significantly higher retention than that expressed by PEKK PTO framework. under both unilateral and bilateral loading, pier abutment received much more strains than that exerted on principal abutment, additionally distal surfaces of both abutments expressed higher significant strains than mesial surfaces. Under both unilateral and bilateral loading, chrome-cobalt PTO (GR I) framework exerted higher significant strains on proximal surfaces of abutments than that expressed by PEKK PTO (GR II) framework.
Conclusion: PEKK PTO could be a promising option in cases of Kennedy class II having pier abutment.