Purpose: The aim of this clinical study is to compare the effect of both definitive partial dentures and telescopic partial dentures on bone height changes around the terminal abutments in mandibular distal extension cases with pier abutment. Materials and Methods: Fourteen mandibular Kennedys Class I classification with pier abutment patients were divided into two equal groups. First group (I) received definitive metal-frame removable partial dentures (RPD), while the second group (II) received telescopic RPD. The supporting bone height around the terminal abutments was radiographically evaluated. Next to baseline recording following denture insertion, bone height measurements were obtained at regular recall follow-up appointments of 6, 12, 18 and 24 months. Radiographic evaluation was carried outusing the Digora system and customized acrylic template constructed for each patient individually. The linear measurement system supplied by the Digora machine software was utilized for recording bone height changes mesial and distal to the main terminal abutments. Results: Comparison was performed between definitive and telescopic groups utilizing independent t-test and resulted in differencesof no significant for all follow-up recalls (P value > 0.05). Conclusion:Definitive RPD and telescopic RPD appeared to besuccessful both clinically and biologically. However, Telescopic RPD proved to be superior to the definitive one regarding bone height measurements.