Purpose: The purpose of this in vivo study is to compare the effect of both Conventional metallic partial denture and Telescopic partial denture on the bone height of the three main abutments in Kennedy class I patients with pier abutment. Materials and methods: fourteen patients with mandibular Kennedy' class I classification with pier abutment were divided into two groups, Group I received conventional removable partial dentures, while the other group received telescopic removable partial denture. The supporting structures of the removable partial dentures were clinically and radiographically evaluated, bone density and bone height were the evaluated parameters. After baseline recording following denture insertion, subsequent measurements were obtained at regular follow up appointments 3, 6, 9 months. Radiographic evaluation was performed using the Digora system, Acrylic template was constructed for each patient. The linear measurement system supplied by the software of the Digora machine was used for recording changes in bone density and bone height mesial and distal to the main three abutments. Results: Comparison was performed between vitallium and telescopic group using independent t test resulting in insignificant difference for all follow up intervals (P value > 0.05), Conclusion Conventional metal RPI clasp and telescopic removable partial denture were both clinically and biologically successful. However, Telescopic removable partial denture is superior to the conventional removable partial denture.