Purpose: the aim of this study was to compare the effect of two attachment designs (Bollard coping) which is a resilient coping and (conventional rigid telescopic crown) on implant stability, in mandibular implant supported over-denture, opposing a maxillary conventional complete denture, over a follow-up period of 6 months. Materials and Methods: Twenty completely edentulous patients were selected for this study. The patients were randomly divided into two groups each one composed of ten patients. Group I received Bollard coping in implants supported mandibular over-denture opposing maxillary complete denture, while group II received conventional telescopic crown in implant supported mandibular over-denture opposing maxillary complete denture. The stability of implants for both groups was measured by using the Osstell ISQ device at base line, three months and six months after insertion of prostheses. Result: In Group I ( Bollard coping ) the mean ISQ values showed an increase with time with ISQ values of 60.3± 4.87 , 67.1± 2.42 and 71.5 ± 1.71at Baseline , after 3 months and 6 months respectively such an increase was statistically significant ( P-value ≤0.01 ) In Group II (Conventional telescopic crown) the mean ISQ values showed an increase with time with ISQ values of 61.7± 5.06, 65.7± 3.30 and 68.4± 3.53 at Baseline , after 3 months and 6 months respectively such an increase was statistically significant ( P-value =0.004) Conclusion: The use of Bollard coping in implant retained over-dentures proved to be a favorable treatment option , where it demonstrated an increased in implant stability quotient more than conventional telescopic crown.