Aim of this study was to evaluate influence of thermoplastic denture base material on plaque index and depth of gingival sulcus of implants supported mandibular overdenture. Patients and methods: Twenty completely edentulous patients were selected according to inclusion and exclusion criteria that affect implant success. Two implants were implanted in the interforaminal area of mandible following the two stages surgical protocol; patients were grouped into two groups Group I (TPG) patients received a complete mandibular overdenture constructed of thermoplastic poly amide denture base material and Group II (HCG) patients received a complete mandibular overdenture constructed of conventional heat cured acrylic resin, both groups are retained by ball and socket attachment system. Plaque index and depth of gingival sulcus were measured for each group after overdenture construction and every three months interval for 24 months. One-way ANOVA with post hoc turkey test was used for multiple time comparison. Results: the mean value of pocket depth between 2 groups [TPG - HCG] at different period has no statistically significant difference but statistically significant at a period of twenty four month <0.001* P-value. plaque index show statistically significant <0.001* P-value at all different periods. Conclusion: thermoplastic denture base overdenture has a superior benefit than conventional heat cured type as it give longevity of supported implant by enhancing peri-implant gingival health with reduced pocket depth and plaque index.