Objective: This study was conducted to evaluate the crestal bone height changes of immediately loaded Porous trabecular tantalum dental implants (PTTM ) and screw shaped titanium implants in mandibular two implant overdenture with CBCT scan. Subjects & Methods: Fourteen completely edentulous patients were rehabilitated with maxillary complete dentures & immediately loaded mandibular two implant overdentures. Patients were selected according to certain inclusion & exclusion criteria. Conventional maxillary & mandibular complete dentures were constructed for all patients. Patients were then randomly divided into two equal groups according to the implant type. Group (I-Intervention Group): TM implants & Group (II- control Group): Conventional titanium Screw implants were utilized. Implants were installed in the mandibular interforaminal region. Implants were immediately loaded with ball retained overdentures. Radiographic Evaluation of crestal bone height changes around the implants was made with CBCT scan; at the denture insertion visit, 6, 12 , & 24 months after denture insertion. Data were collected, tabulated & statistically analyzed. Results: All patients were satisfied with their implant overdentures, No implant loss were recorded during the follow-up Period. The results of this study had revealed that the crestal bone height gradually decreased throughout the study period in the two studied groups. The mean values of crestal bone loss were (0.497mm± 0.161, 0.362mm ±0.045, 0.120mm.±0.13, 0.9 mm±0.67) and (0.65mm± 0.076 , 0.338mm±0. 047, 0.75 ±0.407, 1.20 ±0.108) in group I & Group II respectively at 0-6 month, 6- 12 month, 12- 18 month and from 0-24 month intervals. On comparing the studied Groups: The crestal bone loss was greater in Group (II) than Group (I) along the whole follow-up intervals. In the 1st & 2nd follow -up intervals; (0-6month & 6-12 Months) bone loss was greater in Group (II) than Group- I with statistically insignificant difference (P-values 0.069 ns &0.400 ns respectively). However, in the 3rd interval (6-12months) & (12-18 months) and( 0-24months), bone loss was significantly higher in Group-II than Group-I; with (P=0.000*). Conclusions: Within the limitation of the current study: Trabecular Tantalum Dental Implants (PTTM) may induce less crestal bone loss than conventional screw-shaped titanium implants in immediately loaded mandibular implant overdentures.