Background and Objective: The concept of immediate occlusal loading with dental implants offers several advantages. In this research, the effect of type of restoration on Osseointegration rate of dental implants was histologically evaluated. Materials and Methods: Three months prior to implantation, the lower premolar teeth of 15 dogs were extracted. Then, 3 to 4 Maestro™ implants were placed in the healed extraction sites for each dog (n=48). Dividing the dogs into 3 groups, the implants were either loaded 48 hours later, with metallic or prefabricated acrylic crowns, or were left unloaded until the time of sacrifice. Three months after implant insertion, the animals were sacrificed and the samples were investigated to define the Osseo integration rate, lamellar and woven bone percentage and local inflammation of the regenerated bone. Results: No significant difference in the observed criteria was observed among the three groups (p>0.05); however, the unloaded group had the highest osseointegration rate and the group with metallic crown loaded had the least. The prosthesis type had no significant effect on the implant success rate (p>0.05). Lamellar and woven bone percentage of regenerated bone also did not differ in the three groups (p>0.05). One implant from each group failed in this study. Conclusion: Compared to unloaded implants, bone regeneration seems to have similar histological characteristics around immediately loaded dental implants and if properly carried out, these two kinds of restoration materials do not seem to affect the osseointegration and the bone regeneration process.