© 2020. All rights reserved.Objectives: To assess differential effects of different materials combined with allograft on bone-to-implant contact and newly formed bone formation in dental implants with coronal defects histomorphometrically. Materials and Methods: The study was conducted on 24 male New Zealand white rabbits. Dental implants (3.0 χ 10 mm) were placed at the center of defects (9 mm diameter, 4 mm depth) created in the tibial bones of the rabbits. Graft (GF, n=8), graft + rifamycin (GR, n=8) and graft + black cumin oil via orogastric route (GB, n=8) were applied on the coronal aspects of the implants for 28 days. Undecalcified histomorphometric analyses were conducted on slides stained with toluidine blue. Results: Bone-to-implant contact was 46.57% ± 3.59% in the graft (GF), 67.12% ± 3.64% in the graft + rifamycin (GR) and 55.62% ± 4.37% in the graft + black cumin oil (GB) groups. The percentage of new bone formation at the defect area was 34.71% ± 4.11% in the graft, 55.37% ± 4.89% in the graft + rifamycin, and 45.75% ± 3.69% in the graft + black cumin oil groups. In terms of new bone formation and bone-to-implant contact, graft + rifamycin and graft + black cumin oil groups were significantly different from the graft group. The differences between the graft + rifamycin and graft + black cumin oil groups were also statistically significant. Conclusions: Allograft + rifamycin and orogastric black cumin oil were found to have positive effects on bone healing at sites with coronal defects. Rifamycin showed significantly greater favorable effects on bone-to-implant contact and new bone formation compared to black cumin oil.