Purpose: Resolution of defects surrounding dental implants can be achieved through the placement of rough-surfaced implants with bone substitutes. The aim of this study was to evaluate the effect of biphasic calcium phosphates (BCP) on the healing of circumferential bone defects surrounding dental implants. Materials and Methods: The premolars were removed in four mongrel dogs, and three different types of experimental sites were created: BCP, control, and ungrafted sites. In all groups, implants were placed in the edentulous area. In the BCP group, gap defects with 2-mm diameters were surgically created around each implant and the defects were filled with BCP bone substitute. In the control group, gap defects were not made around the implants. In the sham surgery group, gap defects were prepared but were not filled with BCP bone substitute. The defects were evaluated histologically and histometrically after 8 and 16 weeks. One-way analysis of variance and the independent t test were used for statistical analysis (α = .01). Results: Histometric measurements in the groups after 8 weeks showed the smallest remaining defect depths (RDDs) in the control group (17%). The RDD in the BCP group (39%) was greater than in the control group, and the ungrafted sites group had the greatest RDD (62%). There was no difference in bone-to-implant contact among the groups. Histometric measurements at 16 weeks showed that the RDD in the ungrated sites group (57%) was greater than in both the control (12%) and the BCP (31%) groups. Conclusion: Within the limitations of this study, BCP bone substitute contributed to defect resolution and maintained space for new bone ingrowth before 8 weeks. No additional contribution to defect resolution by BCP was found after 8 weeks. Keywords: biphasic calcium phosphates, bone-to-implant contact, circumferential bone defect, implant, remaining defect depth