<p>We investigated the effect of synthesized collagen model polypeptides consisting of a proline‐hydroxyproline‐glycine (poly(PHG)) sequence combined with porous alpha‐tricalcium phosphate (α‐TCP) particles on bone formation in a mandibular canine defect model. The porous α‐TCP particles were mixed with a poly(PHG) solution, and the obtained sponge was then cross‐linked and analyzed by scanning electron microscopy. The optimal mixing concentration of α‐TCP granules and the poly(PHG) solution was decided to be 0.15g/mL by compression testing. The osteoblastic differentiation with the ALP activity of human mesenchymal stromal cells (hMSCs) cultured on the poly(PHG)/α‐TCP was slightly greater than that of hMSCs cultured on the poly(PHG). Mandibular defects were analyzed in healthy beagles using micro‐computed tomography and histological evaluation. At 2 and 4 weeks, the volume density of new bone was grater in the poly(PHG)/α‐TCP group than in the group with only poly(PHG) (p<0.05); however, there was no difference at 8 weeks (p>0.05). Histological evaluation at 4 weeks after implantation revealed that the poly(PHG) had degraded and that newly formed bone was present on the surface of the α‐TCP particles. This study demonstrates that the composite created using porous α‐TCP particles and poly(PHG) is sufficiently adaptable for treating the mandibular canine defect model. (J Osaka Dent Univ 2023; 57: 223‐231)</p>