Background: An oily calcium hydroxide formulation proved over the last years to be highly efficient in promotingbone regeneration in closed defects as periapical lesions, cysts, or post-extraction defects. The aim of the presentstudy is the assessment of the outcome of treatment of deep intrabony periodontal defects with an Open FlapDebridement) (OFD) + combination of {(30% Hydroxyapatite HAp + 70% β-Tricalcium Phosphate ranules mixed withan Oily Calcium Hydroxide Suspension (OCHS )} and compare the results with {(OFD) alone)}. The combination ofOCHS& TCP was used in humans with a sort of positive results, and more conduction of studies was recommended.Material and method: The sample of this study composed of sixteen patients; each had at least two intrabony defectteeth. For each patient, one tooth was treated by OFD only (control group 16 teeth) and the other teeth (studygroup 16 teeth) were treated with OFD + a mixture of (OSTEON II- Korea) granules comprise of (30% HydroxyapatiteHAp + 70% β-Tricalcium Phosphate) and OCHS (Osteoinductal®, Osteoinductal GmbH., Muenchen, Germany). Theclinical parameters that were measured and recorded included (Plaque index PLI, Gingival index (GI), Gingivalrecession(GR) , Bleeding on probing (BOP), probing pocket depth (PPD), clinical attachment level (CAL) andradiographical width & depth of the bony defect. These parameters were recorded before treatment (base line) &six months after the treatment.Results: The results after treatment revealed a highly significant reduction in all of the parameters except the PLI inboth study & control groups compared to baseline (p < 0.001). The clinical results were indicated that the studygroup showed significant reductions of PPD and CAL mean values more than improvements obtained by the controlgroup with significant difference (p < 0.05).Conclusions: An excellent postoperative improvement in clinical parameters was noticed in the study group morethan control group and the differences were significant. Thus the present study has revealed that the treatmentmodality of OFD + a combination of granules comprise of (30% Hydroxyapatite HAp + 70% β-Tricalcium Phosphate)mixed with oily Calcium Hydroxide suspension is successful, predictable and more beneficial than (open flapdebridement) (OFD) alone in the treatment of deep intrabony periodontal defects.