Aim of study: The objective of this study was to evaluate the clinical & radiographic effects of using bone graft (Nano bone graft) as a regenerative technique in one side with vertical bone defect in comparison to sub-gingival mechanical debridement in the other side. Materials and methods: In a split-mouth study design, 10 patients having bilateral intra-bony periodontal defects with radiographic vertical bone loss and associated probing depth ≥ 7mm. Selected sites were randomly divided into two groups. In group I non-surgical periodontal therapy was done, in group ii, Modified Widman flap with application of Nano-bone graft was done. Clinical and radiographic parameters were recorded at baseline, 3-months and 6-month post-opertavely.Results: Both treatment groups showed a significant probing depth(PPD) reduction, clinical attachment gain, increase bone density 6-month after surgery compared with baseline, however, Nano-bone group showed more bone fill at 3 months when compared to nonsurgical group then it decrease to almost equal to nonsurgical group at the end of the study . Conclusion:the use of Sub-gingival debridement is more advisable than modified Widman flaps and Nano-bone application as it gives the same clinical outcome with less cost and less harm for the patient.•Clinical recommendations: Further studies are needed with larger sample size and longer duration to detect the action of Nano-bone graft in the treatment of vertical bony defects in comparison to sub-gingival mechanical debridement.