Pinhole Regenerative Therapy (PRT) following minimally invasive non-surgical periodontal therapy (MINST) in the treatment of intrabony defects associated with Stage III Grade B periodontitis. Eligible patients with 2- or 3-wall intrabony defects will be randomly allocated to the study groups. Clinical outcomes, including probing pocket depth (PPD) reduction and clinical attachment level (CAL) gain, together with radiographic bone defect fill assessed by periapical radiographs and CBCT, will be evaluated over a 6-month follow-up period to determine the effectiveness of the proposed minimally invasive regenerative approacا