Primary implant stability is central to predictable osseointegration and long-term implant success. While conventional subtractive osteotomy remains a reliable approach in ridges of adequate width, osseodensification has been proposed as a bone-preserving alternative, particularly in narrower ridges. However, direct intra-patient comparisons under contrasting ridge conditions remain relatively limited. This report describes a 35-year-old systemically healthy female presenting with bilateral mandibular first molar edentulism. Preoperative cone-beam computed tomography demonstrated a ridge width of 7 mm with D3 bone density at site 46 and 5 mm with D2 bone density at site 36. A flapless conventional osteotomy was performed at site 46, whereas site 36 underwent flap elevation followed by osseodensification-assisted preparation to allow controlled ridge expansion. Implant stability was assessed using resonance frequency analysis. Primary stability measured 72 implant stability quotient (ISQ) at site 46 and 75 ISQ at site 36. At 16 weeks, both implants demonstrated secondary stability values of 71 ISQ. Radiographic evaluation at prosthetic loading revealed minimal crestal bone remodeling (≤0.5 mm at all measured surfaces), with no evidence of peri-implant radiolucency. Healing progressed without complication. Within the inherent limitations of a single-patient case report, osseodensification in a narrow ridge achieved stability comparable to flapless conventional osteotomy performed in an anatomically favorable ridge.