The socket shield technique preserves the buccal bone and gingival architecture in the aesthetic zone by deliberately leaving a fragment of the patient's own root in place when an immediate implant is inserted. It works well, but a basic question has stayed unanswered: what happens, mechanically, when the implant directly contacts that retained fragment, and how thick or wide should the shield be? This study used three-dimensional finite element analysis to find out.

Models of a maxillary anterior socket shield implant were built from cone-beam CT data. The residual root fragment was fixed at 1.5 mm thickness and 6 mm length, while its labial arc angle was varied across 60, 90, 120, 150 and 180 degrees. The simulation applied a 30 N·cm insertion torque and a 100 N occlusal load.

Under insertion torque, peak stress in the fragment fell steadily as the arc angle widened, from 101.9 MPa at 60 degrees down to 42.43 MPa at 180 degrees, with stress concentrating where the implant neck reaches its widest diameter. Periodontal ligament stress and fragment displacement also decreased with wider arcs. Under occlusal load the picture inverted: wider arcs raised stress in the PDL and cortical bone while lowering it in the fragment and implant. Cortical bone stress was lowest in the mid-range and climbed sharply at 180 degrees (64.51 MPa).

The synthesis is practical. A shield arc of roughly 120 to 150 degrees balanced these competing demands and offered the most favourable biomechanical environment. The authors are appropriately cautious: this is a static model, real loading is cyclic and fatigue effects were not tested, so clinical validation is still needed. Still, for surgeons choosing how much root to retain, the study turns an intuitive judgement into a quantified target.