BACKGROUND: Implant migration is an uncommon phenomenon defined as a change in the positional axis of a stable implant. This report describes a rare case of spontaneous macro-migration occurring during the healing phase in a site with poor bone density and evaluates its 8-year functional success. METHODS: A 53-year-old female required implant placement in the maxillary left first molar (Universal tooth #14) site with low bone density (residual bone height: 4.2-5 mm). Following sinus floor elevation using particulate bone grafting, a 4 mm × 13 mm implant was placed (insertion torque: 35 Ncm; initial implant stability quotient ISQ: 63). Digital image registration utilizing a rigid-body transformation algorithm was employed to quantify migration at 4 months, 8 months, and 8 years. RESULTS: Digital analysis confirmed a 12.8° mesial macro-migration within the first 4 months. Despite the shift, stability increased biologically (ISQ 63-78). A 15° angled abutment was used for prosthetic correction. At 8 years, the implant remained functionally stable with intact three-dimensional bone encapsulation on cone-beam computed tomography and minimal marginal bone loss. CONCLUSIONS: Spontaneous migration in low-density bone before graft maturation does not necessarily preclude successful osseointegration. Long-term stability can be achieved through prosthetic intervention. KEY POINTS: Clinical phenomenon: Spontaneous implant macro-migration can occur in low-density (Type IV) bone during the submerged healing phase, particularly when associated with immature particulate bone grafts. Diagnostic tool: Digital image registration utilizing open-source software is an effective method for clinicians to objectively quantify positional shifts and differentiate adaptive migration from pathological displacement. Treatment outcome: Dental implants undergoing significant spontaneous migration (up to 12.8°) can achieve successful osseointegration and 8-year functional stability when managed with appropriate prosthetic compensation using angled abutments.
Tsai et al. (Thu,) studied this question.