Sir, a 74-year-old patient was referred to the oral surgery department by her general dental practitioner. On consultation, the patient complained of a loose lower complete denture. She reported that she had undergone implant placement some 20 years previously in South Africa and that she had not attended for dental examination since.

Clinical and radiographic examination revealed a subperiosteal mandibular implant (Figs 1,2). The bar was firm and the patient reported that she was experiencing no pain. There were multiple mucosal dehiscences anteriorly and posteriorly, with the exposure of necrotic bone. There appeared to be some deposits of calculus associated with the abutments.

Figure 1: Intraoral views.
figure 1

Note dehiscences with bone exposure posteriorly, exposure of a screw in the lower left anterior region and calculus deposits around the posts

Figure 2: Radiographic view showing mandibular full arch subperiosteal implant, with anterior and posterior retaining screws.
figure 2

Note radiolucencies adjacent to the anterior screws. The generalised lack of close fit to bony surface is likely related to continued ridge resorption

Radiographic examination showed a metal framework spanning the entire edentulous mandible. It sat approximately 2-2.5 mm above the alveolar ridge. Due to the smooth bony border and the even loss across the mandible, this is most likely to be due to continued resorption over time rather than pathological bone loss due to infection. The framework was secured to the bone by four retaining screws: two anteriorly and two posteriorly. The mandible itself was atrophic, with radiolucencies evident around the two anterior retaining screws.

Complete subperiosteal implant placement was first described as a treatment for the atrophic mandible in the 1940s. A mucoperiosteal flap would be raised to allow an impression to be made of the surface of the mandible. CT scans were also used to allow CAD/CAM fabrication of the framework, negating the need for impressions. The framework usually rests on the mandible, with no penetration into the bone.

Due to the high success rates in atrophic mandibles of osseointegrated implants facilitated by the placement of autogenous grafts, subperiosteal implants are no longer used. However, as this case highlights, there may still be some in situ which could present to the general dental practitioner.