Implants · patient case question
Where are bilateral implants optimally placed for an implant-retained MANDIBULAR overdenture?
Patient case: Maintenance of a screw-retained implant prosthesis
Patient: Male, 59 years old
Chief Complaint: Attends for review of a screw-retained implant-supported prosthesis placed eighteen months ago.
Background: Non-smoker. Well-controlled hypertension. Good plaque control.
Current Findings: The prosthesis is stable and the peri-implant tissues are healthy, with no bleeding on probing and no radiographic bone loss beyond expected remodelling. He asks what ongoing care the restoration will need.
Show answer and explanation
Correct answer: B. In the canine regions
- A. Second premolar sites sit close to the mental foramina and risk nerve injury, and the anterior ridge remains unsupported.
- B. CORRECT. The canine regions are the standard sites for a two-implant mandibular overdenture. The bone is dense and adequate in volume there, the sites lie anterior to the mental foramina so the mental nerve is safe, and the inter-implant distance gives a favourable anteroposterior spread for retention and stability while permitting rotation about the interconnecting axis so the posterior ridges continue to share the load.
- C. The posterior mandible carries the inferior alveolar canal and is often severely resorbed. Posterior implants in an overdenture also create a rigid, cantilevered scheme.
- D. Implants placed too close together in the incisor region give a very short anteroposterior spread and poor resistance to rotation.
Note: The two-implant mandibular overdenture is widely regarded as the minimum standard of care for the edentulous mandible. Note that a MAXILLARY overdenture generally requires four or more implants because of the poorer bone quality.