The reliability of implant-retained hinging overdentures for the fully edentulous mandible. An up to 9-year longitudinal study.

The treatment of fully edentulous mandibles by means of implant-supported hinging overdentures has become a routine therapy, although long-term data on the success rate of implants and prostheses are lacking. This longitudinal study examined 207 consecutively treated patients who received, during the past 10 years, 449 Brånemark implants to retain a mandibular hinging overdenture, mainly on a Dolder bar. Clinical parameters and standardized radiographs taken at every recall visit with an interval of 6-12 months were used to judge the implant rigidity in the jawbone, the marginal bone level, and attachment level changes. The cumulative implant failure rate at 9 years was 3%. After loading, implant loss was concentrated during the first 12 months, with only one failure observed at 22 months. A radiographically determined bone loss of 0.7 mm was observed during the first year. From the second year, a mean annual bone loss of 0.05 mm occurred. The attachment loss, calculated as the sum of probing pocket depth plus the recession, was 0.07 mm/year and paralleled the changes in marginal bone level over time. The rigidity of the implant-bone interface revealed an increase over time, as shown by a decrease in Periotest values. The bar-overdenture complications were related to relining (23%), untightening of the retention clip (10%), and renewal of the prosthesis (7%). When magnets or ball attachments were used, more aftercare was needed. Fracture of the antagonistic full denture occurred in 7% of patients. The present data indicate that the mandibular overdenture therapy on two (Brånemark) implants is a very reliable and cost-effective treatment, even in a long-term perspective for the fixed full mandibular prosthesis and especially in elderly patients.