Implant supported overdentures--the Birmingham experience

The use of an implant retained overdenture with magnets offers a simple treatment approach to the problem of instability of the complete denture. Advantages with magnets include a simplified clinical technique and reduced lateral stresses on the abutments. This paper reports on a long-term study undertaken at Wordsley Hospital and Birmingham Dental teaching hospital in the West Midlands.

Twenty-one patients received implant-retained overdentures with magnets over a 5-year period. The average age of the patients was 63 years (range 44-83 years). Seventy-eight Astra (Astra Tech AB, Mölndal, Sweden) implants were placed: 17 patients had four, two had three and two had two implants placed.

During the 5-year study, 11 implants were lost, one from infection, and the remaining 10 were lost because of a failure of osseointegration. This equates to an 86% success rate which increases to 97% when implants shorter than 1 cm are discounted. Over this period, the average number of dentures constructed per patient was 2.3. The main reason for denture replacement was a loss of function of the magnets. When the steel casing around the magnets was breached, then corrosion resulted. The life expectancy of the magnets over the 5-year period was 77 weeks (+/-50 weeks). One denture was replaced due to problems of instability. Patient satisfaction with the treatment remains high, and all patients can now wear dentures satisfactorily.

The use of a magnet retained overdenture offers a simple reconstructive approach to complete denture instability. Methods are currently being investigated to improve the clinical function and durability of the magnets. The success rate with the implants remains good after 5 years in function.