A 3- to 6-year study of overdentures supported by hydroxyapatite-coated endosseous dental implants

The purpose of this study was to evaluate the clinical effectiveness of hydroxyapatite-coated cylindrical implants to support overdentures. These implants were placed between 1990 and 1994 and have been followed up over a period of 3 to 6 years.

One hundred thirty-nine Calcitek dental implants were placed in 43 patients to support 14 maxillary and 30 mandibular overdentures. Standardized clinical review procedures were used.

At exposure all the implants were found to be osseointegrated. To date only 7 implants (5%) have completely failed and two associated overdentures (5%) have been lost. The cumulative survival rate of all implants over 6 years was 92%. However, if failure is defined by the loss of more than 4 mm of cervical bone, 33 implants could be classified as being in the process of failing. Using these figures, interval success rates as low as 82% were found by year 6, and the cumulative success rate would fall to 39%. Maxillary survival and success rates were significantly lower than mandibular rates, at 38% and 10%, respectively, by year 5.

Failure rates were higher in the maxillary arch, in poor quality bone, in smokers, and where implants were opposed by a natural dentition or an implant-supported prosthesis. The results suggest that the cervical bone level adjacent to the Calcitek cylindrical hydroxyapatite-coated implant failed to establish a steady state, particularly in the maxillary arch. Doubts remain regarding the long-term prognosis of these cylindrical implants.