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Clinical and histologic aspects of dental implants removed due to mobility.

BACKGROUND
Implant failures are rare but do occur. Mechanical factors are certainly important in implant failures; so are biologic, iatrogenic, and functional factors. Mobility is the cardinal sign of implant failure. Three major etiologic factors have been suggested for implant failures: infection, impaired healing, and overload. The aim of the present study was to histologically and histochemically evaluate the fibrous connective tissue found around failed dental implants removed due to mobility.


METHODS
In a 5-year period, 51 root-form implants were retrieved because of mobility and underwent histological examination. Thin ground sections were obtained from each implant.


RESULTS
Almost all implants had been inserted in posterior (premolar-molar) regions of both jaws. In all specimens, there was the presence of a 600 to 1,100 microm thick connective tissue between implants and surrounding bone. In every case, the surrounding bone was compact and highly mineralized, with well-structured Haversian canals and few areas of remodeling. No bacteria were found in the most coronal portion of the implants. A scarce inflammatory cell infiltrate was present in the connective tissue of some specimens. In about 10% of specimens, the epithelium tended to surround the perimeter of the implant.


CONCLUSION
Our histological results are consistent with the hypothesis that late failures of osseointegrated implants can be caused by a combination of poor bone quality, mechanical trauma to bone, and overloading forces.