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.