Ultrastructure of the Interface Periodontal Tissue/Titanium Mini-Implant in Rat Mandibles

Objectives: Little is known about the behavior of the supporting periodontium (alveolar bone and periodontal ligament) in relation of the titanium mini-implant. The aim of the present study was to ultrastructuraly examine the interface between periodontal tissues and titanium mini-implants in rat mandibles. Methods: A titanium screw-type mini-implant (1.4mm x 1.2mm) was placed between the buccal roots of the lower first molar of twenty 3-month-old male Wistar rats. After 45, 60, 90 and 120 days of implantation the animals were killed, the mandibular portion removed, fixed and processed for electron microscopy. Results: The ultrastructural analysis revealed evident bone formation in all the samples. Some specimens with 45 days showed connective (osteoblast-like) cells, which were surrounded by a collagen-rich organic matrix. At the advanced times, the bone tissue reached the implant surface, exhibiting some osteocytes and the electron-opaque line ("laminae limitans") close to the interface. Adjacent to that region, an amorphous material or collagen fibrils in direct contact with the implant space were found. In the areas in which the implant was placed in contact with the periodontal ligament it appeared with its typical aspect. This reorganized its constituents around the implant over which they seemed to form a conspicuous cementum-like layer at longer times after implantation. Conclusion: Therefore, the areas in which the alveolar bone in contact with the implant surface revealed osseointegration took place in all specimens and where the periodontal ligament was in contact with the implant thus showed a conspicuous cementum-like layer at longer times after implantation.