The barrier between the keratinized mucosa and the dental implant - An experimental study in the dog

The present study was performed in order to examine the composition of the connective tissue that forms an attachment to a dental implant. 6 beagle do gs were used. All mandibular premolars were extracted. After 3 months of he aling, 6 fixtures - 3 in each side of the mandible - (Astra Tech Implants, Dental System(R) TiO blast; Astra Tech AB, Molndal, Sweden) were installed. After another 3 months of healing, abutment (Uni-abutment(R) 45; Astra Tec h AB, Molndal, Sweden) connection was performed and a plaque control progra m was initiated. The animals were sacrificed and perfused with a fixative t hrough the carotid arteries. Each implant site, including the implant and t he soft and hard periimplant tissues, was dissected, decalcified in EDTA an d further processed using a "fracture technique". The specimens were subseq uently embedded in EPON, cut with the microtome set at 3 mu m and the secti ons stained in PAS and toluidine blue. From the EPON-embedded blocks, ultra -thin sections were cut and electron micrographs were prepared. The detaile d histologic and morphometrical examinations were restricted to a 200 mu m Pride zone of connective tissue interposed between the apical border of the junctional epithelium and the bone tissue. In the analysis, this zone was further subdivided into 2 different units; (i) one central, 40 mu m wide un it (zone A) located immediately next to the implant surface, and (ii) one l ateral, 160 mu m wide unit (zone B) that was continuous with the central un it. The implant surface epical of the junctional epithelium and coronal of the bone crest appeared to be in direct contact with a connective tissue. Z one A of this connective tissue was characterized by its (i) absence of blo od vessels and (ii) abundance of fibrablasts which were interposed between thin collagen fibers. The more lateral zone B contained comparatively fewer fibroblasts, but more collagen fibers and blood vessels. There are reasons to assume that the fibroblast, rich barrier tissue next to the titanium su rface plays a role in the maintenance of a proper seal between the oral env ironment and the peri-implant bone.