Some characteristics of periimplant tissues. Experimental studies in the dog

Abstract

The aim of the present experiments was to analyze aspects of the marginal tissues at implants which (i) differed with respect to design, installation technique and abutment material (ii) were challenged to repeated break-up of the zone of connective tissue integration and (iii) were exposed to plaque formation. The beagle dog model was used. 3 months prior to fixture installation all mandibular premolars were extracted. The implants were monitored during a six month period after abutment connection. At the end of each experiment a clinical examination, including assessment of plaque and soft tissue condition was performed, radiographs obtained and biopsies harvested. The biopsies were prepared for histometric and morphometric analyses. The peri-implant soft tissue consistently was comprised of two units, one epithelial and one connective tissue unit. A well-keratinized oral epithelium was continuous with a junctional epithelium that faced the implant. This junctional epithelium extended to a distance of about 2 mm apical of the mucosal margin. The connective tissue portion that was located between the bone crest and the junctional epithelium ( zone of connective tissue integration ) was dominated by collagen. In a narrow tissue portion close to the implant, the majority of the collagen fibers were attached to the periosteum and ran a course parallel to the surface of the implant. The vertical dimension of the "zone of connective tissue integration" varied between 1.0 and 1.5 mm, when formed adjacent to a titanium or a ceramic surface. When gold or dental porcelain was used in the abutment part of the implant or when the connective tissue attachment was disrupted by repeated dis- and re-connection of the abutment, the epithelium migrated "apically", bone resorption occurred and the "zone of connective tissue integration" was formed to the titanium surface of the fixture. The structure and composition of the peri-implant tissues that formed after a submerged or nonsubmerged installation technique did not differ. 5 months of plaque formation at different implant systems, resulted in the establishment of inflammatory infiltrates in the marginal portions of the periimplant mucosae. These lesions resided in a connective tissue compartment lateral to the barrier epithelium.