PERI‐IMPLANT MUCOSA

Most information regarding the structural features of the peri‐implant mucosa is derived from animal studies using dog models. In such studies implants were placed in the edentulous ridge (alternatively, the fresh extraction socket), the outer osseous part of which was covered with masticatory mucosa. It was also shown that the healed peri‐implant mucosa on the buccal aspect averaged about 3 to 4 mm high when measured from the mucosal margin to the crest of the peri‐implant bone. In addition, this mucosa contains a core of connective tissue, mainly comprised of collagen fibers and matrix elements (85%), comparatively few fibroblasts (3%), and vascular units (5%). The outer (oral) surface of the connective tissue is covered by an often orthokeratinized epithelium. The portion of the peri‐implant mucosa that is facing the implant (abutment) contains two distinct parts, a “coronal” portion that is lined by a thin barrier epithelium (similar to the junctional epithelium of the gingiva) and sulcular epithelium, and a more “apical” segment in which the connective tissue appears to be in direct contact with the implant surface. This apical portion of the peri‐implant mucosa is designated zone of connective tissue adhesion.

In the connective tissue immediately lateral to the barrier and sulcular epithelium, a delicate plexus of vascular structures, similar to the dentogingival vascular plexus, is consistently present, while the connective tissue adhesion zone appears to harbor only limited amounts of vascular structures. At implants placed into masticatory mucosa, the main collagen fiber bundles are anchored in the crestal bone and extend in a marginal direction parallel to the surface of the metal device. It is assumed that circular fibers may also be present in this type of peri‐implant mucosa.

Moon et al. analyzed under electron scanning microscope the zone of connective tissue adhesion confined to a 200‐μm wide zone of the connective tissue facing the implant. The findings demonstrated that the adhesion includes two distinct layers: one inner layer, about 40 μm wide, which harbors large amounts of fibroblasts (32% of volume) that appear to be in intimate contact with the surface of the implant; and one outer layer, about 160 μm wide, that is dominated by collagen fibers (83%), smaller amounts of fibroblasts (11%), and larger volumes of vascular structures (3%).

Valid histologic information is not currently available regarding the peri‐implant mucosa when implants are placed in non‐keratinized lining or alveolar mucosa.