KERATINIZED MUCOSA (KM)

Keratinized mucosa is a term used to describe the masticatory mucosa that is present at many, but not all, implant sites. Keratinized mucosa extends from the margin of the peri‐implant mucosa to the movable lining (oral) mucosa. Keratinized mucosa is comprised of a lamina propria (fibrous connective tissue that contains fibroblasts and equal amounts of type I and type III collagen) that is covered by an orthokeratinized squamous epithelium. The width of the Keratinized mucosa at the facial/buccal side of teeth is, as a rule, about 1 mm greater than at contralateral implant sites. It is suggested that loss of crestal bone following tooth extraction is the main reason for dimunition of the Keratinized mucosa. The thickness of facial Keratinized mucosa, determined with a probe at the base of the PD, is greater at implants than at teeth (2.0 mm vs 1.1 mm, respectively).

The need for a minimum amount of keratinized mucosa to maintain peri‐implant tissue health is apparently a controversial issue. Several studies failed to associate the lack of a minimum amount of Keratinized mucosa with mucosal inflammation, while other studies suggested that plaque build‐up and marginal inflammation were more frequent at implant sites with < 2 mm of Keratinized mucosa.