Although the periodontium and peri-implant supporting structures share similar histo- logic and clinical features, there are several fundamental differences between the anchorage and attachment of teeth and implants. A key difference is that there is no periodontal ligament or cementum around dental implants, with the alveolar bone in direct contact with the implant surface. As is the case with teeth, the transmucosal component of implants needs to provide a physical and physiological barrier between the external oral environment and the underlying tissues. The implant- mucosa interface also includes a sulcus resembling that associated with teeth, as well as an attachment apparatus. Indeed, the architecture of the supra-alveolar transmucosal components, consisting of a sulcus, junctional epithelium, and connective tissue attachment, is simi- lar around implants and teeth. Although both the transmucosal component of implants and the transgingival component of teeth have a sulcus (in health) or pocket (in disease) and a connective tissue attachment, important differences exist, which have clinical implications for the maintenance of peri-implant mucosal health, as well as for the diagnosis and management of peri-implant disease [38].
Soft tissue around teeth is subdivided into gingiva and mobile mucosa. The attached keratinized gingiva is composed of a keratinized epithelium, dense connective tissue, and periosteum which plays an essential role in the protection of periodontal struc- tures. The attached gingiva provides increased resistance of the periodontium to exter- nal injury, contributes to the stabilization of the gingival margin position, and aids in
the dissipation of physiological forces that are exerted by the muscular fibers of the alveolar mucosa onto the gingival tissues [39]. The width of keratinized tissue around natural teeth does not seem to be correlated with the maintenance of periodontal health. According to several reports, a 2.0 mm of attached gingiva is sufficient for the maintenance of periodontal health [3, 40] even in cases in which subgingival restora- tion margins are placed [41–43]. Apically repositioned flap as described by Friedman [44] has been successfully used to increase the width of attached gingival around natu- ral teeth. Moreover, this procedure can be modified and used around implants in cases where a thick gingival biotype is present (when there is no need of improving peri- implant mucosa thickness) (Fig. 10.7), with the advantages of promoting low morbid- ity to the patient (as it precludes the need of second surgical site) and better esthetic color blending [45]. The characteristics of the transmucosal passage-junctional epi- thelium and connective tissue attachment of the implant are established when healing of the ridge mucosa following implant surgery is in progress. In this context it should be realized that an essential role of epithelium in wound healing is to cover any con- nective tissue surface that is severed, such as during surgery. Thus, the epithelial cells
a
b
Fig. 10.7 (a) Maxillary alveolar ridge demonstrating lack of attached keratinized tissue. Note the presence of palatal roughness and shallow palate with evidence of significant maxillary atresia—
(a) baseline; (b) paracrestal incision associated with anterior and posterior vertical releasing inci- sions followed by mucoperiosteal flap elevation and its apical repositioning; (c) buccal and apical mobilization of the flap followed by its stabilization using the surgical adhesive, as well as inter- position of collagen type I sponge on the palatine wound; (d) sutures; (e) 3 weeks follow-up, occlusal view; (f) 3 weeks follow-up, frontal view; (g) 6 weeks follow-up, note the ample keratin- ized tissue band surrounding the implants, as well as the maintenance of the nonkeratinized mucosa close to its original position
e
g
f c
d
Fig. 10.7 (continued)
a
c
b
Fig. 10.8 Anterior mandibular site presenting a single recession defect and a thin periodontal biotype. A free gingival graft was used to decrease recession depth and to increase the width and thickness of keratinized tissue—(a) baseline; (b) 21 days follow-up; (d) 12 months follow-up
at the periphery of the mucosal wound, produced at implant installation, are geneti- cally programmed to divide and migrate across the injured part until epithelial conti- nuity is restored. The epithelial cells also have the ability to adhere to the implant surface, synthesize basal lamina as well as hemidesmosomes, and establish an epithe- lial barrier that has features in common with a junctional epithelium. Equally impor- tant is the capacity of a normal, uninflamed connective tissue to form an attachment to the titanium surface below the epithelium and in a more superficial location to support the junctional epithelium. The maintenance of normal connective tissue is of critical importance for normal turnover of the epithelial and connective tissue attachments to the titanium implant [46].