For decades now, dental implants have been successfully used to replace lost teeth, thereby restoring masticatory function, compromised esthetics, discomfort, and low self-confidence. Original surgical and restorative protocols focused on edentulous patients and included a strictly staged approach as the standard modus operandi. Over the decades, a myriad of developments has been introduced, including implant treatment of partial edentulism and aiming at simplification without jeopardizing predictability of dental implants. A main focus was on a reduction of the number of interventions, the invasiveness of the surgery, and the overall duration of the treatment. Moreover, changing patient demands have obviously stimulated a shortening of the entire treatment approach. Over the years, additional indications presenting with more advanced tissue conditions such as immediate implants have been included for treatments using dental implants.
Tooth-Supporting Tissues
The way our teeth are attached to the alveolar bone by the periodontal ligament (PDL) and protected by the marginal periodontium against foreign intruders is a masterpiece of tissue architecture and function. The cementum, PDL, alveolar bone, and gingiva form an evolutionary, structural, and functional unit called thedental attachment apparatus.1 This unit serves several functions: it anchors the individual teeth to their bony alveoli and binds together one jaw’s teeth into a dental arch. The PDL is a dense connective tissue composed of collagenous fibers and cells, blood vessels, and nerves. It is interposed in the space between the root surface of a tooth and the alveolar bone. Collagen fiber bundles calledSharpey fibers cross the space and are anchored in the root cementum at one end and in the alveolar bone at the other. Sharpey fibers are composed of hundreds of single collagen fibers. Every single fiber is deeply buried and anchored in the mineralized matrix of cementum and in the periosteum of the alveolar bone, respectively. On average, 28,000 collagen fiber bundles insert per 1 mm2 area of cementum on a functioning tooth. The PDL works like a flexible suspension that allows resisting displacing forces and protects the teeth against an excessive occlusal load.
The primary functions of the gingiva around natural teeth are protection and stability; that is, to defend the interface between the teeth and the soft tissues against foreign invaders and to stabilize the position of the tooth in the alveolar bone. The structural framework that allows these tasks to be accomplished offers various spectacular details provided by evolution. Among them are how the gingiva and the underlying bone are protected by the highly specialized junctional epithelium and the way the collagen fibers of the connective tissue are attached to the tooth (Fig 1-1).
FIG 1-1 Dental attachment apparatus.(a) Longitudinal section through the periodontal ligament (PL). B: alveolar bone; D: dentin; C: cementum.(b and c) Sharpey collagen fiber bundles (FB) attached to root cementum (C).(d) Gingiva (G) attached to enamel (E); JE: junctional epithelium.(e) Functionally oriented collagen fibers(red arrows) viewed in transmitted light and(f) viewed in polarized light(white arrows).
The junctional epithelium extends from the sulcular epithelium to the enamel/cementum junct