The periodontium consists of those tissues that support the teeth and is divided into a gingival unit and an attachment unit or attachment apparatus. The following is a list of the various parts of the gingival unit:
The gingiva is made up of free and attached gingiva (Fig. 8-1). Composed of very dense mucosa called masticatory mucosa, it has a thick epithelial covering and keratinized cells. The underlying mucosa is composed of dense collagen fibers (Table 8-1). This type of masticatory mucosa is also found on the hard palate. Masticatory mucosa is well designed to withstand the trauma to which it is subjected in grinding food.
|Tissue Characteristics||Free and Attached Gingiva||Alveolar Mucosa|
|Type of mucosa||Masticatory||Lining|
|Tone||Tightly bound||Movable and elastic|
|Epithelium||Thick epithelial layer||Thin epithelial layer|
|Rete peg formation||No rete peg formation|
|Texture||Stippled surface (like an orange peel)||Smooth|
|Color||Light pink||Red to bright red|
|Fiber||Collagenous fibers||Collagenous fibers and elastic fibers|
The rest of the mouth is lined with a different type of mucosa called lining mucosa. This type makes up the alveolar mucosa. It is thin and freely movable and tears or injures easily. The epithelium covering this lining mucosa is thin and nonkeratinized. Its mucosa is composed of loose connective tissue and muscle fibers.
Free gingiva is the gum tissue that extends from the gingival margin to the base of the gingival sulcus. The attached gingiva extends from the base of this sulcus to the mucogingival junction. Alveolar mucosa is found apical to the mucogingival junction and is contiguous with the rest of the mucous membrane of the cheeks and lips and the floor of the mouth. Free gingiva is usually light pink in color and averages between 0.5 to 2 mm in depth.
The free gingival margin around a fully erupted tooth is located next to the enamel about 0.5 to 2 mm coronal to the cementoenamel junction (CEJ). It forms a collar, which is separated from the tooth by the gingival sulcus. This gingival sulcus is the space between the free gingiva and the tooth. The bottom of the sulcus is influenced by the curvature of the cervical line of the tooth. A healthy gingival sulcus rarely exceeds 2.5 mm in depth.
The gingival papilla is the free gingiva located in the triangular interdental spaces. The apex in the anterior teeth is rather sharp but is more blunt in the posterior teeth. The shape of gingival papilla is greatly affected by the location of the contact area of the adjacent teeth, the shape of the interproximal surfaces of the adjacent teeth, and the CEJ of the adjacent teeth. Inflammation of the gingival papilla is easily recognized because the area takes on a color that is more red than normal and exhibits a puffy appearance with some blunting of its apex.
The inner portion of the gingival sulcus is lined with nonkeratinized epithelium; the outer portion is the free gingiva, which is covered with keratinized epithelium. The attached gingiva begins at the base of the gingival sulcus. A gingival groove often occurs on the outside of the free gingiva and corresponds to the base of the sulcus. This groove is not always present but is to be considered a normal part of the anatomy when present. The attached gingiva extends apically from the base of the sulcus and is attached to the bone and the cementum by a dense network of collagenous fibers. It often has a stippled texture, resembling the dimpled surface of an orange. Stippling becomes evident before the teeth erupt and becomes even more so in adult gingiva. The attached gingiva is highly keratinized and is covered by stratified squamous epithelium in which rete peg formation is evident. The dimpling effect is caused by the rete peg formation, which is simply the irregular binding of the epithelium to the bone by collagen fibers. This causes depressions or dimples where the epithelium is pulled tight to the bone. The color of the gingiva varies from light to dark pink and may contain pigment, correlating to the skin pigmentation of the person. The darker a person’s skin color, then the more likely it is that the gingiva is darker and contains melanin.
The gingiva is connected to the tooth by a meshwork of collagenous fibers. These fibers are formed by fibroblasts, which are the principal cells of connective tissue. All fibers embedded in the cementum are known as Sharpey’s fibers; they extend from the cementum to the papillary area of the gingiva. These fibers pass out from the cementum in small bundles (Fig. 8-2, A). Some of the fibers (A) curve toward the mucosa of the free gingiva and interlace with one another. Other fibers (B) pass directly across from the cementum to the gingiva. Still further apically, other fibers (C) pass from the cementum over the alveolar crest and turn apically between the outer periosteum of the alveolar process and the outer epithelial covering of the attached gingiva.
On the proximal side (Fig. 8-2, B), the connective tissue fibers arise from a higher level on the cementum because of the curvature of the CEJ on the interproximal surfaces of the teeth. This curvature allows more room for the cementum to attach to the gingiva. Attachment is made possible by/>