The periodontium is defined as the supporting tissues of the teeth including surrounding alveolar bone, the gingiva, the periodontal ligament, and the outer layer of the tooth roots (all identified in Fig. 7-1).

A. ALVEOLAR BONE

The right and left maxillae bones together, and the mandible, both have a process of bone called the alveolar [al VEE o lar] process that surrounds the roots of all healthy teeth in that arch. The root of each erupted tooth is embedded in an individual alveolus [al VEE o lus] (plural alveoli) or tooth socket whose shape corresponds closely with the shape of the roots of the tooth it surrounds. Each alveolus is lined with a thin compact layer of bone called alveolar bone proper (or bundle bone). This compact bone is seen on a radiograph (x-ray) as the lamina dura.

B. TOOTH ROOT SURFACE

Tooth roots are covered by a thin layer of cementum.

C. PERIODONTAL LIGAMENT (ABBREVIATED PDL)

The periodontal ligament is a very thin ligament composed of many fibers that connects the outer layer of the tooth root (which is covered with cementum) with the alveolar bone proper that lines each alveolus. The groups of fibers of the periodontal ligament represented in Figure 7-1 are greatly enlarged. The entire thickness of the ligament would normally be less than one fourth of a millimeter (0.25 mm).

D. GINGIVA

The gingiva [JIN je va] is a part of the oral tissue (oral mucosa) covered by keratinized tissue (epithelium). This keratinized tissue contains keratin, a fibrous protein found in skin and hair that provides surface toughness. Gingiva covers the alveolar processes of the jaws and surrounds the portions of the teeth near where the root and crown join (cervical portion). The gingiva is the only visible part of the periodontium that can be seen in the mouth during an oral examination.

1. Description of Healthy Gingiva and Oral Mucosa

Healthy gingiva varies in appearance from individual to individual and in different areas of the same mouth. It is usually pink or coral pink (Fig. 7-2), but in many persons with darkly colored and black skin, and in many persons of Mediterranean origin, healthy gingiva may have brown masking pigmentation (melanin pigmentation) (Fig. 7-3). Healthy gingiva is also resilient and firm and does not bleed when probed. Its surface texture is stippled, similar to that of an orange peel. The margins of healthy gingiva are thin in profile and knife edged. The gingival margin is the edge of gingiva closest to the chewing or incising surfaces of the teeth, and, in health, it is somewhat parallel to the cementoenamel junction (CEJ), so it is shaped like a parabolic arch (similar in shape to the McDonald arches). Surface stippling and the parabolic arch pattern around each anterior tooth are evident in Figure 7-4. Characteristics of normal gingiva are listed later in Table 7-1 along with the traits of diseased gingiva.

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