Molecular And Cell Biology

Periodontology 2000, Vol. 24, 2000, 28–55 Printed in Denmark ¡ All rights reserved

Copyright C Munksgaard 2000

PERIODONTOLOGY 2000
ISSN 0906-6713

Molecular and cell biology of the gingiva
P. M ARK B ARTOLD, L AURENCE J . W ALSH & A . S AMPATH N ARAYANAN
The healthy periodontium provides the support necessary to maintain teeth in adequate function. It is comprised of four principal components:namely, the gingiva, periodontal ligament, alveolar bone and cementum. Each of these periodontal components is distinct in its location, tissue architecture, biochemical and cellular composition and yet, they function together as a single unit. Recent research has revealed that the extracellular matrix components of one periodontal compartment can influence the cellular activities of adjacentstructures; thus, pathological changes occurring in one periodontal component may have significant ramifications for the maintenance, repair or regeneration of other components of the periodontium. The gingiva, in health, normally covers the alveolar bone and tooth root to a level just coronal to the cementoenamel junction (Fig. 1). Anatomically, the gingiva is classified into three distinct domains; thefree marginal gingiva, the interdental gingiva and the attached gingiva (187). Histologically, it is composed of two distinct components – the overlying epithelial structures and the underlying connective tissue. While the epithelium is predominantly cellular in nature, the connective tissue is less cellular and is composed primarily of an integrated network of fibrous and nonfibrous proteins,growth factors, minerals, lipids and water. These two components are responsible for orchestrating the earliest responses associated with the development of gingivitis and periodontitis. This chapter considers the general architecture, cellular composition, biochemical attributes and interactive relationship between the gingival epithelium and connective tissue.

Gingival structure, architecture andfunction
Gingival epithelium
Terminology The arrangement of the gingival tissues to the tooth crown and root surfaces is shown in Fig. 1. The gingival epithelia, which cover the underlying connective tissues, can be loosely categorized into at least three different types based on their location and composition. The oral epithelium extends from the mucogingival junction to the tip of the gingivalcrest and is subdivided into the free marginal gingiva and the attached gingiva. The sulcular epithelium lines the gingival sulcus and extends from the tip of the gingival crest to coronal most portion of the junctional epithelium. The junctional epithelium extends from the base of the gingival sulcus to an arbitrary point approximately 2.0 mm coronal to the alveolar bone crest and is closely adaptedto the tooth surface to form sealing and attachment functions. These three epithelia differ ultrastructurally (192), and there are distinct phenotypic differences in their expression of various cytokeratins and cell surface markers (116, 221). Upon completion of the eruption of a tooth, the gingival tissues form a well-defined relationship to the tooth surface and alveolar bone. The epithelialtissues attach to the tooth via an epithelial attach-

Fig. 1. Anatomic relationship of gingival tissues to the teeth and alveolar bone. Clinical landmarks include the free gingiva at the cervical margin of the teeth (FGM); the interdental papilla (IP); and the mucogingival junction (MGJ), which separates the attached gingiva (AG) from the alveolar mucosa (AM).

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Molecular and cell biology of thegingiva

ment termed the junctional epithelium, which, in health, is usually located at, or coronal to, the cementoenamel junction. The gingival tissues attach to the root surface at or below the cementoenamel junction via fiber insertion into the cementum of the root surface which lies coronal to the alveolar crest. The general dimensions of these structures have been described, with the...