The dentogingival junction is the critical "seal" between the tooth and gingiva. Understanding how this seal is built, maintained and ultimately destroyed is central to understanding periodontal disease.
Overview
The dentogingival junction (DGJ) is the interface where the gingiva meets the tooth surface. Functionally it:
Protects the underlying periodontal tissues from the oral environment.
Regulates the passage of fluid and immune cells.
Provides a structural and biological attachment between tooth and soft tissues.
Structurally, it is composed of both epithelial and connective tissue components. On the epithelial aspect, three surfaces are important:
The oral gingival epithelium facing the oral cavity.
The sulcular epithelium lining the gingival sulcus.
The junctional epithelium attached directly to the tooth.
Beneath these epithelial layers lies the gingival connective tissue, strengthened by collagen fibre bundles that attach to tooth and bone, supporting the gingival margin.
In health, this system creates a tight yet dynamic barrier that is constantly monitored and defended by the host immune response.
Relationship of the Dentogingival junction to the Tooth Surface
In a healthy, young individual, the junctional epithelium normally terminates near the cemento-enamel junction (CEJ) and often attaches to enamel. With age, and especially the presence of recession of disease, the epithelial attachment may be found on cementum or along the root surface as it migrates apically.
Regardless of whether the attachment is on enamel or cementum, the biological architecture of the epithelial attachment remains similar.
The Gingival Sulcus
The gingival sulcus is a narrow space between the tooth and the inner aspect of free gingiva. Clinically, a healthy sulcus has a probing depth of approximately 1-3.5mm (BPE scores of 0-2). This space is filled with gingival crevicular fluid, an inflammatory exudate that carries immune cells, antibodies, and inflammatory mediators to the sulcus. Even in health, there is a small controlled inflammatory presence here as part of normal surveillance.
Oral Gingival Epithelium
The oral (outer) gingival epithelium covers the marginal and attached gingiva facing the oral cavity. Histologically it is keratinised stratified squamous epithelium. It displays rete pegs extending into the underlying connective tissue, which help to anchor the epithelium and increase surface area. Its principal role is to act as a mechanical and barrier surface, resisting abrasion from mastication while limiting the penetration of bacterial and chemical irritants.
Sulcular Epithelium
The sulcular epithelium lines the gingival sulcus from the free gingival margin down to the coronal limit of the junctional epithelium. Unlike the oral epithelium, it is usually non-keratinised and in health, typically lacks rete pegs. Although it is not directly attached to the tooth surface, it forms the lateral wall of the sulcus and is in close contact with the plaque biofilm. It is more permeable than the oral gingival epithelium and is therefore an important site of interation between bacterial products and host inflammatory mediators.
Junctional Epithelium
The junctional epithelium is the key epithelial component of the dentogingival junction. It forms the epithelial attachment to the tooth and is critical to the integrity of the periodontal seal.
Histological features:
The junctional epithelium is derived from the reduced enamel epithelium during tooth eruption and maintains its attachment to the tooth thereafter. Histologically, the junctional epithelium is non-keratinised stratified squamous epithelium. It is relatively thin, with only about 15-30 cell layers coronally, tapering to only a few layers apically. In health, it does not exhibit rete pegs and has a very high cell turnover, reflecting its dynamic nature at this vulnerable interface.
Microscopic attachment:
The junctional epithelium is anchored between the tooth surface and the underlying connective tissue by two basal laminae:
Tooth side: attached via an internal basal lamina and hemidesmosomes on the epithelial cells.
Connective tissue side: attached va an external basal lamina to underlying gingival connective tissues.
This configuration means the junctional epithelium is effectively suspended between tooth and soft tissues, forming a collar-like attachment around the tooth.
Functional properties:
The junctional epithelium is highly permeable. It allows the passage of neutrophils and gingival crevicular fluid from the underlying connective tissue into the gingival sulcus. This permeability is a double-edged sword: it allows effective immune surveillance and rapid response to bacterial challenge, but also means that bacterial products can more readily diffuse into the tissues.
In health, the coronal extent of the junctional epithelium is at or very near the cemento-enamel junction, and this position is a key reference point when assessing attachment levels clinically.
Gingival Connective Tissue
Beneath the epithelium lies the lamina propria or gingival connective tissue. It is composed primarily of type I collagen, fibroblasts, blood vessels, nerves and a resident population of immune cells.
This connective tissue is firmly attached to both cementum and alveolar bone, helping to stabilise the gingiva. Several key fibre groups provide additional support to help maintain the architecture at the gingival margin:
Dentogingival fibres: extend from cementum into the free and attached gingivae, supporting and stabilising the marginal gingiva.
Circular fibres: encircle the tooth within the marginal gingiva, helping to maintain its contour and position.
Dentoperiosteal fibres: run from cementum over the alveolar crest into the periosteum, anchoring the gingiva to the bone.
Trans-septal fibres: extend from cementum of one tooth to cementum of the adjacent tooth. They help to maintain tooth contact and alignment and contribute to the continuity of the gingival unit.
Together, these fibres brace the gingiva against the tooth and contribute to overall stability of the dentogingival junction.
Supracrestal Tissue Attachment
The concept formerly referred to as "biologic width" is now more precisely described as supracrestal tissue attachment. It represents the combined height of the soft tissues attached to the tooth above the alveolar bone crest.
It has two main components:
The junctional epithelium, approximately 1mm in height
The supracrestal connective tissue attachment, around 1mm of collagen-rich connective tissue between the junctional epithelium and the alveolar bone.
Together, there structures occupy about 2mm above the alveolar crest in health. this dimension is clinically important: when restorative margins encroach on this space, they can cause chronic inflammation, breakdown of attachment and subsequent recession or pocketing as tissues attempt to re-establish an appropraite supracrestal attachment zone.
The Dentogingival Junction in Periodontal Disease
Periodontal disease can be understood as progressive failure of the dentogingival junction under chronic bacterial challenge and host inflammatory response. Broadly, disease progression can be considered in two stages:
Gingivitis: reversible inflammation without the loss of attachment or bone.
Periodontitis: irreversible inflammation with loss of connective tissue attachment and alveolar bone.
Gingivitis
Gingivitis beings the plaque accumulation the gingival margin and within the gingival sulcus. The bacterial biofilm and its products stimulate an inflammatory response in the underlying connective tissue.