Pathogenesis of periodontal disease
Periodontal disease begins as an infiltrate subjacent to the epithelium of the gingival margin and rapidly extends throughout
the marginal gingiva to affect the connective tissue underlying both the oral and the sulcular epithelium. In addition, there
are pathologic alterations of both the sulcular and the oral epithelium of the marginal gingiva. The inflammatory lesion is
found throughout the entire thickness of the marginal gingival tissue.
There is a significant correlation between deposit amounts and pocket depths and between deposits and hyperplastic tissues
with the additional factor of infection by periodontal pathogens. The size of hyperplastic tissue mass and pocket depth increases
concurrently as the disease becomes more severe.
Bone loss begins at the bifurcation of the second premolars and around the first premolars. As the disease progresses, the
third and fourth premolars and then the first molars become involved. Bone resorption appears sooner and more severely in
the bifurcation regions than interproximally. The first and second premolars are the teeth most frequently lost from periodontitis
usually exhibiting bilateral symmetry in the disease process. The predilection for bone loss at the bifurcation of totally
normal teeth is located at the base of the gingival sulcus and is readily accessible.
The clinical features and pathogenesis of periodontitis is characterized by conversion of the normal gingiva to acutely inflamed,
highly vascular, collagen poor granulation tissue. The disease begins as an acute vasculitis upon which a lymphoid cell response
becomes superimposed. However, at an early stage, proliferation of the tissues of the gingival margin and the soft tissue
wall of the gingival sulcus occurs and enlargement becomes apparent. With the passage of time, this structure, which presents
clinically as a rolled margin, enlarges and, in cross section, presents a mushroom-like appearance with a cauliflower-like
surface. The structure is comprised of collagen poor, highly vascular granulation tissue with a dense infiltrate of lymphoid
cells and a variable population of PMNs - vasculitis persists.
With time, this structure becomes smaller although in general there is a clear line of demarcation between the normal and
the disease tissue. Enlargement continues until no normal gingiva remains. During this process, extensive bone resorption
occurs. The soft tissues behave in one of two ways, either the hyperplastic granulation tissue remains located near the cemento-enamel
junction and a deep periodontal pocket forms comparable to the situation usually seen around human teeth, or alternatively,
the soft tissue retreats along the root surface as the bone resorbs. In cases of the latter type, the disease may progress
to the point of tooth exfoliation without significant pocket formation.
The total periodontium consists of the connecting and supporting tissues of the teeth. These are the gingiva, periodontal
ligament, cementum, and alveolar bone.
The attached gingiva is the part of the oral mucosa that covers the alveolar processes of the jaw and surrounds the necks
of the teeth. The gingival sulcus is the shallow crevice or space around the tooth bounded by the surface of the tooth on
one side and the epithelium lining the free margin of the gingiva on the other.
The attached gingiva is the most important oral mucosal tissue. It is the first line of defense against periodontal disease,
protecting the subjacent bone and supporting tissues. Without an adequate zone of gingiva to maintain support to the tooth
and protect the alveolar bone, the crestal and alveolar bone will be lost to disease. The width of the attached gingiva is
a very important clinical parameter. It is defined as the distance between the mucogingival junction and the projection on
the external surface of the bottom of the gingival sulcus or the periodontal pocket. It is firm, resilient, and tightly bound
to the underlying periosteum of alveolar bone.
The facial aspect of the attached gingiva extends to the relatively loose and movable alveolar mucosa from which it is demarcated
by the mucogingival junction.
The mucogingival junction remains stationary throughout adult life, changes in the width of the attached gingiva are due to
modifications in the position of the coronal end.
The gingival sulcus is the shallow V-shaped space or groove between the tooth and gingiva that encircles the newly erupted
tooth, only the junctional epithelium persists. The sulcus consists of the shallow space that is coronal to the attachment
of the junctional epithelium and is bounded by the tooth on one side and the sulcular epithelium on the other. The coronal
extent of the gingival sulcus is the gingival margin.
Periodontal disease progresses from the marginal gingiva to the gingival sulcus with subsequent reduction and loss of the
epithelial attachment. Without the epithelial attachment the underlying alveolar bone and periodontal ligament are destroyed.
The loss of supporting bone results in loosening and eventual loss of the tooth.