Pathology of the Orofacial System

Pathology of the orofacial system concerns developmental anomalies and their consequences, disease processes, and the course of diseases. It involves investigating the causes (etiology), physical changes (pathologic anatomy), and origin (pathogenesis) of diseases as well as their clinical appearance (signs and symptoms).

The formation and development of the teeth from tooth germs through to eruption is a differentiated, complex process involving active cell structures. Disturbances may arise during the normal course of development. These tissue anomalies have an effect on the functional ability of the masticatory system and therefore must be remedied.

Dysgnathia is a collective term for various morphologic and functional anomalies. It refers to occlusal anomalies such as malposition of teeth, missing tooth germs, or excessive numbers of teeth as well as abnormal jaw development, joint damage, malocclusions, and other forms of systemic damage.These dysgnathic anomalies can be compared with the normal occlusion to determine whether orthodontic treatment is needed.

There is a sliding scale from extreme malformations to an optimal occlusion, from deviations not requiring treatment to severe deformities that necessitate intensive orthodontic treatment. As well as developmental anomalies, the masticatory system can be affected by a variety of diseases caused by external (exogenous) or internal (endogenous) factors, the most severe consequence of which would be tooth loss. Most tooth loss is due to tooth decay (caries) and diseases of the tooth bed (periodontal diseases) (Fig 9-1).

Tooth decay is a chemicoparasitic process that, if left untreated, will progress and lead to destruction of the tooth. Acute or chronic decay of the dental hard tissue starts with demineralization of the enamel. Acid-forming bacteria in the soft deposits on the teeth first demineralize the dental hard substances, then other bacteria also break down the organic constituents. Areas susceptible to caries are all the pits and fissures as well as unclean sites, such as the approximal and cervical areas. Caries does not occur on cusps and marginal ridges, which undergo self-cleaning because of the flow of food. The dental treatment of caries involves mechanically removing the diseased and softened dental hard tissue and replacing it with suitable filling material.

Periodontal diseases are all conditions affecting the tooth bed, especially the purulent, inflammatory processes that lead to reduction of the dental attachment apparatus (periodontium). A distinction is made between gingivitis, marginal periodontitis, and apical periodontal diseases resulting from pulp diseases (pulpitis).

Gingivitis is superficial inflammation of the gingiva with a variety of causes: bacterially induced marginal gingivitis caused by poor oral hygiene (simple gingivitis); necrotizing, ulcerative gingivitis caused by lowered resistance, smoking, and alcohol abuse (ulcerative gingivitis); and puberty gingivitis caused by poor oral hygiene and open mouth breathing.

Marginal periodontitis is an episodic, inflammatory condition of the marginal periodontium caused by bacterial deposits; it can affect the gingiva and the periodontal ligament. Chronic inflammation of the soft tissues, with gingiva that bleeds easily, gingival pockets that contain pus, and accretions on the root, causes the affected teeth to become loose and fall out. It arises from excessive stress on individual teeth, tartar buildup, vitamin C deficiency, metabolic diseases, and hormonal disturbances. To treat marginal periodontitis, causal factors are eliminated and gingival pockets surgically removed.

Pulpitis is inflammation of the dental pulp that may be caused by microbial invasion in the case of caries, by overheating when grinding the dental hard tissues, or by filling materials.This condition takes the form of closed pulpitis (pulp cavity is not open) or open pulpitis (pulp open to the oral cavity). In pulpitis, blood pools in the pulpal veins; if there are pus-forming (pyogenic) bacteria in the tissue, small abscesses will form, and the pus will penetrate the pulp tissue. Mild pulpitis can be fully cured if the causes of the condition are removed.