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General Information on Oral Pathology

1-1. GENERAL

a.      Pathology is the study of disease, especially of the structural and functional changes in tissues and organs that cause or are caused by disease. Oral pathology is that branch of pathology concerned with diseases of the oral cavity. Microbiology is the study of microorganisms, including bacteria, fungi, and viruses. Disease is a particular destructive process in an organism, usually with a specific cause and characteristic signs and symptoms. A sign is objective evidence of disease that is detectable by the health care provider; for example, redness or bleeding. A symptom is subjective evidence of disease--in other words, what a patient tells the health care provider. Examples of symptoms would be pain and weakness. The word asymptomatic refers to a disease exhibiting no symptoms.

b.      Terminology of a descriptive nature is used to define aspects of a pathological process. Local (localized) means that the disease is restricted to a part or small area of the body. Generalized means the disease affects all parts of the body or covers a large area (many organ systems). Incipient refers to a disease or disorder that is just beginning. Severe refers to an intense distress of prolonged duration caused by the disease process. Acute relates to a sudden onset of symptoms, generally of short duration. Chronic refers to a prolonged disease process, with symptoms generally of a constant nature.

1-2. INFLAMMATION OF TISSUES

When a tissue is injured or irritated by mechanical, chemical, thermal, or bacterial agents, it becomes inflamed. Inflammation is the reaction of a tissue to an injurious agent. The body does not always overcome the attack and so disease persists. For example, the irritation produced by dental caries may result in inflammation of the pulp. This pulpal inflammation is called pulpitis. (The suffix "itis" indicates that inflammation exists.) In every case, the inflammatory condition results from some form of irritation and, to restore normal function to the tissues, the cause must be eliminated. The function of inflammation is to activate all the defenses of the body and to bring them to the site of the injury with the purpose of overwhelming the source of the injury or irritation.

1-3. STAGES OF INFLAMMATION

Inflammation is a body defense mechanism that occurs regardless of the source of injury. The inflammatory response is progressive, in stages; however, it should be realized that various stages may exist within an injured area at the same time. The major stages in the inflammatory process are: vascular change, exudation, and repair. The initial inflammatory response is vascular tissue injury, resulting in the following sequence of events.

a.      Hyperemia. The presence of an abnormally large blood supply in which the blood vessels are dilated and the flow of blood is slower.

b.      Permeability. Increased permeability in the smaller blood vessels, allowing the body to position blood elements in the area in order to heal the injured tissue or combat any introduced foreign agents.

c.      Exudation. The movement of fluid and blood cellular elements (exudates) into the injured tissue(s).

d.      Edema. Accumulation of fluids within the tissue(s) that then slows or stagnates blood flow. This acts to localize the inflammatory process.

1-4. MAJOR SIGNS AND SYMPTOMS OF INFLAMMATION

The four major signs and symptoms of inflammation are swelling, pain, heat, and redness. Sometimes a fifth sign is disturbance of function. Swelling is the visual sign of the accumulation of inflammatory substances (exudates) in the tissues and the increased amount of blood in the area. The pressure of the exudates (and perhaps the action of toxins, enzymes, and acids released from injured cells or liberated by defensive cellular elements) on the nerve endings causes pain. The redness and heat that accompany inflammation are due to the increased amount of blood in the area. Inflammatory involvement of the tissue may result in disturbance of function.

1-5. BENEFICIAL EFFECTS OF INFLAMMATION

The beneficial effects of inflammation are essentially fourfold. First, the increased fluid dilutes the irritants present in the area (that is, bacteria and their poisonous products). Second, the blood cells engulf and often digest bacteria, dead cells, or other debris that might cause or continue the inflammation. Third, antibodies, which are also present in the edema fluid, neutralize toxic substances. Fourth, clotting of the edema fluid walls off the area and prevents the irritant and the inflammation or the inflammatory process from spreading beyond the affected site.

1-6. SUPPURATION

Suppuration is the formation of pus. It often accompanies inflammation and retards the healing process. Pus is composed of leukocytes, broken-down cells, serum, bacteria (dead or alive), and inflammatory debris.

1-7. ABSCESS

An abscess is a circumscribed area of pus surrounded by a restraining wall of tissue. A narrow tube or channel that often develops to afford drainage of the abscess is called a sinus track. A periapical abscess is a collection of pus at the apex of the tooth. It is caused by the spread of infection through the apical foramen of the tooth to the periapical tissues. A periodontal abscess is a collection of pus along the sides of the tooth but usually not involving the apical area. It may be caused by a foreign object forced into the periodontal tissues. Abscesses are often clinically manifested by swelling.

1-8. ULCER

An ulcer is an open sore other than a wound. The base of an ulcer is composed of granulation tissue (wound repair tissue) resulting from the body's attempt at healing and repair.

1-9. CELLULITIS

Cellulitis occurs when inflammation is not controlled and contained within a localized area and spreads through the substance of the tissue or organ. In cellulitis, swelling usually develops rapidly in conjunction with a high fever. The skin usually becomes very red and the area is characterized by severe throbbing pain as the inflammation localizes. The condition is often associated with periapical, periodontal, or pericoronal infections.

1-10. REPAIR OF TISSUES

a. General. The capacity of the human body to restore damaged tissues to health varies with the particular type of tissue or cells involved. Worn-out cells are replaced and tissues rebuilt as a normal physiological process to bring about the growth and repair of the body as a whole. Once tissue injury has been controlled by the inflammatory process, wound repair can begin. Cells in the area of the injury proliferate, organizing to return the tissue to its original form with resumption of previous function. The process of healing is fundamentally the same in all damaged tissues. It consists of two parts. First is the removal of inflammatory material and necrotic debris. The second part, as much as possible, is the replacement or reconstruction of the original tissue.

b.      Granulation. The process of healing involves the invasion and replacement of dying and dead tissue by immature mesenchyma called granulation tissue. Granulation tissue consists mostly of fibroblasts and capillaries. As wound repair progresses, the fibrous and vascular cell components gradually convert into a mature tissue. Then, old epithelial cells at the wound edge proliferate to cover the new fibrous tissue surface. If the wound edges are not brought together or are exposed to irritants or infections, granulation tissue forms on the opposing surfaces and fills the space.

c.      First Intention. This is the healing process observed when the wound surfaces are close together, such as in a small cut or in a closely sutured wound. The first step in repair is the formation of a clot. This clot is slowly replaced by granulation tissue and a covering of epithelium. When the edges of a clean aseptic wound are closely approximated, rapidly growing (proliferative) connective tissue cells join the walls of the wound and proliferative epithelial cells close over the surface. In first intention, the wound heals without scarring.

d.      Second Intention. This is the healing process observed when the opposing edges of the wound are not together, such as in a large ulcer. Granulation tissue fills in the wound from the base and eventually is covered with epithelium. In many instances, repair results in less than completely normal regeneration, causing altered tissue structure that forms a fibrous scar. In second intention, healing is often characterized by the formation of a scar.

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