Oral Infections and Inflammations

The human mouth contains numerous varieties of normal, harmless commensal microorganisms, and the antibacterial action of saliva helps limit their growth. However, the presence of dental plaque and residual food, particularly sugar, in the mouth can promote infection. Inflammation of the mouth is known as dermatitis, while inflammation of the gum is known as gingivitis.

One acute infection that affects the mouth is thrush, caused by the yeast Candida albicans, which occurs when commensal microbes grow in white patches on the tongue and oral mucosa. In adults, opportunistic infections are common in people who are debilitated or whose immunity is lowered by steroids, antibiotics, or cytotoxic drugs. In children, it occurs most commonly in bottle-fed babies. Chronic thrush may develop, affecting the roof of the mouth. In people who wear dentures, the fungi survive in fine grooves on the upper surface of the denture and repeatedly infect the oral mucosa. The same fungi is also responsible for sexually transmitted infections.

Gingivitis is the inflammation of the gums, which may be acute or more commonly chronic. Chronic gingivitis is a common inflammatory condition that occurs in response to the accumulation of bacterial plaque around the teeth. It causes bleeding gums and gradually destroys the tissues that support the teeth, which eventually loosen and may fall out.

Viral infections are usually caused by the herpes simplex virus, HSV-1. Acute herpetic gingivostomatitis is an inflammation of the mouth and gums caused by herpes simplex virus-1 and is the most common oral virus infection. It is characterized by extensive and very painful ulceration. Secondary or recurrent herpes lesions, also known as cold sores, occur around the nose and on the lips. After an initial outbreak, the viruses remain dormant within local nerves. Later outbreaks, usually at the same site, are precipitated by a variety of stimuli, including exposure to UV rays (strong sunlight) and impaired immune response.

Squamous cell carcinoma is the most common type of malignant tumor in the mouth, affecting mainly older adults and carrying a poor prognosis. The usual sites are the floor of the mouth and the edge of the tongue. Ulceration occurs frequently, and there is early spread to surrounding tissues and cervical lymph nodes. In such cases, the prognosis is very poor.

Cleft palate and cleft lip (harelip) are congenital disorders that occur during embryonic development when the roof of the mouth, which is the hard palate, develops as two separate right and left halves. Before birth, these two halves normally fuse along the midline. If fusion is incomplete, a cleft, or division, remains, which may be very minor or substantial. Cleft lip ranges from a minor notch in the upper lip to a more extensive condition when the lip is completely split in one or two places and the nose is involved. In cleft palate, there is a gap between the two halves of the palates, creating a channel of communication between the mouth and the nasal cavity. Contributing factors include genetic abnormalities, certain drugs, or poor nutrition between 7 and 12 weeks of pregnancy. Drinking, eating, and development of speech cannot take place normally until the defect has been surgically repaired.

Tooth decay starts with discoloration and then formation of cavities (caries). It arises when bacteria present in a plaque on the teeth act on sugars, forming acid, which may eventually destroy the hard part of the teeth. Caries can be prevented by good oral hygiene.

Mumps is an acute inflammatory condition of the salivary glands, especially the parotids, caused by the mumps virus, which is one of the parainfluenza group of viruses. The virus spreads through inhalation of infected droplets and multiplies elsewhere in the body before spreading to the salivary glands.

Mumps virus is most infectious for 1-2 days before and 5 days after symptoms appear. In developed countries, children are usually vaccinated against mumps in their preschool years to prevent its spread. However, in unvaccinated individuals, mumps can cause serious complications such as meningitis or meningoencephalitis affecting the brain and orchitis, which is testicular inflammation, after puberty. In some cases, the testes may even atrophy, leading to sterility.

In addition to mumps, there are other viral infections that can affect the mouth. These infections are usually caused by one type of herpes simplex virus, HSV-1. Acute herpetic gingivostomatitis is an inflammation of the mouth and gums caused by herpes simplex virus-1 and is the most common oral virus infection. It is characterized by extensive and very painful ulceration. Recurrent herpes lesions, also known as cold sores, are caused by the same virus and occur around the nose and on the lips. After an initial outbreak, the viruses remain dormant within local nerves. Later outbreaks, usually at the same site, are precipitated by a variety of stimuli, including exposure to UV rays (strong sunlight) and impaired immune response.

Aside from viral infections, there are also tumors that can affect the mouth, such as squamous cell carcinoma, which is the most common type of malignant tumor in the mouth. It mainly affects older adults and carries a poor prognosis. The usual sites are the floor of the mouth and edge of the tongue, and ulceration occurs frequently. There is early spread to surrounding tissues and cervical lymph nodes in which case the prognosis is very poor.

Finally, there are congenital disorders that can affect the mouth, such as cleft palate and cleft lip (harelip). During embryonic development, the roof of the mouth, which is the hard palate, develops as two separate halves – the right and left halves – from the lips anteriorly to the uvula posteriorly. Before birth, these two halves normally fuse along the midline. If fusion is incomplete, a cleft, which is a division, remains, which may be minor or substantial. Cleft lip ranges from a minor notch in the upper lip to a more extensive condition when the lip is completely split in one or two places and the nose is involved. In cleft palate, there is a gap between the two halves of the palates, which creates a channel of communication between the mouth and the nasal cavity. Contributing factors include genetic abnormalities, certain drugs, or poor nutrition between 7 weeks and 12 weeks of pregnancy. Drinking, eating, and development of speech cannot take place normally until the defect has been surgically repaired.

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