Definition and Epidemiology

The American Academy of Periodontology has emphasized the direct connection between oral health and general health; accordingly, it is imperative for providers to treat oral infections and to promote oral hygiene.¹ The most common oral infectious lesions are candidiasis, herpes labialis, and recurrent aphthous stomatitis.^2,3 Other common oral lesions are also discussed in this chapter because their recognition is important in the differential diagnosis of systemic disease or oral cavity cancer.

Viral infections of the mouth include those caused by the common herpes simplex virus types 1 and 2 (HSV-1 and HSV-2). HSV-1 is the type most associated with oral lesions, believed to infect up to 90% of the population. Human papillomavirus (HPV) is also found in the oral cavity, manifesting with papillomatous soft tissue lesions. HPV can be transmitted by direct contact, including sexual contact. HPV-associated cancers are estimated to make up 30% of cancers in the United States.³

Bacterial infections of the mouth frequently cause periodontitis or gingivitis. Oral bacterial infections are under intense investigation because they have been linked to systemic diseases, such as cardiovascular disease and diabetes.¹

Candida albicans is the most common fungus to infect the oral cavity. Fungal infections of the mouth are encountered across the spectrum of patient age. Thrush, or candidal infection of the oral mucosa, is caused by the overgrowth of C. albicans, fungi that are normally found in the flora of the gastrointestinal tract. Reports state that as many as 50% of adults may have Candida as part of their normal oral flora. Immunocompromised hosts and patients who wear dentures are susceptible to these oral mucosal lesions, as are patients with diabetes, ulcerative colitis, Crohn disease, gluten sensitivity, or poor oral hygiene and others with poor general health. These lesions may occur from infancy through maturity and can be a recurrent source of irritation. Inhaled steroids are also a risk factor for candidiasis.³

Aphthous ulcers (recurrent aphthous ulceration, canker sores) are defined as shallow, painful, and often recurrent lesions of the oral mucosa. These are the most common oral mucosal lesions in North America.^3,4 Prevalence is estimated at 5% to 50%.⁴ Aphthous ulcers typically affect adolescents and young adults, with more females than males affected. Incidence has been noted to be 20% to 40% in the general population.³ Patients with known ulcerative colitis, Crohn disease, or gluten-sensitive enteropathy may have aphthous ulcers as a feature of these conditions.^3,4

Stomatitis is a general term that refers to the inflammation of the soft tissues of the oral cavity. Chemical or heat injuries can initiate stomatitis; aspirin can cause an ulcerative lesion when it is used as a topical anesthetic on the oral mucosa. Burns sustained from hot food or liquids can also cause mucosal irritations. Certain food substances, chewing gum, oral mouth rinses, and dental products can induce painful lesions.³

Aphthous ulcers and stomatitis are often encountered in primary care practice. Other entities are associated with oral lesions and may include mechanical irritation, drug reactions, local trauma (broken teeth, cheek gnawing), nutritional deficiencies, and stress. These forces irritate and inflame the sensitive oral mucosa. Conditions may be localized to the oral mucosa or associated with systemic disease; therefore it is important to accurately diagnose and appropriately care for oral lesions.^3,4

Pathophysiology

Herpes labialis occurs when HSV-1 is introduced to the oral mucosa through the oral secretions. After the initial outbreak, the virus typically remains in the trigeminal ganglion (HSV-1) and is commonly reactivated at a later time.^3,5 HPV invades the mucosal epithelium and the basal layer, where the viral DNA infects the host DNA. Over 150 HPV types have been identified, of which only nine are known to cause cancer (and another six are being investigated). HPV type 16 is most associated with oral cavity malignancy.⁶

Gingivitis is most commonly associated with bacterial overgrowth in persons with poor oral hygiene. As few as 4 or 5 days without oral care can initiate the infectious process, and continued inattention to dental health can eventually lead to tooth and bone loss.⁷ There is much interest in investigating the role that oral health and gingivitis have in the development of coronary heart disease, atherosclerosis, and stroke.⁸

The most common fungal infection in the oral cavity is candidiasis. Overgrowth of C. albicans (thrush) occurs when the normal oral flora is out of balance or when the host immunity is somehow compromised.⁹

Aphthous ulcers are a common presenting problem for all age groups. Although the exact cause of these ulcers is unknown, it is thought to be autoimmune in nature.² Other proposed etiologic factors include physical or emotional stress; trauma associated with physical, chemical, or local agents; deficiencies of vitamin B₁₂, folic acid, or iron; familial or genetic predisposition; microbial agents; and hypersensitivity states such as gluten-sensitive enteropathy.⁴ Generalized stomatitis may be caused by poor oral hygiene, ill-fitting dentures, and nicotine abuse. Mechanical trauma, chemical trauma from caustic substances, or hot foods may also traumatize the mucosa.³ Thrush more typically occurs with underlying diabetes or with immunocompromised states. Parenteral antibiotic and steroid use have been implicated as precursors to oral candidiasis.^2,3

Clinical Presentation

Patients with herpes simplex typically report a prodromal set of symptoms that include localized pain, tingling, and burning with erythema.^2,3 These symptoms are followed by the eruption of vesicles that evolve into painful ulcerative lesions.³ The patient may experience an incubation period of 4 to 7 days after exposure.²

HPV infections manifest as white, verrucous lesions individually or in clusters. The lesions can be found on the lips, hard palate, or gingiva. They are painless but may become ulcerative in response to local trauma.⁶

Thrush usually appears as white, cottage cheese–like lesions that are easily removed with a swab. The underlying tissue may bleed after manipulation. Children with thrush may have a white coating in the mouth, and they often have difficulty feeding.^2,3

Gingivitis manifests as an inflammation of the gingiva, possibly with areas of ulceration with or without purulent discharge from the affected areas.¹⁰ Patients typically report bleeding with eating (hard food such as chips and crusty breads) or tooth care. Chronic gingivitis may cause only minimal findings.^1,3

Aphthous ulcers are painful, shallow ulcerations of the nonkeratinized oral mucosa and occur as solitary or multiple lesions. A prodrome of burning or pricking of the oral mucosa has been reported.⁴ The lesions may be recurrent but are not typically found on the anterior hard palate or gingiva.³ Ranging in size from 2 mm to several centimeters, aphthous ulcers may have a gray-yellow, pseudomembranous base surrounded by erythema. The disease itself is self-limited, usually lasting 10 to 14 days.⁴

There are three categories of aphthous ulcers. Minor aphthous ulcers are the most common and range in size from 2 to 10 mm (0.08 to 0.4 inch); healing occurs during 7 to 14 days. Many people attribute these minor ulcers to stress, trauma, or even menses. Major aphthous ulcers may be seen as painful lesions that are larger than 1 cm in diameter and are often in a state of cyclic eruption. Scarring is associated with these lesions. The third category is the herpetiform ulceration, which often is mistaken for lesions of HSV. These lesions are small (2 to 3 mm [0.08 to 0.12 inch]), are widely scattered or closely grouped, and may be recurrent. Cultures of these lesions are negative for virus.^2,3

Physical Examination

The lesions of HSV are vesicular with an erythematous base. The vesicles may coalesce and ulcerate before healing. Recurrent lesions may be triggered by fever, stress, and exposure to sunlight.³

Examination of the patient with oral HPV reveals single or multiple verrucous, white, sessile growths.³ The Pap smear is currently the screening tool for genital HPV, but there is currently no screening examination for oral HPV.⁵

Candidal infection manifests as white, curdlike lesions on the oral mucosa or tongue. Patients with xerostomia may have thrush more often, because saliva is an oral protectant against overgrowth of this yeast.^2,3

Gingivitis may cause few physical findings. Minor manipulation of the gingiva may cause local bleeding.⁹

Aphthous ulceration can occur as a solitary lesion or multiple lesions. The usual presentation is a 2- to 10-mm (0.01- to 0.4-inch), ulcerative mucosal lesion that has a white-yellow central fibrinous pseudomembrane.^2,3