Bacterial

- (Plaque-induced) gingivitis—A common periodontal (gum) disease is Gingivitis. Periodontal refers to the area the infection affects, which include the teeth, gums, and tissues surrounding the teeth. Bacteria cause inflammation of the gums which become red, swollen and can bleed easily. The bacteria along with mucus form a sticky colorless substance called plaque which harbours the bacteria. Plaque that is not removed by brushing and flossing hardens to form tartar that brushing doesn't clean. Smoking is a major risk factor. Treatment of gingivitis is dependent on how severe and how far the disease has progressed. If the disease is not too severe it is possible to treat it with chlorhexidine rinse and brushing with fluoride toothpaste to kill the bacteria and remove the plaque, but once the infection has progressed antibiotics may be needed to kill the bacteria.

- Periodontitis—When gingivitis is not treated it can advance to periodontitis, when the gums pull away from the teeth and form pockets that harbor the bacteria. Bacterial toxins and the body's natural defenses start to break down the bone and connective tissues. The tooth may eventually become loose and have to be removed.

- Scarlet fever is caused by streptococci species, and starts as tonsilitis and pharyngitis before involving the soft palate and the tongue. It usually occurs in children where a fever occurs and a rash develops on the skin. It is treated with penicillin and the prognosis is generally excellent.

Viral

- Herpes simplex (infection with herpes simplex virus, or HSV) is very common in the mouth and lips. This virus can cause blisters and sores around the mouth (herpetic gingivostomatitis) and lips (herpes labialis). HSV infections tend to recur periodically. Although many people get infected with the virus, only 10% actually develop the sores. The sores may last anywhere from 3–10 days and are very infectious. Some people have recurrences either in the same location or at a nearby site. Unless the individual has an impaired immune system, e.g., owing to HIV or cancer-related immune suppression, recurrent infections tend to be mild in nature and may be brought on by stress, sun, menstrual periods, trauma or physical stress.

- Mumps of the salivary glands is a viral infection of the parotid glands. This results in painful swelling at the sides of the mouth in both adults and children. The infection is quite contagious. Today mumps is prevented by getting vaccinated in infancy. There is no specific treatment for mumps except for hydration and painkillers. Sometimes mumps can cause inflammation of the brain, testicular swelling or hearing loss.

Fungal

- Oral candidiasis is by far the most common fungal infection that occurs in the mouth. It usually occurs in immunocompromised individuals. Individuals who have undergone a transplant, HIV, cancer or use corticosteroids commonly develop candida of the mouth and oral cavity. Other risk factors are dentures and tongue piercing. The typical signs are a white patch that may be associated with burning, soreness, irritation or a white cheesy like appearance. Once the diagnosis is made, candida can be treated with a variety of anti fungal drugs.

Smoking and tobacco use of any kind are associated with increased risk of dry socket. This may be partially due to the vasoconstrictive action of nicotine on small blood vessels. Abstaining from smoking in the days immediately following a dental extraction reduces the risk of a dry socket occurring.

Vasoconstrictors are present in most local anesthetics, and are intended to increase the length of analgesia by reducing blood supply to the region which reduces the amount of local anesthetic solution that is absorbed into the circulation and carried from the local tissues. Hence, use of local anesthetics with vasoconstrictors is associated with an increased risk of dry socket occurring. However, frequently use of local anesthetic without vasoconstrictors would not provide sufficient analgesia, especially in the presence of acute pain and infection, meaning that the total dose of local anesthetic may need to be increased. Adequate pain control during the extraction is balanced against an increased risk of dry socket.

There are many oral and maxillofacial pathologies which are not fully understood.

- Burning mouth syndrome (BMS) is a disorder where there is a burning sensation in the mouth that has no identifiable medical or dental cause. The disorder can affect anyone but tends to occur most often in middle aged women. BMS has been hypothesized to be linked to a variety of factors such as the menopause, dry mouth (xerostomia) and allergies. BMS usually lasts for several years before disappearing for unknown reasons. Other features of this disorder include anxiety, depression and social isolation. There is no cure for this disorder and treatment includes use of hydrating agents, pain medications, vitamin supplements or the usage of antidepressants.

- Aphthous stomatitis is a condition where ulcers (canker sores) appear on the inside of the mouth, lips and on tongue. Most small canker sores disappear within 10–14 days. Canker sores are most common in young and middle aged individuals. Sometimes individuals with allergies are more prone to these sores. Besides an awkward sensation, these sores can also cause pain or tingling or a burning sensation. Unlike herpes sores, canker sores are always found inside the mouth and are usually less painful. Good oral hygiene does help but sometime one may have to use a topical corticosteroid.

- Migratory stomatitis is a condition that involves the tongue and other oral mucosa. The common migratory glossitis (geographic tongue) affects the anterior two thirds of the dorsal and lateral tongue mucosa of 1% to 2.5% of the population, with one report of up to 12.7% of the population. The tongue is often fissured, especially. in elderly individuals. In the American population, a lower prevalence was reported among Mexican Americans (compared with Caucasians and African Americans) and cigarette smokers. When other oral mucosa, beside the dorsal and lateral tongue, are involved, the term migratory stomatitis (or ectopic geographic tongue) is preferred. In this condition, lesions infrequently involve also the ventral tongue and buccal or labial mucosa. They are rarely reported on the soft palate and floor of the mouth.

Denture-related stomatitis is usually a harmless condition with no long term consequences. It usually resolves with simple measures such as improved denture hygiene or topical antifungal medication. In severely immunocompromised individuals (e.g. those with HIV), the infection may present a more serious threat.

Periapical periodontitis of some form is a very common condition. The prevalence of periapical periodontitis is generally reported to vary according to age group, e.g. 33% in those aged 20–30, 40% in 30- to 40-year-olds, 48% in 40- to 50-year-olds, 57% in 50- to 60-year-olds and 62% in those over the age of 60. Most epidemiologic data has been generated in European countries, especially Scandinavia. Millions of root canal treatments are carried out in the United States each year, although the total number of root canal treatments is an imperfect indicator of the prevalence of periapical periodontitis, since not always is it performed due to the presence of periapacial periodontitis, and not all cases of asymptomatic periodontitis will be treated in this manner, either due to lack of patient attendance or watchful waiting.

Denture-related stomatitis is common and occurs worldwide. Usually the people affected are middle aged or elderly, with females being affected slightly more commonly than males. Prevalences of up to 70% have been reported in elderly care home residents. It is by far the most common type of oral candidiasis.

Once the plaque stagnation area is removed either through further complete tooth eruption or tooth removal then pericoronitis will likely never return. A non-impacted tooth may continue to erupt, reaching a position which eliminates the operculum. A transient and mild pericoronal inflammation often continues while this tooth eruption completes. With adequate space for sustained improved oral hygiene methods, pericoronitis may never return. However, when relying on just oral hygiene for impacted and partially erupted teeth, chronic pericoronitis with occasional acute exacerbation can be expected.

Dental infections such as a pericoronal abscess can develop into septicemia and be life-threatening in persons who have neutropenia. Even in people with normal immune function, pericoronitis may cause a spreading infection into the potential spaces of the head and neck. Rarely, the spread of infection from pericoronitis may compress the airway and require hospital treatment (e.g. Ludwig's angina), although the majority of cases of pericoronitis are localized to the tooth. Other potential complications of a spreading pericoronal abscess include peritonsillar abscess formation or cellulitis.

Chronic pericoronitis may be the etiology for the development of paradental cyst, an inflammatory odontogenic cyst.

Pericoronitis usually occurs in young adults, around the time when wisdom teeth are erupting into the mouth. If the individual has reached their twenties without any attack of pericoronitis, it becomes substantially less likely one will occur thereafter.

Mouth infections, also known as oral infections, are a group of infections that occur around the oral cavity. They include dental infection, dental abscess, and Ludwig's angina.

Amalgam tattoo is found in up to 1% of people in the general population. It is the most common cause of solitary or focal pigmentation of the oral mucosa.

Daily oral hygiene measures to prevent periodontal disease include:

- Brushing properly on a regular basis (at least twice daily), with the patient attempting to direct the toothbrush bristles underneath the gumline, helps disrupt the bacterial-mycotic growth and formation of subgingival plaque.

- Flossing daily and using interdental brushes (if the space between teeth is large enough), as well as cleaning behind the last tooth, the third molar, in each quarter

- Using an antiseptic mouthwash: Chlorhexidine gluconate-based mouthwash in combination with careful oral hygiene may cure gingivitis, although they cannot reverse any attachment loss due to periodontitis.

- Using periodontal trays to maintain dentist-prescribed medications at the source of the disease: The use of trays allows the medication to stay in place long enough to penetrate the biofilms where the microorganism are found.

- Regular dental check-ups and professional teeth cleaning as required: Dental check-ups serve to monitor the person's oral hygiene methods and levels of attachment around teeth, identify any early signs of periodontitis, and monitor response to treatment.

- Microscopic evaluation of biofilm may serve as a guide to regaining commensal health flora.

Typically, dental hygienists (or dentists) use special instruments to clean (debride) teeth below the gumline and disrupt any plaque growing below the gumline. This is a standard treatment to prevent any further progress of established periodontitis. Studies show that after such a professional cleaning (periodontal debridement), microbial plaque tends to grow back to precleaning levels after about three to four months. Nonetheless, the continued stabilization of a patient's periodontal state depends largely, if not primarily, on the patient's oral hygiene at home, as well as on the go. Without daily oral hygiene, periodontal disease will not be overcome, especially if the patient has a history of extensive periodontal disease.

Periodontal disease and tooth loss are associated with an increased risk, in male patients, of cancer.

Contributing causes may be high alcohol consumption or a diet low in antioxidants.

There are many possible causes of gingival bleeding. The main cause of gingival bleeding is the formation and accumulation of plaque at the gum line due to improper brushing and flossing of teeth. The hardened form of plaque is calculus. An advanced form of gingivitis as a result of formation of plaque is periodontitis. Other causes that can exacerbate gingival bleeding include:

- placement of new dentures

- tooth or gum infection

- diabetes mellitus

- idiopathic thrombocytopenic purpura

- leukemia

- malnutrition

- use of aspirin and anticoagulants(blood thinners) such as warfarin and heparin

- hormonal imbalances during puberty and pregnancy

- iron overload

Other less common causes are:

- vitamin C deficiency (scurvy) and vitamin K deficiency

- dengue fever

Dental caries is an infectious disease caused primarily by "Streptococcus mutans", characterized by acid demineralization of the enamel, which can progress to further breakdown of the more organic, inner dental tissue (dentin). Everybody is susceptible to caries but the probability of development depends on the patient’s individual disease indicators, risk factors and preventive factors. Factors that are considered high-risk for developing carious lesions on the teeth include:

- Low fluoride exposure

- Time, length, and frequency of sugar consumption

- Quality of tooth cleaning

- Fluctuations in salivary flow rates and composition

- Behavior of the individual

- Socioeconomic status of the individual

- Quality and composition of biofilms

Organic acids released from dental plaque lead to demineralization of the adjacent tooth surface, and consequently to dental caries. Saliva is also unable to penetrate the build-up of plaque and thus cannot act to neutralize the acid produced by the bacteria and remineralize the tooth surface.

Prevention of early childhood caries begins before the baby is born; women are advised to maintain a well-balanced diet of high nutritional value, especially during the third trimester and within the infants first year of life. This is since enamel undergoes maturation; if the diet is not sufficient, a common condition that may occur is enamel hypoplasia.

Enamel hypoplasia is a developmental defect of enamel that occurs during tooth development, mainly pre-natally or during early childhood. Teeth affected by enamel hypoplasia are commonly at a higher risk of caries since there is an increased loss of minerals and therefore the tooth surface is able to breakdown more easily than in comparison to a non-hypoplastic tooth. It is therefore suggested to the mother to maintain a healthy diet since evidence suggests malnourishment during the perinatal period increases the risk of hypoplastic teeth in an infant.

OM is usually a polymicrobial, opportunistic infection, caused primarily by a mixture of alpha hemolytic streptococci and anaerobic bacteria from the oral cavity such as "Peptostreptococcus", "Fusobacterium" and "Prevotella", (in contrast to OM of the long bones, usually caused by isolated "Staphylococcus aureus" infection). These are the same as the common causative organisms in odotonogenic infections. However, when OM in the jaws follows trauma, is the likely cause is still staphylococcal (usually "Staphylococcus epidermis".

Other risk factors can be any familial hypercoagulation tendency, including for example, Factor V (Five) Leiden heterozygosity.

Infection of periapical tissues of a high immunity host by organisms of low virulence which leads to a localized bony reaction to a low grade inflammatory stimulus.

The exact cause of the condition is unknown. There is most evidence to support vascular infarction and ischemic necrosis of salivary gland lobules as a mechanism for the condition. Experimentally, local anaesthetic injections and tying of the arteries is reported to trigger the development of tissue changes similar to NS in lab rats. Factors which are thought to cause this ischemia are listed below, however sometimes there is no evident predisposing factor or initiating event.

- Trauma e.g. during intubation, or surgical procedures

- Local anesthetic injection

- Smoking

- Alcohol

- Diabetes mellitus

- Vascular disease, (e.g. arteriosclerosis)

- Pressure from a dental prosthesis

- Allergy

- Bulimia

- Infection

- Ionizing radiation

If left untreated, a severe tooth abscess may become large enough to perforate bone and extend into the soft tissue eventually becoming osteomyelitis and cellulitis respectively. From there it follows the path of least resistance and may spread either internally or externally. The path of the infection is influenced by such things as the location of the infected tooth and the thickness of the bone, muscle and fascia attachments.

External drainage may begin as a boil which bursts allowing pus drainage from the abscess, intraorally (usually through the gum) or extraorally. Chronic drainage will allow an epithelial lining to form in this communication to form a pus draining canal (fistula). Sometimes this type of drainage will immediately relieve some of the painful symptoms associated with the pressure.

Internal drainage is of more concern as growing infection makes space within the tissues surrounding the infection. Severe complications requiring immediate hospitalization include Ludwig's angina, which is a combination of growing infection and cellulitis which closes the airway space causing suffocation in extreme cases. Also infection can spread down the tissue spaces to the mediastinum which has significant consequences on the vital organs such as the heart. Another complication, usually from upper teeth, is a risk of septicaemia (infection of the blood) from connecting into blood vessels, brain abscess (extremely rare), or meningitis (also rare).

Depending on the severity of the infection, the sufferer may feel only mildly ill, or may in extreme cases require hospital care.

The prognosis is excellent, as no treatment is usually required.

If the offending tooth is extracted, the area of condensing osteitis may remain in the jaws indefinitely, which is termed osteosclerosis or bone scar.

Dentists and dental hygienists measure periodontal disease using a device called a periodontal probe. This thin "measuring stick" is gently placed into the space between the gums and the teeth, and slipped below the gumline. If the probe can slip more than below the gumline, the patient is said to have a gingival pocket if no migration of the epithelial attachment has occurred or a periodontal pocket if apical migration has occurred. This is somewhat of a misnomer, as any depth is, in essence, a pocket, which in turn is defined by its depth, i.e., a 2-mm pocket or a 6-mm pocket. However, pockets are generally accepted as self-cleansable (at home, by the patient, with a toothbrush) if they are 3 mm or less in depth. This is important because if a pocket is deeper than 3 mm around the tooth, at-home care will not be sufficient to cleanse the pocket, and professional care should be sought. When the pocket depths reach in depth, the hand instruments and cavitrons used by the dental professionals may not reach deeply enough into the pocket to clean out the microbial plaque that causes gingival inflammation. In such a situation, the bone or the gums around that tooth should be surgically altered or it will always have inflammation which will likely result in more bone loss around that tooth. An additional way to stop the inflammation would be for the patient to receive subgingival antibiotics (such as minocycline) or undergo some form of gingival surgery to access the depths of the pockets and perhaps even change the pocket depths so they become 3 mm or less in depth and can once again be properly cleaned by the patient at home with his or her toothbrush.

If patients have 7-mm or deeper pockets around their teeth, then they would likely risk eventual tooth loss over the years. If this periodontal condition is not identified and the patients remain unaware of the progressive nature of the disease, then years later, they may be surprised that some teeth will gradually become loose and may need to be extracted, sometimes due to a severe infection or even pain.

According to the Sri Lankan tea laborer study, in the absence of any oral hygiene activity, approximately 10% will suffer from severe periodontal disease with rapid loss of attachment (>2 mm/year). About 80% will suffer from moderate loss (1–2 mm/year) and the remaining 10% will not suffer any loss.

Diet plays a key role in the process of dental caries. The type of foods along with the frequency at which they are consumed can determine the risk it puts for also developing carious lesions. With new products being put on supermarket shelves with irresistible prices, this can largely influence what people buy. It is common for infants and young children to frequently consume fermentable carbohydrates, in the form of liquids. The consumption of liquids containing fermentable carbohydrate, include drinks such as: juice, breast milk, formula, soda. These consumables all have the potential to increase the risk of dental caries due to prolonged contact between sugars in the liquid and cariogenic bacteria on the tooth surface.

Recent research has shown that breastfeeding does not increase caries risk up to 12 months of age. Poor feeding practices without appropriate preventive measures can lead to a distinctive pattern of caries in susceptible infants and toddlers commonly known as baby bottle tooth decay or ECC. Frequent and long duration bottle feeding, especially at night, is associated with ECC. This finding can be attributed to the fact that there is less salivary flow at night and hence less capacity for buffering and remineralisation. Each time a child drinks these liquids, acids attack for 20 minutes or longer. A parent's education and health awareness has a major influence on the caries experience of their child - feeding practices, dietary habits and food choices.

Periodontitis is an infection of the gums which leads to bone destruction around the teeth in the jaw. Periodontitis occurs after gingivitis has been established, but not all individuals who have gingivitis will get periodontitis. Plaque accumulation is vital in the progression of periodontitis as the bacteria in plaque release enzymes which attack the bone and cause it to break down, and at the same time osteoclasts in the bone break down the bone as a way to prevent further infection. This can be treated with strict oral hygiene such as tooth brushing and cleaning in between the teeth as well as surgical debridement completed by a dental professional.

A cutaneous sinus of dental origin is where a dental infection drains onto the surface of the skin of the face or neck. This is uncommon as usually dental infections drain into the mouth, typically forming a parulis ("gumboil").

Cutaneous sinuses of dental origin tend to occur under the chin or mandible. Without elimination of the source of the infection, the lesion tends to have a relapsing and remitting course, with healing periods and periods of purulent discharge.

Cutaneous sinus tracts may result in fibrosis and scarring whcich may cause cosmetic concern. Sometimes minor surgery is carried out to remove the residual lesion.

A phoenix abscess is a dental abscess that can occur immediately following root canal treatment. Another cause is due to untreated necrotic pulp (chronic apical periodontitis). It is also the result of inadequate debridement during the endodontic procedure. Risk of occurrence of a phoenix abscess is minimised by correct identification and instrumentation of the entire root canal, ensuring no missed anatomy.

Treatment involves repeating the endodontic treatment with improved debridement, or tooth extraction. Antibiotics might be indicated to control a spreading or systemic infection.