The prognosis for impacted wisdom teeth depends on the depth of the impaction. When they lack a communication to the mouth, the main risk is the chance of cyst or neoplasm formation which is relatively uncommon.

Once communicating with the mouth, the onset of disease or symptoms cannot be predicted but the chance of it does increase with age. Less than 2% of wisdom teeth are free of either periodontal disease or caries by age 65. Further, several studies have found that between 30% – 60% of people with previously asymptomatic impacted wisdom teeth will have them extracted due to symptoms or disease, 4–12 years after initial examination.

Extraction of the wisdom teeth removes the disease on the wisdom tooth itself and also appears to improve the periodontal status of the second molar, although this benefit diminishes beyond the age of 25.

Risk factors associated with gingivitis include the following:

- age

- osteoporosis

- low dental care utilization (fear, financial stresses, etc.)

- poor oral hygiene

- overly aggressive oral hygiene such as brushing with stiff bristles

- mouth-breathing during sleep

- medications that dry the mouth

- cigarette smoking

- genetic factors

- pre-existing conditions

Few studies have looked at the percentage of the time wisdom teeth are present or the rate of wisdom teeth eruption. The lack of up to five teeth (excluding third molars, i.e. wisdom teeth) is termed hypodontia. Missing third molars occur in 9-30% of studied populations.

One large scale study on a group of young adults in New Zealand showed 95.6% had at least 1 wisdom tooth with an eruption rate of 15% in the maxilla and 20% in the mandible. Another study on 5000 army recruits found 10,767 impacted wisdom teeth. The frequency of impacted lower third molars has been found to be 72% and the frequency of retained impacted wisdom teeth that are free of disease and symptoms is estimated at 11.6% to 29% which drops with age.

The incidence of wisdom tooth removal was estimated to be 4 per 1000 person years in England and Wales prior to the 2000 NICE guidelines.

Most dental pain can be treated with routine dentistry. In rare cases, toothache can be a symptom representing a life-threatening condition, such as a deep neck infection (compression of the airway by a spreading odontogenic infection) or something more remote like a heart attack.

Dental caries, if left untreated, follows a predictable natural history as it nears the pulp of the tooth. First it causes reversible pulpitis, which transitions to irreversible pulpitis, then to necrosis, then to necrosis with periapical periodontitis and, finally, to necrosis with periapical abscess. Reversible pulpitis can be stopped by removal of the cavity and the placement of a sedative dressing of any part of the cavity that is near the pulp chamber. Irreversible pulpitis and pulp necrosis are treated with either root canal therapy or extraction. Infection of the periapical tissue will generally resolve with the treatment of the pulp, unless it has expanded to cellulitis or a radicular cyst. The success rate of restorative treatment and sedative dressings in reversible pulpitis, depends on the extent of the disease, as well as several technical factors, such as the sedative agent used and whether a rubber dam was used. The success rate of root canal treatment also depends on the degree of disease (root canal therapy for irreversible pulpitis has a generally higher success rate than necrosis with periapical abscess) and many other technical factors.

Successful treatment of a dental abscess centers on the reduction and elimination of the offending organisms.

This can include treatment with antibiotics and drainage. If the tooth can be restored, root canal therapy can be performed. Non-restorable teeth must be extracted, followed by curettage of all apical soft tissue.

Unless they are symptomatic, teeth treated with root canal therapy should be evaluated at 1- and 2-year intervals after the root canal therapy to rule out possible lesional enlargement and to ensure appropriate healing.

Abscesses may fail to heal for several reasons:

- Cyst formation

- Inadequate root canal therapy

- Vertical root fractures

- Foreign material in the lesion

- Associated periodontal disease

- Penetration of the maxillary sinus

Following conventional, adequate root canal therapy, abscesses that do not heal or enlarge are often treated with surgery and filling the root tips; and will require a biopsy to evaluate the diagnosis.

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.

A periodontal abscess most commonly occurs as a complication of advanced periodontal disease (which is normally painless). A periodontal pocket contains dental plaque, bacteria and subgingival calculus. Periodontal pathogens continually find their way into the soft tissues, but normally they are held in check by the immune system. A periodontal abscess represents a change in this balance, related to decreased local or systemic resistance of the host. An inflammatory response occurs when bacteria invade and multiply within the soft tissue of the gingival crevice/periodontal pocket. A pus-filled abscess forms when the immune system responds and attempts to isolate the infection from spreading.

Communication with the oral environment is maintained via the opening of the periodontal pocket. However, if the opening of a periodontal pocket becomes obstructed, as may occur if the pocket has become very deep (e.g. with furcation involvement), then plaque and calculus are trapped inside. Food packing may also obstruct a periodontal pocket. Food packing is usually caused by failure to accurately reproduce the contact points when dental restorations are placed on the interproximal surfaces of teeth. Another potential cause occurs when a periodontal pocket is scaled incompletely. Following this procedure, the gingival cuff tightens around the tooth, which may be enough to trap the bacteria left in the pocket. A gingival retraction cord which is accidentally left "in situ" is an occasional cause of a periodontal abscess.

Penetrating injury to the gingiva e.g. with a toothbrush bristle, fishbone, toothpick or periodontal instrument may inoculate bacteria into the tissues. Trauma to the tissues, e.g. caused by an impact on a tooth, or excessive pressure exerted on teeth during orthodontic treatment. Occlusal overload may also be involved in the development of a periodontal abscess, but this is rare and usually in combination with other factors. Bruxism is a common cause of excessive occlusal forces.

Systemic immune factors such as diabetes can predispose to the formation of periodontal abscesses.

Perforation of a root canal during endodontic therapy can also lead to a periodontal abscess.

Toothache may occur at any age, in any gender and in any geographic region. Diagnosing and relieving toothache is considered one of the main responsibilities of dentists. Irreversible pulpitis is thought to be the most common reason that people seek emergency dental treatment. Since dental caries associated with pulpitis is the most common cause, toothache is more common in populations that are at higher risk of dental caries. The prevalence of caries in a population is dependent upon factors such as diet (refined sugars), socioeconomic status, and exposure to fluoride (such as areas without water fluoridation). In the United States, an estimated 12% of the general population reported that they suffered from toothache at some point in the six months before questioning. Individuals aged 18–34 reported much higher experience of toothache than those aged 75 or over. In a survey of Australian schoolchildren, 12% had experienced toothache before the age of five, and 32% by the age of 12. Dental trauma is extremely common and tends to occur more often in children than adults.

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.

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.

A periodontal abscess (also termed lateral abscess, or parietal abscess), is a localized collection of pus (i.e. an abscess) within the tissues of the periodontium. It is a type of dental abscess. A periodontal abscess occurs alongside a tooth, and is different from the more common periapical abscess, which represents the spread of infection from a dead tooth (i.e. which has undergone pulpal necrosis). To reflect this, sometimes the term "lateral (periodontal) abscess" is used. In contrast to a periapical abscess, periodontal abscesses are usually associated with a vital (living) tooth. Abscesses of the periodontium are acute bacterial infections classified primarily by location.

Dentin hypersensitivity is a relatively common condition. Due to differences in populations studied and methods of detection, the reported incidence ranges from 4-74%. Dentists may under-report dentin hypersensitivity due to difficulty in diagnosing and managing the condition. When questionnaires are used, the reported incidence is usually higher than when clinical examination is used. Overall, it is estimated to affect about 15% of the general population to some degree.

It can affect people of any age, although those aged 20–50 years are more likely to be affected. Females are slightly more likely to develop dentin hypersensitivity compared to males. The condition is most commonly associated with the maxillary and mandibular canine and bicuspid teeth on the facial (buccal) aspect, especially in areas of periodontal attachment loss.

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

There are many possible causes for gingival recession:

- By far the most common cause is gum disease (periodontal disease).

- Overaggressive brushing is often assumed to cause gum recession, however a systematic review of the literature concludes that "The data to support or refute the association between tooth brushing and gingival recession are inconclusive." A subsequent study found horizontal tooth brushing technique (versus Bass technique or circular methods), medium-hardness toothbrush use and brushing only once daily were associated with gingival recession.

- Hereditary thin, fragile or insufficient gingival tissue predisposes to gingival recession.

- Dipping tobacco, which affects the mucous membrane lining in the mouth and will cause receding gums over time

- Self-inflicted trauma, such as habits like digging a fingernail or pencil into the gum. This type of recession more commonly associated with children and persons with psychiatric disorders.

- Scurvy (lack of dietary vitamin C)

- Acute necrotizing ulcerative gingivitis

- Abnormal tooth position, such as tooth crowding, giving inadequate cover of one or more teeth by the jaw bone.

- Piercings in the lip or tongue that wear away the gum by rubbing against it.

- Intentional gingival retraction. For example, the adult tooth may not grow out of the gum, and to remedy this, a procedure called an exposure is done. It involves the gum tissue being cut open to allow the adult tooth to grow out. This is a less common cause of gum recession.

The cause of plaque-induced gingivitis is bacterial plaque, which acts to initiate the body's host response. This, in turn, can lead to destruction of the gingival tissues, which may progress to destruction of the periodontal attachment apparatus. The plaque accumulates in the small gaps between teeth, in the gingival grooves and in areas known as "plaque traps": locations that serve to accumulate and maintain plaque. Examples of plaque traps include bulky and overhanging restorative margins, claps of removable partial dentures and calculus (tartar) that forms on teeth. Although these accumulations may be tiny, the bacteria in them produce chemicals, such as degradative enzymes, and toxins, such as lipopolysaccharide (LPS, otherwise known as endotoxin) or lipoteichoic acid (LTA), that promote an inflammatory response in the gum tissue. This inflammation can cause an enlargement of the gingiva and subsequent formation. Early plaque in health consists of a relatively simple bacterial community dominated by Gram-positive cocci and rods. As plaque matures and gingivitis develops, the communities become increasingly complex with higher proportions of Gram-negative rods, fusiforms, filaments, spirilla and spirochetes. Later experimental gingivitis studies, using culture, provided more information regarding the specific bacterial species present in plaque. Taxa associated with gingivitis included "Fusobacterium nucleatum" subspecies "polymorphum", "Lachnospiraceae" [G-2] species HOT100, "Lautropia" species HOTA94, and "Prevotella oulorum" (a species of "Prevotella" bacterium), whilst "Rothia dentocariosa" was associated with periodontal health. Further study of these taxa is warranted and may lead to new therapeutic approaches to prevent periodontal disease.

Erupted teeth that are adjacent to impacted teeth are predisposed to periodontal disease. Since the most difficult tooth surface to be cleaned is the distal surface of the last tooth, in the presence of an impacted tooth there is always gingival inflammation around the second molar that is invariably present. Even this minor amount of inflammation can provide bacteria access to a larger portion of the root surface that results in early formation of periodontitis compromising the tooth.

Even in situations in which no obvious communication exists between the mouth and the impacted third molar there may be enough communication to initiate dental caries (tooth decay).

In dentistry, calculus or tartar is a form of hardened dental plaque. It is caused by precipitation of minerals from saliva and gingival crevicular fluid (GCF) in plaque on the teeth. This process of precipitation kills the bacterial cells within dental plaque, but the rough and hardened surface that is formed provides an ideal surface for further plaque formation. This leads to calculus buildup, which compromises the health of the gingiva (gums). Calculus can form both along the gumline, where it is referred to as supragingival ("above the gum"), and within the narrow sulcus that exists between the teeth and the gingiva, where it is referred to as subgingival ("below the gum").

Calculus formation is associated with a number of clinical manifestations, including bad breath, receding gums and chronically inflamed gingiva. Brushing and flossing can remove plaque from which calculus forms; however, once formed, it is too hard and firmly attached to be removed with a toothbrush. Calculus buildup can be removed with ultrasonic tools or dental hand instruments (such as a periodontal scaler).

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.

Dentin hypersensitivity may affect individuals' quality of life. Over time, the dentin-pulp complex may adapt to the decreased insulation by laying down tertiary dentin, thereby increasing the thickness between the pulp and the exposed dentin surface and lessening the symptoms of hypersensitivity. Similar process such as formation of a smear layer (e.g. from toothbrushing) and dentin sclerosis. These physiologic repair mechanisms are likely to occur with or without any form of treatment, but they take time.

A great many diseases involve the mouth, jaws and orofacial skin. Some example pathologies which can involve the oral and maxillofacial region are listed. Some are more common than others, and this list is by no means complete. The examples are considered according to a surgical sieve.

Xerostomia is a very common symptom. A conservative estimate of prevalence is about 20% in the general population, with increased prevalences in females (up to 30%) and the elderly (up to 50%).

Pericoronitis is an infection of the soft tissue that covers the crown of an impacted tooth and is usually caused by the normal oral microbiota. For most people there exists a balance between the host defenses and the oral micriobiota but if the host defenses are compromised like during minor illness such as influenza or an upper respiratory tract infection, pericoronitis results. Another common cause is entrapment of food beneath the gum flap (also called an operculum). Pericoronitis can present as a mild infection or severe infection. In its mildest form it is just a localized tissue swelling and soreness whereas in severe forms the swelling is slightly larger even sometimes creating trismus (difficulty opening the mouth).

Occasionally, an impacted tooth causes sufficient pressure on the roots of adjacent teeth causing it to resorb.

An impacted tooth occupies space that is usually filled with bone. This weakens that area of bone and renders the jaw more susceptible to fracture.

When impacted teeth are retained completely within the alveolar process, the associated follicular sac is also retained along with it. Though in most persons the dental follicle maintains its original size sometimes it may undergo cystic degeneration and become a dentigerous cyst or a keratocyst.

Extra teeth, lost teeth, impacted teeth, or abnormally shaped teeth have been cited as causes of malocclusion. A small underdeveloped jaw, caused by lack of masticatory stress during childhood, can cause tooth overcrowding. Ill-fitting dental fillings, crowns, appliances, retainers, or braces as well as misalignment of jaw fractures after a severe injury are other causes. Tumors of the mouth and jaw, thumb sucking, tongue thrusting, pacifier use beyond age 3, and prolonged use of a bottle have also been identified as causes.

In an experiment on two groups of rock hyraxes fed hardened or softened versions of the same foods, the animals fed softer food had significantly narrower and shorter faces and thinner and shorter mandibles than animals fed hard food. Experiments have shown similar results in other animals, including primates, supporting the theory that masticatory stress during childhood affects jaw development. Several studies have shown this effect in humans. Children chewed a hard resinous gum for two hours a day and showed increased facial growth.

During the transition to agriculture, the shape of the human mandible went through a series of changes. The mandible underwent a complex series of shape changes not matched by the teeth, leading to incongruity between dental and mandibular form. These changes in human skulls may have been "driven by the decreasing bite forces required to chew the processed foods eaten once humans switched to growing different types of cereals, milking and herding animals about 10,000 years ago."

To establish appropriate alignment and occlusion, the sizes of upper and lower front teeth, or upper and lower teeth in general, need to be proportional. Inter-arch tooth size discrepancy (TSD) is defined as a disproportion in the mesio-distal dimensions of teeth of opposing dental arches, which can be seen in 17% to 30% of orthodontic patients.

Hairy tongue occurs in about 0.5% of adults. However, the prevalence is variable depending on the population studied.