Clinical signs of TRs are often minimal since the discomfort can be minor. However, some authors have described discomfort while chewing, anorexia, dehydration, weight loss, and tooth fracture. The lower third premolar is the most commonly affected tooth.

Attrition occurs as a result of opposing tooth surfaces contacting. The contact can affect cuspal, incisal and proximal surface areas.

Indications of attrition can include:

- Loss of tooth anatomy: This results in loss of tooth characteristics including rounding or sharpening of incisal edges, loss of cusps and fracturing of teeth. Enamel of molar teeth may appear thin and flat. When in occlusion the teeth may appear the same height which is particularly apparent for anterior teeth.

- Sensitivity or pain: Attrition may be entirely asymptomatic, or there may be dentin hypersensitivity secondary to loss of the enamel layer, or tenderness of the periodontal ligament caused by occlusal trauma.

- Tooth discolouration: A yellow appearance of the tooth surface may be due to the enamel being worn away, exposing the darker yellower dentin layer underneath.

- Altered occlusion due to decreasing vertical height, or occlusal vertical dimension.

- Compromised periodontal support can result in tooth mobility and drifting of teeth

- Loss in posterior occlusal stability

- Mechanical failure of restorations

Dental fluorosis (also termed mottled enamel) is an extremely common disorder, characterized by hypomineralization of tooth enamel caused by ingestion of excessive fluoride during enamel formation.

It appears as a range of visual changes in enamel causing degrees of intrinsic tooth discoloration, and, in some cases, physical damage to the teeth. The severity of the condition is dependent on the dose, duration, and age of the individual during the exposure. The "very mild" (and most common) form of fluorosis, is characterized by small, opaque, "paper" white areas scattered irregularly over the tooth, covering less than 25% of the tooth surface. In the "mild" form of the disease, these mottled patches can involve up to half of the surface area of the teeth. When fluorosis is moderate, all of the surfaces of the teeth are mottled and teeth may be ground down and brown stains frequently "disfigure" the teeth. Severe fluorosis is characterized by brown discoloration and discrete or confluent pitting; brown stains are widespread and teeth often present a corroded-looking appearance.

People with fluorosis are relatively resistant to dental caries (tooth decay caused by bacteria), although they may be of cosmetic concern. In moderate to severe fluorosis, teeth are physically damaged.

A person experiencing caries may not be aware of the disease. The earliest sign of a new carious lesion is the appearance of a chalky white spot on the surface of the tooth, indicating an area of demineralization of enamel. This is referred to as a white spot lesion, an incipient carious lesion or a "microcavity". As the lesion continues to demineralize, it can turn brown but will eventually turn into a cavitation ("cavity"). Before the cavity forms, the process is reversible, but once a cavity forms, the lost tooth structure cannot be regenerated.

A lesion that appears dark brown and shiny suggests dental caries were once present but the demineralization process has stopped, leaving a stain. Active decay is lighter in color and dull in appearance.

As the enamel and dentin are destroyed, the cavity becomes more noticeable. The affected areas of the tooth change color and become soft to the touch. Once the decay passes through enamel, the dentinal tubules, which have passages to the nerve of the tooth, become exposed, resulting in pain that can be transient, temporarily worsening with exposure to heat, cold, or sweet foods and drinks. A tooth weakened by extensive internal decay can sometimes suddenly fracture under normal chewing forces. When the decay has progressed enough to allow the bacteria to overwhelm the pulp tissue in the center of the tooth, a toothache can result and the pain will become more constant. Death of the pulp tissue and infection are common consequences. The tooth will no longer be sensitive to hot or cold, but can be very tender to pressure.

Dental caries can also cause bad breath and foul tastes. In highly progressed cases, an infection can spread from the tooth to the surrounding soft tissues. Complications such as cavernous sinus thrombosis and Ludwig angina can be life-threatening.

Acid erosion often coexists with abrasion and attrition. Abrasion is most often caused by brushing teeth too hard.

Any frothing or swishing acidic drinks around the mouth increases the risk of acid erosion.

Impacted wisdom teeth without a communication to the mouth, that have no pathology associated with the tooth and have not caused tooth resorption on the blocking tooth rarely have symptoms. In fact, only 12% of impacted wisdom teeth are associated with pathology.

When wisdom teeth communicate with the mouth, the most common symptom is localized pain, swelling and bleeding of the tissue overlying the tooth. This tissue is called the operculum and the disorder called pericoronitis which means inflammation around the crown of the tooth. Low grade chronic periodontitis commonly occurs on either the wisdom tooth or the second molar, causing less obvious symptoms such as bad breath and bleeding from the gums. The teeth can also remain asymptomatic (pain free), even with disease. As the teeth near the mouth during normal development, people sometimes report mild pressure of other symptoms similar to teething.

The term asymptomatic means that the person has no symptoms. The term asymptomatic should not be equated with absence of disease. Most diseases have no symptoms early in the disease process. A pain free or asymptomatic tooth can still be infected for many years before pain symptoms develop.

The two main classification systems are described below. Others include the tooth surface fluorosis index (Horowitz et al. 1984), which combines Deans index and the TF index; and the fluorosis risk index (Pendrys 1990), which is intended to define the time at which fluoride exposure occurs, and relates fluorosis risk with tooth development stage.

Feline Tooth Resorption (TR) is a syndrome in cats characterized by resorption of the tooth by odontoclasts, cells similar to osteoclasts. TR has also been called "feline odontoclastic resorption lesion" (FORL), neck lesion, cervical neck lesion, cervical line erosion, feline subgingival resorptive lesion, feline caries, or feline cavity. It is one of the most common diseases of domestic cats, affecting up to two-thirds. TRs have been seen more recently in the history of feline medicine due to the advancing ages of cats, but 800-year-old cat skeletons have shown evidence of this disease. Purebred cats, especially Siamese and Persians, may be more susceptible.

TRs clinically appear as erosions of the surface of the tooth at the gingival border. They are often covered with calculus or gingival tissue. It is a progressive disease, usually starting with loss of cementum and dentin and leading to penetration of the pulp cavity. Resorption continues up the dentinal tubules into the tooth crown. The enamel is also resorbed or undermined to the point of tooth fracture. Resorbed cementum and dentin is replaced with bone-like tissue.

Early childhood caries (ECC), also known as "baby bottle caries," "baby bottle tooth decay" or "bottle rot," is a pattern of decay found in young children with their deciduous (baby) teeth. The teeth most likely affected are the maxillary anterior teeth, but all teeth can be affected. The name for this type of caries comes from the fact that the decay usually is a result of allowing children to fall asleep with sweetened liquids in their bottles or feeding children sweetened liquids multiple times during the day.

Another pattern of decay is "rampant caries", which signifies advanced or severe decay on multiple surfaces of many teeth. Rampant caries may be seen in individuals with xerostomia, poor oral hygiene, stimulant use (due to drug-induced dry mouth), and/or large sugar intake. If rampant caries is a result of previous radiation to the head and neck, it may be described as radiation-induced caries. Problems can also be caused by the self-destruction of roots and whole tooth resorption when new teeth erupt or later from unknown causes.

Children at 6–12 months are at increased risk of developing dental caries. For other kids aged 12–18 months, dental caries develop on primary teeth and approximately twice yearly for permanent teeth.

Abrasion is a pathological, non-carious tooth loss that most commonly affects the premolars and canines. Abrasion frequently presents at the cemento-enamel junction and can be caused by many contributing factors, all with the ability to affect the tooth surface in varying degrees.

Sources of abrasion may arise from oral hygiene habits such as toothbrushes, toothpicks, floss, and dental appliance or may arise from other habits such as nail biting, chewing tobacco or another object. Abrasion can also occur from the type of dentifrice being utilized as some have more abrasive qualities such as whitening toothpastes.

The appearance may vary depending on the aetiology of abrasion, however most commonly presents in a V-shaped caused by excessive lateral pressure whilst tooth-brushing. The surface is shiny rather than carious, and sometimes the ridge is deep enough to see the pulp chamber within the tooth itself.

In order for successful treatment of abrasion to occur, the aetiology first needs to be identified and ceased, e.g. overzealous brushing. Once this has occurred subsequent treatment may involve the changes in oral hygiene or toothpaste, application of fluoride to reduce sensitivity or the placement of a restoration to aid in reducing the progression of further tooth loss.

Dental attrition is a type of tooth wear caused by tooth-to-tooth contact, resulting in loss of tooth tissue, usually starting at the incisal or occlusal surfaces. Tooth wear is a physiological process and is commonly seen as a normal part of aging. Advanced and excessive wear and tooth surface loss can be defined as pathological in nature, requiring intervention by a dental practitioner. The pathological wear of the tooth surface can be caused by bruxism, which is clenching and grinding of the teeth. If the attrition is severe, the enamel can be completely worn away leaving underlying dentin exposed, resulting in an increased risk of dental caries and dentin hypersensitivity. It is best to identify pathological attrition at an early stage to prevent unnecessary loss of tooth structure as enamel does not regenerate.

All teeth are classified as either developing, erupted (into the mouth), embedded (failure to erupt despite lack of blockage from another tooth) or impacted. An impacted tooth is one that fails to erupt due to blockage from another tooth.

Wisdom teeth develop between the ages of 14 and 25, with 50% of root formation completed by age 16 and 95% of all teeth erupted by the age of 25. However, tooth movement can continue beyond the age of 25.

Impacted wisdom teeth are classified by the direction and depth of impaction, the amount of available space for tooth eruption. and the amount of soft tissue or bone (or both) that covers them. The classification structure helps clinicians estimate the risks for impaction, infections and complications associated with wisdom teeth removal. Wisdom teeth are also classified by the presence (or absence) of symptoms and disease.

One review found that 11% of teeth will have evidence of disease and are symptomatic, 0.6% will be symptomatic but have no disease, 51% will be asymptomatic but have disease present and 37% will be asymptomatic and have no disease.

Impacted wisdom teeth are often described by the direction of their impaction (forward tilting, or mesioangular being the most common), the depth of impaction and the age of the patient as well as other factors such as pre-existing infection or the presence of pathology. Of these predictors, age correlates best with extraction difficulty and complications during wisdom teeth removal rather than the orientation of the impaction.

Another classification system often taught in U.S. dental schools is known as "Pell and Gregory Classification". This system includes a horizontal and vertical component to classify the location of third molars (predominately applicable to mandibular third molars): the third molar's relationship to the occlusal plane being the vertical or "x-component" and to the anterior border of the ramus being the horizontal or "y-component". Vertically, Class A impaction is one in which the occlusal surface of the impacted tooth is level or nearly level with the occlusal plane and the cervical line of the adjacent second molar.

There are many signs of dental erosion, including changes in appearance and sensitivity. One of the physical changes can be the color of teeth. There are two different colors teeth may turn if dental erosion is occurring, the first being a change of color that usually happens on the cutting edge of the central incisors. This causes the cutting edge of the tooth to become transparent. A second sign is if the tooth has a yellowish tint. This occurs because the white enamel has eroded away to reveal the yellowish dentin. A change in shape of the teeth is also a sign of dental erosion. Teeth will begin to appear with a broad rounded concavity, and the gaps between teeth will become larger. There can be evidence of wear on surfaces of teeth not expected to be in contact with one another. If dental erosion occurs in children, a loss of enamel surface characteristics can occur. Amalgam restorations in the mouth may be clean and non-tarnished. Fillings may also appear to be rising out of the tooth, the appearance being caused when the tooth is eroded away leaving only the filling. The teeth may form divots on the chewing surfaces when dental erosion is occurring. This mainly happens on the first, second, and third molars. One of the most severe signs of dental erosion is cracking, where teeth begin to crack off and become coarse. Other signs include pain when eating hot, cold, or sweet foods. This pain is due to the enamel having been eroded away, exposing the sensitive dentin.

Gum recession is generally not an acute condition. In most cases, receding of gums is a progressive condition that occurs gradually over the years. This is one reason that it is common over the age of 40. Because the changes in the condition of the gums from one day to another are minimal, patients get used to the gums' appearance and tend not to notice the recession visually. Receding gums may remain unnoticed until the condition starts to cause symptoms.

The following signs and symptoms may indicate gum recession:

- Tooth mobility

- Dentin hypersensitivity (over-sensitive teeth) - short, sharp pain is triggered by hot, cold, sweet, sour, or spicy food and drink. If the cementum covering the root is not protected anymore by the gums, it is easily abraded exposing the dentin tubules to external stimuli.

- Teeth may also appear longer than normal (a larger part of the crown is visible if gums are receding)

- The roots of the tooth are exposed and visible

- The tooth feels notched at the gum line

- Change in the tooth’s color (due to the color difference between enamel and cementum)

- Spaces between teeth seem to grow (the space is the same, but it seems larger because the gums do not fill it any more)

- Cavities below the gum line

If the gum recession is caused by gingivitis, the following symptoms may also be present:

- Puffy, red, or swollen (inflamed) gums

- Gum bleeding while brushing or flossing

- Bad breath (halitosis)

In some cases, it is the treatment of gingivitis that reveals a gum recession problem, that was previously masked by the gums swelling.

Opacities due to MIH can be quite visible especially on anterior teeth which could present as a problem aesthetically. Patients frequently claim aesthetic discomfort when anterior teeth are involved. The discoloured appearance of the anterior teeth could also have negative effects on a child’s psychological development and self-esteem.

Ankylosis of deciduous teeth ("submerged teeth") may rarely occur. The most commonly affected tooth is the mandibular (lower) second deciduous molar. Partial root resorption first occurs and then the tooth fuses to the bone. This prevents normal exfoliation of the deciduous tooth and typically causes impaction of the permanent successor tooth. As growth of the alveolar bone continues and the adjacent permanent teeth erupt, the ankylosed deciduous tooth appears to submerge into the bone, although in reality it has not changed position. Treatment is by extraction of the involved tooth, to prevent malocclusion, periodontal disturbance or dental caries.

Classifications enable the oral surgeon to determine the difficulty in removal of the impacted tooth. The primary factor determining the difficulty is accessibility, which is determined by adjacent teeth or other structures that impair access or delivery pathway. The majority of classification schemes are based on analysis on a radiograph. The most frequently considered factors are discussed below.

The lesions that appear in teeth affected with MIH can present as opacities that vary from white to yellow-brown. They are usually asymmetrical in appearance, with a sharp demarcation that distinguishes between normal and affected enamel. The lesions usually do not involve the cervical third of affected teeth.

This type of classification is based on the amount of impacted tooth that is covered with the mandibular ramus. It is known as the Pell and Gregory classification, classes 1, 2, and 3.

Internal resorption may sometimes follow dental trauma (although in other cases it appears unrelated). This is where the dentin is resorbed and replaced instead by hyperplastic, vascular pulp tissue. As this process starts to approach the external surface of the tooth, a pink hue of this replacement pulp tissue may become visible through the remaining overlying tooth substance. This appearance is sometimes termed "pink tooth of Mummery".

Teeth die mainly as a result of extensive tooth decay, however this may also occur following dental trauma or heavy drilling down of the tooth during tooth preparation prior to restoration.

Gingival recession, also known as receding gums, is the exposure in the roots of the teeth caused by a loss of gum tissue and/or retraction of the gingival margin from the crown of the teeth. Gum recession is a common problem in adults over the age of 40, but it may also occur starting from the age of a teenager, or around the age of 10. It may exist with or without concomitant decrease in crown-to-root ratio (recession of alveolar bone).

Tooth resorption is a process by which all or part of a tooth structure is lost due to activation of the body's innate capacity to remove mineralized tissue, as mediated via cells such as osteoclasts. Types include external resorption and internal resorption. It can be due to trauma, infection, or hyperplasia.

Internal resorption is an unusual condition where the dentin and pulpal walls begin to resorb centrally within the root canal. The first evidence of the lesion may be the appearance of a pink-hued area on the crown of the tooth; the hyperplastic, vascular pulp tissue filling in the resorbed areas. This condition is referred to as a pink tooth of Mummery, after the 19th century anatomist James Howard Mummery.

The cause can sometimes be attributed to trauma to the tooth, but other times there is no known cause. If the condition is discovered before perforation of the crown or root has occurred, endodontic therapy (root canal therapy) may be carried out with the expectation of a fairly high success rate.

Tooth wear (also termed non-carious tooth substance loss) refers to loss of tooth substance by means other than dental caries or dental trauma. Tooth wear is a very common condition that occurs in approximately 97% of the population. This is a normal physiological process occurring throughout life, but accelerated tooth wear can become a problem.

Tooth wear is majorly the result of three processes; attrition, abrasion and erosion. These forms of tooth wear can further lead to a condition known as abfraction, where by tooth tissue is 'fractured' due to stress lesions caused by extrinsic forces on the enamel. Tooth wear is a complex, multi-factorial problem and there is difficulty identifying a single causative factor. However, tooth wear is often a combination of the above processes. Many clinicians therefore make diagnoses such as "tooth wear with a major element of attrition", or "tooth wear with a major element of erosion" to reflect this. This makes the diagnosis and management difficult. Therefore, it is important to distinguish between these various types of tooth wear, provide an insight into diagnosis, risk factors, and causative factors, in order to implement appropriate interventions.

Multiple indices have been developed in order to assess and record the degree of tooth wear, the earliest was that by Paul Broca. In 1984, Smith and Knight developed the tooth wear index (TWI) where four visible surfaces (buccal, cervical, lingual, occlusal-incisal) of all teeth present are scored for wear, regardless of the cause.