Loss of attachment:

- By far the most common cause is periodontal disease (gum disease). This is painless, slowly progressing loss of bony support around teeth. It is made worse by smoking and the treatment is by improving the oral hygiene above and below the gumline.

- Dental abscesses can cause resorption of bone and consequent loss of attachment. Depending on the type of abscess, this loss of attachment may be restored once the abscess is treated, or it may be permanent.

- Many other conditions can cause permanent or temporary loss of attachment and increased tooth mobility. Examples include: Langerhans cell histiocytosis.

Increased forces on the tooth:

- Bruxism (abnormal clenching and grinding of teeth) can aggravate attachment loss and tooth mobility if periodontal disease is already present. The tooth mobility is typically reversible and the tooth returns to normal level of mobility once the bruxism is controlled.

- Dental trauma. Luxations, and root fractures of teeth can cause sudden mobility after a blow. Dental trauma may be isolated or associated with other facial trauma.

- Increased biting force on one tooth can cause temporary increased mobility until corrected. A common scenario is a new filling or crown which is a fraction of a millimeter too prominent in the bite, which after a few days causes periodontal pain in that tooth and/or the opposing tooth.

Clinically, there is a number of physiological results that serve as evidence of occlusal trauma:,

- Tooth mobility

- Fremitus

- Tooth migration

- Pain

- Thermal sensitivity

- Pain on chewing or percussion

- Wear facets

Microscopically, there will be a number of features that accompany occlusal trauma:

- Hemorrhage

- Necrosis

- Widening of the periodontal ligament, or PDL (also serves as a very common radiographic feature)

- Bone resorption

- Cementum loss and tears

It was concluded that widening of the periodontal ligament was a "functional adaptation to changes in functional requirements".

The reported symptoms are very variable, and frequently have been present for many months before the condition is diagnosed. Reported symptoms may include some of the following:

- Sharp pain when biting on a certain tooth, which may get worse if the applied biting force is increased. Sometimes the pain on biting occurs when the food being chewed is soft with harder elements, e.g. seeded bread.

- "Rebound pain" i.e. sharp, fleeting pain occurring when the biting force is released from the tooth, which may occur when eating fibrous foods.

- Pain when grinding the teeth backward and forward and side to side.

- Sharp pain when drinking cold beverages or eating cold foods, lack of pain with heat stimuli.

- Pain when eating or drinking sugary substances.

- Sometimes the pain is well localized, and the individual is able to determine the exact tooth from which the symptoms are originating, but not always.

If the crack propagates into the pulp, irreversible pulpitis, pulpal necrosis and periapical periodontitis may develop, with the respective associated symptoms.

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.

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.

Most commonly used classification system with respect to treatment planning. Depending on the angulation the tooth might be classified as:

- Mesioangular

- Horizontal

- Vertical

- Distoangular

- Palatal

- Buccal

- Lingual

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

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.

Mobility is graded clinically by applying pressure with the ends of 2 metal instruments (e.g. dental mirrors) and trying to rock a tooth gently in a bucco-lingual direction (towards the tongue and outwards again). Using the fingers is not reliable as they are too compressible and will not detect small increases in movement. The location of the fulcrum may be of interest in dental trauma. Teeth which are mobile about a fulcrum half way along their root likely have a fractured root.

Normal, physiologic tooth mobility of about 0.25 mm is present in health. This is because the tooth is not fused to the bones of the jaws, but is connected to the sockets by the periodontal ligament. This slight mobility is to accommodate forces on the teeth during chewing without damaging them. Milk (deciduous) teeth also become looser naturally just before their exfoliation. This is caused by gradual resorption of their roots, stimulated by the developing permanent tooth underneath.

Abnormal, pathologic tooth mobility occurs when the attachment of the periodontal ligament to the tooth is reduced (attachment loss, see diagram), or if the periodontal ligament is inflamed. Generally, the degree of mobility is inversely related to the amount of bone and periodontal ligament support left.

Grace & Smales Mobility Index

- Grade 0: No apparent mobility

- Grade 1: Perceptible mobility <1mm in buccolingual direction

- Grade 2: 1mm< but <2mm

- Grade 3: 2mm< or depressibility in the socket

Miller Classification

- Class 1: < 1 mm(Horizontal)

- Class 2: >1 mm(Horizontal)

- Class 3: > 1 mm (Horizontal+vertical mobility)

Cracked tooth syndrome could be considered a type of dental trauma and also one of the possible causes of dental pain. One definition of cracked tooth syndrome is "a fracture plane of unknown depth and direction passing through tooth structure that, if not already involving, may progress to communicate with the pulp and/or periodontal ligament."

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.

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.

1-increased localised pressure.

2- focal growth retardation and stimulation.

An anterior crossbite can be referred as negative overjet, and is typical of class III skeletal relations (prognathism).

An anterior crossbite in a child with baby teeth or mixed dentition may happen due to either dental misalignment or skeletal misalignment. Dental causes may be due to displacement of one or two teeth, where skeletal causes involve either mandibular hyperplasia, maxillary hypoplasia or combination of both.

Various classifications have been proposed to classify gingival recession, Miller’s classification system being the one that is most widely followed. Many cases which are encountered in daily clinical practice cannot be classified according to the criteria of the present classification systems. Kumar & Masamatti's classification system gives a comprehensive depiction of recession defect that can be used to include cases that cannot be classified according to present classifications. A separate classification system for palatal recessions (PR) has been given. A new comprehensive classification system classifies recession on the basis of the position of interdental papilla and buccal/lingual/palatal recessions. Kumar & Masamatti's classification system tries to overcome the limitations of Miller's classification.

For people, the relevance and functionality of teeth can be easily taken for granted, but a closer examination of their considerable significance will demonstrate how they are actually very important. Among other things, teeth serve to:

- support the lips and cheeks, providing for a fuller, more aesthetically pleasing appearance

- maintain an individual's vertical dimension of occlusion

- along with the tongue and lips, allow for the proper pronunciation of various sounds

- preserve and maintain the height of the alveolar ridge

- cut, grind, and otherwise chew food

Supernumerary teeth can be classified by shape and by position. The shapes include the following:

- Supplemental (where the tooth has a normal shape for the teeth in that series);

- Tuberculate (also called "barrel shaped");

- Conical (also called "peg shaped");

- Compound odontoma (multiple small tooth-like forms);

- Complex odontoma (a disorganized mass of dental tissue)

When classified by position, a supernumerary tooth may be referred to as a "mesiodens", a "paramolar", or a "distomolar".

The most common supernumerary tooth is a mesiodens, which is a malformed, peg-like tooth that occurs between the maxillary central incisors.

Fourth and fifth molars that form behind the third molars are another kind of supernumerary teeth.

Dental trauma refers to trauma (injury) to the teeth and/or periodontium (gums, periodontal ligament, alveolar bone), and nearby soft tissues such as the lips, tongue, etc. The study of dental trauma is called dental traumatology.

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.

Dens invaginatus, also known as dens in dente ("tooth within a tooth") is a condition found in teeth where the outer surface folds inward. There are coronal and radicular forms, with the coronal form being more common.

Dens invaginatus is a malformation of teeth most likely resulting from an infolding of the dental papilla during tooth development or invagination of all layers of the enamel organ in dental papillae. Affected teeth show a deep infolding of enamel and dentine starting from the foramen coecum or even the tip of the cusps and which may extend deep into the root. Teeth most affected are maxillary lateral incisors and bilateral occurrence is not uncommon. The malformation shows a broad spectrum of morphologic variations and frequently results in early pulp necrosis. Root canal therapy may present severe problems because of the complex anatomy of the teeth. Cause, prevalence, classification, and therapeutic considerations including root canal therapy, apical surgery and prevention of pulpal involvement are reviewed.

Repair with cementum or dentin occurs after partial root resorption, fusing the tooth with the bone. It may occur following dental trauma, especially occlusal trauma, or after periapical periodontitis caused by pulp necrosis. Ankylosis itself is not a reason to remove a permanent tooth, however teeth which must be removed for other reasons are made significantly more difficult to remove if they are ankylosed.

As stated, the position of maximal closure in the presence of teeth is referred to as maximum intercuspation, and the vertical jaw relationship in this position is referred to as the vertical dimension of occlusion. With the loss of teeth, there is a decrease in this vertical dimension, as the mouth is allowed to overclose when there are no teeth present to block further upward movement of the mandible towards the maxilla. This may contribute, as explained above, to a sunken-in appearance of the cheeks, because there is now "too much" cheek than is needed to extend from the maxilla to the mandible when in an overclosed position. If this situation is left untreated for many years, the muscles and tendons of the mandible and the TMJ may manifest with altered tone and elasticity.

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.