Diagram of a healthy human molar showing the enamel, cementum, pulp, and dentin which make up the structure, as well as the surrounding tissues The causes of<unk>  of teeth is uncertain. One common belief is the role of genetic factors with an autosomal dominant inheritance pattern, evidenced by the appearance of family occurrence in several families. Trauma, inflammation and infection may also be responsible for causing the disease. The frequency for<unk>  to happen in deciduous teeth is far more frequent than that in permanent teeth, with a ratio of about 10 to 1, and the majority of the ankylosed teeth occur in lower teeth, about twice as often as in the upper teeth. Therefore, it is strongly believed that their incidence may be due to different causes. For<unk>  in permanent teeth, with the first molar being the most common affected teeth, it is hard to find a precise cause because of the complicated nature which is believed to be linked to several different factors and the difficulty in diagnosis as many cases are asymptomatic. For other cases, there are several theories explaining the cause. Dental trauma may be a major cause for the disease since it can lead to luxation, reported in 30 to 44% of all dental trauma cases, and hence replacement resorption, which is the situation in<unk>  of teeth. The association between<unk>  and orthodontic treatment are also observed in some cases, in which the leakage of etchant<unk> e junction between cementum and enamel during the surgery, damage<unk> e junction or tilting of the<unk>  may be some possible mechanisms to relate the disease<unk> e treatment. Genetic factors may also be involved in causing the disease, which is supported by the occurrence of ankylosed molars, either in primary or permanent dentition, in close relatives. The possible explanation is the inheritance of a gene which might be a process imitator of<unk>  in the periodontal ligament. This gene can then be transferred from parents to offsprings and lead to<unk>  of teeth. Deciduous (baby) teeth<unk>  of deciduous teeth may rarely occur. The most commonly affected<unk>  is the mandibular (lower) second deciduous molar. Partial root resorption first occurs and then the<unk>  fuses<unk> e bone. This prevents normal exfoliation of the deciduous<unk>  and typically causes impaction of the permanent successor<unk> . As growth of the alveolar bone continues and the adjacent permanent teeth erupt, the ankylosed deciduous<unk>  appears to submerge into the bone, although in reality it has not changed position. Treatment is by extraction of the involved<unk> , to prevent malocclusion, periodontal disturbance or dental caries. Permanent (adult) teeth In healthy teeth, the periodontal ligament (PDL) fibroblasts block osteogenic cells within the periodontium by releasing locally acting regulators. This separates the<unk>  root from alveolar bone. Damage<unk> e PDL disrupts this process resulting bone growth across the periodontal space and fusion with the root. It may occur following dental trauma, especially re-implanted or severely intruded teeth. Increasing the extra oral dry time increases the likelihood of<unk>  The probability also increases with the severity of intrusion. There is no known treatment to arrest the process.<unk>  itself is not a reason to remove a permanent<unk> , however teeth which must be removed for other reasons are made significantly more difficult to remove if they are ankylosed.<unk>  in growing patients can result in infra occlusion of teeth, this can lead to an aesthetic and functional deficit.
Tooth ankylosis
Radial dysplasia
Metaphyseal dysplasia
Multiple epiphyseal dysplasia
Spinal stenosis
Carpal coalition
Fibrous ankylosis
Tarsal coalition