page_title: Tooth ankylosis
section_title: Causes
hierarchical_section_title: Tooth ankylosis / Causes
context_page_description: Tooth ankylosis is the pathological fusion between alveolar bone and the cementum of teeth, which is a rare phenomenon in the deciduous dentition and even more uncommon in permanent teeth. Ankylosis occurs when partial root resorption is followed by repair with either cementum or dentine that unites the tooth root with the alveolar bone, usually after trauma. However, root resorption does not necessarily lead to tooth ankylosis and the causes of tooth ankylosis remain uncertain to a large extent. However, it is evident that the incident rate of ankylosis in deciduous teeth is much higher than that of permanent teeth.
  Risk factors of tooth ankylosis can be generally classified into genetic factors and dental trauma. Diagnostic methods of tooth ankylosis include the use of clinical examinations, x-ray and cone beam computerized tomography. Tooth ankylosis could have several symptoms, with decreased tooth count being the most prominent one. Factors like gender and sex may also lead to the incidence of certain signs, yet the full mechanisms have not been well evaluated. In general, the non-growing subjects and growing subjects would exhibit different signs and symptoms.
context_section_description: The causes of ankylosis 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 ankylosis 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 ankylosis 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 ankylosis of teeth. The association between tooth ankylosis and orthodontic treatment are also observed in some cases, in which the leakage of etchant to the junction between cementum and enamel during the surgery, damage to the junction or tilting of the tooth may be some possible mechanisms to relate the disease to the 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 ankylosis in the periodontal ligament. This gene can then be transferred from parents to offsprings and lead to ankylosis of teeth.
caption: Diagram of a healthy human molar showing the enamel, cementum, pulp, and dentin which make up the structure, as well as the surrounding tissues