The under maturation of the enamel causes the tooth structure to be softer, and more susceptible to the effects of bruxism due to abnormalities in skeletal development. The oral abnormalities are evaluated by radiographs and visual examination. Oral radiographs are frequently repeated due to the high incidence of infection due to abnormal biting patterns seen in TDO cases. Cause
TDO is caused by autosomal dominant mutations in the DLX gene family. Known mutations include a 4-basepair deletion in exon 3 of DLX3 on chromosome 17q21, causing a frameshift mutation. Pathogenesis
DLX3 plays numerous significant roles during osseous, connective tissue, and dermal cell differentiation. It is expressed in the placenta and is important for embryonic development of hard bone tissue in the teeth, skull, and long bones such as in the arms and legs. During normal tooth development, DLX3 is predominantly expressed in the inner tooth enamel epithelium. In TDO cases, DLX3 is expressed in the outer enamel epithelium and leads to the abnormally thin enamel observed in the disease, which leads to tooth attrition and is most often the cause of dental abscess seen in TDO persons. DLX3 in TDO is also responsible for upper cranial thickness, calvaria, osteosclerosis of the long bones, long narrow head (dolichocephaly), abnormally thin brittle nails, and premature closing of fibrous joints. Consequently, 95% of people with TDO that are 16 years old or younger show skeletal abnormalities before full maturation takes place.Lack of mastoid pneumatization by mastoid cells occurs in 82% of the cases and is rarely prevalent outside of TDO diagnosis.
Tricho–dento–osseous syndrome (TDO) is a rare, systemic, autosomal dominant genetic disorder that causes defects in hair, teeth, and bones respectively. This disease is present at birth. TDO has been shown to occur in areas of close geographic proximity and within families; most recent documented cases are in Virginia, Tennessee, and North Carolina. The cause of this disease is a mutation in the DLX3 (distal-less 3) gene, which controls hair follicle differentiation and induction of bone formation. All patients with TDO have two co-existing conditions called enamel hypoplasia and taurodontism in which the abnormal growth patterns of the teeth result in severe external and internal defects. The hair defects are characterized as being rough, course, with profuse shedding. Hair is curly and kinky at infancy but later straightens. Dental defects are characterized by dark-yellow/brownish colored teeth, thin and/or possibly pitted enamel, that is malformed. The teeth can also look normal in color, but also have a physical impression of extreme fragility and thinness in appearance. Additionally, severe underbites where the top and bottom teeth fail to correctly align may be present; it is common for the affected individual to have a larger, more pronounced lower jaw and longer bones. The physical deformities that TDO causes become more noticeable with age, and emotional support for the family as well as the affected individual is frequently recommended. Adequate treatment for TDO is a team based approach, mostly involving physical therapists, dentists, and oromaxillofacial surgeons. Genetic counseling is also recommended.