Primary failure of tooth eruption (PFE) is an autosomal dominant disorder caused by a heterozygous mutation in the PTHR1 gene. Affected patients have Primary failure of tooth eruption, with the first and second molar teeth most commonly affected. This leads to a progressive posterior open bite. Ankylosis of deciduous teeth is also noticed, which makes it impossible to use orthodontic force to move the teeth into the correct positions.
Diagnosis is reached by clinical examination, X-ray and genetic testing. Since regular orthodontic treatment causes ankylosis in these patients, prosthetic rehabilitation is the only reasonable option that can be used to manage the condition. In children, removable prosthesis works well.
PFE is transmitted as an autosomal dominant trait with high penetrance and variable expression. Mutations in the parathyroid hormone receptor-1 (PTHR1) gene have been shown to be causal for the condition. This gene codes for a small G-protein coupled receptor that plays a key role in regulation of calcium metabolism as well as skeletal development. The variability in expression of mutations in this gene is exemplified by patients from the same family carrying the same mutation exhibiting varying degrees of phenotypic severity. Recent studies indicate that mutations in PTHR1 may lead to a functionless receptor, thus suggesting that haploinsufficiency of PTHR1 is likely to be the underlying principle of PFE.