The clinical spectrum of tooth-eruption disorders includes both syndromic and nonsyndromic problems ranging from delayed eruption to a complete failure of eruption. A defect in the differential apposition/resorption mechanism in alveolar bone can cause conditions, such as tooth ankylosis, primary failure of eruption (PFE), failure of eruption caused by inadequate arch length, and canine impaction. As our knowledge of the molecular events underlying normal tooth eruption has increased, so too has our understanding of clinical eruption disorders. The recent finding that one gene, parathyroid hormone receptor 1 (PTH1R), is causative for familial cases of PFE suggests that other disturbances in tooth eruption may have a genetic etiology. In this report, we evaluated the current terminology (ie, ankylosis, PFE, secondary retention) used to describe nonsyndromic eruption disorders, in light of this genetic discovery. We observed that some patients previously diagnosed with ankylosis were subsequently found to have alterations in the PTH1R gene, indicating the initial misdiagnosis of ankylosis and the necessary reclassification of PFE. We further investigated the relationship of the PTH1R gene, by using a network pathway analysis, to determine its connectivity to previously identified genes that are critical to normal tooth eruption. We found that PTH1R acts in a pathway with genes, such as parathyroid hormone related peptide (PTHrP), that have been shown to be important in bone remodeling, hence eruption, in a rat model. Thus, recent advances in our understanding of normal and abnormal tooth eruption should allow us in the future to develop a clinical nomenclature system that is determined more by the molecular genetic cause of the eruption failures versus the clinical appearance of the various eruption disorders.
ASJC Scopus subject areas