The term "Primary Failure of Tooth Eruption" (PFE) refers to the presence of one or more primary non-ankylosed teeth which, due to a disruption in the eruption mechanism, do not or only partially erupt on their own. After the resorption of the coronal alveolar bone, these teeth do not fully erupt despite the absence of a mechanical obstruction. PFE with pathogenic mutations in the PTHR1 gene, located on chromosome 3 (3p22-21.1), is characterised by a defect in the periodontium. Vertical growth ceases at a certain point, causing the teeth to exhibit progressive infraposition and eventually re-submerge beneath the mucosa. Orthodontic movement of such teeth is not possible as they behave like osseointegrated implants and cause infraposition in unaffected teeth as well. Variants of eruption disorders with a similar phenotype, but without evidence of a pathogenic PTHR1 mutation, also exist.