The position of the mental foramen on panoramic radiographs of patients with neurofibromatosis type 1.

UNLABELLED: Neurofibromatosis type 1 (NF1) is an autosomal dominant tumor predisposition disorder and a disease with frequent osseous malformations. In the craniomaxillofacial region, bony malformations of NF1 patients are often associated with plexiform neurofibromas (PNF). PNF can manifest early in life and often have a topographical relationship to the branches of the trigeminal nerve. It is unclear when these nerve sheath tumors interact with the skeleton. Since tooth and bone development can be correlated with stages of prenatal development, a fixed point of mandibular ossification, the topography of the mental foramen (MF), was used to assess the timing of possible interactions between PNF and bone deformation.

MATERIAL AND METHODS: The panoramic radiographs (PRs) of 182 patients with confirmed NF1 were examined for MF's position and compared with PRs from 182 healthy individuals who were matched for gender and age (age (years): min: 13; max.: 73; mean: 35; male/female = 79/103).

RESULTS: In most cases, the MF was located between the roots of the premolars or below the second premolar in both groups. The distribution pattern of the foramina did not differ between the NF1 groups. There was no tumor effect (PNF) on the topography of the foramen.

CONCLUSION: Most of the PNF-associated mandibular dysplasia probably develop only after perineural ossification of the mandible at the MF and peri-foraminal arrangement of primary tooth germs and precursors of permanent dentition. The PNF-associated, often bizarre deformities of the lower jaw usually manifest distally to the premolar region, where they influence postnatal bone development.