Fibrous dysplasia: Radiology

Fibrous Dysplasia Radiology Location: • Involves the maxilla almost twice often as the mandible • Most commonly posterior region. • Commonly unilateral and very rarely bilateral. Periphery : Periphery of the lesion is most commonly ill-defined and blends imperceptibly with the normal bone. Periphery of the young lesions sometimes appears to be sharp and even corticated. Internal structures Density and trabecular pattern of the lesion vary considerably Variation is more pronounced in Mandible and more homogenous in maxilla. The internal aspect of bone is of 3 tyeps - More radiolucent than normal Less radiolucent than normal Mixture of these 2 lesions The early lesions appears as a cyst like radiolucency in the jaws Sometimes it appears to have granular internal septa, giving internal aspect a multilocular appearance. Trabeculae: Abnormal trabeculae usually are shorten, thinner, irregularly shaped and more numerous than normal trabeculae. The altered trabeculae may give rise to various appearance such as: - Orange peel (Peau d’orange) Ground glass Thumb print Cotton wool Simple bone cyst like bone cavities are seen and occurs more commonly in mandibular lesions. Effects on surrounding structures : Small lesion has no effect on surrounding structure Typically cause enlargement of the bone from within cause ribbon like thinning of cortex. Expansion of the bone is even along it’s length rather than the more concentric expansion seen with benign tumors. Vertical depth of the mandible is often increased In the maxilla the lesion encroaches the sinus usually from the lateral wall and last section of the sinus to be involved is the most postero-superior portion. Normal anatomic shape of the antrum is most oftenly maintained Lamina dura of the teeth in the affected area of the bone become indistinct. PDL space may appear to be very narrow. FD can displace teeth and interfere with normal eruption. Superior displacement of the IAN canal is another typical finding of FD. Rarely there is root resorption.