"Floating tooth sign" seen in

i.e. (Histiocytosis X): (631-Basis pathology 8th) (2201-H 17th) (595-Ghai 7th)"Floating tooth sign " - radiographic examination of the mandible, erosion of the bony alveolus around the teeth, so that they seen to be floating in space. It occurs in some of histiocytosis X** (Internet)HISTIOCYTOSIS - X(Langerhans cell histiocytosis) (LCH)* Malignant proliferations of dendritic cells or macrophages and includes three clinico pathologically related conditions occuring in children - eosinophilic granuloma, Hand-Schiller Christian disease and Letterer - Siwe syndrome* Histiocytosis X comprises a variety of syndrome associated with foci of eosinophilic granuloma, Diabetes insipidus exophthalmos and punched out lytic bone lesions* The hall mark of LCH is the presence of Birbeck granules in the cytoplasm** (rod shaped structure having dilated tennis - racket like terminal end) and positivity for S-100 protein and CD la positivity**** Most common involvement is of the skeleton (80%)Odontogenic Myxoma - locally invasive and recurring tumour characterised by abundant mucoid stroma and loose stellate cellsAmeloblastoma - is the most common benign** but locally invasive epithelial odontogenic tumour* Resemblance to like admantinoma of the tibia**** Follicular pattern is the most common* Commonest site is mandible in the molar ramus areaPindborg tumor - is also known as calcifying epithelial odontogenic tumour. It resembles an ameloblastoma in that it is locally invasive and commonly identified as uni-multilocular swelling in the molar-ramus region* Scattered flecks of calcification throughout the radiolucency give rise to the term Driven SnowAppearance**Eosinophilic granuloma - (108-Dalinert 5th)* Eosinophilic granuloma can cause lytic bevelled lesion or "hole within hole 9 appearance in skull. This is due to assymetric destruction of inner + outer tables* Other characteristic bony lesions(i) 'Floating teeth' - due to lesion in jaw(ii) Vertebra plana or 'coin on edge' appearance due to collapse of vertebra(iii) "punched out lesions "Admantinoma - honey comb appearance, Soap bubble appearance* Radicular cysts (Periapical cysts) - Most common type of jaw cysts**