[Peri-tumor mandibular demineralization].

This study describes hitherto unpublished observations suggesting mechanism by which a tumor can cause massive resorption of the mandible. Microradiographic analysis of the cancerous areas has shown a mobilization of minerals from compact and spongious bone tissue accompanied by incomplete degradation of collagen fibres. The minerals are deposited in the lumen of the Haversian canals, the medullar cavity and the perimandibular soft tissue, areas which are not normally mineralized.

[The pathogenesis of osteoradionecrosis].

The microradiographic analysis of thick sections of fragments removed from irradiated patients suffering from osteoradionecrosis has made it possible to bring to the fore two types of bone resorption caused by cells: an osteoclastic one not followed by a relevant osteogenesis, and another, pathognomonic of postradic complications, linked with an altered activity of the osteocytes. Those cells, which have been affected, because of a progressive infection, are responsible for an irreversible widening of the osteoplasts, set in the properly vascularized bone regions, in particular in the wall of haversian canals. The coalescence of widened osteoplats causes polycylic cavities which is a typical feature of osteoradionecrosis.

[The dental system and facial growth].

1. As they grow, the dental germs build their chamber, exerting tensions on a fibrillar structure facing their occlusal side or incisive edge. This structure now stretches the circular margin of the alveolus, made of chondroïd tissue.

Long-term sequelae of pelvis irradiation: histological and microradiographical study of a femoral head.

Despite the lack of radiological signs, a femoral head showed histological and microradiographical features of osteonecrosis, 54 years after massive irradiation of the right hip. Intertrabecular spaces were invaded by connectivo-vascular tissue with focal accumulation of mast cells, and several resorption foci were filled with mononucleated cells. Moreover, all the microradiographs showed peculiar hypercalcified lines, sometimes containing empty osteocytic lacunae, the origin of which is difficult to precise.

Radiation osteitis of the clavicle following radiotherapy and radical neck dissection of head and neck cancer.

The bone alterations in the region of the clavicle (3 cases) are similar to those we have observed and described elsewhere in the skeleton i.e., the mandible, maxillary and ethmoid bones.

Skeletal growth and chondroid tissue.

Membranous and endochondral ossification processes are insufficient to describe all the aspects observed in the growing skeleton. The presence of chondroid tissue that we have identified by means of all modern histological techniques, including those able to detect the different types of collagen, has also to be explained. Present in the mandibular symphysis of either the human or cat fetuses, chondroid tissue has also been observed in the other parts of the mandible, in the sutural areas of the skull and in all the bones of both axial and appendicular skeleton.

Bone vitality in the cat's irradiated jaw. Histological study.

The vitality of the mandible in cats was studied from two to 15 months after irradiation. Dose of 80 Gy in three days was delivered using three hairpin shape iridium-192 wires surrounding the mandibula. The osseous vitality was assessed from the percentages of lacunae inhabited by osteocytes (IL).

Considerations about the cloverleaf skull.

The study of four cloverleaf skulls (two fetuses, one infant, and a young adult) concerns two Pfeiffer syndromes, a thanatophoric dysplasia and an isolated case. Clinical and radiologic examinations showed malformations at the level of the calvarium, the base, orbital cavities, and, sometimes, limb abnormalities. Correlations between these findings and the microradiographic analysis of nondemineralized sections elucidate this trilobular appearance of the skull.

Bone vitality in induced radionecrosis of the mandible estimated by osteocytic population counting.

To understand the changes of the irradiated mandibular bone, we tried to define, in space, how the lesions of the osseous tissue appear and involve. We estimated the vitality of the removed jaw fragments by counting the number of inhabited lacunae (I.L.

Histological and microradiographical study of Crouzon's disease.

A histological and microradiographical study of thin undecalcified sections from the cranial vault of three different cases of Crouzon's disease has been performed. The fundamentally abnormal aspects of the bone tissues observed in this disease consist of a premature closing of the sutures, an external membranous bone apposition and an internal selective bone resorption leading to the production of the crests already visible in the clinical radiographs. A thickening of these crests by secondary bone apposition has been observed.

Contribution to the histological and microradiographic study of the craniostenosis.

The authors describe the microradiographical and histological aspects of ill sutures in cases of trigonocephalies, brachycephalies and oxycephalies. This is based on the study of fragments coming from 30 cases of craniostenosis. They question the responsibility of the dura mater and invoke an encephalic cause producing by error forces at the level of the sutural areas.

[Micrographic aspect of mandibular osteoradionecrosis (author's transl)].

Fragments of the lower jaw from 42 patients with carcinoma of the oral cavity or oropharynx, and treated primarely with fraction radiotherapy, were excised for radiation osteonecrosis 6 month to 10 years after irradiations. The excised specimens are X-rayed before being coated with methylmetacrylate. They are then cut into thick sections along lines detailled on the X-ray films.

[Ultrastructure of achromic malignant melanoma of the gingiva. value in differential diagnosis].

The authors report a case of a large oral tumour. On the basis of classical histological and histochemical techniques, the diagnosis was oriented towards an angiosarcoma though it was not possibile to eliminate an achromic melanoma. Ultrastructural studies demonstrated the presence of premelanosomes and established the diagnosis of an achromic malignant melanoma.