[Osteopetrosis. Classification, etiology, treatment options and implications for oral health]

Bone is continuously remodelled to maintain its strength and structural integrity. Remodelling is the result of an equilibrium between bone formation performed by osteoblasts and bone resorption performed by osteoclasts. In osteopetrosis this equilibrium is disturbed by a defect in the osteoclastogenesis or by disfunction of osteoclasts. Osteopetrosis is divided into four types: malignant infantile osteopetrosis, intermediate osteopetrosis, and two types of autosomal osteopetrosis. Malignant infantile osteopetrosis is usually diagnosed within the first year of birth by bone sclerosis and bone marrow obliteration. This type is very severe and usually results in death within a few years. The intermediate type usually appears before the age of ten and leads to recurrent pathologic fractures and cranial nerve compression. Autosomal dominant osteopetrosis is usually mild and consists of two sybtypes. Type I involves marked thickening of the cranial vault. Type II patients have predominantly sclerosis of the pelvis, the vertebrae and the base of the skull. Type I and II patients may often be long-lasting asymptomatic, but will eventually present with pathologic fractures, bone pain, and the effects of cranial nerve compression. Oral problems of osteopetrosis are delayed tooth eruption, absence of some teeth, malformed teeth, enamel hypoplasia, disturbed dentinogenesis, hypomineralisation of enamel and dentin, propensity for tooth decay, defects of the periodontal membrane, thickened lamina dura, mandibular protrusion, and the presence of odontomas. Tooth removal should be limited as it may induce bone fractures and osteomyelitis.