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# Bone Diseases Bone diseases are classified into genetic/inherited, fibro-osseous lesions, metabolic and endocrine disorders, and other lesions. ## Genetic/Inherited/Dominant ### Osteogenesis Imperfecta * **Fragile bone:** due to a defect in type I collagen synthesis. * **Long bones are thin an...

# Bone Diseases Bone diseases are classified into genetic/inherited, fibro-osseous lesions, metabolic and endocrine disorders, and other lesions. ## Genetic/Inherited/Dominant ### Osteogenesis Imperfecta * **Fragile bone:** due to a defect in type I collagen synthesis. * **Long bones are thin and fractured easily.** * **Blue sclera** (in some cases). * **Deafness** (in some cases). * **Dental aspects:** * Dentinogenesis imperfecta. * Increased susceptibility to fracture during extractions. * Difficulty with intubation. * Class III malocclusion. * Impactions of teeth 6 and 7. * **Classes:** * **Class I:** Mildest and most common. * **Class II:** More severe; patients may die young. * **Class III:** Oral manifestations. * **Class IV:** Patients do not have blue sclera. ### Osteopetrosis (Marble Bone Disease, Albers-Schonberg Disease) * **Solid, dense but brittle bones** susceptible to fracture. * **Inactivity of osteoclasts** leading to excessive bone formation. * **Replacement of bone marrow with bone**. * **Anemia** due to reduced bone marrow space. * **Hepatosplenomegaly** (enlarged liver and spleen). * **Dental aspects:** * **Unerupted teeth:** Difficulty in eruption. * **Panoramic X-rays:** Difficulty in identifying roots due to increased bone density. * **Increased bone density:** Reduced visibility of bone marrow spaces on radiographs. ## Fibro-osseous Lesions ### Fibrous Dysplasia * **Defect in gene controlling growth and differentiation of osteoblasts.** * **Genetic:** Non-inherited condition. * **Monostotic:** Affects one bone. (Often the maxilla > mandible) * **Polyostotic:** Affects multiple bones. * **Can involve craniofacial bones, ribs, etc.** * **Painless bony swelling** that can be well or poorly defined. * **Affects normal function of mastication and causes malocclusion.** * **Radiographs** show multiple patterns including radiolucent and radiopaque regions. ### Cemento-osseous Dysplasia * **Periapical cemento-osseous dysplasia:** Calcification of bone with connective tissue in periapical areas; common in middle-aged African American women; usually with vital teeth. * **Focal cemento-osseous dysplasia:** Displacement of bone near teeth in a more sporadic fashion. * **Florid cemento-osseous dysplasia:** Radiopaque, irregular masses, often affecting multiple quadrants in the mandible and maxilla. ## Other Diseases ### Achondroplasia * **AD:** Most common genetic skeletal disorder. * **Defect in osteochondral ossification:** Affects epiphyses of long bones; short-limbed. * **Normal head and trunk size.** * **Defective middle 1/3 of face (malocclusion).** ### Cleidocranial Dysplasia * **AD or sporadic:** Defect in closure of sutures in the skull and delayed closure of fontanelles. * **Absence or underdevelopment of clavicles**. * **Retention of primary teeth with delayed eruption of permanent teeth.** * **Multiple unerupted permanent teeth and dentigerous cysts,** * **Thin roots.** * **Facial and skull abnormalities.** ### Cherubism * **Hereditary (AD) or sporadic:** Mutation in the SH3BP2 gene. * **Bilateral, symmetrical expansion of the posterior mandible.** * **Moon-shaped face.** * **Associated with enlargement of the submandibular region.** * **Dental aspects:** Delayed exfoliation of primary teeth, displacement of developing permanent tooth follicles, malformed permanent teeth, and significant malocclusion with tipping and crowding.