Other bone disorders

Question 1

Describe achondroplasia:

Answer 1

• Autosomal dominant condition
• Definition/mechanism: Fibroblast growth factor receptor 3 (FGFR3) mutation -> abnormal cartilage synthesis, decreases epiphyseal bone formation.

Symptoms:

• Disproportionate short stature: short limbs, macrocephaly (big head)
• Midface retrusion (“concave face”)
• Frontal bossing (protuberance of frontal bones)

Question 2

Describe osteogenesis imperfecta

Answer 2

• Several subtypes: autosomal dominant, autosomal recessive, or X-linked
• Definition: genetic disorder of type 1 collagen -> poorly formed colalgen
• Symptoms: fragile bones, blue sclera, weak ligaments/tendons, deafness, cardiac defects.
• Dentinogenesis imperfecta type 1 is associated with osteogenesis imperfecta

Question 3

Describe osteomyelitis

Answer 3

• Definition/mechanism:
  1) Infection and inflammation of bone, caused by microorganisms.
  2) Bacteria get access to bone via trauma, blood spread or adjacent infection.
  3) Low vascularity bones are more susceptible: tibia, humerus, vertebrae, maxilla, and mandible.

Symptoms:

• fever
• pain
• swelling
• erythema (redness of skin/mucosa)
• Suppuration

Treat with intra-venous antibiotics

Question 4

Describe osteomalacia

Answer 4

• Osteomalacia: in adults, inadequate mineralization of osteoid during bone turnover
• Risk factors: vitamin D deficiency, calcium deficiency and renal disease
• Definition/mechanism: insufficient phosphate and calcium to mineralized newly formed bone matrix (osteoid)
• Symptoms: softer bones, easy bending and fractures

Question 5

Describe rickets

Answer 5

• Rickets: inadequate skeletal mineralization in children
• Risk factors: vitamin D deficiency, calcium deficiency, renal disease
• Definition/mechanism: impaired mineral deposition of bone affecting growth plates, only seen before growth plate disappears

Symptoms: short stature and bone deformities, negligible effects on dental concerns.

Question 6

Describe metabolic bone disease and dental implications

Answer 6

Any disease of bone that causes abnormal bone remodelling:

• causes reduced volume of mineralized bone
• Causes abnormal bone architecture

Main types:

• Osteoporosis
• Osteomalacia
• Paget’s disease
• Hyperparathyroid bone disease
• Bone disease associated with inflammatory conditions (e.g. rheumatoid arthritis)
• Bone disease associate with renal failure (e.g. renal osteodystrophy)

Question 7

Describe hyperparathyroidism’s definition, mechanism and symptoms.

Answer 7

Definition: chronically high parathyroid hormone (PTH) concentration.

Mechanism:

• increased reabsorption of bone trabeculae
• Increased skeletal bone turnover

Symptoms:

• Decreased plasma phosphate level (PTH causes PO4, dumping kidneys)
• Increased calcium and phosphate urine levels
• Formation of bony-cysts
• Lytic lesions in jaw (“Brown tumours”): contain multinucleated osteoclast-like giant-cells, detectable radiographically
• Loss of lamina dura and “ground-glass” appearance of alveolar bone: mobile teeth

Primary vs secondary

• Primary -> increased plasma calcium levels
• Secondary -> unchanged or decreased plasma calcium levels

Question 8

Describe hypoparathyroidism

Answer 8

Causes: results from accidental removal of the parathyroid gland

Symptoms:

• low plasma calcium (hypocalcaemia)
• Tetany = intermittent muscle spasms
• Dental:
  1) reduced lamina dura contrast
  2) increased lamina dura thickness
  3) large tongue and lips
  4) Enamel hypoplasia (low amounts of enamel)
• Dental in children:
  1) hypoplastic enamel
  2) Delayed eruption

Question 9

Describe Paget’s disease

Answer 9

Definition:

• localized areas of markedly increased bone turnover - irregular bone resorption and replacement
• Dysfunctional osteoclasts cause disorganized new bone.

Aetiology: strong genetic component, 20%

Symptoms:

• Mainly asymptomatic
• Affects pelvis, tibia, femur, lumbar/sacral spine, and skull most
• Rarely:
  1) bone deformity
  2) pain
  3) increased fracture risk
  4) Osteosarcoma (cancer)
  5) Irregular “cotton-wool” pattern of bone (radiographic)

Dental:

• Affects maxilla much more frequently than mandible
• Hypercementosis of teeth
• Enlarged alveolar processes
• Difficulty with extractions (increased bone density)
• Haemorrhage from extraction (vascular fibrous marrow formed)

Question 10

Describe the changes occur that occur to the craniofacial region in hyperparathyroidism

Answer 10

• Cyst-like radioluciencies in jaw
• Loss of lamina dura around tooth socket
• Ground-glass appearance of alveolar bone
• Increasingly mobile teeth

Question 11

Describe changes that occur to the craniofacial region in hypoparathyroidism

Answer 11

• Reduced contrast of lamina dura around tooth socket and increased width.
• Big tongue
• Big lips
• Enamel hypoplasia (low amounts)
• Delayed eruption in children

Question 12

Describe changes that occur to the craniofacial region in Paget’s disease

Answer 12

• Affect maxilla more than mandible
• Enlarged alveolar processes
• Hypercementosis of teeth
• Sclerotic bone
• Increased bone density -> Difficulty with extractions