MECHANISMS OF BONE GROWTH & DEVELOPMENT

what are the functions of bone tissue

• load bearing

• protection of vital organs

• movement

• physical form/ shape and aesthetics

• anchor for teeth via cementum and PDL

• hearing

• metabolic e.g. calcium storage, haematopoiesis for RBC

what is the composition of bone

living cells

• osteoblasts

• osteocytes

• osteoclasts

extracellular matrix

• organic (35% by volume)

• mineral (40% by volume)

• water (25% by volume)

outline the ECM of bone

• organic (35% by volume)

  • collagen type I (95%)

  • collagen type V (5%)

  • plus other proteins e.g. osteocalcin

• mineral (40% by volume)

  • hydroxyapatite

• water (25% by volume)

—

ECM of mineralised collagen performs the mechanical work of load bearing and protection

outline the types of bone

outline the forms of bone

what is the periosteum

the periosteum lines the outer surface of cortical bone

woven bone

what does this histological image show

osteoclasts in resorption cavity

what does this histological image show

osteoclast lacunae

relevancy of bone physiology to dentistry

phases of bone remodelling

outline the mechanism of bone remodelling

what kind of cycle is bone remodelling

a continuous process

the adult skeleton is effectively replaced how often

every decade

systemic factors stimulating bone resorption (6)

systemic factors stimulating bone formation

local factors stimulating bone resorption (4)

local factors stimulating bone formation

what are the forms of bone healing (extension of remodelling)

• primary

• secondary

outline primary bone healing

primary bone healing

• if the site of injury is mechanically stable with low mechanical strain and a good blood supply, direct contact

• intramembranous bone healing will occur via remodelling

outline secondary bone healing

secondary bone healing

• more commonly, healing occurs via endochondral ossification

• fracture healing here begins in a relatively hypoxic environment

• this leads to recruitment of stromal cells and formation of a cartilaginous callus

note about first stage of endochondral ossification

list some bone diseases

• Paget’s disease

• bone cancers

• Medication-related osteonecrosis of the jaw (MRONJ)

outline Paget’s disease

• enlarged or deformed bones

• causes not fully understood

• may be managed with drug therapies

outline bone cancers

• occurs with solid e.g. breast, prostate and haematopoietic malignancies e.g. myeloma

• primary bone cancers are relatively rare, the majority have metastasised from other cancers (2° cancer)

outline MRONJ

• complex pathology

• initiated by accumulation of anti-osteoporotic drugs e.g. bisphosphonates in bone tissue, trauma and microbial colonisation