Differences in hard tissues

Difference between acellular and cellular cementum

	Acellular cementum	Cellular cementum
Commonly seen in	Cervical and middle third of root	Apical third of root
Position of cells	No cells	Lacunae and canaliculi containing cementocytes and their processes
Border with dentin	Not clearly demarcated	Clearly demarcated
Rate of development	Relatively slow	Relatively fast
Incremental lines	Relatively close together	Relatively wide apart
Precementum layer	Virtually absent	Present

Difference between alveolar bone, cementum, dentin and enamel

	Alveolar bone	Cementum	Dentin	Enamel
Derived from	Mesoderm	Ectomesenchyme	Ectomesenchyme	Ectoderm
Cell of origin	Osteoblast	Cementoblast	Odontoblast	Ameloblast
Cells in mature tissue	Osteocytes	Cemetocytes (absent in acellular cementum)	Odontoblasts	Does not persist
Degrading cells	Osteoclasts	Cementoclasts / odontoclasts	Odontoclast	Odontoclast
Matrix vesicle formation	Observed	Observed	Observed	Not seen
Apatite content (in %)	50 to 60	45 -50	70	96
Primary organic content	Collagen	Collagen	Collagen	Enamel proteins
Remodeling	High rate	No remodeling	No remodeling	No remodeling
Repair	By new bone	By new cementum	By tertiary dentin	No repair except remineralization in surface
Incremental lines	Resting and reversal lines	Slater	Von Ebner, Owen, neonatal line	Retzius, neonatal line
Nerve innervation	Yes	Nil	Yes – only pain fibers	Nil
Vascularity	Yes	No vascular channels	No vascular channels	No vascular channels