TOOTH TISSUES: CEMENTUM WABeresford ENAMEL DENTINE GINGIVA PULP

TOOTH TISSUES: CEMENTUM WABeresford ENAMEL DENTINE GINGIVA PULP

TOOTH TISSUES: CEMENTUM WABeresford ENAMEL DENTINE GINGIVA PULP CEMENTUM ALVEOLAR BONE PERIODONTAL LIGAMENT/ PDL TOOTH DESIGN: Spear me Blade

ENAMEL Shaft DENTINE Grip CEMENTUM TOOTH DESIGN: Spear me Refinements ENAMEL DENTINE Shaft is hollow for PULP CEMENTUM

Hand represented by PERIODONTAL LIGAMENT & ALVEOLAR BONE Closer to true proportions CEMENTUM: Role Cementum is the hard covering of the root that can: fuse to dentine, but be alive and grow outwards to trap the periodontalligament fibers, and thus attach the tooth to the alveolar bone. It is itself a kind of bone, but is less susceptible to erosion Bone matrix = collagen fibrils + mineral crystals

REMINDER -BONE CELLS Active Osteoblasts Bone canal vessels Periosteum Osteocyte Osteoclast Resting cells Ca2+

CEMENTUM-BONE DIFFERENCES FORMING CELLS ARE CEMENTOBLASTS IMBEDDED CELLS ARE CEMENTOCYTES ACELLULAR CEMENTUM EXISTS NO PERIOSTEUM Bone matrix = collagen fibrils + mineral crystals Active Osteoblasts Bone canal vessels

Periosteum Osteoclast Resting cells Osteocyte Ca2+ COLLAGEN FIBERS NO TRABECULAE PERPENDICULAR TO NO MARROW SURFACE NO VESSELS OR CANALS WITHIN CEMENTUM ALMOST NO REMODELING

BONE-CEMENTUM SIMILARITIES MATRIX MATERIALS Bone matrix = collagen fibrils + mineral crystals LACUNAE WITH CANALICULI FOR CELLS & CELL PROCESSES Bone canal vessels SIMILAR APPEARANCE IN STAINED & GROUND SECTIONS

Periosteum APPOSITIONAL GROWTH FROM SURFACE INCREMENTAL GROWTH LINES IN MATRIX EROSION BY OSTEOCLASTS (cementoclasts) ORIENTATION: Terms CUSPAL/ OCCLUSAL Enamel CORONAL

CERVICAL { PU LP AL RADICULAR APICAL Cementum CEMENTUM: Position ENAMEL } }

CROWN DENTINE PULP CEMENTUM Cervix ROOT Cementum is on the root, but can extend slightly onto enamel. Cementum also can be exposed to the oral cavity, if the gingiva recedes too far CEMENTUM: types & width PU LP

AL 10 mm thick } The left of this Fig is misleading in suggesting that all cementum is cellular. The cervical half is thin and acellular - no cementocytes Cementum 700 mm thick

APICAL INTER-RADICULAR CEMENTUM Multi-rooted teeth usually have particularly thick & cellular cementum between the roots in an interradicular position CEMENTUM: Boundaries Cemento-enamel junction CEJ Dentino-cemental junction DCJ Ligamento-cemental junction APICAL FORAMEN

CEMENTUM: CEJ VARIATIONS E E E D D D CEMENTUM OVERLAP C/E most frequent BUTT JOINT

end-to-end GAP dentine exposed GROWTH OF CEMENTUM = PDL anchoring E E PDL fibers D D E

D Reactivated cementoblasts lay down cementoid Cementoid becomes another layer of cementum. Cells make more cementoid E D PDL fibers become imbedded in newly formed cementum Sharpeys fibers GROWTH OF CEMENTUM III

D D Further down the root cementoblasts proliferate Further down the root cementoblasts proliferated so that one cell can become imbedded as a cementocyte, while another remains on the surface as a cementoblast PDL fibers omitted. CEMENTUM MATRIX

Fine collagen fibrils - intrinsic PDL fibers (extrinsic) become imbedded in newly formed cementum MATRIX PROPORTIONS collagen fibrils and glycoproteins & proteoglycans Imbedded PDL fibers Sharpeys fibers - not specific to cementum Organic 35% mineral crystals 65%

Inorganic ROOT FORMATION REDUCED DENTAL EPITHELIUM DENTINE HERTWIGS ROOT SHEATH Epithelial diaphragm Root sheath breaks up, allowing sac mesenchymal cells to contact root

dentine Odontoblast recruitment site CEMENTOGENESIS START DENTINE Root sheath breaks up & lifts, allowing sac mesenchymal cells to contact root dentine PULP Dentine &/or Epithelial root sheath induces mesenchymal cells to become cementoblasts

Odontoblast recruitment site by root sheath: pulp signaling SEQUENCES Directions of cemental growth - outwards & apicalwards Dentine formed before cementum & cervical before apical Occlusal wear FUNCTIONAL ERUPTION & TOOTH MOVEMENT

Osteoclasts resorbing bone Bony interdental septum Osteoblasts laying down bundle bone PDL fibers incorporated in bone as Sharpeys fibers Cellular cementum added to apex Compensates for occlusal wear? Basil

CEMENTICLES IN PDL CEMENTUM: Defects CORONAL CEMENTUM spurs, etc, on enamel PU LP HYPERCEMENTOSIS excess deposition CEMENTOCLASIA - eroded cementum (occurs normally in decidual-tooth shedding) CEMENTUM: Repair

PU LP PU LP After cementoclasia, cementoblasts may fill in the defect with new cementum. This cycle can be repeated, and also occurs a little during shedding & after root fracture EXFOLIATION of DECIDUOUS MOLAR III ENAMEL DENTINE

Erosion of bone and the deciduous root is not steady & continuous, but may cease briefly, when some repair of eroded cementum & dentine can occur (by cementum). CEMENTICLES Hard mineralized bodies found in the periodontal ligament or partially imbedded in cementum PU LP

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