Lecture 3

covers the anatomic crown & varies in the thickness in different areas of the tooth.

• Enamel

• Pulp

• Dentin

• Cementum

enamel formation

cells responsible for amelogenesis; originate from the embryonic germ layer called ECTODERM

• yellowish white to grayish white

• translucent in nature

1. COLOR of underlying dentin

2. THICKNESS of enamel

3. Amount of STAINS in enamel

decreases gradually from cusps or incisal

edges to cemento-enamel junction.

Enamel Thickness

2.0 mm

2.3 – 2.5

2.5 – 3.0 mm

HARDEST CALCIFIED TISSUE in the human body.

has a high modulus of elasticity, high compressive strength and low tensile strength

2.8

• Inorganic contents: 95% – 98%

• Organic contents: 1 – 2%

• Water: 4 – 12%

largest mineral constituent

Ca10(PO4)6(OH)2

a) ENAMEL RODS or prisms b) ROD SHEATHS c) CEMENTING INTERROD SUBSTANCE

appear as oval, fish scale or keyhole shaped

• largest structural components

• has a head and tail

aligned perpendicularly to both the DEJ & the tooth surface in the deciduous & permanent teeth

groups of enamel rods that entwine with adjacent group of rods.

optical appearance of bands appear to be composed of alternating light and dark zones

considered as growth rings

incomplete circles of striae of retzius at the enamel surface formed a series of alternating grooves.

elevations between the grooves; continuous around a tooth & lie parallel to the cementoenamel junction.

hypomineralized structures of enamel rods & inter-rod substance that project between adjacent groups of enamel rods from the DEJ.

thin leaflike faults between enamel rod groups that extend from the enamel surface toward the DEJ sometimes extending into the dentin.

• pain receptors

• odontoblastic processes that cross the DEJ into the enamel.

interface of the enamel & dentin

failure or compromised coalescence of the enamel of developmental lobes results in a deep invagination in the groove area of the enamel surface.

noncoalesced enamel at the deepest point of a fossa.

covers the newly erupted tooth and is worn away by mastication and cleansing.

organic deposit which is a precipitate of salivary proteins.

• considered as a single tissue with mineralized

• dentin compromising the mature end product of cell differentiation and maturation.

forms the largest portion of the tooth structure

dentin formation.

cells responsible for dentinogenesis

• YELLOWISH in color

• harder than bone but softer than enamel

• Inorganic contents- 70%

• Organic contents - 20%

• Water- 5%

small canals that remain from the process of dentinogenesis & extend through the entire width of dentin, form the pulp to the DEJ

• dentin that immediately surrounds the dentinal tubules

• more mineralized than intertubular dentin and predentin.

• located between the dentinal tubules

• less mineralized than peritubular dentin

• main body of dentin.

layer that lines the innermost (pulpal) portion of dentin.

• PRIMARY DENTIN

• SECONDARY DENTIN

• TERTIARY DENTIN

• outlines the pulp chamber;

• forms the initial shape of the tooth;

• formed before root completion.

• forms on all internal aspects of the pulp cavity.

• Represents the continuing, but much slower, deposition of dentin by the odontoblasts after root formation has been completed.

• produce in reaction to noxious stimuli, such as caries or a restorative dental procedure.

also referred to as:

• REACTIVE,

• REPARATIVE or

• IRREGULAR SECONDARY DENTIN

results from aging or mild irritation & causes change in the composition of the primary dentin.

areas of dentinal tubules that are empty & are black when viewed microscopically.

• outward (exposed) portion of reactive

• sclerotic dentin where slow caries has destroyed formerly overlying tooth structure, leaving a hard, darkened cleanable surface.

• The most accepted theory of pain transmission

• This accounts for pain transmission by the small rapid movement of fluids that occur within the dentinal tubules

less effective pulpal barrier than superficial dentin near the DEJ or dentinoenamel junction.

composed of denatured collagen, hydroxyapatite & other cutting debris.

serves as a natural bandage over the cut dentinal tubules because it occludes many of the dentinal tubules with debris

formed from cutting debris forced into the tubules

soft connective tissue that occupies the central portion of the tooth.

• CORONAL PULP

• RADICULAR PULP

located in the pulp chamber in the crown portion of the tooth, including the pulp horns that are directed toward the incisal ridges & cusps tips.

located in the pulp canal/s in the root portion of the tooth.

• MYELINATED & UNMYELINATED FIBERS,

• ARTERIES,

• VEINS,

• LYMPH CHANNELS,

• CONNECTIVE TISSUE CELLS,

• INTERCELLULAR SUBSTANCE,

• ODONTOBLASTS,

• FIBROBLASTS,

• MACROPHAGES,

• COLLAGEN, &

• FINE FIBERS

• FORMATIVE

• NUTRITIVE

• SENSORY

• DEFENSIVE

production of primary & secondary dentin by the odontoblasts

supplies nutrients & moisture to the dentin through the blood vascular supply to the odontoblasts & their processes.

provides sensory nerve fibers within the pulp to mediate the sensation of pain.

related to its response to irritation by mechanical, thermal, chemical or bacterial stimuli

hard connective tissue that covers the roots of the teeth.

cementum formation

developed from undifferentiated mesenchymal cells in the connective tissue of the dental follicle

Inorganic material: 45 – 50%

• HYDROXYAPATITE

ORGANIC MATTER & WATER: 50 – 55%

are portions of the collagenous principal fibers of the periodontal ligament embedded in both the cementum & alveolar bone

• ACELLULAR

• CELLULAR

living tissue that does not incorporate cells into its structure & usually predominates on the coronal half of the root

occurs on the apical half

refers to the cementoenamel junction that is formed when cementum joins the enamel