口腔生理學（含顎咬合）
Oral physiology (occlusion included)
學習目標
† 1. let the student to understand the
PDL and alveolar Bone
臺北醫學大學牙醫學系
張維仁
E-mail [email protected]
base knolwedge of oral physisology.
† 2.The student can firsther studying
the advance courses of dental
science.
參考資料
† 1.Applied Oral Physiology, 2nd ed.
Christopher L.B.Lavelle Butterworths
& Co.Lts, 1998
† 2.Physiology for dental students 1st
ed. D.B.Ferguson. Butterworths &
Co.Lts, 1998.
Enamel
ENAMEL
Physical characteristics
† Enamel's primary mineral is hydroxyapatite, which is a
† the hardest and most highly mineralized
crystalline calcium phosphate . The large amount of
minerals in enamel accounts not only for its strength but
also for its brittleness. Dentin, which is less mineralized
and less brittle, compensates for enamel and is
necessary as a support.
† Unlike dentin and bone, enamel does not contain
collagen. Instead, it has two unique classes of proteins
called amelogenins and enamelins. While the role of
these proteins is not fully understood, it is believed that
they aid in the development of enamel by serving as a
framework
substance of the body, and with dentin,
cementum, and dental pulp is one of the four
major tissues which make up the tooth. It is the
normally visible dental tissue of a tooth and
must be supported by underlying dentin. 96% of
enamel consists of mineral, with water and
organic material composing the rest
† Enamel varies in thickness over the surface of
the tooth and is often thickest at the cusp, up to
2.5 mm, and thinnest at its border, which is
seen clinically as the cementoenamel junction
(CEJ)
Structure of enamel
Scanning electron
microscope views of (A)
the enamel layer covering
coronal dentin, (B) the
complex distribution of
enamel rods across the
layer, (C and D) and
perspectives of the rodinterrod relationship when
rods are exposed (C)
longitudinally or (D) in
cross section. Interrod
enamel surrounds each
rod. R, Rod; IR, interrod;
DEJ, dentinoenamel
junction.
† The basic unit of enamel is called an enamel rod .
Measuring 4 μm - 8 μm in diameter an enamel rod,
formerly called an enamel prism, is a tightly packed mass
of hydroxyapatite crystals in an organized pattern . In
cross section, it is best compared to a keyhole, with the
top, or head, oriented toward the crown of the tooth, and
the bottom, or tail, oriented toward the root of the tooth.
† The area around the enamel rod is known as interrod
enamel. Interrod enamel has the same composition as
enamel rod, however a histologic distinction is made
between the two because crystal orientation is different in
each . The border where the crystals of enamel rods and
crystals of interrod enamel meet is called the rod sheath .
Hydroxyapatite
A and B, Highresolution
scanning electron
microscope
images showing
that crystals in rod
and interrod
enamel are similar
in structure but
diverge in
orientation.
P63/m
a=
9 .4
2A
P
Ca5(PO4)3OH
Ca
OH,F
D.R.Simpson, 1972)
Structure of enamel
† The arrangement of the crystals within each enamel rod is
highly complex. Both ameloblasts (the cells which initiate
enamel formation) and Tomes' processes affect the crystals'
pattern. Enamel crystals in the head of the enamel rod are
oriented parallel to the long axis of the rod . When found in the
tail of the enamel rod, the crystals' orientation diverges slightly
from the long axis.
† The arrangement of enamel rods is understood more clearly
than their internal structure. Enamel rods are found in rows
along the tooth, and within each row, the long axis of the
enamel rod is generally perpendicular to the underlying dentin .
In permanent teeth, the enamel rods near the cementoenamel
junction (CEJ) tilt slightly toward the root of the tooth.
Understanding enamel orientation is very important in
restorative dentistry, because enamel unsupported by
underlying dentin is prone to fracture.
Amelogenesis
Amelogenesis
1. Produces a partially mineralized
1.
(approximately 30%) enamel. Once the
full width of this enamel has been
deposited……..
2. Significant influx of additional mineral
coincident with the removal of organic
material and water to attain greater
than 96% mineral content. This mineral
influx makes the crystal formed during
the first step grow wider and thicker
2.
3.
Presecretory stage: differentiating ameloblasts
acquire their phenotype, change polarity,
develop an extensive protein synthetic
apparatus, and prepare to secrete the organic
matrix of enamel.
Secretory stage: ameloblsts elaborate and
organize the entire enamel thickness, resulting
in the formation of a highly ordered tissue.
Maturation stage: ameloblasts modulate and
transport specific ions required for the
concurrent accretion of mineral.
Scanning electron micrograph of the surface of a developing human
tooth from which ameloblasts have been removed. The surface
consists of a series of pits previously filled by Tomes’ processes the
walls of which are formed by interrod enamel.
The (A) first (initial) and (B) last (final) enamel layers are
aprismatic, that is, they do not contain rods.
A and B, Scanning electron microscope illustrations showing the complex
trajectory of rods in the inner two thirds of the enamel layer. B, The rods are
organized in groups exhibiting different orientations; this illustration shows
four adjacent groups.
Enamel protein
†
†
1.
2.
3.
4.
5.
†
†
†
6.
Four phases of enamel mineralization.
Amelogenins: 90% regulate growth in thickness and width,
nucleate cystals
Nonamelogenin
Ameloblastin: promote mineral formation and crstal elongaation
Enamelin: the molecule binds HA, crystal nucleation and growth
Sulfated glycoprotein
Tuftlin: cell signaling?? For DEJ
Enzymes
Metalloproteinase: enamelysin MMP20
Serines proteinase: bulk degradation
Phosphatase
Dentin phosphoprotein/ dentin sialoprotein
Striae of Retzius
Cross striations
Longitudinal ground
section showing
disposition of the
striae of Retzius
(arrows).the outermost
layer is the enamel,
the two sections
adjacent to the enamel
represent the dentin,
and the pulp chamber
is in the center.
In scanning electron microscopy, periodic
varicosities and depressions are seen along
enamel rods (R) in (A) rodent and (B) human
teeth, producing the impression of crossstriations along their length. IR, Interrod
enamel.
參與細胞增加而產生？
Human enamel is known to form a rate of approximately 4um/day
Enamel tufts & lamellae
Enamel tufts & lamellae
† Enamel tufts: abrupt changes in the
direction of groups of rods that arise
from different regions of the scalloped
DEJ
† Lamellae: longitudinal oriented defects
filled with organic material (enamel
organ or connective tissue)
Transverse ground section of enamel. Enamel tufts are the branched
structures extending from the dentinoenamel junction (DEJ) into the
enamel (arrowheads). The junction is seen as a scalloped profile.
Geologic faults
Enamel spindles
perikymata
Scanning electron
micrograph of the labial
surface of a tooth,
showing the perikymata.
(Courtesy D. Weber.)
Enamel spindles (arrows) in a ground section extend from the
dentinoenamel junction into the enamel and most frequently are
found at cusp tips.
Odontoblast processes extend into the ameloblast layer
Ground section of enamel
showing the relationship
between the striae of
Retzius and surface
perikymata.
The relationship between the striae of Retzius and surface
perikymata (arrows).
Aging
Defects of amelogenesis
† Discoloration
† Febrile diseases
† Reduced permeability
† Tetracycline-induced disturbaneces
† Modifications in the surface layer
† Fluoride ion >5ppm
Acid etching
Dentition of a patient who had two illnesses at separate times.
The enamel defects, separated by normal enamel, are clearly
visible.
Scanning electron micrographs of etching patterns in enamel. A, Type I
pattern: rod preferentially eroded. B, Type II pattern: rod boundary (interrod)
preferentially eroded; C, Type III pattern: indiscriminate erosion. D, Junction
between type I and type II etching zones.
Summary
介紹口腔中正常的組織，解剖、生理和
口腔組織的演化及生長過程，使同學們
對人體口腔有基本概念。
END