(restodent) enamel
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Is the art & science of the diagnosis,treatment, & prognosis of defects of teeth
which do not require full coveragerestorations for corrections.
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A. Dentitions
B. Classes of human teeth
C. Structures of the teeth
D. Physiology of tooth forms
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1. Deciduous dentition
2. Permanent dentition
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1. Incisors cutting or shearing instrument
2. Canines seizing, piercing & tearing of
food as well as in cutting
3. Premolars
dual role
* like canines in tearing of food
* like molars in the grinding of food
4. Molars
crushing, grinding & chewing offood to the smallest dimensions suitable
for deglutition
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I. Functions
II. Contours
III. Proximal contact area
IV. Embrasures
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Main functions of teeth:1. Mastication
2. Esthetics
3. Speech
4. Protection of supporting tissues
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Facial and lingual surfaces of the
teeth possess convexity for
protection and stimulation of thesupporting tissues during
mastication.
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An imaginarycurved lineencircling a toothat its greatest
bulge Also afford the
correct amount offrictional massageto the gingiva
Cleansingmechanism
General rule: Contour will vary
from tooth totooth
Height of contourfor both anteriorand posteriorteeth is in thecervical thirdEXCEPT lingual
crest of curvatureof posterior teethwhich is near themiddle third
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Anterior tooth showing
labial & lingual crest of
curvature. Both are in
the cervical third.
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Maxillary posterior tooth
with the buccal crest of
curvature in the cervical
third and the lingual
crest of curvature in themiddle third.
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A proximal view of a
maxillary 1st molar with
correct contour. Thegingiva is protected, but
receives proper
stimulation from food
flow during mastication.
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An over contoured
maxillary 1st
molar. Thegingiva will suffer from
lack of stimulation as
food is deflected away
from the gingival tissues.
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A maxillary 1st molar
with less than normalcontour. This contour
gives inadequate
protection to the
gingiva.
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1. Contacts with the proximal surfacesof the adjacent teeth which
prevents food impaction.
2. Adequate embrasure spacegingivally for the gingival tissue,
supporting bone, blood vessels and
nerves that serve the supportingstructures.
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The contact area of the remaining teeth going
posteriorly is located at the junction of the
incisal/occlusal thirds & middle thirds.
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Triangular-shaped
spaces between theteeth formed by the
bone on one side and
the proximal surfaces
and their contact area
on the other side
Normally filled with
gingival tissue Papillary gingiva
Interdental papilla
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are V shaped spacesthat originate at the
proximal contact
areas betweenadjacent teeth.
facial, lingual, incisal
or occlusal & gingival
interdental papilla
fills the gingival
embrasure
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Open space
Spillways
Named for their
location
Facial (buccal and
labial
Lingual
Incisal or occlusal
Gingival/cervical (ifinterproximal space
not occupied by
tissue or bone
Functions:
Allow food to be
forced away from
contact areas
Reduce the forcesof occlusal forces
Self cleansing
Permit a slight
amount ofstimulation to the
gingiva
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1. enamel
2. pulp dentin complex
3. cementum
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covers the anatomic crown & varies in thicknessin different areas of the tooth
enamel rods
color is mostly gray & is semi translucent
Formed by ameloblasts ( originate from the
embryonic germ layer called the ectoderm)
hardest substance of the human body but is
very brittle
http://e/direction%20of%20enamel%20rods.ppthttp://e/direction%20of%20enamel%20rods.ppt -
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chemically - highly mineralized crystalline
structure
95% - 98% inorganic matter
hydroxyapatite
largest mineralconstituent
1 - 2 % organic content
4 % water content
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Structurally, enamel iscomposed of millions ofenamel rods or prisms(largest structural
components), rod sheaths,& a cementing interrodsubstance
Enamel rods may vary innumber
Enamel rods are denselypacked & intertwined in awavy course & extends fromDEJ to the external surfaceof the tooth.
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enamel rods arealignedperpendicularly toboth the DEJ & thetooth surface in thedeciduous &permanent teethexcept in the
cervical region ofpermanent teethwhere they areslightly in apicaldirection
deciduous permanent
DEJ
Enamel
rod
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en
a
m
e
l
for maximal strength in tooth preparation,all enamel rods should be supported bydentin.
caries
d
en
t
i
n
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Groups of enamel rods that entwine
with adjacent group of rods & follow
a curving irregular path toward the
tooth surface forming GNARLEDENAMEL. Occurs in the cervical
regions and incisal & occlusal areas.
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Changes in direction ofenamel prisms produce
an optical appearancecalled HUNTER-SCHREGER bands (appear as alternate light& dark zones of varying
width).Anterior teeth locatedin the incisal surfacesMolars occurs near thecervical region to thecusp tips.
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ENAMEL TUFTS arehypomineralizedstructures of enamel rods
& inter-rod substance thatproject between adjacentgroups of enamel rodsfrom the DEJ
ENAMEL LAMELLAE arethin leaflike faultsbetween enamel rod
groups that extend fromthe enamel surface towardthe DEJ sometimesextending into the dentin.
- contain mostlyorganic materials which isa weak area &
predisposing a tooth to theentry of bacteria & dentalcaries.
ENAMEL SPINDLES d bl i
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ENAMEL SPINDLES odontoblasticprocesses that cross the DEJ into theenamel
may serve as pain receptors
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Enamel rods are formedlinearly by successiveapposition of enamel indiscrete incrementsresulting in structure &
mineralizations called theINCREMENTAL STRIAE OFRETZUIS.- considered as growthrings- in horizontal sections ofa tooth it appear asconcentric circles;
- in vertical sections,symmetric arc patterndescending obliquely tothe cervical region &terminating at the DEJ
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IMBRICATION LINES PICKERILL
incomplete circles of striae of retzuis at the enamel
surface formed a series of alternating grooves
PERIKYMATAelevations between the
grooves; continuous around a tooth& lie parallel to the cementoenamel junction
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The interface of the enamel & dentin is called theDENTINOENAMEL JUNCTION.
- scalloped or wavy in outline, with crest of the wavespenetrating toward the enamel.
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Sound coalescence of the lobes results in
grooves
Faulty coalescence of the lobes results
fissure Enamel is incapable of repairing itself once
destroyed
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Final act of the ameloblast cell is
secretion of a membrane covering the end
of enamel rod. This layer is referred to asNASMYTH MEMBRANE or PRIMARY ENAMEL
CUTICLE.
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Enamel is very hard & dense structure, it is
permeable to certain ions & molecules.
The route of passage is through structuralunits that are hypomineralized & rich in
organic content such as rod sheath,
enamel cracks & other defects
Water is the transporting medium through
small inter crystalline spaces.
Enamel permeability decreases with age.
This decrease is referred to as ENAMELMATURATION
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Enamel is soluble when exposed to an acidmedium. Solubility of enamel increasesfrom the enamel surface to the DEJ.
Fluoride present during enamel formation solubility of enamel is decreased.Trace amounts of fluoride stabilize enamelby:
Lowering acid solubility Decrease the rate of demineralization Enhancing the rate of remineraization
Topical fluoride increase resistance todental caries
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Acid etching the enamel surfacemicromechanical bonding of composite
restorative materials Etchant is a 35% to 50% solution ofphosphoric acid Etching produces an irregular pittedsurface with numerous undercuts Composite or pit & fissure sealant isbonded to the enamel surface by RESIN TAGSformed in the acid etched enamel rodstructure
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Its hardness makes it resistant to thefriction of ordinary use
The curvatures of enamel rods probablyincrease the strength of the enamel
The presence of pits and fissuresinfluences the occurrence of dental caries
The arrangement of enamel rods and the
presence of areas of less mineralizationinfluence the pattern and speed ofprogress of dental caries
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