(RestoDent) Enamel

7/31/2019 (RestoDent) Enamel

1/42

Is the art & science of the diagnosis,treatment, & prognosis of defects of teeth

which do not require full coveragerestorations for corrections.


2/42

A. Dentitions

B. Classes of human teeth

C. Structures of the teeth

D. Physiology of tooth forms


3/42

1. Deciduous dentition

2. Permanent dentition


4/42

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


5/42

I. Functions

II. Contours

III. Proximal contact area

IV. Embrasures


6/42

Main functions of teeth:1. Mastication

2. Esthetics

3. Speech

4. Protection of supporting tissues


7/42

Facial and lingual surfaces of the

teeth possess convexity for

protection and stimulation of thesupporting tissues during

mastication.


8/42

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


9/42

Anterior tooth showing

labial & lingual crest of

curvature. Both are in

the cervical third.


10/42

Maxillary posterior tooth

with the buccal crest of

curvature in the cervical

third and the lingual

crest of curvature in themiddle third.


11/42

A proximal view of a

maxillary 1st molar with

correct contour. Thegingiva is protected, but

receives proper

stimulation from food

flow during mastication.


12/42

An over contoured

maxillary 1st

molar. Thegingiva will suffer from

lack of stimulation as

food is deflected away

from the gingival tissues.


13/42

A maxillary 1st molar

with less than normalcontour. This contour

gives inadequate

protection to the

gingiva.


14/42

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.


15/42


16/42

The contact area of the remaining teeth going

posteriorly is located at the junction of the

incisal/occlusal thirds & middle thirds.


17/42

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


18/42

are V shaped spacesthat originate at the

proximal contact

areas betweenadjacent teeth.

facial, lingual, incisal

or occlusal & gingival

interdental papilla

fills the gingival

embrasure


19/42

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


20/42


21/42


22/42


23/42

1. enamel

2. pulp dentin complex

3. cementum


24/42

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


25/42

chemically - highly mineralized crystalline

structure

95% - 98% inorganic matter

hydroxyapatite

largest mineralconstituent

1 - 2 % organic content

4 % water content


26/42

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.


27/42

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


28/42

en

a

m

e

l

for maximal strength in tooth preparation,all enamel rods should be supported bydentin.

caries

d

en

t

i

n


29/42

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.


30/42

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.


31/42

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


32/42

ENAMEL SPINDLES odontoblasticprocesses that cross the DEJ into theenamel

may serve as pain receptors


33/42

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


34/42

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


35/42

The interface of the enamel & dentin is called theDENTINOENAMEL JUNCTION.

- scalloped or wavy in outline, with crest of the wavespenetrating toward the enamel.


36/42


37/42

Sound coalescence of the lobes results in

grooves

Faulty coalescence of the lobes results

fissure Enamel is incapable of repairing itself once

destroyed


38/42

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.


39/42

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


40/42

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


41/42

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


42/42

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

Documents

(RestoDent) Enamel