Morphology and Histology of Primary and Permanent tooth, Dept of Pedodotnics and Preventive Dentistry
260
Morphology And Morphology And Histology of Primary Histology of Primary And Permanent teeth And Permanent teeth R.Hemalath R.Hemalath a a 1 1 st st Yr Yr
Transcript
Morphology And Histology of Primary And Permanent teeth
R.Hemalatha st 1 Yr
Introduction and Nomenclature The teeth are arranged in upper
and lower arches. Those teeth in the upper arch are termed
maxillary, because they are set in the upper jaw, which is the
maxilla (Plural - maxillae). The teeth in the lower arch are termed
mandibular, because they are located in the lower jaw, which is the
mandible. The mandible is the movable member of the two jaws, while
the maxilla is stationary. B. The imaginary vertical line which
divides each arch, as well as the body, into two approximately
equal halves, is the midline. Strictly speaking, this vertical
division is not a one-dimensional line at all, but rather a
two-dimensional plane, termed the mid-sagittal lane.
The two approximately equal portions of each arch divided by
the midline are termed g&rants, since there are four in the
entire mouth. They are termed: maxillary (upper) right. maxillary
(upper) left. mandibular (lower) right. mandibular (lower) left The
manner in which the mandibular teeth contact the maxillary teeth is
called occlusion. The term for the process of biting or chewing of
food is mastication midline
Classification of Dentitions: A. The human dentition is termed
heterodont, which means it is comprised of different types, or
classes, of teeth to perform different functions in the mastication
process. In comparison, a homodont dentition is one in which all of
the teeth are the same in form and type. This sort of dentition is
found in some of the lower vertebrates. B. Furthermore, man has two
separate sets of teeth, or dentitions. This is termed diphyodonta
as opposed to monophyodont when there is only one set of teeth, and
polyphyodont, when more than two. or continuous, sets of teeth are
developed throughout life.
In man, the two dentitions are termed deciduous and permanent,
while the transitional phase when both deciduous and permanent
teeth are present is called the mixed dentition period. 1.
Deciduous dentition - The teeth of the first, or primary dentition.
They are so named because they are shed like the leaves of
deciduous trees in autumn. They erupt into the mouth from about six
months to two years of age. Normally there are 20 total deciduous
teeth. Other non-scientific names for the deciduous teeth include
"milk" teeth, " baby" teeth, and "temporary" teeth. 2. Permanent
dentition -The teeth of the second, or adult dentition. Normally,
there are 32 permanent teeth and they erupt from 6-21 years of
age.
Classification of Teeth A. Permanent Dentition: As was pointed
out, man is a heterodont, which means that more than one type of
tooth is found in the human dentitions. Each complete quadrant of
the permanent dentition contains eight teeth of differing type and
function, as follows: 1. Incisors (2) - The incisors are the two
teeth of each quadrant which are closest to the midline. They are
named central and lateral incisors. There functions in mastication
are biting, cutting, incising and shearing. There are four
permanent incisors per arch, and a total of eight in the mouth. 2.
Canine (1) - The canine is the third tooth from the midline in each
quadrant. Its function in mastication is cutting, tearing,
piercing, and holding. It also is called a cuspid. There are two
permanent canines per arch, and a total of four in the mouth.
3. Premolars (2) - The premolars are the fourth and fifth teeth
from the midline. They are termed first and second premolars. Their
masticatory role is tearing, holding, and grinding. They are also
called bicuspids. As with the incisors, there are four per arch,
and eight total premolars. 4. Molars (3) - The molars are the
sixth, seventh, and eighth teeth from the midline. They are termed
first, second, and third molars. They are also called six years
molar, twelve year &, and wisdom tooth, in that order. Their
masticatory function is grinding. There are six permanent molars
per arch, and twelve total permanent molars. It can thus be seen
that there are 16 permanent teeth in a complete arch, and a total
of 32 teeth in the permanent dentition.
B. Deciduous Dentition: Each quadrant of man's deciduous
dentition contains the following types of teeth, all of which have
a function similar to their permanent complements: 1. Incisors (2),
which are named central and lateral incisors. 2. Canine (I), or
cuspid. 3. Molars (2), which are named first and second molars.
Therefore, there are five deciduous teeth per quadrant. ten per
arch. and a total of twenty in the primary dentition. When compared
to the permanent teeth, the primary dentition contains an identical
number of incisors and canines, but has no premolars and one less
molar per quadrant.
Dentition Periods and Succedaneous Teeth: It has been pointed
out that man has two dentitions, but three periods of
dentition,since the deciduous and permanent dentitions overlap in
time. These periods are summarized in the following manner: 1.
Primary dentition period - That period during which only deciduous
teeth are present, and occurs from approximately six months to six
J ears of age. The primary dentition period ends at about age six,
with the eruption of the first permanent tooth. normally the
mandibular first molar. 2. Mixed dentition period - That period
during which both deciduous and permanent teeth are present. and
lasts from approximately 6years to 12 years of age. The mixed
dentition period ends and the permanent dentition period begins at
round age twelve. with the exfoliation of the last deciduous tooth,
normally the maxillary second molar.
3. Permanent dentition period- That period when only permanent
teeth are present, and which begins at approximately twelve years
of age and continues through the rest of life.
B. In order for a permanent tooth to erupt into a space where a
deciduous tooth is located, the deciduous tooth must first be shed,
or exfoliated. The natural process by which deciduous roots are
"melted away" to allow for exfoliation is termed resorption. C.
Permanent teeth that replace exfoliated deciduous teeth are called
succedaneous teeth, which simply means "succeeding" deciduous
teeth. Since there are twenty deciduous teeth to be replaced, there
must be twenty succedaneous teeth. The permanent teeth that are
also succedaneous teeth include the incisors and canines, which
replace their deciduous counterparts, and the premolars, which
replace the deciduous molars. Therefore, the only permanent teeth
which are not succedaneous are the molars. It may be said, then,
that all succedaneous teeth are permanent teeth, but all I
permanent teeth are not succedaneous teeth.
Dental Formulae: A. Dental formula - A number and letter
designation of the various types of teeth found in a dentition. The
dental formula indicates the dentition of only one side of the
mouth, but includes both the upper and lower quadrants, and so must
be multiplied by a factor of two to provide the number of teeth in
the entire dentition. B. Thus, the dental formula for man's
permanent dentition is as follows: I-2 : C 1 : P-2 : M-3 2 1 2
3
The deciduous dentition of man has the following dental
formula: I-2 : C 1 : M-2 2 1 2 It should be kept in mind that
animals other than man may have differing dental formulae
General Eruption Pattern: Both the deciduous and permanent
dentitions have a general order, or pattern, of eruption. For the
deciduous dentition, this pattern normally is as follows: A.
Deciduous Dentition: Eruption Sequence 1. Mandibular central
incisor 2. Mandibular lateral incisor 3. Maxillary central incisor
4. Maxillary lateral incisor 5. Mandibular first molar 6. Maxillary
first molar 7. Mandibular canine 8. Maxillary canine 9. Mandibular
second molar 10. Maxillary second molar
As a general rule, mandibular deciduous teeth normally precede
their maxillary counterparts in eruption. It can also be said that
the deciduous teeth normally erupt in order from the front of the
mouth toward the back, even though the canines in each quadrant
normally erupt after the first molars.
Deciduous Dentition: Normal Eruption Time Erruption Age
Mandible Order Maxilla Central Incisor 6 1 7 'I2 Lateral Incisor 7
2 9 Canine 16 4 19 First Molar 12 3 14 Second Molar 20 5 24 Order 1
2 4 3 5
Permanent Dentition: Normal Eruption Sequence 1. Mandibular
first molar 2. Maxillary first molar 3. Mandibular central incisor
4. Mandibular lateral incisor 5. Maxillary central incisor 6.
Maxillary lateral incisor 7. Mandibular canine 8. Mandibular first
premolar 9. Maxillary first premolar 10. Mandibular second premolar
11. Maxillary second premolar 12. Maxillary canine
13. Mandibular second molar 14. Maxillary second molar 15.
Mandibular third molar 16. Maxillary third molar As can be seen.
the permanent mandibular teeth normally precede their maxillary
counterparts in eruption. as was also the pattern with the
deciduous teeth. If the first molar's eruption sequence is ignored,
the permanent mandibular teeth exhibit a perfect anterior to
poterior order. However, in the maxillary arch not only is the
firstmolar out of order the canine normally follows both
premolars.
Eruption Age Mandible Order Central Incisor 6-7 2 Lateral
Incisor 7-8 3 Canine 9-10 4 First Pre-molar 10-11 5 Second Pre-
Molar 11-12 6 First Molar 6-7 1 Second Molar 11-13 7 Third Molar
17-21 8 Maxilla Order 7-8 2 8-9 3 11-12 6 10-11 4 11-12 5 6-7 1
12-13 7 17-21 8
It should be noted that the eruption sequences and dates
presented here are based on the only studies available, which were
conducted a number of years ago. More contemporary data has
suggested that, in some cases, these figures may not be entirely
correct. It has also been suggested that there really may not be a
"normal eruption pattern which is true for both sexes, and across
all racial groups. In other words, the most common eruption
sequences may occur in only a relatively small percentage of the
total population. However, until the results of longitudinal
studies for North American populations are available, "old
sequences and dates will be used.
Numbering Systems: Numbering systems in dentistry serve as
abbreviations. Instead of writing out the entire name of a tooth,
such as permanent maxillary right central incisor, it is much
simpler to assign it a number, letter, or symbol, such as #8 for
the universal numbering system. Of the many systems, the three most
commonly used will be described. A. Universal Numbering System: The
numbering system which enjoys the widest use today is the universal
system. It employs a different number (1-32) in a consecutive
arrangement for all permanent teeth, and a number-letter (ld-20d)
for each of the deciduous teeth. 1. Permanent Teeth - The universal
numbering system assigns a specific number to each permanent tooth.
The upper right third molar is #I, the upper right second molar #2,
and so forth around the entire maxillary arch to the upper left
third molar, which is #16. Since there are no more permanent teeth
in the maxillary arch, the succession drops to the lower left third
molar which is #17, and continues around the entire mandibular arch
where the lower right third molar is #32. For example, tooth #11 is
the permanent maxillary left canine.
2. Deciduous Teeth - The twenty teeth of the deciduous
dentition are numbered in the same manner as are the permanent
teeth (1-20), except that a small (d) is added as a suffix to each
number to designate deciduous. The deciduous upper right second
molar is thus #Id, while the upper left second molar is #10d. The
lower right canine, for example, is #18d. The most common system in
use today for designating deciduous teeth uses the capital letters
A through T. The maxillary right deciduous second molar is tooth A
and the order progresses in the manner used with the 1-32 system
for permanent teeth, so that the mandibular right deciduous second
molar is tooth T. B. Palmer Notation Method: Another commonly used
numerical and letter notation scheme for identifying an individual
tooth utilizes a simple symbol, which differs for each of the four
quadrants. In addition, the numbers 1 through 8 are used to
identify permanent central incisor through third molar in the
specified quadrant. Letters A through E, with the quadrant symbol,
are used for the deciduous dentition
FDI System: The Federation Dentaire Internationale (FDI), the
international dental organization, has introduced a new numbering
system, which is an attempt at standardization throughout the
world. Although presently not in worldwide use, it may be in the
future. It is a simple binomial system, which includes both
permanent and deciduous teeth. The first of the two numbers
identifies the quadrant, and whether the tooth is permanent or
deciduous, as follows: 1 - Permanent maxillary right quadrant 2 -
Permanent maxillary left quadrant 3 - Permanent mandibular left
quadrant 4 - Permanent mandibular right quadrant 5 - Deciduous
maxillary right quadrant 6 - Deciduous maxillary left quadrant 7 -
Deciduous mandibular left quadrant 8 - Deciduous mandibular right
quadrant
The second number identifies the particular tooth in the
quadrant, exactly like the Palmer notation method for permanent
teeth (1-8). The deciduous teeth in each quadrant are numbered
(1-5), the number increasing in size from the midline posteriorly.
Examples in notation utilizing the FDI system are as follows: 18 -
Permanent maxillary right third molar 27 - Permanent maxillary left
second molar 36 - Permanent mandibular left first molar 45 -
Permanent mandibular right second premolar 54 - Deciduous maxillary
right first molar 63 - Deciduous maxillary left canine 72 -
Deciduous mandibular left lateral incisor 81 - Dbciduous mandibular
right central incisor
As review, the first designation in the above list (18) can be
analyzed as follows: 1-The first number indicates that the tooth is
located in the permanent maxillary right quadrant. 8-The second
number indicates that the tooth is eighth from the midline, and
thus is a third molar.
General Oral and Dental Anatomy: brief definition and
description of the various anatomical features of a normal tooth,
and its supporting structures, include the following: A. Dental
Structures: 1. Anatomical crown - That portion of the tooth which
is covered by enamel. 2. Clinical crown - That portion of the tooth
which is visible in the mouth. The clinical crown may, or may not,
correspond to the anatomical crown, depending on the level of the
tooth's investing soft tissue, and so may also include a portion of
the anatomical root. As can be seen from this description, the
clinical crown may be an ever changing entity throughout life,
while the anatomical crown is a constant entity.
3. Anatomical root - That portion of the tooth which is covered
with cementum. 4. Clinical root - That portion of the tooth which
is not visible in the mouth. Again, the clinical root is an ever
changing entity, and may, or may not, correspond to the anatomical
root. Note: In the dental literature, the modifying terms
"clinical" and "anatomical are not often used with crown or root,
but the intended meaning is most often "anatomical" and so will be
used in this manner hereafter. 5. Enamel - The hard, mineralized
tissue which covers the dentin of the anatomical crown of a tooth.
It is the hardest living body tissue, but is brittle, especially
when not supported by sound underlying dentin. 6. Dentin - The hard
tissue which forms the main body of the tooth. It surrounds the
pulp cavity, and is covered by the enamel in the anatomical crown,
and by the cementum in the anatomical root. The dentin constitutes
the bulk, or majority, of the total tooth tissues, but because of
its internal location, is not directly visible in a normal
tooth.
7. Cementum - The layer of hard, bonelike tissue which covers
the dentin of the anatomical root of a tooth. 8. Cervical line -
The identifiable line around the external surface of a tooth where
the enamel and cementum meet. It is also called the cemento-enamel
junction or CEJ. The cervical line separates the anatomical crown
and the anatomical root, and is a constant entity. Its location is
in the general area of the tooth spoken of as the neck or cervix 9.
Dentino-enamel junction or DEJ - The internal line of meeting of
the dentin and enamel in the anatomical crown of a tooth. 10.Pulp -
The living soft tissue which occupies the pulp cavity of a vital
tooth. It contains the tooth's nutrient supply in the form of blood
vessels, as well as the nerve supply.
Pulp Cavity - The entire internal cavity of a tooth which
contains the pulp. It consists of the following entities: a. Pulp
canal(s) - That portion of the pulp cavity which is located in the
root(s) of the tooth. and may also be called the root canal(s). b.
Pulp chamber - The enlarged portion of the pulp cavity which is
found mostly in the anatomical crown of the tooth. c. Pulp horns -
The usually pointed incisal or occlusal elongations of the pulp
chamber which often correspond to the cusps, or lobes of the
teeth
1 1. Pulp Cavity - The entire internal cavity of a tooth which
contains the pulp. It consists of the following entities: a. Pulp
canal(s) - That portion of the pulp cavity which is located in the
root(s) of the tooth. and may also be called the root canal(s). b.
Pulp chamber - The enlarged portion of the pulp cavity which is
found mostly in the anatomical crown of the tooth. c. Pulp horns -
The usually pointed incisal or occlusal elongations of the pulp
chamber which often correspond to the cusps, or lobes of the
teeth.
B. Supporting Structures: 1. Alveolar process - The entire bony
entity which surrounds and supports all the teeth in each jaw
member. 2. Alveolus (Plural - alveoli) - The bony socket, or
portion of the alveolar process, into which an individual tooth is
set. 3. Periodontal ligament (membrane) - The fibrous attachment of
the tooth cementum to the alveolar bone. 4. Gingiva (Plural -
gingivae) - The "gum" or "gums", or the fibrous tissue enclosed by
mucous membrane that covers the alveolar processes and surrounds
the necks of the teeth.
Primary Maxillary Central Incisor Primary Maxillary Central
Incisor Labial Aspect Smooth labial surface. The M-D diameter is
greater than the cervicoincisal length. Incisal edge is nearly
straight Developmental lines are usually not seen. The root is
cone-shaped with even, tapered sides. The root length is greater
than crown length than that of the permanent central incisor.
Lingual Aspect Well-developed marginal ridges ,highly developed
cingulum seen The cingulum extends up toward the incisal ridge
,practically dividing into a mesial and distal fossa. The root
narrows lingually ,whereas its flat surface labially..
Mesial and Distal Aspects Similar - The measurement of the
crown at the cervical third shows the crown to be wide in relation
to its total length. The curvature of the cervical line is curving
towards the incisal ridge The cervical curvature distally is less
than the curvature mesially The root is cone-shaped with even,
tapered sides, apex is blunt Usually Mesial has a developmental
groove and distal is generally Convex
The Pulp Cavity Consist of 3 slight projections on incisal
border i.e. 3pulp horns Chamber tapers in M-D diameter cervically,
widest at cervical region Labiolingually Pulp chamber and Canal are
larger than permanent ones. No distinct demarcation between canal
&chamber Pulp canal tapers evenly until ending in apical
foramen
Incisal Aspect The incisal edge is centered over the main bulk
of the crown and is relatively straight. The labial surface is much
broader and also smoother than the lingual surface. The lingual
surface tapers towards the cingulum.
Primary Maxillary Lateral Incisor Similar to the central
incisor from all aspects, but its dimensions differ width. The
disto-incisal angles of the crown are more rounded than those of
the central incisor.
Primary Maxillary Lateral Incisor The pulp chamber follows the
contour of the tooth, as does the canal The root has similar shape,
but is longer, thinner and tapering
PRIMARY MANDIBULAR CENTRAL INCISOR Labial Aspect Flat face ,No
developmental grooves Mesial and distal sides of the crown are
tapered evenly from the contact areas, with the measurement being
less at the cervix Crown is wide in proportion to its length The
heavy root trunk permanent maxillary lateral incisor. The root is
long and evenly tapered down to the apex, which is pointed. The
root is almost twice the length of the crown
Lingual Aspect The marginal ridges, cingulum - located easily
Middle third may hay a flattened surface/ incisal third slight
concavity lingual fossa. Lingual Convergence of the crown and root
is seen
Mesial Aspect The incisal ridge is centered over the center of
the root The convexity of the cervical contours labially and
lingually at the cervical third is Most pronounced More pronounced
by far than the prominences found on a permanent mandibular central
incisor. These cervical bulges are important. The mesial surface of
the root is nearly flat and evenly tapered; the apex blunt.
Distal Aspect Outline : Opp of mesial Cervical line is less
curved. Developmental depression is evident on the distal side of
the root Pulp Cavity Widest mesiodistally at the roof
Labiolingually the is widest at the cingulum Oval in appearance,
tapers as it reaches apex Definite demarcation between chamber and
canal
Incisal Aspect The incisal ridge is straight and bisects the
crown labiolingually. A definite taper is evident toward the
cingulum on the lingual side. The labial surface from this view
presents a flat Mir surface that is slightly convex, whereas the
lingual surface presents a flattened surface that is slightly
concave.
MANDIBULAR LATERAL INCISOR The fundamental outlines are similar
to those primary central incisor. These two teeth supplement each
other in function. Somewhat larger in all measurements except
labiolingually, where the two teeth are practically identical.
Cingulum of the lateral incisor may be a little more generous than
that of the central incisor Crown root ratio is more in lateral
than in central
MANDIBULAR LATERAL INCISOR The lingual surface of the crown
between the marginal ridges may be more concave. Incisal ridge
tends to slope downward distally. This design lowers the distal
contact area apically, so that proper contact may be made with the
mesial surface of the primary mandibular canine
Pulp Cavity Oval in appearance, tapers as it reaches apex No
demarcation between chamber and canal
Primary Maxillary Canine LABIAL SURFACE The crown is more
constricted at the cervix in relation to its M-D width. The mesial
and distal surfaces are more convex. It has a long, well-developed,
sharp cusp. The cusp on the primary canine is much longer and
sharper ,than permanent Contact areas are at the same level, which
is not the same in permanent The Mesial slope of the cusp is longer
than the distal slope The root of the primary canine is long,
slender, and tapering and is more than twice the crown length
LINGUAL SURFACE Shows well pronounced enamel ridges that merge
with each other This lingual ridge divides the lingual surface into
shallow mesiolingual and distolingual fossae The root of this tooth
tapers lingually and is usually inclined above the middle
third
Mesial Aspect Similar to that of the lateral and central
incisors. Difference in proportion is evident. The measurement
labiolingually at the cervical third is much greater. * This
permits resistance against forces the tooth must withstand during
function. * The function of this tooth is to punch, tear, and
apprehend food material. Distal Aspect The distal outline of this
tooth is the reverse of the mesial aspect. Only difference being,
Cervical line towards the cusp ridge is less than on the mesial
surface.
Pulp Cavity There is a little demarcation between pulp chamber
and the canal. The canal tapers as it approaches the apex. Pulp
chamber follows the external contour of teeth. Central pulpal horn
is projecting incisally.
Incisal Aspect diamond-shaped The angles that are found at the
contact areas mesially and distally are more pronounced and less
rounded than those on permanent canines. Mesial cusp slope is
longer than the distal cusp slope, i.e for Intercuspation with the
lower
MANDIBULAR CANINE Little difference in function between the
mandibular canine and the maxillary canine. The crown is perhaps
0.5 mm shorter, The root is at least 2 mm shorter . The M-D
measurement at the root trunk is greater when compared with its M-D
measurement at the contact areas, than is that of the maxillary
canine It is "thicker" accordingly at the "neck" of the tooth.
The deciduous maxillary canine is much larger labiolingually
The cervical ridges labially and lingually are not quite as
pronounced as those found on the maxillary canine. The greatest
variation is the distal cusp slope is longer than the mesial
slope.
Pulp Cavity Wide mesiodistally as labiolingually No cliff
between canal &chamber Ends in marked constriction at the
apex
PRIMARY MAXILLARY FIRST MOLAR Buccal Aspect The widest
measurement of the crown of the maxillary first molar is at the
contact areas mesially and distally From these points, the crown
converges toward the cervix, with the mm at the cervix being fully
2 mm less than the mm at the contact areas. * This furnishes a
narrower look to the cervical portion of the crown and root, than
compared to permanent maxillary first molar.
The occlusal line is slightly scalloped but with no definite
cusp form. Smooth buccal surface, little evidence of developmental
grooves seen. Relatively smaller than Second molar THE ROOT The
roots of the maxillary first molar are slender and long, and they
spread widely. All three roots may be seen from this aspect. The
distal root is shorter than the mesial one. The bifurcation of the
roots begins almost immediately at the site of the cervical line
(CEJ). * Actually which includes a trifurcation, and this is a
characteristic of all primary molars, whether maxillary or
mandibular. Permanent molars do not possess this characteristic. *
The root trunk on permanent molars is much heavier, with a greater
distance between the cervical lines to the points of bifurcations
a
Lingual Aspect The general outline of the lingual aspect of the
crown is similar to that of the buccal aspect. The crown converges
considerably in a lingual direction, which makes the lingual
portion calibrate less mesiodistally than the buccal portion.
The mesiolingual cusp is the most prominent cusp on this tooth.
It is the longest and sharpest cusp. The distolingual cusp is
poorly defined; it is small and rounded. The distobuccal cusp may
be seen, since it is longer and better developed than the
distolingual cusp. All three roots also may be seen from this
aspect. The lingual root is larger than the others.
Mesial Aspect The dimension of cervical third is greater than
occlusal third The mesiolingual cusp is longer and sharper than the
mesiobuccal cusp. A pronounced convexity is evident on the buccal
outline of the cervical third *characteristic bulge It actually
gives the impression of overdevelopment in this area
The mesiobuccal and lingual roots are visible The distobuccal
root is hidden behind the mesiobuccal root. The lingual root from
this aspect looks long and slender and extends lingually to a
marked degree. It curves sharply in a buccal direction above the
middle third
Distal Aspect From the distal aspect, the crown is narrower
distally than mesially; it tapers markedly toward the distal end.
The distobuccal cusp is long and sharp, and the distolingual cusp
is poorly developed. The prominent bulge seen from the mesial
aspect at the cervical third does not continue distally.
The cervical line may curve occlusally, or it may extend
straight across from the buccal surface to the lingual surface. All
three roots may be seen from this angle, but the distobuccal root
is superimposed on the mesiobuccal root so that only the buccal
surface and the apex of the latter may be seen. The point of
bifurcation of the distobuccal root and the lingual root is near
the CEJ and, as described earlier, is typical.
Occlusal Aspect The crown outline converges lingually. The
crown also converges distally. Outline however is rectangular, with
the shortest sides of the rectangle represented by the marginal
ridges The occlusal surface has a central fossa. A mesial
triangular fossa is just inside the mesial marginal ridge, with a
mesial pit in this fossa and a sulcus with its central groove
connecting the two fossae. A well-defined buccal developmental
groove divides the mesiobuccal cusp and the distobuccal cusp
occlusally.
Supplemental grooves radiate from the pit in the mesial
triangular fossa as follows: -one buccally, one lingually, and one
toward the marginal ridge,with the last sometimes extending over
the marginal ridge mesially. Oblique ridge. The distal marginal
ridge is thin and poorly developed in comparison with the mesial
marginal ridge
Pulp Cavity Pulp Cavity Consists of a chamber Straight 3 pulpal
canals corresponding to 3 roots Variations from this basic design
may be present as anastomoses & branchings. 3-4 pulp horns Pulp
horn sizes MB>ML>DB
Mesio-buccal horn is the largest of pulpal horns occupying a
prominent portion of pulp chamber. Mesiolingual pulpal horn is
second in size,quite angular & sharp. Distobuccal horn is
smallest , sharp & occupies distobuccal angle. Occlusal view of
the pulp chamber resembles somewhat a triangle with rounded
corners
Primary Maxillary Second Molar Buccal aspect The
characteristics resemble those of first permanent molars , but is
smaller. The buccal view shows two well defined buccal cusps with
buccal development grooves between them. The crown is narrow at the
cervix in comparison with its M-D measurement at the contact
areas.
The crown is much larger then that of first primary molar Roots
are slender , are much longer and heavier ten maxillary first molar
The point of bifurcation between buccal roots is close to the
cervical line of crown. The two buccal cusps are more nearly equal
in size and development than those of permanent max 1st molar.
Lingual Aspect 3 cusps seen Mesiolingual cusp- large and well
developed Distolingual cusp- well developed more then primary 1st
molar Third supplemental cusp- apical to mesiolongual cusp called
the tubercle of carabelli, or fifth cusp The cusp is poorly
developed and merely acts as a buttress or supplement to bulk of
mesiolingual cusp.
If the tubercle if carabelli seems to be missing, some traces
of developmental lines or dimples A well defined developmental
grooves separates mesiolingual cusp from distolingual and connects
with developmental groove which outlines with fifth cusp All three
roots are visible from this aspect Lingual root is large and thick
in comparison with other two roots Approx the same length as
mesiobuccal root .
Mesial Aspect The crown has a typical molar outline that
resembles that of the permanent molars very much The crown appears
short because of its width buccolingually in comparison with its
length. The crown of this tooth is usually only about 0.5 mm longer
than the crown of the first deciduous molar, but the buccolingual
measurement is 1.5 t 2 mm greater. In addition, the roots are 1.5
to 2 mm longer.
The mesiolingual cusp of the crown with its supplementary fifth
cusp appears large in comparison with the mesiobuccal cusp. The
mesiobuccal cusp from this angle is relatively short and sharp.
Little curvature to the cervical line is evident. Usually, it is
almost straight across from buccal surface to lingual surface.
The mesiobuccal root from this aspect is broad and flat. The
lingual root has somewhat same curvature as of 1 molar. The
mesiobuccal root extends lingually far out beyond the crown
outline. The point of bifurcation between the mesiobuccal root and
the lingual root is 2 or 3 mm apical to the cervical line of the
crown
Distal Aspect From both the distal and the mesial aspects, the
outline of the crown lingually creates a smooth, rounded line,
whereas a line describing the buccal surface is almost straight
from the crest of curvature to the tip of the buccal cusp. The
distobuccal cusp and the distolingual cusp are about the same in
length. The cervical line is approximately straight, as was found
mesially
All three roots are seen from this aspect, although only a part
of the outline of the mesiobuccal root may be seen, since the
distobuccal root is superimposed over it. The distobuccal root is
shorter and narrower than the other roots. The point of bifurcation
between the distobuccal root and the lingual root is more apical in
location than any of the other points of bifurcation.
Occlusal Aspect From the occlusal aspect, this tooth resembles
the permanent first molar It is somewhat rhomboidal and has four
well-developed cusps : mesiobuccal, distobuccal, mesiolingual,
distolingual, and fifth supplemental cusp. The buccal surface is
rather flat with the developmental groove between the cusps less
marked than that found on the first permanent molar.
Pulp Cavity The pulp cavity consist of a pulp chamber & 3
pulp canals corresponding to three roots. These canals leave floor
of chamber at the mesiobuccal & distobuccal corners & from
lingual area. Pulp chamber has 4 pulpal horns, a fifth horn
projecting from lingual aspect of mesiolingual horn may be present.
The mesiobuccal pulp horn is largest, pointed & extends
occlusally
Mesiolingual pulp horn is second in size, when combined with
fifth horn it presents a bulky appearance. Distobuccal pulp horn is
third in size, joining mesiolingual pulp horn as slight elevation.
Distolingual pulp horn is shortest & extends only slightly
above occlusal level.
Primary Mandibular First Molar It appears strange and primitive
Buccal Aspect The mesial outline of the crown is almost straight
from the contact area to the cervix The distal portion converges
toward the cervix more than usual, so that the contact area extends
distally to a marked degree. The distal portion of the crown is
shorter than the mesial portion, with the cervical line dipping
apically where it joins the mesial root.
No developmental groove is evident between them The mesial cusp
is larger than the distal cusp. A developmental depression dividing
them (not a groove) extends over to the buccal surface. THE ROOT
The roots are long and slender, and they spread greatly at the
apical third beyond the outline of the crown. The buccal aspect
emphasizes the strange, primitive look of this tooth.
Lingual Aspect Mesially, the crown and root converge lingually
to a marked degree Distally, the opposite is true of both crown
& root. The distolingual cusp is rounded. The mesiolingual cusp
is long and sharp at the tip. The sharp and prominent mesiolingual
cusp is an outstanding characteristic Mesial marginal ridge is well
developed. Part of the two buccal cusps may be seen from this
Mesial Aspect The mesiobuccal cusp and the mesiolingual cusp
are in view from this aspect, also the well-developed mesial
marginal ridge. Cervical line slanted upwards buccolingually The
buccal and lingual outlines of the root drop straight down and are
approximately parallel for more than half their length, tapering
only slightly at the apical third
The root end is flat and almost square. A developmental
depression usually extends almost the full length of the root on
the mesial side.
Distal Aspect Cervical line does not drop bucally Cervical line
is almost straight Distobuccal cusp and distolingual cusp are not
as long or as sharp as mesial cusps Distal marginal ridges not as
straight and well defined as mesial marginal ridge Distal root is
rounded and shorter and tapers more apically
Occlusal aspect Crowns outlines converges lingually and also
distally Occlusal surface is more nearly rectangular with shorted
sides of the rectange represented by marginal ridges Occlusal
surface has central fossa Mesial triangular fossa is just inside
the mesial marginal ridge , with a mesial pit in this fossa and a
sulcus with its central groove connecting the two fossae
A well defined buccal developmental groove divides mesiobuccal
cusp and distobuccal cusp occlusally Supplemental grooves radiate
from the pit in mesial triangular fossa as follows -one buccally ,
one lingually and one towards the marginal ridge with last
sometimes extending over the marginal ridge mesially
Pulp Cavity Pup cavity contains a chamber and 3 canals
Mesiobuccal and mesiolingual canals are confluent and leave the
chamber in the form of a ribbon The distal pulp canal projects in
ribbon fashion floor of chamber in distal aspects
Pulp chamber had 4 pulpal horns Mesiobuccal horn- largest and
rounded Distobuccal pulp horn-is second , but lacks height of
mesial horns Mesiolingual Horn is third in size and second in
height , while Distolingual pulpal horn is smallest Occlusal view
of pulp chamber is rhomboidal
Mandibular second molar It has characteristics that resembles
those of Permanent mandibular first molar, although its dimensions
differ Buccal Aspect IT has a narrower M-D calibration at the
cervical Portion of the crown than at contact level The mandibular
first permanent molar, accordingly is wider at the cervical
portion
The roots are slender and long Characteristic flare
mesioditally at the middle and apical thirds The point of
Bifurcation of the roots starts immediately below the CEJ
Lingual Aspect Two cusps are almost equal dimensions Seen , a
short , lingual groove is between them The cervical line is
relatively Straight The mesial Portion of the crown seems to be a
little higher then the distal portion , thus appears tipped
distally
Mesial Aspect Outline resembles permanent mandibular First
molar The crest of contour is more prominent bucally Marginal ridge
is high The lingual cusp is longer or higher then Buccal cusp
Cervical line is regular Mesial root is unusually broad and flat
with a blunt and apex sometimes serrated
The cervical line is regular The distal root is almost as broad
as the mesial root and is flattened on distal surface The distal
root tapers more at the apical end than does the mesial root
Distal Aspect Crown is not as wide distally as it is. Mesially,
therefore mesiobuccal and distobuccal cusps from the distal aspect
The distolingual cusp appears well developed and triangular ridge
Is seen over the distal marginal ridge The distal marginal ridge
dips down more sharply and is shorter buccolingually than mesial
marginal ridge
Occlusal Aspect Occlusal outline is some what rectangular Three
buccal cusps are similar in Size Two lingual cusps are also equally
Matched Well defined triangular ridges seen The distal triangular
fossa is not well defined as mesial triangular fossa The mesial
marginal ridge is better developed and more pronounced than the
distal marginal ridge Supplemental grooves are seen on the slopes
of triangular ridges and in the mesial and distal triangular
fossa
Pulp Cavity Pulp cavity is made up of chamber and usually 3
pulp canals Two mesial pulp canals are confluent as they leave
floor of pulp chamber through A common orifice Distal canal is
constricted in the centre
Pulp chamber has 5 pulp horns corresponding to 5 cusps
Mesiobuccal and Mesiolinual Pulp Horns are largest Distobuccal horn
is smaller then mesial horns The distal horn is shorter and
smallest occupying a position distal to distobuccal horn
How it differs from Permanent In the deciduous molar the
M-B,D-B, and the distal cusps are almost equal in size and
development The distal cusp of the permanent molar is smaller than
the other two Because of the small buccal cusps, deciduous tooth
crown is narrower bucolingually,in comparison with its mesiodistal
measurement, than is the permanent tooth
Permanent Incisors The permanent incisors are the first and
second teeth from the midline, which, along with the canines,
comprise the anterior teeth of each quadrant. The incisor closest
to the midline is termed the central incisor, while the second
tooth from the midline is the lateral incisor. This positions the
lateral incisor distal to the central incisor and mesial to the
canine.
In size, the maxillary incisor crowns are generally larger than
those of the mandibular incisors. In the maxillary arch, the
central incisor crown is normally larger than the crown of the
lateral incisor. However, in the mandibular arch, the lateral
incisor crown and root are generally larger than those of the
central incisor, although only very slightly
The incisors as a group participate in all three of the major
functions of the human dentition and have a greater role in
esthetics and phonetics than any other group of teeth. 1.
Mastication - They function by biting, cutting, incising and
shearing, thus breaking the food particles into smaller pieces
suitable for grinding. .
2. Esthetics - Not only do the size, shape, color, and manner
of placement of incisors directly contribute to a person's
appearance, but they provide the support necessary for the normal
profile of the lips and face. 3. Phonetics - They are necessary for
the execution of certain sounds
Labial Aspect The mesial margin is straight and meets the
incisal edge at right angle. The distal margin is shorter and more
rounded. The distoincisal angle is more rounded than the
mesioincisal angle. The labial surface is marked by two
developmental groove and has convexity in cervical third. Maxillary
central incisor is the widest anterior tooth mesiodistally
Lingual Aspect The crown profile is same as that of labial
surface except that there is a broad depression in the central
portion called the lingual fossa and a well developed cingulum. The
lingual fossa is bordered by mesial and distal marginal ridges on
the sides Lingual aspect and the cingulum cervically. The cervical
line on labial and lingual surface is convex apically.
Mesial aspect From the mesial aspect the labial margin is
convex The lingual margin is S shaped, being convex near cingulum
and concave in the middle Mesial curvature of cervical line (3.5mm)
is the most pronounced compared to any other tooth. The cervical
line on the mesial and distal surface is convex incisally
Distal surface is very similar to the mesial surface. This
outline is also convex, but more rounded than on the mesial, as is
the distoincisal angle. The crest of curvature is associated with
the contact area,which is located in the incisal third very near
the junction of the incisal and middle thirds, and so is farther
cervically than it is on the mesial. Although the cervical half of
the mesial and distal outlines is normally convex, either outline
can be nearly straight, in comparison to the almost always convex
incisal half.
Incisal aspect The crown and incisal margin are centered over
root Crown profile is almost bilaterally symmetrical The incisal
margin of newly erupted teeth show three elevations called
mamelons. They correspond to the developmental lobes
Root The root is straight and tapers from the cervical line to
the apex giving it a conical shape The root ends in a blunt apex.
Average Dimensions in millimeters Crown Root Length Length 10.5
13.0 Mesiodistal Diameter at Contact Area 8.5 Mesiodistal Diameter
at Cervical Line 7.0 Labiolingual Diameter at Crest of Curvature
7.0 Labiolingua l Diameter at Cervical Line 6.0 Curvature of
Cervical Line M D 3.5 2.5
Maxillary Lateral Incisor The general shape is similar to
maxillary central incisors except that they are shorter and
narrower. Next to third molars maxillary lateral incisors are the
teeth that show most variation in crown size, shape and form
Labial Aspect The mesioincisal and distoincisal angles are more
rounded than the corresponding angles of the maxillary central
incisor Maxillary Lateral Distoincisal angle more rounded
Mesioincis al angle more rounded Maxillary Central Incisor
Distoincisal angle Mesioincisal angle
On the lingual aspect the marginal ridges and cingulum are more
prominent Prominent marginal ridges Prominent cingulum
CANINES Canines are very long and stable teeth There are four
canines placed at the corner of the mouth and hence called the
corner stones of the dentition They have a single pointed cusp
(also called cuspids) Maxillary canine erupts between 10-12 years
and mandibular canine erupts between 9-10 years of age
Maxillary Canine Labial aspect The crown of maxillary canine is
narrower mesiodistally than that of maxillary central incisor. The
incisal aspect has a large cusp with a pointed cusp tip It has two
slopes (cusp ridges), the mesial slope being shorter than the
distal slope The labial surface is smooth and bulky in the middle
because of the labial ridge
Lingual aspect The crown and root are narrower lingually The
cingulum is well developed, large and sometimes pointed like a cusp
Occasionally a well developed lingual ridge is seen that divides
the lingual fossa into mesial and distal lingual fossae Heavy
marginal ridges are associated with well formed cingulum and
fossae
Mesial aspect From the mesial aspect canine looks similar but
bulkier than maxillary central incisor Maxillary canine is the
widest anterior tooth labiolingually The cervical line curvature is
towards the cusp (incisally) The contact area is near the junction
of the incisal and middle third Mesial aspect
Distal aspect Distal surface is very similar to the mesial
surface The cervical line exhibits less curvature The contact are
is near the middle third
Incisal aspect The labiolingual dimension is greater than the
mesiodistal dimension The cusp tip is labial to the centre of the
crown labiolingually and mesial to the centre mesiodistally The
labial ridge and the cingulum are very noticeable from this
aspect
Root only one The root is the longest and strongest of all the
teeth in the dentition The mesial and distal surfaces of the root
have developmental depressions. Average Dimensions in millimeters
Crown Length Root Length 10.0 17.0 Mesiodistal Diameter at Contact
Area 7.5 Mesiodistal Diameter at Cervical Line 5.5 Labiolingual
Diameter at Crest of Curvature 8.0 Labiolingual Diameter at
Cervical Line 7.0 Curvature of Cervical Line M D 2.5 1.5
Mandibular Canine Labial aspect Mandibular canines are similar
to maxillary canines except that they are slightly narrower
mesiodistally Mesial outline of the crown is straight and inline
with the mesial outline of the root The mesial cusp ridge is
smaller than the distal cusp ridge
Lingual aspect The lingual surface of the crown is smooth and
flat simulating the surface of mandibular lateral incisor Cingulum
is less prominent and marginal ridges are less distinct Mesial and
Distal aspects These aspects are very similar and the cervical line
curves more on the mesial aspect The contact area on mesial aspect
is in the incisal third and a little higher on the distal
third
Incisal aspect Like maxillary canine the labiolingual dimension
is more than the mesiodistal dimension The cusp tip appears
inclined in a lingual direction Root The root is shorter by 1 or 2
mm The developmental depression is more pronounced on the lower
canine
Maxillary Pre- Molars Introduction Premolars are so named
because they are placed between the anterior teeth and the molars
Premolars assist the canines and the molars in tearing and chewing
food Maxillary premolars have two cusps and sometimes one or two
roots Maxillary 1st premolar erupts between 10-11 years and
maxillary 2nd premolar erupts between 10-12 years of age
Maxillary 1st Premolar Maxillary 2nd Premolar
Maxillary 1st Premolar Buccal aspect This tooth has two cusps,
buccal and lingual cusps. The buccal cusp is long with a pointed
tip resembling the cusp of a canine The mesial slope of the buccal
cusp is longer than the distal slope, which is the opposite of
canine The buccal surface is convex, showing strong a strong buccal
ridge The crown exhibits little cervical line curvature
Lingual aspect The crown tapers towards the lingual aspect The
lingual cusp is shorter than the buccal cusp The lingual cusp is
smooth from the cervical portion to the area near the cusp tip The
cusp tip is pointed with mesial and distal slopes meeting at an
angle of about 90 degrees Small portion of the buccal cusp can be
seen from this aspect
Mesial aspect From the mesial and distal aspect both the buccal
and lingual cusps are visible A well developed mesial marginal
ridge and a mesial marginal developmental groove is present In the
middle of the mesial surface is the mesial Mesial aspect
developmental depression which continues beyond the cervical line
The contact area is near the halfway point (JOM ) 3
Distal aspect There is no developmental depression or groove on
this aspect, instead it is convex at almost all points The
curvature of the cervical is less on this aspect The contact area
is near the junction of occlusal and middle third
Occlusal aspect The occlusal aspect is roughly hexagonal in
shape The buccolingual dimension of the crown is much greater than
the mesiodistal dimension The occlusal surface is circumscribed by
the cusp ridges and marginal ridges
1. 2. 3. 4. 5. 6. Within the cusp ridges and marginal ridges
the following are present Central developmental groove Mesiobuccal
and distobuccal developmental groove Mesial marginal developmental
groove Mesial and distal developmental pit Mesial and distal
triangular fossa Buccal and lingual triangular ridge
Root Most Maxillary first premolars have 2 roots, but one and
three roots can also be seen. Two roots; buccal and lingual The
buccal portion of the root resembles canine The root when viewed
from the proximal side shows a big trunk and bifurcation area from
where the buccal and lingual root separate A developmental
depression is seen on the mesial aspect of the trunk.
Average Dimensions in millimeters Crown Length Root Length 8.5
14.0 Mesiodistal Diameter at Contact Area 7.0 Mesiodistal Diameter
at Cervical Line 5.0 Labiolingual Diameter at Crest of Curvature
9.0 Labiolingual Diameter at Cervical Line 8.0 Curvature of
Cervical Line M D 1.0 0
Maxillary 2nd Premolar Buccal aspect The maxillary second
premolar resembles the maxillary first premolar in form and
function The buccal cusp is not as long as that of maxillary 1st
premolar It is less pointed. The mesial slope of the buccal cusp
ridge is shorter than the distal cusp ridge
Lingual aspect The lingual cusp is more or less the same size
as the buccal cusp Mesial and Distal aspects There is greater
distance between the cusps No developmental depression is present
nor any developmental groove crossing the marginal ridge on the
mesial aspect On the distal aspect there is a developmental
depression which is deeper than the depression on the mesial
surface of maxillary 1st premolar
Occlusal aspect The occlusal aspect is more rounded The central
developmental groove is shorter There are multiple supplementary
grooves radiating from the central groove Root Maxillary 2nd
premolar has one root, which is usually as long or a millimeter
longer than the root of maxillary 1st premolar
Maxillary Molars Maxillary molars are the largest teeth in the
maxillary arch. The permanent molars are not succedaneous teeth
because they dont have any predecessors. The deciduous molars are
still in place when the first permanent molars erupt at the age of
6. Maxillary First Molar It has a large crown with four well
developed cusps and occasionally a small fifth cusp. In addition to
the cusps it has three well formed roots; two buccal and one
lingual.
Buccal aspect The crown is roughly trapezoidal Mesiobuccal and
distobuccal cusps are the two buccal cusps Part of mesiolingual and
distolingual cusps are seen from this aspect as the distolingual
line angle is obtuse The buccal developmental groove divides the
two buccal cusps.
Lingual aspect General outline of lingual aspect is reverse of
buccal aspect The mesiolingual, distolingual and fifth cusp are the
only cusps seen from this aspect Mesiolingual cusp is largest of
all the cusps. Distolingual cusp is small and spheroidal
The lingual developmental groove separates the lingual cusps
Sometimes a fifth cusp called the cusp of carebelli may be present.
When present it attached to the Lingual aspect mesiolingual surface
of the mesiolingual cusp.
Mesial aspect Mesiobuccal, mesiolingual and fifth cusps are
visible from this aspect also Mesial marginal ridge is confluent
with the mesiobuccal and mesiolingual cusp ridges and is curved
cervically The cervical line is irregular, Mesial Curving
occlusally aspect The contact area is at the junction of the middle
and occlusal third, closer to the buccal aspect A shallow concavity
is found just below the contact are.
Distal aspect Distobuccal and distolingual cusps are seen The
marginal ridge dips sharply cervically The cervical line is almost
straight Distal aspect
Occlusal aspect The occlusal aspect is roughly rhomboidal in
shape Maxillary first molar crown is wider mesially than distally
and wider lingually than buccally The elevations and depression on
this surface are: 1. Cusps Mesiolingual cusp is the largest
followed by mesiobuccal, distolingual, distobuccal, and the
smallest being the fifth cusp.
2.Ridges Mesial marginal ridge and distal marginal ridge
Oblique ridge 3. Fossae Major fossae: central fossa and distal
fossa Minor fossae: mesial triangular and distal triangular
fossae
4 Grooves Central developmental groove Buccal developmental
groove Lingual developmental groove Transverse groove of the
oblique ridge Distal oblique groove Fifth cusp groove Supplemental
grooves
Pit Central developmental pit Occlusal aspect
Root Maxillary first molar has three roots; two buccal and one
lingual The lingual root is long and slender with bluntly round
apex Mesiobuccal root is broader and curves distally while the
distobuccal root is narrower at the base and a lot straighter
Both the buccal roots are of equal size but smaller than the
lingual root The level of bifurcation area is more closer to the
cervical area on the mesial side than on the distal side. Average
Dimensions in millimeters Crown Lengt h 7.5 Root Length B L 12 13
Mesiodistal Mesiodistal Labiolingual Labiolingual Curvature of
Diameter at Diameter at Diameter at Diameter at Cervical Line D
Contact Area Cervical Line Crest of Curvature Cervical Line M 10.0
8.0 11.0 10.0 1.0 0
Maxillary Second Molar The crown is shorter cervico-occlusally
and about the same width buccolingually when compared with
maxillary first molar The distobuccal cusp is not as well developed
and the distolingual cusp is also small. The fifth cusp is absent
The roots are as long as, if not somewhat longer than those of the
first molar The elevations and depression on the occlusal surface
are similar to that of maxillary first molar.
Maxillary Third Molar Maxillary third molar varies considerably
in size, shape and position It often presents itself as a
developmental anomaly Third molar supplements second molar and is
also similar in its design All third molars show more developmental
variation than any other teeth in the dentition
Mandibular Incisors Introduction Mandibular incisors are four
in number Mandibular central incisor and lateral are similar in
anatomy and complement each other in function They are smaller than
the maxillary incisors Mandibular central incisor erupts between
the age of 6 and 7 Mandibular lateral incisor erupts between the
age of 6 and 8
Mandibular Central Incisor Mandibular Central Incisor is the
smallest tooth in the dentition Labial aspect Labial surface of
mandibular central incisor is very small. It is the narrowest tooth
mesiodistally of all the permanent teeth Narrowest tooth in the
dentition Labial aspect
It is bilaterally symmetrical It is the only incisor where both
mesioincisal and distoincisal angles are sharp and at right angles
Both mesioincisal and distoincisal angles are sharp Labial
aspect
Lingual aspect The lingual aspect is concave from the incisal
edge to the cervical line Cingulum is smooth and barely visible
Shallow lingual fossa and smooth cingulum
The surface is smooth and devoid of any grooves. No other tooth
in the mouth, except the mandibular lateral incisor, shows so few
developmental lines and grooves
Mesial aspect The labial outline is almost straight, except
near cervical third where it is convex The labial surface is
inclined lingually The lingual margin is S shaped The cervical line
on the mesial and distal surface is convex incisally Mesial
aspect
Distal aspect Distal surface is very similar to the mesial
surface. The cervical line is less curved. Distal aspect
Incisal aspect This aspect illustrates the bilateral symmetry
of this tooth. The labiolingual diameter is greater than
mesiodistal diameter. Labiolingually bigger than mesiodistally
Bilaterally symmetrical Newly erupted teeth show mamelons which
wear off upon mastication
Root The root is single and straight. The deflection of the
root if present is on the labial or distal side.
Average Dimensions in millimeters Mesiodistal Crown Root Lengt
Length Diameter at Contact Area h 9.0 12.5 5.0 Mesiodistal Diameter
at Cervical Line Labiolingual Diameter at Crest of Curvature 3.5
6.0 Labiolingual Diameter at Cervical Line 5.3 Curvature of
Cervical Line M D 3.0 2.0 CHRONOLOGY Contact Area Man L.I
Appearance of enamel organ 5 m.i.u First evidence of calcification
3-4 months Crown completion 4-5 years I3 Eruption 6-8 years I3-
Incisal third Root completion 10 years Mesial Distal I3
Mandibular Lateral Incisor Mandibular lateral incisor is
slightly wider mesiodistally The cervical portion of the lingual
aspect is narrower while the incisal portion is wider. This gives
the crown a more or less a fan shaped appearance Fan shaped
appearance Cervical portion narrower
The concavity in the lingual aspect is slightly more when
compared to mandibular central incisor The incisal edge follows the
mandibular arch, giving the crown a slightly twisted appearance on
its root Lingual fossa more concave
Mandibular Pre-molars Mandibular First Premolar Mandibular 1st
premolar has many characteristics of mandibular canine It functions
along with mandibular canine It has two cusps and one root
Mandibular 1st premolar erupts between 10-12 years of age
Buccal aspect From the buccal aspect a large well formed,
pointed buccal cusp is seen The mesial outline is similar to the
distal outline The mesiobuccal cusp ridge is shorter than the
distobuccal cusp ridge (similar to canines) Buccal aspect The
mesial and distal slope of the buccal cusp sometimes show
concavity
Lingual aspect The crown tapers and inclines lingually The
lingual cusp is small, pointed and nonfunctional and in some
specimens it is no longer than the cingulum of maxillary canine
Lingual aspect Between the mesiobuccal and lingual lobe is the
mesiolingual developmental groove
Mesial aspect The lingual inclination of the crown can be seen
from this aspect The lingual cusp is approximately two thirds the
size of the buccal cusp The mesial marginal ridge has extreme
lingual slope Mesial aspect
Mesiolingual developmental groove is present between the mesial
marginal ridge and the mesiolingual cusp ridge The mesial and
distal contact areas are in the middle third, the distal contact
area being more wider.
Distal aspect Distal marginal ridge is higher and does not have
the extreme lingual slope The cervical line curvature is less
curved Distal aspect
Occlusal aspect The crown converges sharply to the centre of
the lingual surface The occlusal surface has two depressions;
mesial and distal fossae Most common form of mandibular 1st
premolar shows a mesiolingual depression and mesiolingual
developmental groove Occlusal aspect
Root The mandibular 1st premolar has one root The root is
approximately (3-4mm)shorter than the root of mandibular canine but
the outline bears a close resemblance to the canine A deep
developmental groove is seen on the mesial aspect on the root On
the distal aspect there is a shallow depression devoid of any
developmental groove.
Average Dimensions in millimeters Crown Length Root Length 8.5
14.0 Mesiodistal Diameter at Contact Area 7.0 Mesiodistal Diameter
at Cervical Line 5.0 Labiolingual Diameter at Crest of Curvature
7.5 Labiolingual Diameter at Cervical Line 6.5 Curvature of
Cervical Line M D 1.0 0
Mandibular Second Premolar Mandibular 2nd premolar resembles
the mandibular 1st premolar from the buccal aspect only The crown
assumes two common types. The first and more common type is the
3-cusp type and the second is the 2-cusp type The two differ mainly
in the occlusal design
Buccal aspect The buccal cusp is shorter with the cusp slopes
presenting less degree of angulations Lingual aspect There may be
one or two lingual cusps mesiolingual and distolingual cusps The
cusp(s) are more developed than the lingual cusp of lower first
premolar A groove separates the two lingual cusps
Mesial and Distal aspects The crown and root are wider
buccolingually Unlike mandibular 1st premolar the marginal ridge is
at right angle to the long axis of the tooth More of occlusal
surface is visible form the distal aspect because the distal
marginal ridge is at lower level than the mesial marginal ridge The
contact areas both mesial and distal are broad and appear higher
because of the short buccal cusp
Occlusal aspect From the occlusal aspect the 3-cusp type
appears square and the 2-cusp type appears rounded. 3-cusp type:-
each cusp is separated by deep developmental grooves forming a Y
shape in the centre ,the occlusal surface also includes a. central
pit b. mesial developmental groove c. mesial triangular fossa d.
distal developmental groove e. distal triangular fossa f. lingual
developmental groove g. supplemental grooves
2-cusp type: - one buccal cusp and one well developed lingual
cusp is present - a central groove travels in a mesiodistal
direction and end in mesial and distal fossa (forming H shape) Root
Mandibular 2nd premolar has a single root which is larger and
longer than the root of mandibular 1st premolar The root is usually
wide with a blunt apex
Mandibular Molars The mandibular molars are larger than any
other mandibular teeth. They are three in number on each side of
the mandible ,the first, second, and third mandibular molars. The
first molar lies posterior to the second premolar, followed by the
second and third molars. They perform the major portion of the work
of the lower jaw in mastication. Each mandibular molar has two
roots, one mesial and one distal. The third and some second molars
may show a fusion of these roots.
Decrease in size, crowns & Roots Roots less divergent More
distal inclination Cusp number
Mandibular First Molar Measurements: Average length 21.5 mm
Crown length (CL) 7.5mm, Root length 14 mm Mesiodistal (MD)
diameter 11mm Buccal Aspect: the mandibular first molar is the
largest tooth in the mandibular arch. It has five well-developed
cusps: two buccal, two lingual, and a distal cusp. It has two
well-developed roots, one mesial and one distal. These roots are
widely separated at the apices.
Buccal Aspect: All five cusps can be seen; the tips of the
lingual cusps can be seen because they are higher than the others.
Two developmental grooves appear on the crown portion; the
mesiobuccal developmental groove and the distobuccal developmental
groove. The mesiobuccal, distobuccal, and distal cusps are
relatively flat. The cervical line is commonly regular in
outline.
Lingual Aspect: Three cusps may be seen: two lingual cusps and
the distal cusp. The lingual cusps are high enough to hide the
buccal cusp. The lingual developmental groove is between the
lingual cusps, extending on the lingual surface.
The mesial outline of the crown is convex. The crest of contour
is higher mesially than distally. The distal outline of the crown
is straight. The cervical line lingually is irregular. The root
bifurcation lingually starts at 4mm below the cervical line.
Mesial Aspect: Two cusps and the mesial root only are to be
seen: the mesiobuccal and mesiolingual cusps and the mesial root.
the entire crown has a lingual tilt in relation to the root axis.
The buccal outline of the crown is convex; this curvature outlines
the buccal cervical ridge. The cervical line may assume a straight
line. The surface of the crown is convex. The mesial root curve
lingually.
Distal Aspect: We see more of the tooth than in the mesial
aspect because there is a distal convergence of the tooth. The
distal cusp is in the foreground of the crown portion. The distal
contact area is placed just below the distal cusp. The distal
marginal ridge is short. The surface is convex. The cervical line
is straight.
Occlusal Aspect: outline is hexagonal. The MD measurement is
greater than BL. The mesiobuccal cusp is larger than either of the
two lingual cusps, which are almost equal to each other in size;
the distobuccal cusp is smaller than any one of the other three
mentioned, and the distal cusp is the smallest. Occlusal
aspect
The land marks to be identified on this surface are: (a)
Central fossa. (b) Mesial and distal triangular fossae. (c) Central
developmental groove. (d) Mesiobuccal and distobuccal developmental
grooves. (e) Lingual Developmental groove. (f) Central pit (g)
Mesial and distal marginal ridges.
Mandibular Second Molar Measurements: Average length 20 mm
Crown length (CL) 7mm, Root length 13mm Mesiodistal (MD)
diameter10.5mm Buccal Aspect: The crown is shorter and narrower
than the first molar. There is one developmental groove, the buccal
developmental groove, between the mesiobuccal and distobuccal
cusps. The roots are inclined distally.
Lingual Aspect: The crown and root converge lingually. The
mesiodistal at the cervix is always greater than that of the first
molar. The contact areas are more noticeable from the lingual
aspect; at a lower level, especially in the distal, than those of
the first molar.
Mesial Aspect: Except for the differences in measurement, there
are little differences from the first molar. The cervical ridge
buccally is less pronounced. Distal Aspect: It is similar to the
first molar except for the absence of the distal cusp and a
distobuccal groove. The contact area is centered on the distal
surface.
Occlusal Aspect: There is considerable difference from the
first molar. The small distal cusp of the first molar is not
present, as well as an absence of the distobuccal developmental
groove. Occlusal aspect of Mandibular Second Molar
Mandibular Third Molar Measurements: Average length 18 mm Crown
length (CL)7mm, Root length11 mm Mesiodistal (MD) diameter10 mm
Buccal Aspect: vary in outline buccal cusps are short and rounded.
shows two roots, mesial and distal, shorter than the roots of the
first and second molars, and their distal inclination is greater.
The roots may be separated or fused.
Lingual Aspect: The third molar, when well developed,
corresponds closely to the form of the second molar except for size
and root development.
Mesial Aspect &Distal Aspect: This tooth resembles the
mandibular second molar except in dimension. Occlusal Aspect:
similar to second mandibular molar; with a more rounded outline and
a smaller buccolingual measurement
Tooth development Initiation of tooth Odontogenesis-Factors
from first arch Ones ability acquired maintained by dental
papillary cells
6 wks In utero Tooth Buds Dental Lamina
Life Cycle of the Tooth Growth Initiation Proliferation
Histodifferentiation Morphodifferentiation Apposition Calcification
Eruption Attrition
Primary Epithelial band/ 6 week th Continuous band of thickened
epithelium Roughly horse shoe shaped Thickening first seen in ant
midline
Contd thickening of DL in 10 areas of upper/ lower arch
Thickenings correspond to position of future primary dentn
Proliferation Multiplication of the cells of the initiation
stage Formation of the tooth germ Cap Stage formation of the Dental
Papilla Stellate reticulum Enamel pulp 9-11 weeks
Histodifferentiation Bell Stage Dental papilla Dental Organ
Dental Sac Dental Lamina 14th week
Morphodifferentiation Advanced bell stage. Inner enamel
epithelium Formation of Dentin Fate of the Dental Lamina 18th
week
Apposition appositional, additive and regular
Calcification Begins at the cusp tips or incisal edges and
proceeds cervically
Lines of Retzius
Neonatal line
Stages in tooth growth Dental lamina and Bud stage Cap stage
Bell stage[ Early] Bell stage {advanced} Formation of enamel and
dentin matrix Initiation Proliferation Hiisto defferentiation
Morpho defferentitiation Apposition
Theories of Eruption Root Formation Theory Proliferation of the
Hertwigs Epithelial Root Sheath Proliferation of the connective
tissue of the papilla Simultaneous growth of the jaw Pressures from
muscular action Apposition and resorption of bone
Exfoliation of the Primary Tooth Pressure on the roots by the
erupting permanent tooth Development of osteoclasts Successive
resorption of tooth root, cementum, dentin and adjacent bone due to
the action of the osteoclasts.
Clinical significance of morphology& histology Variation of
teeth has been an enduring interest to the clinical practitioner
and the laboratory scientist. No two teeth are alike. The
day-to-day variation of teeth that we see is the norm. It is the
odd, peculiar, and strange group of teeth to which we focus our
attention here. They are called anomalies.
These few facts about tooth development will assist us in
understanding tooth variation: (1) Teeth form from the cooperative
interaction of two germ layers--ectoderm and ectomesenchyme (a
neural crest derivative). (2) Enamel is formed from the ectodermal
components. (3) Dentin, pulp, cementum, the supporting PDL, and
bone are all derived from ectomesenchyme.
Disturbances in Size Microdontia means teeth that are smaller
than normal. Generalized microdontia is a rare condition associated
with uncommon conditions such as pituitary dwarfism."Pegshaped"
upper lateral incisors and small third molars are seen regularly by
the practicing dentist. Occasionally, an upper lateral incisor is
missing on one side, peg-shaped on the other side. -Macrodontia
refers to teeth that are larger than normal. Generalized
macrodontia is rare, seen infrequently in conditions such as
pituitary gigantism. It can be localized involving just one or a
few teeth. You may occasionally see the term 'megadontia' used for
this condition. .....
Disturbances in Number. Anodontia is the congenital absense of
all teeth, Anodontia means the failure of teeth to form at all.) In
true (or complete) anodontia, all teeth fail to develop. -True
anodontia is an extremely rare occurrence. When this does occur, it
is usually part of a more generalized disorder ectodermal
dysplasia, an inherited defect of all ectodermally derived
structures. -Partial anodontia is the failure of one or more teeth
to develop. It is much more common than complete anodontia. Third
molars, lower second premolars, and upper lateral incisors (in that
order) are the most common congenitally absent teeth. When a
deciduous tooth is absent, its permanent successor is usually
missing also.)
Supernumerary teeth are 'extra' teeth. Most (90%) occur in the
maxilla. Their presence in the deciduous dentition is quite rare.
Two terms occasionally used to describe are polydontia or
hyperdontia. The most common of all supernumerary teeth is the
mesiodens which is a supernumerary that forms in the midline
between and lingual to the roots of the maxillary central incisors.
Most supernumerary teeth do not erupt; they often are unknown until
detected on X-ray films. Fourth molars, themselves a rare
occurrence are infrequently called 'paramolars' or 'distomolars.'
Supernumerary teeth occur less often than do missing teeth.
Disturbances in Eruption. -Premature eruption of all of the
teeth, either deciduous or permanent, may suggest an underlying
endocrine dysfunction such as h