Nomenclature,Chronology and Morphology

11/08/06 Department of pedodontics and preventive dentistry

NOMENCLATURE,CHRONOLOGy ,MORPHOLOGY,ERUPTI

ON AND SHEDDING OF HUMAN DENTITION


NOMENCLATURE•The first step in understanding dental anatomy is to learn the nomenclature ,or the system of names use to describe or classify the material included in the subject.

•The term mandibular refers to the lower jaw or mandible.

•And the term maxillary is for upper jaw ,maxilla

•Acc. to dictionary definition the term decidous means “not permanent ,transitory” but unabridged dictionary means milk tooth, which is define as one of the temporary teeth of a mammal that are replaced by permanent teeth. Also called baby tooth.

•The term primary indicate first dentition i.e. decidous dentition where as term permanent suggest permanent dentition.


FORMULAE FOR MAMMALIAN TEETHThe number of all mammalian teeth are expressed by fomulae that is used to differentiate the human dentition from others species.

The denomination of each tooth is represented by the initial letter in its name i.e I for incisor,C for canine,P for premolar,M for molar.

Each letter is followed by a horizontal line and the number of each type of tooth is placed above the line for maxilla and below the line for the mandible.

The dental formula for the PRIMARY DENTITION is I2/2 C1/1 M2/2=10

11/08/0611/08/06Department of pedodontics and Department of pedodontics and

preventive dentistrypreventive dentistry

For PERMANENT DENTITION is:- I2/2 C1/1 P2/2 M3/3=16


TOOTH NUMBERING SYSTEMSUNIVERSAL NUMBERING SYSTEM:-Recommended by ADA in 1968.For PRIMARY DENTITION it is as follows:

A B C D E F G H I J

T S R Q P O N M L K

A to J>Maxillary teeth ,beginning with maxillary right second molar. ”For the mandibular teeth letters K to T are used.

For PERMANENT DENTITION it is as follows:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17

1 to 16>Maxillary teeth ,beginning with maxillary right third molar. And for Mandibular teeth numbers 17 to 32 used.


PALMER NOTATION SYSTEM:Palmer published this system in 1870.In this system the arches are divided into quadrants.For PRIMARY DENTITION it is as follows:

E D C B A A B C D E

E D C B A A B C D E

Thus for single tooth such as maxillary right central incisor the designation is A/ and for mandibular right central incisor the notation is |A.

For PERMANENT DENTITION it is as follows:

8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8

8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8

In this the right maxillary first molar is 6


FDI SYSTEM

o Full form is Federation Dentaire Internationale.

oAdopted by WHO for both Primary and Permenent dentition.

oThis is two digit system.

oTooth notation for PRIMARY DENTITION is:

55 54 53 52 51 61 62 63 64 65

85 84 83 82 81 71 72 73 74 75

For eg 53 In this first digit i.e 5 indicates Quadrant and 3 is tooth number so it is maxillary right decidous canine.

oTooth notation for PERMANENT DENTITION is:

18 17 16 15 14 13 12 11 21 22 23 24 25 26 27 28

48 47 46 45 44 43 42 41 31 32 33 34 35 36 37 38

For eg 23 is maxillary left permanent canine.


THE CROWN AND ROOTEach tooth has a Crown and Root.

The crown is with covered Enamel and Root is covered with Cementum.

They both join at CEMENTOENAMELJUNCTION or CERVICAL LINE.

The main bulk of tooth is composed of Dentine.

ROOT

CERVICAL LINE

CROWN


The pulp chamber is in crown and Pulp canal is in the root.

So four tissues of tooth are ENAMEL, CEMENTUM, DENTINE and PULP. The first three are hard tissue and last is soft tissue.

The cross section displays a Pulp Chamber and Pulp canal which normally contains a pulp tissue.


The root portion of the tooth is firmly fixed in the bony process of jaw.

That portion of the jaw serving as support for the tooth is called ALVEOLAR PROCESS. The bone of the tooth socket is called ALVEOLUS.

The crown portion is partially covered by the soft tissue called GINGIVA or GUM TISSUE.



PRIMARYPRIMARY

(Upper)(Upper)i1i1

I2I2

CC

M1M1

m2m2

14(13-16)14(13-16)

16(14-16)16(14-16)

17(15-18)17(15-18)

15(14-17)15(14-17)

19(16-23)19(16-23)

1.51.5

2.52.5

9.09.0

6.06.0

11.011.0

10(8-12)10(8-12)

11(9-13)11(9-13)

19(16-22)19(16-22)

16(13-19)16(13-19)

29(25-33)29(25-33)

1.51.5

2.02.0

3.253.25

2.52.5

3.03.0

PRIMARYPRIMARY

(lower)(lower)i1i1

I2I2

CC

M1M1

m2m2

14(13-16)14(13-16)

1616

1717

15.5(14.5-17)15.5(14.5-17)

18(17-19.5)18(17-19.5)

2.52.5

3.03.0

9.09.0

5.55.5

1010

8(6-10)8(6-10)

13(10-16)13(10-16)

20(17-23)20(17-23)

16(14-18)16(14-18)

27(23-31)27(23-31)

1.51.5

1.51.5

3.253.25

2.252.25

3.03.0

CHRONOLOGYCHRONOLOGY OF PRIMARY DENTITIONDENTITION TOOTH FEOC CROWN COM ERUPTION

Weeks in utero Months Months ROOT COMP



PermanentPermanent

(Upper)(Upper)i1i1

I2I2

CC

P1P1

P2P2

m1m1

M2M2

m3m3

3-43-4

10-1210-12

4-54-5

1.5Y1.5Y

2.5Y2.5Y

At birthAt birth

2.5-3Y2.5-3Y

7-9Y7-9Y

4-54-5

4-54-5

6-76-7

5-65-6

6-76-7

2.5-32.5-3

7-87-8

12-1612-16

7-87-8

8-98-9

11-1211-12

10-1110-11

10-1210-12

6-76-7

12-1312-13

17-2117-21

1010

1111

13-1513-15

12-1312-13

12-1412-14

9-109-10

14-1614-16

18-2518-25

PermanentPermanent

(lower)(lower)i1i1

I2I2

CC

P1P1

P2P2

m1m1

M2M2

m3m3

3-43-4

3-43-4

4-54-5

1.5-2Y1.5-2Y

2.5Y2.5Y

At birthAt birth

2.5-32.5-3

8-10Y8-10Y

4-54-5

4-54-5

6-76-7

5-65-6

6-76-7

2.5-32.5-3

7-87-8

12-1612-16

6-76-7

7-87-8

9-109-10

10-1210-12

11-1211-12

6-76-7

11-1311-13

17-2117-21

99

1010

12-1412-14

12-1312-13

13-1413-14

9-109-10

14-1514-15

18-2518-25

CHRONOLOGY OF PERMANENT DENTITION

DENTITION TOOTH FEOC CROWN COM ERUPTION ROOT Months Years Years

COMPLETE



DEVELOPMENT AND ERUPTION OF TEETH

The term ERUPTION has been used to denote the tooth emerging through the gingiva, but then it became more completely defined to mean continuous tooth movement from the dental bud to occlusal contact.

PRIMARY TEETH Enamel organs do not develop at the same rate.

Some of the primary teeth are undergoing resorption while the roots of others are still forming.

Not all teeth lost at the same time.

Primary dentition is completely formed at 3y of age

Calcification begins in utero from 13-16 weeks.



• The DENTAL DEVELOPMENT CAN BE CONSIDERED TO HAVE TWO COMPONENTS:

• formation of crowns and roots.• The eruption of the teeth.

THE DENTITIONSTHE DENTITIONS Divided into 3 Divided into 3 A.A. PRIMARY DENTITION: PRIMARY DENTITION: till six years.till six years.B.B. TRANSTITIONAL DENTITION PERIOTRANSTITIONAL DENTITION PERIOD:D:

C.C. PERMANENT DENTITION:PERMANENT DENTITION:



SEQUENCE OF ERUPTION

FOR PRIMARY DENTITION

AB D C E (Maxillary)

A B D CE (Mandibular)

FOR PERMANENT DENTITION

Maxillary-6 1 2 4 5 3 7 8

Mandibular-6 1 2 3 4 5 7 8

SEOUENCES OF ERUPTION

FOR PRIMARY DENTITION AB D C E (Maxillary) A B D CE (Mandibular)

FOR PERMANENT DENTITION Maxillary-6 1 2 4 5 3 7 8 Mandibular-6 1 2 3 4 5 7 8



MORPHOLOGIC DIFFERENCE BETWEEN PRIMARY AND PERMANENT TEETH

• The crowns of primary teeth are wider mesiodistally in comparison to permanent.

• The roots of primary anterior teeth are narrow and long compared with crown width and length.

• The cervical ridge of enamel at cervical third of anterior crowns is much more prominent labially in the primary.

• The crown and roots of primary molars are more slender mesiodistally at the cervical third.

• The buccal and lingual surfaces of primary molars are flatter above the cervical curvature.



The primary teeth are usually lighter in color than the permanent.

The enamel is relatively thin and has a constant depth.

The pulp horns are high and pulp chambers are large.

Dentine thickness between pulp chambers and the enamel is limited.

Primary roots are narrow when compared to crown width.

Department of pedodontics and preventive dentistry11/08/06

THE PRIMARY TEETHMAXILLARY CENTRAL INCISOR Labial Aspect

In the crown of the primary central incisor, the mesiodistal diameter is greater than the cervicoincisal length.

The labial surface is very smooth, and the incisal edge is nearly straight. Developmental lines are usually not seen. The root is cone-shaped with even tapered sides.

Lingual Aspect The lingual aspect of the crown shows well-developed and highly-developed

cingulum. The root narrows lingually and presents a ridge for its full length in

comparison with a flatter surface labially. Mesial and Distal Aspects

The mesial and distal aspects of the primary maxillary central incisors are similar.

The measurement of the crown at the cervical third shows the crown from this aspect to be wide in relation to its total length.

The curvature of cervical line, which represents the cementoenamel junction (CEJ), is distinct, curving toward the incisal edge.

The root from this aspect appears more blunt.



MAXILLARY CENTRAL INCISORMAXILLARY CENTRAL INCISOR• Incisal AspectIncisal Aspect

– The incisal edge is centered over the main bulk of the The incisal edge is centered over the main bulk of the crown and is relatively straight.crown and is relatively straight.

– On the incisal edge, the labial surface is much broader and On the incisal edge, the labial surface is much broader and also smoother than the lingual surface.also smoother than the lingual surface.

– The lingual surface tapers toward the cingulum.The lingual surface tapers toward the cingulum.

MAXILLARY LATERAL INCISORMAXILLARY LATERAL INCISOR

– In general, the maxillary lateral is similar to the central In general, the maxillary lateral is similar to the central incisor from all aspects, but its dimensions differ.incisor from all aspects, but its dimensions differ.

– Its crown is smaller in all directions.Its crown is smaller in all directions.

MAXILLARY CANINEMAXILLARY CANINE• Labial AspectLabial Aspect

– The crown is more constricted at the cervix in relation to its The crown is more constricted at the cervix in relation to its mesiodistal width, and the mesial and distal surfaces are mesiodistal width, and the mesial and distal surfaces are more convex.more convex.

• Lingual AspectLingual Aspect– The lingual aspect shows pronounced enamel ridges that The lingual aspect shows pronounced enamel ridges that

merge with each other.merge with each other.– This lingual ridge divides the lingual surface into shallow This lingual ridge divides the lingual surface into shallow

mesiolingual and distolingual fossae.mesiolingual and distolingual fossae.– The root of this tooth tapers lingually.The root of this tooth tapers lingually.



MAXILLARY CANINEMAXILLARY CANINE• Mesial AspectMesial Aspect

– From the mesial aspect, the outline form is similar.From the mesial aspect, the outline form is similar.– The measurement labiolingually at the cervical third is The measurement labiolingually at the cervical third is

much greater.much greater.

• Distal AspectDistal Aspect– The curvature of the cervical line toward the cusp ridge is The curvature of the cervical line toward the cusp ridge is

less than on the mesial surface.less than on the mesial surface.

• Incisal AspectIncisal Aspect– From the incisal aspect, the crown is essentially diamond-From the incisal aspect, the crown is essentially diamond-

shaped.shaped.– The tip of the cusp is distal to the center of the crown, and The tip of the cusp is distal to the center of the crown, and

the mesial cusp slope is longer than the distal cusp slope.the mesial cusp slope is longer than the distal cusp slope.

MANDIBULAR CENTRAL INCISORMANDIBULAR CENTRAL INCISOR• Labial AspectLabial Aspect

– The labial aspect of this crown has a flat face with no The labial aspect of this crown has a flat face with no developmental grooves.developmental grooves.

– The mesial and distal sides of the crown are tapered evenly The mesial and distal sides of the crown are tapered evenly from the contact areas, the measurement being less at the from the contact areas, the measurement being less at the cervix.cervix.

– The root of the primary central incisor is long and evenly The root of the primary central incisor is long and evenly tapered down to the apex, which is pointed.tapered down to the apex, which is pointed.



MANDIBULAR CENTRAL INCISORMANDIBULAR CENTRAL INCISOR• Lingual AspectLingual Aspect

– The marginal ridges and the cingulum may be located easily.The marginal ridges and the cingulum may be located easily.– The lingual surface of the crown at the middle third and the The lingual surface of the crown at the middle third and the

incisal third may have a flattened surface level with the incisal third may have a flattened surface level with the marginal ridges, or it may present a slight concavity, called the marginal ridges, or it may present a slight concavity, called the lingual fossa.lingual fossa.

– The root of the primary central incisor is long and evenly The root of the primary central incisor is long and evenly tapered down to the apex, which is pointed.tapered down to the apex, which is pointed.

• Mesial AspectMesial Aspect– The incisal ridge is centered over the center of the root and The incisal ridge is centered over the center of the root and

between the crest of curvature of the crown.between the crest of curvature of the crown.– The convexity of the cervical contours labially and lingually at The convexity of the cervical contours labially and lingually at

the cervical third is pronounced.the cervical third is pronounced.– The mesial surface of the root is nearly flat and evenly tapered.The mesial surface of the root is nearly flat and evenly tapered.

• Distal AspectDistal Aspect– The outline of this tooth from the distal aspect is the reverse of The outline of this tooth from the distal aspect is the reverse of

that found from the mesial aspect.that found from the mesial aspect.

• Incisal AspectIncisal Aspect– The incisal ridge is straight and bisects the crown labiolingually.The incisal ridge is straight and bisects the crown labiolingually.– The labial surface from this view presents a flat surface slightly The labial surface from this view presents a flat surface slightly

convex, whereas the lingual surface presents a flattened convex, whereas the lingual surface presents a flattened surface slightly concave.surface slightly concave.



MANDIBULAR LATERAL INCISORMANDIBULAR LATERAL INCISOR

– The lateral incisor is somewhat larger in all measurements The lateral incisor is somewhat larger in all measurements except labiolingually, where the two teeth are practically except labiolingually, where the two teeth are practically identical.identical.

– The cingulum of the lateral incisor may be a little more The cingulum of the lateral incisor may be a little more generous than that of the central incisor.generous than that of the central incisor.

– The lingual surface of the crown between the marginal The lingual surface of the crown between the marginal ridges may be more concave.ridges may be more concave.

MANDIBULAR CANINEMANDIBULAR CANINE

– The crown is slightly shorter, and the root may be as much The crown is slightly shorter, and the root may be as much as 2 mm shorter than the maxillary canine.as 2 mm shorter than the maxillary canine.

– The mandibular canine is not as large labiolingually as its The mandibular canine is not as large labiolingually as its maxillary opponent.maxillary opponent.

MAXILLARY FIRST MOLARMAXILLARY FIRST MOLAR

– The greatest dimension of the crown of the maxillary first The greatest dimension of the crown of the maxillary first molar is at the mesiodistal contact areas, and from these molar is at the mesiodistal contact areas, and from these areas the crown converges toward the cervical region.areas the crown converges toward the cervical region.

– The mesiolingual cusp is the largest and sharpest.The mesiolingual cusp is the largest and sharpest.– The distolingual cusp is poorly defined, small, and rounded.The distolingual cusp is poorly defined, small, and rounded.– The buccal surface is smooth, with little evidence of The buccal surface is smooth, with little evidence of

developmental grooves.developmental grooves.– The three roots are long, slender, and widely spread.The three roots are long, slender, and widely spread.



MAXILLARY SECOND MOLARMAXILLARY SECOND MOLAR

• There are two well-defined buccal cusps, with a There are two well-defined buccal cusps, with a developmental groove between them.developmental groove between them.– The bifurcation between the buccal roots is close to the The bifurcation between the buccal roots is close to the

cervical region. The roots are longer.cervical region. The roots are longer.– The lingual surface has three cusps: a mesiolingual cusp that The lingual surface has three cusps: a mesiolingual cusp that

is large and well developed, a distolingual cusp, and a third is large and well developed, a distolingual cusp, and a third and smaller supplemental cusp (cusp of Carabelli).and smaller supplemental cusp (cusp of Carabelli).

– A well-defined groove separates the mesiolingual cusp from A well-defined groove separates the mesiolingual cusp from the distolingual cusp.the distolingual cusp.

MANDIBULAR FIRST MOLARMANDIBULAR FIRST MOLAR

– The mesial outline of the tooth, when viewed from the buccal The mesial outline of the tooth, when viewed from the buccal aspect, is almost straight from the contact area to the aspect, is almost straight from the contact area to the cervical region.cervical region.

– The mesiolingual cusp is long and sharp at the tip; a The mesiolingual cusp is long and sharp at the tip; a developmental groove separates this cusp from the developmental groove separates this cusp from the distolingual cusp.distolingual cusp.

– The mesial marginal ridge is well developed.The mesial marginal ridge is well developed.– When the tooth is viewed from the mesial aspect, there is an When the tooth is viewed from the mesial aspect, there is an

extreme curvature buccally at the cervical third.extreme curvature buccally at the cervical third.– The crown length is greater in the mesiobuccal area than in The crown length is greater in the mesiobuccal area than in

the mesiolingual.the mesiolingual.– The longer slender roots spread considerably at the apical The longer slender roots spread considerably at the apical

third.third.

Department of pedodontics and preventive dentistry11/08/06

MANDIBULAR SECOND MOLAR

The mandibular second molar resembles the mandibular first permanent molar.

The buccal surface is divided into three cusps that are separated by a mesiobuccal and distobuccal developmental groove.

The primary second molar, when viewed from the occlusal surface, appears rectangular with a slight distal convergence of the crown.

The mesial marginal ridge is developed to a greater extent than the distal marginal ridge.



THE PERMANENT TEETHTHE PERMANENT TEETH

Maxillary Central IncisorMaxillary Central Incisor

• FacialFacial: It is the most prominent : It is the most prominent tooth in the mouth. It has a nearly tooth in the mouth. It has a nearly straight incisal edge and a gracefully straight incisal edge and a gracefully curved cervical line. The mesial curved cervical line. The mesial presents a straight outline; the distal presents a straight outline; the distal aspect is more rounded. Mamelons aspect is more rounded. Mamelons are present on freshly erupted, are present on freshly erupted, unworn central incisors. unworn central incisors.

Lingual:Lingual: The lingual aspect presents a The lingual aspect presents a distinctive lingual fossa that is distinctive lingual fossa that is bordered by mesial and distal marginal bordered by mesial and distal marginal ridges, the incisal edge, and the ridges, the incisal edge, and the prominent cingulum at the gingival. prominent cingulum at the gingival.



• ProximalProximal: Mesial and distal : Mesial and distal aspects present a distinctive aspects present a distinctive triangular outline. This is true for triangular outline. This is true for all of the incisors. The incisal all of the incisors. The incisal ridge of the crown is aligned on ridge of the crown is aligned on the long axis of the tooth along the long axis of the tooth along with the apex of the tooth. with the apex of the tooth.

• IncisalIncisal: The crown is roughly : The crown is roughly triangular in outline; the incisal triangular in outline; the incisal edge is nearly a straight line, edge is nearly a straight line, though slightly crescent shaped. though slightly crescent shaped.



Maxillary Lateral Incisor Facial: The maxillary lateral

incisor resembles the centralincisor, but is narrower

mesio-distally. The mesial outline resembles the

adjacent central incisor; the distal outline--and particularly the distal incisal angle is more rounded than the mesial incisal angle (which resembles that of the adjacent central incisor.

The distal incisal angle resembling the mesial of the

adjacent canine. Lingual: On the lingual surface, the marginal ridges are usually prominent and terminate into a prominent cingulum. There is

often a deep pit where the marginal ridges converge

gingivally. A developmental groove often extends across the distal of the cingulum onto the root continuing for part or all of

its length



Proximal: In proximal view, the maxillary lateral

incisor resembles the central except that the

root appears longer--about 1 1/2 times longer than

the crown. A line through the long axis of the tooth

bisects the crown. Incisal: In incisal view, this tooth can resemble either the central or the canine to varying degrees. The

tooth is narrower mesiodistally than the upper central incisor;

however, it is nearly as thick labiolingually.



Mandibular Central

Incisor Facial: The mandibular

central incisor is the smallest tooth in the

dental arch. It is a long, narrow, symmetrical

tooth. The incisal edge is straight. Mesial and distal outlines descend apically from the sharp mesial and distal incisal

angles. Lingual: The lingual

surface has no definite marginal ridges. The

surface is concave and the cingulum is minimal

in size



Proximal: Both mesial and distal surfaces present a triangular

outline. Incisal: The incisal

edge is at right angles to a line passing

labiolingually through the tooth reflecting its bilateral symmetry.



Mandibular Lateral Incisor

Facial: This tooth resembles the central

incisor, but is somewhat larger in most

proportions. It is a more rounded tooth; this is

especially evident in the distal incisal angle in unworn specimens.

There is a lack of the bilateral symmetry seen

in the central. Lingual: Except for the lack of symmetry, this

tooth resemble the central.



Proximal: Like the central, the crown

presents a triangular outline. When viewed

critically, the rotation of the incisal edge can be

seen. Incisal: The incisal edge

'twisted' from the 90 degree angle with a line

passing labiolingually through the tooth.



Maxillary Permanent Canine

Facial: The canine is approximately 1 mm narrower than the central incisor. Its mesial

aspect resembles the adjacent lateral incisor; the distal aspect anticipates the first premolar proximal to it. The canine is slightly darker and more yellow in the color than the incisor teeth.

The labial surface is smooth, with a well developed middle lobe extending the full

length of the crown cervically from the cusp tip. The distal cusp ridge is longer than the

mesial cusp Distinct ridge. Lingual : mesial and distal marginal ridges, a well-devloped cingulum, and the cusp ridges

form the boundries of the lingual surface. The prominent lingual ridge extends from the cusp tip to the cingulum, dividing the lingual surface

into mesial and distal fossae.



Proximal: The mesial and distal aspects

present a triangular outline. They resemble

the incisors, but are more robust--especially in the cingulum region. Incisal: The asymmetry of this tooth is readily

apparent from this aspect. It usually

thicker labiolingually than it is mesiodistally. The tip of the cusp is displaced labially and mesial to the central

long axis of this tooth.



Mandibular Permanent Canine

Facial: The mandibular canine is noticeably narrower mesidistally than the upper, but the root may be as long as that of the upper

canine. In an individual person,the lower canine is often shorter than that of the upper

canine. The mandibular canine is wider mesiodistally than either

lower incisor. A distinctive feature is the nearly straight

outline of the mesial aspect of the crown and root. When the

tooth is unworn, the mesial cusp ridge appears as a sort of

'shoulder' on the tooth. The mesial cusp ridge is much

shorter than the distal cusp ridge.

Lingual: The marginal ridges and cingulum are less prominent than

those of the maxillary canine. The lingual surface is smooth

and regular. The lingual ridge, if present, is usually rather subtle

in its expression.



Proximal: The mesial and distal aspects present a triangular outline. The

cingulum as noted is less well developed. When the crown

and root are viewed from the proximal, this tooth uniquely

presents a crescent-like profile similar to a cashew nut.

Incisal: The mesiodistal dimension is clearly less than the labiolingual dimension.

The mesial and distal 'halves' of the tooth are more identical

than the upper canine from this perspective. You will

recall that the cusp tip of the maxillary canine is facial to a line through the long axis. In the mandibular canine, the

unworn incisal edge is on the line through the long axis of

this tooth.



Maxillary First Premolar

Facial: The buccal surface is quite rounded and this

tooth resembles the maxillary canine. The buccal cusp is long; from that cusp

tip, the prominent buccal ridge descends to the

cervical line of the tooth. Lingual: The lingual cusp is smaller and the tip of that cusp is shifted toward the mesial. The lingual surface is rounded in all aspects



Proximal: The mesial aspect of this tooth has a distinctive concavity in

the cervical third that extends onto the root. It is called variously

the mesial developmental depression, mesial concavity, or the 'canine fossa'--a misleading

description since it is on the premolar. The distal aspect of the maxillary first permanent molar

also has a developmental depression. The mesial marginal

developmental groove is a distinctive feature of this tooth.

Occlusal: There are two well-defined cusps buccal and lingual. The larger cusp is the buccal; its

cusp tip is located midway mesiodistally. The lingual cusp tip is shifted mesially. The occlusal

outline presents a hexagonal appearance. On the mesial

marginal ridge is a distinctive feature, the mesial marginal

developmental groove.



Maxillary Second Premolar

Facial: This tooth closely resembles the maxillary first premolar but is a less defined copy of its companion to the

mesial. The buccal cusp is shorter, less pointed, and more

rounded than the first. Lingual: Again, this tooth

resembles the first. The lingual cusp, however, is more nearly as large as the buccal cusp. Proximal: Mesial and distal surfaces are rounded. The

mesial developmental depression and mesial marginal

ridge are not present on the second premolar.

Occlusal: The crown outline is rounded, ovoid, and is less

clearly defined than is the first.


Mandibular First Premolar



Mandibular Second Premolar

11/08/0611/08/06 Department of pedodontics and preventive Department of pedodontics and preventive dentistrydentistry

Maxillary First Permanent Molar

Facial: The mesiobuccal and distobuccal cusps dominate the

facial outline. They are separated by the buccal developmental groove.

All three roots are visible. The buccal roots present a 'plier handle' appearance with the large lingual

root centered between them. Lingual: Two cusps of unequal size dominate the occlusal profile. The cusps are separated by the lingual

developmental groove which is continuous with the distolingual (or distal oblique) groove. The larger

mesiolingual cusp often displays the Carabelli trait. It is a variable

feature. It appears most often as a cusp of variable size, but is

occasionally expressed merely as a

pit.


Proximal: In mesial perspective the mesiolingual cusp, mesial marginal

ridge, and mesiobuccal cusp comprise the occlusal outline. When present,

the Carabelli trait is seen in this view. In its distal aspect, the two distal

cusps are clearly seen; however, the distal marginal ridge is somewhat

shorter than the mesial one. A small concavity on the distal surface that

continues onto the distobuccal root is occasionally described.

Occlusal: The tooth outline is somewhat rhomboidal with four distinct cusps. The cusp order

according to size is: mesiolingual, mesiobuccal, distobuccal, and distolingual. The tips of the

mesiolingual, mesiobuccal, and distobuccal cusps form the trigon,

reflecting the evolutionary origins of the maxillary molar. The distolingual cusp is called the talon (heel) and is a

more recent acquisition in evolutionary history. A frequent feature of maxillary molars is the

Carabelli trait located on the mesiolingual cusp.


Maxillary Second Permanent Molar Facial: The crown is shorter occluso-

cervically and narrower mesiodistally whe compared to the first molar. The

distobuccal cusp is visibly smaller than the mesiobuccal cusp. The two buccal roots are more nearly parallel. The roots are

more parallel; the apex of the mesial root is on line with the with the buccal

developmental groove. Mesial and distal roots tend to be about the same length. Lingual: The distolingual cusp is smaller than the mesiolingual cusp. The Carabelli

trait is absent. Proximal: The crown is shorter than the first molar and the palatal root has less

diverence. The roots tend to remain within the crown profile.

Occlusal: The distolingual cusp is smaller on the second than on the first molar.

When it is much reduced in size, the crown outline is described as 'heart-shaped.' The Carabelli trait is usually absent. The order

of cusp size, largest to smallest, is the same as the first but is more exaggerated:

mesiolingual, mesiobuccal, distobuccal, and distolingual.


Mandibular First Permanent Molar Facial: The lower first permanent molar has the widest mesiodistal diameter of all of

the molar teeth. Three cusps cusps separated by developmental grooves make on the

occlusal outline seen in this view. Moving from mesial to distal, these features form the occlusal outline as follows: mesiobuccal

cusp, mesiobuccal developmental groove, distobuccal cusp, distobuccal developmental groove, and the distal cusp. The mesiobuccal cusp is usually the widest of the cusps. The mesiobuccal cusp is generally considered the largest of the five cusps. The distal cusp is smaller than any of the buccal cusps and it contributes little to the buccal surface.

The two roots of this tooth are clearly seen. The distal root is usually less curved

than the mesial root. Lingual: Three cusps make up the occlusal profile in this view: the mesiolingual, the distolingual, and the distal cusp which is somewhat lower in profile. The mesiobuccal cusp is usually the widest and highest of the three. A short lingual developmental groove separates the two lingual cusps


Proximal: The distinctive height of curvature seen in the cervical third of the buccal surface is called the cervical ridge. The mesial surface may be flat or concave in its cervical third . It is highly convex in

its middle and occlusal thirds. The occlusal profile is marked by the mesiobuccal cusp,

mesiolingual cusp, and the mesial marginal ridge that connects them. The

mesial root is the broadest buccolingually of any of the lower molar roots. The distal

surface of the crown is narrower buccolingually than the mesial surface.

Three cusps are seen from the distal aspect: the distobuccal cusp, the distal

cusp, and the distolingual cusp. Occlusal: This tooth presents a pentagonal

'home plate' occlusal outline that is distinctive for this tooth. There are five cusps. Of them, the mesiobuccal cusp is

the largest, the distal cusp is the smallest. The two buccal grooves and the single

lingual groove form the "Y5" patern distinctive for this tooth. The five cusp and

"Y5" pattern is important in dental anthropology.


Mandibular Second Molar Facial: When compared to the first molar, the second molar crown is

shorter both mesiodistally and from the cervix to the occlusal surface. The two well-developed buccal cusps form the occlusal outline. There is no distal

cusp as on the first molar. A buccal developmental groove appears

between the buccal cusps and passes midway down the buccal surface

toward the cervix. Lingual: The crown is shorter than that of the first molar. The occlusal

outline is formed by the mesiolingual and distolingal cusps.

Proximal: The mesial profile resembles that of the first molar. The

distal profile is formed by the distobuccal cusp, distal marginal ridge, and the distolingual cusp. Unlike the first molar, there is no

distal fifth cusp. Occlusal: There are four well

developed cusps with developmental grooves that meet at a right angle to

form the distinctive "+4" pattern characteristic of this tooth.


TOOTH ERUPTIONThe word eruption properly refers to the cutting of the tooth through the gum,it is generally understood to mean the axial or occlusal movement of the tooth from its developmental position within in the jaw to its functional position in the occlusal plane.


However eruption is only part of the total pattern of physiologic tooth movement.

Physiologic tooth movement is descried as consisting of the following.

1.PREERUPTIVE TOOTH MOVEMENT –When deciduous tooth germs first differentiate ,they are very small and good deal of space is between them.This space is soon used because of the rapid growth of the tooth germs and crowding result,especially in the incisor and canine region.

Permanent teeth with deciduous also move before they reach the position from which they will erupt.


The permanent molars,which have no

deciduous predecessors also exhibit movement.

For eg.The upper permanent molars,which develop in the tuberosity

of the maxilla /,at first have their occlusal

surfaces distally and swing around only when the maxilla has grown

sufficiently to provide the necessary SPACE.



2.ERUPTIVE TOOTH MOVEMENT- During this phase ,the tooth moves from its position

within the bone of the jaw to its functional position in occlusion ,and the principal

direction of movement is OCCLUSAL OR AXIAL.3.POST ERUPTIVE TOOTH MOVEMENT-

movement that maintains 1)The position of the erupted tooth while the jaw

continues to grow .2)Compensate for occlusal and proximal wear.’It involves both the tooth &its socket & ceases

when jaw growth is completed .


HISTOLOGY OF TOOTH MOVEMENT

1.Preruptive Phase- Whether it involves drifting or growth of the tooth germ,demands remodeling of the bony wall of the crypt.This is achieved by the selective deposition and rfmoval of bone by osteoblastic and osteoclastic activity.


2. Eruptive phase- In this significant developmental events occur that are associated with eruptive tooth movement.They include the formation of roots,the periodontal ligament,and

the dentogingival junction.Bone removal is necessary for permanent teeth

to erupt.In the case of those teeth with deciduous predecessors there is an additional anatomic

feature,the Gubernacular canal and its content,the Gubernacular cord,which may have

an influence on tooth movement.After removal of any overlying bone there is loss of the intervening soft connective tissue between

the reduced enamel epithelium covering the crown of the tooth and the overlying oral

epithelium.


7 Gubernacular canal and its contents in histologic section. The canal is filled with connective tissue that connects the dental follicle to the oral epithelium. Strands of epithelial cells (arrowheads), remnants of the dental lamina, are often present.


Erupting molar. Both the reduced dental epithelium, overlying the enamel space in this demineralized section, and the oral epithelium have begun to proliferate into the intervening connective tissue as it breaks down.

Erupting molar. Fusion of the reduced dental epithelium and the oral epithelium has occurred to form the beginning of an epithelial-lined canal.


3.Post eruptive phase- The principal movement is in an axial direction.

Movements are also made to compensate for occlusal and proximal wear of the tooth.It is

generally assumed that the continous deposition of cement around the apices of the roots of the teeth is sufficient to compensate

the occlusal wear.Wear also takes place at the contact points

between teeth and to maintain tooth contact mesial or proximal drift takes place.

Histologically,this drift is seen as a selective deposition and resorption of bone on the socket

walls by osteoblast and osteoclasts respectively.

11/08/06Department of pedodontics and

preventive dentistry

MECHANISM OF TOOTH MOVEMENT

Bone Remodelling – It is important to permit tooth movement. Whether the bony remodeling that occurs around teeth causes or is the effect of tooth movement is not known, others studies on bone remodeling have indicated that control

may reside with the bone living cell, the osteoblast

Root Formation – It is the obvious cause of euptive tooth movement. Root formation follows

crown formation and involves cellular proliferation. It is the former that actually that occurs, but if occlusal movements is prevented, resorption of bone occurs at the base of socket. The bone at that base of the socket cannel act

as a fixed base because pressure on bone results in its resorption.

11/08/06Department of pedodontics and

preventive dentistry

Vascular Pressure – It is known that teeth move in synchrony with the arterial pulse, so local volume changes can procedure limited both

movement.

Periodontal Ligament Traction – There is a good deal of evidence that the eruptive force resides

in the dental follicle periodontal ligament complex.

Tissue culture experiment have shown that ligament fibroblast are able to contract a collagen gel, which in turn brings about movement of a disk of root tissue

attached to that gel.


SHEDDING OF DECIDUOUS TEETHThe human dentition,like those of most mammals consists of two generations.The first generation is k/a deciduous & the other is Permanent(secondary)dentition.The physiologic process resulting in the elimination of the deciduous dentition is called shedding or exfoliation.


Pattern of SheddingIt is the progressive reserption of the roots of

the teeth & their supporting tissue,the periodontal ligament.

In general, the pressure generated by the growing & erupting permanent tooth dictates the pattern of

deciduous tooth resorption because of the developmental position of the permanent incisor and canine tooth germs and their subsequent physiologic

movement in an occlusal and resorption of the roots of the deciduous incisors and canines begins on their lingual surfaces. Later these tooth germs occupy a

position directly apical to the deciduous teeth, which permits them to erupt in the position formly occupied by

deciduous molars after first begins on their inner surface because the early developing bicuspids are

found between them. The areas of early resorption are repaired by the

deposition of a cementum – like tissue.


Roots of a primary molar completely resorbed. Dentin is in contact with the premolar enamel.

Exfoliated deciduous molar. The roots have been lost completely, and the enamel has eroded.


Histology of SheddingThe cell responsible for the removal of dental hard tissues are identical to osteoclasts are highly specialised cells responsible for the

removal of bone, and are called odontoclast their cytoplasm is vacuolated and the surface of the

cell adjacent to the resorbing hard tissue forms a “ruffled” border. Peripheral to the ruffled border

is a clear zone.The clear zone represent the attachment apparatus

of the odontoclast.Odontoclast are able to resorb all the dental hard

tissues including enamels.When dentine is being resorbed , the presence of

the tubules provides a pathway for the easy extension of odontoclast process.


Light microscopic appearance of the odontoclast. The odontoclast exactly resembles the osteoclast. Its large size, multinucleate appearance, and ruffled border are visible.

Fine structure of the odontoclast. This cell is resorbing dentin, and sends extensions (arrows) into the dentinal tubules. The ruffled or brush border can be seen, as can the multinucleated character of the cell.


Single rooted teeth are usually shed before root resorption is complete, therefore odontoclast are not found within the pulp chambers of these teeth.

In molars the roots are usually completely resorbed and the crown is also partially resorbed, before exfoliation when this happens the odontoclasts layer is replaced by odontoblasts which resorb both primary & secondary dentin.

The process of tooth resorption is not continuous since there are periods of rest & repairs.

Odontoclast are most commanly found on surfaces of the roots in relation to the advancing permanent tooth they have also been described root canals and pulp chambers of resorbing teeth lying against the predentin surface.

11/08/06 Department of pedodontics and preventive dentistryUltrastructure of odontoclasts and their

precursors.

Cement like tissue (arrowheads) deposited on resorbed coronal dentin.


The forces of mastication applied to the deciduous tooth are also capable of initiating the resorption. As an individual grows, the muscles of mastication increase in

size and exert forces on the deciduous tooth greater than its periodontal ligament can withstand. This leads to the trauma to the ligament and the initiation of resorption.

Photomicrograph showing the abrupt loss of periodontal ligament in a shedding tooth.

Electron micrograph of a periodontal ligament fibroblast in an area preceding the root resorption front. Its cytoplasm is filled with collagen (arrowheads) suggesting an interference with the protein synthetic and/or degradative cell physiology.


As resorption of the roots initiated by pressure of the underlying tooth occurs, there is progressive loss of surface area for attachment of PDL fibres bundles. This weakening of tooth support occurs because it has to withstand increasingly greater occlusal forces generated by the growing muscles of mastication.

Histology of root resorption. Tooth resorption is occurring at the apex of the root, and as a consequence changes are seen in the periodontal ligament (PDL) as this structure becomes less able to cope with the forces applied to it. The downward and oblique orientation of the ligament fibers is progressively lost (below arrowhead), and local pockets of cementum resorption occur (arrows).


REFERENCE:-

WHEELER’S Dental Anatomy ,Physiology & Occlusion By:-Major M. Ash,Stanley J. NelsonDentistry for the child &Adolescent By:-Ralph E. Mcdonald,David R. AveryDental Anatomy By:-Bhalaji

Text Book Of Oral Histology & Embryology By:- Orbans

Text Book Of Oral Histology By:- A. R TENKATE.

Text Book Of Oral Histology By:- Dr.SATISH CHANDRA.


Documents

Nomenclature,Chronology and Morphology