MORPHOLOGY OF DECIDUOUS MORPHOLOGY OF DECIDUOUS TEETHTEETH

Dr jameel kifayatullah KCD

Functions of primary teeth needed for efficient chewing of food provide support for lips and cheeks

maintaining a normal facial appearance and smile

formulation of clear speech critical for maintaining space for

permanent teeth to erupt

Important times for tooth eruption

1. NO TEETH (EDENTULOUS)• From birth to 6 months old (approximately):There are no teeth visible within the mouth. 2. PRIMARY DENTITION ONLY• 6 months to 2 years old (approximately): All

primary teeth are erupting into the child’s mouth over this period.• 2 to 6 years old (approximately): All 20 primaryteeth are present; no permanent teeth are yet visiblein the mouth.

Important times for eruption

3. MIXED DENTITION• 6 years old (approximately): Permanent teeth start to appear, beginning with the first molars (also called 6-year molars) just distal to the primary second molars. followed closely by the loss of the primary mandibular central

incisors, which are quickly replaced by the permanent mandibular central incisors.

• 6 to 9 years old: All eight permanent incisors replace primary incisors that are exfoliated (shed).

Important times for eruption 9 to 12 years old: All four permanent

canines and eight premolars replace primary canines and molars.

• 12 years old: Second molars (also called 12-year molars) emerge distal to the permanent first molars.

Important times for eruption4. ADULT DENTITION ONLY • After 12 years (second) Molars erupt,

28 permanent teeth are present, and all primary teeth have been exfoliated and replaced.

• 17 to 21 years old: Third molars (if present)

emerge.

Deciduous versus permanent dentition

Smaller in sizeShorter crown height relative to total crown

root lengthGreater crown width mesiodistally relative to

inciso(occluso) gingival height Relatively longer roots than their

crowns compared to permanent teeth

Deciduous versus permanent dentition

CERVICAL RIDGES on labial and lingual surface of anterior teeth

Buccal cervical ridges on deciduous molars Constricted cervix(squeezed in) Occlusal aspect: constricted occlusal table

Deciduous versus permanent dentition Longer and thinner roots when compared to permanent teeth Flaring or spreading in deciduous molar roots.

Pulp chamber deciduous v/s permanent teeth

Larger pulp chamber compared to permanent teeth

Deciduous Dentition The layers of enamel and dentin of primary

teeth are thinner than on secondary teeth, so the pulp cavities are proportionally larger and therefore closer to the surface

Primary teeth are less mineralized so become very worn

Primate spaces: Interproximal spaces between primary teeth i.e b/w max lateral incisor and canine and b/w mandibular canine and first molar--- proper alignment of permanent

Dental formula

Deciduous teeth

1. Prominent cervical ridges on facial surfaces run mesiodistally

2. The prominent lingual cingula seem to bulge and occupy about one third of the cervicoincisal length

3. No depressions, mamelons, or perikymata on the labial surface of the crowns of the primary incisors

TRAITS OF ALL PRIMARY ANTERIORTOOTH CROWN

ROOT TRAITS OF ANTERIOR TEETH

The roots of primary anterior teeth are long in proportion to crown length and are relatively narrow mesiodistally

The roots of primary anterior teeth bend labially in their apical one third to one half by as much as 10 degree.

Deciduous incisors

EruptionMandibular before maxillary incisorsCentral before lateral incisors

No mamelons, labial grooves or lobes

Maxillary Central incisor

UNS------------------E, F FDI--------------------- 51, 61 PALMER-------------- A A Eruption time------- 7.5months(FULLER) Order----------------- 1 Shedding----------- 6-7 years

Maxillary Central incisor

Increased mesiodistal width of crown (unique trait)

Rounded mesioincisal and distoincisal angle than permanent successor.

No mamelons on incisal surface+ flat incisal surface

No labial grooves, depressions or lobes

Pronounced bulge on labial surface.

Maxillary Central incisor Prominent

cingulum. Prominent

marginal ridges Deeper lingual

fossa. No lingual pit

Maxillary Central incisor

MESIAL ASPECT: wider labiolingually

Cervical line exhibits less curvature incisally.

DISTAL ASPECT: Cervical line curvature

less on distal surface as compared to mesial surface.

Maxillary Central incisor Incisal Aspect Straight incisal

edge Divides the crown

into equal labial and lingual portions.

Greater mesiodistal width.

Maxillary Central incisor Single root Tapers evenly to

the apex Root longer

relative to crown length.

Maxillary Lateral Incisor UNS--------------------D ,G FDI--------------------- 52, 62 PALMER--------- B B Eruption time------- 9

months(FULLER) Order----------------- 2 Shedding------------ 7 -8 yrs

Maxillary Lateral incisor

Much smaller than central (trapezoidal labially, triangular proximal aspect)

Crown is wider incisocervically than mesiodistally.

Distoincisal angle more rounded than mesioincisal angle

Marginal ridges on lingual surface more prominent

Lingual fossa is deep

Maxillary lateral incisor Incisal aspect Much narrowerMesiodistal dimension more rhomboidal &

more convex.

Maxillary Lateral IncisorROOT Lateral incisor root

relatively longer Apex not so

rounded.

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Mandibular teeth

Mandibular central incisor UNS-------------------- P, O FDI--------------------- 81, 71 Eruption time------- 6

months(FULLER) Order----------------- 1 Shedding------------ 6-7 yrs

Mandibular central incisor

Chisel shape incisor morphology Sharp mesioincisal and distoincisal

angles to the cervial line(90 DEGREES)

Incisal margin straight,no mamelons.

Smooth labial surface lacking developmental depressions.

Flatter than labial surface of permanent incisors.

Labially symmetrical crown Bulge on labial surface at CEJ.

Mandibular central incisor Well developed

lingual cingulum Less defined

marginal ridges than those of maxillary deciduous central incisor.

Shallow lingual fossa

Mandibular central incisor

Proximal aspect; Triangular in shape/ wedge shaped

when seen from mesial or distal aspect.

Incisal edge located over root centre. Cervical line contour evenly curved

towards incisal. Greater labiolingual width than that

of permanent incisors. Distal aspect shows less depth of

curvature towards incisal.

Mandibular central incisor Straight incisal edge Divides the labial and

lingual portions of the crown into nearly equal halves.

In deciduous maxillary central incisor the crown is wider MD.

M & D portions of crown symmetrical

Mandibular central incisor Single ,long ,slend

er Convex labial and

lingual surfaces. Flattened mesial

and distal surfaces.

Mandibular Lateral Incisor UNS--------------------Q , N FDI--------------------- 82, 72 Eruption time------- 7 MONTHS Order----------------- 2 Shedding------------ 7-8 years

Mandibular lateral incisor Similar in form to

deciduous central incisor.

Distoincisal angle is rounded, mesioincisal angle is sharp.

Labial/lingual aspect: Incisal outline slopes

slightly towards the distal

Mandibular Lateral Incisor Lingual Aspect Cingulum and

marginal ridges little larger.

Lingual fossa little deeper.

Mandibular Lateral Incisor Incisal aspect:

crown not symmetrical.

Cingulum bulges towards distal.

Mandibular lateral incisor Single root Longer root than

central incisor Distal curvature

apically. Distal longitudinal

groove.

Maxillary deciduous canine

Maxillary canine UNS--------------------C (rt) , H(lt) FDI--------------------- 53, 63 Eruption time------- 19 MONTHS Order----------------- 4 Shedding------------ 10-12 years

Maxillary canine

MD width > crown height(Incisocervical measurement)

Labial or lingual views: diamond in shape

Rounder mesial and distal outlines.

M & D outlines overhang the cervical line.

M& D contact areas located at the same level incisocervically.

Mesial cusp slope longer than distal cusp slope.

No labial ridge or depressions No imbrication lines.

Maxillary canine Well developed

cingulum. Prominent marginal

ridges. ML and DL fossae are

present Tubercle often present

on the cingulum extending from the cusp tip to cingulum.

Maxillary canine Mesial aspect Triangular in shape Labial margin convex

incisocervically Lingual margin

concave in incisal half and convex in cervical half

Labiolingually tooth is thicker

Cervical line depth less

Maxillary canine Distal Aspect Similar to mesial

except that cervical line shows less curvature.

Incisal aspect Rhomboidal outline Exhibits more

rounding incisal than the permanent canine.

Cusp tip offset to distal.

Mesial cusp ridge therefore longer.

Maxillary canine ROOT Single root Root approx twice

the length of crown

Wider labiolingually than mesiodistally.

MANDIBULAR CANINE

Mandibular canine UNS-------------------- R ,M FDI--------------------- 83, 73 Eruption time------- 16 MONTHS Order----------------- 4 Shedding------------ 9-12 years

Mandibular canine Smaller and slimmer overall than the

maxillary deciduous canine. MD width of mandibular primary

canine< MD width of maxillary pri canine.

Incisocervical ht> MD Width.

Mandibular canine Distoincisal slope

longer than mesioincisal slope(reverse of max.dec canine)

Mandibular canine LL diameter < that

of deciduous max. canine( much narrower tooth labiolingually)

Less pronounced cingulum, MR & cervical ridges.

Shallower fossae than max canine.

Mandibular canine Single but shorter root.

TRAITS OF ALL PRIMARY POSTERIORTOOTH CROWNS The prominent mesial cervical ridge or

bulge on the buccal surface narrow occlusal table:Due to the taper

of the crown from the cervical bulges toward the occlusal surface

molar crowns are wide mesiodistally relative to their height cervico-occlusally

Traits tooth crowns molar The primary molar occlusal anatomy is

shallow; the cusps are short (not pointed sharp,

almost flat), occlusal ridges not pronounced, and fossae and sulci are correspondingly not as deep as on secondary molars.

Traits tooth crowns molar

There are few grooves or depressions in the crowns.

6. In the primary dentition, primary second molars are decidedly larger than primary first molars. This is different in the permanent dentition where firstmolars are larger than seconds

ROOT TRAITS OF PRIMARYPOSTERIOR TEETH

1. The root furcations are near the crown, with little or no root trunk

2.thin and slender roots This root divergence makes room for the developing

succedaneous premolars. 3. The roots of primary molars are similar to those

of permanent molars in relative size (before resorption)and number.

Primary maxillary molars have three roots: the palatal (longest), mesiobuccal, and distobuccal (shortest). Primary mandibular molars

have two roots: the mesial (largest) and distal.

Maxillary deciduous molars

Maxillary 1st molar UNS----------------- B(Right) , I (LEFT) FDI--------------------- 54, 64 Eruption time------- 14 MONTHS Order----------------- 3 Shedding------------ 9-11 years

Maxillary 1st molar Most atypical of all primary or permanent molars Crown doesnot resemble any other primary or

permanent molar crown. Exhibit some similarities to the crowns of permanent

premolars

Maxillary 1st molar BUCCAL ASPECT MD diameter greater

than crown height Mesial and distal

outlines are convex ,constricted towards cervix.

Comparatively straight occlusal outlinetwo buccal cusps not sharp or prominent.

Maxillary 1st molar Essential difference from

permanent tooth Depth of curvature is much

greater towards the mesial than distal.

Buccal surface smooth and lacks grooves or depressions.

MOLAR TUBERCLE OF ZUCKERKANDL; pronounced bulge on mesial surface of buccal surface.

Flat surface occlusally

Maxillary 1st molar LINGUAL ASPECT Lingual surface

shorter mesiodistally than buccal surface.

ML cusp quite bulky and dominates the occlusal outline

DL cusp is so diminitive that DB CUSP is also partially visible from this aspect.

Maxillary 1st molar LINGUAL ASPECT Cervical line is

evenly and slightly curved towards cervix.

Convex & smooth surface ,lacking grooves or depressions.

Maxillary 1st molar MESIAL ASPECT Disparity b/w the

buccolingual widths at its cervical and occlusal margins much more than in max.first permanent molars.

Wider dimension cervically due to prominent cervical ridge on buccal and greater taper of buccal and lingual outlines towards occlusal.

Maxillary 1st molar Mesial Aspect Buccal outline dominated by

cervical ridge and crest of curvature is in cervical third.Remainder of buccal outline straight.

Lingual outline convex.More cervically located crest of curvature than in permanent molars

Occlusal outline MB+ ML cusps and mesial marginal ridge make up the occlusal outline.

ML cusp more generous in height than MB cusp.

Maxillary 1st molarMESIAL ASPECT Cervical line

slightly curved towards occlusal.

Maxillary 1st molar Distal Aspect Considerably smaller than the mesial

surface. Tapering of buccal surface towards the

distal therefore much of the buccal surface visible

from distal aspect. DB cusp more prominent than minute DL

cusp. Distal marginal ridge less pronounced than

mesial marginal ridge. Cervical line is straight to slightly curved

occlusally.

Maxillary 1st molar

OCCLUSAL ASPECT UNUSUAL FIVE SIDED FIGURE Cusps: 4 cusps 1) MB cusp 2) DB cusp 3) ML cusp 4) DL cusp

Maxillary 1st molarMesiolingual cusp Largest cusp and

longest.Mesiobuccal cusp MB cusp greater

than distobuccal.Distobuccal cuspDistolingual cusp Smallest cusp.

Maxillary 1st molar Transverse ridge:

prominent T-ridge Formed by lingual

cusp ridge of MB cusp and buccal cusp ridge of ML cusp.

Oblique RidgeExtends from ML

cusp to DB cusp.

Maxillary 1st molar Fossae: 3 fossae1) CENTRAL FOSSA2)MESIAL

TRIANGULAR FOSSA

3) DISTAL TRIANGULAR FOSSA

Maxillary 1st molar ROOTS no root trunk. Root trunk: defined as that

portion of root situated b/w cervical line and the point of furcation.

Three roots: 1) MB root 2) DB ROOT 3) Palatal Slender and flared roots Largest +longest palatal root.

Maxillary 2nd molar UNS-------------------- A,J FDI--------------------- 55, 65 Eruption time------- 24 MONTHS Order----------------- 5 Shedding------------ 10-12 years

Maxillary 2nd molar Primary maxillary

second molar larger than primary maxillary first molar

Closely resembles the permanent maxillary first molar in form but is smaller in all dimensions.

Usually has a Cusp of Carabelli ,as its permanent counterpart.

Mandibular 1st molar UNS-------------------- L &S FDI--------------------- 84, 74 Eruption time------- 12 MONTHS Order----------------- 3 Shedding------------ 9-11 years

Mandibular 1st molar crown unlike any tooth of

either dentition.(unique crown shape)

Prominent buccal cervical ridge on mesial half of buccal surface.

The HOC on the buccal is at cervical one third

The HOC on the lingual is in the middle one third.

Mandibular first molar Crown wider

mesiodistally than buccolingually

Mandibular primary first molar Buccal aspect:

mesial outline straight occlusogingivally

Distal outline more convex & overhangs the cervical line

Two buccal cusps in occlusal outline MB AND DB CUSP.MB CUSP LARGER.

BUCCAL ASPECT CUSP OUTLINES

MORE PROMINENT THAN PRIMARY MAX FIRST MOLAR

DEPRESSION SEPARATING TWO BUCCAL CUSPS

BUCCAL ASPECT CERVICAL LINE

DEEPER OFFSET TOWARS MESIAL

PROMINENT CERVICAL RIDGE ON MESIAL PORTION

LINGUAL ASPECT LINGUAL SURFACE

SHORTER OCCLUSOCERVICALLY THAN BUCCAL

SMOOTHER AND CONVEX

LACKS ANY DEPRESSION AND RIDGES

LINGUAL ASPECT STRAIGHTER

CERVICAL LINE TWO LINGUAL

CUSPS ON OCCLUSAL OUTLINE

ML CUSP LARGER AND SHARPER

PORTIONS OF TWO BUCCAL CUSPS SEEN

MESIAL ASPECT CERVICAL RIDGE

representing crest of curvature in cervical third of buccal outline

BOTH MB &ML cusps visible CONTACT AREA: at the junction of occlusal & middle

third CERVICAL LINE: Located

farther cervically on buccal and extends to more occlusal at lingual

Distal aspect All the four cusps

seen MB Cusp the

longest

Mandibular 1st molar CUSPS: 4 cusps:1)MB

2) ML 3) DB 4) DL

The two mesial cusps are considerably larger than distal cusps.

OCCLUSAL ASPECT occlusal outline is

somewhat oval or rectangular

wider mesiodistally than faciolingually occlusal table is

wider mesiodistally than faciolingually

OCCLUSAL ASPECT 4 CUSPS MB LARGEST

FOLLOWED BY ML,DB,DL (smallest)

The two mesial cusps larger than distal cusps

Mandibular 1st molar A transverse ridge

passes b/w the mesiobuccal and mesiolingual cusps.

OCCLUSAL TABLE Fossae : 3 Central ,mesial and

distal triangular fossae

Two pits: central and mesial pit

Distal pit absent Central pit :deepest

pit and is the central grooves distal termination

Occlusal table GROOVES Central:connects mesial

and central pits Buccal: originates in

central pit extend buccaly to fade out on occlusal surface b/w two buccal cusps

Lingual:separated the two lingual cusps and fade out on occlusal surface

Mandibular 1st molar Roots 2 roots i.e mesial and

distal . Mesial wider than

distal root. FLAT apex of root

mesial root Shorter distal root

having rounded apex

HOW TO TELL RIGHT FROM LEFT PRIMARY TEETH Crown longer on mesial

than distal (facial) Occlusal table has

small mesial triangular fossa; large distal fossa

Mesial cervical crown bulge

Distal marginal ridge more cervical than mesial

HOW TO TELL RIGHT FROM LEFT PRIMARY TEETH Mesial root (if intact)

longer and wider (faciolingually

Mandibular 2nd molar UNS-------------------- K&T FDI--------------------- 85, 75 Eruption time------- 20 MONTHS Order----------------- 5 Shedding------------ 10-12 years

Mandibular 2nd molar

Larger than the primary mandibular first molar.

closely resembles the permanent mandibular first molar, disregarding size and general differences.

5 cusps similar to permanent mand first molar.

Mandibular 2nd molar Major differences are: The 3

buccal cusps (MB,DB& distal) are nearly equal in size.

Occlusal table relatively narrower buccolingually and less pentagonal than that of the first permanent molar.

The mesial root is longer and wider than the distal root whereas they are of equal length in permanent first molar.

ANY QUESTIONS???