development of the teeth and occlusion

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PEDODONTICS

DEVELOPMENT AND MORPHOLOGY

OF THE TEETH AND OCCLUSION

Dr. Amal A. A. KaderPediatric Dentist

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DEVELOPMENT AND MORPHOLOGY OF THE TEETH AND OCCLUSION

-Introduction

-Calcification

-Importance of Primary teeth

-Eruption

-Principal morphological characteristics of primary teeth

-Morphologic differences between primary and permanent teeth

-Normal occlusion in children

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The development

of the human tooth

can be observed

as early as the sixth week

of embryonic life .

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At birthAll primary teeth and 6

6 months1 and 3

1 year2

2 years4

3 years5 and 7

9 years8

Calcification

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Importance of Primary Teeth

1 .Preparation of the food for digestion and assimilation

2 .Maintenance of space for the permanent teeth

3 .Helps to growth and development of the jaws

4 .Helps to the development of speech

5 .Aesthetic function

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Each tooth stars to move towards occlusion at the time of crown completion and beginningof root formation

1. Pre-eruptive phase: in which the tooth root begins its formation and begins to move toward the surface of the oral cavity.

2 .Eruptive phase: is the time of gingival emergence, and about ½ or 2/3 the root is formed.

ERUPTION

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Agemonths

612182430

ToothABDCE

ERUPTION

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At birthAll primary teeth and 6

6 months1 and 3

1 year2

2 years43 years5 and 79 years8

ToothAge (months)

A6B12D18C24E30 -36

Calcification Eruption

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ERUPTION

Upper6124537

Tooth6789101112

Lower6123457

Permanent Dentition

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Principal Morphological Characteristicsof individual primary teeth

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The mesiodistal diameter of the crown of the maxillary central incisor is greater than the cervicoincisal lengt

The maxillary lateral incisor crown is smaller in all dimensions and the length of the crown is greater than the mesiodistal width .

Maxillary Incisors

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The crown of the maxillary canine is more constricted at the cervical region than are the incisors .

The canine root is more than twice the length of the crown.

Canine

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The mesiolingual cusp of the maxillary first molar is the largest and sharpest

The distolingual cusp is poorly defined, small and rounded

First maxillary primary molar

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There is considerable resemblance between the

maxillary primary second molar and the maxillary

first permanent molar. There are two well-defined

buccal cusps, with a developmental groove between them .

The crown of the second molar is considerably larger than that of the first molar.

Second maxillary primary molar

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The mandibular first primary molar doest not resemble any of the permanent teeth.

The mandibular first molar has two buccal cusps;the mesial cusp is the larger of the two.

First mandibular primary molar

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The mandibular second molar resembles the mandibular

first permanent molar

One of difference

between the crowns of the primary

molar and that of the first permanent molar is in the

distobuccal cusp because the distal cusp of the permanent

molar is smaller than the others two buccal cusps .

Second mandibular primary molar

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Number: 20

Color: White

Morphological differences between primary and permanent teeth

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Size:Primary teeth are smallerin all dimensions

The mesiodistal width of primaryincisors and canines is less

The mesiodistal width of primary molars is wider than their premolarssuccesors

The thickness of enamel and dentine in primary teeth is approximately half

Its thickness in permanent teeth

Morphological differences between primary and permanent teeth

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Crowns

Morphological differences between primary and permanent teeth

The crowns of the primary teeth arewider mesiodistally

The buccal and lingual surfaces of primary molars converge sharply towardthe occlusal surface, forming a narrow occlusal table

The cervical ridge of enamel at the cervical third of the anterior crowns is much moreprominent labially and lingually

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Crowns

Morphological differences between primary and permanent teeth

The enamel cap in primary molars ends abruptly at the cement enamel junction

The crowns of primary molars are bulbousdue to their markedly constricted necksand pronounced cervical ridges on the buccal aspect especially in the maxillary and mandibular first molars The enamel cap in primary teeth is thinner

and has nearly a constant depththroughout the crown

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Crowns

Morphological differences between primary and permanent teeth

The enamel rods at the cervix slopeocclusally in primary teeth instead ofbeing oriented gingivally as in permanent teeth

The interproximal contact between primary molars is not a small roundarea as in permanent molars but tendsto be a large ellipsoid and flattened area

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Roots

Morphological differences between primary and permanent teeth

The roots of primary anterior teeth are narrower mesiodistally

The roots of the primary molars are relatively longer and more slender

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Pulp

Morphological differences between primary and permanent teeth

The pulp chambers are large

The pulp horns are higher in primary molars, especially the mesial pulp horn.

The root canals of primary molars show more lateral branchings and apical

ramifications

Apical foraminae in primary teethis relatively wider

The pulp chamber will decrease in size with an increase in age

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Morphological differences between primary and permanent teeth

Incisor spacing

Primate spaces

Overjet: 0

Overbite: Can be edge to edge until a complete crown

Spee curve: There is not

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Occlusion at 3 years

Normal Occlusion in children

Straight or flush terminal plane

Mesial step

Distal step

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Occlusion at 6 years

Normal Occlusion in children

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Occlusion at 8 to 9 yearsNormal Occlusion in children

With the eruption of the upper and lower permanent incisors there is an increase indepth of overbite

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Normal Occlusion in childrenOcclusion at 8 to 9 years

Diastema between upper permanent central incisors,which is normal for this age (ugly duckling stage)

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Diastema between upper permanent central incisors,which is normal for this age (ugly duckling stage)

Normal Occlusion in childrenOcclusion at 8 to 9 years

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Occlusion at 10 to 12 yearsNormal Occlusion in children

With the eruption of premolars, the vertical dimension is increased which corrects the deep overbite

Closure of Leeway spaces

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Occlusion at 10 to 12 yearsNormal Occlusion in children

With the eruption of premolars ,the vertical dimension is increasedwhich corrects the deep overbite

Closure of Leeway spaces

Diastema between upper centralincisors is closed

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