Deciduous dentition

Prerequisite knowledgeGrowth & development of face and jaws both

prenatal and postnatal Eruption of teeth timing and sequenceMorphology of teeth both primary and

permanent Terminology of key wordsMasticatory movements and path of closure

of the mandible

Definition of terms used

Deciduous dentitionmixed dentitionPermanent dentitionPredecessorSuccessor

Over biteVertical distance between upper and lower

incisal edges

Over jetHorizontal distance between upper and lower

incisal edges.

Inclination of teethProclined

Vertical

Retroclined

Arch relationship

At birth - gum padsUpper horseshoe - shapedLower U - shapedCovered with thick fibrous muco periosteum.Contain 24 crypts of developing teeth.Separated , tongue lies in between

Eruption of deciduous incisors.During the first year, the gum pads enlarge

and arches widen to provide space for erupting incisors.

Timing of eruption 6 month variation premature eruption of teeth natal and

neonatal teeth.

Deciduous dentition Natal teethNeonatal teeth.

Sequence of eruptionLower central incisorupper central incisor,Lower lateral incisorupper lateral incisor,Lower primary first molar,Upper primary first molarLower and upper primary caninesLower and upper primary second molars.

Typical features of primary dentitionColour - whiter than permanent teethSize incisors and canines are smaller than

permanent teeth

.Typical features of occlusion of primary dentition.Incisors are uprightPrimate space presentpositive over jet and over biteeach maxillary tooth occlude with two

mandibular teeth.Distal surfaces of primary second molars in

same vertical plane.

Age changes from 3 to six years.Spacing begin to appear or existing spaces

increase due to growthocclusal attritionincisor position become edge to edgedistal surfaces of second molar may not

remain in same vertical plane

Development of occlusion

Mixed dentition stage 6-12 years

Beginning of the mixed dentition

Lower first molar erupt around six years.

Space gaining for incisor eruptionTotal size of lower primary incisors -17mmTotal size of lower permanent incisors -23mmUpper primary incisors -23mm.upper permanent incisors -30mm.

Space made available to accommodate incisors1. Spacing already present in th incisor

region

2. increase of inter canine width

3.upper incisors erupt into wider arc

Leeway spaceDifference between total mesio -distal size of

primary canine and both primary molars always larger than total size of permanent canine first premolar and second premolar.

C+D+E> 3+4+5 Leeway space = (C+D+E )- (3+4+5)

Transient malocclusions seen in the mixed dentition

Transient incisor crowding

Transient incisor crowding

Features of normal OCCLUSIONSkeletal bases should be ideal

Correct size and correct relationship

Occlusal featuresAll teeth are present and in correct contact

with their immediate neighbors in the same arch with no spacing or rotations.

There is no tooth size disproportion between maxillary and mandibualr teeth.

The teeth are at correct inclination and angulation in their respective skeletal bases. Teeth of the buccal segment should be slightly mesially and lingually inclined and the teeth o f the labial segment should be slightly mesially inclined and proclined.

Each upper tooth occludes with corresponding tooth in the lower arch and one distal to it, with the exception of the upper third permanent molars.

Upper teeth lie labial or buccal to the lower teeth The lower labial segment teeth therefore, occlude with the palatal surface of the upper labial segment teeth and the buccal cusps of the lower buccal segment teeth occlude in the fossae of the upper buccal segment teeth.

Occlusal plane is slightly curved and can be considered to form a part of a sphere. The curvature in the sagittal plane is known as the Curve of Spee Curvature in the coronal plane is known as Curse of Monson.

The incisor, canine and molar relationship are class 1

In function following observations are made,On protrusion there is incisal guidance where

the incisors remain in contact with the buccal segment teeth out of occlusion.

In lateral excursions there is either canine guidance or group function in the buccal segments and there is no balancing or non working side interferences.

Occlusal featuresNo rotationsNo crowding or spacingCorrect inclinations class I occlusion occlusal plane has a slight curveCurve of spee and Curve of Monson