Developmentofocclusion.ppt

8/14/2019 Developmentofocclusion.ppt

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Developing Dentition

AndIts Disturbances


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Development of Occlusion

Pre-dentate period

Deciduous dentition Mixed dentition

Permanent dentition


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Pre-dentate period

Period from birth to eruption of first deciduous teeth

Alveolar arches of infant called gum pads

The gum pads:

the alveolar processes at birth

pink, firm and covered with fibrous periosteum

Divided into 10 segments by transverse/ lateral grooves

Lateral Sulci: prominent lateral grooves between deciduous canine anddeciduous first molar

Develop in 2 parts: Labial portion (Differentiates first)

Lingual portion (Differentiates later)

These 2 portions separated by dental groove- site of origin of dentallamina


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Maxillary gum pads

Horse shoe shaped

Consists of:

Gingival groove

Dental groove

Lateral sulcus (canine and deciduous molar segments)


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Gingival groove

Dental groove

Lateral sulcus

Lateral grooves

Papilla

Maxillary Gum Pad


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Mandibular gumpads

U shaped with labially everted anterior portion

Also consists of:

Gingival groove

Dental groove

Lateral sulcus


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Mandibular Gum Pad

Lateral sulcus

Molar Segment

Canine Segment

Gingival groove


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Relationship of Gumpads

At rest, gumpads separated by tongue over lower gum pad

Variable overjet with contact only at molar segment

Lateral sulcus of lower is distal to upper

At function:

Mainly vertical

No lateral movement

Very little in antero-posterior plane In early foetal development, mandibular protrusion present

which is gradually reversed

At birth, lower jaw situated posteriorly


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Relationship of Gumpads


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Growth of Gum Pads

At birth, width is inadequate to accommodate all incisors

Growth of gum pads is rapid in first year

More in transverse and in labio-lingual direction Each segment becomes prominent & prepare for eruption

Eruption commences at 6 months of age


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Deciduous or Primary Dentition

General features

Both dental arches are half round/ovoid

No curve of speeShallow cuspal digitation

Slight overjet/overbite

Vertical incisors

Spacing is normal/ No crowding


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The Occlusion of Primary Dentition

1. The incisors are more vertically positioned in the alveolus & are

often spaced.

2. The overbite is usually greater.

3. Significant primate spaces (the spaces distal to the lower canine

and mesial to the upper canine)

4. The distal edges of the upper and lower primary molars may be

flush, mesial or distal step.


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Spacing in Primary Dentition

Spaced dentition: Considered good as the spaces can be

utilized for adjustment of permanent teeth

2 types:

Primate space/Simian/Anthropoid space

Physiologic space/Development space


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Primate Spaces

between upper lateral and caninebetween lower canine and first deciduous molar


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Developmental/ Physiologic spaces

Total space varies from 0-8 mm, average 4mm in maxillary archTotal space varies from 1-7 mm, average 3mm in mandibular arch


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Primary Molar relation

Relationship of the Distal surface of maxillary and mandibular

second primary molars

Flush Terminal Plane relation

Mesial step

Distal step


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Primary Anterior teeth relation

Overbite: Vertical overlap, minimal to about 2 mm

Overjet: Horizontal overlap, range 2-6 mm, average 1-2 mm

at 2yrs 4mm

decreases with age upto 5 yrs

Canine relation: most stableclass I

class II

Arch dimensions

Arch circumference

Arch length

Bicanine diameter

Bimolar diameter

Arch height

Arch width


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The six/four rule

for primary tooth emergence

(4 teeth emerge for each 6 months of age)

1.6 months:4 teeth (lower centrals & upper centrals)

2.12 months:8 teeth ( 1. + upper laterals & lower laterals)

3.18 months:12 teeth (2. + upper first molars & lower first

molars)

4.24 months:16 teeth (3. + upper canines & lower canines)

5.30 months: 20 teeth (4. + lower second molars & upper

second molars)


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Summary for primary teeth development

By 4th week in utero, dental lamina; 6th week tooth germs

By 5 months in utero, all crowns start calcification.

By 1 year (11-12 months), all crowns complete formation.

By 2.5 years, all primary teeth have emerged.

By 4 years , all primary teeth complete root formation.


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Abnormal Behaviour of Primary Teeth

1.Retained primary teeth

2. Submerged primary teeth

3. Remnants of Primary Teeth

4. Natal and Neonatal Teeth


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Retained Primary Teeth


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Submerged Teeth Ankylosed Teeth


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Natal teeth


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Natal Teeth

Natal teeth already present at the time of birth; neonatal

teeth erupt during the first 30 days after birth

Generally develop on the lower arch where the central

incisors will be.

Have little root structure and are attached to the margin

of the gingiva by soft tissue

Because of their placement, they may cause irritation and

trauma to the infant's tongue

May cause pain/irritation to mother while feeding

If the tooth is loose,the child runs a risk of aspiration


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Mixed dentition:

anterior deep bite

lower anterior crowding

ugly duckling stage

end-on relation

Permanent dentition:

overjet and overbite


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Infantile Swallow


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Developmentofocclusion.ppt