Clinical features of mixed dentition period

Resource faculties Dr Bandana Koirala(Professor and HOD)

Dr Mamata Dali (Assistant Professor)

Dr Sneha Shrestha(Assistant Professor)

Department of pedodontics BPKIHS,Dharan

PresenterSantosh pandit (502) bless288maniac@gmail.comSandhya Pokharel(501)BDS 2011

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DEFINITION

The period during which both primary and permanent teeth are in oral cavity together , is known as mixed dentition period.

6 E D C 2 1 1 2 C D E 6 6 E D C 2 1 1 2 C D E 6

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DEVELOPMENT OF MIXED DENTITION

Mixed dentition period consists of both

deciduous & permanent teeth in the oral

cavity.

Extends from 6- 12 years of age

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MIXED DENTITION CONSISTS OF 3 PHASES:

1. First transitional period

2. Inter-transitional period

3. Second transitional period

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1. FIRST TRANSITIONAL PERIOD

A. Emergence of first permanent molars

B.Exchange of deciduous incisors with permanent incisors

C. Establishment of occlusion

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A.EMERGENCE OF FIRST PERMANENT MOLARS

•Mandibular first molar is the firstpermanent tooth to erupt at around 6 years of age

•Anteroposterior positioning of thepermanent molars is influenced by terminal plane relation-ship of deciduous2nd molars which is of 3 types.

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The erupting 1st permanent molars may also be in a flush or end-on relation

The shift in permanent lower molar from flush terminal plane to class 1 relation can occur in 2 ways:

1. EARLY SHIFT

2. LATE SHIFT11

1. EARLY SHIFT

If flush terminal plane in second deciduous molars – primate spaces seen

Eruptive force of permanent molars – closing of primate spaces

Since this occurs in the early mixed dentition period, it is called EARLY SHIFT

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2. LATE SHIFT

•When no spaces exist – first permanent molar not able to close space

•So when primary molar exfoliate – permanent molar migrates mesially to use up “LEEWAY SPACE”

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2. LATE SHIFT

When the deciduous 2nd molars exfoliate the permanent 1st molars drift mesially utilizing the LEEWAY SPACE OF NANCE.

This occurs in the late mixed dentition period & is called LATE SHIFT

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LEEWAY SPACE OF NANCE

The combined mesiodistal widths of deciduous canine, 1st & 2nd molars is more than that of the combined mesiodistal widths of permanent canine, 1st & 2nd premolars.

The difference between the two is called LEEWAY SPACE

MAXILLA : 0.9mm/ segment= 1.8mm total MANDIBLE : 1.7mm/ segment= 3.4mm total

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B. EXCHANGE OF INCISORS

• Deciduous incisors are replaced by permanent incisors• Mandibular central incisors are usually 1st to erupt

INCISOR LIABILITY : Difference between the amount of space needed for accommodation of incisors and the amount of space available is called incisor liability.

MAXILLARY ARCH: 7mm MANDIBULAR ARCH: 5mm 18

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•MAXILLARY ARCH – 4 mm

•MANDIBULAR ARCH – 3 mm

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SEX DENTAL ARCH WIDTH INCREASE BETWEEN 2-18 YEARS

MALES MAXILLA 6 mm

MANDIBLE 4 mm

FEMALES MAXILLA 4.5 mm

MANDIBLE 4 mm

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Ugly-duckling-stage-badri.mp4

Self correcting when canines erupt - pressure is transferred from the roots to the coronal areas of the incisors

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INTER- TRANSITIONAL PERIOD

Lasts for around 1.5 years

Relatively stable phase with no changes occuring in the dentition

Teeth present are permanent incisors & 1st

molars along with deciduous canines & molars

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SECOND TRANSITIONAL PERIOD

• 9-10 YEARS OF AGE – STARTS WITH SHEDDING OF POSTERIOR TEETH

•EMERGENCE OF CUSPID , BICUSPID AND SECOND PERMANENT MOLARS

•CORRECTION OF UGLY DUCKLING STAGE

•CHILD LOSES ROUNDNESS OF BODY

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• MOST COMMON SEQUENCE OF ERUPTION 4-3-5 IN MAXILLA 3-4-5 IN MANDIBLE

• DENTAL ARCH LENGTH IS REDUCED JUST PRIOR TO ERUPTION OF SECOND MOLAR BY MESIAL FORCE

• UTILIZATION OF LEEWAY SPACE

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Other self correcting anomalies

•Anterior deep bite

•Mandible anterior crowding

•End on relation

TRANSITION TO PERMANENT DENTITION

Permanent dentition forms within the jaws soon after birth except for cusps of 1st permanent molars which formbefore birth

Permanent incisors develop lingual or palatal to deciduous incisors The premolars develop below the diverging roots of deciduous molars

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Calcification begins at birth with the calcification of cusps of 1st permanent molars & extends as late as the 25th yr of life

Complete calcification of incisor crowns takes place by 4-5 yrs & of other permanent teeth by 6-8 yrs except for the 3rd molars

At approximately 13 yrs of age all permanent teeth except 3rd molars are fully erupted

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ERUPTION SEQUENCE OF PERMANENT DENTITION

MAXILLARY ARCH:

6 – 1 - 2 – 4 – 5 – 3 – 7 – 8

OR

6 – 1 – 2 - 4 – 3 – 5 – 7 – 8

MANDIBULAR ARCH:

6 – 1 – 2 – 3 – 4 – 5 – 7 - 835

REFERENCES

• DENTISTRY FOR THE CHILD AND ADOLESCENT, NINTH EDITION by Ralph E. McDonald,David R. Avery,Jeffrey A. Dean

• TEXTBOOK OF PEDODONTICS by Shova Tandon

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