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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) [email protected] Pokharel(501)BDS 2011
1
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
2
DEVELOPMENT OF MIXED DENTITION
Mixed dentition period consists of both
deciduous & permanent teeth in the oral
cavity.
Extends from 6- 12 years of age
3
MIXED DENTITION CONSISTS OF 3 PHASES:
1. First transitional period
2. Inter-transitional period
3. Second transitional period
5
1. FIRST TRANSITIONAL PERIOD
A. Emergence of first permanent molars
B.Exchange of deciduous incisors with permanent incisors
C. Establishment of occlusion
6
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.
7
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
12
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”
13
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
14
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
15
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
SEX DENTAL ARCH WIDTH INCREASE BETWEEN 2-18 YEARS
MALES MAXILLA 6 mm
MANDIBLE 4 mm
FEMALES MAXILLA 4.5 mm
MANDIBLE 4 mm
22
Self correcting when canines erupt - pressure is transferred from the roots to the coronal areas of the incisors
28
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
29
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
30
• 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
31
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
33
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
34
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