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OF DENTITION &
Factors affecting occlusal
The development of dentition is an important
part of craniofacial growth as the formation,
eruption, exfoliation and exchange of teeth
take place during this period. This is an
assimilation of facts, predictions, studies, in
both static and dynamic situations; the
factors influencing them and their clinical
The very 1st
sign of tooth development appears late in the 3rd
At 6 weeks, the 4 maxillary odontogenenic zones coalesce to form
the dental lamina.
Morphological changes in the dental lamina occurs in 3 main
Initiation of the entire deciduous dentition –during 2nd
Initiation of the entire permanent dentition –from 5th
Initiation of the 1st
permanent molar–4 months in utero
Initiation of the 2nd
permanent molar-1 yr
Initiation of the 3rd
permanent molar-4 to 5 yrs
Immediately after the formation of Dental
lamina, the following take place :
Division for cheek & lip from the Dental
arches at the Vestibular furrow.
Increased mitotic activity( knob-like )
corresponding to each deciduous tooth
Between the 7th
week both max. &
mand. Deciduous tooth buds form.
buds to form are the mand. Anterior
The growth rate throughout the tooth bud is not
uniform & is more active at the periphery.
The Cap stage begins by the 8th
week with the
appearance of a concavity on the deep surface of the
The epithelium of the cap-shaped tooth organ
enlarges & proliferates into deeper connective tissues
Areas of increased cellular density give rise to non-
enamel portions of the tooth & its periodontal matrix.
The Tooth germ, consisting of the Enamel organ,
Dental papilla & Dental follicle can be identified.
Bell Stage :
In the Bell stage, the Enamel organ differentiates into :
-Inner enamel epithelium
-Outer enamel epithelium
Dental papilla cells differentiate into Odontoblasts &
Inner enamel epithelium cells into Ameloblasts. They
deposit Dentin & Enamel respectively, and withdraw
from each other & the DE junction.
The OEE becomes discontinuous & allows entry of cells
from the Dental sac, while the Stellate cells are
withdrawn to make room for the Crown.
When enamel formation is complete, the crown is fully
Just before the ameloblasts deposit their
matrix, the Cervical loop lengthens due to a
proliferation of cells & forms the Hertwigs
epithelial root sheath (determines no., size &
shape of roots ).
Dentin matrix is deposited against the root
sheath & covered by cementum due to the
invasion of cementoblasts, which eventually
form the PDL .
Periodontal ligament traction
BIRTH TO COMPLETE PRIMARY
POST-NATAL DEVELOPMENTPOST-NATAL DEVELOPMENT
OF DENTITIONOF DENTITION
BIRTH TO COMPLETE
The tooth buds of all primary teeth are present and in
various stages of development at the time of birth.
About 7 to 8 months after birth, all the teeth except
the 7’s & 8’s are present in some stage of
In a mandible which is less than 1yr of age, a line
drawn along the occlusal surfaces passes through the
condyle suggesting the lack of ramal growth.
By the 1st year, a normal & desirable dentition will
usually exhibit spacing.www.indiandentalacademy.com
The 1st primary tooth to erupt is the lower central
incisor between 6&8 months of age, followed by the
U.Centrals, U.Laterals & L.Laterals.
The 1st primary molar erupts by about the 14th
The primary cuspids & 2nd primary molars erupt by
about 2 1/2 yrs of age.
The primary teeth are quite upright whereas the
permanent incisors have a labial inclination & the
permanent posteriors have a mesial tilt.
There is evidence of vertical growth as signified by
the superior positioning of the condyle to the
PERIOD( 3-6 yrs )
This is the period between the completion of
eruption of Primary dentition & the emergence
of the Permanent teeth.
According to Baume(1950)
Primate Space(Type I Spacing)
Space for the 6’s is achieved by
Tuberosity apposition in the maxilla.
Ramal resorption in the mandible.
The tooth buds of the 4’s & 5’s begin to form.www.indiandentalacademy.com
PERIOD( 6-8 yrs )
Eruption of the 1st permanent molars :
The Terminal plane is very important in
determining the interocclusal relationship of
the 1st permanent molars.
-Vertical plane type
-Mesial step type
-Distal step type
Exchange of incisors :
The primary incisors begin to exchange with the
permanent incisors before & after the eruption of the 6’s.
The total sum of the M-D width of the 4 permanent
incisors is > that of the primary incisors by about 7mm in
the maxilla & 5mm in the mandible.
Incisor liability(Mayne 1968 )
-Interdental spacing in primary incisors should exist.
-Intercanine archwidth growth should occur.
- Intercanine archlength should increase through anterior
positioning of the permanent incisors.
-Favourable size ratio between the primary & permanent
PERIOD( 8-10 yrs )
This period is referred to as the “Mixed
Dentition period”/ “Ugly Duckling stage”
( Broadbent 1937 ) .
Vertical dimension of the face increases
thus increasing the alveolus to
accommodate the roots.
Max. Tuberosity& Mand. Ramal activity
makes room for the 7’s.
Max. cuspids are lateral to the nose, mand.
cuspids close to the mand. borders.www.indiandentalacademy.com
Premolars are in the bifurcation of
their antecedents with evidence of
The “GABLE EFFECT” :
-The mand. cuspids & bicuspids are
in the shape of a ‘V’, in sequence, in
relation to the occlusal plane.
-The sequence of eruption being
3,4,5 in the mandible, 3 makes its
way much ahead of 4 & 5.
PERIOD( 10- 12 yrs )
Here, exchange of teeth occurs between c,d,e &
Emergence of 7’s takes place by virtue of increase
in arch-circumference, after the Dental arch upto
6, is established .(mixed to permanent )
During the exchange & emergence, smooth
utilization of “Leeway space” & “Primate space”
The sequence of eruption of the lateral teeth in:
Maxilla - 4, 3, 5 ( 3,4,5 /4,5,3 are exceptions ).
Mandible - 3,4, 5. www.indiandentalacademy.com
This is considered to be between 18 & 25 yrs,
when the roots of the permanents are
completed and the 8’s have erupted.
Nose & chin become more prominent to
Cranio-facial growth gives finishing touches to
the face by pneumatization of the Sinuses &
apposition at the Glabella.
Increase in jaw growth continues ( mandible )
to accommodate the 8’s.www.indiandentalacademy.com
Skeletal factors :
Conditions that affect jaw growth
1. Any pathological condition
2. Inherited & acquired congenital
3. Trauma or infection during the growing
The teeth are set in the jaws and hence
jaw relationship will have an influence
on that of the dental arches. Jaw
relationships can be considered as :
1. Jaws in relation to the cranial base
2. Jaws in relation to each other
-Skeletal Cl.I, II & III
-Buccal cross-bite/ lingual occlusion
-High gonial angle-increased V.D
Low gonial angle-decreased V.D
3. Alveolar bone in relation to basal bone
Muscle factors :
Final tooth position is largely governed by muscle
action, particularly muscles of the lips, cheeks &
Tongue size, resting position & function
Adaptive resting posture or adaptive
Endogenous tongue thrust
Thumb & finger sucking
Dental factors :
The third major factor affecting occlusal
development is the relationship between
the size of the dentition & the size of the
jaws. But it is more realistic to consider
dentition size in relation to the dental
arch size, than to jaw size.
Effects of excessive dentition size
-Overlapping & displacement of teeth
-Impaction of teeth
-Space closure after extractions
Effects of early loss of primary teeth
-Function & oral health
-Over-eruption of opposing teeth
-Psychological effects on child & parent
-Position of permanent teeth
Effects of asymmetric loss of primary
Local Factors :
Aberrant developmental position of
-Unknown etiology( perm. Max. canines )
Presence of supernumerary teeth
-Supplemental (teeth of normal form )
-Conical (the mesiodens )
-Tuberculate (usually palatal to the upper
centrals, delaying their eruption )
Hypodontia can modify the occlusion & position
of the teeth by virtue of its effects on :
-The form of the teeth
-The position of the teeth
-The growth of the jaw
The Upper Labial Frenum
This may cause median diastema. Other possible
causes are :
-Proclination of upper incisors
Normal versus Ideal occlusionNormal versus Ideal occlusion
Models of occlusionModels of occlusion
Occlusal Adaptive MechanismsOcclusal Adaptive Mechanisms
Normal vs Ideal occlusion
‘Normal’ implies variations around an
average or mean value
‘Ideal’ connotes a hypothetical
concept or goal
It is perfectly proper and practical to
accept at the end of treatment , an
arrangement of the teeth within the
jaws in positions that are neither ideal
nor normal but may be stable in a
particular person’s face.
Models of occlusion
Occlusion is the common theme of all
branches of dentistry, but the concepts of
occlusion held by practitioners of different
fields are different.
The best occlusion, and hence the best model
of occlusion , is that which adapts best
Occlusal Adaptive Mechanisms
STAGE DENTITION BONE MUSCULATURE
Growth Learning, imprinting
Repair Supportive occlusal
Resorption Loss of sensory input