Development of dentition and occlusion

DEVELOPMENT
OF DENTITION &
OCCLUSION
www.indiandentalacademy.com

OVERVIEW
 Introduction
 Pre-natal development
 Post-natal development
 Factors affecting occlusal
development
-General
-Local
 Clinical implications
 Conclusion

INTRODUCTION
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
implications.

PRE-NATAL DEVELOPMENT
OF TEETH
 Initiation
 Bud stage
 Cap stage
 Bell stage

Initiation:
The very 1st
sign of tooth development appears late in the 3rd
embryonic week.
At 6 weeks, the 4 maxillary odontogenenic zones coalesce to form
the dental lamina.
Morphological changes in the dental lamina occurs in 3 main
phases:
 Initiation of the entire deciduous dentition –during 2nd
month
in utero
 Initiation of the entire permanent dentition –from 5th
month
in utero
 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

Bud Stage:
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
position .
 Between the 7th
& 8th
week both max. &
mand. Deciduous tooth buds form.
 The 1st
buds to form are the mand. Anterior
teeth.

Cap Stage:
 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
bud.
 The epithelium of the cap-shaped tooth organ
enlarges & proliferates into deeper connective tissues
(ectomesenchyme).
 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
-Stratum intermedium
-Stellate cells
-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
formed. www.indiandentalacademy.com

Root Formation:
 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 .

THEORIES OF
TOOTH ERUPTION
 Bone remodeling
 Root growth
 Vascular pressure
 Periodontal ligament traction

 BIRTH TO COMPLETE PRIMARY
DENTITION
 1ST
INTERTRANSITIONAL PERIOD
 1ST
TRANSITIONAL PERIOD
 2ND
INTERTRANSITIONAL PERIOD
 2ND
TRANSITIONAL PERIOD
 ADULT DENTITION
POST-NATAL DEVELOPMENTPOST-NATAL DEVELOPMENT
OF DENTITIONOF DENTITION

BIRTH TO COMPLETE
PRIMARY DENTITION
(Birth- 3yrs)
 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
development.
 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
month.
 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
occlusal plane.

FIRST INTERTRANSITIONAL
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)
 Terminal plane
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

FIRST TRANSITIONAL
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
teeth. www.indiandentalacademy.com

SECOND INTERTRANSITIONAL
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
their resorption.
 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.

SECOND TRANSITIONAL
PERIOD( 10- 12 yrs )
 Here, exchange of teeth occurs between c,d,e &
3,4, 5.
 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”
takes place.
 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

ADULT DENTITION
 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
enhance profile.
 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

FACTORS AFFECTING
OCCLUSAL DEVELOPMENT
 GENERAL FACTORS
1.Skeletal Factors
2.Muscle Factors
3.Dental factors
 LOCAL FACTORS

General Factors
 Skeletal factors :
Conditions that affect jaw growth
are ;
1. Any pathological condition
2. Inherited & acquired congenital
malformation
3. Trauma or infection during the growing
years

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.
 Lip form
 Lip activity
 Tongue size, resting position & function
 Adaptive resting posture or adaptive
swallowing
 Endogenous tongue thrust
 Thumb & finger sucking
 Neutral zone

 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
teeth
Space maintenance

Local Factors :
 Aberrant developmental position of
individual teeth
-Trauma
-Malposed crown
-Dilacerated root
-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 )

 Developmental Hypodontia
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 :
-Hypodontia
-Supernumerary teeth
-Generalized spacing
-Proclination of upper incisors
-Heredity

 Buccal Crossbite :
-Bilateral Crossbite
-Unilateral Crossbite
-The Incisal Overbite

CLINICAL IMPLICATIONS
 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
through time.

Occlusal Adaptive Mechanisms
STAGE DENTITION BONE MUSCULATURE
Developing
dentition
Eruption and
tooth movement
Growth Learning, imprinting
Healthy
adult
dentition
Wear,
extrusion,anterior
component
Repair Supportive occlusal
reflexes
Deteriorating
adult
dentition
Reconstructive
dentistry
Resorption
pathology
Traumatic occlusal
reflexes: protective
occlusal responses
Edentulous
adult
Prosthetic
dentistry
Resorption Loss of sensory input

Development of dentition and occlusion

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Development of dentition and occlusion