Development of dentition & occlusion /certified fixed orthodontic courses by Indian dental academy

DEVELOPMENT OF
DENTITION AND
OCCLUSION

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INDIAN DENTAL ACADEMY
Leader in continuing dental education


DEVELOPMENT OF DENTITION
INTRODUCTION
 Embryonic cavity is lined by
oral ectoderm
 6th week of intra uterine
life(IUL) →local proliferation of
oral ectoderm →formation of
dental lamina
 Deciduous teeth →direct
proliferation of dental lamina
 Permanent teeth →lingual
extension of dental lamina
 Permanent molars →distal
proliferation of dental lamina

DEVELOPMENT OF TEETH
Bud

stage
Cap stage
Bell stage
Root formation


Bud stage


Cap stage


Bell stage


PERIODS OF OCCLUSAL DEVELOPMENT

1.
2.
3.
4.

Pre-dental period
Deciduous dentition period
Mixed dentition
Permanent dentition period


PRE-DENTAL PERIOD
 Period

after birth during which neonate does not
have teeth
 Lasts 6 months after birth


Gum pads



1.
2.




Alveolar processes at the time of birth
Firm,pink,horse shoe shaped,covered by
fibrous periosteum
Develops in two parts
Labiobuccal portion
Lingual portion
Both portions separated by dental
groove
Gum pads are divided into 10 segments
by transverse grooves
Each segment has one developing
deciduous tooth sac

 lateral

sulcus:
transverse groove
between canine and first deciduous molar
segment.
 Useful in judging inter arch relationship at a
very early stage.
 Lateral sulcus of mandibular arch is more distal
to that of maxillary arch



birth
At birth, no teeth are
visible. Primary teeth are
at least partially formed
and development of
permanent teeth has
begun.


Infantile open bite






Upper and lower gum pads are similar to each other
Upper gum pad is longer and wider
When both are approximated, there is a complete
overjet all around
Contact occurs between upper and lower gum pads in
first molar region and space exists in anterior region
This infantile open bite is considered normal and helps
in suckling


STATUS OF DENTITION
 Neonate

is without teeth for 6 months of life.
 Gum pads insufficient to accommodate
developing incisors that are crowded in crypts
 1st yr of life →gum pads grow rapidly permitting
incisors to erupt in good alignment.


NATAL TEETH




Teeth erupted at the
time of birth →natal teeth
Teeth erupted during 1st
month of life →neonatal
teeth




Natal and neonatal teeth
mostly in mandibular
incisor region and show
familial tendencies


DECIDUOUS DENTITION PERIOD
 1st

6 weeks of IUL →initiation of tooth buds
 Primary teeth erupt at about 6 months
 Eruption completed by 2 ½-3 ½ yrs
 Sequence of eruption →A-B-D-C-E




6 months
At six months, the four
central incisors are
visible, usually appearing
two at a time and
appearing in the lower
jaw first




7-8 months
At seven or eight
months, the four lateral
incisors appear next to
the central incisors. The
primary teeth are bluish
white.




12 months
At around twelve
months, the primary first
molars appear, leaving
temporary spaces
between them and the
lateral incisors




16 months
At sixteen months, the
primary canines erupt
between the lateral
incisors and first molars.




2 years
At two years, the second
primary molars begin to
appear, completing the
primary teeth. By age
three, they appear
completely


SPACING IN DECIDUOUS DENTITION
 Spaces

usually exist between deciduous teeth
→physiological or developmental spaces
 Important for normal development of
2°dentition
 Absence of spaces is an indication that
crowding of teeth may occur in 2°dentition


Primate spaces







Also called as simian
or anthropoid spaces
Seen mesial to
maxillary canines and
distal to mandibular
canines
Helps in placement of
canine cusps of
opposing arch


Deep bite





May occur in initial developing stages
Accentuated by the fact that deciduous incisors are
more upright
Lower incisal edges often contact cingulum area of
maxillary incisors
Later reduced by
1. Eruption of deciduous molars
2. Attrition of incisors
3. Forward growth of mandible

Flush terminal plane
 Mesiodistal

relation between distal surfaces of
upper and lower 2nd deciduous molars is called
as flush terminal plane
 Normal feature of deciduous dentition where
second deciduous molars are in same vertical
plane


MIXED DENTITION PERIOD

1.
2.
3.

Begins at approximately 6yrs.Classified into:
1st transitional period
Inter transitional period
2nd transitional period


FIRST TRANSITIONAL PERIOD



1.
2.
3.

Emergence of 1st permanent molars and exchange of
deciduous incisors with permanent incisors
1st permanent molar erupts at 6yrs-guided into the
dental arch by distal surface of 2nd deciduous molar
Mesiodistal relation between distal surfaces of upper
and lower deciduous molars are of 3 types
Flush terminal plane
Mesial step terminal plane
Distal step terminal plane

FLUSH TERMINAL PLANE
 Mesiodistal

relation between distal surfaces of
upper and lower 2nd deciduous molars is called
as flush terminal plane.
 Normal feature of deciduous dentition where
second deciduous molars are in same vertical
plane.


 Erupting

first molars may be in a flush or end
on relation
 For transition of such an end on molar to a
Class I molar relation, lower molar has to move
forward by about 3-5mm relative to upper
molar
 This can occur in 2 ways. By early shift or late
shift

EARLY SHIFT
 Occurs during early
mixed dentition period
 Eruptive force of
permanent molar pushes
deciduous 1st and 2nd
molars in the arch to
close primate space and
establishing Class I

LATE SHIFT
 Occurs during late mixed
dentition period
 In children who lack
primate space, when the
deciduous molars
exfoliate the permanent
1st molars drift mesialy
utilizing leeway space.


MESIAL STEP TERMINAL PLANE
 Distal

surface of lower 2nd deciduous molar is
more mesial than that of upper. Thus
permanent molars directly erupt into Angles
Class I occlusion
 Occurs due to early forward growth of mandible


DISTAL STEP TERMINAL PLANE
 Distal

surface of lower 2nd deciduous molar lies
more distal to that of upper. Thus erupting
permanent molars maybe in Class II relation


INCISAL LIABILITY
 The

exchange of lower incisors take place. The
difference between the amount of space
needed for the accomodation of incisors and
the space available for this →incisal liability
 It is roughly 7mm in upper arch and 5 mm in
lower arch


Incisal liability
Overcome by the following factors:
1. Utilization of interdental spaces seen in
primary dentition
2. Increase in inter- canine width
3. Change in incisor inclination


INTER TRANSITIONAL PERIOD
 Maxillary

and mandibular arches consists of
sets of deciduous and permanent teeth
 Between permanent incisors and permanent
1st molars are deciduous canines and molars
 This phase during mixed dentition stage is
relatively stable and no change occurs


SECOND TRANSITIONAL PERIOD
 Replacement

of deciduous molars and
canines by premolars and permanent
cuspids respectively


Leeway space of Nance


Combined mesiodistal
width of permanent
canines and premolars
is usually less than that
of deciduous canines
and molars, this is
Leeway space of
Nance


Leeway space of Nance




Greater in mandibular
arch [3.4mm] than in
maxillary arch [1.8mm]
This excess space is
utilized for mesial drift
of mandibular molars to
establish Class I molar
relation


Ugly duckling stage


Transient or self
correcting malocclusion
seen in maxillary incisor
region b/w 8-9yrs seen
during eruption of
permanent canines




As developing
permanent canines
erupt, they displace
roots of lateral incisors
mesially,in turn
transmitting force to
roots of central incisors
which gets displaced
mesially. Resultant
divergence of crown
causes midline spacing




18 years
Last teeth to appear,
the third molars, or the
wisdom teeth, erupt at
about age 18


THANK YOU
Leader in continuing dental education


Development of dentition & occlusion /certified fixed orthodontic courses by Indian dental academy

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