2. Infancy and Early childhood:
Premature birth: Low birth weight
Infant weighing less than 2500 gm at birth are at
greater risk of problems. Until recent years,
children with birth weights below 1500 gm often did
not survive.
With best of the medical facility available some now
are saved.
3. If premature infant survives the neonatal period,
however, there is every reason to expect that
growth will follow the normal pattern and that the
child will gradually overcome the initial handicap.
Chronic illness: For normal infant 90% of the
available energy must be utilized by the child for
the requirement of survival, thus leaving only 10%
for the growth.
4. Chronic illness alters this balance and affects the
growth of the child. The more chronic the illness,
greater the cumulative impact.
Maturation of oral function: Respiratory
movements are “practiced” in utero. Swallowing
also occurs during the last months of fetal life, it
appears that swallowed amniotic fluid may be an
important stimulus to activation of the infant’s
immune system.
5. Suckling and swallowing:
Suckling consist of small nibbling movements of
the lips, to stimulate the smooth muscle and to
contract and squirt milk into his mouth. The
tongue is placed anteriorly in contact with the
lower lip. And it is only necessary for infant to
groove the tongue and allow the milk to flow
posteriorly into the pharynx.
6. This sequence of events defines an infantile
swallow, which is characterized by active
contractions of the musculature of the lips, a tongue
tip brought forward into contact with the lower lip,
and little activity of the posterior tongue or
pharyngeal musculature.
7. • The suckling reflex and the infantile swallow
normally disappears during the first year of life.
• And infant matures the semisolid food is
replaced by the solid food. And child learns to
use the tongue in a more complex way.
• The first speech sounds are the bilabial sounds
“m”, “p”, “b” which is why the an infant first
word is likely to be “mama” and “papa”.
8. Survey of American Children indicate that at age 8
about 60% have achieved adult swallowing pattern,
while remaining 40% are still in transition.
Eruption of Primary Dentition
Eruption of permanent dentition
9. Important features during transition from primary
dentition to permanent dentition:
• It is seen that both in maxillary and mandibular
arches the permanent incisor tooth buds lie lingual
to the primary incisors.
• As the result is the tendency for mandibular
incisor
10.
11. Permanent incisor teeth are considerably larger than
the primary incisor that they replace, as the each
permanent incisors and the canines are 2-3mm
wider than the their primary teeth, the spacing in
the primary dentition is not only important but it is
very critical.
12. Primate spaces/ Anthropoid spaces: The name given
for the spaces present mesial to the canines in the
maxillary arch and distal to the deciduous canines in
the mandibular arch. This is approximately 1-2mm
in each arch. The primate space are normal features
of deciduous dentition and are required critically for
accommodating the emerging permanent incisors.
13. This is the amount of discrepancy of space arising
during the eruption of permanent incisors.
When the central incisor erupt, these teeth use
essentially all the excess space found in the normal
primary dentition. Thus with the eruption of lateral
incisors the space situation becomes more tight in
both arches. In the maxillary arch, on the average,
has just enough space to accommodate the lateral
incisors. But in the mandible arch when the lateral
incisor erupt on the average 1.6mm less space
available for the four mandibular incisors.
Incisor liability:
14.
15. • This difference between the amount of space
needed for the incisors and the amount of available
space is termed as incisor liability
• Because of this a normal child will go through a
transitory stage of lower incisor crowding at the age
of 8-9yr.
• Continued development of arches improve this
spacing situation and by the time canines erupt the
space once again is adequate.
16. The problem of incisor liability is usually overcome
during normal growth by following mechanisms:
1. A slight increase in the width of the dental arch
across the canines. This increase is about 2mm
on an average. This increase more in the maxilla
compare to the mandible. And it is more in boys
compare to girls.
17. 2. Labial positioning of permanent incisors relative to
the primary incisors. The primary incisors tend to
stand upright. As the permanent incisor replace
they lean slightly forward arranging in the
broader arc. This is about 1-2mm in normal child.
3. Repositioning of the canines in the mandibular
arch. The permanent canine teeth not only widen
out slightly but move back into the primate
spaces.
18.
19. Ugly duckling stage: In the maxillary arch mutually
there will be a central diastema in the primary
dentition and it tend to close as the lateral incisor
erupt. Usually upper canines during their path of
eruption tends to go more mesial to hit the roots of
the lateral causing to increase the diastema and
transient lateral flaring maxillary lateral incisors. As
the canines erupt this situation of ugly duckling
stage is resolved.
20. Leeway space : In contrast to the lesser width of
primary incisors the primary molars have greater
mesiodistal width compare to the their permanent
premolars which eventually replaces them.
As the result each side of mandibular arch contents
about 2.5mm of space known as Leeway Space.
This Leeway space in the maxillary arch is 1.7mm.
Usually the lower permanent molar migrates forward
into this leeway space during the course of normal
development of dentition.
21.
22.
23. • The occlusal relationship in the mixed dentition
is usually flush terminal plane.
• The primary dentition equivalent of Angle Class
II is the distal step.
• A mesial step corresponds to class I
24. Transient Malocclusions during the course
of Normal development of Dentition.
1. Spacing in the primary dentition
2. Primate spaces
3. Ugly duckling stage
4. Lower incisor crowding – incisor liability
5. Flush terminal plane in the primary dentition
which eventually replaces to the class I in
permanent dentition.
6. Slight convex profile. As the mandibular
skeletal growth is slightly slower and continued
late during adolescent years.
