development of normal occlusion

Supervision :
Prof. Dr/ Maher foda
By / Ashraf Almassri

o Neo-natal period.
o Primary dentition period.
o Mixed dentition period.
o Permanent dentition period.

Neonatal Period
(lasts up to 6 months after birth)

•Alveolar processes at the time of birth- gum
pads.
• Pink in color, firm and are covered by a
dense layer of fibrous periosteum.

• The gum pad soon gets
segmented by a groove called
transverse groove, & each
segment is a developing tooth
site.
• The pads get divided into
‘labio-buccal’ & ‘lingual
portion’, by a dental groove.
• The groove between the canine
and the 1st molar region is
called the lateral sulcus, useful
for judging the inter arch
relationship at a very early
stage.

• The upper gum pad is horse shoe
shaped & shows:
o Gingival groove: separates gum
pad from the palate.
o Dental groove:
o starts at the incisive papilla, extends
backward to touch the gingival
groove in the canine region &
then moves laterally to end in the
molar region.
o Lateral sulcus.
Gum pads

• The lower gum pad is‘U’
shaped and rectangular,
characterized by:
o Gingival groove:
lingual extension of the
gum pads.
o Dental groove.
o Lateral sulcus.
Gum pads

• Anterior open bite is seen at rest
with contact only at the molar
region.
• Complete overjet.
• Class II pattern with maxillary
gum pad being more prominent.
• Mandible is distal to the maxilla of
2.7 mm- male and 2.5- female.
• The range of variation of this distal
relationship is from 0 to 7 mm. . (
Sillman JH 1938)
Relationship of Gum Pads

o Mandibular lateral sulci
lies posterior to maxillary
lateral sulci.
o Mandibular functional
movements are mainly
vertical, and to a little
extent antero-posterior.
Lateral movements are
absent.
Relationship of Gum Pads

• A ‘precise bite’ or jaw
relationship is not yet
seen. Therefore, neonatal
jaw relationship cannot be
used as a diagnostic
criterion for reliable
prediction of subsequent
occlusion in the primary
dentition.

Pre-erupted teeth’ or ‘Early Invasive teeth’ are teeth that erupt during
the 2nd or 3rd month.

• Classification
Hebling (1997) classified natal teeth into 4 clinical categories:
1. Shell-shaped crown poorly fixed to the alveolus by gingival
tissue and absence of a root;
2. Solid crown poorly fixed to the alveolus by gingival tissue
and little or no root;
3. Eruption of the incisal margin of the crown through gingival
tissue
4. Edema of gingival tissue with an unerupted but palpable
tooth.
Natal/neonatal teeth

• Gender
Predilection for females
Kates et al (1984) reported a 66% proportion for females
against a 31% proportion for males.
• Etiology
It has been related to several factors, such as:-
Superficial position of the germ
 Infection or malnutrition
Eruption accelerated by febrile incidents or hormonal
stimulation,
 Hereditary transmission of a dominant autosomal gene
 Osteoblastic activity inside the germ area related to the
remodeling phenomenon and hypovitaminosis

• Associated syndromes
Hallerman-Streiff
Ellis-Van Creveld
 Craniofacial dysostosis
 Multiple steatocystoma
 Congenital pachyonychia
 Sotos Syndrome.

• Complications
Interfere with feeding
Risk of aspiration
Traumatic injury to the baby’s tongue
and/or to the maternal breast
Riga-Fede disease- oral condition
found, rarely in newborns manifests
as an ulceration on the ventral surface
of the tongue or on the inner surface of
the lower lip. Caused by trauma to the
soft tissue from erupted baby teeth.
Riga-Fede disease

 (From around the 6th month to 6 years)

Root
completed
(years)
Eruption
(months)
Crown
completed
(months)
First evidence
of calcification
(Weeks in uteri)
Primary
(upper)
11/21011/214 (13-16)Central
21121/216Lateral
31/419917Canine
21/2166151/21st molar
32911192nd molar
Chronology of Primary Dentition

Root
completed
(years)
Eruption
(months)
Crown
completed
(months)
First
evidence of
calcification
(Weeks in
utero)
Primary
(Lower)
11/28(6-10)21/214 (13-16)Central
11/213( 10-16)316Lateral
31/420(17-23)917Canine
21/416( 14-18)51/2151/2
1st molar
32710182nd molar
Chronology of Primary Dentition

• There are 48 teeth/parts of teeth present in the jaw. It is
at this time that there are more teeth in the jaws than at
any other time.

• Spacing- 2 types of dentition are
seen:
• A) Spaced dentition - usually
seen in the deciduous dentition to
accommodate the larger
permanent teeth in the jaws.
• More prominent in the anterior
region, and are called
‘physiological spacing’ or
‘developmental spacing’.
• Absence of spaces in the primary
dentition is an indication that
crowding of teeth may occur when
Features Of Primary Dentition

• Most subhuman primates have
it through out life and use it for
interdigritation of the opposing
canines. This space is used for
early mesial shift.
primate spaces’, ‘simian spaces’
or ‘anthropoid spaces’.

• Non- spaced dentition
Teeth are present without any
spaces in between the teeth
 Due to narrow dental arches or
if teeth are wider than usual
 Usually indicates in
developing permanent dentition
but it is not always the case

• Shallow overjet & overbite. Initially a deep bite may occur
due to the fact that the deciduous incisors are more upright
than their successors. The lower incisal edges often contact
the cingulum area of the maxillary incisors. This deep bite is
later reduced by:
o Eruption of deciduous molars.
o Attrition of incisors.
o Forward movement of the mandible due to growth.

Ovoid arch Form
Features Of Primary Dentition contd…

• The molar relationship in the primary dentition can be
classified into 3 types:
o Straight/flush terminal plane.
o Mesial step.
o Distal step.
Molar Relationship

• If the distal surface of maxillary
and mandibular deciduous
second molars are in the same
vertical plane; then it is called a
flush terminal plane
• Normal molar relationship in
the primary dentition, because
the mesiodistal width of the
mandibular molar is greater than
the mesiodistal width of the
maxillary molar.
Flush Terminal Plane:

• Distal surface of
mandibular deciduous
second molar is mesial to
the distal surface of
maxillary deciduous
second molar.
Mesial step :

•Distal surface of mandibular
second deciduous molar is more
distal to the distal surface of the
maxillary second deciduous
molar
Distal Step :

• Relationship of maxillary &
mandibular deciduous canines is
one of the most stable in primary
dentition
• Classified as:
Class 1
Class 2
Canine relationship

• The mixed dentition period can be divided into
three phases:
o First transitional period.
o Inter-transitional period.
o Second transitional period.
Mixed Dentition Period
(Around 6 years- 12 years)

The location & relation
of the 1st permanent
molar depends much
upon the distal surface
of the upper & lower 2nd
deciduous molar.
Eruption of 1st Permanent Molar

• The shift in lower molar from a flush terminal
plane to a class I relation can occur in two
ways:
Transition to Class I Molar Relation
oEarly shift.
oLate shift.

• Early shift occurs during the early mixed dentition period.
• Since this occurs early in the mixed dentition, it is called
early shift. (at 6 yrs old)
Early Shift

• This occurs in the
late mixed dentition
period and is thus
called late shift.
(at 11 yrs old)
• Used leeway space
.
Late shift

• Described by Nance in 1947
•Maxilla: 0.9 mm/segment = 1.8
mm.
• Mandible: 1.7 mm/segment =
3.4mm.
Leeway Space of Nance

• Although the deciduous posterior segment of teeth is larger
than the permanent segment, converse is true of the anterior
segments
• Nance did not consider large difference in mesiodistal size
between the deciduous incisor teeth & their permanent
successors– arch needs to be looked in its totality
• Maxillary incisors, as a group in one quadrant– 3.2to 3.5 mm
larger
• Mandibular incisors, as a group in one quadrant – 2.4 to 2.5
mm larger
• The latter figures balance out or cancel the 1.7 mm of so called
leeway space

• Moorrees -- measurements of
deciduous & permanent teeth in
the mouths obtained by
longitudinal studies, there is no
leeway space
• Total no. of permanent teeth
destined to replace total no. of
deciduous teeth in an average
child – slightly less than 1mm
more space in mandibular arch,
6mm more in maxillary arch
• 1.7 mm leeway space taken up
by the larger permanent incisors,
requires more distal eruption of
permanent canines
• Allows reduction of incisor
crowding in mandibular arch

• If the permanent molars were allowed or even
encouraged to drift mesially and utilize the leeway space
– no enough room in the arch for the incisor segment
• Initially – permanent incisors are forced into a crowded
position
• If molars are held stable, incisors will utilize the leeway
space, ultimately the average mandibular arch will have
enough room for proper alignment

• l Usually occurs in primary
arches that have no primary
spacing.
• When the md permanent lateral
incisors erupt, the primary md
canines are moved laterally,
thus creating space for the
maxillary permanent lateral
incisors.
• Secondary spacing can also
occur during the eruption of
permanent central incisors
Secondary spacing

• When the deciduous
second molars are in a
distal step, the
permanent first molar will
erupt into a class II
relation. This molar
configuration is not self
correcting and will cause
a class II malocclusion
despite Leeway space
and differential growth.
Distal step :

• Primary second molars in
mesial step relationship
lead to a class I molar
relation in mixed
dentition. This may
remain or progress to a
half or full cusp class III
with continued
mandibular growth.
mesial step :

Distal Step – 23.3%
incidence, abnormal, Class
II- 38.6%
•Straight terminal plane –
49.2% incidence, Class I
or II
•Mesial Step - <2mm
26.7%, class I 58.9%
•>2mm 0.8%. Class III-
2.5%

During the first transitional period the
deciduous incisors are replaced by the
permanent incisors. The mandibular
central incisors are usually the first to
erupt. The permanent incisors are
considerably larger than the deciduous
teeth they replace. This difference
between the amount of space needed for
the accommodation of the incisors and the
amount of space available for this, is
called ‘Incisal liability ’. The incisal
liability is roughly about 7.6 mm in the
maxillary arch & about 6 mm in the
mandibular arch (Wayne).

Transition of
Incisors
The incisal liability is over come by
the following factors:
Interdental physiological spacing in the primary
incisor region. (4 mm in maxillary arch & 3 mm
in mandibular arch)

• Increase in inter-canine arch width:
• Significant amount of growth occurs with the eruption of
incisors and canines. That creates more room for the
permanent incisors.

• Increase in anterior length of the dental arches:
• Permanent incisors erupt labial to the primary incisors to
obtain an added space of around 2-3 mm.

• Change in inclination of permanent incisors:
• Primary teeth are upright but permanent teeth incline to
the labial surface, thus decreasing the inter-incisal angle
from about 151 degrees in the deciduous dentition to 124
degrees in the permanent dentition. This increases the
arch parameter.

Inter-Transitional Period
This is a stable phase where little
changes take place in the dentition.
The teeth present are the permanent
incisors and first molar along with the
deciduous canines and molars. This
phase prepares for the second
transitional phase. Some of the
features of this stage are:
o Any asymmetry in emergence and
corresponding differences in height
levels or crown lengths between the
right and left side teeth are made up.

• Root formation of
emerged incisors, and
molars continues,
along with concomitant
increase in alveolar
process height.

• Resorption of roots of
deciduous canines and
molars.

Second Transitional Period
The second transitional period is
characterized by the replacement of
the deciduous molars and canines by
the premolars and permanent canines
respectively. At around 10 years of
age the deciduous canines shed, but
just before the shedding there is a
transient or self correcting
malocclusion seen in the maxillary
incisor region between the age of 8 –
9 years.

• Around the age of 8 - 9
years, a midline diastema is
commonly seen in the upper
arch, which is usually
misinterpreted by the parents
as a malocclusion.
• Its typical features are:
o Flaring of the lateral incisors.
o Maxillary midline diastema.
Ugly Duckling Stage
(Broadbent’s phenomenon)

• Crowns of canines on young
jaws impinge on developing
lateral incisor roots, thus
driving the roots medially
and causing the crowns to
flare laterally.The roots of
the central incisors are also
forced together, thus
causing a maxillary midline
diastema.
Ugly Duckling Stage
(Broadbent’s phenomenon)

• With the eruption of the
canines, the impingement
from the roots shift incisally
thus driving the incisor
crowns medially, resulting in
closure of the diastema as
well as the correction of the
flared lateral incisors.

• The canines in the upper
arch erupt only after the
premolars have replaced
the deciduous molars,
whereas the canine erupt
before the premolars in
the lower arch.
Sequence of Eruption

• Favorable occlusion in this area is largely
dependent on:
Second Transitional Period contd…
o Favorable eruption
sequence.
o Satisfactory tooth size to
available space ratio.
o Attainment of normal molar
relation with minimum
diminution of space available
for the bicuspids.

Eruption of permanent second molars
• Before emergence- second molars, oriented in a mesial
& lingual direction
• Teeth- formed palatally , guided into occlusion by Cone
Funnel mechanism , upper palatal cusps (cone) slides
into the lower occlusal fossa (funnel)
• Arch length is reduced by mesial eruptive forces
• Thereby, crowding if present is accentuated

• This period is
marked by the
eruption of the four
permanent second
molars.
The Permanent Dentition

Nolla’s Stages of Tooth Development
Moyers
In 1960 Nolla studied the stages of tooth
development using panoramic & postero-anterior
radiographs.

Calcification begins at birth
with the calcification of the
cusps of the first
permanent molar and
extends as late as the 25th
year of life. Complete
calcification of incisor
crowns take place by 4 – 5
years and of the other
permanent teeth by 6 – 8
years except for third
molars.

Chronology of Permanent Dentition
Root
completed
(years)
Eruption
( months)
Crown
completed
(months)
First
evidence of
calcification
( weeks in
utero)
Permanent
(Upper)
107-8 yr4-5 yr3-4 moCentral
118-9 yr4-5 yr10-12 moLateral
13-1511-12 yr6-7 yr4-5 moCanine
12-1310-11 yr5-6 yr11/2-13/4 yr1st premolar
12-1410-12 yr6-7 yr2-21/4 yr2nd premolar
9-106-7 yr21/3-3 yrAt birth1st molar
14-1612-13 yr7-8 yr21/3-3 yr2nd molar
18-2517-21 yr12-16 yr7-9 yr3rd molar

Root
completed
( years)
Eruption
( months)
Crown
completed
(months)
First
evidence of
calcification
( weeks in
utero)
Permanent
(Lower)
96-7 yr4-5 yr3-4 moCentral
107-8 yr4-5 yr3-4 moLateral
12-149-10 yr6-7 yr4- 5 moCanine
12-1310-12 yr5-6 yr13/4-2yr1st premolar
13-1411-12 yr6-7 yr21/4-21/2 yr2nd premolar
9-106-7 yr21/2-3yrAt birth1st molar
14-1511-13 yr7-8 yr21/2-3yr2nd molar
18-2517-21 yr12-16 yr8-10 yr3rd molar

• The permanent
incisor develop lingual
to the deciduous
incisor and move
labial as erupt.

•The premolar develop
•below the diverging root
•of the deciduous molars.

• At approximately 13 yrs
of old all permanent
teeth except third molars
are fully erupted .

Features of Permanent
Dentition
• Coinciding midline. Class I molar
relationship.

• Vertical overbite of
about one third the
clinical crown height
of the mandibular
central incisors.
Overjet and over bite
decreases throughout
the second decade of
life due to greater
forward growth of the
mandible.

• Key I – Molar
relationship
MB cusp of the max 1st
molar falls into the
mesiobuccal groove of the
mand 1st molar and that
the distal surface of the
DB cusp of the upper first
permanent molar should
make contact and occlude
with mesial surface of the
MB cusp of the lower
second molar.
Andrews keys to normal
occlusion

Key II Crown angulation
(Tip)
• The angulation of the
facial axis of every
clinical crown should
be positive
• The gingival portion of
the long axis of the all
crowns must be distal
than the incisal
portion.
occlusion

Key III Crown inclination
• In upper incisors, the gingival
portion of the crown’s labial
surface is lingual to the
incisal portion.
• In all other crowns, including
lower incisors, the gingival
portion of the labial or buccal
surface is labial or buccal to
the incisal or occlusal
portion.
occlusion

Key IV – Rotations
• The fourth key to normal
occlusion is that the
teeth should be free of
undesirable rotations.
occlusion

Key V – Tight contacts
• contact points should be
tight (no spaces).
• In absence of
abnormalities such as
genuine tooth size
discrepancies, contact
point should be tight.
occlusion

Key VI – Occlusal plane or
curve of spee
• The curve of Spee should
have no more than a slight
arch.
• Intercuspation of teeth is best
when the plane of occlusion is
relatively flat.
• A deep curve of Spee results
in a more contained area for
the upper teeth, making
normal occlusion impossible.
occlusion

Key VII – Correct tooth size or
the bolton’s ratio
• Bennett and McLaughlin in
1993 gave seventh key to
normal occlusion. i.e. the upper
and lower tooth size should be
correct.
occlusion

 Roth (1981) added some functional keys to the
previous six keys to normal occlusion by Andrew:
a) Centric relationship and centric occlusion should be
coincident.
b) In protrusion, the incisors should disclude the posterior teeth,
with the guidance provided by the lower incisal edges passing
along the palatal contour of the upper incisors.
c) In lateral excursions of the mandible, the canine should guide
the working side whilst all other teeth on that and the other
side are discluded.
d) When the teeth are in centric occlusion, there should be even
bilateral contacts in the buccal segments.

1. Arch Length Discrepancy
1. Crowding
2. Spacing
2. Deviation in no. of teeth-
1. Absence of teeth ( Agenesis)
2. Supernumerary teeth
Abnormalities in dental arch

• Sequence of
agenesis is – :
• 3rd molar > Mand.
2nd premolars > Max
Lateral Incisors >
Max. 2nd Premolar
Absence of teeth ( Agenesis)

•Its relative in nature
•All teeth combined > or < relative to size of
jaws or head.
•Crowding
•Spacing
•Deviation in size of individual teeth
•Tooth size Discrepancy
Deviation in tooth
size

•Frequent in mand deciduous
molars.
• In permanent 2 types
•Due to abnormal position within
jaw
• Max perm. Canine
•Due to lack of space
•Mand 3rd molar
Ankylosis

In its simplest of definition, occlusion is the way the maxillary and
mandibular teeth articulate, but in reality dental occlusion is a much more
complex relationship, because it not only involves the study of the teeth, but
also their morphology and angulations, the muscles of mastication, the
skeletal structures, the temperomandibular joint, and the functional jaw
movements. In addition to this, it also involves the relationship of the teeth in
centric occlusion, in centric relation, and even during function, and because
all this, requires neuromuscular coordination, occlusion should also involve
an understanding of the neuromuscular systems, and if we need to determine
an abnormal course of development, it is the responsibility of we
‘pedodontists’ to have an adequate knowledge on these subjects, to help us
differentiate abnormal from normal, before initiating therapy.

development of normal occlusion

development of normal occlusion

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