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Development of occlusion
1.
2. Index
• Introduction
• Periods of occlusal development
Neo-natal period.
Primary dentition period.
Mixed dentition period.
Permanent dentition period
• References
3. Term occlusion is derived from the Latin word,
“occlusio”; defined as the relationship
between all the components of the
masticatory system in normal function,
dysfunction and parafunction. An ideal
occlusion is the perfect interdigitation of the
upper and lower teeth, which is a result of
developmental process consisting of the three
main events, jaw growth, tooth formation and
eruption
4. Periods of tooth development
Pre-dental Stage
(0-6months)
Deciduous
dentition (6
months-6 years)
Mixed dentition
(6-12 years)
Permanent
dentition
6. Gum Pads• Alveolar processes at the time of birth- gum pads.
• Pink in colour, 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.
7. Gum Pads contd…
The upper gum pad is horse shoe
shaped & shows:
o Gingival groove: separates
gum pad from the palate.
o Dental groove: 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.
8. Gum Pads contd…
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.
9. Relationship of Gum Pads
o Anterior open bite is seen at rest
with contact only at the molar region.
o Complete overjet.
o Class II pattern with maxillary gum
pad being more prominent.
o Mandible is distal to the maxilla of
2.7 mm- male and 2.5- female.
( Sillman JH 1938)
oThe range of variation of this distal
relationship is from 0 to 7 mm. .
( Sillman JH 1938)
10. 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.
11. 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.
14. Features Of Primary Dentition
• 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 the larger
permanent teeth erupt.
15. Features Of Primary Dentition
contd…
• Most subhuman primates
have it through out life and use
it for interdigitation of the
opposing canines. This space is
used for early mesial shift.
primate spaces’, ‘simian spaces’ or
‘anthropoid spaces’.
16. Features Of Primary Dentition contd…
• 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
17. Features Of Primary Dentition
contd…
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:
oEruption of deciduous molars.
oAttrition of incisors.
oForward movement of the mandible due to growth.
19. Molar Relationship
The molar relationship in the primary dentition can be classified
into 3 types:
oStraight/flush terminal plane.
oMesial step.
oDistal step.
20. Flush Terminal Plane
• 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.
21. Mesial Step
Distal surface of mandibular
deciduous second molar is
mesial to the distal surface of
maxillary deciduous second
molar.
22. Distal Step
Distal surface of mandibular
second deciduous molar is
more distal to the distal
surface of the maxillary second
deciduous molar
23. Canine relationship
• Relationship of maxillary &
mandibular deciduous
caninnes is one of the most
stable in primary dentition
• Classified as:
Class 1
Class 2
Class 3
Class 1
Class 2
24.
25. Mixed Dentition Period
(Around 6 years- 12 years)
The mixed dentition period can be divided into three
phases:
o First transitional period.
o Inter-transitional period.
o Second transitional period.
27. Eruption of 1st Permanent Molar
The location & relation of the 1st permanent molar depends much
upon the distal surface of the upper & lower 2nd deciduous molar.
29. Early Shift
• Early shift occurs during the early mixed dentition period.
• Since this occurs early in the mixed dentition, it is called early shift.
30. Late Shift
This occurs in the late mixed
dentition period and is thus
called late shift.
31. Leeway Space of Nance
• Described by Nance in 1947
Maxilla: 0.9 mm/segment = 1.8 mm.
Mandible: 1.7 mm/segment = 3.4mm.
32. • 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
33. Secondary spacing
• Term was coined by Baume
• Observed in closed primary dentition
• Secondary spacing can also occur
during the eruption of permanent
central incisors
34. Distal Step
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.
35. Mesial 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.
36. Influence of terminal plane on the
position of 1st permanent molar
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%
38. 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)
39. Transition of Incisors contd…
Increase in inter-canine arch width:
Significant amount of growth occurs with the eruption of
incisors and canines.
40. Transition of Incisors contd…
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.
41. Transition of Incisors contd…
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 150 degrees in the
deciduous dentition to 123
degrees in the permanent
dentition. This increases the
arch parameter.
43. Inter-Transitional Period contd…
•Root formation of emerged
incisors, and molars
continues, along with
concomitant increase in
alveolar process height.
•Resorption of roots of
deciduous canines and
molars.
45. Ugly Duckling Stage
(Broadbent’s phenomenon)
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:
oFlaring of the lateral incisors.
oMaxillary midline diastema. Crowns of canines on young jaws
impinge on developing lateral incisor roots, thus driving the roots
medially and causing the crowns to flare laterally.
o The roots of the central incisors are also forced together, thus
causing a maxillary midline diastema.
47. Ugly Duckling Stage contd…
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.
48. Ugly Duckling Stage contd…
Hence this unaesthetic metamorphosis, eventually leads to an
aesthetic result.
49. Sequence of Eruption
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.
51. Second Transitional Period contd…
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
52.
53. The Permanent Dentition
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.
54. The Permanent Dentition contd…
The permanent incisors
develop lingual to the
deciduous incisors and move
labially as they erupt.
The premolars develop below
the diverging roots of the
deciduous molars.
55. The Permanent Dentition contd…
At approximately 13
years of age all
permanent teeth
except third molars are
fully erupted.
56. Features of Permanent Dentition
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.
57. Andrews keys to normal occlusion
• 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.
58. 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.
59. Andrews keys to normal 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.
60. Andrews keys to normal occlusion
Key IV – Rotations
• The fourth key to normal
occlusion is that the teeth should
be free of undesirable rotations.
61. Andrews keys to normal 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.
62. Andrews keys to normal 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.
63. Andrews keys to normal 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.
