NORMAL OCCULUSION

1. Development of Normal
Occlusion
Dr.Vivek G. Chitte.
Dept of Orthodontics and Dentofacial
Orthopedics
S.B. Patil institute for Dental Sciences and
Research

2. Contents
 Theories of mammalian dentition.
 Prenatal dental development
a) initiation of odontogenesis - bud , cap , bell stages.
b) spatial patterns - arch shape , spacing
 Mouth of the neonates
a) the gum pads
b) neonatal jaw relationships
c) precociously erupted primary teeth
 Primary teeth at occlusion
a) development of primary teeth
b) development of primary occlusion

3.  Mixed dentition period
a) uses of dental arch perimeter
b) first molar eruption
c) incisor eruption
d) cuspid and bicuspid eruption.
e) second molar eruption
 Development of permanent teeth
a) calcification
b) eruption
 Permanent dentition
a) size of teeth
b) number of teeth
 Dentitional and occlusal development in an young adult
 Conclusion

4. Theories of mammalian dentition.
1)Theory of concrescences -the mammalian
dentition was produced by fusion of two or more
primitive conical teeth and each with its
corresponding root originated as single tooth
2)Theory of tritubercly -Each of mammalian
tooth was derived from a single reptilian tooth by
a secondary differentiation of tubercles and roots
. This theory was widely accepted
3)Theory of multituberculy-the mammalian
dentition is the result of reduction and
condensation of primitive tubercle teeth

5. A)Prenatal dental development
Intitiation of odontogenesis
1) The embryonic developent of both decideous
and permanent proceds in 4 stage
1)initiation 2)bud 3) cap 4) bell
Tooth germ consist of 3 parts.
An enamel organ – which is derived from the
oral ectoderm –that produce enamel.
A dental papilla and dental sac –which are
derived from the mesenchym-dental papilla
produce the dentine and pulp of the tooth
.dental sac produces the cementum and
periodontal ligament

6. • Enamel formation ceases once the tooth
crown is complete but dentine formation
continue with root development .A layer of
cementum is laid down on surface of root
dentine and incorperate periodontal ligament
fibers that support the tooth through its
attachment to the bony wall of tooth socket

7. 2) SPATIAL PATTERNS
A)Arch shape- The prenatal
dental arch progressively
changes shape ; at 6 to 8
week it is ant-post flatter , By
the bell stage of tooth germ
.anterior segment of dental
arch has elongated and
approches the catenary by
beginning of 4th month

8. b)spacing –decideous anterior teeth especially
the lateral inciors often apper crowed and out
of alingment with in total dental arch before
birth but usually erupt n good alingment .

9. B) Mouth of the neonates
1) Gum pads – At birth the alveolar process are
covered by gum pads which soon are
segmented to indicate the site of developing
teeth .Basic form of the arches determined in
intrauterine life

10. NEONATAL JAW RELATION
Arch-
horse shoe Complete
overjet
Contact area
Molar region
Infantile anterior open bite

11. Precociously erupted
primary teeth
Natal teeth
Neonatal teeth

12. Self correcting anomalies
Retrognathic mandible
Differential and
forward growth of
mandible
Anterior open bite
Eruption of primary
incisors

13. Infantile swallowing pattern-
Introduction of solid food in diet
Self correcting anomalies

14. c)Primary teeth and occlusion
1)Development of primary teeth–initiation of
hard tissue development for all deciduous
teeth occurs between 3.5 and 4.5 intrauterine
month .
The crowns have been seen to get mineralized
about half way by birth and become formed
1st 12 month of post natal life .Root formation
continue and is completed after eruption

15. Sequence of initial calcification
Primary teeth
1)Central incisors (14 week)
2)1st molar(15week)
3)Lateral incisors (16week)
4)Canine(17 week)
5)2nd molar(18th week )

16. • Crown completion
6-12month
4-6month
Canine
and
incisor
root completion
1YEAR
Time required for development of primary teeth

17. B) Eruption
• It is defined as axial or occlusal movement of tooth
from its devepmental position with in the jaw to
its functional position in the occlusion plane .
• Types of tooth eruption
• Three distinct types of teeth are differentiated by
their eruption pattern
• 1)continuously growing –Tooth formation and
eruption occurs through out life ,The eruption
velocity which is relatively rapid under normal
function ,increases whenever the velocity of the
wear increases or when antagonist tooth removed
.example of these teeth are the incisors of
roduents and lyomorphs

18. 2)Continuously extruding – Teeth stop forming once
root formation is completed .The height of clinical
crown is maintained by eruption of tooth and
apical migration of the surrounding epithelial
attachment ,with out simultaneously deposition
of alveolar bone. example is the check teeth of
cattle and sheep .
3)Continuously Invested teeth –human teeth
belong to this type of eruption . These teeth also
forming after a predictable amount of root
development has occurred and have distinct
anatomic crown and root structure, but the
alveolar bone remodels in response to eruption .

19. Theories of tooth eruption
1) Bone remodeling –it supposes that selective
deposition and resorption of bone bring about
eruption .
2) Root growth theory – proliferating root
impinges on a fixed case , thus converting an
apically directed force in to occlsal movement .
3) Vascular pressure theory –localised increase in
tissue fluid pressure in the peri apical region is
sufficient to move tooth.
4) Ligament traction theory- it proposes that cells
and fibers of ligament pull the tooth in to
occlusion .

20. Timing of decideous teeth eruption
Teeth Maxillary Mandible
Central incisors 10 mon 8 mon
Lateral incisors 11 mon 13 mon
Canine 19 mon 20 mon
1st molar 16 mon 16 mon
2nd molar 29 mon 27 mon

21. Clinical considerations
• When there is a delayed eruption of an
antimere beyond the six month period , the
clinician should carefully examine the patient
to determine whether appropriate
radiographic evaluation are needed.
• Delayed tooth eruption has a number of
etiological factors but it is important for the
clinician to exclude the presence of any
pathological condition such as a cyst or a
supernumerary tooth.

22. Teething and systemic disturbance
• Teething is term limited by common usage to
eruption of primary dentition .eruption of
primary dentition usually begins in the 5th or
6th month of child life .In most case of
eruption causes no distress to the child or
parent but some times process causes the
local irritation
• Clinical features of teething- local sign –
1) hyperemia or swelling of the mucosa
overlying the erupting teeth 2) patch of
erthema of check

23. • Systemic sign -1) general irritation and crying
2) loss of apetite 3)sleeplessness
4)restlessness 5) incresed salivation and
drooling . associated
problem – systemic –fever , vomiting .
d)Size and shape of primary teeth - the
primary tooth size and it’s mineral mass are
largely inherited . The primary teeth are
smaller in overall size and crown dimensions
more specifically in comparison with
permanent teeth the following differences are
noted-

24. 1. The crown of the primary anterior teeth are
wider mesiodistally in comparison with their
crown length than are the permanent teeth.
2. Roots of primary anterior teeth are narrower
and longer comparatively.
3. The roots of the primary molars accordingly are
longer and more slender and flare more,
extending out beyond projected outline of the
crown.
4. The cervical ridge of the enamel of anterior are
more prominent.
5. Crowns and roots of the primary molars at their
cervical portions are more slender mesiodistally.

25. Molars
Mand: Max -2:1
Physiologic
resorption
PDL resorption
Osseous
bridging and
fusion between
bone and
dentin
Submerged tooth
Failure of vertical
development
Ankylosis of primary teeth

26. Anomalies
Anomalies of crown development are seen less
frequently in primary than in permanent
dentition ,fewer than 1%of all children have
congenitally missing primary teeth , most
commonly missing primary teeth lateral incisors ,
the max central incisors and 1st primary molar
Primary tooth resorption - resorption of decideous
incisors takes more rapidly than that of canine
molars .
The permanent successor may be
visible immediately after exfoliation of decideous
teeth or there may be latent period of 0.1 to 0.5
yr before permanent successors erupts .

27. Development of primary occlusion
A)neuromascular consideration -
The neuromuscular regulation of jaws relation
is important to the development of occlusion.
When teeth are erupted and
muscle are functioning ,the arch formed by
the crowns , is probably not determined by
the muscles

28. Primary dental arches
• Arch dimensions
the size of the primary dental arch can be
measured by dental arch width between the
primary canines and between the primary
molars.
In maxilla
•Increased intercanine
width by 6 mm
between 3-13 yrs
•Increased Intermolar
width of 2 mm between
3-5 yr

29. In mandible
•Increased
intercanine width
by 3.7 mm
between 3 -13 yrs
Increased
Intermolar width
of 1.5 mm
between 3-5 yr

30. • Arch length and circumference
The dental arch length can be
measured from most labial surface
of the primary central incisors to
the canines and to the second
primary molars.
The arch circumference is
determined by measuring the
length of the curved line passing
over the buccal cusps and the
incisor edges of the teeth from the
distal surface of the primary
second molar around the arch to
the distal surface of the other
primary molar.

31. • Arch width
Primary dentition does not show any
substantial increase in width across the
alveolar arch.
• Arch height
There is a little or no increase in the arch
height during the period of primary dentition.

32. Occlusal relation
Primary dentition is complete after eruption
of 2nd primary molar, indicating that the
location of the permanent teeth in future has
already been determined at this stage.
• Primary molar relationship
The mesiodistal relationship between the
distal surface of the upper and lower second
primary molars usually can be classified into
the three types-

33. • Flush terminal or
Vertical plane type- the
distal surfaces of the
upper and lower 2nd
deciduous molar teeth
are in a straight plane
(flush) , usually it is
favorable relationship to
guide the permanent
molars.

34. • Mesial step type- the
distal surface of lower
molar is more mesial to
that of upper. Invariably
it is favorable to guide
the permanent molars
into class I relationship.

35. • Distal step type -
distal surface of lower
molar is more distal
to that of the upper.
This relation is
unfavorable as it
guides the permanent
molars into distal
occlusion.

36. Anterior teeth relationship
• Overbite- it is the distance
which the incisor edge of
the maxillary incisors
overlap vertically to the
incisor edge of the
mandibular incisors
• Average overbite in primary
dentition is 2 mm.

37. • Overjet - it is the
horizontal distance
between the lingual aspect
of the maxillary incisors
and labial aspect of the
mandibular incisors, when
the teeth are in centric
relation.
• The average is 1-2 mm.

38. • Canine relationship
The relationship of the maxillary
and mandibular deciduous
canines is one of the most stable
in primary dentition.
It is classified as -
Class I - when the mandibular canine interdigitates in
embrasure between the maxillary lateral and canine
Class II - where mandibular canine interdigitates distal
to the embrasure.

39. The normal signs of primary dentition
• Spaced anteriors
• Primate space
• Shallow overbite and overjet
• Straight terminal plane
• Class I molar and cuspid relationship
• Almost vertical inclination of anterior teeth
• Ovoid arch form

40. Mixed dentition

41. Mixed dentition
• Period of both primary and
permanent dentition
• Clinical importance
– utilization of arch
perimeter
– Adaptive changes in
occlusion
– Orthodontic intervention

42. •Mixed dentition
•Three phases
•First transitional
period.
•Inter transition period.
•Second transitional
period

43. • First transitional
period :-
–Emergence of first
permanent molars.
–Exchange of deciduous
incisors with
permanent incisors.
–Establishment of
occlusion

44. • Inter transitional
period
–Both sets of
dentition
• Permanent incisors,
1st molars
• Deciduous canines,
1st ,2nd molars

45. • Second
transitional period
–Emergence of
Bicuspids, cuspids,
2nd molar.
–Establishment of
occlusion

46. • Occlusal changes in
mixed dentition
–Flush terminal plane of
primary dentition
• Cl -I molar relations
achieved by.
-- early mesial shift
–Late mesial shift

48. • 1st molar eruption
–Mandible
• Guidance by distal
surface of 2nd primary
molar
• Mesial and lingual
path of eruption
–Maxilla
• Distal and buccal
path of eruption
• Forward movement
of maxillary growth
– Space created
posteriorly

49. Molar adjustment
• Closure of primate space
–Early mesial shift
–Late mesial shift-
• Mesial migration of first
permanent molar after
loss of second
deciduous molar using
leeway space.

50. Difference of space
–Leeway space
• Mandible- Per
quadrant 1.7mm
• Maxilla- 0.9mm

51. Incisor eruption Mandible
– Peramanent mandibular
incisors lingually to primary
incisors.
– Lingual activity moves the
permanent incisors labially to
their normal balanced
position.
– Lateral incisors as they
emerges not only push the
lateral primary incisors
labially but also move the
primary cuspids distally and
laterally.

52. • Maxilla
- Maxillary permanent incisors
erupt with more labial
inclination than primary
teeth.
- Maxillary lateral incisors - it ‘s
more difficult in assuming
their normal position.
Developing crowns of
maxillary cuspids lie just
labially and distally to their
roots.

54. CLINICAL CONSIDERATIONS
• Following the eruption of mandibular central
and lateral incisors , the arch width
measurements in the lower arch are
essentially established.
• Lower arch length after the eruption of first
permanent molars decreases with the loss of
primary molars and mesial moment of first
permanent molars in the leeway space.
Because of these limitations most clinicians
consider the lower arch as the key to
orthodontic diagnosis.

55. • Cuspid and Bicuspid eruption
Favorable development of occlusion
1) Favourable sequence of eruption
2) Satisfactory tooth size- available space ratio
3) Attainment of normal molar relationship with
minimal diminution of space available for
bicuspid
4) Favourable bucco- lingual relationship of
alveolar process

56. Mandible
• Favourable eruption
sequence
– 6-1-2-3-4-5-7
• Eruption of canine
–Maintenance of arch
perimeter
–Increased
intercanine width
–Prevention of lingual
tipping of incisors
–Hastened by
extraction of primary
cuspids

57. Eruption of 1st
Bicuspid
• Rarely any
difficulty
• Sometimes
rotation due to
uneven
resorption of
primary molar

58. • Eruption of 2nd
bicuspid
–Last succedaneous
tooth to erupt
–Eruption complication
• Mesial migration of 1st
molar
• Tooth size- Space
available ratio poor
• Premature exfoliation
of 2nd primary molar
–Extreme variation in
calcification and
development schedule

59. • Maxilla
–Sequence of eruption
• 6-1-2-4-5-3-7 or
• 6-1-2-4-3-5-7
–Displaced labially
• Habits
–Affect eruptive
pattern of cuspid
and bicuspid

60. • Maxilla
• 1st bicuspid
• Minimal difficulty in
eruption
• Same size as primary
predecessor
• 2nd bicuspid
Easy eruption
• Larger mesiodistal
width of primary
predecessor

61. • Cuspid
–Use of Leeway space
to accommodate
–More tortuous path of
eruption
–Favourable sequence
• Cuspid before 2nd
molar
–Labioversion with
mesial inclination

62. Ugly duckling stage
(Broadbent Phenomenon)

63. • 2nd molar eruption
– Last to erupt before 3rd
molar
– Mandible
• If precede 2nd bicuspid
tips the 1st molar
mesially
– Maxilla
• Eruption before
mandibular 2nd molar
• Symptom of developing
C-lI relation
– Max. molar eruption
before mand. molar-
symptomic C lI

64. Mixed dentition
• Molar eruption
• Incisor eruption
• Leeway space

65. Permanent dentition

66. Development of the permanent teeth
Calcification-the
calcification of the
teeth has been
studied in many ways,
serial radiograghic
methods are the most
practical .
Girls are more
advanced in
calcification of
permanent teeth than
the boys .
 Nolla’s stages

67. Eruption
Interrelation between calcification and eruption
•Developmental process that moves a tooth from it’s
crypt position through the alveolar process into the
oral cavity and to occlusion with it’s antagonist
•Onset of Movement of tooth after crown formation
•2 to 5 years for the posterior teeth to reach the
alveolar crest following completion of their crown.
•12 to 20 months to reach occlusion after reaching
alveolar margin.

68. • PRERUPTIVE - initial position of tooth germ
depends on hereditary factors.
• INTRAALVEOLAR - the tooth position affected by
1) presence or absence of adjacent teeth
2) rate of resorption of primary teeth
3) early loss of primary teeth
4) localized pathological condition
• INTRAORAL - tooth can be moved by lip, cheek,
tongue muscle or external object and drift into
space.
• OCCLUSAL - the muscles of mastication exerts
influence through interdigitation of cusps. The
periodontal ligament disseminates the strong
forces of chewing to the alveolar bone.

69. Factors regulating and affecting
eruption
• Both the sequence and the timing of eruption
seems to be largely gene determined .
• There are important racial difference in timing of
permanent tooth emergence .The great
difference for incisors and molars ;the for the
cuspids and premolars .
• The nutritional influence on calcification and
eruption are relatively much less significant than
the genetic.
• The mechanical disturbances can alter the
genetic plan of eruption as can localized pathosis.

70. • Sex Difference
Except for third molars girls erupt their
permanent teeth an average of approximately
5 months earlier than boys.
• Sequence of Eruption
– Maxillary-
• 6-1-2-4-3-5-7 or
6-1-2-4-5-3-7
– Mandibular-
• 6-1-2-4-3-5-7 or
6-1-2-3-4-5-7

71. Teeth Maxillary Mandibular
Central incisor 7 ¼ yrs 6 ¼ yrs
Lateral incisor 8 ¼ yrs 7 ½ yrs
Canine 11 ½ yrs 10 ½ yrs
First premolar 10 ¼ yrs 10 ½ yrs
Second premolar 11 yrs 11 ¼ yrs
First molar 6 ¼ yrs 6 yrs
Second molar 12 yrs 12 yrs
Third molar 20 yrs 20 yrs
Time for permanent tooth
eruption

72. • Ectopic development
– Teeth developing away from normal position
– Most common- Max.1st molar, canine, mand.
Cuspid, max 2nd premolar, max lateral
• Large primary and permanent teeth
• Diminished max. Length
• Posterior position of maxilla
• Atypical angle of eruption
– Sexual dimorphism
The treatment for this difficult problem is best begun
early in dental development in order to utilize the
natural force of eruption.

73. Permanent dentition
• Size of the tooth
1) The tooth size is largely determined genetically.
2) Female tooth size commonalities are greater
than males.
• Number of the teeth
missing teeth - complete absence of teeth is
termed as anodontia. Incomplete formation of
dentition is termed as oligodontia.
The teeth most frequently absent are -
1. mand. Second premolar
2. Max. lateral incisors
3. Max. second premolars

74. Supernumerary teeth
These are encountered less frequently than
other congenitally missing teeth. More often
occur in maxilla particularly in the
pre maxillary region.

75. Dimensional changes in the dental
arch
• Dimensional changes in the dental arches
– Combined width of teeth
– Dimensions of dental arches in which the teeth are
arranged
– Dimension of basal bone

76. • Width increase dependant on alveolar process
growth.
• The maxillary alveolar processes diverge while
mandibular alveolar processes are more
parallel.
• Clinical significance -
midpalatine suture can be
reopened with rapid palatine
expansion to acquire the large amount of
widening of maxilla.

77. • Length or depth
it is measured at the midline from a point
midway between the central incisor to a
tangent touching the distal surface of second
primary molars or the second premolars.

78. • Circumference or perimeter
Reduction in mandibular
arch circumference.
Late mesial shift
Mesial drifting tendency
Lingual positioning of incisors
due to differential
mandibulomaxillary growth
Original tipped position of
incisors and molars
Localized factors
3rd molar eruption
Maxillary arch perimeter
Angulation of incisors-
Preservation

79. Overjet and overbite
Primary dentition- Almost
zero
Mixed to permanent
dentition-
Overbite-
Increases followed by
decrease
Correlates with no. of
facial variations
Overjet
Anteroposterior skeletal
relationship
Sensitivity to abnormal
lip and tongue function

80. Andrew’s six keys of occlusion
• These are a set of six characteristics that were
consistently present in collection of 120 casts
of naturally optimal occlusion, identified by Dr.
Lawrence F Andrews.

81. Andrew’s six keys of occlusion
• Inter- arch relationship
– Molar
• Maxillary 1st
– Mesiobuccal cusp
– Mesiolingual cusp
– Distal marginal ridge

82. Andrew’s six keys of occlusion
• Interarch
relationship
–Premolar
• Cusp-Embrasure
–Canine
• Cusp-Embrasure
–Incisor
• Maxillary
overlap

83. Andrew’s six keys of occlusion
• Mesio-distal crown
Angulation
– The gingival
portion of the long
axis of crown is
more distal than
the incisal portion

84. Andrew’s six keys of occlusion
• Labio-lingual
crown inclination
– Maxillary incisors
• Positive inclination
– Mandibular
incisors
• Slightly negative
inclination.

85. Andrew’s six keys of occlusion: Labio-
lingual crown inclination
• The Canines and premolars
– negative and similar.
• Maxillary first and second molars
– More negative than canines and premolars.

86. Andrew’s six keys of occlusion
• absence of
rotation

87. Andrew’s six keys of occlusion
• Tight contact

88. Andrew’s six keys of occlusion
• Curve of spee
– The depth of the curve of Spee ranges from a flat
plane to slightly concave surface.

89. Dentitional and occlusal changes in
young adults
3rd molar development
– Most variable in
calcification and eruption
– Role of 3rd molar in
crowding
– Simultaneous events
• Arch perimeter shortening
• Increased incisor crowding
• More Forward Mandibular
growth than maxilla

90. Conclusion
• Development of dentiton in human is complex
and depends on many variables .
• To determine an abnormal course of
development , it is the responsibility to an
orthodontist to have adequate knowlage on
the subject to differentiate abnormal from
normal before initiating therapy.