Development of occlusion

1. Development Of Occlusion

2. Introduction
 Occlusal development can be divided into the
following developmental periods:
 1.Dentition At Birth / Pre Dental Period
 2.Development of Primary Teeth /
The Deciduous Dentition Period (birth-2
1/2yrs)
 3.Mixed Dentition Period (6-12yrs)
 4.Permanent Dentition Period(12yrs onwards)

3. Pre Dental Period
 The features of
Predental period are:
 A> GUM PADS:
The alveolar arches
upper and lower at
the time of birth are
known as gum pads.

4.  Transverse groove
 Lateral sulcus
 Dental groove
 Gingival groove
 Lateral sulcus
 First molar contact area

5.  The labio-buccal portion is divided in ten segments
by transverse grooves each corresponding to a
deciduous tooth.
 The groove present b/w the canine and first
deciduous molar area is called the lateral sulcus.
 The lingual portion develops after the labio-buccal
portion and both are separated from each other by
the dental groove which is again limited by the
gingival groove on the lingual side.

6.  The gingival groove in the upper jaw separates the
gum pads from the palate.
 The dental groove runs laterally and gingivally to
contact the gingival groove in the region of canine and
later crosses across the region of first deciduous molar
distally and buccally.
 At rest these gum pads are separated by the tongue.
The upper gum pad is bigger than the lower gum pad
in such a way there is complete overjet all round the
upper to lower gum pads .

7.  Vertical space in the anterior region is present
which is occupied by the tongue
 At birth since gum pads are not wide enough to
accommodate their erupting incisors we find
crowding and rotations of these teeth which get
corrected as the arch expands
 The upper and lower gum pads occludes in the
area of future deciduous molars

8. Deciduous Dentition Period
Eruption Age And Sequence :
1. Lower centrals (6months)
2. Upper centrals (7months)
3. Lower laterals (8months)
4. Upper laterals (9months)
5. Lower first molar (12 months)
6. Upper first molar (14 months)
7. Lower canine (16 months)
8. Upper canine (18months)
9. Lower second molar (20 months)
10. Upper second molar (24 months)

9. DECIDUOS DENTITION
AGE IN MONTHS
A B C D E
A B C D E
E D C B A
E D C B A
7 9 18 14 24
6 8 16 12 20

10. Salient features of primary dentition:
 1. Spacing of Incisor Teeth
 2. Primate Space /Simion / Anthropoid
Space
 3. Deep Bite
 4. Flush Terminal Plane
 5. Reduction in the over jet gradually
because of the forward growth of the
mandible - Early change
 6. Reduction in the overbite as permanent
teeth erupt – Later change

11. 1. Spacing in Incisor Teeth
 Spacing is normal
throughout the primary
dentition this generalize
spacing of the primary
teeth is requirement for
the proper alignment of
the permanent teeth

12. Primate Space or Simien Space or Anthropoid Space
Present between:
 Upper arch – b/w lateral incisor and
canine
 Lower arch – b/w canine and first
deciduous molar
 In the lower arch space is utilized
during the eruption of posterior teeth
 However,in the upper arch since this
space is present mesial to the
canine, it doesn’t really give an
opportunity for the canine to move
distally. The upper canine
interdigilate into this space during
eruption.

13. Leeway Space Of Nance
( Not a feature of primary dentition)
 In contrast to the anterior teeth, the
premolars are smaller than the molars.
 According to Profitt:
 1. upper first deciduous molar is almost the
same size as that of upper first premolar
 2. Lower first deciduous molar is 0.5mm
larger than lower first premolar
 3. upper second deciduous molar bigger
than upper second premolar by 1.5mm
 4. Lower deciduous molar is bigger than
lower second premolar by 2mm

14.  In other words, the combined mesio-distal width of ‘CDE’ is
greater than the mesio-distal width of ‘345’ in both the dental
arches.
 Upper arch = 0.9mm per quadrant
 Lower arch = 1.7mm per quadrant
 The leeway space helps not only in providing adequate space
for eruption of permanent teeth but also helps in changing
END-ON TO CLASS1 MOLAR RELATIONSHIP

16.  Differential growth of the mandible is also
an important contributor to molar
transition. If a child has a flush terminal
plane (end-on) early in the mixed
dentition about (3.5mm) of movement of
molar is required to move it to a class 1
molar relation
 Half the distance is contributed by the
differential growth of the mandible. The
other half by utilization of LEEWAY SPACE
of NANCE

17. NATAL TEETH:
 Are teeth present at birth normally teeth
erupt after 6month.
 These can be
 1. Supernumery teeth
 2. Otherwise a normal central incisor
 Because of a possibility that they could be
perfectly normal, such a natal tooth
should not be extracted casually.

18. HOLLYWOOD SMILE:
 The primary dentition has generalized
spacing in both the arches.
 Primary dentition with no spaces b/w the
primary incisors resulting in a good
appearance of the child’s smile due to lack
of spacing is termed as
“HOLLYWOOD SMILE”
This guarantees insufficient room for the
permanent incisors which results in crowding.

20. MIXED DENTITION PERIOD:
 Period b/w 6years – 12 years
Salient features of mixed dentition are:
 1. Ugly duckling stage
 2. Incisors liability
 3. leeway space of Nance
 4. Molar relation
 5. Correction of existing deep-bite.

21. Ugly ducking stage
 During the mixed dentition period there is a space seen b/w the
central incisors and the lateral incisor crowns are flared distally
with spacing which is a transient malocclusion and does not
required any orthodontic intervention
 Its an ugly arrangement of anterior teeth. There the developing
permanent canine (upper) causes mesial displacement of the
permanent incisors causing distal divergence of the crowns of
the same in incisors.
 But as the canine erupt, the same pressure exerted on the
roots is transferred onto the crowns and the malocclusion gets
self corrected. Hence it is also called “SELF CORRECTING
ANOMOLY”

22. Ugly ducking stage

23. INCISOR LIABILITY
 The permanent teeth are considerably larger than the deciduous incisors the
difference b/w the space needed for the incisors and the amount of space
available is called “INCISAL LIABILITY”
 Hence the anteriors inspite of decreased amount of space, still aligns
themselves by means of
 1. Utilization of spaces present b/w anterior teeth (primary dentition)
 2. Increased width of the arch (intercanine width)
 3. Labial positioning of centrals and laterals as they erupt.
 4. Distal shifting of permanent canines after exfoliation of first
deciduous molars. (not always)

24. ACCORDING TO WARREN MAYNE:
 Incisor liability in upper : 7.5mm
 Incisor liability in lower : 6mm
 Spacing : Upper - 4mm
 Lower – 3mm
 Inter canine width : Upper -2mm
 Lower -1.5mm
 Labial eruption of incisors : Upper -1-
2mm

25. PRESENCE OF DEEP BITE
 During mixed dentition phase presence of deep
bite is considered to be normal (TRANSIENT
MALOCCLUSION)
 As the mandible grows, it grows horizontally and
vertically. When it grows vertically, the teeth
that are in function erupt at a rate that parallels
the rate of growth of the mandibular ramus.
Thus the deep bite gets corrected slowly.

26. MOLAR RELATION:

27. PERMANENT DENTITION PERIOD
12 years onwards

28. PERMANENT DENTITION
AGE IN YEARS
1 2 3 4 5 6 7 8
1 2 3 4 5 6 7 8
6-7 7-8 9-10 10-12 11-12 6-61/2 12-15 18-21
7-8 8-9 11-12 10-11 10-12 6-61/2 12-15 18-21

29. 1. Pre emergent eruption
2. Post emergent eruption
 a) Post emergent spurt
 b) Juvenile occlusal equilibrium
 c) Adult occlusal equilibrium

30. PRE-EMERGENT ERUPTION:
 Erupting movement begins soon after the root
begins to form. But, during the crown formation
there is a very slow labial or buccal drift of
teeth.
 This phase of eruption of the tooth within the
bone before emerging into the oral cavity is
termed as “Pre-emergent Eruption.”
 Failure of eruption of teeth due to failure of
bone resorption is seen is CLEIDOCRANIAL
DYSPLAISA

31. POST-EMERGENT ERUPTION
 Once the tooth erupts into the oral cavity, it erupts
rapidly until it reaches the occlusal level after which it
is subjected to force of mastication. At this point, its
eruption slows down and then as it reaches the
occlusal level of other teeth and is in complete
function, the eruption all but HALTS.
 The phase of rapid eruption after eruption into the
oral cavity (GINGIVA) till it reaches the occlusal level
is termed as “ Post Emergent Spurt”

32.  The next phase of slow eruption after reaching the
occlusal level is termed as JUVENILE OCCLUSAL
EQUILIBRIUM
 It is observed that eruption occurs mostly in night
 During juvenile equilibrium phase, the eruption rate
parallels the amount of vertical growth of mandible.
 When the pubertal growth spurt ends, a final phase
of eruption occurs called the ADULT OCCLUSAL
EQUALIBRIUM. However they erupt very slowly.
But if its antagonist tooth is lost at any age, again
the opposite tooth can erupt rapidly.