This document discusses occlusion and its development from birth through adulthood. It begins by defining static and dynamic occlusion. It then discusses ideal, normal, and physiologic occlusion. It describes the periods of occlusal development from pre-dental through deciduous, mixed, and permanent dentition. It provides details on eruption sequences, spacing, and transitional periods. It also discusses occlusal curvatures like the Curve of Spee and Wilson. In summary, it provides a comprehensive overview of occlusion, its classifications, development through life stages, and related anatomical concepts.
2. INTRODUCTION
The term occlusion has both static and dynamic aspects
Static refers to form, alignment and articulation of teeth
within & between dental arches and relationship of teeth
to their supporting structures
It may be defined also as the contact relationship of the
teeth in function or parafunction
3. IDEAL OCCLUSION:
Pre-conceived theoretical concept of occlusal structural &
functional relationships that include idealized principles
and characteristics that an occlusion should be
NORMAL OCCLUSION:
It is class I relationship of maxillary & mandibular 1st
molars in centric occlusion
PHYSIOLOGIC OCCLUSION:
Occlusion that deviates in one or more ways from ideal
yet it is well adapted to that particular environment is
esthetic & shows no pathologic manifestations
4. FUNCTIONAL OCCLUSION:
An arrangement of teeth which will provide highest
efficiency during excursive movements of mandible which
is necessary during function
BALANCED OCCLUSION:
An occlusion in which balance & equal contacts are
maintained throughout entire arch during all excursions of
mandible
Others : Therapeutic occlusion, Traumatic Occlusion,
Centric Occlusion etc.
5. PERIODS OF OCCLUSAL DEVELOPMENT:
PRE-DENTAL PERIOD
DECIDUOUS DENTITION PERIOD
MIXED DENTITION PERIOD
PERMANENT DENTITION PERIOD
6. PRE-DENTAL PERIOD
The period after birth during which the neonate does not
have teeth
Lasts for 6 months
7. GUM PADS
Alveolar processes at the time of birth
Pink, firm and are covered by a dense layer of fibrous
periosteum
8. Horse-shoe shaped and developed in two parts
Labio-buccal portion & lingual portion
Two portions of gum pads are separated by dental
groove
9. Gum pad are divided into 10 segments by certain grooves
called transverse grooves
Each of these segment consist of developing deciduous
tooth sac
Gingival groove separate gum pads from palate & floor of
the mouth
10. Transverse groove between canine & and first deciduous
molar segment is called the lateral sulcus
Lateral sulci are useful in judging the inter-arch
relationship at a very early stage
The lateral sulcus of the mandibular arch is normally
more distal to that of the maxillary arch
Lateral sulcus
11. The upper and lower gum pads are almost similar to
each other
The upper gum pad is both wider as well as longer than
the mandibular gum pad
Thus when upper and lower gum pads are approximated,
there is a complete overjet all around
12. Contact occurs b/w upper & lower gum pads in first
molar region and a space exists between them in
anterior region
This infantile open bite is considered normal and it helps
in suckling
Infantile open bite for
suckling
13. Status of dentition
Neonate is without teeth for about 6 months of life
At birth gum pads are not sufficiently wide to
accommodate developing incisors, which are crowded in
their crypts
During 1st year of life gum pads grow rapidly permitting
incisors to erupt in good alignment
14. Teeth that are present at the time of birth are called natal
teeth.
Teeth that erupt during the first month of age are called
neonatal teeth.
The natal and neonatal teeth are mostly located in the
mandibular incisor region and show a familial tendency.
15. DECIDUOUS DENTITION PERIOD
Initiation of primary tooth buds occurs during first six
weeks of intra-uterine life
Primary teeth begin to erupt at age of about 6 months
Eruption time for primary teeth : 21/2 - 3 1/2 years
16. Eruption age and sequence of
deciduous dentition
A-B-D-C-E
6months – 3 Years
18. SPACING IN DECIDUOUS DENTITION
Spacing usually present b/w deciduous teeth & called
physiological spaces or developmental spaces
Spaces in primary dentition is important for normal
development of permanent dentition
19. Absence of spaces in primary dentition can cause
crowding (when the larger permanent teeth erupt)
Spacing invariably is seen mesial to maxillary canines &
distal to mandibular canines
20. These physiological spaces are called primate spaces or
simian spaces or anthropoid spaces as they are seen
commonly in primates
These spaces help in placement of the canine cusps of
the opposing arch
21. Flush terminal plane
Mesio-distal relation b/w distal surfaces of upper & lower
second deciduous molars is called the terminal plane
A normal feature of deciduous dentition is a flush terminal
plane where distal surfaces of upper & lower second
deciduous molars are in same vertical plane
22. Deep bite
A deep bite may occur in initial stages of development
Deep bite is accentuated by fact that deciduous incisors
are more upright than their successors
23. Lower incisal edges often contact cingulum area of
maxillary incisors
This deep bite is later reduced due to following factors:
a. Eruption of deciduous molars
b. Attrition of incisors
c.Forward movement of mandible due to growth
24. MIXED DENTITION PERIOD
Mixed dentition period begins at approximately 6 years of
age with eruption of 1st permanent molars
During mixed dentition period, deciduous teeth along with
some permanent teeth are present in oral cavity
25. Mixed dentition period classified into three phases:
1st transitional period
Inter-transitional period
2nd transitional period
26. 1st transitional period
Characterized by emergence of 1st permanent molars &
exchange of deciduous incisors with permanent incisors
1st permanent molar erupts at 6 yrs guided into dental arch
by distal surface of 2nd deciduous molar
27. Mesio-distal relation b/w distal surfaces of upper and
lower 2nd deciduous molars can be of three types:
1. FLUSH TERMINAL PLANE
2. DISTAL STEP
3. MESIAL STEP
28. Flush terminal plane
Distal surface of upper & lower 2nd deciduous molars are
in one vertical plane
Normal feature of deciduous dentition
Erupting 1st permanent molars may also be in a flush or
end on relationship
29. For transition of such an end on molar relation to a Class I
molar relation, lower molar has to move forward by about
3-5 mm relative to upper molar
Utilization of physiologic spaces & leeway space in
lower arch & by differential forward growth of mandible
Shift in lower molar from a flush terminal plane to a Class I
relation can occur in two ways - Early and Late shift
30. Early shift
Early shift occurs during early mixed dentition period
Eruptive force of 1st permanent molar is sufficient to push
deciduous 1st & 2nd molars forward in arch to close primate
space & establish a Class I molar relationship
Since this occurs early in mixed dentition period it is called
early shift
31. Late shift
Many children lack primate space & thus erupting
permanent molars are unable to move forward to establish
Class I relationship
In these cases, when deciduous second molars exfoliate
permanent 1st molars drift mesialy utilizing leeway space
This occurs in late mixed dentition period & is thus called
late shift
32. Mesial step terminal plane
Distal surface of lower second deciduous molar is more
mesial than that of upper
Permanent molars erupt directly into Angle's Class I
occlusion
Mesial step terminal plane most commonly occurs due to
early forward growth of mandible
33. If differential growth of mandible in a forward direction
persists, it can lead to Angle's Class III molar relation
If forward mandibular growth is minimal, it can establish a
Class I molar relationship
34. Distal step terminal plane
Distal surface of lower second deciduous molar being
more distal to that of the upper
Thus erupting permanent molars maybe in Angle's Class
II occlusion
36. Exchange of incisors:
During first transitional period deciduous incisors are
replaced by permanent incisors
Mandibular central incisors : 1st to erupt
Permanent incisors > deciduous incisors
37. This difference b/w amount of space needed for
accommodation of incisors & amount of space available
for this is called Incisal liability
Incisal liability (maxillary arch ) : about 7 mm
Incisal liability (mandibular arch ) : about 5 mm
38. The incisal liability is overcome by the following factors:
A. Utilization of interdental spaces seen in primary
dentition:
Physiologic or developmental spaces that exist in primary
dentition are utilized to partly account for
incisal liability
Permanent incisors are much more easily
accommodated in normal alignment in cases exhibiting
adequate inter-dental spaces than in an arch that has no
space
39. B. Increase in inter - canine width:
During transition from primary incisors to permanent
incisors, increase in inter-canine width of both maxillary &
mandibular arches takes place
This is an important factor that allows much larger
permanent incisors to be accommodated in arch
previously occupied by the deciduous incisors
40. C. Change in incisor inclination:
One of differences b/w deciduous & permanent incisors
is their inclination
Primary incisors are more upright than permanent
incisors
Since permanent incisors erupt more labially inclined,
they tend to increase dental arch perimeter
41. A. Primary incisors are more
upright in alignment than
permanent incisors
B. Permanent incisors are
more labialy inclined
43. Inter - transitional period
In this period the maxillary and mandibular arches consist
of sets of deciduous and permanent teeth.
Between permanent incisors and first permanent molars
are deciduous molars and canines.
This phase during the mixed dentition period is relatively
stable and no change occurs.
44. 2nd transitional period
2nd transitional period is characterized by replacement of
deciduous molars & canines by premolars & permanent
cuspids respectively
Combined mesio-distal width of permanent canines &
premolars is usually less than that of deciduous canines
and molars & this Surplus space is called leeway space
of Nance
45. Leeway space (mandibular arch) : about 3.4mm (1.7mm
on each side of the arch)
Leeway space (maxillary arch) : about 1.8mm (0.9 mm
on each side of the arch)
Excess space available after exchange of deciduous
molars & canines is utilized for mesial drift of mandibular
molars to establish Class I molar relation
46. Ugly duckling stage
Sometimes a transient or self correcting malocclusion is
seen in maxillary incisor region b/w 8-9 years of age
This is a particular situation seen during eruption of
permanent canines
47. As developing permanent canines erupt, they displace
roots of lateral incisors on to roots of central incisors,
which also get displaced mesialy
A resultant distal divergence of crowns of two central
incisors causes a midline spacing
48. Described by Broadbent ( hence also known as
Broadbent phenomenon) as ugly duckling stage as
children tend to look ugly during this phase of
development
This condition usually corrects by itself when canines
erupt & pressure is transferred from roots to coronal area
of incisors
49. PERMANENT DENTITION PERIOD
Permanent dentition forms within jaws soon after birth,
except for cusps of first permanent molars, which form
before birth
Permanent incisors develop lingual or palatal to deciduous
incisors and move labially as they erupt
Premolars develop below diverging roots of deciduous
molars
50. Eruption sequence of permanent dentition may exhibit
variation:
6-1-2-4-3-5-7 or 6-1-2-3-4-5-7
In mandibular arch sequence is:
6-1-2-3-4-5-7 or 6-1-2-4-3-5-7
51. Occlusal Curvatures & Axial Position
a. Curve of Spee
b. Curve of Wilson
c. Sphere of Monson
d. Axial position
52. Curve of Spee
The curvature which begins at the tip of canines & follows
buccal cusp tips of premolars & molars posteriorly, when
viewed from their facial aspect
Two dimensional and curves upward from anterior to
posterior
53. Inclination of some of individual posterior teeth must be
offset from vertical long axis of body, if their occlusal
surfaces are to conform to this curve
Maxillary molar roots are inclined mesialy & mandibular
molar roots distally
54. Curve of Wilson
Medio-lateral curvature of occlusal plane of posterior
teeth
Two dimensional, at right angle to Curve of Spee
Purpose of this arc in occlusal curvature is to
complement paths of condyles during movements of
mandible
55. Crowns of mandibular posterior teeth must incline to
lingual, while crowns of maxillary posterior teeth must
incline toward buccal
This curve becomes deeper posteriorly, so that molars
inclination is greater than that of premolars
Because of this curve & associated tooth inclinations,
buccal cusps of mandibular molars & lingual cusps of
maxillary molars usually appear to be longer
56. Sphere of Monson
Compensating Occlusal Curvature
Three dimensional curvature of the occlusal plane, which
is the combination of the Curve of Spee and the Curve of
Wilson
This curvature is in form of a portion of a ball, or sphere
This curvature is concave for mandibular arch & convex
for the maxillary arch
57. Axial Position
Inclination of a tooth from a vertical axis
Normally described in mesio-distal & facio-lingual directions
It is normally described in terms of root's inclination, which
means that crown is normally inclined in opposite direction
58. These inclinations are necessary for proper occlusal &
incisal function of teeth
As these axial positions are described, it should be of value
to relate them to individual tooth's functions, as well as its
inclination relative to Curves of Spee and Wilson