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
35.
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
42.
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. b. Curve of Wilson
c. c. Sphere of Monson
d. 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