stage of the development of the occlusion

1. DEVELOPMENT OF OCCLUSION
MOHAMED A. IBRAHIM

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

17. ERUPTION SEQUENCE

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. 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

59. AXIAL POSITIONS OF TEETH

63. REFERENCES
• CONCISE DENTAL ANATOMY & MORPHOLOGY : JAMES L FULLER
• DENTAL ANATOMY, PHYSIOLOGY & OCCLUSION: WHEELER’S
• TEXTBOOK OF DENTAL ANATOMY, PHYSIOLOGY & OCCLUSION: RASHMI GS
(PHULARI)
• MOYERS RE: HANDBOOK OF ORTHODONTICS
• ORTHODONTICS - THE ART & SCIENCE : S.I. BHALAJHI
• INTERNET

64. Thank you