This document discusses the development of teeth from pre-natal to mixed dentition stages. It begins with the formation of dental lamina and enamel organs that give rise to deciduous teeth. The stages of tooth development from bud to bell stage are described. It then discusses the sequence of eruption of primary teeth and the characteristics of primary dentition including spacing, overjet, overbite and molar relationships. The mixed dentition period is divided into transitional phases with a focus on early and late shift occurring due to eruption of permanent molars and loss of deciduous teeth. Concepts such as leeway space and secondary spacing are also introduced.

1. By:
Pratik yadav
MDS 1st yr
Dept of orthodontics

2. INTRODUCTION
 The development of dentition is an important
part of craniofacial growth as the formation,
eruption, exfoliation and exchange of teeth
take place during this period. This helps in
assimilation of facts, predictions of teeth
eruption , the factors influencing them and
implicate clinically for treatment .

3. PRE-NATAL DEVELOPMENTOF
TEETH
 The embryonic oral cavity is lined by stratified
squamous epithelium known as the oral ectoderm
 Around the 6th week of intra uterine life, the infero-
lateral border of maxillary arch and supero- lateral
border of mandibular arch shows localised
proliferation of oral ectoderm resulting in the
formation of a horse-shoe shaped band of tissue
called dental lamina
 Dental lamina plays a important role in the
development of dentition

5.  In certain areas the dental lamina proliferate
and forms knob like structure that grows into
underlying mesenchyma.
 Each knob represents a future deciduous
tooth and is called enamel organ
 Enamel organ passes through a number of
stages ultimately forming the teeth
 Based on shape of the enamel organ develops
can be divided into,
 Bud stage
 Cap stage
 Bell stage

6. BUD STAGE
Differentiation of dental lamina leads to formation of round,
ovoid swelling at 10 different points corresponding to future
position of deciduous teeth. These are the primordia of
enamel organ.
Enamel organ consists of peripherally located low columnar
cells and centrally located polygonal cells.
Dental papilla : It is the area of ectomesenchymal
condensation subjacent to enamel organ. Cells of dental
papilla will form tooth pulp & dentine.
Dental sac: It is area of ectomesenchymal condensation
surrounding the tooth bud & dental papilla. Cells of dental
sac will form cementum & periodontal ligament.

9. Bud
Stage

10. CAP STAGE :
 Characterized by a shallow invagination of deep surface
of a bud.
 Cuboidal cells cover the convexity of the cap
outer enamel epithelium.
 Columnar cells cover the concavity of the cap
Inner enamel epithelium.
 Stellate Reticulum:
 Polygonal cells begin to separate as more
intercellular fluid is produced and forms cellular network
called stellate reticulum.
 Enamel Knot:
 Cells in center of the enamel organ are densely packed.
This knot projects towards underlying dental papilla .
Vertical extension of enamel knot forms enamel cord.
Both the structures disappear before enamel formation
begins.

11. Cap Stage of
Tooth
Development
Dental (enamel) organ
Dental papilla
Dental follicle
©Copyright 2007, Thomas G. Hollinger, Gainesville, Fl

12. BELL STAGE :
1. The cell of inner enamel epithelium differentiate into tall
columnar tissue called ameloblast
2. A few layers of flat squamous cells are seen between stelate
reticulum and inner enamel epithelim this layer is called stratum
intermedium
3. Stellate reticulum expands due to accumulation of intra cellular
fluid , they r star shaped & as the enamel formation stars it
collapse to a narrow zone thereby reducing the distance between
inner & outer enamel epithelium
4. Before inner enamel epithelium begins to produce enamel, the
peripheral cells of the dental papilla differentiate into odontoblast

14. FORMATION OF ROOT
Root start forming after dentin formation has
reached future cementoenamel junction. Both dental organ
and dental papilla play part in formation of root.
Hertwig's epithelial root sheath :
* The outer and inner dental epithelium meets one
another at future cervical area and is called
cervical loop.
* This cervical loop forms epithelial sheath of
Hertwig, which moulds the shape of the root and
initiates dentin formation.

15.  The root sheath consists of only outer and inner dental
epithelium.
 The inner layer of cells remains short and do not produce
enamel. These cells induce the differentiation of cell of dental
papilla into Odontoblasts, which lay a layer of dentin. At the same
time the continuity of Hertwig's sheath is destroyed due to
infiltration of connective tissue and the root sheath breaks up into
small strands of epithelium called epithelial rests of Molassez.
 While the coronal part of the sheath degenerates, the apical part
continues to grow in length and aid in lengthening of root.

16. Term occlusion is derived from the Latin word,
“occlusio”; defined as the relationship between
all the components of the masticatory system
in normal function, dysfunction and
parafunction.
An ideal occlusion is the perfect interdigitation
of the upper and lower teeth, which is a result
of developmental process consisting of the
three main events, jaw growth, tooth formation
and eruption

17. Evolution
To develop a functional occlusion it became
necessary for the teeth and bones to develop
synchronously. Over a period of time there was loss
or fusion of cranial and facial bones, the number of
bones have reduced and the dental formula has also
undergone changes.

18. Periods of Occlusal Development
Occlusal development can be divided into the following
development periods:
o Neo-natal period.
o Primary dentition period.
o Mixed dentition period.
o Permanent dentition period.

19. Neonatal Period
(lasts upto 6 months after birth)

20. Gum Pads
• Alveolar processes at the time of birth- gum pads.
• Pink in colour, firm and are covered by a dense layer of fibrous
periosteum.

21. Gum Pads contd…
• The gum pad soon gets segmented by
a groove called transverse groove, &
each segment is a developing tooth site.
•The pads get divided into ‘labio-
buccal’ & ‘lingual portion’, by a dental
groove.
• The groove between the canine and
the 1st molar region is called the lateral
sulcus, useful for judging the inter
arch relationship at a very early stage.

22. Gum Pads contd…
The upper gum pad is horse shoe
shaped & shows:
o Gingival groove: separates
gum pad from the palate.
o Dental groove: starts at the
incisive papilla, extends
backward to touch the
gingival groove in the
canine region & then
moves laterally to end in
the molar region.
o Lateral sulcus.

23. Gum Pads contd…
The lower gum pad is ‘U’
shaped and rectangular,
characterized by:
o Gingival groove: lingual
extension of the gum
pads.
o Dental groove.
o Lateral sulcus.

24. Relationship of Gum Pads
o Anterior open bite is seen at rest with
contact only at the molar region.
o Complete overjet.
o Class II pattern with maxillary gum
pad being more prominent.
o Mandible is distal to the maxilla of 2.7
mm- male and 2.5- female. ( Sillman JH
1938)
oThe range of variation of this distal
relationship is from 0 to 7 mm. .
( Sillman JH 1938)

25. Relationship of Gum Pads
o Mandibular lateral sulci lies
posterior to maxillary lateral sulci.
o Mandibular functional movements
are mainly vertical, and to a little
extent antero-posterior. Lateral
movements are absent.

26. A ‘precise bite’ or jaw
relationship is not yet seen.
Therefore, neonatal jaw
relationship cannot be used as
a diagnostic criterion for
reliable prediction of
subsequent occlusion in the
primary dentition.

27. Status of Dentition at Birth

28. Precociously Erupted Primary
Teeth
Natal tooth Neonatal teeth
Pre-erupted teeth’ or ‘Early Infansive teeth’ are teeth that
erupt during the 2nd or 3rd month.

29. Natal/neonatal teeth
 Classification
Hebling (1997) classified natal teeth into 4 clinical categories:
1. Shell-shaped crown poorly fixed to the alveolus by gingival
tissue and absence of a root;
2. Solid crown poorly fixed to the alveolus by gingival tissue
and little or no root;
3. Eruption of the incisal margin of the crown through gingival
tissue
4. Edema of gingival tissue with an unerupted but palpable
tooth.

30.  Gender
 Predilection for females
 Kates et al (1984) reported a 66% proportion for females
against a 31% proportion for males.
 Etiology
It has been related to several factors, such as:-
 Superficial position of the germ
 Infection or malnutrition
 Eruption accelerated by febrile incidents or hormonal
stimulation,
 Hereditary transmission of a dominant autosomal gene
 hypovitaminosis

31. Natal/neonatal teeth
 Complications
 Interfere with feeding
 Risk of aspiration
 Traumatic injury to the baby’s tongue
and/or to the maternal breast
 Riga-Fede disease- oral condition
found, rarely in newborns manifests
as an ulceration on the ventral surface
of the tongue or on the inner surface
of the lower lip. Caused by trauma to
the soft tissue from erupted baby
teeth.
Riga-Fede disease

32.  Diagnosis
 A radiographic verification of the relationship
between a natal and/or neonatal tooth and
adjacent structures, nearby teeth, and the
presence or absence of a germ in the primary
tooth area would determine whether or not the
tooth belongs to the normal dentition ( Almeida
CM et al 1997)
 Most natal and neonatal teeth are primary teeth
of the normal dentition and are not
supernumerary teeth ( Brandt Sk et al 1983)
 Correspond to teeth of the normal primary
dentition in 95% of cases, while 5% are
supernumerary (Hawkins C 1932)

33.  Treatment
 If the erupted tooth is diagnosed as a tooth of the normal
dentition -- maintenance of these teeth in the mouth is the first
treatment option, unless this would cause injury to the baby
(Chow MH 1980, Roberts MW 1992)
 When well implanted-- these teeth should be left in the arch
and their removal should be indicated only when they interfere
with feeding or when they are highly mobile, with the risk of
aspiration (Toledo AO 1996)
 Reasons for removal -- The risk of dislocation and consequent
aspiration, traumatic injury to the baby’s tongue and/or to the
maternal breast, (Kates GA et al 1984)

34.  Martins et al (1998) suggested smoothing of the incisal
margin to prevent wounding of the maternal breast during
breast feeding.
 If the treatment option is extraction, certain precautions should
be taken :
 Avoiding extraction up to the 10th day of life to prevent
hemorrhage
 Assessing the need to administer vitamin K before extraction
(0.5-1.0 mg IM)
 Considering the general health condition of the baby
 Avoiding unnecessary injury to the gingiva
 Being alert to the risk of aspiration during removal.

35. (From around the 6th month to 6 years)

36. Sequence of Eruption

37. Primary
(upper)
First evidence of
calcification
(Weeks in utero)
Crown
completed
(months)
Eruption
(months)
Root
completed
(years)
Central 14 (13-16) 11/2 10 11/2
Lateral 16 21/2 11 2
Canine 17 9 19 31/4
1st molar 151/2 6 16 21/2
2nd molar 19 11 29 3
Chronology of Primary Dentition
Wheelers…

38. Primary
(Lower
First evidence of
calcification
(Weeks in utero)
Crown
completed
(months)
Eruption
(months)
Root
completed
(years)
Central 14 (13-16) 21/2 8(6-10) 11/2
Lateral 16 3 13( 10-16) 11/2
Canine 17 9 20(17-23) 31/4
1st molar 151/2 51/2 16( 14-18) 21/4
2nd molar 18 10 27 3
Wheelers…

39. Status of Dentition
(during primary dentition period)

40. At around 5 – 6 Years
There are 48 teeth/parts of teeth present in the jaw. It is at this
time that there are more teeth in the jaws than at any other time.

41. Features Of Primary
Dentition
• Spacing- 2 types of dentition are seen:
•A) Spaced dentition - usually seen in the
deciduous dentition to accommodate the
larger permanent teeth in the jaws.
• More prominent in the anterior region,
and are called ‘physiological spacing’ or
‘developmental spacing’.
• Absence of spaces in the primary
dentition is an indication that crowding of
teeth may occur when the larger
permanent teeth erupt.

42. Features Of Primary
Dentition contd…
• Most subhuman primates
have it through out life and use
it for interdigitation of the
opposing canines. This space is
used for early mesial shift.
primate spaces’, ‘simian spaces’ or
‘anthropoid spaces’.

43. Features Of Primary
Dentition contd…
Shallow overjet & overbite. Initially a deep bite may occur due to the fact that
the deciduous incisors are more upright than their successors. The lower incisal
edges often contact the cingulum area of the maxillary incisors. This deep bite
is later reduced by:
oEruption of deciduous molars.
oAttrition of incisors.
oForward movement of the mandible due to growth.

44. Features Of Primary
Dentition contd…
Almost vertical
inclination of anteriors.

45. Features Of Primary
Dentition contd…
Ovoid arch form.

46. Molar Relationship
The molar relationship in the primary dentition can be classified
into 3 types:
oStraight/flush terminal plane.
oMesial step.
oDistal step.

47. Flush Terminal Plane
• If the distal surface of
maxillary and mandibular
deciduous second molars are in
the same vertical plane; then it
is called a flush terminal plane
• Normal molar relationship in
the primary dentition, because
the mesiodistal width of the
mandibular molar is greater
than the mesiodistal width of
the maxillary molar.

48. Mesial Step
Distal surface of mandibular
deciduous second molar is
mesial to the distal surface of
maxillary deciduous second
molar.

49. Distal Step
Distal surface of mandibular
second deciduous molar is
more distal to the distal surface
of the maxillary second
deciduous molar

51. Mixed Dentition Period
(Around 6 years- 12 years)
The mixed dentition period can be divided into three
phases:
o First transitional period.
o Inter-transitional period.
o Second transitional period.

52. First Transitional Period

53. Eruption of 1st Permanent Molar
The location & relation of the 1st permanent molar depends much
upon the distal surface of the upper & lower 2nd deciduous molar.

54. Transition to Class I Molar
Relation

55. Early Shift
• Early shift occurs during the early mixed dentition period.
• Since this occurs early in the mixed dentition, it is called early shift , the
eruptive force of first permanent molar push the deciduous 1st & 2nd
deciduous molar to close the primate space .

56. Late Shift
This occurs in the late mixed
dentition period when the
second deciduous molar
exfoliate the first permanent
molar drift mesialy & use
leeway space and is thus called
late shift.

57. Leeway Space of Nance
• Described by Nance in 1947
Maxilla: 0.9 mm/segment = 1.8 mm.
Mandible: 1.7 mm/segment = 3.4mm.

58. Secondary spacing
• Term was coined by Baume
• Observed in closed primary dentition
• Secondary spacing can also occur
during the eruption of permanent
central incisors

59. Distal Step
When the deciduous second
molars are in a distal step, the
permanent first molar will
erupt into a class II relation.
This molar configuration is not
self correcting and will cause a
class II malocclusion despite
Leeway space and differential
growth.

60. Mesial Step
Primary second molars in
mesial step relationship lead to
a class I molar relation in
mixed dentition. This may
remain or progress to a half or
full cusp class III with
continued mandibular growth.

61. Exchange of Incisors

62. Transition of Incisors
The incisal liability is over come by the
following factors:
Interdental physiological spacing in the primary incisor region.
(4 mm in maxillary arch & 3 mm in mandibular arch)

63. Transition of Incisors contd…
Increase in inter-canine arch width:
Significant amount of growth occurs with the eruption of
incisors and canines.

64. Transition of Incisors contd…
Increase in anterior length of the dental arches:
Permanent incisors erupt labial to the primary incisors to obtain
an added space of around 2-3 mm.

65. Transition of Incisors contd…
Change in inclination of
permanent incisors:
Primary teeth are upright but
permanent teeth incline to the
labial surface, thus decreasing
the inter-incisal angle from
about 151 degrees in the
deciduous dentition to 124
degrees in the permanent
dentition. This increases the
arch parameter.

66. Inter-Transitional Period

67. Inter-Transitional Period contd…
Root formation of emerged
incisors, and molars
continues, along with
concomitant increase in
alveolar process height.

68. Inter-Transitional Period contd…
Resorption of roots of
deciduous canines and
molars.

69. Second Transitional Period

70. Ugly Duckling Stage
(Broadbent’s phenomenon)
Around the age of 8 - 9 years, a
midline diastema is commonly
seen in the upper arch, which is
usually misinterpreted by the
parents as a malocclusion.
Its typical features are:
oFlaring of the lateral incisors.
oMaxillary midline diastema.

71. Ugly Duckling Stage contd…
Crowns of canines on young
jaws impinge on developing
lateral incisor roots, thus
driving the roots medially and
causing the crowns to flare
laterally.

72. Ugly Duckling Stage contd…
The roots of the central incisors are also forced
together, thus causing a maxillary midline diastema.

73. Ugly Duckling Stage contd…
With the eruption of the
canines, the impingement from
the roots shift incisally thus
driving the incisor crowns
medially, resulting in closure
of the diastema as well as the
correction of the flared lateral
incisors.

74. Ugly Duckling Stage contd…
Hence this unaesthetic metamorphosis, eventually leads to an
aesthetic result.

75. Self correcting anomalies

76. Sequence of Eruption
The canines in the upper arch erupt only after the premolars
have replaced the deciduous molars, whereas the canine erupt
before the premolars in the lower arch.

77. Second Transitional Period contd…

78. Second Transitional Period contd…
Eruption of permanent second molars
 Before emergence- second molars, oriented in a mesial &
lingual direction
 Teeth- formed palatally, guided into occlusion by Cone
Funnel mechanism , upper palatal cusps (cone) slides into the
lower occlusal fossa (funnel)
 Arch length is reduced by mesial eruptive forces
 Thereby, crowding if present is accentuated

80. The Permanent Dentition
This period is marked by the
eruption of the four permanent
second molars.

81. The Permanent Dentition contd…
Calcification begins at birth
with the calcification of the
cusps of the first permanent
molar and extends as late as the
25th year of life. Complete
calcification of incisor crowns
take place by 4 – 5 years and of
the other permanent teeth by
6 – 8 years except for third
molars.

82. Permanent
(Upper)
First evidence
of calcification
( weeks in
utero)
Crown
completed
(months)
Eruption
( months)
Root
completed
(years)
Central 3-4 mo 4-5 yr 7-8 yr 10
Lateral 10-12 mo 4-5 yr 8-9 yr 11
Canine 4-5 mo 6-7 yr 11-12 yr 13-15
1st premolar 11/2-13/4 yr 5-6 yr 10-11 yr 12-13
2nd premolar 2-21/4 yr 6-7 yr 10-12 yr 12-14
1st molar At birth 21/3-3 yr 6-7 yr 9-10
2nd molar 21/3-3 yr 7-8 yr 12-13 yr 14-16
3rd molar 7-9 yr 12-16 yr 17-21 yr 18-25
Chronology of Permanent Dentition
Wheelers…

83. Permanent
(Lower)
First evidence of
calcification
( weeks in utero)
Crown
completed
(months)
Eruption
( months)
Root completed
( years)
Central 3-4 mo 4-5 yr 6-7 yr 9
Lateral 3-4 mo 4-5 yr 7-8 yr 10
Canine 4- 5 mo 6-7 yr 9-10 yr 12-14
1st premolar 13/4-2yr 5-6 yr 10-12 yr 12-13
2nd premolar 21/4-21/2 yr 6-7 yr 11-12 yr 13-14
1st molar At birth 21/2-3yr 6-7 yr 9-10
2nd molar 21/2-3yr 7-8 yr 11-13 yr 14-15
3rd molar 8-10 yr 12-16 yr 17-21 yr 18-25
Wheelers…

84. The Permanent Dentition contd…
The permanent incisors
develop lingual to the
deciduous incisors and move
labially as they erupt.

85. The Permanent Dentition contd…
The premolars develop below
the diverging roots of the
deciduous molars.

86. The Permanent Dentition contd…
At approximately 13
years of age all
permanent teeth
except third molars
are fully erupted.

87. Features of Permanent
Dentition
Coinciding midline. Class I molar relationship.

88. Features of Permanent
Dentition contd…
Vertical overbite of about
one third the clinical
crown height of the
mandibular central
incisors. Overjet and over
bite decreases throughout
the second decade of life
due to greater forward
growth of the mandible.

89. Andrews keys to normal
occlusion
 Key I – Molar relationship
MB cusp of the max 1st molar falls
into the mesiobuccal groove of the
mand 1st molar and that the distal
surface of the DB cusp of the upper
first permanent molar should make
contact and occlude with mesial
surface of the MB cusp of the lower
second molar.

90. Andrews keys to normal
occlusion
Key II Crown angulation (Tip)
 The angulation of the facial axis of
every clinical crown should be
positive
 The gingival portion of the long axis
of the all crowns must be distal than
the incisal portion.

91. Andrews keys to normal
occlusion
Key III Crown inclination
 In upper incisors, the gingival
portion of the crown’s labial surface
is lingual to the incisal portion.

92. Andrews keys to normal
occlusion
Key IV – Rotations
 The fourth key to normal
occlusion is that the teeth should
be free of undesirable rotations.

93. Andrews keys to normal
occlusion
Key V – Tight contacts
 contact points should be tight
(no spaces).
 In absence of abnormalities
such as genuine tooth size
discrepancies, contact point
should be tight.

94. Andrews keys to normal
occlusion
Key VI – Occlusal plane or curve
of spee
 The curve of Spee should have no
more than a slight arch.
 Intercuspation of teeth is best
when the plane of occlusion is
relatively flat.
 A deep curve of spee results in a
more contained area for the upper
teeth, making normal occlusion
impossible.

95. Andrews keys to normal
occlusion
Key VII – Correct tooth size or the bolton’s ratio
 Bennett and McLaughlin in 1993 gave seventh key
to normal occlusion. i.e. the upper and lower tooth
size should be correct.