development of tooth, tooth eruption, shedding, clinical considerations.

1. TOOTH ERUPTION AND
SHEDDING
DR. BHARTI SACHDEVA
M.D.S. 1ST YR

2. CONTENTS
 Introduction
 Dental lamina
 Vestibular lamina
 Developmental stages
 Tooth eruption
 Pre eruption phase
 Eruption phase
 Theories of eruption
 Post eruption phase
 Chronology of human dentition
 Shedding of teeth
 Clinical considerations
 Bibliography

3. During the development of embryo, there is formation of
three germ layers – a)Ectoderm
b)Endoderm
c)Mesoderm
At 6th week of I.U.L. – horseshoe shape – primary epithelial
band
At 7th week of I.U.L. – dental lamina & vestibular lamina
All deciduous teeth arises from dental lamina , later
permanent successors arise from its lingual extension &
permanent molars from its distal extension.

8.  It serves as primordium for ectodermal portion of
deciduous teeth.
 Later during development of jaws , permanent
molars arise directly from distal extension of dental
lamina.
 The successors of deciduous teeth develop from
lingual extension of free end of dental lamina
opposite to enamel organ of each deciduous teeth.
 The lingual extension of dental lamina is named
successional lamina & develops from 5th month in
utero (permanent central incisor )to 10th month of
age (second premolar).

16. EARLY BELL STAGE

19. ERUPTION
ERUPTION

20. ERUPTION / EMERGENCE OF TEETH
Maurya Massler & Schour (1941) –
eruption as process whereby forming
tooth migrates from its intraosseous
location in the jaw to its functional
position within the oral cavity.
“eruption” denote tooth emerging through the
gingiva

22. PRE-ERUPTIVE PHASE
 Includes movement of developing tooth germs within
alveolar process
 Growing tooth moves in two directions to maintain its
position in expanding jaws viz. bodily movement &
eccentric movement
 Bodily movement –which occurs continuously as jaw
grows ,is a movement of entire tooth germ.
 This causes bone resorption in
direction of tooth movement
and bone apposition behind it

23.  Ecentric growth- growth in one part of tooth while rest of
remains constant .
 For example- root elongates ,yet crown does not increase
in size the crown maintains a constant relationship to
surrounding alveolar bone while increase in alveolar
height compensates for root growth.
 Successional permanent teeth develop lingual & near to
occlusal level of their primary predecessor.
 But at the end of this phase , teeth positioned lingually &
near apical third of primary teeth.

24.  Tooth germs grow rapidly
crowding
relieved by lengthing of jaw
tooth germ move outward & upward
This change occurs mainly due to eruption of primary
teeth & increase in height of supporting tissues.

25.  Anatomic Stages of tooth eruption – NOYES
& SCHOUR
Roots begin their formation as a result of
proliferation of both epithelial root sheath &
mesenchymal tissue of dental pappila & dental
follicle
The erupting tooth moves through bone of crypt
& connective tissue of oral mucosa

26. REE of crown proliferates & forms a thin attachment
with oral epithelium
Crown erupts further & lateral border of oral mucosa
now becomes DEJ
Tip of crown enters oral cavity by degenerating
membrane & breaking through center of double–
layered epithelium
REE now surrounding like a cuff , becomes known as
junctionl or attachment epithelium

27. Erupting tooth continues to move occlusally as
result of active eruption , exposing more of
clinical crown
Separation of attachment epithelium from crown &
resulting apical shift of attachment epithelium

28.  Alteration of connective tissue of dental follicle to
form pathway initiates by root formation & ends by
occlusal contact.
 Eruption pathway appears as a decreased &
degenerated connective tissue fibers, cells, blood
vessels & terminal nerves . These changes are
due to loss of blood supply & release of enzymes
that aid in degradation of these tissues.
Eruptive phase / pre-functional
eruptive phase-
Initiates by root formation & ends by occlusal contact.

34. POST ERUPTIVE PHASE
Movements made by the tooth after it has reached its functional
position in the occlusal plane.
They may be divided in three categories:
Accomodation for
growth
Compensation for
occlusal wear
Accomodation for
interproximal wear

35. ACCOMMODATION FOR GROWTH - Mostly occurs between
14 and 18 years by formation of new bone at the alveolar crest and
base of socket to keep pace with increasing height of jaws.
COMPENSATION FOR OCCLUSAL WEAR - Compensation
primarily occurs by continuous deposition of cementum around the
apex of the tooth. However, this deposition occurs only after tooth
moves.
ACCOMMODATION FOR INTERPROXIMAL WEAR -
Compensated by mesial or approximal drift.

36. FACTORS CONTROLLING MESIAL DRIFT:
(a) Contraction of the transseptal fibers: As the proximal tooth
surfaces of adjacent teeth become worn from functional
tooth movement, the transseptal fibers of the periodontal
ligament become shorter (due to contraction) and thereby
maintain tooth contact .
(b) Adaptability of bone tissue: The side of pressure on PDL
fibers causes bone resorption, whereas pull on the fibers
causes bone apposition. Therefore, as the contact areas of
the crowns wear, the teeth tend to move mesially, thereby
maintaining the contact.

37. (c) Anterior compartment of occlusal force: An anteriorly
directed force is generated when teeth are clenched, due
to the mesial inclination of most teeth and the forward-
directed force generated from inter-cuspal forces.
Eliminating opposing teeth results in elimination of
biting forces, causing a slowing down of the mesial
migration
(d) Pressure from soft tissues: Buccal mucosa and tongue
push teeth mesially

38. THEORIES OF TOOTH ERUPTION
Root elongation theory ( hammock ligament
theory )(TOMES 1872)
Bone remodelling theory(BRASH 1928)
Periodontal ligament contraction theory
(THOMAS 1967)
Vascular pressure theory
Pulp constriction theory(V.KORFF 1935)
Dental follicle theory (MARKS & CAHILL 1984)
Growth of periodontal tissues
Pressure from muscular action
Resorption of alveolar crest
Hormonal theory
Cellular proliferation theory

49.  PTHrp osteoblast activation
RANKL (ODF)
RANK
Osteoclast formation signal transduction

62. Alveolar bone growth: HERMAN believed that the growth
of the alveolar bone might push or squeeze the tooth out
of its alveolar and into the oral cavity. However, X-ray and
histological section show that the bone does not actually
touch the tooth, In addition, this mechanism can operate
only upon single conical roots but not on multi rooted
teeth.

63. Pressure from muscular action
Berten suggested that action of musculature of
cheeks & lips upon alveolar process might serve to
squeeze crown of tooth out into oral cavity like a
pumpkin seed from between fingers.
This process continuous until the teeth is in
occlusion.

64.  Resorption of alveolar crest – serve to expose
crown of tooth into oral cavity. This theory is not
tenable since histological examination shows that
alveolar crest is the site of most rapid & continous
growth of bone.
 Hormonal theory – Arthur Keith suggested that
hormones secreted by thyroids & pituitary glands
might govern eruption of teeth .
 This theory does not explain mechanism of eruption
of teeth & only points out fact that hormones may
affect eruption of teeth.

65.  Foreign body theory – states that calcified body
such as tooth tends to be exfoliated by tissue just as
does any foreign body.
 Cellular proliferation theory – Noyes point out that
tremendous pressure ,which is evolved from cellular
proliferation, provides growing plant with sufficient
force to break through hard obstacles. Similarly
,osmotic pressure & forces resulting from cellular
proliferation in pulp & surrounding tissues may account
for eruption of teeth.

67. In 1944 Carlson published a comprehensive radiographic
analysis of eruption of different types of permanent teeth.
He showed that for human permanent premolars:
1) eruption begins only after crown formation is complete,
2) root formation occurs initially at expense of basal bone
without movement of crown,
3) Most of root growth occurs during stage of rapid
preocclusal eruption to occlusal plane,
4) completion of root, like its initial growth, is at expense of
basal bone, &
5) teeth continue to erupt slowly or move with growth of
alveolar process throughout life.

68. The Intraosseous Stage of Eruption
All teeth develop within the alveolar bone of jaws.
 Challenge of intra osseous stage of tooth eruption is to
escape from bone surrounding crown and to redirect growth
of alveolar bone proper to surround & support a developing
root. Former involves bone resorption & latter bone
formation on opposite sides of erupting tooth.
These activities have been shown to depend upon the
adjacent parts of the true dental follicle.
Studies in nonhuman primates have shown that rootless
teeth can erupt & that follicle is important in eruption.
Damage to follicle was most reliable predictor of failed
eruption in transplantation studies.
In periods of rapid root growth, bone formation occurs
primarily in furcation areas

69. . Bone growth in apical region occurs only if root growth is
not fast enough to keep up with eruption. Rate of eruption is
rate of formation of eruption pathway and its coordination
with bone formation in selected areas of crypt & alveolar
crest. Since rootless teeth can erupt, root formation is not
considered prime mover in tooth eruption.
Movement of tooth through bone requires a coordinated
resorption & formation of bone, that this process can be
plastic, & asymmetrical to accommodate root growth and
tooth drift,& that these metabolic events likely begin in
enamel epithelia & are continued and coordinated by dental
follicle.

70. Speed of Tooth Eruption
Erupting tooth move at different speeds at different
times.
 Initially, eruption is slow in bone.
If there are prolonged delays, ankylosis of tooth to bone
can result.
 The rate of eruption increases as tooth is released from
bone, penetrates mucosa, & becomes very slow as it
approaches occlusal plane. These shifts in speed are also
seen in root formation.

71. Basic Principles in Tooth Eruption
Active tooth eruption begins in an interaosseous
environment.
Bone resorption, necessary for eruption, is regulated by
dental follicle. Like bone resorption, alveolar bone formation
associated with tooth eruption depends upon dental follicle
& is associated with high cell proliferation.
(1) Any region of a dental follicle has the potential for
initiating and regulating bone resorption and bone formation
or for not influencing bone metabolism.
(2) Movement of teeth during eruption consists of preparing
a path through bone or soft tissues and moving them along
this path. There is a failure of eruption when an eruption
pathway has not been formed.

72. (3) Root formation is accomodated during tooth eruption &
is a consequence, not a cause of the process.
(4) Bone formation & root formation move an erupting
tooth through oral epithelium & into its position within
dental arch at occlusal plane. It is unlikely that periodontal
ligament contributes substantially to eruption, but may
have a role late in process. Bone formation & possibly
formation of apical cementum maintain a slow eruptive
movement throughout life of tooth.

75. SEQUENCE OF EMERGENCE OF PRIMARY
TEETH
 Predominant sequence of eruption of primary teeth
in individual jaw is –
 Central incisor
 Lateral incisor
 First molar
 Canine
 Second molar

76. TIME LINE FOR HUMAN TOOTH DEVELOPMENT
Age developmental characterisitics
42-48 days bud stage : deciduous incisors ,
canines & molars
55-56 days bell stage for deciduous teeth ,
bud stage for permanent
14 weeks bell stage for deciduous teeth ;bud
stage for permanent teeth
18 weeks dentin & functional ameloblats in
deciduous teeth
32 weeks dentin & functional ameloblasts in
permanent first molars

78. SHEDDING OF TEETH
 Physiologic process resulting in complete elimination of
deciduous dentition.
Pattern of shedding
Result of progressive resorption of roots of deciduous teeth
and its supporting tissues.
Pressure generated by erupting permanent tooth guides pattern
of deciduous tooth resorption.
Initially , pressure is against root surface of deciduous tooth
and resorption occurs on lingual surface.

79.  Later these developing tooth germs occupy a position
directly apical to the deciduous tooth.
 In mandibular incisors the apical positioning of the tooth
germs does not occur thus permanent tooth erupts
lingually.

80. RESORPTION OF DECIDUOUS MOLARS
 Resorption of roots of deciduous molars first begin on
their inner surfaces because early developing bicuspids
are found between them.
 With continued growth of jaws & occlusal movement of
deciduous molars, successional tooth germs lie apical to
deciduous molars.
 When bicuspids begin to erupt , resorption of deciduous
molars is again initiated and continues until roots are
completely lost & tooth is shed.

81.  Occurs on surface of cementum and dentine .
 Involves a loss of the organic as well as mineral
constituent of the matrix .
 During resorption process of disorganization
relative to mineral & organic components occurs
more or less concomitantly.
 Resorption of cementum & dentine of deciduous
teeth is characterized by the presence of
osteoclasts.

82. PRIMARY ROOT RESORPTION WITH
PERMANENT SUCCESSOR
 Root resorption of primary teeth starts at site of root
that is closest to permanent successor. E.g in anterior
teeth completed crown of permanent successor is
found lingual to apical third of root of primary
predecessor:
 Resorption of lingual surface of apical third of primary
tooth root.
 Resorption proceeds horizontally in incisal direction
until primary tooth sheds & permanent tooth erupts.

83. PRIMARY ROOT RESORPTION WITHOUT
PERMANENT SUCCESSOR
 Root is protected from resorption by presence of
narrow PDL cell layers which are composed of-
Collagen fibers
Fibroblasts
Cementoblasts
 Degrdation of PDL proceed root resorption & root
removal of collagen fibres of PDL is considered
main step in initiation of this process.
 As face grows & muscles of mastication enlarge
,forces that are applied on deciduous tooth become
heavier than primary tooth periodontal ligament can
withstand.

84. HISTOLOGY OF SHEDDING
 Odontoclasts are resorbing cells derived from
monocytes & migrate from blood vessels to resorption
site , wthere they form multinucleated odontoclast with a
clear attachment zone & ruffled border.
 Giant multinuclear cells with 4-20 nuclei
 Resorption occurs at ruffled border which greatly
increses surface area of odontoclast in contact with
bone.
 Distribution of odontoclast during tooth resorption-
found on surface of roots in relation to advancing
permanent tooth.
 Single rooted tooth shed before root resorption is
completed.

85.  Odontoclasts are not found in pulp chamber of
these teeth.
 In molars, roots are completely resorbed & crown is
partially resorbed.
 Odontoblasts layer is replaced by odontoclasts.
 Sometimes all dentine is removed & vascular tissue
is seen beneath translucent cap of enamel.

97. CLINICAL CONSIDERATIONS
 Natal or neonatal teeth
(Massler & Savara 1950)
Eruption of teeth at birth called natal
teeth or
during first 30 days of life called neonatal teeth

98.  They may be well formed & normal or represent
hornified epithelial structures without roots.
 Found on gingivae over crest of ridge &
 arise either from an accessory bud of dental lamina
ahead of deciduous bud or from bud of an
accesssory dental lamina

99. Macknin et al (2000) identified symptoms like general
irritability ,disturbed sleep, gum inflammation ,drooling ,
loss of appetite, diarrhea, circumoral rash ,intraoral
ulcers, sucking ,wakefullness & ear rubbing temporailly
related to teething.
•Baby is teething when his or her first set of teeth,
called primary teeth , break through the gums.
•Begins at around 6 months of age.
TEETHING

100. •Carpenter (1978) found that in 120 subjects ,during
eruption of anterior teeth only 39% exhibited several
symptoms ( fever , vomiting, diarrhea, drooling irritability
,rashes) & 78% exihibited symptoms in case of eruption
of posterior teeth .
Also observed that symptoms disappeared on either day
of or day after eruption of tooth.

101. 270 children aged between 8 and 36 months were selected &
divided into 5 groups with 54 children initially enrolled in each group.
Children were seen during an 8-day period during tooth eruption.
Five methods used as remedies to reduce teething symptoms were:
1) cuddle therapy, 2) ice, 3) rubbing the gums, 4) teething rings and 5)
food for chewing. Teething symptoms, type of erupted tooth,
symptoms of recovery & mother’s satisfaction with treatment were
evaluated.
Results:250 children (mean age 16 ± 7.2 months) completed study. Most
frequent teething symptoms were drooling (92 %), sleep disturbances
(82.3 %) and irritability (75.6 %). These symptoms were more pronounced
in low birth weight children (p > 0.05). Canine eruption led to more loss of
appetite than incisor (p = 0.033) or molars eruption (p = 0.014).

102. The most favorable results for time to recovery & mother’s
satisfaction were seen when teething rings were used, followed by
cuddle therapy and rubbing the gums.
By: Memarpour, Mahtab; Soltanimehr, Elham; Eskandarian, Taherh. BMC Oral Health. Jul2015, Vol. 15 Issue
1, p1-8. 8p

104.  Develops from third tooth bud arising from dental
lamina near permanent tooth bud or possibly from
splitting of permanent bud itself.

116. BIBLIOGRAPHY
Orbans oral histology & embryology (12th edition) (22-
45) (281 – 303)
Memarpour, Mahtab; Soltanimehr, Elham;
Eskandarian, Taherh. BMC Oral Health. Jul2015, Vol. 15
Issue 1, p1-8. 8p
Wise GE, Frazier- Bowers S ,D’Souza RN:Crit Rev Oral
Biol Med 2002; 13-323
Ten’s cate of oral histology 8th edition(70 – 94)
Oral development of histology by James k. Avery 3RD
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Shafer’s textbook of oral pathology 6th edition (38- 79)