Lec. 3
Pedodontics
‫حسن الوطيفي‬.‫د‬
Eruption of the teeth
Definition: The process of eruption involves the movement or change of position of the
tooth from the deeper portion of the jaws into the oral cavity until it achieves occlusal
contact with adjacent and apposing teeth.
Although many theories have been advanced, the factors responsible for the eruption of
the teeth are not fully understood.
The factors that have been related to the eruption of teeth include:
 Elongation of the root.
 Forces exerted by the vascular tissues around and beneath the root.
 Growth of the alveolar bone.
 Growth of dentin.
 Growth and pull of the periodontal membrane.
 Hormonal influences.
 Presence of a viable dental follicle.
 Pressure from the muscular action.
 Resorption of the alveolar crest.
Factors influencing the timing of eruption
 Genetic factors: lower teeth erupted before upper teeth.
 Environmental factors.
 Gender: girls precede boys.
 Socioeconomic condition.
 Birth weight.
 Hormonal factors: pituitary growth hormones and thyroid hormones.
The researchers state that tooth eruption is a complex and tightly regulated process that
involves cells of the tooth organ and the surrounding alveolus. Mononuclear cells
(osteoclast precursors) must be recruited into the dental follicle prior to the onset of
eruption. These cells, in turn, fuse to form osteoclasts that resorb alveolar bone, creating
an eruption pathway for the tooth to exit its bony crypt. In recent years, knowledge of the
biology of tooth eruption has greatly increased. What has emerged is the realization that
interactions of osteoblasts, osteoclasts, and dental follicles involve a complex interplay of
regulatory genes that encode various transcription factors, proto-oncogene, and soluble
factors.
Phases of tooth eruption:
1. Presumptive phase (pre-eruptive phase):
All movements of primary and permanent tooth germs (crowns) from time of their early
initiation and formation to the time of crown completion (ends with early initiation of
root formation).
2. Eruptive phase: Starts with initiation of root formation and made by teeth to move
from its position with in bone of the jaw to its functional position in occlusions. Has an
intraosseous and extra osseous compartment. It includes 4 stages: Root formation,
movement, penetration and oclussal contact.
3. Post eruptive phase: Takes place after the teeth are functioning to maintain the
position of the erupted tooth in occlusion while the jaws are continuing to grow and
compensate for colossal and proximal tooth wear.
Why do developing crowns move constantly in the jaws during the presumptive
phase?
1. To place the teeth in position for eruptive tooth movement.
2. To alleviate the problems of jaw growth, this allows second molar to move backward
and anterior teeth to move forward
2 Developing crown move constantly during the presumptive phase as they respond to
positional changes of the neighboring crowns and to changes in the mandible and
maxilla.
3. Permanent teeth develop lingual to the incise level of the primary anterior teeth and
later as primary teeth erupt, the permanent crowns are lingual to the apical 3rd of primary
roots.
4. Permanent prernolars move from colossal level of primary molars to a position
enclosed within the primary tooth roots.
5. All movements in the presumptive phase occur within the crypts of the developing
crowns.
Type of tooth movement in pre-eruptive phase:
 Total bodily movement.
 Movement where one part remains fixed while the rest continues to grow leading
to change in the center of the tooth germ.
Eruptive tooth movement: 4 major events occur:
1. Root formation: Include:
 Space is required for root formation.
 Proliferation of epithelial root sheath.
 Initiation of root dentin and pulp.
 Increase in fibrous tissue of the follicle
2. Movement:
 Occurs finically or colossally.
 The main reason for movement is so that the roots can form normally.
 Reduced enamel epithelium fuses and contacts the oral epithelium.
3. Penetration of the tooth's crown tip through the fused epithelial layers allowing
entrance of the crown into the oral cavity.
4. Intraoral incisal or colossal movement of the erupting tooth continues until clinical
contact with the opposing crown occurs.
Clinical crown: During eruption, the exposed crown extending from the cusp tip to the
area of the gingival attachment.
Anatomic crown: Entire crown, extending from cusp tip to the cementoenamel (CEJ.)
junction
Pos- eruptive tooth movement:
1. Movements to accommodate the growing jaws. Mostly occurs between 14 and 18
years by formation of new bone at the alveolar crest and base of socket to keep pace wit
increasing height of jaws.
2. Movements to compensate for continued occlusal wears. Compensation primarily
occurs by continuous deposition of cernentum around the apex of the tooth. However,
this deposition occurs only after tooth moves. Similar to eruptive tooth movement.
3. Movements to accommodate interproximal wear. Compensated by mesial or proximal
drift. Mesial drift is the lateral bodily movement of teeth on both sides of the mouth.
Very important in orthodontics.
Active eruption: to compensate incisal arid occlusal wear.
Passive eruption: gradual recession of the gingiva and the underlying alveolar bone.
Both active and passive eruption leads to lengthening of clinical crown.
Variation in the sequence of eruption:
1- The mandibular first permanent molars are often the first permanent teeth to erupt.
They are quickly followed by the mandibular central incisors.
2- Moyers stated that the most common sequence of eruption of permanent teeth in the
mandible is first molar, central incisor, lateral incisor, canine, first premolar, second
premolar, and second molar.'' The most common sequence for the eruption of the
maxillary permanent teeth is first molar, central incisor, lateral incisor, first premolar,
second premolar, canine, and second molar (Fig. 1).
Fig. 1
3- These common sequences in each arch to be favorable for maintaining the length of
the arches during the transitional dentition.
4- The mandibular canine erupted before the maxillary and mandibular first premolars in
girls. In boys the eruption order was reversed, the maxillary and mandibular first
premolars erupted before the mandibular canine.
5- The mandibular canine erupts before the first and second premolars because of:
 This sequence aids in maintaining adequate arch length.
 Prevent lingual tipping of the incisors. Lingual tipping of the incisors not only
causes a loss of arch length but also allows the development of an increased
overbite.
 An abnormal lip musculature or an oral habit that causes a greater force on the
lower incisors than can be compensated by the tongue allows a collapse of the
anterior segment. For this reason use of a passive lingual arch appliance is often
indicated when the primary canines have been lost prematurely or when the
sequence of eruption is undesirable.
6- A deficiency in arch length can occur if the mandibular second permanent molar
develops and erupts before the second premolar.
7- Eruption of the second permanent molar first encourages mesial migration or tipping
of the first permanent molar and encroachment on the space needed for the second
premolar.
8- In the maxillary arch the first premolar ideally should erupt before the second
premolar, and they should be followed by the canine.
9- The untimely loss of primary molars in the maxillary arch, which allows the first
permanent molar to drift and tip mesially, results in the permanent canines being blocked
out of the arch, usually to the labial side.
10- The position of the developing second permanent molar in the maxillary arch and its
relationship to the first permanent molar should be given special attention. Its eruption
before the premolars and canine can cause a loss of arch length, just as in the mandibular
arch.
11- The eruption of the maxillary canine is often delayed because of an abnormal
position or devious eruption path. This delayed eruption should be considered along with
its possible effect on the alignment of the maxillary teeth.
LINGUAL ERUPTION OF MANDIBULAR PERMANENT INCISORS
The eruption of mandibular permanent incisors lingual to retained primary incisors is
often a source of concern for parents. The primary teeth may have undergone extensive
root resorption and may be held only by soft tissues. In other instances the roots may not
have undergone normal resorption and the teeth remain solidly in place. It is common for
mandibular permanent incisors to erupt lingually, and this pattern should be considered
essentially normal. It is seen both in patients with an obvious arch length inadequacy and
in those with a desirable amount of spacing of the primary incisors.
Management:
1. In either case the tongue and continued alveolar growth seem to play an important role
in influencing the permanent incisors into a more normal position with time. Although
there may be insufficient room in the arch for the newly erupted permanent tooth, its
position will improve over several months.
2. In some cases there is justification for removal of the corresponding primary tooth.
Extraction of other primary teeth in the area is not recommended, however, because it
will only temporarily relieve the crowding and may even contribute to the development
of a more severe arch length inadequacy.
Influence of premature loss of primary teeth on the eruption time of their
successors
1- Eruption of the premolar teeth is delayed in children who lose primary molars at 4 or 5
years of age and before.
2- If extraction of the primary molars occurs after the age of 5 years, there is a decrease
in the delay of premolar eruption.
3- At 8, 9, and 10 years of age, premolar eruption resulting from premature loss of
primary teeth is greatly accelerated.
Notes:
 Teeth reach occlusion before the root development is complete.
 The tooth emerges when 2/3 of root formed.
 Root completion 2-3 years after eruption.
ERUPTION SEQUENCE:
 MANDIBULAR INCISORS
 1 ST PERMANENT MOLARS, UPPER INCISORS
 CANINE (MAND)
 1ST PREMOLAR
 MAX CANINE
 2ND PREMOLAR
ALSO:
 MAXILLARY: 1ST MOLAR, CI, LI, 1ST PM, 2ND PM, CUSPID, 2ND
MOLAR, 3RD MOLAR
 MANDIBULAR: 1ST MOLAR, CI, LI, CUSPID, 1ST PM, 2ND PM, 2ND
MOLAR, 3RD MOLAR
Primary Teeth: Sequence of Eruption
 ERUPTION SEQUENCE
 MANDIBULAR INCISORS
 1ST PERMANENT MOLARS, UPPER INCISORS
 CANINE (MAND)
 1 ST PREMOLAR
 MAX CANINE
 2ND PREMOLAR
 ALSO:
 MAXILLARY: 1ST MOLAR, CI, LI, 1ST PM, 2ND PM, CUSPID, 2ND
MOLAR, 3RD MOLAR MANDIBULAR: 1ST MOLAR, CI, LI, CUSPID, 1ST
PM, 2ND PM, 2ND MOLAR, 3RD MOLAR
Premature eruption of permanent teeth:
 Not enough root for stability of primary tooth.
 Gross caries in primary tooth.
 Abscess cause bone resorption beneath primary tooth.
Dental age Determined by:
1-Which permanent teeth have erupted
2-Amount of resorption of primary teeth
3-Amount of development of permanent teeth