1
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2
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- Root growth
- Cushion hammock ligament
- Bone remodeling
- Pulp growth
- Vascular pressure (Pulp constriction)
- Hydrostatic (Tissue fluid) pressure
- Gubernacular cord
- Dental follicle
- Periodontal ligament traction
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3
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- Growth of the root pushing against the alveolar bone forces the crown
through the gums.
- Contradictions:
- Rootless teeth erupt
- Eruptive movements of teeth do not coincide with the total length of
their roots
- Eruption occurs even after root completion
- Eruption occurs even after surgical removal of Hertwig's epithelial
root sheath, periapical tissue and apical papilla
- Impacted and unerupted permanent teeth with completely formed roots
erupt after surgical exposure
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4
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- Proposed by Sicher in 1942.
- A ligament anchored in the alveolar bone acts like a "cushion
hammock" on which the root rests. Growth of the root apically on
the "hammock" is translated in an axial direction resulting in
tooth eruption.
- Contradiction:
- No histological evidence of the ligament. What is seen is pulpodentinal
membrane.
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5
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- Growth of the alveolar bone pushes the tooth outward.
- Contradictions:
- Fibres run in a reverse direction than what the theory proposes
- New bone cannot exert force on fibres already inserted into the bone
- In Vit A and Vit D deficiency, there is increased alveolar bone or
osteoid, but eruption rates not increased
- When tooth with incompletely formed root is pinned to the bone, bone
resorption takes place as root grows
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6
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- Growth of pulp produces eruptive force.
- Contradictions:
- Teeth with extirpated pulps erupt normally
- Vit. D deficiency results in increased proliferation of pulp, but there
is no increase in rate of eruption
- Eruption occurs even after surgical removal of Hertwig's epithelial
root sheath, periapical tissue and apical papilla
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7
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- States that as dentin continues to form, there is pressure on the pulp,
which results in eruption of the tooth.
- Contradictions:
- Rootless teeth erupt
- Teeth with extirpated pulps erupt normally
- Vitamin A deficiency results in pulp constriction but there is no
increased rate of eruption
- Protein deficiency results in thin dentin and wider pulp, but eruption
rate not is not decreased
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8
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- Presence of blood vessels in the apical region causes formation of
tissue fluid which exert a steady pressure which result in tooth
movement.
- Contradictions:
- Eruption occurs even after surgical removal of Hertwig's epithelial
root sheath, periapical tissue and apical papilla
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9
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- Gubernacular cord (fibrous connective tissue strands that connect oral
mucosa to the follicles of the permanent tooth germs) pulls the teeth
from underlying tissues.
- Contradictions:
- Theory does not explain tooth movement after eruption
- Theory does not explain tooth movement of deciduous teeth
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10
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- Follicular cells express factors which recruit osteoclasts that permit
bone remodeling around the erupting tooth.
- Evidences:
- In osteopetrotic animals (which lack osteoclast differentiation),
eruption is prevented
- Immunohistochemical findings of cellular activity around REE and dental
follicle
- Experiment
- Molar removed, follicle stripped, molar replaced – no eruption
- Crown removed, follicle intact – eruptive pathway still forms within
bone
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11
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- Force for eruptive tooth movement resides in periodontal ligament which
pulls the tooth out
- Evidences:
- Experiment by interfering with collagen synthesis by denying Vit C or
by injecting latharytic agent slows down or stops tooth movement.
- In a continuously erupting tooth (e.g. rodent incisor), is cut and a
barrier is placed between 2 halves, the distal half continues to erupt in
spite of dissociating from the growing root and apical vasculature.
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12
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- Mechanism: Forces necessary for generating tooth eruption may be derived
by:
- Randomly oriented fibres become ordered
- Contraction of collagen due to crosslinking
- Contraction of collagen due to GAG turnover
- Contraction of collagen due to myofibroblasts (have wavy nucleus,
microtubules and microfilaments)
- Remodeling of periodontal ligament collagen by fibroblasts
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13
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- Initially crowding of deciduous tooth germs
- Dec 2nd molars move backward and anterior tooth germs move forward
- All teeth move bodily outward and upward (mand teeth) or downward (max
teeth)
- Perm tooth germs lie in their own bony crypts lingual to or between the
roots of dec teeth
- Initially the perm max molars have their occlusal surfaces facing
distally, but swing mesially
- Initially the perm mand molars have their long axes inclined mesially,
but swing vertically into position after mand grows to provide space
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14
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- Intraosseous phase: 1-10 microns/ day tooth movement
- Extraosseous phase: 75 microns/ day
- Environmental factors (muscle forces from tongue, lips, cheeks; contact
of erupting teeth with other erupted teeth; habits like thumb sucking)
determine the final position of the tooth within the dental arch.
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15
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16
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- To accommodate growing jaws
- To compensate for occlusal wear
- To compenstae for interproximal wear
- Physiological mesial drift
- Occlusal forces
- Pressure from cheeks and tongue
- Transseptal fibres
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