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Biology of Tooth Movements
Cementum is more resistant to resorption: Important in permitting orthodontic tooth movement
Types of Tooth Movement
Types of Tooth Movement
- Tooth Eruption
- Active
- Passive
- Lateral drifts
- Physiological
- Due to loss of adjacent teeth
- Orthodontic tooth movement
| Orthodontic force | Orthopedic force |
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Frontal resorption facilitates orthodontic tooth movement, whereas undermining resorption impedes orthodontic tooth movement. Hyalinization
- It represent a sterile necrotic area, generally limited to 1 or 2 mm in diameter.
- Degeneration
- Elimination of destroyed tissue
- Establishment of a new tooth attachment
Theories of tooth movement
The 3 important theories of tooth movement are
- Pressure tension theory by SCHWARTZ
- Bone bending piezoelectric theory by FARRAR
- Fluid dynamic theory BEIN
Pressure tension theory by SCHWARTZ relies on chemical rather than electrical signals as the stimulus for cellular differentiation and ultimately tooth movement.
Alteration in blood flow within the PDL is produced by the sustained pressure that causes the tooth to shift position within the PDL space, compressing the ligaments in some areas while stretching it in others.
Bone bending piezoelectric theory by FARRAR
Deformation or bending of intraseptal alveolar walls and suggested that bone bending may be possible mechanism for bringing about tooth movement.
Piezoelectric signals have 2 unusual characteristics
- Quick decay rate
- The production of equivalent signal, opposite in direction, when the force is released.
- Area of concavity in bone are associated with –ve charges and evoke bone apposition.
- Area of convexity are associated with +ve charges and evoke bone resorption.
Fluid dynamic theory BEIN
Force Types
- Light, continuous forces
- Never declines to zero.
- Interrupted forces
- Declines to zero
- Intermittent forces
- Declines to zero
Phases of tooth movement
Burstone categories the stages into
1. Initial phase
2. Lag phase
3. Post lag phase<
1. INITIAL PHASE:
- During initial phase very rapid tooth movement is observed over a short distance which then stops.
- This movement represents displacement of the tooth in the PDL and probably bending of the alveolar bone to the certain extent.
- Studies have shown that both light force and heavy force displace the tooth to the same extent during the initial phase of the tooth movement.
- During this phase, little or no tooth movement occurs.
- This phase is characterized by formation of the hyalinized tissue in the PDL which has to be resorbed before tooth movement occurs.
- Light forces
- Heavy forces
- Longer lag phase occurs in case of heavy force to eliminate hyalinized tissue.
- After the lag phase, tooth movement progresses rapidly as the hyalinized zone is removed and the bone undergoes resorption .
- During this phase osteoclasts are found over a large surface area resulting in direct resorption of the bony surface facing the PDL.
MCQ
Q. In orthodontic tooth movement which is involveda) Osteoblast
b) Osteoclast
c) Both A & B
d) None
Answers with explanation
Answer is C
