Periodontal Ligament Traction Theory Of Tooth Eruption

Question 1. Theories of eruption.
Answer:

1. Bone remodeling theory.

It proposes that selective deposition and resorption of bone bring about eruption.

2. Root formation theory.

It supposes that the proliferating root impinges on a fixed base, thus converting an apically directed force into occlusal movement.

3. Vascular pressure theory:

It supposes that a local increase in tissue fluid pressure in the periapical region is sufficient to move the tooth.

4. Ligament traction theory.

It proposes that the cells and fibers of the ligament pull the tooth into occlusion.

Question 2. Hydrodynamic theory.
Answer:

It is also called vascular pressure theory.
It supposes that a local increase in tissue fluid pressure in the periapical region is sufficient to move the tooth.
Experiments have shown that an increase in hydrostatic pressure increases the rate of eruption while a decrease in hydrostatic pressure decreases the rate of eruption.
But it has not been proved whether this pressure is primarily responsible for eruption.

Question 3. PDL traction theory.
Answer:

It proposes that the cells and fibers of the ligament pull the tooth into occlusion.
It is the most accepted theory.
According to this theory, forces initiated by fibroblast present in PDL could be responsible for tooth eruption.
During the conversion of procollagen to collagen in the PDL, a contraction of fibroblasts causes tractional force.
This force is transmitted to the collagen to cause tooth eruption.
When collagen formation is inhibited and fibroblastic activity is stopped, eruption stops.
Thus, this theory is accepted.

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