Theories Of Tooth Eruption With Clinical Considerations

Describe briefly the theories of the eruption of teeth. Add a note on clinical considerations related to tooth eruption.
Answer:

Theories of the eruption of tooth:

1. Bone remodeling theory:

It proposes that selective deposition and resorption of bone bring about eruption.
It has been established that the dental follicle is absolutely required for it.
This follicle provides the source for new bone-forming cells and a channel for osteoclasts that are derived from monocytes.
This theory was rejected as the tooth continues to erupt even after the selective removal of the dental follicle.

2. Root formation theory:

It proposes that the proliferating root impinges on a fixed base thus converting an apically directed force into occlusal movement.
According to this theory, the root requires a fixed base to translate the apical force into occlusal movement.
Thus, it postulated the existence of a cushion hammock ligament to provide a fixed base for the growing root to react against.
This theory was rejected because.
It is the crown that moves away from the root.
Root elongation may exert pressure and cause resorption of bone at the base of its socket.
The Hammock ligament has no bony insertion thus it cannot act as the fixed base.
some teeth move greater than their root length.
Even rootless teeth erupt.

3. Vascular pressure theory:

It proposes that a local increase in tissue fluid pressure in the periapical region is sufficient to move the tooth.
Teeth move in synchrony with the arterial pulse, so local volume changes can produce limited tooth movement.
Ground substance can swell by 50% with the addition of water and a differential pressure sufficient to cause tooth movement between the tissues below and above an erupting tooth has been reported.
Through vascular pressure can play an important role by generating an eruptive force, different opinions have been put forward as to whether these pressures are primarily responsible for eruption.

4. Ligament traction theory:

It proposes that the cells and fibers of the ligament pull the tooth into occlusion.
According to this theory, force is initiated by the fibroblast causing an eruption of teeth.
This force is transmitted to collagen fiber bundles.
Once the tooth has appeared in the oral cavity and before it attains its final position, the periodontal ligament fibers exert the tractional force due to its attachment to the alveolar bone and to its orientation.
When the formation of collagen is inhibited with drugs and when fibroblastic activity is stopped in the periodontal ligament area, eruption stops.
Thus, this theory is the most accepted theory.

Ligament traction theory Clinical considerations:

The periodontal ligament and the bone of the jaw possess elasticity which is used for orthodontic movement.
The eruption schedule of teeth helps in the assessment of dental age.
Sometimes natal and neonatal teeth appear.
Premature loss of deciduous may lead to delayed eruption of permanent and drifting of opposite teeth which block the eruptive pathway.
Severe trauma may eliminate dental follicles which prevents periodontal ligament formation.
When the tooth breaks through the oral epithelium, an acute inflammatory response occurs in the connective tissue adjacent to the tooth.
Teeth that erupted beyond an occlusal plane are known as supra-erupted teeth.
Teeth lying below the occlusal level are submerged teeth.
Ankylosed teeth do not undergo posteruptive movement.

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