Mechanics Of Tooth Movement

What are the characteristic features of orthodontic force. Describe the deleterious effects of orthodontic force on root.
Answer.

Characteristic Features of Orthodontic Force

Clinically

Orthodontic force should produce rapid tooth movement.
Orthodontic force should cause minimum patient discomfort.
Orthodontic force should be such that the lag phase of tooth movement should be shorter.
As orthodontic force is applied and the tooth is moved it should be loosened in its socket.

Histologically

After application of an orthodontic force vitality of tooth and PDL is maintained.
Orthodontic force should initiate maximum cellular response.
Orthodontic force should produce frontal resorption.
Orthodontic force is applied such that the integrity of periodontal attachment is maintained by reorganization of fibers.

Deleterious Effects of Orthodontic Force on Root

Tissues lying adjacent to the root start undergoing remodeling as tooth movement occur.
Cementum or root remodeling also starts.
Resorption of cementum occurs next to hyalinized areas so this means that root start resorbing at the place when the heavy forces are implicated.
Root remodeling restore proper length of root at the time of orthodontic tooth movement.
As islands of cementum are formed the repair of root does not take place and there is permanent loss of root structure at apex.
There are two types of root resorption, i.e. localized and generalized

Localized Root Resorption

Application of excessive orthodontic force as well as excess long duration of treatment leads to the enhancement in chances of resorption.
Susceptibility of upper incisors is more for resorption to occur.
As the roots are pressed against cortical plate root resorption occur.

Generalized Root Resorption

It is divided into two types, i.e. moderate and severe.
Moderate generalized root resorption: In most of the patients generalized shortening of root will occur due to orthodontic treatment. Resorption of maxillary incisors is highest.
Severe generalized root resorption: It occurs in the condition like hypothyroidism, in such cases orthodontic treatment is contraindicated.

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