What are reliable movements in Aligners?

Clear aligners have taken the world by storm in recent years. Not only are they convenient and comfortable for the patient, but they also overcome conspicuous and negative aesthetic impacts brought on by older orthodontic treatment solutions – fixed appliances.

Before we applaud the spectacle that is CAT, we must first accredit the person who brought it to the limelight in the first place. Kesling, in 1946 developed and introduced a series of rubber-based clear tooth positioners that could progressively align minor mispositioned teeth after a course of mandatory fixed orthodontic treatment. Later, experts explored the prospect of a fully transparent aligner system that could independently achieve minor tooth movements. The clear aligner systems including the Invisalign® system we know today came about as a result of this curious venture.

Aligner therapy works by sequentially moving the malaligned teeth in small increments with consecutive aligners to ultimately reach the desired orthodontic outcome. They are programmed to move a tooth or multiple teeth by 0.25 to 0.33 mm every 14 days. As can be expected, aligner therapy is not indicated in all orthodontic cases. While CAT is sufficient to resolve anterior crowding and molar distalization (2.5 mm), they are not equipped to modify bodily expansion of the maxillary posterior teeth, canine and premolar rotational movements, extrusion of maxillary incisors, and overbite control.

So, what seems to be the issue? Aligner therapy makes use of certain movements that allow this form of treatment to be favourable for correcting certain cases.

Which are reliable movements in aligners?

Although the idea of using consecutive clear thermoplastic appliances to align teeth is empathetic, it can also be ambitious in some aspects. According to a study, the average rate of accuracy of three movements – rotation, mesiodistal tipping, and vestibulolingual tipping was 70.6% in the anterior tooth region. Overall, the rate was 73.6% across both full arches.

Out of all the movements, mesiodistal tipping was the most predictable movement. It achieved a mean accuracy of 82.5%. Individually, rotation reached 66.8% accuracy and vestibulolingual tipping was 72.9%. Mesiodistal tipping of the canines, premolars, and molars showed a high accuracy index in the upper arch as compared to the lower arch.

Another study concluded that since some tooth movements displayed a significant difference between predicted and achieved positions of the teeth, it could be greatly beneficial for the patient to go through the treatment. They said that the evaluation of the treatment after the 15th aligner would be greatly valuable.

Not all treatment cases can result in ideal tooth movements, especially with aligners. Some movements are just achieved easier with aligners than others. Choosing the right treatment technique specific to the patient’s orthodontic condition is vital to ensure optimal results.