19: Aligners

Chapter 19


In addition to the conventional systems of removable and fixed appliances, there are now methods of straightening and de-rotating overcrowded teeth by using aligners.

Most aligners are similar in appearance to Essix retainers and are made of flexible plastic. There are some aligners that are made from acrylic.

They are both removable.

They are usually used as a non-extraction treatment option for patients with:

  • mild spacing
  • mild crowding
  • mild rotations

They do not aim to treat patients with severe crowding or skeletal discrepancy.

Aligners are popular with adults because:

  • they are less visible
  • they can be taken out for special occasions, e.g. meetings, dates
  • they are easy to use and don’t affect speech
  • apart from when eating and drinking, they can be worn all the time


The advantages of this system are:

  • surgery time, both for the patient and the clinician, can be saved on adjustment appointments
  • the aligners are comfortable, with no sharp wires or brackets to cause discomfort
  • aesthetically, they are very discreet
  • easy to keep clean


The disadvantages of this system are:

  • should an aligner not be worn sufficiently, it cannot produce enough force to achieve steady progress
  • if an aligner is accidentally lost, another one has to be ordered and made, which takes time and incurs an additional cost
  • there is no control over tooth root movements (as there is with fixed appliance therapy)
  • it is limited in the degree of movements it can achieve


Type one

The first type, known under trade names such as:

  • Invisalign
  • ClearStep

use a series of appliances.

Teeth can be aligned using a series of aligners that move them small amounts at a time.

How far the teeth are crowded and rotated would govern how many aligners are needed.

When the first one is fitted, it can feel a little tight and there is significant pressure on the teeth.

After a few days, this becomes less as the teeth are moving towards their new position.

After a fortnight or so, the next aligner is fitted; again, it feels tight and this gets less as the teeth move.

This goes on until the teeth are in their new alignment and are straight.

Type two

The second type, like the one marketed under the name, the Inman Aligner, uses just one appliance.

The Inman Aligner is also a removable appliance. It must be worn as much as possible.

It has a bar over the front of the teeth and uses the force produced by a coiled spring to push and pull the teeth and compress them into alignment.

This method is most successful when aligning the anterior segments.

The patient must visit the surgery regularly to check the aligner’s progress.

The scope and therefore the length of treatment are shorter than other methods.

For both methods, there are small firm foam cylinders available. The patient chews on these and the action of this is said to help seat the aligners.


For both methods, in order to move crowded teeth into a better position, there is a need create some space.

The method of getting this small amount of space is known as interproximal stripping or interdental enamel reduction.

This needs to be done, to a greater or lesser degree depending on the space needed. As the aligners move the teeth, they gradually use up the extra space created.

This technique can also be used selectively in fixed appliance therapy if there is:

  • an area of very mild, localised crowding
  • the need to de-rotate an individual tooth

Sometimes, in order to eliminate ‘dark triangles’ gingivally, contact points are reduced so that the teeth can come closer together and provide an improved shape of the papilla. Interdental enamel reduction can also be employed when re-shaping and contouring.

Stripping or slenderising removes tiny amou/>

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Jan 2, 2015 | Posted by in Orthodontics | Comments Off on 19: Aligners
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