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Clear Aligners - The danger of limitations

Opdateret: 29. aug. 2022

Just because you are working with an aligner system that has a lot of limitations built in, doesn't mean you'll avoid making errors - on the contrary!

It sounds so good, but it's pretty bad.

It's about the limitations several aligner systems put into their software.

Stop sign at road

Avoid malpractice

The intention behind the restrictions seems good enough.

The idea is to give general dentists the impression that they cannot make mistakes treating their patients with clear aligners. By introducing a number of restrictions on the movements that can be planned and performed with the aligner system, the rationale is that dentists using the system will be less likely to do something wrong.

There are just a number of challenges.

First, it is not possible to perform a treatment without affecting all the teeth covered by the aligner.

Secondly, any restriction on tooth movement creates a potential domino effect, increasing the risk of compromises that, contrary to the intention of the restriction, result in patients being treated incorrectly.

Lack of overview

Third, we have learned that many restrictions are imposed by industry employees without a dental background. Those with an understanding of data and algorithms often tend to see orthodontic treatment as one where an algorithm can be designed to ensure optimal treatment every time. At AlignerService, we are therefore frequently asked by various aligner manufacturers if we can provide a set of parameters that can constrain aligner software in a way that aligner treatments are always within some safe boundaries.

To this there is only one qualified answer: "Yes! If you need constraints, you should not do any treatment at all!" The need for restrictions is in fact an expression of a lack of knowledge about orthodontics.

Restrictions in tooth movement almost always (in 90-95% of all treatments) lead to such compromises that dental health is compromised or outright malpractice results.

When orthodontists express opposition to aligner treatments, it is not because the form of treatment is bad. It is because a large proportion of general dentists who use the systems do not have an overview of what they are doing. They are unknowingly incompetent or at worse deliberately incompetent.

Problem 1 - Force distribution

When we treat patients orthodontically we affect all the teeth in the mouth. Even if, for example, we limit the system to moving only the anterior 8-10 teeth. This is because of Newton's third law, which describes how a force in one direction will cause an equal force in the opposite direction.

A very simplified example

When we move the anterior 8 teeth, in a patient with a full set of teeth, we typically do not see a clinical changes in the position of the molars. This is because the anchorage of these teeth in the bone is so large overall and spread over such a large root surface that the forces are not expressed clinically. This does not mean that a force is not applied to the teeth. The force is just distributed over a larger area than that of the teeth being moved.

This means that as a practitioner you should ALWAYS be aware of the force distribution when moving teeth orthodontically. If you do not have an overview of the force distribution and how to work with it, we highly recommend you seek out help when you do your treatment planning.

Problem 2 - the trade-offs

Imagine you have a patient with extreme crowding of the mandibular front. You (typically the patient) only want to straighten the teeth in the lower jaw and do nothing about the upper jaw. In this way, you have imposed a number of fairly severe restrictions on how you can move the mandibular teeth.

The upper jaw and lower jaw must fit together. When we only correct the teeth in one jaw, it puts some very strong restrictions on how we can move the teeth in the jaw we want to correct, without compromising occlusion.

If we try anyway, it will often manifest itself in a tremendous amount of IPR. This is to an extent that could be significantly reduced by moving the teeth in both the upper and lower jaws.


Just as I have tried to illustrate in the example where we only treat one jaw, limitations in an aligner system will lead to a number of unintended consequences that only few users are aware of.


In a malocclusion we typically find molars rotated mesially. By rotating the molars back into their ideal position, we gain many millimetres of space. Space that sometimes enables us to avoid IPR or at least decrease the amount of IPR needed. Restricting the aligners to not move the molars will therefore increase the need for IPR.

You thereby do not change the malocclusion, while grinding away enamel for no reason.


Here we often see a restriction based on the fear of moving the teeth out through the facial bone - a well-founded fear which is not necessarily minimised by these restrictions.

Many restrictions also result in not being able to expand enough. This in turn will lead to a greater need for IPR to achieve a reasonably satisfactory end result, as well as often preventing the practitioner from reversing the malocclusion. In addition, it may lead to unsatisfactory aesthetic results, as the teeth cannot be moved into an appropriate position. Even if there is enough bone to do so.

Spiral staircase


We often see dentists asking if it's ok to compromise when their patients need teeth rotated more than the limitations of their aligner system allow.

When we are asked, it is almost always because the dentist knows it is not okay, but is seeking a colleague's blessing to perform a treatment that will actually end up being a malpractice.

Our rule of thumb would be: "If you are in doubt - you are not in doubt"


I have only touched on a few of the many challenges inherent in aligner systems that have build in limitations. As is evident, there are virtually no benefits to patients or practitioners related to the limitations.

Limitations in aligner software are primarily imposed by aligner manufacturers in the hope that general practitioners will be lured into believing that they can do no harm to their patients. Which will encourage more dentists to perform aligner treatments and thus increase the sales of the aligner manufacturers. With my knowledge of dentists, this does not seem to me to match the professional profile most want to maintain for themselves as well as for the dental profession.

In conclusion, I would like to state that in rare cases, it is possible to treat patients with a system that has many limitations built in. As a dentist, you just need to know what you are doing to know if that is the case - before you start any treatment. Here I would remind you that there is a good reason why it takes 3-4 years to become an orthodontist.

Just because you are working with an aligner system that has a lot of limitations built in, doesn't mean that you avoid performing malpractice - quite the contrary!


If you need help planning your treatments or support throughout your treatment process, you are always welcome to contact us.

Jesper Hatt DDS co-founder of AlignerService

Many kind regards

Jesper Hatt DDS

Co-founder of AlignerService

T: +41 78 268 00 78


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