No extractions needed with clear aligners...Fact or myth?

One of the major discussions in orthodontics that exists since its origins is about the necessity of tooth extraction . If we look back in time, it is interesting to see how this issue has fluctuated over time, resulting in orthodontic trends or " tendencies" that support the need for extractions or, on the other hand, the possibility of treating all patients without them. The concept of non-extraction treatment has even been used as an advertising claim to offer patients a more appealing treatment (nobody likes to have teeth removed) but without assessing the long-term consequences or risks of this treatment. Just as each person has different feet and there are different shoe sizes for each one of them, orthodontic treatments should also be planned accordingly to the malocclusion and biological limits of each patient.

Extraction vs. non-extraction

Extraction or non-extraction decision does not depend on the appliance we place on the patient. Whether with brackets or aligners, the need for extraction will be determined after an exhaustive diagnosis of the case. However, depending on the technique we use, it is possible that we may opt for different extractions according to the biomechanics we want to apply. For example, in a case with full Class II, it is possible to extract wisdom teeth if we treat the case with aligners, and, if we treat it with brackets, we may opt to extract premolars.

Why? Because we all know that closing premolar spaces with aligners is biomechanically more complex to achieve than upper distalization, whereas with brackets, since we have better control of root movement, we can close these spaces in a more efficient and predictable way

Fenestrations and dehiscences

Fenestrations and dehiscences of the alveolar bone are defects that are naturally present in many people; it is not necessary to undergo orthodontic treatment for them to arise. It is also a fact that, after orthodontic treatment, these defects tend to increase.

If we review some research papers on this subject, it is interesting to see how the number of recessions and dehiscences after treatment with brackets increases between 10% and 20%, whereas in cases treated with aligners, they only increase by 4%. These are few articles, with different methodologies, so these numbers should be taken with a pinch of salt. But they give us a clue about the greater control that digital planning with aligners compared to conventional treatment, in which we cannot always control the proinclination and expansion of the teeth. It is possible that brackets biomechanically outperform aligners in certain movements, but aligners are clearly superior in terms of control.

We already know that orthodontic treatment increases the risk of creating fenestrations/ dehiscences or increasing them if they are present from the beginning. But...does this risk apply to all cases?

Let's see which variables affect:

• Age: The older the patient, the slower the bone metabolism and the worse will be the patient's response to tooth movement, which translates into a higher risk of fenestration/dehiscence.
• Bone area: As a general rule, most bone defects are located in the vestibular cortex, with a greater presence in the maxilla than in the mandible.
• Race: Afroamerican patients have a higher percentage of fenestrations/dehiscences than Caucasian patients, possibly due to the greater proinclination of the anterior teeth.
• ANB angle: There is a direct relationship between the ANB angle and the presence of recessions/dehiscences.
• Expansion: The greater the planned expansion, especially if we start from a posterior torque close to 0º, the greater the risk of creating or increasing bone defects.

Knowing these variables, we will be able to analyze the case more accurately and decide whether or not to perform extractions. The use of CBCT is really helpful to visualize the possible consequences of the movements we plan, but it cannot replace orthodontic knowledge. This tool has a certain margin of error and is not able to simulate bone remodeling, so it is advisable to take these variables into account when treating our patients.

Allahham DO et al. Association between nonextraction clear aligner therapy and alveolar bone dehiscences and fenestrations in adults with mild-to-moderate crowding. Am J Orthod Dentofacial Orthop 2023;163:22-36.