Strategies for clear aligner case evaluations
A Tuesday morning, a woman in her late thirties in the chair. She wants her lower front teeth straightened before her daughter's wedding. The scan is clean, the photos are sharp, and the software will produce a setup by tomorrow morning if you ask it to. At first glance there is no reason to say no.
Almost any case can be planned. What a case will cost you in unplanned chair time fourteen months from now is a different question, and it is decided before the first setup is ordered.
Case evaluation is judgment, and judgment gets better when it is written down. These are the lines we use in adult cases, and why we drew them where we did.
Which findings stop a clear aligner case before it starts?
In short: seven findings send an adult case out of general practice regardless of how good the rest of it looks.
They are stops. In our own assessment they end the evaluation and turn it into a referral, and they do so before anything else is scored.
A patient under 18. Growth and growth modification are the orthodontist's specialty, built on three to four years of training beyond dental school, and we recommend that general dentists refrain from treating children and refer them.
Cleft lip or palate.
A skeletal discrepancy with a surgical indication. Tooth movement cannot resolve a jaw relationship that needs surgery.
An extraction case. The one exception is a lower incisor extraction.
Ankylosis. Trying to move an ankylosed tooth can start an external resorption process nobody intended.
Active periodontitis. Periodontitis that is not fully under control is an absolute contraindication, because orthodontic movement accelerates periodontal breakdown considerably.
A severe open bite, judged clinically at the chair and never from a photograph.
Most of these are visible in the first ten minutes of an examination. That is the point of putting them first.
How much crowding, rotation and overjet is still predictable?
In short: crowding above 8 mm, a rotation above 30 degrees, and an overjet above 6 mm you intend to correct each move a case out of the range where a general practice can expect a straightforward result.
Numbers are unglamorous, and they are the part of case evaluation that dentists most often carry in their heads instead of on paper. Ours are these.
Crowding of 6 to 8 mm makes a case moderate. Above 8 mm it becomes difficult, because the space has to come from somewhere, and every source of space is its own decision with its own risk.
Rotation is measured on the worst single tooth. Up to 15 degrees is predictable, between 15 and 30 degrees it is moderate, and above 30 degrees it is difficult on any tooth in the arch. Helle Hatt and Jesper Hatt set that single threshold in September 2026. It replaced a table of separate values for each tooth type, which turned out to be more than anyone can hold in their head with a patient in the chair.
Class II correction with an overjet of 4 to 6 mm lifts the case at least one level. Above 6 mm it is complex. Class III correction, when the dentist intends to correct it rather than accept it, is complex from the outset.
A crossbite that needs more than 2 mm of expansion is complex, and a thin biotype alongside it adds a recession risk of its own. If the root contours are visible through the gingiva in the mandibular front, the gingiva and the bone are thin, and the arch has less to give than the setup shows.
Anterior intrusion has one of the narrowest bands of all. Half a millimeter is predictable. Above one millimeter it is difficult, and where that line falls shifts with the aligner system, which is one of the few places brand actually changes the clinical answer.
If a case needs temporary anchorage devices, it is complex. That threshold is about what the aligner alone can carry.
Which findings must be resolved first without making the case more complex?
In short: apical pathology, an impacted tooth in the path of movement, a fixed bridge, bone loss and implants are all stop-and-resolve items, and none of them makes the aligner case itself more difficult.
This is the distinction that took us longest to get right, and it is the one that saves the most cases.
An apical infection has to be brought under control before any tooth is moved. An impacted tooth lying in the path of planned movement risks root resorption of the teeth being moved, so assess it and, where needed, remove it first. A fixed bridge splints its abutments into one unit that cannot be moved, so either plan around it or section it. Generalized bone loss may point to active periodontitis, which is a stop, so rule it out before loading anything. An implant cannot be moved at all, so it becomes fixed anchorage and the movements are planned around it.
None of these findings makes the aligner treatment harder once they are handled. Treating them as complexity is how a straightforward case gets refused, and ignoring them is how a straightforward case turns into a refinement sequence. They belong in their own column.
Where does the patient decide the risk?
In short: there are two factors in every case, the clinical situation and the mindset of the patient, and only one of them shows up on a scan.
One patient wants only the upper arch treated. Another has already decided how long this will take, and a third has had trauma to the front teeth and has not mentioned it. Each of them changes what the treatment can deliver without changing a single millimeter of the setup.
The clinical part of case evaluation can be written down as thresholds. The other part is a conversation, and it has to happen before the scan rather than after the plan comes back.
Why a threshold beats a feeling
In short: a written threshold can be argued with and revised, and a feeling cannot.
Every dentist who treats aligners has a sense of when a case is going to be trouble. That sense is real, it is built on cases you have finished, and it is also invisible to everyone else in the clinic, including the version of you who is tired on a Thursday evening.
Writing the lines down gives clinical judgment something to stand on. Our own thresholds have been revised repeatedly, because a line you can see is a line you can argue with. The AlignerService Risk Management System™ is exactly that: a set of stated positions about where risk starts, held by dentists and orthodontists, and changed when the cases give us reason to.
The woman from Tuesday morning may well be a straightforward case. With the lines written down, you will know before you order the setup.
Start with a Free Aligner Risk Check
If you have a case on your screen and you are not sure which side of these lines it falls on, send it to us. The Free Aligner Risk Check gives you a clinical assessment of complexity and the risks we can see, with an answer within 24 hours on weekdays. No obligation and no subscription.
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Kind regards
Jesper Hatt DDS
P: +41 78 268 00 78
