Roughly 20 years have elapsed since the commercial introduction of the first clear aligners and today they are an established and well accepted treatment modality. Not many remember but back in the early 2000’s, the Invisalign® device was greeted with much skepticism and doubt. A great deal of clinical work and marketing efforts were needed to convince the orthodontic community that this method is here to stay. Today, in many cases, aligners have become the preferred treatment option for clinicians and patients alike.
Reviewing and Revising an eXceed Aligner Plan
Dr. David Arias, Clinical Manager, eXceed
The objective of this article is to providesome basic guidelines and recommendations regarding the review and revision ofeXceed 3D aligner plans.
A. Pre-treatment Review
The first thing to do when opening the plan is to check the initial occlusion, to verify that there is no discrepancy between the 3D bite and the actual bite of the patient.
If we take occlusal photos of the patient with articulating paper marks, we can compare theimages against the occlusogram to verify that the teeth are occluding as in the picture.
To mount the model, two options are available:Maximum Intercuspation or Centric Relation. Please keep in mind that if we want to treat the case from Centric Relationship, that position should be captured in the scan or bite registration/ Layer, the aligner design teamshould be informed that this is how the case should be mounted and Images of such patient need to show maximum intercuspation and centric relationship.
Next, we verify in the patient’s charts whether he/she is canted, and then ensure that the plan has the same occlusal plane. One way to do it is to obtain a photo of the patient biting horizontally a tongue depressor to examine if the plane is canted or simply to use the device Fox Plane.
The occlusal plane of this model is canted, with the right side higher than the left. This condition must be verified clinically with the patient, to decide whether we want to improve the condition or maintain it.
In addition, gingival levels must be checked, since this is how the aligner will be trimmed. This is done only when the patient has significant gingival recession so in that case, we can opt for shorter or taller aligner trimming style.
Using the grid function, at this stage, one must evaluate the initial overjet, overbite and Anterior-Posterior position, providing instructions to the eXceed team on the necessary corrections in millimeters.
Returning to the occlusogram, it can also provide valuable information about the patient’s bite and any initial interferences. The color scheme is easy to understand: Blue indicates a very light contactwith teeth probably notoccluding; Green and yellow represent ideal contacts whereas Red and Brown stand for heavy contacts
The occlusogram includes a pattern of colors demonstrating how and where the patient is biting
A. Post-treatment Review
In the next stage, final tooth position in the aligner plan must be evaluated. It is quite important to check the plan alongside the patient facial and intra-oral photos as well as panoramic X-rays, to better understand how anticipated movements will affect facial aesthetics.
For example, if extrusion or intrusion are planned in the anterior region, the smile line will be affected. We therefore need to have the matching images to ensure the smile line will be improving.
In deep or open bite cases, it is almost always recommended to start with vertical anterior movements. To improve the profile in the next step, we should also move the posteriors. Some open bite patients have a habit, so it is important to have it resolved prior to commencing the aligner’s therapy.
This open bite case is solved mainly with anterior extrusion as we wish to avoid modifying the vertical dimension. For this reason, the posterior teeth are not going to be intruded. Please note that for extrusion movements we need to use horizontal rectangular attachments that will help us to obtain the desired vector. Extrusion is probably the movement that is most difficult to obtain without the use of attachments.
Crowding can be treated in five different techniques: 1. Expansion; 2.Proclination (lingual root torque); 3. Inter-poximal reduction (IPR); 4.Distalization; or 5.Extractions
Anterior-posterior relationship may be improved by means of the following methods: 1) Distalization, made easier with the removal of third molars and use of elastics. It is advisable to use sequential movements even if they increase the number of aligners; 2).Posterior IPR; and 3). Mesialization, which is less predictable due to the need to create space;4). PremolarsExtraction and; 5) Virtual bite jump using elastics.
This Class II case demonstrates the use of the virtual bite jump. This module will simulate in one stage the effect of the elastics during the whole treatment, assuming full compliance and sufficientwearing time. In the aligner plan, the teeth will begin alignment and leveling until the final stage, at which point the simulation will show the jump of the mandible to obtain a correct occlusion.
When there are issues of tooth size discrepancy resulting in heavy anterior contacts, this can usually be treated by: 1)IPR of lower incisors; 2)leaving spaces for restorations on upper arch;or 3) Lower incisor extraction.
Looking at the simulated post treatment model, we need to ensure that the conditions mentioned earlier have been resolved. In addition, one should consider the following:
1) Arch shape: a distance of 35 to 39 mm between upper first molars is recommended. Buccal corridors should also be evaluated to see if expansion is affecting the patient’s smile
2) Leveling: placing emphasis on the curve of Spee.
3) Torque: Upper incisors must be verified to have a positive torque of around 6 degrees and lower incisors at neutral torque or even minus 1 degrees.
4) Angulations: crowns should point mesially and roots distally.
5) Overbite: ideally should be around 2mm with 0.5mm overjet.
If IPR is indicated in the treatment plan, it’s important to know how much and at which stage it is needed. It is essential that the IPR be performed at the prescribed stage, not later.
When clicking on the IPR command in the eXceed software, all teeth requiring IPR are shown. A second click will show the cumulative amount of IPR and in which stage it is needed. In this example 0.4mm of IPR needs to be done before stage number 4, otherwise tracking issues will be developed.
As part of the case submission to the eXceed Planning team, it is important to always specify how the clinical condition is to be resolved and the amount of desired movement.
Next, examine the occlusogram, ensuring heavy contacts are found only in areas where they need to be. For example, when opening a deep-bite by extruding the posterior teeth, one can leave heavy occlusal contacts on the molars and premolars to ensure the bite will further open.
Lastly, evaluate the attachments and request any changes according to clinical preferences.
A. Simulation and Movements’ Review
In the third and final stage, the simulation and the amount of movements are to be evaluated.
To start, one must ascertain whether the movement is simultaneous or sequential. Simultaneous movements decrease the number of aligners but at the same time also reduce treatment predictability. If for example, the 3D simulation portrays large expansions, it is important to return to the photos and see if there are any recessions. If that is the case, then IPR may be required to avoid increasing them even further.
At the same time, it is important to note the amount of movement necessary, to figure out if that is possible with aligners only or whether auxiliary techniques may be required.
This is also important so that the patient may be advised about the possibility that elastics or attachments may be employed during the treatment.
In general, to ensure a more predictable treatment, one should try and strive for:
a) Rotations that are less than 15 degrees in posterior teeth and less than 30 degrees in anterior teeth.
b) Translation movements of around 2mm.
c) Vertical movements on anterior teeth of around 2mm.
d) Vertical movements of posteriors teeth of around 0.5 – 1mm.
When mesialization is used, the key is to first create the space and only then to mesialize. Please remember that mesial or distal changes on the upper arch can be secured more easily relative to the lower arch. In general, it is highly recommended to combine several movement options to increase predictability.
A precondition to placing any attachments is the absence of any interferences with the upper arch, so that enough space is available to bond them on the patient’s teeth. If not, the attachment may be moved to anadjacent tooth, depending on treatment objective.
Please keep in mind that with aligners, the most important goal is usually to create space to allow the teeth to move. If we review in the simulation that a tooth is moving but there is not enough space it is better to revise the case and ask the eXceed Team to expand or procline first or to do IPR.
Note tight contacts between teeth 7-8. If rotation is prescribed, a collision is likely to be developed and therefore a tracking issue. In this case it is better to first expand the tooth 8 and only after the space is generated the rotation can commence.