A great orthodontic treatment with the Invisalign technique starts with a great ClinCheck plan, which is why it is important to have a deep fundamental knowledge of the system and its pillars of success.
That said, during any treatment there will be changes from the original planning, as with brackets in the past, where we used auxiliary techniques, rebonded brackets, used coil springs, auxiliary root torque devices. We should therefore expect to face similar challenges with aligners: these issues can be resolved either by asking for additional aligners or by following our troubleshooting tips and finishing strategies.
16.1 Auxiliary Techniques
Auxiliary techniques will be required when there is a fitting problem, which might be caused by a bad treatment plan, patient biology or poor patient compliance:
- If it is less than 1 mm: this means there are blue or black movements or patient compliance is low, and so the patient should be asked to wear the aligners for a longer period (10–14 days)
- If it is between 1 and 2 mm: use detailing plier (anterior rotations and in/out movements) or auxiliary techniques (posterior rotations, extrusion, root tipping)
- More than 2 mm: scan again
In order to achieve a successful orthodontic treatment, we need to know how to troubleshoot and solve the complications as they arise. Complications commonly encountered with aligners as described below.
16.1.1 Tooth Does Not Follow Rotation Movement
When there is a gap between the aligner and the incisal edges of the teeth or a space around the attachments upon insertion. There is a discrepancy between the tooth position in the aligner and intraorally; the tooth is more rotated in the mouth than in the ClinCheck.
This might occur when there has not been enough compliance and the patient has changed the aligner before the full movement has been completed. One possible solution is to revert to previous aligners and attempt to recover the movement. Try the aligner that best fits and continue the treatment from that aligner.
Another possible cause of a discrepancy between the tooth position and the aligner is that in the software this tooth has started to move before enough space has been created or the clinician did not perform a sufficient amount of the prescribed IPR. To correct the rotation of an incisor, use detailing pliers.
At this point we should stress the importance of asking the technician to make sure there are open contacts mesial and distal to any rotated or lingually positioned tooth. Be especially careful with rotated second premolars rotated and lingual lateral incisors, as the default staging in the software is to move teeth simultaneously, which is not predictable. To increase predictability, we suggest restaging the rotated tooth movement to create space first before moving it into alignment.
In canines that have rotation and tipping problems at the beginning of the treatment, if the software tries to solve the problem of the rotation and root tipping simultaneously, a discrepancy between the canine position and the aligner will appear. To solve this problem, buttons linked with a Powerchain can be used, performing IPR mesial and distal to the canine and maintaining the same aligner until the position of the attachment inside the reservoir of the aligner is corrected.
16.1.2 Tooth Does Not Follow Vertical Movement
A common cause of intrusion is lack of space. If teeth collide into each other, even if they receive the required force to move, they cannot reach their final position and they become intruded.
In order to prevent the intrusion of the teeth, check the contact points with dental floss at every appointment and if they are found to be tight, perform slight IPR to ensure the teeth have space to move.
Extrusion issues may also be encountered during the treatment which may be resolved easily using the tips provided here.
Auxiliary Technique to Extrude a Lateral Incisor
There is a common auxiliary technique to extrude a lateral incisor that has become intruded during the treatment.
- The aligner has to be trimmed on the buccal and lingual sides to allow the tooth to extrude
- It is important to ensure that there is enough clearance between the button and the edge of the aligner: 4.5 ounces, 3/16’ elastics can be used to extrude the tooth, placed from the buccal to the lingual button
When there is an ectopic canine, this must be virtually eliminated to avoid tracking problems and the ectopic canine will need to be guided its final position using extrusion elastics once space has been opened for it. In these cases, the prescription from the practitioner will be used to request that the technician places a large pontic that overlaps the lateral incisor in order to provide space for the ectopic canine.
- After opening space for the canine, extrusive elastics may be used to extrude canines into the virtual pontic
- Buttons can be used on both the buccal and lingual surfaces of the canine to extrude them
- The pontic must be trimmed to avoid interference with eruption of the tooth
- Once the canine has erupted, a new scan is taken to include the newly positioned canine and additional aligners are requested
16.1.3 Managing Root Tipping
This is another important aspect in extraction cases and is performed during these treatments or in cases of agenesis in order to properly close spaces and re‐establish occlusion.
Uprighting a Molar Root
The patient shown in Fig. 16.7 presented with severely tipped molars in the right and left mandibular quadrants after previous orthodontic treatment. Molar uprighting was built into the aligner assisted by TAD mesial to the molars and sectional wire from the molars to the microscrew.
The patient shown in Fig. 16.8 had a mesial tipping of the second premolar root. A power arm was used to upright the root of the second premolar, with a power chain from the power arm to a button on the second molar.