Biologic dynamics
The position of the teeth, bone and soft tissue are constantly adapting to the impact of muscle and function. Add to that, that even though you have created a perfect virtual plan and idealised it making it as predictable as possible, the teeth will constantly adapt to their surroundings. Which can be a challenge during a post-orthodontic restorative phase.
This blog post is about ortho-restorative treatment considerations in regards to retention in clear aligner treatments.
Once the patient reaches the last step in the clear aligner treatment process. It is most unlikely that the exact movements you planned in the virtual treatment plan have been achieved.
Need for additional aligners / a revision?
Clinically we see this challenge over and over. Expect the teeth to be ALMOST in the planned position once you reach the last aligner. In this situation evaluate wether the end position is ok or n ot. If not you will most probably have to do a new IO-scan and take some photos to plan additional aligners/make a revision.
The treatment is not over yet
With the teeth being close to their ideal position, it is advisable to think about how you want to work with your retention the following 6 month. In our opinion the treatment has not finished until you have achieved a stable occlusion, with a harmonious function with teeth that are no longer mobile due to orthodontic movements.
Retention - for how long?
Lifelong retention is necessary in order to keep the teeth in the right end position. The type of retainer you should choose depends largely on the tooth movements you have performed. Often, a bonded retainer on the 8 anterior teeth in the mandible will be a standard solution. But this is not always enough as it will not hold any posterior expansion in place. Just as it will not keep posterior teeth in place if they have been rotated during the aligner treatment.
Should there be room for the teeth to settle?
Right after the orthodontic movement of the teeth has finished, the periodontal ligaments will be longer than normal as the periodontal space is still enlarged. This increased space will enable the teeth to move quite a bit. Clinically this is visible as the teeth will be rather mobile.
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During this phase the teeth will be able to settle into a more refined occlusion or move into unwanted positions or relapse if allowed to. In addition the periodontal ligaments will return to a shorter length as the alveolar bone tightens around the roots.
It takes time for the body to adapt to the new situation. Since the biology differs from person to person, it is difficult to state exactly how long the initial settling phase lasts. Based on experience, we recommend the initial settling phase to last for at least 6 month. This gives the osteoclasts and osteoblasts time to remodel the bone to fit the new position of the teeth.
A lengthy phase of aligner treatment
Creating a retention plan can be frustrating, but also exciting and fascinating. Retention is often an overlooked, lengthy phase of orthodontic treatment.
If it involves removable appliances, occlusal and functional stability in combination with patient compliance. Which in turn requires considering how to communicate with the patient prior to any orthodontic treatment. Otherwise, you risk having to perform costly revisions years after treatment because the patient complains of a relapse due to their own inadequate use of a removable retainer.
Initial settling phase
During the initial settling phase, we have often seen teeth settle into the planned ideal position when using the last aligner for the 6 month period. We believe this is due to the fact, that although the teeth follow the planned treatment. They do not track 100% as planned.
By letting the patient wear the last aligner for 6 month, the teeth have time to settle into the planned position using the aligner as a settling guide (we typically order 3 extra aligners for this last step in the treatment).
Bonded retainers - be aware of this
If you choose to bond a retainer in place it will prevent the settling of the teeth into the clear aligner as the last aligner will no longer fit.
If you add a clear aligner on top of the bonded retainer, based on an IO-Scan of the final position prior to a settling period. The teeth will not be able to settle into the aligner with the planned final position of the teeth. This may be ok but it always depends on the clinical situation and should be evaluated individually in every single case.
Equilibration
Should you prefer to idealise the occlusion with a slight equilibration. You should avoid equilibrating the teeth for at least 6 month after starting the retention phase. This is because the teeth will potentially move quite fast during this period. If you equilibrate during this stage of treatment, you will most probably experience your efforts being useless as the teeth will move into a less favorable position while settling.
Ortho-Restorative treatment considerations
Should restorative treatment be performed immediately after orthodontic treatment?
Whenever we handle ortho-restorative cases it is important to think about retention throughout the entire treatment. Otherwise, there is a risk that the teeth will start to move a lot during the restorative treatment period.
As little as one or two days may be enough to induce a major relapse.
Challenges during ortho-restorative treatments
Usually we will move the teeth into an ideal position of the roots and the soft tissue. However this may lead to really bad looking shapes of the crowns and especially the incisal edges prior to the planned restorative procedure.
The bad aesthetics in the end of the orthodontic phase i an ortho-restorative treatment is often unwanted by the patient, which may force us to proceed with planned restorative procedures. Even though the teeth have not settled into their final position yet. In such a situation it is wise to consider how to retain the anterior teeth in their position.
Either with a bonded retainer - when we plan incisal edge bonding and veneers.
Or with an interconnected provisional that will be able to keep all the anterior teeth in place while waiting for the final restorations.
In situations with planned crowns or bridgework, it is of utmost importance to have a provisional that connects all the teeth between the preparation appointment and the cementation appointment as we need to retain the teeth in their position. If the teeth start to relapse during a provisional stage in the treatment. The final restorations will not fit and if you manage to make the porcelain fit, the occlusion will often be off.
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Provisional retention
Keeping the teeth in position with a provisional type of retention can be done in several ways. The most common is with a provisional alone or a provisional restoration in combination with a bonded retainer - either a permanently bonded retainer or a provisional retainer, that is bonded to the non-prepped teeth and the provisionals.
Avoiding a bonded retainer in this phase enables the use of the existing aligner as a retainer. Either by shaping the provisionals like the teeth you just preped. However by being a bit proactive it is possible to scan a waxup and order a retainer that fits the teeth with procisionals shaped like the waxup. This is often desireable when working on the anterior teeth as it enables us to evaluate the aesthetics of the final result based on the waxup. Instead of relying on the technician to deliver first class restorations based on a situation that never offered any verification in the mouth of the patient.
It is worth being aware that large provisionals can be tricky as the prepped teeth may start to move a bit within a provisional. Just as the teeth may move as the provisional material shrinks during polymerisation and thereby change the final position of the teeth - which will lead to challenges when the final restorations are to be seated.
Conclusion
Retention is a crucial phase in ortho-restorative treatments with clear aligners. Despite meticulous planning, exact tooth movements may not be achieved by the final aligner, often necessitating additional aligners or revisions. Lifelong retention is essential to maintain teeth in their desired positions, with choices ranging from bonded retainers to removable appliances depending on the treatment specifics.
The initial settling phase, typically lasting at least six months, allows periodontal ligaments to adapt and teeth to stabilize. During this time, using the final aligner as a settling guide can help achieve optimal positioning. Retention plans should be carefully considered to prevent relapse, particularly in ortho-restorative cases, where provisional retention methods can ensure teeth remain stable until final restorations are completed.
By staying proactive and employing effective retention strategies, practitioners can significantly reduce the likelihood of costly revisions and ensure lasting treatment outcomes. Sign up for our blog for more insights, tips, and tricks on clear aligner treatments. As a member of the AlignerService site you get notified 1-2 times a month, when we publish new posts.
Sincerely
Dentist, co-founder & business advisor
Jesper Hatt DDS
Phone: +41 78 268 0078
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