Perspectives on Aligner Therapy

Spurred by innovations in technology, rising demand for clear aligners is leading more offices to embrace this esthetic therapeutic option. For insights into this treatment approach, we asked Ricky E. Harrell, DMD, MA, program director for the Georgia School of Orthodontics, for his perspective on developments in orthodontic aligners.

Interest in clear aligners isn’t hard to understand. With recent innovations broadening the scope of  what can be treated with professionally supervised aligner therapy, patients and practitioners alike appreciate the advantages of shorter treatment time, easier maintenance, and an esthetic appearance that traditional orthodontic appliances simply can’t match.

What are some of the drivers behind the increasing popularity of clear aligners? 

Esthetics is one of the main drivers behind the increasing popularity of aligner therapy. With this approach, not only are the results of treatment more esthetically (as opposed to functionally) oriented, the method by which the results are achieved also has to be more esthetic — and that appeals to patients.

In addition, clear aligners offer some advantages over fixed appliance therapy. First, there is less need for appliance maintenance with aligners than with fixed orthodontics. For example, there is no need to repair broken brackets or poking archwires. Aligners also don’t pose issues with ungoverned tooth movement. By this I mean the aligners themselves are self governing; that is, a specific set of trays can only accomplish the tooth movement that was programmed into them. Compared to traditional appliances, they cannot continue tooth movement unabated — even without maintenance. This is not true for numerous situations when using fixed appliances. 

Additionally, oral hygiene is easier to maintain during treatment with aligners than with fixed appliances. We do not see the patterns of decalcification with aligners as we do with fixed appliances. The ability to remove the appliance for oral hygiene measures remedies some of the most difficult issues associated with fixed appliance therapy. 

Advances in technology and the ability of the appliances themselves have increased the scope of what can be treated with aligners as well, so they have become more attractive to the practitioner and patient. Today’s aligners are not what they were 15 years ago.

And during the height of the COVID-19 pandemic, it became popular among some practitioners to conduct virtual appliance checks, as opposed to in-office visits for supervision. There are devices on the market that work with smartphones to allow the practitioner to remotely evaluate tooth movement with aligners. If the teeth are not responding or “tracking” as predicted, the patient can be called into the office for an in-house evaluation and correction. This has made the provision of care safer for both the patient and dental team. 

What factors should clinicians consider before adding clear aligners to their practice offerings?

As an orthodontic educator, one of the biggest concerns — especially among general dentists considering aligner therapy — is the lack of understanding of orthodontics and the limitations of tooth movement. Without sufficient knowledge of these two key elements, treatment is often destined to fall short of the anticipated outcome. 

Compared to many dental procedures, orthodontics generally requires more documentation for treatment. Most general dentists rely upon radiographs and clinical examination/​evaluation to assess treatment needs. In orthodontics, radiographs of the teeth and surrounding bone — most often a panoramic radiograph, as opposed to a full mouth series — are just a portion of the diagnostic record. Very few general practices have the capability to produce a cephalometric radiograph — which, as an orthodontic provider of almost 40 years, I believe is absolutely necessary to plan safe tooth movement. 

So, a key question for the clinician is whether the practice is willing to invest in the technology to obtain adequate documentation before any tooth movement is contemplated, much less attempted. For example, while some aligner companies can produce models for aligner fabrication from conventional impressions, the preferred method is from submission of digital patient files produced with an intraoral scanner (Figure 1). Drilling even deeper into this, some of the aligner companies also dictate which scans they will accept, meaning, they are brand specific regarding scanner technology. 

Broadly speaking, in which types of cases is clear aligner therapy indicated?

For most general practitioners, treatment should be limited to mild-to-moderate Class I malocclusions for correction of rotations, mal­align­ment, and cosmetic changes. It is important to understand that malocclusions are very effective at disguising an underlying skeletal element. For example, a Class II malocclusion may present with a deep overbite. Upon further examination, the depth of overbite may result from hypereruption of an unopposed mandibular anterior dental segment and the teeth erupted until they met resistance from the palate. This can disguise a hyperdivergent skeletal pattern, and if the provider is unaware of the underlying skeletal issue, he or she can unmask the skeletal discrepancy with leveling of the curve of Spee, thereby creating an open bite that is not amenable to orthodontic correction, regardless of the appliance system utilized. 

As noted, general practitioners generally do not have cephalometric imaging capability in their offices, and most do not have the training for appropriate cephalometric evaluation. This is not said to discourage anyone from treating a patient if the clinician feels comfortable and competent in doing so. Rather, it is to make practitioners aware that the initial clinical evaluation is not necessarily reflective of the underlying bony bases, and their position relative to each other and the cranial base — and that can have very significant implications in the clinical outcome. 

Conversely, in which situations is this modality an inferior choice to traditional orthodontics, or perhaps be considered an approach that should be limited to highly experienced clinicians? 

In today’s practice, clinicians highly experienced in aligner therapy are treating some fairly difficult cases. Extraction cases (which, by the way, are still necessary with or without aligner therapy in consideration) were once rarely treated with aligners, but are now more routinely treated in this fashion, especially a mandibular incisor extraction case. The bodily tooth movement (translation) necessary in extraction cases is difficult to achieve without fixed appliances, but some providers are able to produce acceptable results with aligners in these situations. 

Patients with conditions requiring orthognathic surgical correction, where there is an underlying skeletal issue, are occasionally treated with aligners. Often, aligners will be utilized for presurgical tooth movement, and then fixed appliances will be placed right before and during the surgical process. Afterwards, the fixed appliances are removed and the case is completed using a new set of aligners. Ultimately, the thing to remember is that guidelines for surgical preparation with regard to tooth positioning remain the same — regardless of whether aligners or fixed appliances are used. 

One area in which fixed appliance therapy is generally more effective than aligner treatment is in managing mild-to-moderate skeletal discrepancies. With fixed appliances, skeletal expansion in young, adolescent, and sometimes adult patients (if a miniscrew-assisted rapid palatal expansion protocol is utilized) is possible. Because aligner trays are fully tooth supported and deliver a low level of force, skeletal expansion is not possible, as is the case with fixed appliances. That said, there are case reports where traditional expansion appliances are utilized in the beginning of treatment to affect the expansion, after which remaining tooth movement is accomplished with aligner therapy. 

In terms of the patient and practitioner, what are the pros and cons of clear aligners compared to traditional orthodontics?

For the patient, aligner therapy offers a convenient alternative to fixed appliance therapy — provided the treatment needs are amenable to correction by aligners. The esthetics are obviously superior to those afforded by labial fixed appliances. Office visits can be reduced, which makes it more convenient for the patient. Decalcification, as experienced with fixed appliances, is minimized — although soft tissue problems and hygiene still must be monitored with vigilance throughout treatment. Additionally, as the scope of what is considered treatable with aligner therapy broadens, patient convenience will only be enhanced. 

One possible downside to aligner therapy is that patient cooperation is essential. Without the aligners being worn as prescribed, the result will not necessarily reflect the anticipated outcome. What’s more, noncompliance not only produces inferior results, it takes longer to achieve these substandard results.

Although fixed appliances can be utilized to manage almost all orthodontic situations, aligners cannot make the same claim, so their range is more limited. On a cautionary note, like fixed appliances, aligners are also capable of moving teeth right through the cortical plate, so clinicians are advised to closely monitor treatment.

As noted earlier, any provider of orthodontic treatment must understand the limitations of tooth movement — and this is true when using either clear aligners or fixed appliance therapy. 

In practice, many of the same benefits of aligners apply equally to providers and patients. Clear aligners offer better esthetics during treatment, require less frequent maintenance visits, offer easier hygiene care, and help reduce decalcification associated with orthodontic treatment.

The downside to practitioners must also be carefully assessed. Many, but not all, aligner companies will require an intraoral scan, which, in turn, requires a significant investment in equipment for the provider. As noted, the scope of treatment that can be provided with aligners is limited compared to fixed appliances. The cost of the appliances themselves is a significant portion of the overhead associated with treatment. There is also a time lapse between submission of the case for fabrication of the trays and actual appliance delivery. This can interfere with scheduling, especially with the “same-day-braces” practices utilized in some offices. 

For practitioners who decide they can fabricate their aligner appliances in-house, one must invest in scanners, computer systems, three-dimensional printers, materials, and personnel who can manage sequencing of tooth movements, as well as physically produce the aligners. Obviously, this significantly adds to overhead costs associated with treatment. 

Clinicians highly experienced in aligner therapy are treating some fairly difficult cases

For general practitioners who offer clear aligners, when is referral or collaboration with an orthodontist recommended?

In terms of a general practitioner who provides aligner therapy, there is not much scientific evidence on what should be referred to an orthodontist for treatment. For most general practitioners, treatment of Class I dental malocclusions with mild crowding would fall into their purview. For malocclusions with a moderate or significant skeletal component (which is much more difficult for a general practitioner to ascertain), referral to an orthodontic specialist would be recommended. 

I would also recommend consultation/​collaboration with an orthodontist anytime the general practitioner realizes treatment is not progressing as expected. 

In your estimation, why is do-it-yourself aligner therapy ill advised?

Do-it-yourself aligner therapy is simply bad medicine. That is both an assertion based on my clinical experience and also the title of a guest editorial I wrote for the March 2020 issue. [Editor’s note: “Do-It-Yourself Aligner Therapy Is Bad Medicine” is available at decisionsindentistry.com.] From an overall health standpoint, dentistry is an integral part of comprehensive healthcare and should be accessible to everyone. When we do not incorporate oral screenings and examinations into the treatment flow, we create the opportunity for conditions of pathology and disease, both oral and systemic, to remain undiagnosed.

From the dental perspective, do-it-yourself aligner therapy is almost universally done without radiographic examination and precludes assessment of:

• The condition of alveolar bone and housing
• Presence of disease within the bone that is not visible upon examination of the oral cavity and surrounding structures 
• Status of the roots of teeth
• Position of unerupted teeth
• Potential loss of root structure due to inappropriate tooth movement

For the public to be led to believe that a technician or dentist-supervisor in a remote location can assess oral and orthodontic conditions as well as a trained practitioner who physically examines the patient is both deceptive and unethical. This is not a play by dentists to capture the aligner market; rather, it is a professional commitment to ensure the delivery of safe and effective care (Figure 2). 

As a profession, I do not believe most dental teams do an adequate job of conveying this point to patients. Ultimately, only through understanding the core principles of tooth movement and planning appropriate treatment can dentists hope to harness the increasingly sophisticated capabilities of aligner therapy. 

The author has no commercial conflicts of interest to disclose.

From Decisions in Dentistry. August 2021;7(8)14-17.