Lingual Orthodontics – The Renaissance

The Second Coming
After 30 years in relative obscurity, lingual orthodontics is finally coming into its own. New technologies have swept through the specialty, bringing changes to the way traditional orthodontics is practiced. Developments in CAD/CAM, rapid prototyping and robotics have created novel treatment modalities, such as clear aligners (InvisalignTM) and breathed new life into older techniques, such as lingual orthodontics. This in turn has opened the possibility of orthodontic treatment to new populations of potential patients.

1. Typodont of “Incognito™” lingual appliance. 3M Unitek.

Originally conceived more than 35 years ago, lingual technique was orphaned by the larger orthodontic community when technical obstacles in bracket design and clinical technique proved too difficult to overcome.

With the advent of these new transformational technologies, the original promise of the lingual concept has met with the reality of new manufacturing and clinical techniques. Lingual appliances can finally deliver on the early promise.

The Long Road Back
The original lingual appliance designs relied on difficult and exacting laboratory setups to adapt brackets and wires to the lingual surface. In most cases, these were stock labial brackets or modified prefabricated designs that were manually applied by technicians. To compensate for the variable lingual topography, unique to each patient, technicians used specially designed surveyors to build-in torque, tip and angulation into the bracket set-up. With such a straight wire arrangement, flat pre-fabricated wires could be inserted without the need for placing complicated bends. Unfortunately, this was a lengthy and laborious multistep process that introduced a host of inaccuracies at considerable expense. In practical application, all manner of obstacles presented themselves. Paradoxical response to forces, the challenges of limited inter bracket distance and visibility all added to a steep learning curve that limited the appliances appeal. Patients found the first generation of brackets bulky and awkward with many experiencing difficulty with speech and tongue irritation.

2. Early lingual brackets required a technician intensive laboratory service to setup lingual cases.

Despite a promising introduction, the early experience with lingual appliances was difficult for clinicians and patients alike. The arrival in the late 1980s of clear ceramic brackets turned the collective attention for aesthetic solutions elsewhere, effectively closing this chapter in North American practices. Most orthodontist abandoned lingual appliances in North America by the late 1980s. Elsewhere, lingual technique did not arrive in some cases until 10 years after its initial launch and demise in North America. In Europe, Japan and South America, old bracket designs were updated, new ones were developed and expertise with lingual technique grew to encompass a large community of users.

3. Early ‘TARG’ surveyor designed for manual setup of lingual bracket prescriptions.

What’s Different This Time
Europeans have led the field in developing new lingual appliances. The first of the new generation of fully customized lingual appliance ‘system’ was dubbed the “Incognito™” appliance. Developed in Germany from 1998 to 2004, this technology was recently acquired by 3M and it continues to be developed and refined today. It remains today the oldest and most mature of the custom lingual bracket systems. Newer systems with novel self-ligating brackets “(Harmony™”, American Orthodontics) have also been launched recently.

What makes this new generation of lingual appliances special is that it allows each patient to have a customized appliance (base and bracket) with a custom prescription, unique to each patient and tuned specifically to the need of each malocclusion. Complementing robotically bent custom arch wires complete the appliance ‘system’. The result is a sleek, precise and effective appliance that maximizes patient comfort and vastly improves appliance utility for the clinician.

Fabrication begins with a digitized replica of the dentition obtained from PVS impressions or a digital oral scanner. Once digitally rendered as a virtual dentition, the technicians can accurately navigate and map the surface contours with specialized software. Once the doctor has directed and established the parameters, the technicians model a digital setup that establishes a simulated treatment outcome. Digital brackets can be manipulated into ideal positions, incorporating the doctor specified torque, tip and angulations and affixed to the custom bases designed to hug the lingual topography. The virtual brackets are converted to actual wax duplicates by a digital printer and these are attached to sprues and covered in an investment material to be cast like conventional gold restorations. Once separated and polished, the brackets are imbedded in a firm tray material and are then ready for indirect bonding.

The entire fabrication process from impression to finished bonding trays spans four to six weeks. The end result is an easy to apply, extremely accurate (+/– 1/1000th”) and integrated ‘system’ designed with pre-programmed wires to deliver an outstanding outcome.

With such industry leading tools for design and production of sophisticated orthodontic devices, lingual orthodontics has finally entered the digital age; volume production of customized treatment outcomes.

4. Topographic map of the lingual surface of a central incisor. A difficult and variable surface to which to adapt a ‘stock’ bracket.

Why Lingual and Why Now
The demographics of orthodontic practices has changed significantly in the last 15 to 20 years. Adults make up a much larger percentage of the orthodontic population and the average adolescent and adult patient is far more demanding of an aesthetic choice in treatment. Most are clear that they would rather choose a solution that does not compromise confidence in their appearance. Both clear labial brackets and clear aligner appliances have un
til recently been the only choices that most clinicians had to offer. In many case, these appliances would serve well. However, there remain a significant number of patients that simply refuse to accept anything visible on the exterior of their teeth. For others, the clear aligner solution is beyond reach due to the severity of their malocclusion. Others are committed to sports or play musical instruments where labial appliances are too obtrusive. Whatever the obstacles, a significant number of the patients we serve are left to choose between appliances that are either a source of embarrassment or are poorly suited to treat their malocclusion. Faced with these awkward choices, they often avoid treatment altogether.

5. The newest generation of self ligating digitally customized lingual brackets. “Harmony™” by American Orthodontics.

In this aesthetics conscious age, Lingual is a welcome alternative to the conventional fixed or clear aligner choices.

How Lingual Orthodontics Compares
Fixed Labial Systems:
Lingual treatments share many features with conventional labial systems; largely equivalent treatment times, similar levels of control of 1st, 2nd and 3rd order mechanics. The general treatment experience is much the same for patients with labial or lingual braces. Lingual braces require an initial brief period of accommodation to speech and comfort. However, the newest appliance designs reduce this to a non-issue in a matter of a few days or weeks.

6. “Incognito™” by 3M Unitek.

Maintaining oral hygiene is a problem with any fixed appliances. With lingual appliance, the facial tooth surfaces are always easily available for cleaning and never at risk from decalcification.

When finishing in lingual, the clinician benefits from an unencumbered view of the labial profile of the tooth and the adjacent soft tissue contours free from the common gingival hypertrophy and obstruction of wires and brackets. This visibility is helpful with multidisciplinary teams where colleagues can accurately preview case progress and team-up with the orthodontist to steer the finishing phase of pre-prosthetic or pre-perio treatments.

7. “Incognito™” fabrication with 3D digital wax printer.

Clear Aligners Systems:
‘Invisalign™, Clear Correct™, Clear-line™ as well as similar aligner systems, have been adopted by a large numbers of dentists to provide a simple aesthetic treatment option to patients. Programmed to deliver orthodontic movement in preplanned steps, they remove much of the stress and effort from treatment planning and management.

Aligners share the advantages and disadvantages common to most removal appliances. They offer very good aesthetics, good anchorage control and easy removal for oral hygiene and selected activities. They are particularly well suited to simpler mal-alignments and ‘tip-and-tweek’ orthodontics.

8. Robots fabricating custom lingual wires.

However, they are challenged and their reliability suffers where malocclusions require vertical control, rotational correction and root movement. Extraction and surgical treatments are largely beyond the ability of most aligner treatments and tooth translations in excess of 2 to 3 mm are problematic. Similarly, aligners are not indicated in the mixed dentition.

The development of increasing complex ‘attachments’ and advanced computer treatment algorithms have improved aligner performance at the cost of increasingly fussy bonded labial attachments. Many of these ‘enhancements’ work to degrade the aesthetics advantage that made clear aligners so popular.

9. It all begins with the digitized tooth anatomy.

Despite all the advances in design these appliance retain the generic limitations inherent in most removable appliances; patient compliance, limited appliances. Reluctantly, aligner treatment providers have come to accept that 20 to 30 percent of cases will require additional remedial ‘refinement’ treatments. In contrast, lingual appliances can deliver a reliable, adjustable and predictable course of treatment for patients of all ages and malocclusions.

10. Technicians digitally drawing a custom bracket base.

The Lingual Advantage
Lingual appliances are easily combined with either labial braces or with Invisalign treatment in opposite arches. Most commonly, this is done in the mandibular arch, whilst utilizing lingual appliances in the maxillary arch. It often allows for combining the best characteristics of each appliance whilst limiting complexity and costs.

11. Computer generated wire arch forms.

Lingual systems offer unparalleled aesthetics. Invisible, in the true sense with nothing standing between the teeth and the patient’s smile.

12. Lingual brackets cast from printed wax models.

13. Custom indirect bonding tray.

Challenges of Lingual Technique
The nature of lingual tooth morphology limits the amount of available area for the lingual bracket ‘footprint’. In patients with very small teeth, this limiting factor can determine whether lingual appliances can effectively be employed.

14. Invisalign tray.

15. Lingual technique finds easy application in the mixed dentition.

16. Mixed appliance treatment with upper lingual and lower labial brackets is popular.

Treatment with lingual appliances still demands that the clinician acquire a knowledge base built of hand skills and experience, for which there is a significant learning curve. This is a clear limiting factor in the adoption of lingual technique. Many practices find it difficult to delegate the time, extra staff and resources needed to implement lingual systems in a busy practice. Not surprisingly, many orthodontists take on a few cases and quickly find it does not suite their practice ‘style’. Compounding this is the difficulty in delegation of routine tasks to auxiliaries. Few have the training to take on commonly delegated tasks requiring skills unique to lingual. With limited patient numbers, experience to gain competence with such tasks is hard to acquire.

17. Class I crowded; before Tx.

18. Class I crowded; after 14 months Tx.

Lingual does demand more chair time for patients. This can limit its appeal in practices unaccustomed to a lingual focus in their clinical routines. The added time to tie in wires and make adjustments can double, and in some cases, triple the usual time patients inhabit the dental chair. This valuable time can become a serious ‘speed-bump’ in busy practices trying to accommodate the after school rush.

19. Anterior openbite; before Tx.

20. Anterior openbite; after 14 months Tx.

In circumstances where patients have to transfer out of a practice and find themselves in more remote areas, they may find it difficult to locate a clinician knowledgeable enough in the lingual technique to carry on treatment. Unfortunately, despite the passing of 30 years, the number of clinicians with active lingual practices is limited but still growing in North America.

The combination of added chair time and state-of-the-art laboratory services combine to make treatment fees higher for most lingual cases. An informal survey amongst colleagues puts this premium in a range from 10 percent to 50 percent more than a comparable treatment in either conventional labial or clear aligner appliances. In our experience, this has not been a common barrier to acceptance but can be an obstacle for some patients.

21. Surgical class III; before Tx.

22. Surgical class III; after 19 months Tx.

Future of Lingual Technique
Just as clear aligner therapy has established itself as a staple of the orthodontist and dentist, there is a clear place for lingual technique in the orthodontic armamentarium. Its appeal to patients is self-evident when it is offered as an alternative, on par with labial and aligner therapies. And for those patients whose needs fall between the spectrum of clear labial braces and aligner therapies, lingual appliances can present as the treatment of choice.

23. Class II crowded; before Tx.

Adoption of the technique by the larger orthodontic community has so far been limited. Much of this can be attributed to the collective memory of older clinicians that remember the ‘hard times’ and the difficulties with the older technology. For other younger orthodontists, effective comprehensive training in this technique is generally not available in North America. Even without these limiting factors, wider acceptance is likely to remain slow because of the other barriers mentioned earlier; longer chair time, demanding technique, limited resources, costs, etc.

24. Class II crowded; after 16 months Tx.

The next generation of lingual appliances continues to evolve and develop with a steady parade of new lingual ‘systems’ coming on stream. This ongoing evolution promises to continue the lingual “renaissance”.OH

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Dr. Anthony Strelzow is a certified specialist in Orthodontics and maintains a practice in Vancouver B.C., and Whitehorse, Yukon. His Vancouver practice is limited to Lingual and aesthetic appliance treatment. Dr. Strelzow has been practicing Lingual orthodontics for 30 years and teaches Lingual Technique at the post-graduate department of U.B.C. He is also on staff at Vancouver General Hospital. Dr. Strelzow teaches and speaks about lingual and aesthetic techniques extensively and maintains several dedicated websites. He can be reached at www.OrthoArts.ca.

The author wishes to thank 3M Unitek, American Orthodontics, Align Technologies and Specialty Ortho Labs for providing images used in this article.

Oral Health welcomes this original article.