Beginning with the End in Mind by Dr. Thomas S. Shipley

Using high-frequency vibration in orthodontic retention

by Dr. Thomas S. Shipley

Retention can be a frustrating process for orthodontists and patients alike. Relapse occurs for many reasons, ranging from patients who don’t replace their broken retainers to those who are simply noncompliant. Studies have shown that 40 percent to 90 percent of orthodontic patients have unacceptable dental alignment 10 years after treatment.1 Based on these statistics, there’s certainly room for improvement in this important aspect of orthodontic treatment. Therefore, when choosing our retention strategy and appliance, basing it on the individual and retention science can contribute to preserving a lasting and stable occlusion.

One of the reasons retention is difficult to maintain is because of the length of time it takes for the teeth to be adequately “settled” in their new positions. Pratt et al. noted that while retention varies based on tissue types, generally reorganization of the periodontal ligament occurs over three to four months, the gingival collagen–fiber network takes approximately four to six months to remodel, and the elastic supracrestal fibers remain deviated for more than seven months. The article notes that this reorganization phase is completed usually within a year of debonding.¹

Bone-density changes occur during and after orthodontic treatment, as well. Yu et al. noted a 23 percent reduction in bone-mineral density around treated teeth after a seven-month period of active orthodontic treatment. After a two-year retention period, most patients’ alveolar bone density recovered; however, bone density around approximately 10 percent of teeth failed to recover to even 80 percent of its pretreatment state.² This stresses the importance of the second phase: post-retention, lasting for the rest of the patient’s life.

The re-treatment dilemma
When patients present with significant relapse from treatment years ago, they most likely require comprehensive re-treatment, and are now motivated toward lifetime retention. However, when a patient returns just months after completing active treatment with relapsed crowding or rotations, and often a broken (or lost) retainer, the frustration is real—for both parties. The adult patient may have been too busy to reschedule, with relapse occurring quickly. For younger patients, research shows that until age 25, the brain is still developing the ability to process risk/reward and long-term consequences.³ So adolescents often don’t fully understand the significance of strict early retention compliance.

In situations like this we are faced with a dilemma. We cannot just remake the original retainer and place it on top of crooked teeth. The choices are to re-treat the patient with segmental fixed braces, which is time-consuming and costly, or to scan or take impressions, fabricate a new full-time-wear retainer and then use dimpling pliers to apply pressure in an attempt to correct the relapsed teeth. Each suggestion requires re-treatment involving time and expense.

Suggesting re-treatment can have a detrimental effect on the practice. If patients are faced with additional charges (which could range from $600 to $1,200 or more) for re-treatment as a result of relapse, they could become upset with the additional charges, resulting in the loss of the patient and any potential referrals.

I have been faced with the following difficult scenario on more than one occasion: Parents bring in their second child for a new-patient exam, and at the same time bring their older child who finished orthodontic treatment a year ago and has either lost his or her retainer or was noncompliant with retainer wear. If the parents are faced with new charges for their older child because of relapse, they may delay starting the younger patient—or even avoid orthodontic treatment altogether. In this scenario, nobody wins.

The solution
Recently I had an epiphany that’s helping my retention patients considerably. One day, I was considering all the possible ways to solve a retention issue for a teen patient who hadn’t worn his Vivera retainer in the past six months, resulting in crowding of his lower anterior teeth (Figs. 1 and 2). His original retainer couldn’t even be pushed halfway down on his teeth, and when he did try to put it on he experienced significant discomfort (Fig. 3).

I thought of the VPro device from Propel Orthodontics, which I recommend as an aligner seater. I used a dimpling pliers to activate a small amount of axial rotation into the patient’s retainer to guide the tooth back into occlusion (Figs. 4 and 5). As a result of VPro’s high-frequency seating effect, the patient was able to leave the office with his retainer seated better—not yet perfect, but without discomfort (Figs. 6 and 7). When he returned a month later, the rotation was almost gone; after four months of wearing his retainer and using VPro, his teeth had returned to the same position as when he completed orthodontic treatment (Figs. 8 and 9). I instructed him to continue to use his VPro daily in retention for the next two to three months.

In another case, an adult patient had invested $650 for four sets of Vivera retainers. She understood her role in the relapse, but was upset feeling that this money would have been wasted if I had to make a new set of retainers. After using VPro, however, the retainer was gradually reseated and the patient still had three retainers left to use in the future.

Another advantage of using VPro to gently seat a retainer is that pushing the aligners down with biting force, or with fingers over rotated teeth, or using a “chewy” can result in concentrated stress and cracking of the clear vacuum-formed retainer. VPro’s full-arch mouthpiece distributes the forces evenly, and the soft, viscoelastic outer layer gently and progressively seats the retainer (Fig. 10). My patients have had great success keeping their retainers intact and ultimately protecting their investment. These examples are each based on techniques to correct relapse after it occurs.

Prevention is key
Preventing relapse is always preferable to treating it. Through proactive education and choosing the appropriate retention strategy together, we can certainly improve upon the 40 to 90 percent relapse rate at 10 years. We know both the periodontal tissues and alveolar bone must reorganize to support a final stable occlusion. Based on a recent study published by Judex et al., it may be possible to accelerate remodeling of periodontal tissues. This study investigated the impact of vibration at the cellular level concluded that high-frequency vibration significantly increased cell proliferation/gene expression in human periodontal ligament fibroblasts and osteoblasts.4 Further study is needed to determine the clinical significance of this finding. If the periodontal ligament reorganization process could be accelerated, it is possible that the full-time active retention period could be reduced.

Another recent study may have profound impact on how we look at high-frequency vibration, particularly its application in orthodontic retention.⁵ Much of the discussion about vibration use in orthodontics has been its potential application toward accelerating tooth movement. In the Paradox study, Alikhani et al. investigated the mechanism of action and target cells of both high- and low-frequency acceleration in a fixed-appliance model. They reported:

• “Orthodontic forces trigger an inflammation-dependent catabolic cascade that is crucial for tooth movement.”
• “Applying HFA for a short period of time (5 minutes per day) increased the expression of inflammatory markers beyond the saturation point, while simultaneously increasing the rate of tooth movement.”
• “Not only can the catabolic effect of HFA accelerate the rate of orthodontic and orthopedic treatment, but in the absence of orthodontic forces, HFA can induce an anabolic response with the potential to increase the stability and retention of orthodontic results.”

This study was Part 3 of a 10-year methodical investigation of vibration specifically for dental applications in a university research environment.^5–7

While VPro is indicated for use with clear aligners, I have used it successfully with my braces cases during active treatment as well. I began this practice after receiving consistent feedback on its pain-relieving effects while collecting data later to be submitted for publication in a clinical trial.8 Among these braces patients, I use VPro as another helpful retention application with what we call an “active retainer” that has eliminated one or two more appointments at the end of active treatment.

In my practice, we are moving away from alginate impressions. During the visit before debonding, we scan the patient with braces on, digitally remove the braces, zoom in, and carefully look for any rotations or small movements that we may have missed. Then we use software to align that tooth while the patient is still in braces; we create the 3D-printed model with the desired straight teeth and make the vacuum-formed retainer.

On debonding day, we immediately give patients their “active retainers,” which will require enhanced seating because there may be light forces programmed on one or more teeth. In the presence of orthodontic force, these teeth will potentially benefit from the catabolic properties of high-frequency targeting the compressed periodontal ligament,⁵ enhancing inflammatory response and accelerating tooth movement. Once this final detail movement has fully expressed, forces subside, inflammatory markers return to baseline and high-frequency vibration shifts to anabolic.^5,7 At this point, the high-frequency device is directly increasing osteoblast proliferation and delivering mechanical stimulation to osteocyte mechanosensors, which upregulate bone density in support of retention.^4,9

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Conclusion
Beginning with the end in mind—implementing a retention strategy at the initial consult or early in treatment—could help minimize active-treatment visits and post-treatment instability.

I now recommend that all my VPro patients continue using their device five minutes daily for the first two or three months in retention. The increased utility to enhance both active treatment and retention delivers clinician and patient alike significantly more value from the device. With VPro helping in the process of retention, I believe that my practice has been able to stabilize teeth more efficiently, reduce relapse and make retention a much more comfortable process.

References
1. Pratt MC, Kluemper GT, Hartsfield JK Jr., Fardo D, Nash DA. Evaluation of retention protocols among members of the American Association of Orthodontists in the United States. Am J Orthod Dentofacial Orthop. 2011;140(4):520-526.
2. Yu J, Huang H, Liu C, Wu J, Li Y, Tsai M, Hsu J. Does Orthodontic Treatment Affect the Alveolar Bone Density? Medicine. 2016;95(10):e3080.
3. Cohen AO, Breiner K, Steinberg L, Bonnie RJ, Scott ES et al. When Is an Adolescent an Adult? Assessing Cognitive Control in Emotional and Nonemotional Contexts. Psychol Sci. 2016 Apr;27(4):549-62.
4. Judex S, Pongkitwitoon S. Differential Efficacy of 2 Vibrating Orthodontic Devices to Alter the Cellular Response in Osteoblasts, Fibroblasts, and Osteoclasts. Dose-Response July-September 2018:1-8
5. Alikhani M, Alansari S, Hamidaddin MA, Sangsuwon C, Alyami B, Thirumoorthy SN, et al. (2018) Vibration paradox in orthodontics: Anabolic and catabolic effects. PLoS ONE 13(5): e0196540.
6. Alikhani M, Lopez JA, Alabdullah H, Vongthongleur T, Sangsuwon C, Alansari S, Oliveira SM, Nervina JM, Teixeira CC. High-frequency acceleration: therapeutic tool to preserve bone following tooth extractions. J Dent Res 2016. 95(3):311–318.
7. Alikhani M, Khoo E, Alyami B, Raptis M, Salgueiro JM, Oliveira SM, et al. Osteogenic effect of high-frequency acceleration on alveolar bone. J Dent Res. 2012; 91(4):413-9.
8. Shipley T, Brigham G, Sparaga J, Nicozisis J. Reduction in Pain to Orthodontic Forces Using a High Frequency Pulse Vibration Device: A Clinical Trial. [Submitted for publication], 2018.
9. Judex S, Gupta S, Rubin C. Regulation of mechanical signals in bone. Orthod Craniofac Res 2009;12:94–104.