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22 Ortho Tribune United Kingdom Edition | 1/2017 ORTHO TRENDS Dr Amit Lala, USA Introduction to vibration therapy—multiple potential benefits Accelerated orthodontics and vibration therapy to fast track orthodontic tooth movement (OTM) have been hotly debated topics in the orthodontic indus- try in recent years. Periodontally Accelerated Osteogenic Ortho- dontics (PAOO) techniques such as osteotomy, open flap corticot- omy, and piezocision have been shown to decrease treatment time.1 Unfortunately, these classi- cal approaches have had limited patient acceptance because of their invasiveness and side ef- fects.2 In the last several years, micro-osteoperforation, which takes advantage of the same biological regional acceleratory phenome- non as these classical techniques, has been gaining rapid clinical adoption because of the simpli- city of its chairside microinvasive nature.3 There is also growing evidence that the application of mechanical energy-based therapies such as vi- bration can stimulate and acceler- ate bone formation and possibly bone remodelling.4–7 Orthodontic tooth movement, caused by the application of light continuous forces that induce bone formation and remodelling, could logically be accelerated by the application of vibrational force, with the ben- efit of reducing the overall treat- ment time. Since 2008, AcceleDent (OrthoAccel Technologies) has of- fered a daily use vibration device, offering the promise of acceler- ated orthodontic treatment based on delivering mechanical stimu- lation to the dentition. At this point, research on the efficacy of this device in accelerating OTM has been mixed, and clinicians debate its value. The debate on vibration ther- apy as it applies to accelerated orthodontics in general, and the effectiveness of the AcceleDent device specifically, should con- sider other factors in evaluating efficacy. First, there is a distinct possibility that frequency optimi- sation of the devices concerning bone formation/remodelling has not been established. AcceleDent operates in a low frequency range, however, research points towards the benefit of high frequency in bone modulation. Secondly, cur- rent research indicates that high frequency low magnitude (HFLM) vibration therapy as applied to orthodontic treatment may have multiple potential benefits, in- cluding, but not limited to, accel- erated OTM. This article will discuss these additional benefits, including faster more efficient aligner therapy when used as a nightly seating tool, relief of normal orthodontic discomfort from new tight fitting aligners and routine adjustments to fixed appliances, and enhance- ment of orthodontic retention. Additionally, it will touch upon evidence that HFLM vibration is useful in increasing bone density and trabecular bone thickness suggesting applications in implant dentistry and prosthodontics. Current vibration devices used in orthodontic therapy As mentioned previously, the most common, commercially avail- able, vibration device for ortho- dontic treatment is AcceleDent manufactured by OrthoAccel Tech- nologies. This device delivers a vi- brational frequency of 30 Hz and requires 20 minutes per day user wear time. Several early studies on the AcceleDent device seemed to demonstrate higher rates of OTM than the established norms.8–10 However, there are other more re- cent studies that have failed to es- tablish the advantages of the same therapy. A study by Woodhouse et al. (2015) analysed the AcceleDent device to demonstrate its effect on OTM in extraction cases. They found that the supplemental vi- brational force did not signifi- cantly increase rates of orthodontic alignment with a fixed appliance.11 Another comprehensive report on vibration therapy by investigators Yadav et al. (2015) concluded that low frequency mechanical vibra- tion using AcceleDent had no significant effect in accelerating tooth movement.12 The recent studies regarding the apparent ineffectiveness of AcceleDent may be explained by the relatively low vibrational fre- quency of the device. For purposes of this discussion low and high frequency are defined as: • Low frequency–less than or equal to 45Hz; • High frequency–greater than or equal to 90Hz. In a 2010 study by Judex and Rubin, ovariectomised rats were subjected to either low or high frequency vibration. Bone forma- tion rates for subjects treated with high frequency were 159 per cent greater when compared to con- trols, whereas bone formation for low frequency rat subjects were not significantly different than controls. Trabecular bone volume and thickness were also signifi- cantly higher for subjects treated with high frequency.13 Similarly Alikhani et al. found a statistically higher rate of alveo- lar bone formation (+190 per cent) at higher frequencies, with a five minuntes per day application. In short, the most pronounced osteo- genic effects of vibration seem to occur well above the AcceleDent’s low vibrational frequency.14,18 Practically speaking, five min- utes of daily wear time may be beneficial, as it will reduce the dependency on significant patient compliance. In order to realise the maximum benefits of vibration therapy, shorter wear times would logically increase compliance, and improve results. Given all other factors being equal, the studies suggest that a higher frequency device would deliver equivalent amounts of HFA Energy to the dentition in a significantly reduced timeframe. The future of vibration therapy: Expanded application, multiple benefits The apparent limitations of current commercially available vibration devices should not di- minish the potential importance of vibration therapy. Setting aside applications such as implant den- tistry and prosthodontics sug- gested by the osteogenic properties associated with vibration therapy, there are at least four important clinically beneficial orthodontic applications that can be antici- pated. These potential applications are: 1) as a nightly clear aligner seating device; 2) analgesia; relief from normal discomfort associ- ated with orthodontic treatment; 3) accelerated orthodontic tooth movement; 4) and enhancement of retention to minimise orthodontic relapse. What follows is a brief examination of each of the four applications of HFLM vibration as an orthodontic therapy. Improved aligner seating The importance of properly seated aligners, to efficient tooth movement in aligner therapy is clearly understood. Improperly seated aligners can slow treatment, forcingpatientstobacktracktopre- vious trays, and create unintended collateral tooth movements, with a consequence being time con- suming and costly refinements. Seating recommendations range from using ‘chewies’, to biting on hard objects. Some clinicians ad- vise seating only when trays are new (immediately post change), while others recommend daily seating. With the current seating modalities, it is unlikely that pa- tients consistently seat aligners fully. A seating protocol, that takes only five minutes nightly, deliver- ing a range of other patient bene- fits, would insure that aligners are fully seated throughout treatment. Consistent proper aligner seating, would likely result in more effi- cient, faster aligner treatment, even absent biomechanical acceleration caused by vibration itself. Non-pharmacological analgesia Discomfort or pain is a com- mon side effect of orthodontic treatment. The forces applied to the dentoalveolar complex which are required to move teeth, compress the periodontal ligament (PDL) causing inflammation. Pain is most notable when seating a new aligner, or immediately after wire changes and adjustments, when pressure on the PDL is at its greatest, and diminishes as the aligner material expands, and/or the dentition com- ply. In a study accepted in Septem- ber 2015 by the Angle Orthodontist for future publication, Lobre et al found in a randomised clinical trial that vibration therapy ‘resulted in significantly lower perceived pain and less OTC medication use.’15 One theory is that vibration restores normal circulation to the PDL, which is otherwise restricted by compressive forces. Increased blood flow intercepts the ischaemic re- sponse and limits inflammation. Accelerated OTM It is well established that bone undergoes formation and resorp- tion in response to external loading such as gravitational forces, as well as to internal loading such as mus- cular activity.16 Recent research with both animal and human mod- els have demonstrated anabolic re- sponses such as bone growth and changes in bone mineral density in response to vibration.6,7,17 Since OTM is fundamentally based on bone remodelling (formation and resorption) there is little doubt that HFLM vibration has the potential to favourably impact OTM. In a recent split-mouth ran- domised trial involving bilateral maxillary canine distraction after first pre-molar extraction on 15 hu- man subjects, Leethanakul et al. (2015) investigated the impact of vi- bration on accelerated tooth move- Vibration therapy in orthodontics: Realising the benefits 0 % 5 % 10 % 15 % 20 % 25 % Controls Low Freq High Freq Impact on Bone Volume: High vs Low Frequency Vibration Graphic 1: Relative impact of frequency on bone morphology. Increases in bone volume for high frequency subjects was 25 per cent higher than controls; low fre- quency subjects were not statistically different than controls. 0 % 5 % 10 % 15 % 20 % High Freq* Low Freq % Increase in Alveolar Bone Volume Graphic 2: Higher Frequencies are more anabolic. Alikani et al found high fre- quency vibration to be most efficient at accelerating bone growth. * Statistically different from controls and low frequency subjects