Miles and Fisher should be commended for attempting to contribute another “real-world” evaluation of AcceleDent (Miles P, Fisher E. Assessment of the changes in arch perimeter and irregularity in the mandibular arch during initial alignment with the AcceleDent Aura appliance vs no appliance in adolescents: a single-blind randomized clinical trial. Am J Orthod Dentofacial Orthop 2016;150:928-36) as a follow-up to their previous evaluation of the effects of vibration on tooth movement. However, a number of confounding issues seemed to undermine their real-world intent: determining whether vibration might increase the rate of tooth movement. The concerning issues include questionable study end points, a curiously short evaluation period, rather limited uncontrolled treatment mechanics, and inadequate sample size assessment. Taking these deficiencies together, it may be appropriate to at least question the rationale of the study design.
The selection of measuring arch perimeter expansion seems unusual when orthodontists typically choose to maintain mandibular arch form and intercanine dimensions. That choice was apparently based solely on unpublished data on 14 patients for whom no pretreatment or posttreatment measurement or investigative time frame was provided (ie, we don’t know how crowded they were or how long they were treated). Without that information, comparative analysis would seem unlikely. But no matter, the data clearly showed very little change in arch perimeter from baseline to 10 weeks for both groups. Perhaps significant changes were limited by the patients’ original arch forms but certainly by the selection of the mechanics chosen to effect any change: ie, light round superelastic wires are typically considered unlikely to elicit much, if any, change in arch perimeter. It is unclear whether the arches even “needed” additional expansive alteration during this brief 10-week evaluation, since there was only 0.6 to 1.3 mm of mandibular incisor unraveling, and so they were unraveled. For instance, a simple spring retainer would be expected to provide the same or faster changes in that time period for such a minor change: with or without vibration. There have also been previous concerns regarding the reliability of Little’s irregularity index, because it is intended to measure horizontal misalignment between teeth, not vertical discrepancies or “torque” or tip of the roots. As such, it may be considered a significant handicap for assessing orthodontic movement, so it might be argued that for an accurate assessment, 3-dimensional cone-beam computed tomography might be required.
The sample size criteria used to determine the number of patients needed for the study was based on historical “rate of movement” measures; however, the investigators never reported the rate. So, if a 51% change in rate was anticipated, is it actually reasonable to assume that the measures of arch perimeter (mm) and Little’s irregularity index would be 51% different at 5, 8, or 10 weeks? Not aligning the sample size assumptions with the measured end points can significantly alter study design and the number of patients required for a study. Rather, sample size assumptions should be based on the measured primary end point and what is considered to be a clinically meaningful difference between the treatment group and the control group. In this case, the primary end point did not align with the sample size assumptions; therefore, the investigators did not power the study to demonstrate a difference between the control and the treatment groups.
If, in fact, a difference in the rate of tooth movement might be expected with some type of intervention, it would also seem reasonable that treatment mechanics would need to have been modified (eg, changing aligner trays every week, changing wires more frequently), or at least data recordings made at shorter intervals over a longer span. By maintaining a standard treatment protocol (without shortening the follow-up interval or changing or retying wires in the authors’ evaluation period), it was questionable to expect much clinical difference between groups per the study’s protocol. Furthermore, a small diameter archwire (0.014 nickel-titanium) was unlikely to effect more than small changes: not much in terms of altering arch perimeter, or even much more than minor alignment. It was also surprising that the authors abandoned an evaluation of the intervals required to achieve specific treatment goals such as “leveling or alignment” as was reported in their previous vibration study. It certainly would have been more intriguing to compare those results with their old data and other studies examining similar effects.
Most disconcerting was the authors’ selection of a surprisingly brief evaluation period for this study: just 70 days. As noted previously, if the goal were to assess global dental movement measurements, it is reasonable to expect that no significant changes would be found in such an extremely short time frame. Would it be more likely that a true “real-world evaluation” of the clinical effectiveness of vibration effects should at least extend through a very specific and comparable phase of treatment among study groups?
In previous studies of vibration on actual “dental alignment,” there were no statistically significant differences noted in the first 10 weeks (70 days) of alignment by any investigator. This was true even after the 90 to 120 days required to finish “alignment” for the controls and the experimental patients, respectively. More importantly, a statistically significant difference was not found for vibration until 160 days when arch “leveling” was complete (ie, vibration resulted in a 30% greater rate of mandibular arch leveling when compared with 208 days for the controls). It might be concluded that “it takes time to save time as teeth don’t suddenly jump after being ‘buzzed’ just a little.” With these factors in mind, the results presented by Miles and Fisher were absolutely expected. Therefore, we are curious as to why there was a rush to finish this evaluation in such a brief period of time, especially when the aforementioned details were readily available to the investigators. It might be surmised that any effects from vibration (even if lacking in statistical significance) could have been found (or not) had treatment progressed for a reasonable amount of time, especially if substantial compliance with the vibrating devices was observed.
The point of the previous clinical research studies was to determine whether there was any effect on the rate of tooth movement from vibration—that was the key question. The “real world” intent was not to determine if a device was used but, rather, if it had an effect if it were used. For instance, when patients used the device nearly every day (average of 26 times per month for about 7 months), modestly increased rates of dental alignment, leveling, and molar distalization were reported. It is important, however, to note that extrapolating those types of effects (found during “parts of treatment”) to reducing overall treatment times is problematic, especially considering the subjective nature of what is a “finished result.”
Since there are now a number of disparate types of evaluations with conflicting results regarding the effects of vibration, it seems most important for us as clinicians (with the assistance of our academic counterparts) to foster research pursuits with improved study designs that include carefully measuring compliance, using alterations in biomechanics, gathering data points at shortened intervals, and most certainly a longer period of investigation of at least 6 to 7 months. Our primary aims should always be encouraging an objective assessment of the clinical applicability of evidence from scientific trials and squaring them with reported clinical observations when assessing the use of new treatment modalities, instead of relying on the rising trend of ad hominem influences at play. All studies are prone to limitations and being permitted to discuss a different perspective is necessary to progress the enhancement of evidence-based approaches for our patients’ benefit.