Authors’ response

We appreciate the opportunity to reply to the concerns of Drs Alpan, Daher, and Bowman. They expressed concern with the study end point and the short time frame of our research (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 we explained in the article, this is the first part of an ongoing trial, and the goal was to examine initial alignment. This short-term design has been used in previous studies examining the effect of various bracket types and archwire sequences. Specific time points of 5, 8, and 10 weeks were used to evaluate whether the reduction in irregularity or the increase in anterior arch perimeter was occurring sooner in either group. For example, if it was 50% faster, then the irregularity index and arch perimeter in the AcceleDent group by 5 weeks would be the same as the control at 10 weeks; it wasn’t. In fact there was no difference at any time point. Therefore, it would be expected that the transition to another archwire would not occur any sooner in 1 group over another.

They also expressed concern about “uncontrolled” treatment mechanics. Both groups had identical archwires and brackets, and this approach and time frame is common orthodontic practice. In addition, the assessor and the clinician were blinded to random group allocation, the gold standard in reducing bias and any effect of uncontrolled variables. Arch perimeter was chosen as the primary outcome because the original study stated that the most important variable to measure was arch perimeter and used this as a criticism of the article by Woodhouse et al. A power analysis was performed a priori to ensure adequate numbers for this variable in the study. Even if the study were underpowered, the difference between the 2 groups at 5 to 10 weeks ranged from 0 to 0.3 mm and so would never be clinically significant. Similarly, if a rate were calculated, this also would not have been significant because it is the same measurements divided by identical time intervals.

The authors cited an article stating modestly increased rates of dental alignment. This study was retrospective and unblinded, so it suffers from a potential high risk of bias. The period of initial alignment reported with the first archwire was a median 115 days (16.4 weeks) in the previously treated subjects without vibration, whereas those later treated using vibration took a median 81.5 days (11.6 weeks) to progress to the second archwire. When we compare this with the current study, the majority could transition to the second rectangular nickel-titanium archwire (not reported) at the 10-week appointment. Therefore, another possible interpretation of the former finding is that perhaps the wire progression was too slow in the first place, and the unblinded enthusiasm for faster wire progression led to the observed difference in the experimental group. Similar enthusiasm with self-ligating brackets likely led to the findings of reduced treatment time in the initial retrospective studies. However, the later prospective studies found no difference, but when combined in a meta-analysis, the SL brackets appeared to be slower than conventional brackets by about 2 months. This emphasizes the importance of blinding in clinical trials to reduce the potential observer-expectancy effect, which might subconsciously influence the outcome of the study.

Finally, we feel it is important to point out that we have no financial interest or consulting arrangement with any vibrational appliance or other competing appliance. Discussion of research findings is important, but discussion of the claims by key opinion leaders is also critical. Clinicians need to be mindful of argumentum ad verecundiam where something is given more credence than it deserves because of who is saying it. Carl Sagan reminded us that “authorities must prove their contentions like everybody else,” and we believe that our article is a significant addition to the current body of evidence.

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Apr 2, 2017 | Posted by in Orthodontics | Comments Off on Authors’ response
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