To: The Editor, The Angle Orthodontist
Re: Response to: Comprehensive comparison of canine retraction using NiTi closed coil springs vs elastomeric chains: A split-mouth randomized controlled trial by Haya A. Barsoum, Hend S. ElSayed, Fouad A. El Sharaby, Juan Martin Palomo, Yehya A. Mostafa et al. Angle Orthod. 2021;91:441-448.
We appreciate the insightful and interesting comments on our article.
As far as the baseline demographic data of the sample, the patients in this study were adolescents and young adults. The average age was 18.5 ± 3 years. The majority of the patients were females (83%). Despite helping in validation of the comparison, restriction of the gender to females and focusing on a specific age range may reflect on the generalizability of the results.
Great care must be taken when choosing a split-mouth design to assess simultaneous interventions. We agree that statistical tests for paired data may have been a better choice, to take into account the dependent nature of the split-mouth design. Similarly, the split-mouth design may have some limitations when assessing pain. However, it reduces the inter-individual variability which is a concern for subjective self-reported outcomes. We would like to point out that the unit of analysis was the quadrants. Hence, in the current study the percent difference in number of days with reported pain between the NiTi coil spring and elastomeric chain groups was 1.47% which was reported for sixty days for each quadrant (total 32), making the difference of days with pain between the two groups about 28 days. These results are by no means conclusive and require further investigation.
Despite having standard deviations higher than the means for many variables in both groups, reflecting variability, the data in the present study were comparable to the results in the orthodontic literature. 1,2 A future meta-analysis may provide a more precise estimate of the reported outcomes.