We thank our colleagues for their thoughtful remarks.
The most important notion advanced in our study is that tooth movement is the result of an inflammatory process that controls the rate of osteoclast activity and therefore bone resorption. Micro-osteoperforations can accelerate this process by increasing the release of inflammatory markers. As our colleagues mentioned, similar to micro-osteoperforations, extractions can function as an excellent source of inflammatory markers. In our clinical trial design, to separate the effects of extractions from the effects of micro-osteoperforations, we delayed the application of micro-osteoperforations for 6 months after the extractions. In our daily orthodontic practice, of course, extractions can function as micro-osteoperforations, and when possible, they should be postponed until the time of active space closure mechanics to take advantage of their effects on the rate of tooth movement. However, it should be emphasized that whereas extractions can function as micro-osteoperforations, similar to micro-osteoperforations, their effect is limited to the time and the place of application (does not last for more than a few months).
Therefore, to accelerate movement in the areas away from the extraction space or for a few months before or after extractions, micro-osteoperforations are a versatile approach that can be used frequently to accelerate movement of any tooth or group of teeth at different stages of treatment. This procedure can be even more helpful when there is no need for extractions or when extractions have been performed long before the orthodontic treatment.
Our colleagues also asked why the lateral incisors were used as a reference to measure movement of the canines, when we could have used the second premolars. In theory, canine retraction can be exaggerated (false positive) if there is any forward movement of the premolars (for any reason), and it can be underestimated (false negative) if there is any distal movement of the lateral incisor with the canine. Although in our study we did not find any significant movement of premolars or lateral incisors, we decided to report the data collected between the canines and the lateral incisors to decrease any false-positive results.
The other question raised in this letter was the duration of treatment. This clinical trial was designed to precisely monitor tooth movement (canine retraction) in 1 month. Increasing the duration of the study could impose other variables that would obscure the main purpose of the clinical trial, which was evaluation of the effects of micro-osteoperforations on the rate of tooth movement. Based on this 1-month study, the rate of tooth movement increased more than twice. Therefore, it is logical to assume that if the rate of tooth movement is the main factor in determining the duration of treatment, frequent applications of micro-osteoperforations during treatment should decrease the duration of treatment more than half. This is under the assumptions that mechanotherapy and patient cooperation have been optimized, and the biology of tooth movement is the only limiting factor. Currently, other dental centers are conducting long-term clinical trials to learn how often micro-osteoperforations should be applied to maintain the rate of tooth movement at an optimum level. We hope to report on these results soon.