Harm is “the totality of possible adverse consequences of an intervention or therapy.” An adverse event is any unfavorable or harmful occurrence in a patient, temporarily related to a medical intervention, but without any judgment about causality. Although many biological and mechanical risk factors have been associated with external apical root resorption (EARR), a causal relationship has not yet been established. Thus, EARR is an adverse event occurring in orthodontic patients, and its research is a harm-related issue.

Barros et al, in their article in the February 2017 issue, reported the EARR related to anterior retraction with miniscrews (Barros SE, Janson G, Chiqueto K, Baldo VO, Baldo TO. Root resorption of maxillary incisors retracted with and without skeletal anchorage. Am J Orthod Dentofacial Orthop 2017;151:397-406). However, comparing this technique with the extraoral anchorage, using historical controls, and measuring the outcome with periapical radiographs, were not the right choices, since the target was not to evaluate efficacy or effectiveness but, rather, harms.

Kokich raised clinical questions related to EARR: “What causes root resorption? Is it due to heavy orthodontic forces placed on the teeth? What is the incidence of root resorption among orthodontic patients? Is the tendency for root resorption inherited? What is the prognosis for teeth that have had significant root resorption?”

The answers to these questions are important for achieving optimal management of EARR during orthodontic treatment and appropriately informing patients about the risk with this treatment alternative.

In clinical research, however, more important than elaborating appropriate questions, is choosing the right methodology to arrive at useful, valid answers. The randomized controlled trial is not the gold standard in the search of the evidence related to harm, since it may be unfeasible, unethical, or ineffectual. Thus, observational methods may be valid alternatives. As Rothman said: “The type of study should not be taken as a guide to a study’s validity.”

The development of new orthodontic techniques will affect the occurrence of EARR and other adverse events, and so the assessment of the risk of harm will become more important.