We commend Dr Feifei Jiang and colleagues for an excellent study published in the September 2017 issue of the AJO-DO (Jiang F, Chen J, Kula K, Gu H, Du Y, Eckert G. Root resorptions associated with canine retraction treatment. Am J Orthod Dentofacial Orthop 2017;152:348-54). However, we would like to comment on several points.

• 1.

  Was it really proved that the “level of orthodontic load sensed by the tooth” is a potential contributing factor to external apical root resorption (EARR)? After rereading the 4 references mentioned, we say that none of them described actual EARR. These studies found more resorption lacunae—the defense mechanism of the cementum—on different root surfaces when heavier forces were compared with lighter forces. Those lacunae are the normal reaction of the cementum to the force. Normally, those lacunae are being fully remodeled by filling with cementum over time. The problem of the conclusions is in our mind. When somebody states that more resorption lacunae were detected using heavier forces, it immediately comes to our mind that it relates to more EARR. This imaginary connection has never been proved.

• 2.

  How was the intrusion (right side of Table I) measured?

• 3.

  Regrettably, this report does not discuss the authors’ approach to the 6 teeth that “became longer” during the study. We believe that this discussion is crucial to this study, since it deals with minute measurements that are software (CBCT algorithm), hardware (type of CBCT), and even human dependent.

• 4.

  We believe that the results, as well as the conclusions of articles discussing genotypes, should be much more unequivocal. We did not see in the reference list the study of Pereira et al that found, contrary to this article, only a minor contribution of IL-1β rs1143634 GG to EARR.

• 5.

  The sentence in the discussion stating “Although the sample size was small so that no conclusions could be made, the data suggested that older subjects might be more at risk for EARR“ puzzled us. The authors ignored the fact that the youngest participant in the study (age 12) had 6 and 3 times more EARR than the adult participant (age 47) in RR_CT and RR_TR, respectively.

• 6.

  Finally, looking at Table I, especially at the relatively huge resorption of P15, one can draw the false conclusion that patients carrying the combination IL-1β rs1143629 AA, IL-1β rs1143634 GG, IL-1β rs1143643 CC, IL-1 RA rs315951 GG, IL-1 RA rs315952 CC, and IL-1 RA rs1794065 GG are at a high risk for EARR during orthodontic treatment.