We want to praise Dr Darendeliler and his group for another excellent short-term in-vivo study of orthodontic root resorption, published in the January 2017 issue (Patterson BM, Dalci O, Papadopoulou AK, Madukuri S, Mahon J, Petocz P, et al. Effect of piezocision on root resorption associated with orthodontic force: a microcomputed tomography study. Am J Orthod Dentofacial Orthop 2017;151:53-62). This study and many others serve as important bases that shape the treatment paradigms for orthodontic root resorption. However, we would like to know whether the focal resorption seen on extracted roots’ surfaces by different magnifying devices of short-term in-vivo studies can predict the apical root shortening diagnosed with different clinical imaging procedures (x-rays, cone-beam computed tomography, and so on) during or after full orthodontic treatment.
Short-term in-vivo experiments last usually 1 month but not more than 4 months, whereas the different phases of orthodontic root resorption inflammation last much longer. It has been shown in countless studies that most focal surface resorptions are being remodeled and filled with new cementum layers. It takes longer to repair the resorbed crater than to create it. It might be that the resorbed areas seen on the surface of a short-term in-vivo experimental extracted tooth are really areas that were supposed to become fully remodeled, and we really experience the normal reaction of the tissues to the pressure on its way to recover.
Years ago, we proposed to name the process “orthodontically induced inflammatory root resorption” (OIIRR). Over time, we realized that OIIRR is too general, since the root surface is not a uniform tissue, and each area—gingival crest, body, and apical zone—reacts differently to the inflammation that orthodontic force produces.
As a profession, we should make all the efforts to distinguish between these 3 types of resorptions. Right now, we must focus on differentiating between the 2 most common resorptions, the body and the detrimental apical one.
Lately, we introduced the term “orthodontitis” to replaces OIIRR. Orthodontitis is divided into 2 categories: instrumental orthodontitis (IO), where most of the body and apical resorptions undergo the full reversible remodeling process; and instrumental detrimental orthodontitis (IDO), where the inflammation truly shortens the apex, and it can clinically be detected by different imaging techniques. It seems that IO and IDO belong to the reversible and the irreversible body’s defense mechanisms, respectively.
Most professionals are not aware of the difference between the root’s normal or physiologic body surface resorption as a reaction to force application and pathologic apical resorption. Therefore, the short-term in-vivo experiments serve as an essential part of reviews and help the buildup of sometimes wrong or unproved paradigms.
We suggest that a statement, saying that the results may or may not be correlated to apical root shortening after a full course of orthodontic treatment, will be a part of future orthodontic root resorption in short-term in-vivo experimental publications. We hope that authors of those articles will agree with us.