In the May 2017 issue of the AJO-DO , Morris et al evaluated the long-term prevalence of gingival recession after orthodontic treatment. As discussed in the article, periodontal disease and mechanical trauma are believed to be the primary etiologic factors in the development of gingival recession. However, orthodontic therapy may also contribute to gingival recession.

The association between orthodontic treatment and gingival recession is of great interest to the specialty. This is especially true in light of the shift toward a nonextraction, dental-arch expansion approach. For these reasons, the authors chose to study the long-term prevalence of gingival recession after orthodontic tooth movements, focusing on mandibular incisor proclination and maxillary expansion. We appreciate the study but are concerned that the conclusion in the abstract, “orthodontic treatment is not a major risk factor for the development of gingival recession,” is overstated.

One reason for our concern is the potential for selection bias. The study stated, “A retrospective sample of 327 patients from 2 private orthodontic practices in Arlington and Dallas, Tx was evaluated. The selection criteria included records at the beginning of treatment (T1), the end of treatment (T2), and at long-term (at least 2 years after appliances removal) follow-up (T3)”. After application of the selection criteria, 205 patients were included the study. The sample size and long-term records are impressive, but the sample was not random or sequential. One third of the potential sample was lost, and we do not know whether those subjects were similar to or different from the included subjects. We also do not know what other biases may have been introduced by the selection methods.

Second, there are problems with the generalizability of the findings of this study to all orthodontic patients. The patients in this study consisted primarily of adolescents. Additionally, almost 60% of the sample was treated with premolar extractions. The age of these subjects and the high extraction rate are quite different from the demographics of contemporary orthodontic patients. For example, recent estimates are that 27% of orthodontic patients are adults. Furthermore, current extraction rates of about 25% are much lower than the rate reported in the study. Thus, at the very least, the authors’ conclusions must be qualified by the characteristics of the sample, and more research is necessary before we can make the broad claim that there is no relationship between orthodontic treatment and long-term gingival recession.