I want to make a few comments on the article “Lingual appliances reduce the incidence of white spot lesions during orthodontic multibracket treatment,” in the September issue (Wiechmann D, Klang E, Helms HJ, Knösel M. Am J Orthod Dentofacial Orthop 2015;148:414-22). This retrospective study analyzed a huge sample of patients, who were treated in one of the world’s leading lingual orthodontic practices.

Some important factors that affect the etiology of white spot lesions (WSLs) should have been reported, including the ligature type (continuous stainless steel or elastomeric power chain). This has been found to influence not only the archwire replacement speed, but also the plaque accumulation rate. Furthermore, the use of vestibular buttons for intra-arch and interarch elastics can facilitate the onset of labial WSLs.

An important difference in the sample size between the preadolescent (90% of the sample) and adolescent (10% of the sample) groups means that every comparison between them is influenced by this. Furthermore, the period of adolescence is closely associated with the teenage years; therefore, using 13 or 14 years as the cutoff between preadolescence and adolescence would have obtained more balanced groups and probably different results of a statistical comparison.

The influence of further possible confounding factors, such as oral hygiene status, nutritional habits, and fluoridation exposure, was also not considered, although this was declared in the Discussion section. A control group treated in the same clinic with a labial technique could have limited the impact of these confounding factors.

Finally, with regard to the bracketing procedure, the application of a thin extra layer of a fluoride-releasing bonding resin should have been more emphasized. This aspect of the procedure demonstrated that it can significantly (up to 3 times) reduce the onset of WSLs. Therefore, this is an important factor in the marked differences found between labial and fully customized lingual multibracket appliances.