We appreciate Dr Kuhn et al for their study published in the March issue (Kuhn M, Markic G, Doulis I, Göllner P, Patcas R, Hänggi MP. Effect of different incisor movements on the soft tissue profile measured in reference to a rough-surfaced palatal implant. Am J Orthod Dentofacial Orthop 2016;149:349-57). The article provides significant insight into the changes in the soft tissue profile by the movement of incisors using a palatal implant as a reference and is a valuable addition to orthodontic literature. Although the study emphasized the need for stable reference points in the form of palatal implants for evaluation of incisor movements, there were a few concerns on following points.
The total sample size mentioned in the study was 47 subjects, of whom 17 patients had Class I malocclusion, 28 had Class II malocclusion, and 2 had Class III malocclusion. Of the 28 patients having Class II malocclusion, 22 were female, and 2 were male. The total of the Class II sample size thus comes out to be 24 subjects, which could not be comprehended and also was not discussed.
In the study, the minimum chronologic ages of 16 years for female subjects and 18 years for male subjects were accepted if the residual growth could be excluded by hand-wrist radiographs. Since it was a retrospective study, were the hand-wrist radiographs obtained as a routine diagnostic aid in patients above the age of 16 years in females and 18 years in males during the times when they were being treated?
The distance of the x-ray source to the coronal plane was set at 200 cm. The recommended distance from the x-ray source to the midsagittal plane is 152.4 cm, or 5 feet. What were the reasons for using the increased distance from the x-ray source against the standard norms and for using a custom-made x-ray device? Furthermore, were any changes made in the exposure parameters to compensate for the increased x-ray source to the coronal plane distance?
We would be really grateful if the authors can clarify these points. Also, since it was a retrospective study, it would help us better comprehend if we can know the approximate past time frame when these patients were treated.