Finite element research by Lee et al to evaluate the effects of rapid palatal expansion on the craniofacial skeleton of a patient with unilateral cleft lip and palate (UCLP) and to predict the point of force application for optimal expansion desired in UCLP patients has apprised readers regarding the expansion protocols to achieve controlled expansion in patients with UCLP (Lee H, Nguyen A, Hong C, Hoang P, Pham J, Ting K. Biomechanical effects of maxillary expansion on a patient with cleft palate: A finite element analysis. Am J Orthod Dentofacial Orthop 2016;150:313-23).
However, we have some concerns regarding the summarization of results by the authors and the statement in the methodology section of the article.
Regarding the summarization of the results as observed by the authors, they have conflicting statements regarding the displacement of cleft and noncleft sites in group 3 combinations as follows:
In the results section of the study, it was observed that equal expansions of the cleft and normal sides occurred when expansion forces were directed between URE and ULD (cleft-side deciduous second molar and noncleft-side deciduous first molar); however, the authors contradicted this observation by stating that maximum displacement of the cleft side occurred at the incisal edges of URC (cleft-side deciduous canine) and gradually decreased from anterior to posterior teeth with minimal expansion at UR6 (cleft-side permanent molar) when forces were applied between URE and ULD.
We request the authors to revise their statement in the summary section: “Expansion on the normal side was greater than on the cleft side when forces were applied to noncleft-side molars and cleft-side deciduous molars, UR6-ULE and UR6-ULD.” Actually, the opposite is true, as observed from the results section of the study where it is stated that expansion on the normal side was greater than on the cleft side when forces were applied between cleft-side molars and noncleft-side deciduous molars (UR6-ULD and UR6-ULE).
In the methods section, a concern arises with respect to the statement “trying to simulate transverse forces from various expansion devices to achieve an optimal desired expansion in UCLP patients (more activation of anterior region and minimal expansion of posterior region of minor segment).” This statement is incomprehensible because the authors are still developing an ideal direction of transverse forces between the major and minor segments to elicit the optimal expansion in patients with UCLP.