Kabsoo Jang, Kyung Eun Suk, Mohamed Bayome, Yoonji Kim, Seong-Hun Kim, Yoon-Ah Kook

Comparison of arch form between Koreans and Egyptians.

- Korean J Orthod 2010;40(5):334-341

Q. This paper gives valuable information regarding the difference in arch forms between the Korean and Egyptian populations. However, I have a few questions about the selection criteria used in the study, which were listed as 1) a full permanent dentition excluding the third molar, 2) normal size and shape of the teeth, 3) no supernumerary tooth, 4) 3 mm or less arch length discrepancy, 5) no restorations extending to contact point, cusp tip, incisal edge, and 6) no previous orthodontic treatments.

My concern is that the criteria have no mention of a rotation when in fact any presence of significantly rotated teeth in the premolar region could have caused a considerable difference in the bracket position without much affecting the overall arch length discrepancy. Even more serious errors could have been possible if the rotation was involved with the first molars. In addition, 3 mm of crowding seems to be a substantial amount in clinical orthodontic situations. What was the authors' rationale for choosing 3 mm or less as one of the selection criteria for the arch length discrepancy?