I read with a great deal of interest the article on extraction frequencies in the March issue of the journal (Jackson TH, Guez C, Lin FC, Proffit WR, Ko CC. Extraction frequencies at a university orthodontic clinic in the 21st century: demographic and diagnostic factors affecting the likelihood of extraction. Am J Orthod Dentofacial Orthop 2017;151:456-62).

I was puzzled, however, about what seemed to me the extreme discrepancy between the percentage of 4 first premolar extractions listed as “relatively consistent just above 10%” and the rate for all extractions of “consistently just below 25%.” Subtracting the 4-first premolar rate from the all-extraction rate leaves a rate of around 15% for “other extractions.” In other words, “other extractions” are 50% more likely than 4 first premolar extractions. Since Class I malocclusions are the most common problem, it is typically necessary to extract either 4 premolars or no premolars in these situations. So why so large a discrepancy?

I can think of a few reasons that “other extractions” would be used, including second premolars rather than first premolars to minimize facial changes, maxillary first premolars in Class II situations, and possibly a mandibular incisor in certain situations. It still seems to me that these figures don’t really add up.

Perhaps the authors could enlighten us and give us more information as to exactly which teeth have been extracted.