We read with interest the article, “Incidence and effects of genetic factors on canine impaction in an isolated Jewish population” (Chung DD, Weisberg M, Pagala M. Am J Orthod Dentofacial Orthop 2011;139:e331-5).

First, we congratulate the authors for their contribution of identifying a genetic factor contributing to the etiology of palatally displaced maxillary canines. The exact etiology of palatally displaced maxillary canines was unknown until recent years. The authors determined the incidence and effects of genetic factors on palatally impacted canines in a genetically isolated community of ultraorthodox Hassidic Jews of Ashkenazi descent. But, there are some aspects of this study to which we want to draw attention and give additional information.

The authors stated that “A canine was considered impacted if it was not erupted within the normal chronologic age range and had to be surgically exposed to bring it into the oral cavity.” However, the normal chronologic age range and the systemic condition of patients (endocrine deficiencies, febrile diseases, and so on) were not clarified and discussed by the authors.

As stated in other studies, a tooth would be considered impacted if its complete eruption to the oral cavity was prevented by abnormal contact with an adjacent tooth in the same arch and root development of the impacted tooth was at least 75% complete or the patient was over 16 years of age. In our recent study, a tooth was recorded as impacted when it was not exposed in the oral cavity and the patient was over 16 years. Therefore, the mean age of the patients was 19.17 years (range, 16-25 years) in our study.

Several etiologic situations including localized, systemic, and genetic factors could contribute to cause canine impactions. The authors provided some information about localized and genetic factors, but nothing about systemic factors was included. If some patients had systemic disorders, we would like to know whether the findings of this study are reliable.

In this study, the incidence of impacted canines—4.9%—was higher than reported in previous studies. Even if these anomalies do not occur frequently, it is important to make an early diagnosis to begin treatment at the optimum time.