Commentary

The systematic review published in the Cochrane Database of Systematic Reviews had the task of reviewing and updating the evidence of orthodontic treatment modalities in the class II division 2 patient. Class II division 2 patients have a characteristically deep bite with retroclined upper front teeth. The extraction vs non-extraction debate has plagued the field of orthodontics since its inception at the turn of the twentieth century. Edward Angle, widely considered the father of orthodontics, was a staunch believer in non-extraction therapy. One of his brightest disciples, Charles Tweed, soon became opposed to non-extraction therapy and completed many cases in which extraction of the four first premolar teeth was deemed necessary.1 The authors of this systematic review concluded that there was no evidence to support either treatment modality. Interestingly, the authors isolated 857 articles using the aforementioned databases. However, the authors failed to elucidate on the exclusion criteria used to determine that these particular articles were of no use. This could have been done in the form of a table or flow chart, as many systematic reviews have adopted. Furthermore, the article's topic specificity of RCTs and CCTs of class II division 2 may have limited the ability to arrive at a more concrete solution. A recent 2018 systematic review of 14 retrospective studies in the American Journal of Orthodontics and Dentofacial Orthopedics aimed to assess the effects of four premolar extractions on the vertical dimension of the face.2 The 14 studies included were a combination of class I, II and III patients that received four premolar extractions. Two retrospective studies included were specifically on hypodivergent, class II patients. With the limitations of the evidence, the article failed to find any difference in the skeletal vertical dimension of extraction and non-extraction treatment protocols. Moreover, a 2012 systematic review done by the same author of the Cochrane review and published in the American Journal of Orthodontics and Dentofacial Orthopedics on post-treatment stability of class II division II treatment was indecisive about the effect of extraction vs non-extraction therapy. No clear evidence favoured one treatment protocol over the other. However, it was recommended to be prudent when extracting in cases of a thin upper lip and/or an increased nasolabial angle to prevent possible adverse effects on profile.

Lastly, a 2012 retrospective study published in The Art and Practice of Dentofacial Enhancement studying the long-term stability of four premolar extractions in class II patients failed to find any difference in post-treatment parameters between the two treatment protocols.4

Long-term stability such as overjet, overbite, canine and molar relationships were similar in all the studies. The expectation for a randomised clinical trial on this topic may not be feasible and justifiable. Despite some limitations of this review, the current evidence does not support one treatment modality over the other. Further investigation is required to further establish the answer to this clinical dilemma. It is important for orthodontists to establish the success of treatment modalities so that stability of treatment outcomes can be assured. This will ensure a more consistent and evidence-based approach to the practice of orthodontics.