Biased look at self-ligation

The August 2010 “Ask Us” article was not an impartial look at self-ligation (Marshall SD, Currier GF, Hatch NE, Huang GJ, Nah HD, Owens SE, et al. Self-ligating bracket claims. Am J Orthod Dentofacial Orthop 2010;138:128-31). Two of the references cited disputing the formation of buccal bone had errors in study designs and were suspect because of regional accelerated phenomena. A well-designed thesis was dismissed. Was this because it found self-ligating arch expansion to be similar to that of rapid palatal expansion? A textbook chapter was referred to as “a few case reports.” Their conclusion of the stability of expansion is at odds with the authors, who stated that “there are treatments which may be effective, but for which a high level of evidence may not be found.” Could this be said of self-ligation?

On efficiency, they implied that 20 seconds per wire removal is insignificant. In a practice of 50 patients per day, at only 20 seconds, 4 days a week, 48 weeks a year, the difference is 192 patient visits, or 1 week of patient care. That is substantial, and removing wires is faster than placing them.

They noted a meta-analysis of self-ligation vs conventional ligation that showed 1.5° less maxillary incisor proclination with self-ligating brackets. These in-vivo data suggest that crowding is alleviated by buccal expansion and molar “distalization,” not the incisor flaring seen with traditional systems. This was not mentioned.

Friction and binding were addressed with a recently acquired disdain for in-vitro studies. They warned that in-vitro studies do not replicate in-vivo conditions. The review cited supports findings of reduced unwanted side effects of friction described in the in-vivo discussions. They implied that in-vitro studies’ positive results on reduced friction with self-ligation are contrived, whereas there is an emphasis on Burrows, whose premise is counter to all fundamentals of self-ligation; the advantage of self-ligation is accomplished by using small round wires, not the large rectangular wires used in Burrows’ biased report.

They attempted to discredit excellent research by Badawi et al by comparing it with Burrows’ obvious support of traditional ligation. The next studies cited support the use of small round wires in a large lumen to provide more predictable forces and fewer unwanted forces from the outset, but this concept was lost on the authors.

On pain levels associated with self-ligating systems, they downplayed that initial archwires are less painful and emphasized that the second archwire is more painful. However, they failed to mention that the early generation brackets used required pliers that caused mild discomfort to open and close slides. The second wire was larger than any practitioner of self-ligation would consider placing today and occurred without regard to malalignment. This in-vivo study failed to follow protocols and data gleaned from in-vitro studies! No wonder patients found them painful.

It has been stated that a competent clinician uses clinical judgment, “developed from sound experience and bolstered by, but not based exclusively on, systematic scientific evidence.” The authors said that “this challenge requires knowledge of the strength of the evidence of these claims.” I suggest that their challenge includes experience with self-ligations, not solely the judgment of a band of authorities on scientific evidence who might suffer from a proficiency bias leading to inaccurate interpretation of the literature.

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Apr 13, 2017 | Posted by in Orthodontics | Comments Off on Biased look at self-ligation
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