"This comprehensive search indicates that there is an absence of reliable evidence on the positive effects of orthodontic therapy on periodontal status." That sentence led off the Conclusion section of the April JADA cover story article by Dr. Anne-Marie Bollen and colleagues, "The Effects of Orthodontic Therapy On Periodontal Health: A Systematic Review of Controlled Evidence" (JADA 2008;139[4]:413–422).
To be fair, the authors also should have said that there is an absence of reliable evidence regarding the negative effects of orthodontic therapy on periodontal status. The authors clearly acknowledge weaknesses with their analysis because of inherent problems with the 12 research studies on which their analysis is based. These weaknesses should have prevented the drawing of valid conclusions regarding either positive or negative effects of orthodontic care.
The weaknesses of the chosen research are serious: "The main limitations of the review are the potential for bias of the identified studies, the inability to determine the mechanisms by which orthodontic treatment caused the periodontal effects and the studies we chose to be included in the review." In fact, owing to the limitations of the studies, it is not clear that orthodontics caused any periodontal effect.
Consider the conclusion that "orthodontic therapy was associated with 0.03 millimeters of gingival recession" at the 95 percent confidence interval. Readers may be aware that 0.03 mm is one-half the thickness of one sheet of paper found in The Journal. That measurement is insignificant—and not worth reporting—for many reasons, including human biology and measurement error. The authors also reported average bone loss of 0.13 mm, which is approximately two times the thickness of Journal paper. This has the same problem as the earlier example.
A further weakness: "While all of these studies included nontreated controls, the majority involved controls with mild or no malocclusion. In addition, the compared groups may have differed in terms of factors such as oral hygiene practices, socioeconomic status or smoking." In other words, most included studies were not controlled with regard to some key periodontal factors. Furthermore, if the so-called controls had "mild or no malocclusions," then the comparison with posttreatment orthodontic patients (presumably with mild or no malocclusions) would seem pointless.
Apparently, satisfactory research has not been designed to provide reliable evidence that plaque is easier to remove from aligned incisors than from crowded incisors. One could suppose that the answers to some questions can be intuitive. Ask a dentist about crowded incisors and plaque accumulation.
Accordingly, we believe that the American Association of Orthodontists is correct in its assessment that orthodontics can help with periodontal issues.1,2 Our office pilot periodontal study of posterior teeth positioned with little-to-no inclination (and centered on the alveolar crest) versus pretreatment inclined and noncentered teeth has convinced us.3
The authors have performed an important service by way of clear analysis and criticism of the best available studies on their topic. Their point is well-taken—there is a lack of good, published research. One would hope that a study of posterior teeth centered on alveolar crest versus nontreated teeth (non-centered and inclined) might have a higher priority than a study regarding the ease of plaque removal from aligned or crowded incisors.
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