Background and Etiology

One of the rationales often used to promote orthodontic treatment is that it will prevent periodontal problems. This rationale is based on the reasoning that a malocclusion may cause periodontal problems, and therefore, by treating the malocclusion, we can prevent the periodontal deterioration. There are several issues related to this argument that need to be considered.

First, what is a malocclusion? The term “malocclusion” implies a negative or harmful condition. However, malocclusions should not be considered a disease or a biological abnormal state (Vig & Dryland Vig 1995), even though the term includes the prefix “mal.” For an orthodontist, a malocclusion usually means any condition with malaligned teeth, or the lack of a “proper” occlusion, which is most often defined as a Class I interdigitation with an “ideal” overjet in the sagittal direction, no crossbites or scissors bites in the transverse direction, and about a 2-mm positive overbite in the vertical dimension. Deviations from this often result in a recommendation for treatment without considering if a correction is actually needed, wanted, and/or beneficial. From the perspective of patients, malocclusions are usually conditions with less than acceptable esthetic appeal. Orthodontists quite often are happy to “educate” prospective patients, and the belief that a less than ideal “bite” may result in periodontal problems is often used during these discussions.

Second, what is the evidence that a malocclusion is causing periodontal disease? To unequivocally establish the existence of true cause and effect, one should embark on a randomized controlled study, in which malocclusions are randomly assigned to participants and their effects on periodontal condition are measured. No such studies are available. Several studies with lower levels of evidence (epidemiological surveys, cross-sectional and cohort studies) have evaluated the coexistence of malocclusions and periodontal disease (see below). However, both conditions are very prevalent, and their simultaneous occurrence does not prove cause and effect.

Lastly, does orthodontic treatment reduce the risk for periodontal disease? The strongest evidence that orthodontic treatment prevents periodontal problems comes from studies that directly measure the effects of this treatment on periodontal health, not by relying on the assumption that the elimination of malocclusions has to be beneficial. Several studies have compared the periodontal health between individuals with or without orthodontic treatment. The results have been evaluated in systematic reviews. So far, these studies have failed to indicate a positive effect of orthodontic treatment on periodontal health.

Prevalence

Periodontal Disease

Periodontal disease is common. It has been reported that more than 50% of the dentate U.S. population aged 30 to 90 have attachment loss greater than 3 mm, and more than 60% have probing depths equal to or greater than 3 mm (Albandar, Brunelle & Kingman 1999). With increasing age, the prevalence of all periodontal problems increases.

Malocclusion

Data from the third National Health and Nutrition Examination Survey indicate that 20% of the population have deviations from the ideal occlusal relationships, and only 35% of the of adults have well-aligned mandibular incisors (Proffit et al. 1998).

Orthodontic Treatment

In the United States it is estimated that about 30% of the population receives orthodontic treatment (Bollen, Cunha-Cruz & Hujoel 2007). This varies depending on socioeconomic status and race (Proffit, Fields & Moray 1998; Bollen, Cunha-Cruz & Hujoel 2007). A survey by the American Association of Orthodontics reported 5.75 million patients in orthodontic treatment in 2004 (American Association of Orthodontics 2005).

Evidence on the Relationship Between Malocclusion and Periodontal Health

The association between occlusal forces and periodontal destruction is an ongoing controversial issue, as recent publications attest (Deas & Mealey 2006). If the relationship between occlusal forces and periodontal conditions is uncertain, it shouldn’t be surprising that the relationship between malocclusions and periodontal health is even more dubious (with “malocclusions” denoting the conditions usually recognized by orthodontists as needing orthodontic corrections, such as crowding, open or deep bites, crossbites, and overjet). However, the amount of studies in this area is vast, and several review articles and systematic reviews have been conducted.

One systematic review evaluated the relationship between periodontal health and malocclusions where “malocclusions” were recorded using any malocclusion index (Bollen 2008). Because most malocclusion indices combine various components of the dental alignment and occlusion (such as crowding, overjet, etc.), it was thought that this would be a better representation of the majority of patients who usually have several deviant occlusal traits making up their malocclusion. Studies included were limited to humans and excluded those related to individuals with disabilities or specific syndromes. The exposure was malocclusion index, excluding studies evaluating occlusal interferences, balancing contacts, or parafunctions. Studies were included only if there was a control group (either a comparison group of individuals without a malocclusion or a lower severity/grade of the malocclusion). The outcome was any periodontal condition.

The electronic search criteria included malocclusion and periodontal terms and covered publications from 1960 through 2006 on Medline, Web of Science, Cochrane Library, and the gray literature, with no exclusion based on language.

The electronic search identified 2646 unique publications. Titles and abstracts (when available) were screened, and a total of 97 full publications were retrieved for review. These full articles were read, and 72 papers were excluded because they did not fulfill the search criteria. This left a total of 25 studies that reported on 35,300 subjects with a mean age of 22 (range 3 to 60). One cohort study, two case-control studies, and 22 cross-sectional studies reported on a variety of malocclusion indices, ranging from commonly used indices (such as the Occlusion Feature Index and the Dental Aesthetic Index) to custom-designed indices based on overjet/crowding and other malocclusion aspects. The outcome measures ranged from periodontitis, to various periodontal disease indices, to tooth loss. Five of the 25 studies adjusted for possible confounding variables (such as age, socioeconomic status, and/or oral hygiene). The great variability in exposure and outcome variables made it difficult to perform data extraction. However, it was possible to combine data from some of the studies. Six studies (Geiger et al. 1972; Kalamparov, Gantsev & Ershov 1972; Onyeaso, Arowojolu & Taiwo 2003; Sergl & Krause 1973; Schneider & Brendel 1981; Shinberg, Saaki/>