The Cochrane Library, PubMed, Medline, LILACS (Google Scholar and ISI Web of Science databases were searched without restriction. The Journal of Dental Research, Community Dentistry and Oral Epidemiology, American Journal of Orthodontics, American Journal of Orthodontics and Dentofacial Orthopedics, Angle Orthodontist, and European Journal of Orthodontics were hand searched.
Studies in humans reporting on the prevalence or severity of dental crowding and dental caries that included a comparator or control group with no or minimal crowding and assessing the association were included. Non-English articles were excluded from the review in the study-selection stage.
Data extraction and synthesis
Data extraction and evaluation of primary studies were performed independently by two reviewers. Study quality was assessed but meta-analysis was not carried out owing to the wide range of measurement indices used and study heterogeneity. A qualitative summary is presented.
Eight cross-sectional studies were included in the qualitative review. No association between crowding and caries was reported in four studies, a significant negative correlation was found in two studies, one study showed a direct and significant relationship and another study showed a positive association in the mandibular anterior region but an inverse correlation in the maxillary posterior region.
To date there are no high-quality studies to resolve the possible association between dental crowding and caries; further high-quality longitudinal studies are needed to clarify this relationship.
There is no reliable evidence for the association between dental crowding and caries.
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Ethik in der Medizin (2015)