Effects of fixed orthodontic brackets on oral malodor: A systematic review and meta-analysis according to the preferred reporting items for systematic reviews and meta-analyses guidelines

Background:This systematic review and meta-analysis aimed to identify whether there is any relationship between fixed orthodontic appliances and malodor, and if self-ligating brackets (SLBs) prevent malodor better than conventional brackets (CBs).Methods:The electronic databases PubMed, Ovid, EMBASE, and the Cochrane Library were searched from inception to September 2016; a manual search was also performed. Randomized controlled and clinical controlled trials, in which experimental groups received fixed orthodontic therapy and malodor was measured, were included. Patients treated with fixed orthodontic brackets were compared with those without any treatment, and SLB systems were compared with CB systems. Two reviewers independently selected potentially relevant studies, evaluated the risk for bias, extracted essential data, and synthesized findings using Review Manager version 5.3 (Copenhagen: The. Nordic Cochrane Centre, The Cochrane Collaboration, 2014).Results:Four studies, involving a total of 152 participants, met the inclusion criteria. Fixed orthodontic appliances caused malodor from the initial visit to 2 to 3 months, but was only significant after the first week (mean difference 20.24 [95% confidence interval [CI]11.75-28.74]; P<.00001). Plaque index, gingival index, and periodontal pocket depths demonstrated no statistical differences between the SLB and CB groups after the first week. However, SLBs significantly controlled malodor better than CBs after the first week (mean difference 4.32 [95% CI 6.02 to 2.61]; P<.00001). The quality of the included studies was relatively low and relevant research in this field is quite scarce.Conclusions:Although the evidence base was relatively weak, fixed orthodontic treatment appeared to be a risk factor for malodor, independent of periodontal changes, and SLB systems controlled malodor better than CB systems.