Maintaining oral hygiene during orthodontic treatment remains one of the ongoing challenges in clinical practice.
Fixed appliances, in particular, create plaque-retentive areas that can increase gingival inflammation and contribute to halitosis through the accumulation of volatile sulphur compounds (VSCs). While aligners may simplify oral hygiene to some extent, patients still require consistent maintenance throughout treatment.
Probiotics have increasingly been proposed as a non-invasive strategy to rebalance the oral microbiome and reduce volatile sulphur compound production. Until recently, however, their clinical effectiveness in orthodontic patients remained relatively underexplored.
A recent pair of randomised controlled trials investigated whether a daily probiotic lozenge could improve oral health and reduce halitosis in orthodontic patients treated with either fixed appliances or aligners.
Our Summary
The two trials investigated the effects of a probiotic lozenge containing Lactobacillus salivarius Oral S1 and Vitamin D3 in orthodontic patients.
One study involved patients wearing fixed appliances, while the other focused on aligner patients. In both trials, participants were randomly assigned to either a probiotic or placebo group for one month.
Researchers assessed plaque levels, gingival health, and halitosis-related volatile sulphur compounds at baseline, after treatment, and two months following discontinuation.
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The Findings
Patients wearing fixed appliances who used the probiotic demonstrated improvements in plaque control, gingival health, and halitosis-related measures compared with placebo.
Aligner patients also experienced reductions in halitosis markers, although improvements were more pronounced in the fixed appliance group.
Notably, patients with fixed appliances showed the greatest improvements overall, which is unsurprising given the more challenging oral hygiene environment created by brackets and wires.
Interestingly, the benefits reduced gradually after the probiotics were discontinued, suggesting that ongoing use may be necessary to maintain the improvements achieved during treatment.
The paper concluded that probiotic lozenges may represent a simple and well-tolerated adjunct to support oral health during orthodontic treatment, particularly in patients wearing fixed appliances.
Clinical Interpretation
One of the more interesting aspects of this study is that it focuses on an area of orthodontic treatment that often receives less attention than biomechanics or tooth movement itself.
Oral hygiene, gingival inflammation, and halitosis can significantly influence the patient experience throughout treatment, particularly in fixed appliance cases where plaque retention becomes more difficult to manage over time.
The findings suggest that probiotics may offer a relatively simple adjunctive strategy alongside standard oral hygiene instruction, particularly for patients struggling with plaque accumulation or halitosis during treatment.
At the same time, the rebound effect observed after discontinuation reinforces an important principle seen across many behavioural and biological interventions: maintaining improvement often requires consistency over time rather than short-term intervention alone.
Study Limitation
The two trials were conducted across different centres using different patient demographics, with adolescents treated using fixed appliances and adults treated using aligners. This limits direct comparison between the groups.
About Dr. Jamal
Dr. Jamal Giri is an orthodontist and associate professor at B.P. Koirala Institute of Health Sciences in Nepal. He obtained his orthodontic training from the Institute of Medicine, Tribhuvan University, Nepal, in 2014.
Currently pursuing a PhD at the University of Adelaide, Dr. Jamal’s research focuses on the genetic and environmental factors influencing malocclusion development. He also holds a postgraduate certificate in clinical education from the University of Edinburgh and a master’s in medical education from the University of Nottingham.
Dr. Jamal teaches on the Diploma in Orthodontics & Dentofacial Orthopaedics at the London Dental Institute.
Read More
Vasoglou G, Mylonopoulou IM, Angelopoulos G, Kloukos D, Pandis N, Sifakakis I. Impact of oral probiotics on oral health and halitosis in orthodontic patients treated with aligners or conventional fixed appliances vs placebo: two randomized clinical trials. European Journal of Orthodontics. 2026;48:cjag028.
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