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Oral probiotics

In periodontitis, two meta-analyses found Lactobacillus reuteri added to scaling and root planing gave small short-term gains in pocket depth and attachment. Pooled gingivitis trials of mixed strains found no significant change. Preschool trials of several strains found about 5 fewer children per 100 with cavities. Breath odor reviews disagree. Trial side effects matched placebo.

Add to Bio HackChecked 2026-11-12
Status
Sold in the US as dietary supplements, including lozenges and tablets. Not approved by the FDA as a drug for any use.
Also called
dental probiotics, probiotic lozenges, Streptococcus salivarius K12, BLIS K12, Streptococcus salivarius M18, BLIS M18, Lactobacillus reuteri, Limosilactobacillus reuteri, L. reuteri DSM 17938, L. reuteri ATCC PTA 5289, Prodentis, Lactobacillus rhamnosus, Lactobacillus paracasei
Taken for
bad breath, halitosis, gum disease, gingivitis, bleeding gums, periodontitis, cavities, tooth decay, oral health

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help5

Reported risks0

No risks sourced yet.

What people take it for, and what was found

Shown to help5

Strong

Periodontitis alongside scaling and root planing: Lactobacillus reuteri

Shown to add about 0.3 to 0.4 mm of gum attachment and reduce pocket depth with L. reuteri in adults with chronic periodontitis, in the short term.

The numbers and sources
Effect
In 3 pooled RCTs, L. reuteri added to scaling and root planing gained 0.42 mm more clinical attachment and gave a bleeding on probing reduction of 14.66 more than scaling and root planing alone in the short term. Overall pocket depth showed only a tendency (p 0.06), with significant reductions in moderate (-0.18 mm) and deep pockets (-0.67 mm) [1]. Across 11 placebo-controlled RCTs of L. reuteri alone, pocket depth fell 0.61 mm more at 21 days and 0.40 mm more at 3 months, and attachment gained 0.30 mm more at 3 months. The effect was short term [2].
Population
Adults with chronic periodontitis in RCTs [1][2].
Sources
[1], [2]
Caveats
The abstracts name the species, not the strains. Data were limited and heterogeneous, and follow-up was short [1][2].
Moderate

Periodontitis alongside scaling and root planing: mixed strains

Shown to lower plaque and gum bleeding in adults with periodontitis, with pocket depth falling significantly only in shorter studies.

The numbers and sources
Effect
Across 14 periodontitis trials, probiotics lowered plaque index (95% CI -0.54 to -0.15) and bleeding on probing (95% CI -0.58 to -0.05). Pocket depth was lower but not significantly (95% CI -0.53 to 0.03), and reached significance only in shorter studies [3]. A meta-analysis of 19 studies reported improvements in plaque, pocket depth, attachment, gingival index and bleeding with probiotics, reported as p values [4].
Population
Adults with periodontitis in RCTs of various probiotic strains [3][4].
Sources
[3], [4]
Caveats
Strains, doses and follow-up varied. One review reports p values only [4].
Limited

Gingivitis: Streptococcus salivarius M18 lozenges

Small trials from one group found lower gum inflammation and plaque than placebo in young adults with gingivitis over 4 weeks to 3 months.

The numbers and sources
Effect
In 61 young adults with gingivitis, M18 for 4 weeks lowered gingival index (effect size 0.58, 95% CI 0.05 to 1.10) and plaque (effect size 0.55, 95% CI 0.02 to 1.07) against placebo. After 4 more weeks without lozenges, only the gingival index difference remained [9]. In a 3-month trial, gingival bleeding was lower at 1 month (effect size 1.09, 95% CI 0.55 to 1.63) and 3 months (0.67, 95% CI 0.15 to 1.18), and plaque was lower at 2 and 3 months [10].
Population
Adults aged 18 to 25 [9]. 62 people with gingivitis, 60 completing [10].
Sources
[9], [10]
Caveats
Both trials come from the same group [9][10]. The first reports no funding [9].
ModerateStudied in children

Cavities in young children: mixed strains

Shown to lower cavity incidence in preschool children, 8.5% against 17.5% on placebo at the median, with low certainty.

The numbers and sources
Effect
Across 9 RCTs (2,363 preschool children), median cavity incidence was 8.5% on probiotics and 17.5% on placebo. The pooled risk difference was -0.05 (95% CI -0.10 to -0.00), and caries increment was 0.57 lower (95% CI -0.91 to -0.23) [11]. A 2026 review of 12 RCTs found that Lactobacillus rhamnosus SP1 and L. paracasei SD1, given in milk or tablets for 6 to 10 months, lowered cavity incidence and Streptococcus mutans counts. Evidence on preventing recurrence and on white spots in braces patients was limited and inconsistent [12].
Population
Preschool children [11]. Children and adolescents [12].
Sources
[11], [12]
Caveats
Certainty was low because of risk of bias, heterogeneity and inconsistency [11]. Results varied by strain, dose and delivery [12].
Limited

Cavity risk scores: Streptococcus salivarius M18 and K12

Small trials found lower plaque or better cavity risk scores in children and high-risk patients, but did not measure new cavities.

The numbers and sources
Effect
In 100 caries-active children, M18 for 3 months lowered plaque scores (p 0.05). Salivary S. mutans counts did not differ from placebo except in the children colonized most by M18 [13]. In 76 children at high risk, 90 days of M18 raised the Cariogram estimate of the chance to avoid new cavities against no treatment [14]. In 42 people at high risk, the Cariogram chance to avoid new cavities was 47.14% on K12, 41.36% on M18 and 32.50% with hygiene instructions alone (p 0.047), and only K12 differed from control [15].
Population
Children [13][14]. Patients at high caries risk [15].
Sources
[13], [14], [15]
Caveats
These trials measured plaque, bacteria or risk scores, not new cavities. Two had no placebo [14][15].

Mixed results3

Limited

Gingivitis: Lactobacillus reuteri DSM 17938 and ATCC PTA 5289 lozenges

Small trials found mixed results: lozenges lowered gum and plaque scores in pregnancy gingivitis, while tablets did not change clinical measures in another trial.

The numbers and sources
Effect
In 45 women with pregnancy gingivitis, lozenges with at least 10⁸ CFU each of L. reuteri ATCC PTA 5289 and DSM 17938, taken twice a day for about 7 weeks until birth, left gingival index and plaque index lower than placebo (p < 0.0001) [7]. In 40 people with gingivitis, daily L. reuteri tablets for 8 weeks lowered some periodontal bacteria counts and did not change clinical measures [8].
Population
Healthy women in the third trimester, 24 on lozenges and 21 on placebo [7]. 40 adults with gingivitis [8].
Sources
[7], [8]
Caveats
Two small trials with different results [7][8].
Moderate

Breath odor (halitosis): mixed strains

Mixed results: most reviews found lower breath odor scores in the short term, while one found no significant effect.

The numbers and sources
Effect
Sources disagree. Across 10 RCTs, probiotics lowered volatile sulfur compounds (SMD -1.01, 95% CI -1.93 to -0.09) and improved odor judged by smell (RR 1.31, 95% CI 1.22 to 1.41), with no change in oral health quality of life or plaque [16]. Across 7 RCTs, odor scores (SMD -0.58, 95% CI -0.87 to -0.30) and sulfur compounds (SMD -0.26, 95% CI -0.51 to -0.01) fell in the short term, and only odor scores stayed lower beyond 4 weeks [17]. A review of 4 trials (283 participants) found no significant effect (p 0.53) [18]. A review of 3 trials found lower odor scores (SMD -1.93, 95% CI -2.85 to -1.02) and no change in sulfur compounds (SMD -0.02, 95% CI -2.12 to 2.07) [19].
Population
People with halitosis in RCTs [16][17][18][19]. Strains named in one review include L. salivarius, L. reuteri, S. salivarius and Weissella cibaria [17].
Sources
[16], [17], [18], [19]
Caveats
Trials were small and heterogeneous, with possible publication bias [16]. The authors suggest larger effects when probiotics were combined with conventional treatment [16].
Limited

Breath odor (halitosis): Streptococcus salivarius K12

Small trials found mixed results: K12 lowered sulfur compounds after an antiseptic rinse, but not without one.

The numbers and sources
Effect
In 23 people with halitosis who rinsed with chlorhexidine for 3 days and then took lozenges, 85% on K12 and 30% on placebo had sulfur compound reductions above 100 ppb after 1 week [20]. In 28 people with tongue-coating halitosis who did not clean or rinse first, 30 days of K12 tablets did not change odor scores, sulfur compounds or tongue coating against placebo [21].
Population
Adults with halitosis [20][21].
Sources
[20], [21]
Caveats
Both trials were small. The positive one was a preliminary study that followed an antiseptic rinse [20].

Not shown to help1

Strong

Gingivitis: mixed strains

Not shown to improve gum inflammation, plaque or bleeding over placebo in people with plaque-induced gingivitis.

The numbers and sources
Effect
Across 11 RCTs (554 patients), probiotics did not significantly improve gingival index, plaque index or bleeding on probing in plaque-induced gingivitis, and gum fluid, IL-1β and periodontal bacteria counts did not differ from placebo [5]. In 10 double-blind RCTs, bleeding on probing ranged from 11.87% to 21.7% on probiotics and 15% to 33% on placebo. For L. reuteri, gingival index (WMD -0.48, 95% CI -1.69 to 0.72) and plaque index (WMD 0.18, 95% CI -0.23 to 0.61) did not differ from placebo [6]. A 2025 meta-analysis of 10 gingivitis studies found lower but non-significant plaque and bleeding scores [3].
Population
People with gingivitis in placebo-controlled RCTs [3][5][6].
Sources
[5], [6], [3]
Caveats
Heterogeneity was significant, and the authors of the 10-trial review call the evidence weak [6].

Doses studied

The K12 safety trial gave 1 × 10¹⁰ CFU a day for 28 days [22]. The pregnancy gingivitis trial gave lozenges with at least 10⁸ CFU each of two L. reuteri strains twice a day for about 7 weeks [7]. M18 trials lasted 4 weeks to 3 months [9][10][13], and the preschool caries trials 6 to 10 months for the strains with effects [12].

Risks

Checked, no increase found1

Moderate

Side effects in trials

Side effects were about as common on S. salivarius strains as on placebo in trials of 4 weeks to 3 months.

The numbers and sources
Effect
In 53 adults given 1 × 10¹⁰ CFU of S. salivarius K12 or placebo daily for 28 days, blood chemistry and blood counts did not differ, and adverse events were similar in frequency and intensity [22]. No significant adverse events occurred with M18 in 100 children [13], and no serious or severe adverse events were recorded in two M18 trials in adults [9][10].
Population
Healthy adults [22]. Children and young adults [13][9][10].
Sources
[22], [13], [9], [10]
Caveats
Trials lasted 4 weeks to 3 months.

Claims tested and not found

  1. That probiotics reduce plaque-induced gingivitis. Gingival index, plaque index and bleeding did not improve significantly across 11 RCTs [5].
  2. That K12 reduces tongue-coating breath odor without cleaning first. Odor, sulfur compounds and tongue coating did not differ from placebo after 30 days [21].
  3. That probiotics improve quality of life in halitosis. Oral health quality of life did not differ from control across pooled trials [16].

Sources

  1. Martin-Cabezas R, Davideau JL, Tenenbaum H, Huck O. Clinical efficacy of probiotics as an adjunctive therapy to non-surgical periodontal treatment of chronic periodontitis: a systematic review and meta-analysis. Journal of Clinical Periodontology. 2016. https://doi.org/10.1111/jcpe.12545
  2. Song D, Liu XR. Role of probiotics containing Lactobacillus reuteri in adjunct to scaling and root planing for management of patients with chronic periodontitis: a meta-analysis. European Review for Medical and Pharmacological Sciences. 2020. https://pubmed.ncbi.nlm.nih.gov/32373987/
  3. Benavides-Reyes C, Cabello I, Magán-Fernández A, et al. Clinical effects of probiotics on the treatment of gingivitis and periodontitis: a systematic review and meta-analysis. BMC Oral Health. 2025. https://doi.org/10.1186/s12903-025-05888-5
  4. Li J, Zhao G, Zhang HM, Zhu FF. Probiotic adjuvant treatment in combination with scaling and root planing in chronic periodontitis: a systematic review and meta-analysis. Beneficial Microbes. 2023. https://doi.org/10.3920/bm2022.0056
  5. Liu J, Liu Z, Huang J, Tao R. Effect of probiotics on gingival inflammation and oral microbiota: A meta-analysis. Oral Diseases. 2022. https://doi.org/10.1111/odi.13861
  6. Akram Z, Shafqat SS, Aati S, et al. Clinical efficacy of probiotics in the treatment of gingivitis: A systematic review and meta-analysis. Australian Dental Journal. 2020. https://doi.org/10.1111/adj.12733
  7. Schlagenhauf U, Jakob L, Eigenthaler M, et al. Regular consumption of Lactobacillus reuteri-containing lozenges reduces pregnancy gingivitis: an RCT. Journal of Clinical Periodontology. 2016. https://doi.org/10.1111/jcpe.12606
  8. Iniesta M, Herrera D, Montero E, et al. Probiotic effects of orally administered Lactobacillus reuteri-containing tablets on the subgingival and salivary microbiota in patients with gingivitis. A randomized clinical trial. Journal of Clinical Periodontology. 2012. https://doi.org/10.1111/j.1600-051X.2012.01914.x
  9. Babina K, Salikhova D, Doroshina V, et al. Antigingivitis and Antiplaque Effects of Oral Probiotic Containing the Streptococcus salivarius M18 Strain: A Randomized Clinical Trial. Nutrients. 2023. https://doi.org/10.3390/nu15183882
  10. Babina K, Salikhova D, Makeeva I, et al. A Three-Month Probiotic (the Streptococcus salivarius M18 Strain) Supplementation Decreases Gingival Bleeding and Plaque Accumulation: A Randomized Clinical Trial. Dentistry Journal. 2024. https://doi.org/10.3390/dj12070222
  11. Twetman S, Jørgensen MR. Can probiotic supplements prevent early childhood caries? A systematic review and meta-analysis. Beneficial Microbes. 2021. https://doi.org/10.3920/bm2021.0008
  12. Rodriguez G, Fernández Godoy E, Chaple Gil A, et al. Probiotic supplementation and dental caries prevention in children and adolescents: a systematic review of strain-specific and context-dependent effects. Clinical Oral Investigations. 2026. https://doi.org/10.1007/s00784-026-06752-8
  13. Burton JP, Drummond BK, Chilcott CN, et al. Influence of the probiotic Streptococcus salivarius strain M18 on indices of dental health in children: a randomized double-blind, placebo-controlled trial. Journal of Medical Microbiology. 2013. https://doi.org/10.1099/jmm.0.056663-0
  14. Di Pierro F, Zanvit A, Nobili P, et al. Cariogram outcome after 90 days of oral treatment with Streptococcus salivarius M18 in children at high risk for dental caries: results of a randomized, controlled study. Clinical, Cosmetic and Investigational Dentistry. 2015. https://doi.org/10.2147/CCIDE.S93066
  15. Poorni S, Nivedhitha MS, Srinivasan M, Balasubramaniam A. Effect of Probiotic Streptococcus salivarius K12 and M18 Lozenges on the Cariogram Parameters of Patients With High Caries Risk: A Randomised Control Trial. Cureus. 2022. https://doi.org/10.7759/cureus.23282
  16. Yang Y, Ge J, Chen Y, Liu H. Efficacy and safety of probiotic therapy for halitosis: a systematic review and meta-analysis of randomized controlled trials. Journal of Breath Research. 2025. https://doi.org/10.1088/1752-7163/ae23f0
  17. Huang N, Li J, Qiao X, et al. Efficacy of probiotics in the management of halitosis: a systematic review and meta-analysis. BMJ Open. 2022. https://doi.org/10.1136/bmjopen-2022-060753
  18. López-Valverde N, López-Valverde A, Macedo de Sousa B, et al. Role of Probiotics in Halitosis of Oral Origin: A Systematic Review and Meta-Analysis of Randomized Clinical Studies. Frontiers in Nutrition. 2022. https://doi.org/10.3389/fnut.2021.787908
  19. Yoo JI, Shin IS, Jeon JG, et al. The Effect of Probiotics on Halitosis: a Systematic Review and Meta-analysis. Probiotics and Antimicrobial Proteins. 2019. https://doi.org/10.1007/s12602-017-9351-1
  20. Burton JP, Chilcott CN, Moore CJ, et al. A preliminary study of the effect of probiotic Streptococcus salivarius K12 on oral malodour parameters. Journal of Applied Microbiology. 2006. https://doi.org/10.1111/j.1365-2672.2006.02837.x
  21. He L, Yang H, Chen Z, Ouyang X. The Effect of Streptococcus salivarius K12 on Halitosis: a Double-Blind, Randomized, Placebo-Controlled Trial. Probiotics and Antimicrobial Proteins. 2020. https://doi.org/10.1007/s12602-020-09646-7
  22. Burton JP, Cowley S, Simon RR, et al. Evaluation of safety and human tolerance of the oral probiotic Streptococcus salivarius K12: a randomized, placebo-controlled, double-blind study. Food and Chemical Toxicology. 2011. https://doi.org/10.1016/j.fct.2011.06.038

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