Table 2.

Probiotics: Summary of selected studies.

Reference(s)	Study Design	Probiotics	Objectives	Probiotic Administration	Mains Results and Limitations *
Madhwani et al. (2011) [41]	In vitro	L. reuteri ATCC 55730 L. reuteri ATCC PTA 5289	Investigation of the effects of an oral probiotic bacterium, Lactobacillus reuteri on the composition of nascent plaques (grown in short-term hydroxyapatite disc models) and in steady-state, continuous culture, in vitro dental plaques. Determination of the ecological fate of the probiotic bacterium in continuous culture in vitro plaques.	Not relevant	The introduction of L. reuteri bacteria to in vitro oral models resulted in alterations in both nascent and developed plaque ecosystems, which included increases in numbers of exogenous lactobacilli but also in increases in streptococci and Gram-negative anaerobes. L. reuteri bacteria persisted and potentially integrated into continuous culture dental plaque biofilms for at least 20 days following cessation of dosing. * In vitro study
Jiang et al. (2016) [42]	In vitro	L. rhamnosus GG	Investigation of the ability of probiotic Lactobacillus rhamnosus GG to integrate in oral biofilm and affect its species composition.	Not relevant	L. rhamnosus lowered the biofilm-forming ability of F. nucleatum and successfully integrated in all oral biofilms. L. rhamnosus reduced the counts of S. sanguinis and C. albicans L. rhamnosus only slightly reduced the adhesion of S. mutans. C. albicans significantly promoted the growth of L.GG. * In vitro study
Mendi et al. (2016) [43]	In vitro	L. rhamnosus ATCC9595	Determination of P. gingivalis modulatory effects on the inflammatory response of gingival stromal stem cells (G-MSSCs), including the release of CXCL8, and the expression of TLRs Determination of the L. rhamnosus preventive effect on CXCL8 inhibition in experimental inflammation.	Not relevant	L. rhamnosus showed higher adhesive properties than P. gingivalis on G-MSSCs. When G-MSSCs were pretreated with L. rhamnosus before P. gingivalis stimulation, CXCL8 secretions were found to increase. * In vitro study
Albuquerque-Souza et al. (2019) [44]	In vitro	L. reuteri DSM 17938, L. rhamnosus Lr-32™, L. rhamnosus HN001™, L. acidophilus LA-5™, L. acidophilus NCFM®, L. casei 324 m, Bifidobacterium longum subsp. infantis ATCC15697, B. animalis subsp. lactis BB-12™, B. breve 1101A, B. longum 51A, B. pseudolongum 1191A, B. bifidum	Evaluation of the effect of several clinical isolates and commercially available Lactobacillus sp. and Bifidobacterium sp. On gingival epithelial cells (GECs) challenged by P. gingivalis.	Not relevant	Probiotics may prevent cell death and reduce bacterial adhesion and invasion by P.gingivalis. Probiotics can modulate the inflammatory response mediated by P. gingivalis in GECs IL-1β and TNF-α synthesis stimulation decreases when co-culture with P. gingivalis and L. rhamnosus or bifidocteria (B.longum, B. animalis, B. pseudolongum, B. bifidum) or L. salivarius. CXCL8 secretion increases when co-culture with P. gingivalis and L. salivarius or L. rhamnosus. * In vitro study
Jaffar et al. (2016) [45]	In vitro	L. acidophilus JCM, L. casei subsp. rhamnosus NBRC 3831, L. delbrueckii subsp. casei JCM 1012, L. fermentum JCM 1137, L. fermentum NBRC 15885, Lactococcus lactis NBRC 12007, L. casei NBRC 15883, Leuconostoc fructosum NBRC 3516, Leuconostoc mesenteroides IAM 1046, L. plantarum NBRC 15891, L. johnsonii NBRC 13952, L. sake NBRC 3541, L. paracasei subsp. paracasei NBRC 3533	Evaluation of the potential of probiotic bacteria as a degrading agent against the periodontal pathogen A. actinomycetemcomitans and elucidation of the mechanisms underlying the observations made.	Not relevant	Probiotic bacteria demonstrate a robust degradation activity on A. actinomycetemcomitans Y4 and OMZ 534 strain, and a moderate effect against SUNY 75 strain Lipase enzyme from probiotic strains might be an influential factor in the biofilm degradation against A. actinomycetemcomitans Y4 and OMZ 534 strains. * No measurement of biofilm viability, In vitro study
Oliveira et al. (2017) [46]	Experimental study in rats (n = 32; 8 controls without EP, 8 EP only, 8 control + probiotic, 8 EP + probiotic group)	Bifidobacterium animalis subsp. lactis HN019	Evaluation of effects of topical administration of probiotic bacteria of the genus Bifidobacterium on experimental periodontitis (EP) in rats	Subgingival irrigation with 1 mL of suspension containing 1.9 × 109 CFU of B. lactis HN019 on days 0, 3, and 7.	Compared with group EP, group EP-HN019 presented lower proportions of some Gram-negative anaerobic bacteria-like species involved in the pathogenesis of periodontal diseases Group EP-HN019 presented levels of IL-1b and an IL-1b/IL-10 ratio that were significantly reduced compared with group EP. * No identification of the subgingival microbiota before EP.
Invernici et al. (2020) [47]	randomized placebo-controlled study (n = 30, 15 Scaling root planning + placebo and 15 Scaling root planning + probiotic)	Bifidobacterium animalis subsp. lactis HN019	Evaluation of the effects of B. lactis HN019 in non-surgical periodontal therapy in generalized chronic periodontitis patients. Investigation of the oral epithelial cell adhesion and antimicrobial properties of B. lactis HN019.	Lozenge (109 CFU) intake 30 days after non-surgical periodontal therapy.	B. lactis HN019 reduced the adhesion of P. gingivalis to buccal epithelial cells. B. lactis HN019 inhibit the growth of P. gingivalis, P. intermedia, F. nucleatum and A. actinomycetemcomitans in in vitro sensitivity tests. * Sample size
Dassi et al. (2014) [48]	placebo-controlled, parallel study (n = 12; 5 in control group, 7 in probiotic group)	Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus paracasei	Assessment of the impact on the overall saliva microbiome structure of a short-term probiotic intervention	100 g of a commercial probiotic product containing milk fermented (1 day).	Short-term probiotic intake significantly increases the complexity of the community with Steptococcus and Actinomyces as the most involved genera. Absence of significant changes detected in the metabolic structure of probiotic versus control samples. The two Lactobacillus strains present in the probiotic product were not detected in probiotic-intake samples. * Short probiotic intake, Sample size (n = 12)
Dassi et al. (2018) [49]	Cross sectional study (n = 21)	Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus paracasei	Verification of the hypothesis that the intake of commercially available probiotic products has a directly effect on the diversity and composition of the saliva microbiome.	100 g of a commercial probiotic product containing milk fermented (1 day).	The intake of commercially available probiotic products has a directly effect on the diversity and composition of the saliva microbiome, at least at short timescales. The overall taxonomic and abundance distribution of bacterial genera is however minimally influenced by probiotic intake. * Study design, sample size
Becirovic et al. (2018) [50]	Cross sectional study (n = 60)	Lactobacillus acidophilus La-5, Bifidobacterium Bb-12, Lactobacillus rhamnosus GG	Assessment of the effect of daily intake of a probiotic milk drink on the composition of bacterial species in dental supra- and subgingival biofilms.	200 mL probiotic milk beverage each day during 3 weeks	Influence of probiotics on bacteria in subgingival plaque was less than in supragingival plaque. The probiotic has led to a decrease in bacteria Aggregatibacter actinomycetemcomitans, Actinomyces israelii, Actinomyces viscosus, Campylobacter rectus, Eikenella corrodens, Eubacterium saburreum, Fusobacterium nucleatum ssp. nucleatum, Porphyromonas endodontalis, Prevotella intermedia, Porphyromonas gingivalis, Parvimonas micra, Prevotella nigrescens, Streptococcus intermedius, Treponema denticola, Tannerella forsythia in supragingival plaque. In the subgingival plaque a decrease of Actinomyces viscosus, Fusobacterium nucleatum ssp. nucleatum, Treponema socranskii ssp. Socranskii * Study design, sample size
Tada et al. (2018) [51]	Randomized placebo-controlled study (n = 30; 15 placebo group, 15 probiotic group)	L. reuteri DSM 17938, L. reuteri ATCC PTA 5289	Investigation of the effects of a probiotic tablet containing Lactobacillus reuteri in peri-implantitis patients.	One tablet a day for 6 months with 1 × 108 CFU L. reuteri strains DSM 17938 and ATCC PTA 5289.	Negligible changes were observed in the bacterial flora around implants * Sample size, No evaluation of L. reuteri colonization.
Kõll et al. (2008) [52]	In vitro	L. acidophilus, L. crispatus, L. delbrueckii, L. gasseri, L. salivarius, L. paracasei, L. plantarum, L. rhamnosus, L. fermentum, L. oris	Characterization of oral lactobacilli for their potential probiotic properties according to the international guidelines for the evaluation of probiotics. Selection of oral lactobacilli strains that could eventually be used as probiotics for oral health.	Not relevant	Several human oral lactobacilli possess good functional probiotic properties like antimicrobial activity against oral pathogens as well as high tolerance of environmental stress factors. These beneficial properties are better expressed in L. plantarum, L. paracasei, and L. rhamnosus, L. salivarius strains. The strains of L. plantarum differ from the natural resistance pattern of lactobacilli and therefore, should be considered non-safe * In vitro study
Teanpaisan et al. (2011) [53]	In vitro	L. paracasei, L casei, L. salivarius, L. plantarum, L. rhamnosus, L. fermentum, L. gasseri, L.mucosae, L. oris, L. vaginalis	Determination of the inhibitory effect of oral Lactobacillus against putative oral pathogens.	Not relevant	L. paracasei, L. casei, L. salivarius, L. plantarum, L. rhamnosus, L. fermentum have a strong inhibitory effect against S. mutans and Streptococcus sobrinus, as well as, Gram-negative periodontal pathogens Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans. * In vitro study
Van Essche et al. (2013) [54]	In vitro	L. rhamnosus, L. casei, L. fermentum, L. paracasei	Assessment of the antagonistic potential of oral bacteria on periodontal pathogens. Evaluation of the inhibitory effect of some commercial dietary probiotics on periodontopathogens and comparison with the inhibitory effect of orally derived beneficial bacteria.	Not relevant	The commensal oral microbiota is considered to induce a beneficial oral immune response or to interfere with periodontopathogen colonization. Probiotics showed a stronger inhibition of P. gingivalis and P. intermedia, and the oral isolated strains showed a clearly stronger inhibition of F. nucleatum and A. actinomycetemcomitans. * In vitro study
Chen et al. (2020) [55]	In vitro	L.salivarius subsp. salicinius AP-32, L. rhamnosus CT-53, L. paracasei ET-66, Bifidobacterium animalis subsp. lactis CP-9, L. acidophilus TYCA02	Evaluation of the antipathogenic efficacy of different probiotic species and their potential roles in developing functional foods to improve oral health	Not relevant	Lactobacillus salivarius subsp. salicinius AP-32, L. rhamnosus CT-53, L. paracasei ET-66 and B. animalis subsp. lactis CP-9 displayed strong antibacterial activity against the oral pathogens S. mutans, P. gingivalis, F. nucleatum and A. actinomycetemcomitans. * In vitro study
Shin et al. (2018) [56]	In vitro	Lactococcus lactis HY449	Investigation of the inhibitory effects of L. lactis on the bioactivity of periodontopathogens.	Not relevant	L. lactis has antimicrobial activity against periodontopathogens, such as F. nucleatum, P. gingivalis, T. forsythia, and T. denticola. L. lactis neutralized and inhibited inflammatory cytokines induced by lipopolysaccharides derived from these pathogens. * In vitro study
Higuchi et al. (2019) [57]	In vitro	Lactobacillus salivarius WB21 combined with green tea catechins	Evaluation of the combined use of Lactobacillus salivarius WB21 and epigallocatechin gallate for oral health maintenance.	Not relevant	Growth of P. gingivalis was strongly inhibited by co-culture with L. salivarius WB21 combined with green tea catechins * In vitro study
Zhu et al. (2010) [58]	In vitro	L. bulgaricus, S. thermophilus, L. acidophilus, Bifidobacterium	Investigation of the competition between probiotics and periodontal pathogens in vitro.	Not relevant	Probiotics are capable of inhibiting specific periodontal pathogens but have no effect on the periodontal protective bacteria (S. sanguinis). Competition between probiotics and periodontal pathogens depended on the sequence of inoculation. * In vitro study
Tobita et al. (2018) [59]	Randomized double blind placebo-controlled study (n = 16; 8 control, 8 probiotic group)	L. crispatus KT-11 (KT11)	Examination of the effects of KT-11 consumption on the oral environment in healthy volunteers.	A KT-11 food tablet (1.2 × 1010 KT-11 cells) every day for 4 weeks	Daily KT-11 intake can prevent periodontal disease through the improvement of oral conditions. KT-11 makes P. gingivalis numbers decrease. * Sample size
Iniesta et al. (2012) [60]	placebo-controlled, parallel study (n = 40; 20 control, 20 probiotic group)	L. reuteri ATCC-PTA-5289, L. reuteri DSM-17938	Investigation of the effects of an orally administered probiotic on the oral microbiota.	one tablet per day, during 28 days One tablet per day, during 28 days with L. reuteri DSM-17938 and ATCC PTA5289 at a dose of 2 × 108CFU/tablet.	L. reuteri administered in tablets resulted in a reduction in the number of Prevotella intermedia and Porphyromonas gingivalis in the subgingival microbiota, without an associated clinical impact. L. reuteri containing probiotic tablets are able to colonize the saliva and the subgingival habitat. * Differences between groups that, although not significant, may have influenced the outcomes, short time evaluation (follow up 8 weeks)
Teughels et al. (2017) [61]	Randomized placebo-controlled study (n = 30; 15 control, 15 probiotic group)	L. reuteri DSM17938, L. reuteri ATCC PTA-5289	Evaluation of the effects of L. reuteri as an adjunct to scaling and root planning.	One lozenge at the morning and one at the night during 12 weeks (L. reuteri 1 × 108 CFU for each strain)	L. reuteri lozenges resulted in significant additional clinical improvements primarily for initially moderate to deep pockets when compared to SRP alone. The microbiological differences were more moderate and primarily restricted to P. gingivalis numbers. * Sample size, No evaluation of L. reuteri colonization.
Montero et al. (2015) [62]	Randomized double blind placebo-controlled study (n = 59 patients; 29 tests, 30 placebos)	L. plantarum, L. brevis, P. acidilactici	Evaluation of the efficacy of a probiotic combination in the treatment of gingivitis Assessments of the impact of a probiotic combination on the subgingival microbiota	One lozenge at the morning and one at the night during 12 weeks (L. reuteri 1 × 103 CFU for each strain)	Use of probiotic tablets containing L. plantarum, L. brevis and P. acidilactici did not lead to significant changes in mean gingival index; although a significant reduction occurred in the number of sites with severe inflammation. The adjunctive use of the probiotic also demonstrated a significant microbiological impact by reducing the counts of T. forsythia.
Imran et al. (2015) [63]	Cross sectional study (n = 42)	L. casei Shirota	Evaluation of the impact of Probiotic drink containing Lactobacillus casei Shirota on the bacterial population in subgingival plaque in patient with chronic generalized mild to moderate periodontitis.	65 mL of probiotic milk (Yakult©) once daly for one month (108 CFU/mL of L. casei strain Shirota).	Oral administration of the probiotic lactobacilli reduced the numerical sum of A. actinomycetemcomitans, P. intermedia, P. gingivalis. No statistically significant changes were observed in the gingival index and plaque index scores. * Sample size
Sarmento et al. (2019) [64]	Randomized placebo-controlled study (n = 41; 20 control group, 21 probiotic group)	L. casei	Evaluation of the effect of petit-Suisse plus probiotic on the microbiota of children’s saliva.	50g of petit-suisse cheese daily from Monday to Friday, and the following week from Monday to Thursday (3% de L. casei)	The product with added L. casei was shown to be able to reduce A. actinomycetemcomitans, and able to maintain lower density of P. gingivalis in post treatment two weeks later. * No evaluation of probiotic change after introduction in food.
Mayanagi et al. (2009) [65]	Randomized placebo-controlled study (n = 36; 32 control group, 34 probiotic group)	L. salivarius WB21	Evaluation of the impact of oral administration of lactobacilli on the bacterial population in supra/subgingival plaque.	One tablet containing L. salivarius WB21 (6.7 × 108 CFU/tab) and xylitol (280 mg/tab) three times per day during 8 weeks.	L. salivarius WB21 administration successfully decreased the numerical sum of A. actinomycetemcomitans, P. intermedia, P. gingivalis, T. denticola, and T. forsythia in subgingival plaque at 4 weeks. No significant difference between the WB21 and the placebo groups in the direct count of any specific periodontopathic bacteria at 8 weeks. * Sample size
Sajedinejad et al. (2018) [66]	Randomized placebo-controlled study (n = 50; 50 control group, 50 probiotic group)	Lactobacillus salivarius NK02	Evaluation of the effects of probiotic mouthwash and scaling and root planning (SRP) on clinical and microbiological parameters of moderate to severe periodontitis.	Bottle of 20 mL of mouthwash was used twice a day after brushing the teeth for 28 days (108 CFU/mL of L. salivarius NK02)	Probiotic mouthwash was able to inhibit the bacterial growth on both saliva and sub-gingival crevice and exhibited antibacterial activity against A. actinomycetemcomitans. * No long term follow up
Zahradnik et al. (2009) [67]	Cross sectional pilot study (n = 12)	S. oralis KJ3sm, S. uberis KJ2sm, S. rattus JH145	Test the ability of a probiotic mouthwash, ProBiora3, to affect the levels of Streptococcus mutans and certain known periodontal pathogens in the mouth.	Bottle of 20 mL of mouthwash was used twice a day after brushing the teeth for 28 days (108 CFU/mL of S. oralis KJ3sm, S. uberis KJ2sm, S. rattus JH145).	The probiotic mouthwash was able to substantially affect the levels of dental pathogens in saliva (S.mutans) and periodontal pathogens in subgingival plaque (C. rectus and P.gingivalis) * Sample size, Young and orally healthy adults poupulation
Alanzi et al. (2018) [68]	Randomized placebo-controlled study (n = 108, 54 placebo group, 54 probiotic group)	L. rhamnosus GG, B lactis BB12	Determination of the effect of a probiotic combination on the gingival health, dental plaque accumulation, and the oral carriage of four putative periodontal pathogens in healthy adolescents	Lozenges twice a day during a four-week period (probiotic lozenge contained LGG 4.4 × 108 CFU and BB-12 4.8 × 108 CFU)	The short-term daily consumption of LGG and BB-12 probiotic lozenges improved the gingival health in adolescents The short-term daily consumption of LGG and BB-12 probiotic lozenges decreased levels of A. actinomycetemcomitans and F. nucleatum both in saliva and plaque and decreased P. gingivalis count in plaque. * Sample size, short term evaluation
Morales et al. (2018) [69]	Randomized placebo-controlled study (n = 47, 16 SRP + probiotic, 16 SRP + antibiotic, 15 SRP + placebo)	L. rhamnosus SP1	Evaluation of the effects of Lactobacillus rhamnosus SP1-containing probiotic sachet and azithromycin tablets as an adjunct to nonsurgical therapy in clinical parameters and in presence and levels of Tannerella forsythia, Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans.	1 sachet in water (150 mL) ingested once a day after brushing their teeth (2 × 107 CFU/day)	All groups showed improvements in clinical and microbiological parameters at all time points evaluated. Probiotic and antibiotic groups showed greater reductions in cultivable microbiota compared with baseline. The placebo group showed greater reduction in number of subjects with P. gingivalis compared with baseline. However, there were no significant differences between groups The adjunctive use of L. rhamnosus SP1 sachets and azithromycin during initial therapy resulted in similar clinical and microbiological improvements compared with the placebo group. * Sample size
Kobayashi et al. (2017) [70]	Experimental study in mice (n = 108; 36 tréhalose + Pg, 36 LG2055 + Pg, 36 placebo group)	L. gasseri SBT2055	Assessment of the potential of oral administration of Lactobacillus gasseri SBT2055 (LG2055) for Porphyromonas gingivalis infection	Oral intubation with a LG2055 suspension (1 × 109 CFU/200 µL/mouse) through a syringe fitted with a ball-type feeding needle once per day for 5 weeks.	LG2055 treatment significantly reduced alveolar bone loss, detachment and disorganization of the periodontal ligament, and bacterial colonization by subsequent P. gingivalis challenge. The expression and secretion of TNF-α and IL-6 in gingival tissue was significantly decreased in LG2055-administered mice after bacterial infection. * Experimental design
Maekawa et al. (2014) [71]	Experimental study in mice (n = 6; 3 probiotic, 3 placebo group)	L. brevis CD2	Determination of the Lactobacillus brevis CD2 potential on inhibit periodontal inflammation and bone loss in experimental periodontitis.	Lyopatch with L. brevis CD2 (8 × 105 CFU in 1-mm2)	L. brevis CD2-treated mice exhibited significantly decreased expression of all proinflammatory cytokines tested (TNF, IL-1β, IL-6, and IL-17A). L. brevis CD2 treatment resulted in significantly higher counts of aerobic bacteria and, conversely, significantly lower numbers of anaerobic bacteria, as compared to the placebo-treated control group. * Sample size
Keller et al. (2018) [72]	Randomized placebo-controlled study (n = 47, 23 probiotic, 24 placebo group)	L. rhamnosus PB01, L. curvatus EB10	Investigation of the clinical and the microbial effects of probiotic candidate strains in patients with moderate gingivitis.	One tablet in the morning and one in the evening 30 min after tooth brushing containing a mix of L. rhamnosus and L. curvatus (108 CFU/tablet)	The concentration of selected cytokines (interleukin (IL 1β, IL6, IL8, IL10, tumour necrosis factor alpha (TNF-α)) in gingival crevicular fluid were unaffected by the intervention as well as the salivary microbiome. * Sample size, healthy patient
Braathen et al. (2017) [73]	randomised, double-blind, placebo-controlled, cross-over trial (n = 47)	L. reuteri DSM 17938, L. reuteri ATCC PTA 5289	Comparaison of the concentration of salivary immunoglobulin A (IgA) and the selected interleukins (IL)-1β, IL-6, IL-8 and IL-10 in young individuals with presence and non-presence of Lactobacillus reuteri in saliva after a three-week intervention with probiotic lozenges.	Two lozenges per day containing the probiotic bacterium L. reuteri for three weeks (L. reuteri DSM 17938 1 × 109 CFU/lozenge, ATCC PTA5289 2 × 109 CFU/lozenge)	No differences in the cytokine levels (IL1β, IL-6, IL-8 and IL-10) were observed. Individuals with presence of L. reuteri in saliva had significantly higher concentrations of salivary IgA * Sample size, healthy patient
Jørgensen et al. (2016) [74]	randomised, double-blind, placebo-controlled, cross-over trial (n = 47)	L. reuteri DSM 17938, L. reuteri ATCC PTA 5289	Evaluation of the effect of daily ingestion of probiotic lactobacilli on the levels of secretory IgA (sIgA) and selected cytokines in whole saliva of healthy young adults.	Two lozenges per day containing L. reuteri DSM 17938, L. reuteri ATCC PTA 5289 L. reuteri DSM 17938, L. reuteri ATCC PTA 5289	No significant differences in the concentrations of salivary sIgA or cytokines were recorded between the L. reuteri and placebo interventions or between baseline and 3 weeks post-intervention levels. * Sample size, healthy patient
Hallström et al. (2016) [75]	Randomized placebo-controlled study. (n = 46; 22 probiotic, 24 placebo group)	L. reuteri DSM 17938, L. reuteri ATCC PTA 5289	Evaluation of the effects of probiotic supplements in adjunct to conventional management of peri-implant mucositis	Topical oil application (2 × 107 CFU of each strain) followed by twice-daily intake of lozenges for 3 months (1 × 108 CFU of each strain)	Topical treatment and daily intake of probiotic lozenges as an adjunct to mechanical debridement and oral hygiene instructions did not improve clinical, microbial or inflammatory variables of peri implant mucositis as compared to the use of placebo. * Sample size

CFU: colony forming units.