Table 1 General characteristics of the studies included in the systematic review

Benic [2019] [29]

University of Otago

New Zealand

EG: Lozenges [Streptococcus salivarius M18 - 3 × 10⁹ CFU/lozenge]

PG: Lozenges without active bacteria

Administration: 1 month

Dosage: 2 lozenges/d

Gingival inflammation:

Gingival index [33]

Adverse effects

Sample size calculation:

Yes, but not for GI

Reliability of measurements:

Not reported

Gizani et al. [2015] [30]

University of Athens

Greece

EG: Lozenges [Lactobacillus reuteri DSM 17938 and Lactobacillus reuteri ATCC PTA 5289–10⁸ bacteria of each strain]

PG: Identical lozenges without active bacteria

Administration: from the time of enrollment until debonding (mean ± SD: 17.0 ± 6.8 months)

Dosage: 1 lozenge/d; after brushing, before bedtime

Enamel demineralization:

Gorelick et al. [34] White Spot Lesion Index

assessed photographically

Adverse effects

Sample size calculation:

Yes

Reliability of measurements:

Yes

Habib [2016] [31]

University of Toronto

Canada

EG: Lozenges [Streptococcus salivarius K12, Lactobacillus paracasei, Lactobacillus plantarum, Lactobacillus acidophilus, Lactobacillus salivarius, Lactobacillus reuteri - 3 × 10⁹ CFU/lozenge]

PG: Identical lozenges without active bacteria

Administration: 4 weeks

Dosage: loading dose - 2 lozenges, 2 times/d (after breakfast and after dinner) for 1w; maintenance dose; 2 lozenges, 1/d (after breakfast) for next 3 w

Gingival inflammation:

Modified Gingival Index [35]

Adverse effects

Sample size calculation:

Yes

Reliability of measurements:

Yes

Kohar et al. [2015] [32]

Trisakti University

Indonesia

EG₁: Lozenges [Lactobacillus reuteri - 2 × 10⁸ CFU/lozenge]

EG₂: Drink [Lactobacillus casei strain Shirota - 6.5 × 10⁶/bottle]

CG

Administration: 2 weeks

Dosage: 1 lozenge or 65 ml/d, at least 1 h after lunch

Gingival inflammation:

Papillary Bleeding Index [36]

Sample size calculation:

Not reported

Reliability of measurements:

Not reported