Table 2.

Participant characteristics in included studies

Study	Inclusion and exclusion criteria	Analyzed sample [age; gender]
Benic [2019] [29] University of Otago New Zealand	Inclusion Criteria: Presence of at least 20 natural teeth; stainless steel brackets Exclusion Criteria: Systemic disease; lingual braces; living in a non-fluoridated area; periodontal disease; taking antibiotics; using non-fluoride/antibacterial toothpaste; dental fluorosis; smoking; using powered toothbrushes; lactose intolerance; allergy to dairy products; physical inability to brush	Age [range]: 10-30y EG: 32 [20F, 12 M] PG: 32 [21F, 11 M] Missing data: No
Gizani et al. [2016] [30] University of Athens Greece	Inclusion Criteria: Fixed appliances on at least eight maxillary front teeth (incisors, cuspids, and premolars); expected duration of Tx 7–24 m Exclusion Criteria: Individuals under treatment with systemic or local antibiotics up to two weeks before starting the study	Age [mean ± SD]: 15.9 ± 3.9y EG: 42 (23F, 19 M); PG: 43 (33F, 10 M) Missing data: 9 [errors in follow-up photos]
Habib [2016] [31] University of Toronto Canada	Inclusion Criteria: Healthy; aged 11–18 y; mild to moderate gingivitis; fixed appliances on at least 20 teeth for at least 5 m; complete eruption of teeth #16, 21, 23, 36, 41, 43; no active caries; no use of antimicrobial mouth rinses, probiotics, antibiotics or anti-inflammatory drugs within 1 m before the trial; undergone standard orthodontic bonding procedure Exclusion Criteria: Inability to consent or communicate fluently in English; allergies or sensitivity to lozenge ingredients; immunocompromised; major underlying medical condition or ENT problems; pregnancy; smoking, alcohol consumption; oral diseases or conditions; surgery within the past 45d or the next 90d; use of antibiotics, anti-inflammatory drugs, ongoing or use of probiotics within the past 1 m; nausea, fever, vomiting, bloody diarrhea or severe abdominal pain within the past 1 m; molar bands	Age [mean ± SD; range]: 15.69 ± 1.70y; 11-18y EG: 29 [15.75 ± 1.67y; 13F, 16 M] PG: 29 [15.64 ± 1.75y; 20F, 9 M] Missing data: 1/group [lost from to follow-up]
Kohar et al. (2015) [32] Trisakti University Indonesia	Inclusion Criteria: Healthy; no medication; aged 18-25y; fixed appliances Tx for at least 1y Exclusion Criteria: Using xylitol gums, mouthwashes, systemic antibiotics; smokers; pregnancy; topical fluoride treatment	Age [range]: 18-25y EG1: 10; EG2: 10; CG: 10 Missing data: No

CG Control group, without placebo administration, d days, EG Experimental group, F Females, M Males, m months, PG Placebo group, Tx treatment, y years