What do systematic reviews say?

Probiotics vs placebo or control

Probiotics may make little to no difference to the bacterial plaque index versus control (MD 0.21, 95%CI -0.55 to 0.96; very low certainty).

• Efficacy of Probiotic Consumption on Oral Outcomes in Children and/or Adolescents: A Meta-Analysis. 2024 All outcomes

  follow-up: mean 2.3 months · Healthy children and/or adolescents (<18 years) without systemic disease; RCTs from multiple countries (India, Thailand, Spain, Australia, New Zealand, Sweden, Poland, Colombia, Saudi Arabia); mostly school/community and clinic settings · Overall (all presentations pooled)
  MD 0.21 [-0.55, 0.96]
  4 studies · 171 participants
  Very low

Periodontal treatment (scaling and root planing, polishing, or surgery), alone or with oral hygiene counselling, antiseptics, or antimicrobials vs no treatment

• Treating periodontal disease for preventing adverse birth outcomes in pregnant women 2017 · Cochrane All outcomes
  Reported as a secondary periodontal outcome (Analysis 1.8); results not meta-analysed due to considerable heterogeneity (I2 91% to 100%); reduction in favour of periodontal treatment.
  2 studies
  GRADE not reported

Theory-based oral health education/promotion interventions (HBM, TPB, SCT, HAPA, TTM, PMT, SOC, PRECEDE-PROCEED, MI) vs Control (waitlist, routine/standard oral health education, or minimal intervention)

Theory-based interventions significantly reduced dental plaque (SMD -1.92; moderate certainty).

• Health promotion theory-based educational interventions for improving oral health in children and adolescents: a… 2025 All outcomes

  Post-intervention (follow-up 1 to 24 months, varies by study) · School-based and community settings; multiple countries (predominantly Iran; also Pakistan, Hong Kong, Lithuania, Thailand) · Overall
  SMD -1.92 [-2.42, -1.42]
  9 studies · 12562 participants
  Moderate

Metal-free cantilevered FDPs (feldspathic-veneered zirconia) vs Metal-ceramic cantilevered FDPs

Metal-free cantilevered FDPs (feldspathic-veneered zirconia) showed no clear difference in plaque index (PI) compared with metal-ceramic cantilevered FDPs; GRADE not reported.

• Metal‐free materials for fixed prosthodontic restorations 2017 · Cochrane All outcomes

  24 months
  MD -0.10 [-1.04, 0.84]
  1 study · 19 participants
  GRADE not reported

Clear aligners (Invisalign / thermoformed aligners) vs Conventional orthodontic appliance treatment

In randomized trials, clear aligners probably reduce plaque accumulation versus fixed appliances, though the subgroup estimate is imprecise and its CI crosses no effect (SMD -1.79, 95% CI -3.63 to 0.04; moderate certainty).

• White spot lesions, plaque accumulation and salivary caries-associated bacteria in clear aligners compared to fixed… 2023 All outcomes

  Range 1 to 18 months (maximum time-point per study) · University/hospital orthodontic clinics and private practice (multiple countries) · Study design: randomized controlled trials
  SMD -1.79 [-3.63, 0.04]
  3 studies · 111 participants
  Moderate
• White spot lesions, plaque accumulation and salivary caries-associated bacteria in clear aligners compared to fixed… 2023 All outcomes

  6 months · University/hospital orthodontic clinics and private practice (multiple countries) · Follow-up: 6 months
  SMD -2.04 [-3.37, -0.70]
  5 studies · 253 participants
  GRADE not reported
• White spot lesions, plaque accumulation and salivary caries-associated bacteria in clear aligners compared to fixed… 2023 All outcomes

  Range 1 to 12 months (maximum time-point per study) · University/hospital orthodontic clinics and private practice (multiple countries) · Study design: non-randomized studies of interventions
  SMD -1.46 [-2.77, -0.15]
  5 studies · 246 participants
  Moderate

Electronic cigarette use vs Non-smokers (non-users)

E-cigarette users tend to have a higher plaque index (more biofilm accumulation) than non-smokers (narrative synthesis of systematic reviews; ungraded).

• An Umbrella Review of E-Cigarettes' Impact on Oral Microbiota and Biofilm Buildup. 2025 All outcomes

  Oral health / dental care (community and clinical samples)
  Narrative synthesis: e-cigarette users exhibited a higher plaque index than non-smokers across included reviews (Shabil, Vamos, Youssef, Thiem, Figueredo, Yang [24,25,27,29,30,31]); the umbrella review reported no…
  6 studies
  GRADE not reported

Consumption of xylitol chewing gum by women (mothers) vs No chewing gum

Xylitol sugar-free gum significantly reduced plaque quantity versus no-gum/control (SMD -0.743, 95% CI -1.148 to -0.338), with high heterogeneity (I2 = 86.0%; ungraded).

• A Systematic Review and Meta-Analysis of the Role of Sugar-Free Chewing Gum on Plaque Quantity in the Oral Cavity. 2022 All outcomes

  End of study (last reported time point; study durations 4 days to 2 years) · Community, residential care homes, and schools; predominantly adults
  SMD -0.743 [-1.148, -0.338]
  7 studies
  GRADE not reported

Gum chewing (sugar-free) vs No chewing gum

Sugar-free chewing gum significantly reduced plaque quantity versus no-gum/control (SMD -0.778, 95% CI -1.167 to -0.390), with high heterogeneity (I2 = 86.6%) and no GRADE rating (ungraded).

• A Systematic Review and Meta-Analysis of the Role of Sugar-Free Chewing Gum on Plaque Quantity in the Oral Cavity. 2022 All outcomes

  End of study (last reported time point; study durations 4 days to 2 years) · Community, residential care homes, and schools; predominantly adults
  SMD -0.778 [-1.167, -0.390]
  7 studies
  GRADE not reported
• A Systematic Review and Meta-Analysis of the Role of Sugar-Free Chewing Gum on Plaque Quantity in the Oral Cavity. 2022 All outcomes

  End of study (last reported time point; study durations 4 days to 2 years) · Community, residential care homes, and schools; predominantly adults · Sensitivity analysis (pre-post correlation set to 0.95 for the SFG group)
  SMD -1.098 [-1.539, -0.656]
  7 studies
  GRADE not reported

Chlorhexidine (mouthrinse or gel), as part of oral hygiene care vs placebo or usual care

• Oral hygiene care for critically ill patients to prevent ventilator‐associated pneumonia 2020 · Cochrane All outcomes
  Plaque index: Fu 2019 found a significant reduction in the chlorhexidine group; Ozcaka 2012 and Scannapieco 2009 found no difference; 3 studies; no usable pooled estimate.
  3 studies
  GRADE not reported

1400/250 ppm F (amine F/SnF2) toothpaste + mouthrinse, daily vs 1400/250 ppm F (NaF) toothpaste + mouthrinse, daily

It is very uncertain whether 1400/250 ppm F (amine F/SnF2) toothpaste + mouthrinse, daily changes visible plaque index (mean change from baseline) compared with 1400/250 ppm F (NaF) toothpaste + mouthrinse, daily (very low certainty).

• Fluorides for preventing early tooth decay (demineralised lesions) during fixed brace treatment 2019 · Cochrane All outcomes

  At debond; follow-up 1.5 years
  MD -0.09 [-0.18, 0]
  1 study · 97 participants
  Very low

Interdental brushing plus toothbrushing vs Toothbrushing alone

It is very uncertain whether interdental brushing plus toothbrushing changes plaque (Quigley & Hein plaque index, Turesky modification; scale 0… compared with toothbrushing alone (very low certainty).

• Interdental brushing for the prevention and control of periodontal diseases and dental caries in adults 2013 · Cochrane All outcomes

  4 weeks (1 month)
  MD -0.95 [-1.34, -0.56]
  1 study · 62 participants
  Very low