What do systematic reviews say?

Intervention not reported

• Computerized advice on drug dosage to improve prescribing practice 2013 · Cochrane Headline outcomes only
  no estimate extracted
  3 studies · 255 participants
  Very low

MHRV vs placebo

MHRV showed no clear difference in exacerbations needing oral steroids compared with placebo (moderate certainty).

• Dehumidifiers for chronic asthma 2013 · Cochrane Headline outcomes only
  OR 0.52 [0.22, 1.24]
  1 study · 100 participants
  Moderate

Dental caries vs Caries-free status

Across the combined sample set, alpha-diversity metrics were significantly higher in caries than in health, but no pooled effect estimate was reported.

• Meta-analysis of caries microbiome studies can improve upon disease prediction outcomes. 2022 All outcomes

  Human oral samples
  Higher alpha diversity in caries than health; p<0.001 (Wilcoxon; no pooled effect size reported)
  19 studies · 2016 participants
  GRADE not reported

Dental caries vs Caries-free status

Phosphonate and phosphinate metabolism and glyoxylate and dicarboxylate metabolism had the lowest reported adjusted P values (0.04); no pooled effect estimate was reported.

• Meta-analysis of caries microbiome studies can improve upon disease prediction outcomes. 2022 All outcomes

  Human oral samples
  no estimate extracted
  19 studies · 2016 participants
  GRADE not reported

Dental caries vs Caries-free status

Beta-diversity matrices showed statistically significant ADONIS results, while clustering by study and 16S region was also observed; no pooled effect estimate was reported.

• Meta-analysis of caries microbiome studies can improve upon disease prediction outcomes. 2022 All outcomes

  Human oral samples
  no estimate extracted
  19 studies · 2016 participants
  GRADE not reported

Pre-radiotherapy extraction of healthy molar teeth vs Conservative treatment (leaving the teeth in place during radiotherapy, with oral health education and disease prevention: oral hygiene, fluoride, diet advice)

The review found no eligible studies for this question.

• Dental extractions prior to radiotherapy to the jaws for reducing post‐radiotherapy dental complications 2013 · Cochrane All outcomes
  no estimate extracted
  0 studies
  No studies found

Pre-radiotherapy extraction of diseased molar teeth vs Conservative treatment (restoration of the teeth and leaving them in place during radiotherapy, with oral health education and disease prevention: oral hygiene, fluoride, diet advice)

The review found no eligible studies for this question.

• Dental extractions prior to radiotherapy to the jaws for reducing post‐radiotherapy dental complications 2013 · Cochrane All outcomes
  no estimate extracted
  0 studies
  No studies found

Pre-radiotherapy extraction of healthy molar teeth vs Conservative treatment (leaving the teeth in place during radiotherapy, with oral health education and disease prevention: oral hygiene, fluoride, diet advice)

The review found no eligible studies for this question.

• Dental extractions prior to radiotherapy to the jaws for reducing post‐radiotherapy dental complications 2013 · Cochrane All outcomes
  no estimate extracted
  0 studies
  No studies found

Pre-radiotherapy extraction of diseased molar teeth vs Conservative treatment (restoration of the teeth and leaving them in place during radiotherapy, with oral health education and disease prevention: oral hygiene, fluoride, diet advice)

The review found no eligible studies for this question.

• Dental extractions prior to radiotherapy to the jaws for reducing post‐radiotherapy dental complications 2013 · Cochrane All outcomes
  no estimate extracted
  0 studies
  No studies found

Pre-radiotherapy extraction of diseased molar teeth vs Conservative treatment (restoration of the teeth and leaving them in place during radiotherapy, with oral health education and disease prevention: oral hygiene, fluoride, diet advice)

The review found no eligible studies for this question.

• Dental extractions prior to radiotherapy to the jaws for reducing post‐radiotherapy dental complications 2013 · Cochrane All outcomes
  no estimate extracted
  0 studies
  No studies found

Pre-radiotherapy extraction of healthy molar teeth vs Conservative treatment (leaving the teeth in place during radiotherapy, with oral health education and disease prevention: oral hygiene, fluoride, diet advice)

The review found no eligible studies for this question.

• Dental extractions prior to radiotherapy to the jaws for reducing post‐radiotherapy dental complications 2013 · Cochrane All outcomes
  no estimate extracted
  0 studies
  No studies found

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

E-cigarette use is associated with more cariogenic bacteria and increased dental caries risk compared with non-smokers (narrative synthesis; 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 use linked to increased cariogenic bacteria (S. mutans, Lactobacilli) and worsening dental caries, with flavored e-liquids noted as a caries risk factor (Zieba, Camoni, Yang…
  3 studies
  GRADE not reported

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

E-cigarette use is associated with self-reported gingivitis compared with non-smokers (single included review; 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: a meta-analysis within Camoni et al. combining 6 primary studies found an association between e-cigarette use and self-reported gingivitis, with high heterogeneity (Camoni [28]); the umbrella…
  1 study
  GRADE not reported

Electronic cigarette use vs Traditional (conventional) cigarette smokers

E-cigarette users tend to have a lower plaque index and less periodontal harm than traditional cigarette smokers, although still worse than non-smokers (narrative synthesis; ungraded).

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

  Oral health / dental care
  Narrative synthesis: plaque accumulation and periodontal harm were less pronounced in e-cigarette users than in traditional cigarette smokers; cigarette smokers had a significantly higher plaque index than e-cigarette…
  4 studies
  GRADE not reported

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

E-cigarette users appear more likely to develop periodontal disease and worse periodontal parameters than non-smokers (narrative synthesis; 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 use associated with increased risk of periodontal and gingival disease and worse periodontal parameters vs non-smokers (Tattar, Shabil, Figueredo, Yang [23,24,30,31]); no pooled…
  7 studies
  GRADE not reported

Antioxidants (lycopene, curcumin, Oxitard) vs Placebo or no active treatment

The review found no eligible studies for this question.

• Interventions for managing oral submucous fibrosis 2024 · Cochrane All outcomes
  The trials did not measure hospital admission.
  0 studies
  No studies found

Physiotherapy (tongue-spatula jaw exercises) vs No active treatment (control)

It is very uncertain whether physiotherapy (tongue-spatula jaw exercises) changes maximal mouth opening (interincisal distance) compared with no active treatment (very low certainty).

• Interventions for managing oral submucous fibrosis 2024 · Cochrane All outcomes

  3 to 6 months
  MD 0.50 [-7.72, 8.72]
  1 study · 24 participants
  Very low

Intralesional steroid injection plus adjunctive treatment vs steroid injection

Intralesional steroid injection plus adjunctive treatment showed no clear difference in maximal mouth opening (interincisal distance) compared with intralesional steroid injection alone (low certainty).

• Interventions for managing oral submucous fibrosis 2024 · Cochrane All outcomes

  Less than 3 months
  MD -0.03 [-2.48, 2.43]
  2 studies · 148 participants
  Low
• Interventions for managing oral submucous fibrosis 2024 · Cochrane All outcomes

  3 to 6 months
  MD -0.85 [-3.31, 1.61]
  2 studies · 148 participants
  Low

Topical curcumin gel vs Topical aloe vera gel

It is very uncertain whether topical curcumin gel changes maximal mouth opening (interincisal distance) compared with topical aloe vera gel (very low certainty).

• Interventions for managing oral submucous fibrosis 2024 · Cochrane All outcomes

  Less than 3 months
  MD -0.64 [-3.91, 2.63]
  1 study · 60 participants
  Very low

Buccal fat pad pedicle plus placental extract vs Buccal fat pad pedicle alone

It is very uncertain whether buccal fat pad pedicle plus placental extract changes maximal mouth opening (interincisal distance) compared with buccal fat pad pedicle alone (very low certainty).

• Interventions for managing oral submucous fibrosis 2024 · Cochrane All outcomes

  Less than 3 months
  MD 7.80 [4.90, 10.70]
  1 study · 10 participants
  Very low