What do systematic reviews say?

Pre-operative radiotherapy (plus surgery) vs surgery

Pre-operative radiotherapy (plus surgery) showed no clear difference in locoregional control compared with surgery alone; GRADE not reported.

• Interventions for the treatment of oral cavity and oropharyngeal cancer: radiotherapy 2010 · Cochrane All outcomes

  Timing unclear
  RR 0.63 [0.28, 1.46]
  1 study
  GRADE not reported

Pre-operative and post-operative radiotherapy vs Post-operative radiotherapy alone

Pre-operative and post-operative radiotherapy showed no clear difference in disease free survival compared with post-operative radiotherapy alone; GRADE not reported.

• Interventions for the treatment of oral cavity and oropharyngeal cancer: radiotherapy 2010 · Cochrane All outcomes
  HR 1.13 [0.78, 1.64]
  1 study
  GRADE not reported

Pre-operative and post-operative radiotherapy vs Post-operative radiotherapy alone

Pre-operative and post-operative radiotherapy showed no clear difference in locoregional control compared with post-operative radiotherapy alone; GRADE not reported.

• Interventions for the treatment of oral cavity and oropharyngeal cancer: radiotherapy 2010 · Cochrane All outcomes
  HR 1.13 [0.78, 1.64]
  1 study
  GRADE not reported

Pre-operative and post-operative radiotherapy vs Post-operative radiotherapy alone

Pre-operative and post-operative radiotherapy showed no clear difference in total mortality compared with post-operative radiotherapy alone; GRADE not reported.

• Interventions for the treatment of oral cavity and oropharyngeal cancer: radiotherapy 2010 · Cochrane All outcomes
  HR 0.67 [0.35, 1.28]
  1 study
  GRADE not reported

Prefabricated metal post and core (Category II) vs Metal custom-cast post and core (Category I)

The review found no eligible studies for this question.

• Root canal posts for the restoration of root filled teeth 2007 · Cochrane All outcomes

  Minimum 6 months (planned)
  No included trial compared metal-cast posts with prefabricated metal posts (a planned primary comparison); no eligible study identified.
  0 studies
  No studies found

Dental caries vs Caries-free status

The relative abundance of S. mutans in saliva is significantly higher in caries-active than caries-free individuals (pooled SMD 1.48, 95% CI 0.45 to 2.50), but heterogeneity is very high (I2=90%); ungraded.

• Streptococcus mutans and Caries: A Systematic Review and Meta-Analysis. 2025 All outcomes

  Cross-sectional · Clinical oral-microbiome studies; saliva and/or supragingival plaque samples; 7 countries; DNA/RNA-based sequencing or microarray · Saliva sample
  SMD 1.48 [0.45, 2.50]
  5 studies · 258 participants
  GRADE not reported

Dental caries vs Caries-free status

No oral microbial taxon other than S. mutans was consistently associated with caries; alpha-diversity mostly did not differ between caries-active and caries-free groups and beta-diversity findings were mixed (ungraded, narrative).

• Streptococcus mutans and Caries: A Systematic Review and Meta-Analysis. 2025 All outcomes

  Cross-sectional · Clinical oral-microbiome studies; saliva and/or supragingival plaque samples; 7 countries; DNA/RNA-based sequencing or microarray
  Narrative synthesis (no pooled estimate): no bacterial genus or species other than S. mutans was consistently (reported in more than 2 studies) associated with caries-active status (Table 3; 15 of 19 studies for…
  Studies not reported
  GRADE not reported

Elective radical (comprehensive) neck dissection vs Elective selective neck dissection

• Interventions for the treatment of oral cavity and oropharyngeal cancers: surgical treatment 2023 · Cochrane All outcomes
  Total mortality: 2 trials reported HR but could not be pooled (different surgical procedures); neither indicated a difference (BHNCSG 1998 HR 1.14, 0.70 to 1.86; Bier 1994 HR 0.87, 0.41 to 1.83); 252 participants (2…
  2 studies · 252 participants
  Very low

Elective radical (comprehensive) neck dissection vs Elective selective neck dissection

The review found no eligible studies for this question.

• Interventions for the treatment of oral cavity and oropharyngeal cancers: surgical treatment 2023 · Cochrane All outcomes
  Locoregional recurrence: not reported.
  0 studies
  No studies found

Elective radical (comprehensive) neck dissection vs Elective selective neck dissection

• Interventions for the treatment of oral cavity and oropharyngeal cancers: surgical treatment 2023 · Cochrane All outcomes
  Adverse events (BHNCSG 1998): flap necrosis, wound infection, fistula, vascular rupture, haematoma, seroma, chyle fistula; no complications in 45/76 modified radical ND and 54/72 supraomohyoid ND; 2 vs 1 postoperative…
  1 study · 148 participants
  Low

Elective radical (comprehensive) neck dissection vs Elective selective neck dissection

It is very uncertain whether elective radical (comprehensive) neck dissection changes recurrence compared with elective selective neck dissection (very low certainty).

• Interventions for the treatment of oral cavity and oropharyngeal cancers: surgical treatment 2023 · Cochrane All outcomes

  5 years
  RR 1.21 [0.63, 2.33]
  1 study · 143 participants
  Very low

Elective radical (comprehensive) neck dissection vs Elective selective neck dissection

It is very uncertain whether elective radical (comprehensive) neck dissection changes disease-free survival (new disease, progression, and mortality) compared with elective selective neck dissection (very low certainty).

• Interventions for the treatment of oral cavity and oropharyngeal cancers: surgical treatment 2023 · Cochrane All outcomes

  5 years
  HR 0.57 [0.29, 1.11]
  1 study · 104 participants
  Very low

Genetically predicted pulp and periapical diseases vs Without pulp and periapical diseases (lower genetic liability)

Genetically predicted pulp and periapical diseases were associated with modestly higher odds of lacunar stroke (OR 1.20); ungraded MR, FDR-adjusted P 0.033.

• The contribution of oral infectious diseases in lacunar stroke based on meta-analysis and Mendelian randomization study. 2025 All outcomes

  Genetic epidemiology (European-ancestry GWAS summary data)
  OR 1.20 [1.03, 1.41]
  Studies not reported
  GRADE not reported

Hall technique vs Non-restorative cavity control (NRCC)

• Interventions for treating cavitated or dentine carious lesions 2021 · Cochrane All outcomes

  Primary dentition
  Cost-effectiveness reported narratively: HT found more cost-effective than NRCC in primary teeth (Santamaria 2018); not GRADE-rated.
  1 study
  GRADE not reported

Hall technique vs Non-restorative cavity control (NRCC)

It is very uncertain whether hall Technique (sealing with a preformed metal crown) changes failure of therapy compared with non-restorative cavity control (NRCC) (very low certainty).

• Interventions for treating cavitated or dentine carious lesions 2021 · Cochrane All outcomes

  30 months · Cavitated lesions, primary dentition
  OR 0.19 [0.05, 0.74]
  1 study · 84 participants
  Very low

Co-presence of Veillonella spp. with Streptococcus mutans vs Streptococcus mutans acidogenesis without Veillonella spp. modulation (conceptual)

The review concludes that Veillonella spp. may modulate (often inhibit) S. mutans acid production and compete for lactate substrate, potentially reducing cariogenesis, but the evidence is narrative and ungraded.

• A systematic review of Streptococcus Mutans and Veillonellae species interactions in dental caries progression:… 2025 All outcomes

  Community and clinical pediatric dental settings (USA, Hong Kong, Indonesia); saliva or dental plaque microbial sampling
  Narrative synthesis (no effect estimate): Veillonella spp. can inhibit acid production by S. mutans and compete for substrate by utilizing lactic acid, a by-product of S. mutans metabolism, as a carbon source,…
  Studies not reported
  GRADE not reported

Hall technique vs Compomer restoration or non-restorative caries treatment

Preformed metal (Hall) crowns had a low reported annual failure rate (3.1%) versus compomer (14.7%) in one RCT; low quality of evidence (ungraded).

• Clinical effectiveness of restorative materials for the restoration of carious primary teeth without pulp therapy: a… 2022 All outcomes

  2.5 years / 30 months (Santamaria 2017) · University (Germany)
  Annual failure rate (%) PMC Hall technique 3.1%; compomer 14.7%
  1 study · 169 participants
  GRADE not reported

Metal-free tooth-supported FDPs (pressed veneering ceramic) vs Metal-free tooth-supported FDPs (layered veneering ceramic)

• Metal‐free materials for fixed prosthodontic restorations 2017 · Cochrane All outcomes
  No comparative data were presented with regard to aesthetics. Aesthetics evaluated by the patient was reported dichotomously (yes/no) in the trial but no between-group estimate was presented.
  1 study
  GRADE not reported

Metal-free tooth-supported FDPs (pressed veneering ceramic) vs Metal-free tooth-supported FDPs (layered veneering ceramic)

• Metal‐free materials for fixed prosthodontic restorations 2017 · Cochrane All outcomes
  No comparative data were presented for the pre-specified secondary outcomes. The trial analyzed and reported plaque index, bleeding on probing and pocket probing depth but no between-group estimate was presented in the…
  1 study
  GRADE not reported

Metal-free tooth-supported FDPs (pressed veneering ceramic) vs Metal-free tooth-supported FDPs (layered veneering ceramic)

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

  12 and 36 months
  At 12 months 40 participants were available and at 36 months 36 participants were available. No FDP failures were reported in either group at either time.
  1 study · 40 participants
  Very low