de la Rosa 1988.

Study characteristics
Methods	Trial design: parallel (2 arms) Location: a boarding school in Monterrey, Mexico Number of centres: 1 Study duration: recruitment period not stated. Duration of study and duration of rinsing was 12 weeks
Participants	Participants: boarding school boys Inclusion criteria: quote: "For acceptance into the study, they had to have some degree of plaque‐induced gingivitis" Exclusion criteria: quote: "Those with gross oral neglect or pathoses that needed prompt care were not accepted" Baseline gingivitis: (Papillary Marginal Gingivitis Index; mean baseline score of all sites graded for individuals examined at 6 weeks) Gp A: mean 0.6933; Gp B: mean 0.6513 Age at baseline (years): range 8‐18 Gender: 100% male Number randomised: not reported Number evaluated: 92 (Gp A: 46; Gp B: 46)
Interventions	Comparison: CHX versus placebo Gp A (completers n = 46): CHX 0.12%, 15 mL, twice daily, 30 seconds, 12 weeks Gp B (completers n = 46): placebo (composition not described), 15 mL, twice daily, 30 seconds, 12 weeks Prophylaxis at baseline: quote: "...all subjects received a dental prophylaxis to remove any dental accretions" OHI: quote: "At the beginning of the studies, the subjects received soft toothbrushes and brushing instructions" Postrinsing instructions: not reported Supervised rinsing Timing of mouthrinsing in relation to toothbrushing: quote: "The evening rinsing was preceded by a one‐minute toothbrushing with a sodium fluoride dentifrice, Crest"
Outcomes	Gingivitis (gingival inflammation: Papillary Marginal Gingivitis Index, de la Rosa and Sturzenberger 1976, severity (mean score all sites) and occurrence (proportion of sites with a PMGI score ≥1)); plaque (TQH, Turesky 1970); assessed at 6 and 12 weeks follow‐up
Funding	Funding: quote: "The work was supported by a grant of the Procter & Gamble Company, Cincinnati, OH"
Notes	Sample size calculation: not reported Adverse effects: quotes: "Some mild epithelial desquamations were observed in some chlorhexidine subjects… There was no discomfort reported in association with these transient incidences in our study. Neither was there a consequence on oral health… there was an increase in extrinsic tooth stain and supragingival calculus in the chlorhexidine groups.." and "There was no lasting side effect on the oral soft tissue or the health of the users" Declarations/conflicts of interest: potential conflict of interest: the second author is a Senior Dentist at the Procter and Gamble Company and the third author is an Associate Director, Peridex Research, Procter and Gamble Company
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "..subjects were stratified by age intervals (<12 and >/= 12) and stratified by seven intervals of gingivitis scores ranging from <0.25 to >1.50. Within these strata, the subjects were distributed into the chlorhexidine or the placebo groups at random" Comment: no description of the method of random sequence generation
Allocation concealment (selection bias)	Unclear risk	No information is provided
Blinding of participants and personnel (performance bias) All outcomes	High risk	The authors report that the study is "double‐blind". The comparison group rinsed with placebo rinse, no details are given regarding the formulation or presentation of the placebo Comment: it is not clear whether the 'supervisory personnel' who dispensed the toothpaste and mouthrinse and supervised the rinsing were blind.The authors report an increase in extrinsic tooth stain and supragingival calculus in the CHX group. The higher level of tooth staining and calculus in the CHX group meant that participants could have worked out which group they were in (or that they were in the active mouthrinse group) and this could have affected their oral health behaviours and hence the outcome. The direction of this potential bias is unclear
Blinding of outcome assessment (detection bias) All outcomes	High risk	The authors report that the study is "double‐blind". Quote: "Previous records were not available at subsequent examinations nor did examiners have any knowledge as to which treatment group a given subject belonged" Comment: the authors report an increase in extrinsic tooth stain and supragingival calculus in the CHX group. The higher level of staining and calculus in the CHX group meant that the outcome assessor could not be adequately blinded and this could have affected the outcome assessment. The direction of this potential bias is unclear
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Numbers at baseline not reported, so attrition from baseline cannot be calculated. Between 6 weeks and 3 months 4 (8%) participants were lost from the CHX group and 6 (11.5%) participants were lost from the placebo group
Selective reporting (reporting bias)	High risk	The SDs for the main outcome (mean gingivitis occurrence and severity) are not reported. The ancillary outcome (plaque) is mentioned but not fully reported possibly because the result was not statistically significant
Other bias	Unclear risk	No information is provided on intra‐ and interexaminer reproducibility. The groups appear balanced for gingivitis at baseline. The authors state that the baseline scores demonstrate comparability of the test and control groups. However, the statistical significance of the differences is not reported