Christou 1998.

Methods	Trial design: split‐mouth, (2 arms) Location: Academic Centre for Dentistry, Amsterdam, The Netherlands Number of centres: 1 Recruitment period: not reported
Participants	Inclusion criteria: adult patients not previously treated for periodontitis, 25 years old or older, at least 3 natural teeth present in each quadrant Exclusion criteria: use of antibiotics over last 3 months before baseline, use of interdental cleaning aids on a regular basis Baseline plaque: not reported Baseline periodontal status: generalised moderate to severe periodontitis, the presence of at least 1 site in each quadrant for fulfilling all following criteria: probing depths > 5 mm, bleeding on probing and radiographic evidence of alveolar bone loss, gingiva with little or no recession showing overt signs of inflammation Age at baseline (years): age range 27 to 72, mean age 37.4 Sex: 14 males/12 females Number randomised: 26 (Gp A and Gp B both had 26 participants as this was a split‐mouth study) Number evaluated: 26 (Gp A and Gp B both had 26 participants as this was a split‐mouth study) Attrition per group: none lost to follow‐up Smoking status: not reported
Interventions	Comparison: manual toothbrushing and interdental brushing versus manual toothbrushing and flossing Gp A (n = 26 evaluated) interdental brushes (frequency of use not reported) Gp B (n = 26 evaluated) dental floss (frequency of use not reported) All participants received a manual toothbrush Duration of intervention: 6 weeks Training: participants received detailed instructions for use of a manual toothbrush, dental floss and interdental brushes by a dental hygienist and were provided with by take‐home written instructions. Baseline cleaning: supragingival calculus was removed at sites where interference with interdental cleaning occurred. Compliance assessment: compliance was confirmed by a telephone call after a week of treatment. After 3 weeks, oral hygiene instructions were reinforced by the dental hygienist.
Outcomes	Measurements: at baseline and 6 weeks Dental plaque: Volpe modification of Quigley and Hein Plaque Index Periodontal disease ‐ gingivitis: measured by bleeding on probing (BOP) assessed by Angulated Bleeding Index (ABI) and Periodontal Pocket Bleeding Index (PPBI) Probing depth (PD) evaluated using a force controlled probe Adverse effects: self‐reported; participants completed a questionnaire concerning any problems with dental floss (DF) or interdental brushes (IDB), level of comfort in handling the 2 devices and their perception of efficacy of the devices. 14 participants experienced problems with use of dental floss, 2 with use of interdental brushes, 2 with both, and 8 did not encounter any problems. Attrition: no participants were lost from the study.
Funding	State Scholarship Foundation of Greece gave a grant; Entra ‐ Lactona BV provided brushes and interdental brushes.
Notes	Trial authors recorded interdental spaces that could not be entered by the assigned interdental device and excluded them from the analysis (12 sites for any size of the IDB and 2 sites for the DF). All measurements were carried out by the same examiner under the same conditions; examiner reliability was not reported, but a force‐controlled probe was used allowing confidence in the outcome assessment.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "The use of DF was randomly assigned to the left or the right side of the mouth and the use of IDB to the other side" Comment: no further information given
Allocation concealment (selection bias)	Low risk	Split‐mouth study
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding of participants was not possible
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "All procedures concerning instruction, cleaning and exclusion of sites from the analyses were performed in the absence of the examiner, keeping these recordings blind throughout the study"
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	There were no losses to follow‐up. 12 sites not accessible to any size of IDB and 2 sites not accessible to DF were excluded from the analysis. Total number of assessed sites not reported
Selective reporting (reporting bias)	Low risk	No protocol available. All outcomes stated in the Methods section were addressed in the Results.
Other bias	Unclear risk	Compliance confirmed by a telephone call after a week of treatment, but not reported.