Söderholm 1982.

Methods	Trial design: parallel (3 arms) Location: Department of Periodontology, School of Dentistry, University of Lund, Malmö, Sweden Number of centres: 1 Study Duration: recruitment and follow‐up dates not reported. Participants followed‐up at 12 weeks
Participants	Participants: 69 white‐collar employees at a shipyard in Malmö, Sweden Inclusion criteria: not reported Exclusion criteria: not reported Age at baseline (years): 5‐Visit Group: 35.3 years (SE 0.8); 2‐Visit Group: 36.3 years (SE 0.8); Control Group: 35.6 years (SE 35.6) Gender: 5‐Visit Group: female 3 (13%), male 20 (87%); 2‐Visit Group: female 3 (13%), male 20 (87%); Control Group: female 3 (13%), male 20 (87%) Number randomised: 69 (5‐Visit Group: 23; 2‐Visit Group: 23; Control Group: 23) Number evaluated: 41 (5‐Visit Group: 19; 2‐Visit Group: 22; Control Group: not available)
Interventions	Intervention: 5‐Visit Group: plaque control program given during 5 visits. The interval between each of the visits was 2 days to 3 days. Each visit was scheduled as a 30‐ minute appointment 2‐Visit Group: plaque control program given during 2 visits. The 2 visits were spaced 7 days to 10 days apart and were scheduled as 60‐minute appointments. No other treatment except the oral hygiene instruction was provided at the plaque control visits. Oral hygiene instructions were given by 2 plaque control nurses. The intervention program was based on the following educational aids and principles: ‐ a step‐by‐step approach was used in teaching the patients the performance of oral hygiene procedures. New devices or techniques were not recommended or used until the patients had tried and found that those previously used were insufficient ‐ the teaching was as far as possible based upon positive reinforcement. Negative criticism was kept at a minimum ‐ plaque‐disclosing dyes and mouth mirrors were used and given to the patients ‐ repeated charting of plaque was used for instruction and feedback to the patients Control: did not receive OHA, however they were omitted at the 12‐week examination as many of these patients had started restorative care and had been given OHA. This group is not included further in this review Prophylaxis provided: "After the initial examination all participants received a dental prophylaxis. This was given in 1 visit and consisted of scaling and removal of large overhangs to remove interference with plaque control. The treatment was provided by a dental hygienist and completed within 1 hour. 2 months later the experiment started (baseline examination). This delay was used in order to ensure that reduction in bleeding tendency and periodontal pocket depth resulting from the initial prophylaxis would have occurred prior to the start of the experiment" Member of dental team delivering intervention: dental nurse and hygienist Frequency of intervention: intervention groups: 5 visits with OHA or 2 visits with OHA Intensity of intervention (length of time): 5‐Visit Group: 150 minutes; 2‐Visit Group: 120 minutes Setting: secondary care Disease level: not reported
Outcomes	Plaque score: the percentage of tooth surfaces (mesial, buccal, distal and lingual) with plaque. Plaque was defined as the soft material on the tooth surfaces which stains dark red with an erythrosine‐disclosing solution (Diaplac Rondell, Astra, Sweden) and which could be removed easily with the blunt side of a probe. The mesial and distal of the teeth were evaluated from the vestibular aspect Periodontal pocket score: percentage of tooth surfaces (mesial, buccal, distal and lingual) with periodontal pockets equal to or greater than 5 mm Gingival bleeding score: percentage of gingival areas (mesial, buccal, distal and lingual) showing bleeding after probing for pocket measurement Number of teeth Age
Notes	Funding: not reported Sample size calculation: not reported Adverse effects: not reported Declarations/conflicts of interest: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "In an attempt to obtain comparable groups of subjects the individuals were first matched in combinations of 3 with the help of a computer. Different weight was attached to the above 5 recordings. The plaque score was given the greatest weight followed by their periodontal pocket score, gingival bleeding score, number of teeth and age, respectively. The 3 individuals in a matched combination were randomly placed in 1 of the 3 study groups. Males and females were treated separately. Each group originally contained 23 individuals (20 males and 3 females)" Comment: insufficient information on the method of random sequence generation
Allocation concealment (selection bias)	Unclear risk	Not mentioned Comment: insufficient information on allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Quotes: "The treatment was provided by a dental hygienist and completed within 1 hour" and "Oral hygiene instructions were given by 2 plaque control nurses. At random, half of the participants in each of the 2 experimental groups was assigned to 1 of the nurses and the remaining half to the other nurse" Comment: patient and personnel would have been aware of allocation (5 visits versus 2 visits). Blinding of participants was not possible; it is unclear the influence this would have on the risk of bias for this domain
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quotes: "The clinical examinations were performed by 2 of the authors (GS and NN). Each of these examiners scored the same subjects throughout the experiment. The 2 examiners scored equal numbers of subjects in each of the 3 study groups, and were not aware to which study group the individual subjects belonged" and "Each of these (2) examiners scored the same subjects throughout the experiment...and were not aware to which study group the individual subjects belonged" Comment: the examiner did not know which group the participants they were assessing had been assigned to
Incomplete outcome data (attrition bias) All outcomes	Low risk	12‐week follow‐up data reported for intervention groups as per study protocol with additional 12‐, 24‐, 36‐ and 48‐month data also reported 12‐month follow‐up 5‐Visit Group: 23 to 19; 2‐Visit Group: 23 to 22 24‐month follow‐up 5‐Visit Group: 19 to 17; 2‐Visit Group: 22 to 21 36‐month follow‐up 5‐Visit Group: 17 to 19; 2‐Visit Group: 21 to 19 48‐month follow‐up 5‐Visit Group: 19 to 18; 2‐Visit Group: 19 to 20 Comment: all groups data reported as per initial study protocol
Selective reporting (reporting bias)	Low risk	All outcomes in methods section were reported
Other bias	Low risk	No apparent other bias