NCT03364751.

Study characteristics
Methods	Design: RCT Study dates: November 2017 to June 2019 Recruitment: recruited at dental practices Location: Japan Setting: ambulatory setting, with data collected at dental clinics
Participants	Number randomised: 172 Characteristics: 19.2% women; mean age 48 years; all smoked > 10 cigarettes per day; no data on FTND score Specialist population: aged ≥ 30 years; Japanese ethnicity; diagnosed with generalised chronic periodontitis Inclusion criteria Current smoker, verified by urinary cotinine Smoked ≥ 10 cigarettes per day for past ≥ 5 years Aged ≥ 30 years Diagnosed with generalised chronic periodontitis Had ≥  15 natural teeth No intention to quit smoking during study Exclusion criteria Medical conditions that were a safety concern or would interfere with study Had orthodontic appliances Use drugs or supplements likely to interfere with study Pregnant or lactating Planning pregnancy during study period
Interventions	Randomised (1:1 ratio) to use an electronic HTP or continue smoking cigarettes Heated tobacco arm Device heating method: electronic Device name: THS, brand name IQOS Device manufacturer: PMI Other instructions and details: participants were given THS devices, but asked to buy their own tobacco sticks Behavioural support: none mentioned Instructions for smoking cessation/switching: switch entirely to THS use for study period Cigarette smoking arm Behavioural support: none mentioned Instructions for smoking cessation/switching: continue smoking cigarettes
Outcomes	Follow‐up time points: 13 and 26 weeks Abstinence outcomes: N/A  Safety outcomes: adverse events; serious adverse events Prevalence/sales outcomes: N/A
Notes	Funding source Tobacco industry funded: quote: "PMI is the sole source of funding and sponsor of this project". Author conflicts of interest Quote: "The work reported in this publication involved a candidate reduced risk product developed by PMI Research & Development. All authors are employees of PMI".
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No details on random sequence generation.
Allocation concealment (selection bias)	Low risk	Randomised using an interactive web/voice response system.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	All outcomes were biological.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Attrition was low across all groups, with only 1 participant failing to complete follow‐up in each study arm.
Selective reporting (reporting bias)	Low risk	Protocol was preregistered and all outcomes were reported.
Other bias	High risk	Results analysed based on actual product use, rather than product participants were randomly allocated to use.