Mulhern 1982.

Methods	Study design: randomised parallel group, clinical trial. Conducted in USA. Number of centres: not reported. Recruitment period: not reported. Funding source: a Grant‐in‐Aid of research from the Endowment and Memorial Foundation of the American Association of Endodontists.
Participants	60 participants (31 females, 29 males, range age from 13 to 75 years, ethnic group reported: 1 Asian, 42 White and 17 Black). Inclusion criteria: non‐surgical endodontic treatment of asymptomatic mature single‐rooted teeth with necrotic pulps. Exclusion criteria: patients with severe medical conditions, using corticosteroids or anti‐inflammatory drugs and/or recent or active antibiotics therapy. Diagnostic criteria for pulpal or periapical disease: Rx and vitality test. Group 1: randomised 30, analysed 30. Group 2: randomised 30, analysed 30
Interventions	Group 1: single visit. Group 2: multiple visits (3 visits: in the interappointment period no medication was used, only a dry pledget of cotton with a double cement system of Cavit G and zinc oxyphosphate cement in the coronal access cavity was employed). 2 operators (graduate endodontic students). Rubber dam. Use of magnification loupes and canal shaping not detailed. Irrigation: 2.5% sodium hypochlorite. Working length not reported. Obturation with lateral condensation was performed using gutta‐percha and Kerr Tubli‐Seal.
Outcomes	Pain Evaluated at 48 hours after treatment (by a questionnaire) and at 1 week (clinical examination). Participants with multivisit treatment were asked to complete a questionnaire for each visit. Painkiller use Flare‐up (swelling) (see Table 3).
Notes	Patients in the experimental group received free treatment, whereas those in the control group were charged the usual clinic fee for treatment.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote " The teeth were randomly assigned to group 1 (single visit) or 2 (multiple visits)".
Allocation concealment (selection bias)	Unclear risk	Not specified.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Comment: not applicable, radiographic assessment was not among outcomes.
Incomplete outcome data (attrition bias) All outcomes	Low risk	100% of patients who entered the study were included in the final analysis.
Selective reporting (reporting bias)	Low risk	Planned outcomes reported.
Other bias	Low risk	Comment: no other source of bias identified.