Jo 2015.

Methods	Study design: cross‐over RCT Conducted in: Japan Graduate Dental School, Tokyo Number of centres: 1 Recruitment period: started August 2013 Funding source: supported by the Japanese Society for Promotion of Science Study duration: until one month follow‐up after denture insertion. August 2013 to October 2014
Participants	Patients who were edentulous in both arches and who required a new pair of dentures ‐ 11 males (46%) and 13 females (54%), with average age of 74 ± 9.6 years. More than 50% of participants in both groups belonged to the American College of Prosthodontics (ACP) class III. Inclusion criteria: ability to independently travel to the clinic for prosthodontics of TMDU Hospital Faculty; adequate understanding of written and spoken Japanese; ability to understand and respond to a questionnaire. Exclusion criteria: dementia or existing psychiatric conditions; current use of dentures 277 participants recruited by telephone, 248 declined to participate, 29 assessed for eligibility, 2 excluded, 27 randomised and allocated to two groups of 14 and 13. Total of three participants withdrew (2 in the first phase and 1 in the second phase). All participants gave informed consent, signed a letter of consent, and underwent a preliminary examination that included a panoramic radiographic survey.
Interventions	The only difference between the two intervention was at the impression stage: the simplified method of fabricating CD used single‐stage impression for mandibular impression and two stage‐two step for maxillary impression; the conventional method used two stage‐two step final‐impression method. All other steps were the same for both groups. Two dentists with 10 to 12 years' experience performed the clinical procedure. Intervention group: simplified method Preliminary impression: alginate impression materials with stock metal tray. Final impression: custom tray fabricated autopolymerising resin, border moulding with green stick, and final impression with silicone (final cast not used for processing primary cast used) Jaw relation: single maxillomandibular relation record without facebow transfer and intraoral gothic arch tracing and articulated using average value articulator Try‐in: done Denture insertion: denture inserted and adjusted four times every week Intervention group: conventional method Preliminary impression: alginate impression materials with stock metal tray Final impression: custom tray fabricated autopolymerising resin, border moulding with green stick and final impression with silicone Jaw relation: single‐sitting maxillomandibular relation record without facebow transfer and intra oral gothic arch tracing and articulated using average value articulator Try‐in: done Denture insertion: denture inserted and adjusted four times every week Washout period was one month, and relined old dentures were used during the washout period.
Outcomes	Primary outcome: general participant satisfaction with the new dentures measured using 100‐mm visual analogue scales (VAS) from 0 = completely dissatisfied to 100 = completely satisfied Secondary outcome Oral health‐related quality of life (OHRQoL) measured using OHIP‐EDENT‐J. OHIP‐EDENT‐J has been cross‐culturally adapted for the Japanese population.
Notes	The major difference between the two groups was that in the simplified method group, two‐stage final mandibular impression was used as a dummy and not used for processing, but the maxillary two‐stage final impression was used for processing. The authors confirmed the same when contacted. UMINCTR Clinical Trial, unique trial number: UMIN000009875
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Allocation to the C‐S and S‐C groups was performed based on the classification system for complete edentulism of The American College of Prosthodontists (ACP) with stratified randomisation."
Allocation concealment (selection bias)	Low risk	Quote: "The C‐S group had the conventional method used first, followed by the simplified method. The S‐C group went through the procedures in the reverse order. None of the clinicians or participants were told about the methods or the order of allocation."
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: "Blinding of the clinicians, the laboratory workers, and the researcher who performed assessments and analysis of outcomes was impossible because they could view the master casts." Quote: "Blinding of participants was possible as they were not told the order of fabrication, which method was used first (simplified or conventional), and the number of clinical appointments was the same in the conventional and simplified method groups, due to the inclusion of the mandibular final dummy impressions in the simplified method."
Blinding of outcome assessment (detection bias) All outcomes	High risk	Quote: "Blinding of the clinicians, the laboratory workers, and the researcher who performed assessments and analysis of outcomes was impossible because they could view the master casts."
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: total number of participants was 27, allocated randomly to two groups of 14 and 13. Total of 3 participants withdrew (2 in the first phase and 1 in the second phase). All were accounted for in the final analysis.
Selective reporting (reporting bias)	Low risk	Comment: all outcomes reported as planned
Other bias	Low risk	No other bias found