Which final impression technique and material is best for complete and removable partial dentures?

Data sources Cochrane Oral Health's Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), Medline, Embase, the US National Institutes of Health Trials Registry (ClinicalTrials.gov) and the World Health Organization International Clinical Trials Registry Platform databasesStudy selection Randomised controlled trials (RCTs) comparing different final-impression techniques and materials for treating people with complete dentures (CD) and removable partial dentures (RPD) were included.Data extraction and synthesis Two reviewers independently extracted data and assessed risk of bias. Results were expressed as risk ratios (RR) for dichotomous outcomes, and as mean differences (MD) or standardised mean differences (SMD) for continuous outcomes, with 95% confidence intervals (CI). Meta-analysis used a random-effects model.Results Nine studies were included, eight involving CD. Six of the CD studies were at high risk of bias, two at low risk. For complete dentures there was low-quality evidence that silicone was a better final-impression material for oral health-related quality of life than alginate. There was also very low-quality evidence of no clear differences between the single-stage impression alginate and the two stage- two step elastomer groups in participant-reported quality of life using OHIP-EDENT. The RCT involving RPD altered-cast technique versus one-piece cast technique found low quality evidence of no difference between groups, for general satisfaction at one-year follow-up.Conclusions There is no clear evidence that one technique or material has a substantial advantage over another for making complete dentures and removable partial dentures. Available evidence for the relative benefits of different denture fabrication techniques and final-impression materials is limited and is of low or very low quality. More high-quality RCTs are required.