How many implants are necessary to stabilise an implant-supported maxillary overdenture?

Data sources Pubmed and EMBASE databases were searched from 2000 to 2017 and complemented by manual searching of the references of reviews and the full-text articles assessed for inclusion.Study selection The inclusion criteria were: (i) Randomised clinical trials (RCT), prospective or retrospective studies, and case series or case reports including at least ten totally edentulous patients rehabilitated with maxillary implant-supported overdenture; (ii) analysed one of the following outcomes: survival rate of the implants, survival rate of the overdenture and patient-reported results; (iii) had at least two years of follow-up; (iv) and were written in English language.Data extraction and synthesis The data extraction was performed by two independent reviewers.