Purpose: This study aimed to evaluate the outcomes of treatment methods used to rehabilitate adult patients with maxillary and/or mandibular edentulism after at least 5 years of follow-up. The risks, adverse effects, and cost effectiveness of these methods were also evaluated. Materials and Methods: Three databases as well as the reference lists of included publications were searched using specified indexing terms. Publications that met the inclusion criteria were read and interpreted using pre-established protocols. Quality of evidence was classified according to the GRADE system (high, moderate, low, or very low). Results: The search yielded 2,130 titles and abstracts. Of these, the full-text versions of 488 publications were obtained. After data extraction and interpretation, 10 studies with moderate study quality of evidence and 1 study with low quality of evidence regarding outcomes, risks, and adverse effects remained. Three studies on the economic aspects of treatment were also included (1 with moderate quality and 2 with low quality). Low-quality evidence showed that the survival rate of implant-supported fixed prostheses is 95% after 5 years in patients with maxillary edentulism and 97% after 10 years in patients with mandibular edentulism. The survival rate of implant-supported overdentures is 93% after 5 years (low-quality evidence). In implant-supported fixed prostheses, 70 of every 1,000 implants are at risk of failing in the maxilla after 5 years and 17 of every 1,000 implants in the mandible are at risk after 10 years. Regarding economic aspects, the evidence was insufficient to provide reliable results. Conclusions: Due to the low quality of evidence found in the included studies, further research with a higher quality of evidence is recommended to better understand the outcomes of treatment for patients with maxillary and/or mandibular edentulism.