title: Success and survival rates of mandibular overdentures supported by two or four implants: a systematic review.
abstract: This systematic review evaluated the influence played by the number of implants on the results of rehabilitation treatment with mandibular overdentures on 2 or 4 implants. The literature search was conducted using PubMed, Embase and Cochrane databases. Specific terms were used in performing a search from January 1980 to January 2013. The search strategy was applied by two reviewers who extracted the data and compared the results. Discrepancies were resolved by discussion. Great heterogeneity was seen among the selected studies, in regard to survival rates, prosthesis failure and function rates. A medium degree of quality and methodological consistency was found in one study, and no studies showed a high degree. When considering the prosthesis success rate for 2 implants, there was a variation of 23% to 100%. However, when considering the survival rate, the result was 92% to 100%. For 4 implants, prosthesis survival rates showed less variation, i.e., 97.7% to 100%. Ball attachments were the most common type of abutment for 2 implants; however, there was a higher prevalence of bar abutments for 4 implants. Rehabilitations with 2 implants showed more complications and required more maintenance according to the connection type. Given the limitations of this review, mandibular overdentures with 4 implants showed better results with respect to survival and success rates, especially those with a bar connection. Further studies comparing these two treatment types are necessary to improve the scientific evidence in this area.
authors.affiliation: Department of Dentistry, Universidade Federal do Rio Grande do Norte, NatalRN, Brazil.
authors.forename: Isabelle de Sousa
authors.initials: Ide S
authors.lastname: Dantas
authors.affiliation: Department of Dentistry, Universidade Federal do Rio Grande do Norte, NatalRN, Brazil.
authors.forename: Mariana Barbosa Câmara de
authors.initials: MB
authors.lastname: Souza
authors.affiliation: Department of Dentistry, Universidade Federal do Rio Grande do Norte, NatalRN, Brazil.
authors.forename: Maria Helena de Siqueira Torres
authors.initials: MH
authors.lastname: Morais
authors.affiliation: Department of Dentistry, Universidade Federal do Rio Grande do Norte, NatalRN, Brazil.
authors.forename: Adriana da Fonte Porto
authors.initials: Ada F
authors.lastname: Carreiro
authors.affiliation: Department of Dentistry, Universidade Federal do Rio Grande do Norte, NatalRN, Brazil.
authors.forename: Gustavo Augusto Seabra
authors.initials: GA
authors.lastname: Barbosa
mesh_terms: D003758:Dental Implantation, Endosseous / Q000379:methods; D019094:Dental Prosthesis, Implant-Supported / Q000379:methods*; D019232:Dental Restoration Failure; D003826:Denture, Complete, Lower; D003828:Denture, Overlay; D006801:Humans; D007575:Jaw, Edentulous / Q000534:rehabilitation*; D016896:Treatment Outcome