Data sources Cochrane Oral Health's Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), Medline, Embase, the US National Institutes of Health Ongoing Trials Register (ClinicalTrials.gov) and the World Health Organization International Clinical Trials Registry Platform.

Study selection Randomised controlled trials (RCTs), including cross-over trials on maxillary or mandibular implant overdentures with different attachment systems with at least one-year follow-up were considered. There were no restrictions on language or date of publication.

Data extraction and synthesis Data were abstracted by four reviewers with risk of bias being assessed using the Cochrane tool. Data were combined using a fixed effects meta-analysis. The GRADE approach was used to assess the overall body of evidence.

Results Six RCTs with a total of 294 mandibular overdentures were included. All of the trials were considered to be at high risk of bias. No studies on maxillary overdentures were included. For bar and ball attachments there was low quality evidence [two studies] that short-term re-treatment (repair of attachment system) was higher with ball attachments; RR =3.11(95%CI; 1.68 to 5.75) but no difference RR = 1.18(95%CI; 0.38 to 3.71) for replacements of attachment systems. There was no difference between ball and magnet systems in medium-term prosthodontic success or repair of attachment systems, but prosthodontic maintenance costs were higher when magnet attachments were used [one study - very low quality evidence]. Only one trial compared ball and telescopic attachments providing very low quality evidence.

Conclusions For mandibular overdentures, there is insufficient evidence to determine the relative effectiveness of different attachment systems on prosthodontic success, prosthodontic maintenance, patient satisfaction, patient preference or costs. No trial evidence was available for maxillary overdentures.

数据来源Cochrane口腔健康试验注册，Cochrane对照试验中央注册（CENTRAL），Medline，Embase，美国国立卫生研究院正在进行的试验注册（ClinicalTrials.gov）和世界卫生组织国际临床试验注册平台。

研究选择考虑了随机对照试验（RCT），包括对具有不同附着系统的上颌或下颌种植义齿的交叉试验，并至少随访一年。语言或出版日期没有限制。

数据提取和综合数据由四位审阅者提取，其中使用Cochrane工具评估了偏倚风险。使用固定效应荟萃分析合并数据。GRADE方法用于评估整体证据。

结果共纳入6个RCT，共294个下颌覆盖义齿。所有试验均被认为有偏见的高风险。没有关于上颌覆盖义齿的研究。对于棒和球附件，质量证据不充分[两项研究]，表明球附件的短期再处理（修复附件系统）更高。RR = 3.11（95％CI; 1.68至5.75），但无差异RR = 1.18（95％CI; 0.38至3.71），用于更换附件系统。球形和磁铁系统在中期修复牙齿或修复附着系统方面没有差异，但是当使用磁铁附件时，修复牙齿的维护成本较高[一项研究-质量非常低的证据]。只有一项试验比较了球和伸缩附件的质量很差。

结论对于下颌覆盖义齿，没有足够的证据来确定不同附着系统在修复牙齿成功，修复牙齿，患者满意度，患者偏爱或费用方面的相对有效性。没有上颌覆盖义齿的试验证据。