Data sources PubMed/Medline, Scopus and Cochrane databases supplemented by hand searches in the journals; Clinical Oral Implants Research, Journal of Oral Rehabilitation, The Journal of Prosthetic Dentistry, Journal of Prosthodontics and Journal of Dentistry.

Study Selection Randomised controlled clinical trials (RCTs), prospective studies with ≥ ten participants and follow-up periods ≥ six months, published in English, and comparing splinted and unsplinted attachment systems within the same study.

Data extraction and synthesisTwo investigators independently performed the electronic search; of which one collected the data while the other investigator verified it. A third investigator was involved in cases of disagreement. The Kappa test was also used to determine the inter-examiner agreement. The risk of bias was analysed using the Cochrane Risk of Bias Tool and the Newcastle-Ottawa scale.

Results Nine studies were included; six RCTs, two prospective studies and one crossover study, involving the placement of 984 implants in 380 patients and a mean follow-up period of five years. All implants were placed in the mandibular arch. The included studies demonstrated a low or unclear risk of bias. Both splinted and unsplinted attachment systems performed similarly, with no statistically significant differences present in marginal bone loss, complications and implant survival.

Conclusions The choice of attachment system does not seem to influence marginal bone loss, the incidence of complications or implant survival in mandibular overdentures.

数据来源PubMed / Medline，Scopus和Cochrane数据库，并在期刊中进行手工搜索作为补充；临床口腔植入物研究，口腔修复杂志，修复牙科杂志，修复口腔医学和牙科杂志。

研究选择英文发表的随机对照临床试验（RCT），前瞻性研究（≥10名参与者且随访期≥6个月），并比较同一研究中夹板和非夹板的附着系统。

数据提取和综合两名调查员独立进行了电子搜索。其中一个收集了数据，而另一位调查人员对其进行了验证。第三位调查员参与了意见分歧的案件。Kappa检验还用于确定审查员之间的协议。使用Cochrane偏倚风险工具和纽卡斯尔-渥太华量表对偏倚风险进行了分析。

结果共纳入9项研究。六项随机对照试验，两项前瞻性研究和一项交叉研究，涉及在380例患者中放置984个植入物，平均随访期为5年。所有的植入物都放置在下颌弓。纳入的研究表明偏倚风险低或不清楚。夹板式和非夹板式附着系统的性能相似，在边缘骨丢失，并发症和植入物存活率方面没有统计学上的显着差异。

结论选择附着系统似乎不会影响下颌覆盖义齿的边缘性骨丢失，并发症的发生率或植入物的存活率。