Overdentures: The effect of attachment systems on clinical performance

Overdenture - ball attachments

Implant supported overdentures are an alternative option for the rehabilitation of edentulous patients. Studies have demonstrated good implant survival rates and improvement in quality of life however there are maintenance and complication rates with overdenture attachments.

The aim of this review was to compare the behaviour of overdentures supported by bar and clip or ball and O-ring attachments regarding retention, maintenance, masticatory efficiency, bone loss, and patient satisfaction.


Searches were conducted in the PubMed, Web of Science and OpenGray databases. Clinical trials that compared overdentures supported by bar and clip and ball and O-ring attachments examining one of the outcomes: retention, bone loss, masticatory efficiency, or patient satisfaction were considered.  Risk of bias was assessed using the Cochrane domain-based tool. A narrative summary of the findings was presented.


  • 17 studies were included, retention was assessed in 3 studies, masticatory efficiency in 3, bone loss in 7 and patient satisfaction in 9.
  • 3 studies reported retention with bar and clip and ball and O-ring attachments. One showed no difference, one demonstrated better results with bar and clip and the other found better outcomes with O-ring attachments.
  • 3 RCTs compared 1 or more masticatory aspects of the two systems observing no differences with regard to the mastication or maximum occlusal force of the participants.
  • 7 RCTs evaluated bone loss around implants supporting mandibular overdentures. No difference in bone loss was seen between overdentures supported by bar and clip or ball and O-ring attachments in 6 studies. One study reported greater vertical bone loss with the ball and O-ring attachment on the buccal, mesial, and distal surfaces.
  • 9 RCTs evaluated patient satisfaction with all studies reporting no difference in general satisfaction. I study reported higher satisfaction regarding overdenture stability using a ball and O-ring attachment after 10 years. And one study found higher satisfaction in patients with a bar and clip attachment regarding retention and stability after 8 years.


The authors concluded: –

  1. Mastication, bone loss, and patient satisfaction were not influenced by the attachment type (bar and clip or ball and O-ring) used for mandibular overdentures.
  2. There is a tendency for better initial retention with the bar and clip attachments; however, other factors such as time of use, distance between the implants, and angulation of the implants can also significantly affect this variable and should be taken into consideration.


This review aims to compare the effectiveness of two overdenture attachment systems. While 3 databases have been searched there is a lack of detail about the process .  Although the authors indicate that risk of bias has been assessed details are not included in a table or as a clear summary in the text.

It is interesting to note that a 2018 Cochrane review of the effectiveness of attachment systems (Dental Elf – 17th Oct 2018) which covered a broader range of systems than the current review found insufficient evidence for determine the relative effectiveness of different types of overdenture attachment systems. None of papers included in this new review was published after the Cochrane review with only 3 of the RCTs being common to both reviews. In addition, 3 of the studies included in this new review were excluded by the Cochrane team. Whether this review adds any new information is questionable and it is also disappointing that there is no mention of the Cochrane review in either the introduction or discussion of this review.


Primary Paper

Gonçalves F, Campestrini VLL, Rigo-Rodrigues MA, Zanardi PR. Effect of the attachment system on the biomechanical and clinical performance of overdentures: A systematic review [published online ahead of print, 2019 Sep 18]. J Prosthet Dent. 2019;S0022-3913(19)30349-X. doi:10.1016/j.prosdent.2019.03.024

Review protocol on PROSPERO


Other references

Dental Elf – 17th Oct 2018

Implant overdentures: effectiveness of attachment systems


Picture credits

By Coronation Dental Specialty Group[1]Own work, CC BY-SA 3.0, Link



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