Maxillary overdentures supported by four implants had similar success to those supported with six implants in short term.


Stability problems and lack of retention are problems that edentulous patients often report.  The implant-supported denture is one approach to address these problems.  The aim of this trial was to compare the outcomes of maxillary overdentures supported by four or six dental implants in patients in the anterior part of the maxilla.

Adult edentulous patients with sufficient bone for implants in the anterior maxillary and mandibular region, and sufficient inter-occlusal space for a bar-supported attachment system were randomised to have either four or six dental implants with a length of at least 11 mm and a diameter of 4 mm inserted. All implants were supported with a bar.  Surgical and prosthetic procedures were standardised. Implant survival, overdenture survival, clinical scores, radiographic bone height changes, and patients’ satisfaction were assessed at 1-year.

  • 25 patients were assigned to each group.  1 patient in the 4-implant group died.
  • Implant survival was 100% in the four implants group and 99.3% in the six implants group (one implant lost).
  • Overdenture survival was 100% in both groups.
  • Mean clinical scores were low and did not differ between groups (independent Student’s t-test).
  • Mean marginal bone resorption was 0.24 ± 0.32 mm in the four implants group and 0.25 ± 0.29 mm in the six implants group.
  • Patients’ satisfaction had improved in both groups (paired Student’s t-test).

The authors concluded.

Bar-supported overdentures on four implants in the anterior maxillary region are not inferior to overdentures supported by six bar-connected implants. Implant survival was high, peri-implant conditions were healthy and patients’ satisfaction had increased significantly in both groups.


This is a relatively small study  and as the authors note this trial only took place over a short time period which is an important limitation. Should further longer terms studies confirm that 4-implant overdentures are as successful as 6-implant approaches there will be a clear cost improvement.


Slot W, Raghoebar GM, Vissink A, Meijer HJ. Maxillary overdentures supported by four or six implants in the anterior region; 1-year results from a randomized controlled trial. J Clin Periodontol. 2013 Mar;40(3):303-10. doi: 10.1111/jcpe.12051. Epub 2013 Jan 16. PubMed PMID: 23320877.


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