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Limited evidence appears not to support a minimum number of implants required for maxillary or mandibular overdentures' function or patient's satisfaction

Heeje Lee D.D.S. .


Systematic Review Conclusion

The number of dental implants used for the overdentures does not appear to affect the function of the overdentures or the patient's satisfaction for both maxillary and mandibular arches.

Critical Summary Assessment

This systematic review had significant limitations in its methodology and reporting due to considerable heterogeneity of original studies.

Evidence Quality Rating

Limited Evidence

Structured Abstract

Clinical Questions:

In patients requiring either a maxillary or a mandibular implant overdenture, are there reasons to recommend a certain number of implants to improve the prognosis of the overdentures?

Review Methods:

The author searched one database (Medline) for English-language articles and reviews published between 1990 and 2007. The search was limited to clinical trials, randomized controlled-clinical trials and meta-analyses. Main inclusion criteria were retention, stability, complications, longevity of the overdentures, patient satisfaction, and implant survival rates associated with the number of implants.

Main Results:

The initial search yielded 1779 articles. The author applied inclusion and exclusion criteria to select 11 articles (three observed maxilla overdentures, eight observed mandible overdentures) for final review. In the three maxillary studies, each patient received between two and seven implants; in the eight mandibular studies, each patient received between one and four implants. According to the articles, the number of dental implants did not affect patient satisfaction or the function of the dentures.


Despite the general agreement among practitioners of using a minimum four implants in the maxilla, using two implants did not compromised the longevity of the overdentures or patient satisfaction. Also for the mandibular overdentures, from 1 to 4 implants were used and the number of dental implant was not a determining factor for patient satisfaction or function of the denture.

Source of Funding:

No source of funding was reported.


Importance and Context:

Implant overdenture therapy is a widely accepted treatment option for edentulous patients. The cost of treatment mostly depends on the number of implants placed. Thus, it is important to be able to estimate the minimum number of dental implants needed without compromising the function and survival of the overdenture or patient satisfaction.

Strengths and Weaknesses of the Systematic Review:

The review had several significant weaknesses: 1) the author did not state the number of individuals who searched and reviewed the literature; 2) the author searched only one database; 3) the author both searched and included only English-language articles; 4) the author failed to list the excluded articles and rationale for those exclusions; 5) the author did not assess the scientific quality of the included studies; 6) the author mixed together different types of clinical trials and review articles; 7) author did not statistically combine study findings; and 8) author did not statistically assess possible publication bias. In addition, because the author did not provide a description of the search strategy, the review is not reproducible.

Strengths and Weaknesses of the Evidence:

The author reported a very limited description of the included studies. As the included studies were of low methodological quality and there was significant heterogeneity among the studies, the strength of the evidence provided in the current systematic review was considerably limited. Nevertheless, a consistent trend was identified where neither the number of implants nor attachment type had any bearing to the patient's satisfaction or overdenture function. For the mandible, an overdenture with two implants and a bar attachment was associated with fewer complications compared to a similar overdenture with ball attachments.

Implications for Dental Practice:

The descriptive findings for both the maxillary and mandibular overdentures and the significant weakness identified both in the review methods and the finally included articles questions the relative usefulness of this systematic review. As no clear indication regarding the number of implants required to support an overdenture without compromising function or patient satisfaction was identified other factors such as cost, bone support, clinical expertise and experience of the operator, patient's desire will have to be considered to make the final choice.

Critical Summary Publication Date:


These summaries are not intended to, and do not, express, imply, or summarize standards of care, but rather provide a concise reference for dentists to aid in understanding and applying evidence from the referenced systematic review in making clinically sound decisions as guided by their clinical judgment and by patient needs. American Dental Association © 2018