Patient-reported outcomes (PROs) describe health outcomes deriving directly from the patient’s perspective without interpretation by another person. Patient-reported outcome measures (PROMs) represent the tools to quantify and measure PROs. Dental patient-reported outcomes (dPROs) represent PROs applied to the dental field. The systematic review by Abou-Ayash and co-authors aimed to determine treatment effects of complete implant-supported fixed dental prostheses (CIFDPs) versus implant-supported or implant-retained overdentures (IODs) on dental patient-reported outcomes (dPROs). In contrast to many other items of research, the present review aimed to compare the variation in dPROs between pre- and post-treatment values.

In a previous review, reporting of dPROs in edentulous individuals comparing CIFDPs versus IODs was found to be inconsistent and insufficient (Yao et al. 2018). Although lately more trials in implant dentistry include the patient’s view with the dPROMs, there are still many studies which lack this information, especially in the field of fixed dental implant prostheses. In order to ensure comparability between different scales and non-standardized dPROs and PROMs, Abou-Ayash and co-workers calculated the effect sizes (ES) between studies, which had been previously considered an appropriate tool for comparing dPROs (Reissman et al. 2021). The ES is a quantitative measure of the treatment effect, and the larger the effect size, the stronger the treatment effect.

In completely edentulous patients rehabilitated with conventional dentures (CD), the use of implants to retain or support a dental prosthesis (in either the maxilla or the mandible) leads to an improvement in overall dPROs. When completely edentulous patients wearing a CD are rehabilitated with implants, there is a comparable improvement in dPROs regardless of whether the patients are restored with a CIFDP or an IOD.

When the edentulous mandible is restored with an IOD, there is no difference in dPROs between bar-retained and non-splinted attachments. Bars showed a moderately higher ES than single attachments, however this difference was not statistically significant. These results suggest that there is no difference in dPROs – in terms of attachments – between bar- or single attachment-retained/supported IODs.

With respect to dPROs, mandibular IODs retained by two implants are superior in comparison with IODs retained by a single implant. On the other hand, increasing the number of implants to more than two did not improve dPROs when considering mandibular IODs.

According to the clinical recommendations within the consensus report, both CIFDP and IODs can be recommended for completely edentulous patients in terms of comfort and stability. For utmost levels of comfort, stability and retention, the CIFDP solution may be preferred to IODs if clinically indicated. Other factors to keep in mind while deciding between CIFDPs and IODs include speech, manual dexterity, maintenance requirements, esthetic concerns, space requirements, costs, stability and retention. During treatment planning phases, the patient’s ability to perform adequate plaque control should be taken into consideration and this skill should be re-assessed on a regular basis.

From a patient’s perspective both splinted and single attachments (Fig. 1) may be considered equally effective and can be recommended. Based on dPROs, a mandibular IOD retained by one or two implants (Fig. 2) provides an improvement over a CD, and two implants result in increased comfort compared to a single implant.

Increasing the number of implants to more than two did not improve dPROs when considering mandibular IODs. The number of recommended mandibular implants also depends on the antagonist arch: if the maxilla is dentate or restored with a CIFDP, more than two standard diameter implants in strategic positions are recommended to support the mandibular IOD. This limits the incidence of complications such as fracture of implant and prosthetic components. In certain clinical scenarios, such as compromised anatomic situations or mucosal conditions, more than two implants are also recommended to enable implant support and reduce mucosal support.

Recommendations for future research call attention to critical issues that are not addressed in the current literature. For instance, a clear distinction in terminology should be made between dPROs and dPROMs to ensure that correct terminology is being used and to minimize confusion. Furthermore, more studies directly comparing the treatment effect of CIFDPs versus IODs on dPROs are warranted. When reporting on dPROs, baseline as well as follow-up data should be mandatory to enable meaningful comparisons and data interpretation. Standardized dPROs should be preferred in the future to ensure high methodological quality and comparability, such as the use of the Oral Health Impact Profile (OHIP). For the assessment of specific treatment outcomes, customized questions can be added to pre-existing questionnaires. It is very important that dPROs and dPROMs be comparable across different studies. Indeed, this was one of the main difficulties encountered when trying to compare existing data and for this reason, questions should be proposed that were already used in previous studies on the same topic. The answers to such questions should be collected on commonly used and accepted scales such as visual analog scales (VAS), ordinal response scales or Likert scales.