Can narrow-diameter implants enhance patient-reported outcomes for mandibular implant-retained overdentures?

A systematic review and meta-analysis.

To evaluate and compare stability and functionality between narrow and standard implant-retained mandibular overdentures in edentulous patients from multiple perspectives. Assessments included clinical parameters [survival rate (SR) and marginal bone loss (MBL)], along with patient-reported outcome measures (PROMs) including patient satisfaction and oral health-related quality of life (OHRQoL).

The study protocol followed PRISMA criteria for reporting reviews and meta-analyses. Using appropriate keywords, electronic search was conducted in each of the following databases: Medline, Embase, Cochrane Central Register of Controlled Trials, Web of Science, and Scopus, up to July 22, 2022. There were no restrictions based on language, publication type, or publication date. Additionally, ongoing studies were explored in ClinicalTrials.gov and WHO ICTRP, while cross-references in each selected study were manually examined. The eligible studies were randomized controlled trials (RCTs) or controlled clinical trials (CCTs) comparing narrow implants (diameter ≤ 3.5 mm) to standard implants (diameter > 3.5-4.5 mm) retaining mandibular overdentures in edentulous patients. Excluded were studies with unclear implant diameter information, fewer than 5 patients per group, observational studies, reviews, and laboratory studies. Two authors independently conducted study selection, data collection, and analysis, resolving any discrepancies through discussion with a third author. Methodological quality was assessed using RoB-2 and ROBINS-I tools. Implant SR and MBL measurements at final follow-up were recorded, while patient satisfaction and OHRQoL were evaluated using visual analogue scale (VAS-100) and oral health impact profile (OHIP) questionnaire, respectively.

After duplicate removal, 782 publications and 83 registered clinical trials were identified, of which 26 were eligible for full-text assessment. Ultimately, the quantitative evaluation included 12 publications from 8 independent studies: 4 parallel design RCTs and 4 CCTs. Risk of bias assessment revealed variations among the studies, with only one study being rated as having low risk. The follow-up periods ranged from 1 to 3 years. Meta-analysis showed no significant difference in SR and MBL between narrow and standard implant groups (p = 0.29 and p = 0.93, respectively), with considerable heterogeneity (I² = 100% and I² = 78%, respectively). Regarding PROMs, the narrow implant group showed significantly higher levels of patient satisfaction (mean difference (MD): 8.18; 95% CI: 5.83 to 10.53; p < 0.00001; I² = 36%) and exhibited a significant improvement in OHRQoL (MD: -4.36; 95% CI: -6.83 to -1.89; p < 0.001; I² = 55%) compared to the standard implant group.

For implant-retained mandibular overdentures, the use of narrow implants is associated with comparable SR and MBL, along with higher patient satisfaction and better OHRQoL improvement as compared to standard implants, offering a viable alternative option for patients with diminished alveolar bone width.