Four vs. Six Implant Full-Arch Restorations-A Direct Comparative Retrospective Analysis in a Large Controlled...

Area of Science:

• Oral and Maxillofacial Surgery
• Dental Implantology
• Prosthodontics

Background:

• The optimal number of implants (four vs. six) for implant-supported fixed complete dentures (IFCDs) remains debated regarding implant survival.
• This study addresses the inconclusive evidence by comparing implant survival rates between four and six implants in a large patient cohort.

Purpose of the Study:

• To compare the implant survival of immediately loaded IFCDs supported by four versus six implants.
• To evaluate the influence of treatment planning, patient factors, and anatomical considerations on implant survival.

Main Methods:

• Retrospective analysis of 943 patients and 5989 implants with a mean follow-up of 5.0 years.
• Utilized a systematic clinical decision support system (CDSS) based on alveolar atrophy classification (CC).
• Employed Kaplan-Meier analysis, log-rank tests, and multilevel Cox proportional hazard models to assess implant survival.

Main Results:

• Comparable 2- and 5-year cumulative survival rates (CSRs) for four vs. six IFCDs (2-year: 98.6% vs. 98.4%; 5-year: 98.8% vs. 98.7%).
• Implant loss was correlated with jaw type and age, but not significantly with alveolar atrophy (CC) within the CDSS.
• Differences between implant numbers were more pronounced at maxillary and mandibular levels but remained statistically non-significant.

Conclusions:

• Four and six IFCDs exhibit high and comparable mid-to-long-term implant survival rates when managed with a systematic, patient-centered CDSS.
• The number of implants (four vs. six) did not significantly impact implant survival in this cohort.
• Further research is needed to evaluate prosthetic and technical complications, which were outside the scope of this study.