Cost Effectiveness of Two Short Implants Versus One Short Implant With a Cantilever in the Posterior Region: 7.5-Year Follow-Up of a Randomised Controlled Trial

Aim: To compare long-term clinical and radiographic outcomes of a single short implant (6 mm) supporting a cantilevered restoration versus two adjacent short implants with non-splinted single crowns over a 7.5-year follow-up and determine which approach is more cost effective. Materials and methods: A total of 36 patients with at least a two-tooth gap in the posterior region were randomised to receive either one short implant with a cantilever prosthesis (ONE-C) or two short implants with individual crowns (TWO). Fixed restorations were placed 3-6 months post implantation, and patients were evaluated at baseline and at 6 months and 1, 3, 5 and 7.5 years. Kaplan-Meier curves, mixed-effects models and cost-effectiveness models were used to compare the groups. Results: Twenty-five patients (15 in ONE-C, 10 in TWO) completed the 7.5-year follow-up. Implant survival was 83.3% in group ONE-C and 86.6% in group TWO, with no significant differences between the groups (p = 0.772). No statistically significant differences were found between groups for marginal bone levels (mean difference -0.16 [95% CI: -0.7 to 0.3] p = 0.57), probing depth (mean difference -0.13 [95% CI: -0.5 to 0.3] p = 0.58), bleeding on probing (mean difference 0.0 [95% CI: -0.0; 0.2] p = 0.31) or plaque levels (mean difference -0.0 [95% CI: -0.1 to 0.1] p = 0.93). Technical complications were more frequent in the ONE-C group (64%) than in the TWO group (36%). Conclusion: Both treatment approaches showed comparable clinical and radiographic outcomes. Short implants supporting cantilever restorations were generally more cost effective than two short implants but exhibited higher early complication and failure rates, likely related to mechanical overload. Trial registration: ClinicalTrials.gov Identifier: NCT01649531.