Ferrule dimensions and restoration outcomes in endodontically treated teeth: A systematic review and meta-analysis.

PURPOSE: To systematically review and meta-analyze clinical, in vitro, and finite-element studies assessing how ferrule height, width, and circumferential extent influence fracture resistance and survival of endodontically treated teeth.

METHODS

This review followed PRISMA 2020 guidelines. Two reviewers conducted the screening, with a third resolving disagreements. Eligible designs included clinical studies, in vitro experiments, and finite-element analyses evaluating ferrule characteristics. Risk of bias was assessed using RoB 2, the Newcastle-Ottawa Scale, and CRIS/CONSORT-adapted criteria. Random-effects models were applied.

RESULTS

Thirty-three primary studies (6 clinical, 18 in vitro, 9 finite-element) were included. Ferrule height ≥ 2 mm significantly improved fracture resistance (MD +165 N; 95% CI: 110-215). Ferrule presence increased clinical survival (RR 1.34; 95% CI: 1.12-1.59). Dentin thickness ≥ 1 mm and complete 360° ferrules provided the most favorable reinforcement, while partial ferrules with ≥ 2 opposing walls remained beneficial.

CONCLUSIONS

A ferrule height of 1.5-2.0 mm and dentin thickness ≥ 1 mm are associated with improved biomechanical and clinical outcomes. These findings should be interpreted within the context of variation in study designs and reporting quality. No restorative strategy matched the biomechanical reinforcement provided by a natural dentin ferrule.