Remaining Tooth Structure and Prognosis of Restored Endodontically Treated Teeth: A Systematic Review

The prognosis of endodontically treated teeth is closely tied to the amount and configuration of remaining coronal tooth structure. This systematic review compared the survival of permanent endodontically treated teeth without fracture (fracture-free survival) restored with non-cuspal-coverage direct resin composites versus full/partial-coverage crowns, with a focus on ferrule presence/continuity, axial wall integrity, and the extent of surface loss as modifying factors. Following PRISMA guidance, the review included randomized trials, prospective and retrospective cohorts, and clinical studies from five databases with manual citation tracking; studies involving mature permanent teeth and reporting survival were eligible. Five studies fulfilled the inclusion criteria; the number of teeth considered by the studies ranged from 105 to 420 teeth. Short-term outcomes were uniformly high, with several studies reporting 100% survival at ≤36 months for both crowns and direct composites. In cohorts that used longer follow-up periods of approximately 8-10 years, survival rates were generally higher for crowned teeth, especially when structural loss was extensive. Where reported, stratification by remaining tooth structure (RTS) suggested that teeth with one to three surfaces lost and preserved axial walls performed well with adhesively bonded direct composites, whereas teeth with four to five surfaces lost or disrupted ferrule benefited from cuspal coverage. Risk-of-bias assessment was generally low to moderate, though some studies showed concerns related to deviations from intended interventions or outcome measurement. Overall, crowns and direct composites both achieved high survival rates in the short term; however, the overall evidence indicates a long-term advantage for cuspal coverage in structurally compromised teeth. Evidence certainty is limited by heterogeneity, small numbers, and incomplete reporting of remaining tooth-structure variables, underscoring the need for standardized RTS reporting and longer, well-controlled studies.