Fracture resistance of maxillary lateral incisors: effects of fiber post dimensions, material, and surface treatment.

Abstract

Fiber-reinforced posts are widely used to restore endodontically treated anterior teeth, yet the relative contributions of post length, diameter, material, and surface treatment to fracture resistance in maxillary lateral incisors remain unclear. To determine the individual and interactive effects of fiber post length, diameter, material, and surface treatment on the fracture resistance and failure modes of endodontically treated maxillary lateral incisors restored with composite cores and monolithic zirconia crowns. In a controlled laboratory study (2 × 2 × 2 × 2 design; 16 groups; n = 10/group; N = 160), extracted maxillary lateral incisors received standardized endodontic treatment, fiber post placement, composite core build-ups, and monolithic 5Y-PSZ zirconia crowns. Factors were: post length (8 vs. 12 mm), diameter (0.9 vs. 1.1 mm), post material/system (tested glass-fiber post system vs. tested quartz-fiber post system), and surface treatment (ethanol-cleaned vs. airborne-particle abrasion + silane). A uniform 2-mm ferrule, PDL simulation, and epoxy embedding were used. Specimens were thermocycled (10,000 cycles, 5-55 °C) and loaded at 135° to the long axis with a 3-mm indenter until failure; maximum load (N) and failure mode (repairable vs. non-repairable) were recorded. Data were analyzed with fixed-effects factorial ANOVA (Tukey post hoc) and χ² tests (α = 0.05). Mean fracture load ranged from 655 ± 62 N to 971 ± 65 N. Main effects were additive: 12-mm length (+ 86.9 N), 1.1-mm diameter (+ 76.7 N), the tested quartz-fiber post system (+ 55.0 N) and abrasion+silane (+ 36.3 N) increased load (all P ≤ .010), with no interactions (all P ≥ .075). Higher-strength configurations showed fewer catastrophic root fractures. Within the tested, anatomy-preserving ranges, longer and slightly 1.1 mm diameter posts, the tested quartz-fiber post system and abrasion-plus-silane conditioning can be combined to improve fracture resistance in restored maxillary lateral incisors, supporting strategies that maximise bonding while preserving dentine. Limitation/future work: As an in vitro static test with thermal ageing only, cyclic fatigue and long-term interface degradation remain uncertain and should be evaluated in fatigue models and clinical trials.