J Mech Behav Biomed Mater. 2026 Jul 18;182:107557. doi: 10.1016/j.jmbbm.2026.107557. Online ahead of print.
ABSTRACT
OBJECTIVES: To evaluate the fracture load (FL) of 3- and 4-unit zirconia fixed dental prostheses (FDP)s fabricated from two strength- and translucency-gradient multilayer zirconia materials before and after thermomechanical aging, and to compare the findings with finite element modeling (FEM).
METHODS: A total of 80 FDPs were milled from two zirconia materials: 5Y-PSZ/3Y-TZP (IPS e.max ZirCAD Prime) and 5Y-PSZ/4Y-PSZ (IPS e.max ZirCAD Prime Esthetic) (n = 40/material). Connector cross-sections were adapted to the material and FDP design: 17.0 and 14.1 mm2 (3-unit) and 30.3, 33.1, and 39.2 mm2 (4-unit) for 5Y-PSZ/3Y-TZP FDPs; 26.5 and 31.4 mm2 (3-unit) and 27.5, 38, and 44.6 mm2 (4-unit) for 5Y-PSZ/4Y-PSZ. All FDPs were cemented onto CoCrMo abutments. Half of the specimens were tested on fracture load (FL) under initial conditions, whereas the other half underwent thermomechanical aging in a chewing simulator (2.4 million cycles, 50 N, 1.5 Hz, 12,000 thermal cycles between 5°C and 55°C; 60 s dwell time). Data were analyzed using the Kolmogorov-Smirnov test, univariate analysis with partial eta squared, Mann-Whitney-U-test, Weibull statistics, and the Ciby Geigy method (α = 0.05). In addition, FEM simulations were performed to predict FL and failure location.
RESULTS: For 3-unit FDPs, no difference in initial FL was found between the two materials. After thermomechanical aging, 5Y-PSZ/4Y-PSZ showed higher FL than 5Y-PSZ/3Y-TZP. For 4-unit FDPs, FL was not affected by zirconia material or aging condition. In general, FDP span and thermomechanical aging had no influence on FL. The lowest Weibull modulus was observed for aged 4-unit 5Y-PSZ/4Y-PSZ FDPs, whereas the highest was found for initial 3-unit 5Y- PSZ/3Y-TZP FDPs. All 3-unit FDPs fractured at the connector between abutment and pontic, whereas 4-unit FDPs predominantly fractured in the pontic region between teeth 35 and 36. The FEM-predicted fracture loads were 3080 N and 2181 N for the 3-unit and 4-unit 5Y-PSZ/4Y-PSZ, and 2560 N and 2600 N for the corresponding 5Y-PSZ/3Y-TZP FDPs.
SIGNIFICANCE: Both strength and translucency gradient multilayer zirconia materials exhibited clinically sufficient and largely comparable FL behavior when connector geometry were appropriately designed. Thermomechanical aging did not impair load-bearing capacity under the tested conditions. FEM predictions showed good agreement with the results in terms of both FL magnitude and failure location.
PMID:42472511 | DOI:10.1016/j.jmbbm.2026.107557
