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Войти в исследования Dental materials : official publication of the Academy of Dental Materials · 2026
Optical properties and long-term aging under simulated oral conditions of monolithic four-unit fixed dental prostheses manufactured from gelcast zirconia discs.
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Lüchtenborg Jörg, Sitnikov Nikita, Spies Benedikt C, Hein Sascha, Trunec Martin, Stastny Premysl
Аннотация
OBJECTIVES: To investigate whether microstructural optimization of 3Y-TZP dental zirconia by colloidal gelcasting improves mechanical reliability, aging resistance, and optical properties of monolithic four-unit fixed dental prostheses (FDPs) compared with a conventionally processed reference material.
METHODS: Zirconia discs were fabricated using either colloidal gelcasting or conventional industrial processing and subsequently CAD/CAM-milled into four-unit FDPs (n = 8 per group). After sintering, specimens were subjected to hydrothermal aging with dynamic loading for 5 million cycles. Fracture resistance was assessed by quasi-static loading. Phase transformation was quantified by Raman spectroscopy at loaded and unloaded regions. Wear was evaluated by volumetric analysis of antagonists and FDP surfaces. Optical properties were characterized by spectrophotometric measurements. An RTE-based inverse approach was applied to determine the wavelength-dependent absorption coefficient (µₐ) and reduced scattering coefficient (µs') across the visible spectrum.
RESULTS: All gelcast FDPs (100%) survived combined hydrothermal aging and cyclic loading, whereas one failure occurred in the reference group. After aging, gelcast FDPs exhibited significantly higher fracture loads (1786.3 ± 187.6 N) compared with the conventionally processed control (1468.6 ± 173.0 N). Raman analysis revealed overall low monoclinic phase fractions in both groups. In gelcast zirconia, a statistically significant but low-magnitude spatial variation was detected, with higher monoclinic fractions in unloaded than loaded surface regions. No statistically significant differences in antagonist or FDP volume loss were observed between groups. Optical measurements on separately fabricated discs showed lower reduced scattering coefficients for the gelcast zirconia than for the pressed A2 reference.
SIGNIFICANCE: Colloidal gelcasting improved the optical-mechanical balance of 3Y-TZP in this in vitro study, yielding lower reduced scattering coefficients and higher post-aging fracture loads without evidence of compromised aging behavior.
METHODS: Zirconia discs were fabricated using either colloidal gelcasting or conventional industrial processing and subsequently CAD/CAM-milled into four-unit FDPs (n = 8 per group). After sintering, specimens were subjected to hydrothermal aging with dynamic loading for 5 million cycles. Fracture resistance was assessed by quasi-static loading. Phase transformation was quantified by Raman spectroscopy at loaded and unloaded regions. Wear was evaluated by volumetric analysis of antagonists and FDP surfaces. Optical properties were characterized by spectrophotometric measurements. An RTE-based inverse approach was applied to determine the wavelength-dependent absorption coefficient (µₐ) and reduced scattering coefficient (µs') across the visible spectrum.
RESULTS: All gelcast FDPs (100%) survived combined hydrothermal aging and cyclic loading, whereas one failure occurred in the reference group. After aging, gelcast FDPs exhibited significantly higher fracture loads (1786.3 ± 187.6 N) compared with the conventionally processed control (1468.6 ± 173.0 N). Raman analysis revealed overall low monoclinic phase fractions in both groups. In gelcast zirconia, a statistically significant but low-magnitude spatial variation was detected, with higher monoclinic fractions in unloaded than loaded surface regions. No statistically significant differences in antagonist or FDP volume loss were observed between groups. Optical measurements on separately fabricated discs showed lower reduced scattering coefficients for the gelcast zirconia than for the pressed A2 reference.
SIGNIFICANCE: Colloidal gelcasting improved the optical-mechanical balance of 3Y-TZP in this in vitro study, yielding lower reduced scattering coefficients and higher post-aging fracture loads without evidence of compromised aging behavior.