Three-body wear effect on different CAD/CAM ceramics staining durability

Ceramic restorations often require extrinsic staining to enhance aesthetics, but the durability of these stains under mechanical stress remains unclear. Prior research has shown that ceramics vary in wear resistance, but no prior work had resolved how staining techniques affect long-term stain retention. This gap motivated a detailed comparison of staining durability across different CAD/CAM ceramics. While some materials are known to resist wear better, the specific impact of staining methods on wear resistance had not been fully explored. The study addressed this uncertainty by evaluating how different ceramics and staining protocols influence stain retention during simulated mastication. No prior work had resolved the effect of crystallization timing on stain durability for zirconia-reinforced lithium silicate. The need for a standardized approach to stain application and wear simulation in dental ceramics remains unmet. This study aimed to clarify the mechanical behavior of stained ceramic surfaces under repeated loading.

The study aimed to compare the durability of extrinsic staining on four types of CAD/CAM ceramics. The specific problem addressed was the variability in stain retention across different materials and staining techniques. The motivation stemmed from clinical needs for long-lasting aesthetic restorations. The researchers sought to determine which ceramics and staining protocols best preserve stain integrity under simulated chewing conditions. A key question was whether crystallization timing affected stain durability for zirconia-reinforced lithium silicate. The study also aimed to identify differences in wear resistance between polymerized and fired stains. No prior work had resolved the comparative performance of feldspathic and hybrid ceramics in this context. The goal was to provide data to guide material selection and staining protocols in clinical practice.

The study used four types of monolithic ceramics: high translucent zirconia, zirconia-reinforced lithium silicate, hybrid ceramic, and feldspathic ceramic. Specimens were divided into groups based on staining techniques and crystallization timing. Staining was applied either before or after crystallization for certain materials. A three-body wear test simulated mastication using a food bolus and antagonist in a controlled environment. The wear rate was measured at five intervals using a profilometer. Scanning Electron Microscopy (SEM) was used to analyze surface morphology before and after wear. Two-way ANOVA and post-hoc Tukey tests evaluated statistical significance. The experimental setup allowed for a direct comparison of stain durability across materials and staining methods.

Wear rates were significantly influenced by ceramic type and number of cycles (P < 0.001). Hybrid ceramic lost all staining after 200,000 cycles, while high translucent zirconia and zirconia-reinforced lithium silicate (stained before crystallization) lost staining after 600,000 cycles. Feldspathic ceramic retained staining even after 1,000,000 cycles. Zirconia-reinforced lithium silicate (stained after crystallization) showed improved durability compared to the pre-crystallization group. Feldspar ceramic exhibited significantly higher staining durability than zirconia-reinforced lithium silicate (post-crystallization). SEM images revealed distinct surface morphologies before and after wear testing. Polymerized stains showed lower durability than fired stains across all materials. The results suggest that both ceramic composition and staining protocol play critical roles in stain retention.

The authors concluded that ceramic type and staining protocol significantly affect stain durability under simulated mastication. Feldspathic ceramic demonstrated the highest staining durability, followed by zirconia-reinforced lithium silicate and high translucent zirconia. Staining after crystallization improved durability for zirconia-reinforced lithium silicate. The study found that fired stains outperformed polymerized stains in all tested materials. SEM analysis confirmed that surface morphology changes with wear and staining. No prior work had resolved the comparative performance of these ceramics in this context. The findings suggest that material selection and staining technique should be considered together to optimize stain retention. The results support the use of feldspathic ceramic for long-term stain durability in clinical applications.