Effects of nano MgO addition on the mechanical, wear, and low-temperature degradation properties of 3Y-TZP composite ceramics

Degradation kinetics of high-translucency dental zirconias: Mechanical properties and in-depth analysis of phase transformation

BackgroundsThis study aims to evaluate the effects of low-temperature degradation (LTD) aging and pH variations on the mechanical and surface properties of 4Y-TZP and 6Y-TZP high-translucent zirconia materials subjected to different surface treatments.MethodsA total of 336 Y-TZP specimens (1.2 mm thickness, 12 mm diameter) were prepared and divided into two zirconia groups (4Y-TZP, 6Y-TZP) and four different surface treatment subgroups (glazed, grinding, grinding + polishing, grinding + glazing) (n = 42 per subgroup). Control specimens were stored in distilled water for 28 days (n = 14 per subgroup), while the remaining samples underwent LTD aging in an autoclave for 30 h. After aging, the specimens were immersed in pH 3 (acidic) and pH 9 (basic) solutions for 14 days. The mechanical and surface properties were assessed using biaxial flexural strength testing, Weibull analysis, X-ray diffraction phase analysis, scanning electron microscopy, and digital profilometry for surface roughness measurements.ResultsThe findings demonstrated that LTD aging combined with pH 3 exposure significantly affected the mechanical properties and phase transformation of Y-TZP zirconia (p < 0.05). Among the different surface treatments, grinding followed by polishing resulted in the highest biaxial flexural strength and lowest surface roughness, whereas grinding alone led to a significant decrease in mechanical performance. Grinding followed by glazing provided partial protection against surface degradation; however, the combination of LTD aging and pH exposure resulted in an overall reduction in mechanical strength across all groups. The 6Y-TZP group, due to its higher cubic phase content, exhibited greater resistance to LTD but showed lower biaxial flexural strength compared to 4Y-TZP. Additionally, pH 3 conditions induced more severe surface degradation and mechanical weakening, whereas pH 9 conditions resulted in more controlled degradation.ConclusionSurface treatments, LTD aging, and pH variations play a critical role in determining the mechanical stability and surface characteristics of Y-TZP zirconia. Grinding followed by polishing is recommended for enhancing restoration durability in clinical applications. Acidic environments (pH 3) can negatively impact mechanical properties, while basic conditions (pH 9) provide comparatively better stability. The optimization of surface treatments and protective clinical strategies is essential to mitigating the adverse effects of LTD and ensuring the long-term success of zirconia restorations.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12903-025-07473-2.

Mechanical properties, translucency, and low temperature degradation (LTD) of yttria (3–6 mol%) stabilized zirconia

Influence of crystalline phase transformation induced by airborne-particle abrasion and low-temperature degradation on mechanical properties of dental zirconia ceramics stabilized with over 5 mol% yttria

Development and characterization of Al2O3/SrAl12O19 reinforced zirconia with high fracture toughness and low-temperature degradation-resistant for dental applications

To improve the bioactivity of alumina containing yttria stabilized zirconia (Al-YSZ), composite ceramics consisting of Al-YSZ and 0–10 wt % of hydroxyapatite (HA) were prepared. The XRD patterns of sintered disks with an HA content above 3 wt % had monoclinic and cubic YSZ phases and a β-tricalcium phosphate phase. Although the Vickers hardness decreased as the HA content increased, all the prepared ceramics had the same or greater hardness (1000–1300 Hv with a load of 0.49 N) compared to typical YSZ ceramics (900–1000 Hv) commonly used in clinics. Furthermore, the bonelike apatite formation ability in simulated body fluid, which was examined as a screening of bioactivity, suggested that all the surfaces of Al-YSZ ceramics blending with a small amount of HA may possess the ability to connect bone. After the accelerated low temperature degradation (LTD) test performed in normal saline at 120°C for five days using composite ceramics with the HA content of 0, 1, 3, and 10 wt %, the tetragonal zirconia phase of all composite ceramics were partially transformed into the monoclinic phase with a transition ratio of ca. 16–18 mol % (for HA = 0 and 10 wt %) and ca. 4–5 mol % (for HA = 1 and 3 wt %). Blending microsized HA powder in Al-YSZ ceramics has both positive and negative effects on the LTD durability of Al-YSZ ceramics. An advantage is that calcium ion substitution in YSZ seems to stabilize the tetragonal (or cubic) zirconia phases, but the increased surface area exposed to the solution is a disadvantage.

Tribological and mechanical properties improvement of G20CrNiMo alloy via fabricating gradient composite layer through ultrasonic strengthening grinding process

This study aimed to assess the effect of low-temperature degradation (LTD) and surface treatment on the flexural strength of additive-manufactured (AM) zirconia by comparison to subtractive-manufactured (SM) zirconia. Disc-shaped zirconia specimens were fabricated using AM and SM technology, and each group was assigned to 3 subgroups according to the type of surface treatment: control, sandblasting (SB), and 9% hydrofluoric acid etching (HF). The groups were then further divided into 2 subgroups: unaged and aged. Biaxial flexural strength, crystal phase, surface topography, and surface roughness were measured to evaluate the mechanical properties. Statistical analyses were performed with 3-way ANOVA, followed by the comparison of means with Bonferroni post hoc analyses. The means and standard deviations of the biaxial flexural strength and Weibull parameters were calculated with descriptive statistics. All SM groups showed significantly greater flexural strength than the AM groups (p < .05), and LTD did not affect flexural strength except for the SMHF group (p < .05). After LTD, monoclinic phases (m-phase) were found in all groups, and SEM images showed grain pullout due to zirconia volume expansion in both control groups. Sandblasting significantly affected flexural strength (p < .05), whereas the HF group did not affect flexural strength except in the SMHF group after LTD (p < .05). No significant difference was observed in the surface roughness of AM compared to SM groups conditioned with the same surface treatment regardless of LTD. AM zirconia has comparable mechanical properties to SM zirconia, regardless of low-temperature degradation and surface treatment, which indicates the potential of the AM technique for clinical applications.

Basalt fiber is an eco-friendly reinforcement fiber in fabricating polymer composites with high specific mechanical physicochemical, biodegradable, and wear resistant properties. This article firstly introduces the composition, morphology, functional group, and thermostability of basalt fibers. Subsequently, friction composites based on a newly designed formulation were fabricated with different content basalt fibers. According to the Chinese National Standard, the physical and mechanical properties and tribological performance of the friction composites were characterized and evaluated. Extension evaluation based on extenics theory was developed to evaluate the relationships between the coefficient of friction and content of basalt fiber. Furthermore, the possible mechanism of basalt fiber reinforced friction composites was proposed.

Tetragonal polycrystalline zirconia stabilized with 3% mol of yttria (3Y-TZP) is a popular bioceramic, increasingly used for dental applications thanks to its good mechanical properties, biocompatibility and aesthetic outcome. The addition of stabilizers oxides retains the metastable tetragonal structure, which can transform to the stable monoclinic form upon mechanical or chemical solicitation with its associated volume increment. If the phase transformation is induced by high stresses at the tip of an advancing crack, transformation toughening mechanisms are activated hindering further propagation of the crack and making this material more tough and damage tolerant. On the other hand, when 3Y-TZP is exposed to humid environment at moderate temperatures water species diffuse inside the tetragonal lattice triggering progressive phase transformation and the consequent degradation of the surface. This is known as low temperature degradation (LTD), hydrothermal degradation or aging and is one of the main drawbacks of this family of materials, especially for biomedical applications. There has been a growing interest in modifying the surface topography in order to influence the biological response to these biomaterials. Among the available methods, laser patterning is one of the most promising because it is a non-contact and therefore not-contaminating technique and it allows great precision. In particular, Direct Laser Interference Patterning (DLIP) allows patterning at the micrometric- and nanometric-scale in a single-step process. Laser beams interference creates a periodical distribution of intensity that produces the desired pattern on the surface. It has been successfully applied on metals, polymers and ceramics for different applications spanning from antimicrobial coatings to tribological applications. Its application to 3Y-TZP seems therefore promising but needs a thorough characterization in order to ensure the short and long term stability. This work contributes to understand how nanosecond laser interference patterning modifies the topography and microstructure of 3Y-TZP and how these changes influence the integrity and reliability of the material after the laser treatment. DLIP in the nanosecond regime is a suitable technique to introduce periodical topography at the micrometric scale on the surface of 3Y-TZP. Laser-material interaction mainly results in thermal effects, producing the desired topography alteration thanks to material melting and liquid flow. Pattern geometry and overall surface roughness can be modified independently varying laser fluence and number of pulses. The surface treatment is not free of collateral damage due to thermal shock. Microcracking, recrystallization, residual stresses, phase transformation and texturization are produced on the treated surface. These microstructural modifications are concentrated in a thin layer of material (1 µm thick) and are not a concern for mechanical integrity of the treated material. However, pre-existing defects on the surface can interact with the laser beam, becoming larger critical defects that lower the overall mechanical resistance. Therefore, a good surface finish, ideally free of defects, would ensure an optimal outcome of the surface treatment. Finally, the LTD resistance is reduced by the laser treatment because of the monoclinic phase and residual stresses induced by thermal shock. An annealing treatment is capable of restoring the LTD resistance, even more than before the laser treatment thanks to the texture induced in the tetragonal phase. Therefore, to ensure the good outcome of such laser patterning on 3Y-TZP a thermal treatment (at 1200°C for 1 hour) is recommended to ensure the long term reliability and a defect-free surface is recommendrecommended to ensure the long term reliability and a defect-free surface is advisable to reduce the detrimental effect of laser on mechanical properties.

Improvement of the mechanical, tribological and antibacterial properties of glass ionomer cements by fluorinated graphene

Evaluation of mechanical reliability of zirconia-toughened alumina composites for dental implants

The effects of polytetrafluoroethylene (PTFE), graphite, ultrahigh molecular weight polyethylene (UHMWPE), and their compounds on mechanical and tribological properties of glass-fiber-reinforced polyamide 6 (PA6/GF) were studied. The polymeric materials were blended using twin-screw extruder and subsequently injection molded for test samples. Mechanical properties were investigated in terms of hardness, tensile strength, and impact strength. Friction and wear experiments were run under ambient conditions at a rotating speed of 200 rpm and load of 100 N. The morphologies of the worn surfaces were also observed with scanning electron microscope. The results showed that graphite could increase the tensile strength of PA6/GF-15 composite, but the material became soft. Graphite/UHMWPE complex solid lubricants were effective in increasing the already high impact strength of PA6/GF-15 composite. 5% PTFE gave the maximum reduction in the coefficient of friction. However, PTFE/UHMWPE complex solid lubricants were the best choice for improving both friction and wear behaviors due to the lower friction coefficient and mass wear rate. Moreover, the worn surface of PA6 composites revealed that adhesive wear, abrasive wear, and fatigue wear occurred in this study.

Effect of low-temperature degradation treatment on hardness, color, and translucency of single layers of multilayered zirconia

In this work, we prepared nitrile butadiene rubber (NBR) composites with fluorographene (FG) and carbon nanotubes (CNTs) as hybrid fillers by a solution‐blending method. The resulting composites xFG/yCNTs‐NBR, where x and y represent the loading of FG and CNTs respectively, show significantly improved physical and mechanical properties. The hybrid fillers can form a filler network in the rubber matrix, leading to efficient energy dissipation. As a result, when the mass ratio of FG to CNTs is 1:1 and the total filler loading is 20 phr, the tensile strength of 10FG/10CNTs‐NBR is as high as 12.1 MPa. Furthermore, due to inherent lubricating and oil‐repelling effects of FG, 10FG/10CNTs‐NBR shows an abrasion resistance index (ARI) of 187% and a volume change of 2.38% after 72 h of soaking in aviation oil, which are 24% higher and 48% lower than the corresponding values of unfilled NBR composites, respectively. These results indicate that the hybrid fillers can effectively enhance the mechanical, wear and oil resistant properties of the elastomer composites, which is conductive for application of the NBR‐based composites.