In vitro and in vivo investigation of Argiope bruennichi spider silk-based novel biomaterial for medical use.

As a natural and biocompatible material with high strength and flexibility, spider silk is frequently used in biomedical studies. In this study, the availability of Argiope bruennichi spider silk as a surgical suture material was investigated. The effects of spider silk-based and commercial sutures, with and without Aloe vera coating, on wound healing were evaluated by a rat dorsal skin flap model, postoperatively (7th and 14th days). Biochemical, hematological, histological, immunohistochemical, small angle x-ray scattering (SAXS) analyses and mechanical tests were performed. A. bruennichi silk did not show any cytotoxic effect on the L929 cell line according to MTT and LDH assays, in vitro. The silk materials did not cause any allergic reaction, infection, or systemic effect in rats according to hematological and biochemical analyses. A. bruennichi spider silk group showed a similar healing response to commercial sutures. SAXS analysis showed that the 14th-day applications of A. bruennichi spider silk and A. vera coated commercial suture groups have comparable structural results with control group. In conclusion, A. bruennichi spider silk is biocompatible in line with the parameters examined and shows a healing response similar to the commercial sutures commonly used in the skin.

Irradiation Behavior of Analgesic and Nonsteroidal Anti-Inflammatory Drug-Loaded UHMWPE for Joint Replacement.

Local delivery of pain medication can be a beneficial strategy to address pain management after joint replacement, as it can decrease systemic opioid usage, leading to less side and long-term effects. In this study, we used ultrahigh molecular weight polyethylene (UHMWPE), commonly employed as a bearing material for joint implants, to deliver a wide set of analgesics and the nonsteroidal anti-inflammatory drug tolfenamic acid. We blended the drugs with UHMWPE and processed the blend by compression molding and sterilization by low-dose gamma irradiation. We studied the chemical stability of the eluted drugs, drug elution, tensile properties, and wear resistance of the polymer blends before and after sterilization. The incorporation of bupivacaine hydrochloride and tolfenamic acid in UHMWPE resulted in either single- or dual-drug loaded materials that can be sterilized by gamma irradiation. These compositions were found to be promising for the development of clinically relevant drug-eluting implants for joint replacement.

Self-Assembly Reinforced Alginate Fibers for Enhanced Strength, Toughness, and Bone Regeneration.

Material reinforcement commonly exists in a contradiction between strength and toughness enhancement. Herein, a reinforced strategy through self-assembly is proposed for alginate fibers. Sodium alginate (SA) microstructures with regulated secondary structures are assembled in acidic and ethanol as reinforcing units for alginate fibers. Acidity increases the flexibility of the helix and contributes to enhanced extendibility. Ethanol is responsible for formation of a stiff ß-sheet, which enhances the modulus and strength. The structurally engineered SA assembly exhibits robust mechanical compatibility, and thus reinforced alginate fibers possess an improved tensile strength of 2.1 times, a prolonged elongation of 1.5 times, and an enhanced toughness of 3.0 times compared with SA fibers without reinforcement. The reinforcement through self-assembly provides an understanding of strengthening and toughening mechanism based on secondary structures. Due to a similar modulus with bones, reinforced alginate fibers exhibit good efficacy in accelerating bone regeneration in vivo.

Mechanical characterization of soft biomaterials: which time and spatial scale to choose?

The mechanical properties of soft gels hold significant relevance in biomedicine and biomaterial design, including the development of tissue engineering constructs and bioequivalents. It is important to adequately characterize the gel's mechanical properties since they play a role both in the overall structural properties of the construct and the physiological responses of cells. The question remains which approach for the mechanical characterization is most suitable for specific biomaterials. Our investigation is centered on the comparison of three types of gels and four distinct mechanical testing techniques: shear rheology, compression, microindentation, and nanoindentation by atomic force microscopy. While analyzing an elastic homogeneous synthetic hydrogel (a polyacrylamide gel), we observed close mechanical results across the different testing techniques. However, our findings revealed more distinct outcomes when assessing a highly viscoelastic gel (Ecoflex) and a heterogeneous biopolymer hydrogel (enzymatically crosslinked gelatin). To ensure precise data interpretation, we introduced correction factors to account for the boundary conditions inherent in many of the testing methods. The results of this study underscore the critical significance of considering both the temporal and spatial scales in mechanical measurements of biomaterials. Furthermore, they encourage the employment of a combination of diverse testing techniques, particularly in the characterization of heterogeneous viscoelastic materials such as biological samples. The obtained results will contribute to the refinement of mechanical testing protocols and advance the development of soft gels for tissue engineering.

Biocompatible, porous hydrogels composed of aliphatic polyesters and poly(2-isopropenyl-2-oxazoline). Their application as scaffolds for bone tissue regeneration.

In this study, porous networks were efficiently prepared by crosslinking hydrophilic poly(2-isopropenyl-2-oxazoline) (PiPOx) with dicarboxylic polyesters (HOOC-PLA-COOH or HOOC-PCL-COOH) in the presence of sodium chloride as a water-soluble porogen. Importantly, by using a relatively simple synthetic protocol, the resulting spongy materials were freely formed to the desired size and shape while maintaining stable dimensions. According to the SEM data, the porous 3D structure can be altered by the pore dimensions, which are dependent on the porogen crystal size. After porosity characterization, the mechanical properties were also evaluated via uniaxial compression and tensile tests. The porous networks formed hydrogels with a high water absorption capacity. Finally, after showing cytocompatibility by the MTT assay, we also demonstrated the applicability of the porous hydrogels as scaffolds for cell cultivation. The presented results suggest that this type of hydrogels is a promising material for tissue engineering.

An evaluation of the usability and durability of 3D printed versus standard suture materials.

The capability to produce suture material using three-dimensional (3D) printing technology may have applications in remote health facilities where rapid restocking of supplies is not an option. This is a feasibility study evaluating the usability of 3D-printed sutures in the repair of a laceration wound when compared with standard suture material. The 3D-printed suture material was manufactured using a fused deposition modelling 3D printer and nylon 3D printing filament. Study participants were tasked with performing laceration repairs on the pigs' feet, first with 3-0 WeGo nylon suture material, followed by the 3D-printed nylon suture material. Twenty-six participants were enrolled in the study. Survey data demonstrated statistical significance with how well the 3D suture material performed with knot tying, 8.9 versus 7.5 (p = 0.0018). Statistical significance was observed in the 3D-printed suture's ultimate tensile strength when compared to the 3-0 Novafil suture (274.8 vs. 199.8 MPa, p = 0.0096). The 3D-printed suture also demonstrated statistical significance in ultimate extension when compared to commercial 3-0 WeGo nylon suture (49% vs. 37%, p = 0.0215). This study was successful in using 3D printing technology to manufacture suture material and provided insight into its usability when compared to standard suture material.

Effect of Novel Compound Redox Initiators on Polymerization Mechanism and Mechanical Properties of Acrylic Resin.

Aiming at the problems of long reaction time and the risk of explosion polymerization of acrylate resin, a small amount of ferrocene (Fc) is added to the existing dibenzoyl peroxide (BPO)/N,N-dimethylaniline (DMA) initiators, and the compound redox initiators (BPO/DMA/ (Fc)) are proposed for acrylate resin polymerization at room temperature. The effect of the content of Fc in the resin on the reaction efficiency and the molding quality of products is researched, and the initiation mechanism of the compound redox initiators is analyzed. It is found that with the addition of Fc, the reaction time of the resin can be shortened by 68% at maximum, the heat release temperature of the resin can be reduced by 40% at maximum, the molecular weight of the reaction products can be increased by 74% at maximum, the tensile and bending properties of the resin castings are increased by 23% and 35% at maximum, respectively, and the bending strength and bending modulus are increased by 57% and 27% at maximum, respectively. The compound redox initiators proposed in this paper can improve the molding efficiency and quality of the product, lay a foundation for the application of acrylic resin in the field of pultrusion molding, perfusion molding, and other in situ molding of thermoplastic composites.

Structural Optimization of PA12/MVQ@POE-g-MAH Ternary Composite for Superior Toughness and Low-Temperature Resistance.

To enhance the low-temperature toughness and resistance of the engineering plastic polyamide PA12, this study introduces novel PA12/MVQ@POE-g-MAH ternary composites using a two-step process and dynamic curing. Analytical results indicate that incorporating MVQ@POE-g-MAH into the PA12 matrix markedly enhances its toughness and heat resistance. As the MVQ@POE-g-MAH content increases, the elongation at break of PA12 composites significantly expands from 52.83% to 204.69%, and the notch impact strength escalates from 8.69 to 74.34 kJ m-2. In addition, the brittleness temperature of PA12 decreases from -59.5 to -67.0 °C. Experimental findings confirm that POE-g-MAH is dispersed at the interface between MVQ and PA12, creating an encapsulated structure of MVQ@POE-g-MAH. This enhancement significantly broadens the potential applications of PA12 by improving its toughness, and resistance to both low and high temperatures, as well as impact endurance.

Dynamic Thermosetting Resins with Synergistic Enhanced Strength and Toughness through Combination with Rigid and Soft Microdomains.

Preparation of materials that possess highly strong and tough properties simultaneously is a great challenge. Thermosetting resins as a type of widely used polymeric materials without synergistic strength and toughness limit their applications in some special fields. In this report, an effective strategy to prepare thermosetting resins with synergistic strength and toughness, is presented. In this method, the soft and rigid microspheres with dynamic hemiaminal bonds are fabricated first, followed by hot-pressing to crosslink at the interfaces. Specifically, the rigid or soft microspheres are prepared via precipitation polymerization. After hot-pressing, the resulting rigid-soft blending materials exhibit superior strength and toughness, simultaneously. As compared with the precursor rigid or soft materials, the toughness of the rigid-soft blending films (RSBFs) is improved to 240% and 2100%, respectively, while the strength is comparable to the rigid precursor. As compared with the traditional crushing, blending, and hot-pressing of rigid or soft materials to get the nonuniform materials, the strength and toughness of the RSBFs are improved to 168% and 255%, respectively. This approach holds significant promise for the fabrication of polymer thermosets with a unique combination of strength and toughness.

Sulfur Free Crosslinking of EPDM Composites via Silane Grafting and Silica Incorporation.

This study aims at evaluating and developing an environmental-friendly and sulfur-free cured ethylene propylene diene monomer (EPDM) composites. Silane grafted EPDM (SiEPDM) composites incorporated with silica is prepared via a solvent-free, one-step reactive mixing process. The silane grafting and silica filler bonding are characterized using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The mechanical properties of the developed composites are examined. The fracture morphology is observed using an environmental scanning electron microscopy. The rheology and thermomechanical properties are evaluated by using a rotational rheometer and dynamic mechanical analyzer. Notably, a robust bonding between silica and the grafted silane is established, yielding a crosslinking network within the composite structure. This phenomenon is substantiated by the observed gel efficiency and rheology behavior. Consequently, a pronounced augmentation of up to 75% in tensile strength and 29% in tear strength are observed in the optimized SiEPDM-silica composites, distinguishing them from their EPDM-silica counterparts. The introduction of paraffin oil contributes to enhanced processability; however, it is concomitant with a reduction in gel efficiency and associated mechanical properties. Furthermore, subsequent UV weathering test unveils that the SiEPDM-silica composites exhibit the highest levels of residual tensile strength and modulus, indicative of their exceptional UV stability.

Transparent Multilayer Acrylic Composites Reinforced with Poly(Acrylated Urethane) Filled Low Grammage Bacterial Cellulose Nanopaper.

Cellulose nanopaper is a material structure that possesses high mechanical performance and is widely regarded as a promising 2D reinforcement for polymer matrix composites. This work explores the use of low grammage bacterial cellulose (BC) nanopaper as reinforcement for poly(acrylated urethane) interlayer adhesive to increase the impact performance of multilayer acrylic composites. The BC nanopaper is impregnated with an acrylated urethane resin and laminated between acrylic sheets to create BC/acrylic composites consisting of one, three, and five layers of BC nanopaper-reinforced poly(acrylated urethane) interlayer adhesive(s). Both the poly(acrylated urethane)-filled BC nanopaper interlayer adhesive and the resulting laminated acrylic composites are optically transparent. The incorporation of BC nanopaper into the poly(acrylated urethane) interlayer adhesive improves the tensile modulus by eightfold and the single-edge notched fracture toughness by 60% compared to neat poly(acrylated urethane). It is also found that using poly(acrylated urethane)-filled BC nanopaper interlayer adhesive proves beneficial to the impact properties of the resulting laminated acrylic composites. In Charpy impact testing, the impact strength of the multilayer acrylic composites increases by up to 130% compared to the "gold-standard" impact-modified monolithic acrylic, with a BC loading of only 1.6 wt%.

Antibacterial effect and biocompatibility of silver nanoparticle-coated bone allograft substitutes.

Osteoinduction, and/or osteoconduction, and antibacterial characteristics are prerequisites for achieving successful bone grafting. This study aimed to coat bone allografts with silver nanoparticles and assess their antibacterial activity and biocompatibility compared to uncoated bone allografts. In this study, the bone allografts were coated with varying concentrations of silver nanoparticles (5 mg/l, 10 mg/l, and 50 mg/l) through a simple adsorption technique. Subsequently, the coated samples underwent characterization using SEM, FTIR, EDS, and XRD. The Minimal Inhibitory Concentration (MIC) of the silver nanoparticles was determined against Staphylococcus aureus and Streptococcus mutans. Bacterial growth inhibition was evaluated by measuring turbidity and performing a disk diffusion test. Moreover, qualitative investigation of biofilm formation on the coated bone allograft was conducted using SEM. Following this, MG-63 cell lines, resembling osteoblasts, were cultured on the bone allografts coated with 5 mg/l of silver nanoparticles, as well as on uncoated bone allografts, to assess biocompatibility. The MIC results demonstrated that silver nanoparticles exhibited antimicrobial effects on both microorganisms, inhibiting the growth of isolates at concentrations of 0.78 mg/L for Staphylococcus aureus and 0.39 mg/L for Streptococcus mutans. The bone allografts coated with varying concentrations of silver nanoparticles exhibited significant antibacterial activity against the tested bacteria, completely eradicating bacterial growth and preventing biofilm formation. The osteoblast-like MG-63 cells thrived on the bone allografts coated with 5 mg/l of silver nanoparticles, displaying no significant differences compared to both the uncoated bone allografts and the control group.  Within the limit of this study, it can be concluded that silver nanoparticles have a positive role in controlling graft infection. In addition, simple adsorption technique showed an effective method of coating without overwhelming the healing of the graft.

Design and preparation of Ti-xFe antibacterial titanium alloys based on micro-area potential difference.

Fe was selected as an alloying element for the first time to prepare a new antibacterial titanium alloy based on micro-area potential difference (MAPD) antibacterial mechanism. The microstructure, the corrosion resistance, the mechanical properties, the antibacterial properties and the cell biocompatibility have been investigated in detail by optical microscopy, scanning electron microscopy, electrochemical testing, mechanical property test, plate count method and cell toxicity measurement. It was demonstrated that heat treatment had a significant on the compressive mechanical properties and the antibacterial properties. Ti-xFe (x = 3,5 and 9) alloys after 850 °C/3 h + 550 °C/62 h heat treatment exhibited strong antimicrobial properties with an antibacterial rate of more than 90% due to the MAPD caused by the redistribution of Fe element during the aging process. In addition, the Fe content and the heat treatment process had a significant influence on the mechanical properties of Ti-xFe alloy but had nearly no effect on the corrosion resistance. All Ti-xFe alloys showed non-toxicity to the MC3T3 cell line in comparison with cp-Ti, indicating that the microzone potential difference had no adverse effect on the corrosion resistance, cell proliferation, adhesion, and spreading. Strong antibacterial properties, good cell compatibility and good corrosion resistance demonstrated that Ti-xFe alloy might be a candidate titanium alloy for medical applications.

Development of a patient-specific model of the human coronary system for percutaneous transluminal coronary angioplasty balloon catheter training and testing.

BACKGROUND: To treat stenosed coronary arteries, percutaneous transluminal coronary angioplasty (PTCA) balloon catheters must combine pushability, trackability, crossability, and rewrap behavior. The existing anatomic track model (ASTM F2394) for catheter testing lacks 3D morphology, vessel tortuosity, and compliance, making evaluating performance characteristics difficult. This study aimed to develop a three-dimensional patient-specific phantom (3DPSP) for device testing and safe training for interventional cardiologists. METHODS: A range of silicone materials with different shore hardnesses (00-30-45 A) and wall thicknesses (0.5 mm, 1 mm, 2 mm) were tested to determine compliance for creating coronary vessel phantoms. Compliance was assessed using optical coherence tomography (OCT) and compared to values in the literature. Stenosis was induced using multilayer casting and brushing methods, with gypsum added for calcification. The radial tensile properties of the samples were investigated, and the relationship between Young's modulus and compliance was determined. Various methods have been introduced to approximate the friction between silicone and real coronary vessel walls. Computerized tomography (CT) scans were used to obtain patient-specific anatomy from the femoral artery to the coronary arteries. Artery lumens were segmented from the CT scans to create dissolvable 3D-printed core models. RESULTS: A 15A shore hardness silicone yielded an experimental compliance of 12.3-22.4 m m 2 mmHg · 10 3 for stenosed tubes and 14.7-57.9 m m 2 mmHg · 10 3 for uniform tubes, aligning closely with the literature data (6.28-40.88 m m 2 mmHg · 10 3 ). The Young's modulus ranged from 43.2 to 75.5 kPa and 56.6-67.9 kPa for the uniform and calcified materials, respectively. The dependency of the compliance on the wall thickness, Young's modulus, and inner diameter could be shown. Introducing a lubricant reduced the silicone friction coefficient from 0.52 to 0.13. The 3DPSP was successfully fabricated, and comparative analyses were conducted among eight commercially available catheters. CONCLUSION: This study presents a novel method for crafting 3DPSPs with realistic mechanical and frictional properties. The proposed approach enables the creation of comprehensive and anatomically precise setups spanning the right femoral artery to the coronary arteries, highlighting the importance of such realistic environments for advancing medical device development and fostering safe training conditions.

Influence of sterilization on the retention forces of lithium disilicate and polymer-infiltrated ceramic-network crowns bonded to titanium base abutments: An in-vitro study.

OBJECTIVES: The aim of this study was to evaluate the effect of sterilization on the retention forces of lithium disilicate (LD) and polymer-infiltrated ceramic network (PICN) crowns bonded to titanium base (Ti-base) abutments. MATERIALS AND METHODS: Forty LD and 40 PICN crowns were milled and then bonded to 80 Ti-bases with two resin composite cements: Multilink Hybrid Abutment (mh) and Panavia V5 (pv) for a total of 8 groups (n = 10). Half of the specimens (test) underwent an autoclaving protocol (pressure 1.1 bar, 121°C, 20.5 min) and the other half not (control). Restorations were screw-retained to implants, and retention forces (N) were measured with a pull-off testing machine. The surfaces of the Ti-bases and the crowns were inspected for the analysis of the integrity of the marginal bonding interface and failure mode. Student's t-test, chi-square test, and univariate linear regression model were performed to analyze the data (α = 0.05). RESULTS: The mean pull-off retention forces ranged from 487.7 ± 73.4 N to 742.2 ± 150.3 N. Sterilized groups showed statistically significant overall higher maximum retention forces (p < .05), except for one combination (LD + mh). Sterilization led to an increased presence of marginal gaps and deformities compared to no-sterilization (p < .001), while no statistically significant relationship was found between failure mode and sterilization (p > .05). CONCLUSIONS: Sterilization may have a beneficial effect on the retention forces of LD and PICN crowns bonded to titanium base abutments, although it may negatively influence the integrity of the marginal bonding interface.

Effect of implant type on the stability of cantilever fixed dental prostheses: An in vitro study.

OBJECTIVES: To simulate the replacement of a premolar with an implant-supported cantilever fixed dental prosthesis (ICFDP) and how the fracture load is affected by implant type, positioning within the zirconia blank, and aging protocol. MATERIALS AND METHODS: Seventy-two ICFDPs were designed either within the enamel- or dentin layer of a 4Y-PSZ blank for bone-level and tissue-level titanium-zirconium implants. Fracture load was obtained on the cantilever at baseline (no aging) or after aging in a chewing simulator with the load applied within the implant axis (axial aging) or on the cantilever (12 groups with n = 6). A three-way ANOVA was applied (α = .05). RESULTS: A three-way ANOVA revealed a significant effect on fracture load values of implant type (p = .006) and aging (p < .001) but not for the position within the zirconia blank (p = .847). Fracture load values significantly increased from baseline bone level (608 ± 118 N) and tissue level (880 ± 293 N) when the implants were aged axially, with higher values for tissue level (1065 ± 182 N) than bone level (797 ± 113 N) (p < .001). However, when the force was applied to the cantilever, fracture load values decreased significantly for tissue-level (493 ± 70 N), while values for bone-level implants remained stable (690 ± 135 N). CONCLUSIONS: For ICFDPs, the use of bone-level implants is reasonable as catastrophic failures are likely to be restricted to the restoration, whereas with tissue-level implants, the transmucosal portion of the implant is susceptible to deformation, making repair more difficult.

In vitro pilot study comparing a novel implantoplasty sonic instrumentation protocol with a conventional protocol using burs.

BACKGROUND AND OBJECTIVES: The aim of implantoplasty (IP) is to remove titanium implant layers that have been contaminated and to smoothen the implant surfaces so they retain less plaque. However, existing IP methods are very invasive and reduce implant wall thickness. AIM: To investigate the suitability of novel sonic tips in IP and to compare this novel protocol with conventional abrasive procedures. MATERIALS AND METHODS: Thirty dental implants (Ø 4.1 mm, 10 mm length) were distributed in three groups and investigated according to the protocol of Sivolella et al., with modifications to the instrument's feed rate, the applied contact force, and the speed of implant rotations per minute. The upper third of the implant was processed with a diamond-coated bur (BUR) or novel non-diamond-coated sonic tips (AIRSCALER). After standardized IP, the surfaces were analyzed by tactile profilometry and scanning electron microscopy (SEM). Changes in implant weight, implant material loss, and implant fracture strength were assessed. RESULTS: The mean roughness (Ra , Sa ), implant material loss, and change in implant weight were significantly lower in the AIRSCALER group than in the BUR group, whereas the mean compression resistance values were significantly higher in the AIRSCALER group than in the BUR group. CONCLUSIONS: IP with uncoated sonic tips smoothes the surfaces and reduces structural loss of the implant in the area of microthreads. This new IP method could be of great clinical importance, especially for implants with microthreads and reduced diameter or wall thickness.

Mechanical stability of posterior implant-supported monolithic zirconia cantilever on titanium-base abutments. An in vitro study.

PURPOSE: Investigate survival and technical complications of two-unit posterior implant-supported cantilever made of monolithic zirconia on titanium-base abutments (Zr-TiB) vs. porcelain-fused-to-metal on castable gold abutments (PFM-GA) using two different implant connections, internal butt-joint (IBJ) and internal conical (IC). MATERIALS AND METHODS: Forty-eight implants (4.3 mm diameter) were divided into four groups (n = 12) to support 2-unit mandibular premolar cantilevers with two different materials (Zr-TiB vs. PFM-GA) and two connection types (IBJ vs. IC). Tested groups were as follows: (1) IBJ/Zr-TiB; (2) IBJ/PFM-GA; (3) IC/Zr-TiB; and (4) IC/PFM-GA. Specimens were thermomechanical aged (1,200,000 cycles, 98 N, 5-55°C) with occlusal axial load on the pontic. Catastrophic and non-catastrophic events were registered, and removal torque values measured before and after aging. Specimens surviving aging were subjected to loading until failure. Survival, total complication rates, torque loss (%), and bending moments were calculated. RESULTS: From 48 specimens, 38 survived aging. Survival rates significantly varied from 16.7% (IC/PFM-GA) to 100% (IBJ/Zr-TiB; IBJ/PFM-GA; IC/Zr-TiB) (p < .01). Internal conical connection revealed significantly higher torque loss (IC/ZrTiB - 67%) compared to internal butt-joint (IBJ/Zr-TiB - 44%; IBJ/PFM-GA - 46%) (p < .01). Bending moments were higher in internal butt-joint connections than in internal conical (p < .05). CONCLUSION AND CLINICAL IMPLICATIONS: Two-unit posterior implant-supported cantilever FDPs replacing mandibular premolars composed of monolithic zirconia on titanium-base abutments demonstrated higher mechanical stability compared to porcelain-fused-to-metal on castable gold abutments in this in vitro study. The internal conical connection combined with porcelain-fused-to-metal on gold abutments revealed a high number of failures; therefore, their clinical use may be considered cautiously for this indication.

Effects of erosion and abrasion on resin-matrix ceramic CAD/CAM materials: An in vitro investigation.

The aim of the study was to evaluate the effects of erosion and abrasion on resin-matrix ceramic CAD/CAM materials [CERASMART (GC); VITA ENAMIC (VITA Zahnfabrik); Lava Ultimate (3 M)] in comparison to feldspar ceramic (VITABLOCS Mark II, VITA Zahnfabrik) and resin composite materials (ceram.x universal, Dentsply Sirona). Daily brushing and acid exposure were simulated using a brushing apparatus and a solution of 0.5 vol% citric acid. Microhardness, surface roughness, and substance loss were measured at baseline and after simulation of 1 and 3 years of function. All materials showed a decrease in microhardness after 3 years and an increase in surface roughness (Ra) after 1 and 3 years. The Ra increase was statistically significantly lower for the resin-matrix ceramics than for feldspar ceramic and similar to composite material. After 3 years, only feldspar ceramic showed no significant substance loss. In conclusion, resin-matrix ceramics demonstrate reduced roughening compared to feldspar ceramics, potentially improving restoration longevity by preventing plaque buildup, but differences in abrasion resistance suggest the need for further material-specific research. Future research should aim to replicate clinical conditions closely and to transition to in vivo trials.

Microstructure, physical and mechanical properties of dental polychromic multilayer zirconia of uniform composition.

The present study aimed to compare the microstructure, physical, and mechanical properties of three commercially available dental polychromatic multilayer zirconia materials of uniform composition: Dima Mill Zirconia ML, VITA YZ/ST Multicolor, and VITA YZ/XT Multicolor (with 3, 4, and 5 mol% Y2 O3 , respectively); thus, the influence of Y2 O3 content on the above properties of the produced materials was experimentally studied. Homogeneous zirconia ceramics with a dense micro- and nanostructure, without pores or defects, were produced after milling the blocks and sintering, which resulted in yttrium-stabilized tetragonal and cubic zirconia. Statistical analysis of the results of measurable magnitudes was performed by the one-way ANOVA test. The increase of Y2 O3 content (from 3 to 5 mol%) favored larger grain and crystallite sizes and a decrease of the values of the mechanical properties; yet, the differences were statistically insignificant. Clinically, these differences are expected to have no impact on their function in the oral cavity, both in terms of their fracture propensity and the damage that can be caused to the opposing teeth. Accordingly, the experimental results qualify the polychromic multilayer zirconia ceramics of uniform composition fabricated by milling technology for use in dental restorations.