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Hong-Joo Kim,1 Seon-Ki Lee,2 Hyun-Seung Kim,3 Won-Jae Kim,4 Je-Hwang Ryu,5 Min-Kyung Ji,6 Hyun-Pil Lim1 1Department of Prosthodontics, School of Dentistry, Chonnam National University, Gwangju, Republic of Korea; 2Department of Prosthodontics, Daejeon Dental Hospital, Wonkwang University, Daejeon, Republic of Korea; 3KJ Meditech Co., Ltd, Gwangju, Republic of Korea; 4Department of Oral Physiology, School of Dentistry, Stem cell Secretome Research Center, Chonnam National University, Gwangju, Republic of Korea; 5Department of Pharmacology and Dental Therapeutics, School of Dentistry, Chonnam National University, Gwangju, Republic of Korea; 6Dental 4D Research Center, Chonnam National University, Gwangju, Republic of KoreaCorrespondence: Hyun-Pil Lim, Department of Prosthodontics, School of Dentistry, Chonnam National University, Gwangju, 61186, Republic of Korea, Tel +82-10-2645-7528, Fax +82-62-530-5639, Email mcnihil@jnu.ac.kr Min-Kyung Ji, Dental 4D Research Center, Chonnam National University, Gwangju, 61186, Republic of Korea, Tel +82-10-8432-3639, Fax +82-62-530-5639, Email perizimin@gmail.comPurpose: Atomic layer deposition (ALD) is a method that can deposit zirconia uniformly on an atomic basis. The effect of deposited zirconia on titanium implants using ALD was evaluated in vivo.Methods: Machined titanium implants (MTIs) were used as the Control. MTIs treated by sandblasting with large grit and acid etching (SA) and MTIs deposited with zirconia using ALD are referred to as Groups S and Z, respectively. Twelve implants were prepared for each group. Six rabbits were used as experimental animals. To evaluate the osteogenesis and osteocyte aspects around the implants, radiological and histological analyses were performed. The bone-to-implant contact (BIC) ratio was measured and statistically analyzed to evaluate the osseointegration capabilities.Results: In the micro-CT analysis, more radiopaque bone tissues were observed around the implants in Groups S and Z. Histological observation found that Groups S and Z had more and denser mature bone tissues around the implants in the cortical bone area. Many new and mature bone tissues were also observed in the medullary cavity area. For the BIC ratio, Groups S and Z were significantly higher than the Control in the cortical bone area (P < 0.017), but there was no significant difference between Groups S and Z.Conclusion: MTIs deposited with zirconia using ALD (Group Z) radiologically and histologically showed more mature bone formation and activated osteocytes compared with MTIs (Control). Group Z also had a significantly higher BIC ratio than the Control. Within the limitations of this study, depositing zirconia on the surface of MTIs using ALD can improve osseointegration in vivo.Keywords: atomic layer deposition, ALD, zirconia, machined titanium implant, bone-to-implant contact ratio, BIC, osseointegration

Abstract Background Cement spacer is essential for compensating deformation of zirconia restoration after sintering shrinkage, allowing proper seating and better fracture resistance of the restoration. Studies assessing the effect of cement spacer on fit accuracy and fracture strength of zirconia frameworks are missing in the literature. Therefore, the aim of this study was to evaluate the effect of different cement spacer settings on fit accuracy and fracture strength of 3-unit and 4-unit zirconia frameworks. Methods Sixty standardized stainless-steel master dies were manufactured with 2 prepared abutments for fabricating 3-unit and 4-unit zirconia frameworks. The frameworks were assigned into 6 groups (n = 10) according to cement spacer setting (30 μm, 50 μm, and 80 μm) as follows: 3-unit frameworks; 3u-30, 3u-50, 3u-80, and 4-unit frameworks; 4u-30, 4u-50, and 4u-80. The frameworks were assessed for fit accuracy with the replica method. The specimens were cemented to their corresponding dies, and the fracture strength was measured in a universal testing machine. The Weibull parameters were calculated for the study groups and fractured specimens were inspected for failure mode. Two-Way ANOVA followed by Tukey test for pairwise comparison between study groups (α = 0.05). Results The cement spacer had a significant effect on both fit accuracy and fracture strength for 3-unit and 4-unit frameworks. The 50 μm spacer had significantly better fit accuracy followed by 80 μm, and 30 μm spacers. Both 50 μm and 80 μm spacers had similar fracture strength, and both had significantly better strength than 30 μm spacer. Conclusions For both 3-unit and 4-unit zirconia frameworks, 50 μm cement spacer can be recommended over 30 μm and 80 μm spacers for significantly better fit accuracy and adequate fracture strength.

Aims: The objectives of the study were to compare the adaptation of presintered zirconia and cobalt– chromium prostheses using microcomputed tomography (μCT), scanning electron microscopy (SEM), and stereomicroscope (SM). Materials and Methods: Twenty-four fixed dental prostheses (FDPs) were fabricated on metal abutments, duplicated from maxillary first premolar and first molar prepared on a typodont model. Teeth were reduced to obtain chamfer of 1.2 mm and reduction occlusaly of 2 mm occlusal. Scanning of the abutments was done with random assignment to two groups receiving the FDPs made from soft-milled Co-Cr (n = 12) and zirconia (n = 12). Marginal and internal gaps were assessed using three evaluation techniques (X-ray microcomputer tomography, SEM, and stereomicroscopy). Statistical Analysis Used: Comparison of the results was made using Levene and analysis of variance tests (α =0.05). Results: Irrespective of the material tested, statistical differences were found between the measuring techniques (P = 0.001 overall); the obtained mean gaps were for CT scan (92.60 ± 13.31), for SEM (101.92 ± 23.03), and for SM (113.44 ± 14.68): the multiple comparisons between techniques found a significant difference between CT and SM (P < 0.001), and SEM and SM (P = 0.025). When materials were compared within each measuring technique, Co-Cr showed lower values compared to zirconia in SEM (P < 0.001) and Stereo (P = 0.049); similar results were found in CT. Conclusions: Results values differed with the chosen measuring technique. Co-Cr prostheses had a better fit than zirconia prostheses in SEM and Stereo. μCT showed comparable results to SEM, smaller than SM results.

Objective: The purpose of this study was to evaluate the effect of veneering with lithium-disilicate glass-ceramic material on the marginal microleakage of zirconia-supported crowns. Methods: Ten freshly extracted human third molars were embedded in an acrylic mold from the roots. Crown preparation of each tooth half was handled differently. The distal half of each tooth was prepared with a chamfer-type margin (1.2 mm), while the mesial half was finished with a mini-chamfer (0.6 mm). Zirconia frameworks were designed and manufactured with computer-aided design/computer-aided manufacturing, and the frameworks were veneered on the distal surfaces of the framework using lithium-disilicate glass-ceramic. Specimens were thermocycled and immersed in a basic fuchsine dye solution for 24 hours. Four cross-sections were made from each specimen (n=40), and dye penetrations were recorded under a stereo microscope for microleakage measurements. The microleakage values were statistically analyzed with a Mann-Whitney U test (α=0.05). Results: Mean microleakage values were recorded for each group. The values for the ceramic veneered margin group were noted as 1.17±0.69 mm, while the values for the zirconia margin group were noted as 1.03±0.74 mm. The results did not show significant differences for the compared groups (p=0.102). Conclusion: Lithium-disilicate glass-ceramic veneering for zirconia-supported restorations did not enhance the marginal seal capability.

Amaç: Bu çalışmanın amacı, alüminyum oksit partikülleriyle kumlama sonrası kullanılan farklı primerlerin ve universal adezivin, termal yaşlandırma sonrasında zirkonya ile self adeziv rezin siman arasındaki makaslama bağlanma dayanımı üzerindeki etkisini değerlendirmektir. Gereç ve Yöntem: Çalışmamızda CAD/CAM zirkonya bloklardan boyutları 2 mm x 11 mm x 11 mm olacak şekilde 20 adet dörtgen örnek hazırlanmıştır. Tüm örneklerin yüzeyine 50 µm Al2O3 partikülleri yüzey pürüzlendirme işlemi uygulanmıştır. Hazırlanan örnekler farklı primer ve adeziv uygulamalarına göre 4 alt gruba ayrılmıştır (n=5). Kontrol: Herhangi bir primer veya universal adeziv uygulanmamıştır. Kerr Silane Primer (Negatif Kontrol): MDP içeriği bulunmayan seramik primeri uygulanmıştır. Ceramica-S ve Nova Compo-B Plus: Ceramica-S primer ve Nova Compo-B Plus universal adeziv karıştırılarak uygulanmıştır. Clearfil Ceramic Primer Plus: Clearfil Ceramic Primer Plus uygulanmıştır. Yüzey uygulamalarını takiben self adeziv rezin siman seramik yüzeylerine polimerize edilmiştir. Ardından örnekler 5000 devir termal döngü işlemine tabi tutulmuştur. Örneklere universal test cihazında makaslama bağlanma dayanımı testi uygulanmıştır. Yüzey işlemlerine göre Fmax (N) ve Mpa değerlerinin karşılaştırılmasında Tek Yönlü Varyans Analizi kullanılmıştır. Bulgular: Farklı primer ve adeziv kullanımına göre Fmax (N) ortalama değerleri istatistiksel olarak anlamlı bir farklılık göstermiştir (p0,001). Sonuç: Mevcut limitasyonlar dahilinde, self adeziv rezin simanın herhangi bir primer uygulaması olmaksızın veya MDP içermeyen bir primer uygulanmasının, zirkonya seramik yüzeyine bağlanma gücünü artırmak için yeterli olmadığı sonucuna varılabilir. MDP içeren ve kumlama sonrası uygulanan primerler veya adezivler, zirkonyaya bağlanma için ideal bir seçenek olarak görünmektedir. Anahtar Kelimeler: Primer, Universal adeziv, Zirkonya

Abstract Background The aim of this study is to evaluate the biomechanical behavior of the mesial and distal off-axial extensions of implant-retained prostheses in the posterior maxilla with different prosthetic materials using finite element analysis (FEA). Methods Three dimensional (3D) finite element models with three implant configurations and prosthetic designs (fixed-fixed, mesial cantilever, and distal cantilever) were designed and modelled depending upon cone beam computed tomography (CBCT) images of an intact maxilla of an anonymous patient. Implant prostheses with two materials; Monolithic zirconia (Zr) and polyetherketoneketone (PEKK) were also modeled .The 3D modeling software Mimics Innovation Suite (Mimics 14.0 / 3-matic 7.01; Materialise, Leuven, Belgium) was used. All the models were imported into the FE package Marc/Mentat (ver. 2015; MSC Software, Los Angeles, Calif). Then, individual models were subjected to separate axial loads of 300 N. Von mises stress values were computed for the prostheses, implants, and bone under axial loading. Results The highest von Mises stresses in implant (111.6 MPa) and bone (100.0 MPa) were recorded in distal cantilever model with PEKK material, while the lowest values in implant (48.9 MPa) and bone (19.6 MPa) were displayed in fixed fixed model with zirconia material. The distal cantilever model with zirconia material yielded the most elevated levels of von Mises stresses within the prosthesis (105 MPa), while the least stresses in prosthesis (35.4 MPa) were recorded in fixed fixed models with PEKK material. Conclusions In the light of this study, the combination of fixed fixed implant prosthesis without cantilever using a rigid zirconia material exhibits better biomechanical behavior and stress distribution around bone and implants. As a prosthetic material, low elastic modulus PEKK transmitted more stress to implants and surrounding bone especially with distal cantilever.

Polymer derived ceramics (PDCs) technology has the advantages of simple manufacturing and adjustable composition, providing an effective way to prepare new types of ceramics. However, due to the escape of tiny molecules during the pyrolysis process, the pore defects are formed, and amorphous polymer derived SiCNO ceramics (PDCs SiCNO ceramics) produced by precursor technique have poor mechanical properties. To solve the aforementioned problems, enhancement of the polymer-derived ceramics is achieved by adding a second phase (particles reinforcement) to the ceramic matrix. A method was proposed to obtain ZrO2 reinforced PDCs-SiCNO composite ceramics (PDCs-SiCNO-ZrO2) by ball-milling of polyvinylsilazane (PVSZ) and ZrO2 followed by pyrolyzing. The phase structure and mechanical properties of PDCs-SiCNO-ZrO2 composite ceramics were investigated, respectively. The results show that the introduced ZrO2 fillers are embedded in the matrix of PDCs-SiCNO ceramic as a reinforcement, which not only can effectively reduce the linear shrinkage, but also greatly enhance the mechanical properties of the PDCs-SiCNO-ZrO2 composite ceramics. PDCs-SiCNO-ZrO2 composite ceramics with a 10%(mass fraction) ZrO2 addition have the flexural and compressive strengths of 197.03 MPa and 375.2 MPa, which are 64% and 267% greater than those of PDCs-SiCNO ceramics. The highest hardness value can reach 20.92 GPa, and the fracture toughness can reach 2.76 MPa·m1/2. The addition of appropriate content of ZrO2 contributes to the densification of the PDCs-SiCNO ceramic matrix, which enhances the mechanical properties of the PDCs-SiCNO-ZrO2 composite ceramics.

Background/purpose: Translucent monolithic zirconia restorations have recently introduced. The purpose of this study was to evaluate the clinical behavior and the survival rate of the posterior third-generation monolithic zirconia crowns (MZCs) during three years of clinical service. Materials and methods: Twenty-four patients who needed thirty crowns were enrolled in this study. Digital impressions were made, and the crowns were milled and cemented with a resin cement. The crowns outcomes were assessed using the California Dental Association's (CDA) criteria. Gingival index (GI), plaque index (PI), and periodontal probing depth (PPD) for MZCs and contralateral natural teeth (control) were assessed. Margin index (MI) for MZCs was also assessed. Data analysis was conducted using the Wilcoxon signed-rank and the Friedman tests. Results: The 3-year survival rate was 100%. All MZCs were rated as satisfactory throughout the follow-up period, and no biological or mechanical complications were observed. No differences were recorded when GI, PI and PPD at 3-year of follow-up were compared to baseline. No differences were recorded between crowned and control teeth. The MI remained stable throughout the study period. Conclusion: The third-generation monolithic zirconia appears to be a good treatment option for the rehabilitation of posterior single teeth.

Background/purpose: Nowadays, zirconia-based framework has been used for longspan or full-arch fixed dental prostheses (FDPs). This study aimed to evaluate the effect of pontic distribution on marginal and internal gaps of five-unit anterior zirconiabased DPs. Materials and methods: Right maxillary central incisor and second premolar were selected as terminal abutments and three different edentulous conditions with one nonterminal abutment were simulated. Marginal and internal gaps in each zirconia-based samples(n = 10) were examined by computer-aided replica technique. Five regions, including marginal gaps at mesial or distal finishing line, internal gaps at the mesial or distal axial wall, and occlusal surface, were statistically analyzed (α = .05). Results: Most of marginal gaps and internal gaps at axial wall were clinically acceptable, but larger at occlusal surface. For the three experimental groups, clinically accepted percentage with qualified gaps were less than 30%.There were statistical differences at axial wall over pontic side and marginal gaps over non-pontic side between groups (P

Purpose: To evaluate the influence of the milliamperage and artifact reduction (AR) tool on the diagnosis of buccal and lingual peri-implant dehiscences related to titanium-zirconia (Ti-Zr) and zirconia (Zr) implants using CBCT images. Materials and Methods: Ti-Zr and Zr implants were alternately inserted in 20 sites in the posterior region of three human mandibles that presented intact cortical (control) bones or simulated buccal and/or lingual peri-implant dehiscences. CBCT images were acquired with an OP300 Maxio unit, varied milliamperage (5 and 8 mA), and the use of AR tool. Three oral radiologists assessed the presence of dehiscences using a 5-point scale. The area under the receiver operator characteristic curve (Az), sensitivity, and specificity of each group (control and dehiscence) were obtained and compared using multiway ANOVA (α = .05). Results: The milliamperage and the AR tool did not influence the diagnosis of dehiscences, and there were no differences between the buccal and lingual cortices (P > .05). However, Zr implants showed a higher sensitivity (0.67 to 0.89) and lower specificity (0.26 to 0.44) than Ti-Zr implants (0.19 to 0.44 and 0.93 to 1.00, respectively; P < .05). Az values did not differ between the implant types (P > .05). Conclusions: Dehiscences were more detectable when related to Zr implants, while the absence of dehiscences was more correctly visualized adjacent to Ti-Zr implants. The use of varied milliamperages and the AR tool did not affect the diagnosis of peri-implant dehiscences, regardless of the involved cortical (buccal or lingual) bones. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the fracture load of monolithic, single-tooth implant-supported crowns cemented on solid or Ti-base (Variobase C) abutments. Materials and Methods: Besides abutment types (solid and Ti-base abutments), two ceramic systems (IPS e.max CAD and Zirconia inCoris ZI) and two occlusal thicknesses (0.5 and 1.5 mm) were also investigated in this study. In total, eight groups (n = 8) with 64 maxillary second premolar crowns were fabricated. All the crowns were cemented with resin cement, and the screw accesses in Ti-base groups were sealed with composite resin. After mechanical cycling, the specimens were submitted to fracture load test with the maximum force recorded in Newtons (N). Three-way analysis of variance (ANOVA) and Tukey post hoc test were used for statistical analyses (α = .05). Results: Both the abutment type (P = .0001) and the ceramic system (P = .0001) significantly affected the results. Screw-access channels reduced the fracture load of crowns by half compared to those cemented on solid abutments. The 1.5-mm and 0.5-mm zirconia crowns placed on solid abutments had similar highest fracture loads, while the e.max CAD groups positioned on Ti-base abutments showed significantly lower values compared with other groups. Conclusion: The screw access reduces the resistance of crowns supported by Ti-base abutments compared to crowns cemented on solid abutments. The inCoris ZI showed a higher fracture load than the IPS e.max CAD regardless of the abutment type and thickness. [ABSTRACT FROM AUTHOR]

Purpose: To compare three different types of custom-made root-analog immediate (RAI) dental implants. Materials and Methods: Patients with fractured and/or nonrestorable teeth with uncompromised periodontal ligaments were included in the study. The exclusion criteria were as follows: any uncontrolled systemic disease, bruxism, poor oral hygiene, active periodontal disease, and/or chronic marginal periodontitis. CBCT scans of the teeth were taken, and the datasets were used to reconstruct 3D models that were transferred to 3D modeling software to design the RAIs. Group 1 (GR1) consisted of zirconia RAIs manufactured using a computer numerical control (CNC) machine, group 2 (GR2) consisted of titanium RAIs formed by using a CNC machine, and group 3 (GR3) consisted of titanium RAIs manufactured by using direct laser metal sintering (DLMS) technology, all of which were placed immediately after tooth extraction. Primary stability was measured by using Periotest M. Metal-ceramic single crowns were cemented 3 months later. All implants were evaluated clinically and radiologically 1 year after implant placement. Results: A total of 51 patients (18 men, 33 women) aged between 18 and 66 years (average 34.2 years) were included in the study. In 4 patients, RAIs could not be placed due to the lack of primary stability, and they were excluded. In the remaining 47 patients, the custom-made RAIs (GR1: n = 21, GR2: n = 17, GR3: n = 18, total: n = 56) were placed into fresh extraction sockets immediately after tooth extraction for each patient. Primary stability was achieved. Periotest values (PTV) were between -1.4 and -6.2 (mean -3.3). The mean initial PTV (PTV0) was -2.3 ± 1.8 for the failed implants and -4.5 ± 0.8 for the surviving implants. PTV0 was an independent risk factor (HR 3.61, 95% CI: 1.56-8.35, P = .004) for survival rate, which was 33.3%, 70.6%, and 44.4% for GR1, GR2, and GR3, respectively. The overall survival rate was 48.2%. There was no significant difference between the groups regarding the probability of survival (P = .051). The survival rate was significantly lower for anterior RAIs (P < .001). Clinically healthy gingival margins were observed without any signs of periodontitis or implant mobility, and the mean PTV was -4.0 ± 1.9 in surviving implants, whereas the mean marginal bone loss was 1.3 ± 0.6 mm (median, 0.8; 95% CI: 0.1-3.4) at the 1-year follow-up. Conclusion: This study was the first attempt to compare different RAI manufacturing techniques and biomaterials in the literature. Although the probability of survival was not statistically significant between the groups, the survival rate in GR2 was higher than in the other two groups. Nevertheless, the overall survival rate was significantly lower (48.2%) than in the previous reports. Primary stability was an independent risk factor for failure. Further studies with the minimized variables between groups should be designed for precise results. [ABSTRACT FROM AUTHOR]

Abstract:  Currently, around 50% (~178 million) of all Americans are missing at least 1 tooth, with 12% (~40 million) of Americans missing all of their teeth. Dental implants are a common solution to this issue; titanium is the leading material of choice. Zirconia ceramic dental implants are a suitable replacement for titanium, but are often criticized for their brittleness. By developing a tantalum functional gradient coating, we hope to increase the viability of zirconia ceramic materials for dental implants. Two sets of material were chosen to test the proprietary BruxZir tantalum ion solution: yttria stabilized zirconia (3Y-TZP) and alumina toughened zirconia (ATZ). Solutions with varying concentrations of 0%, 10%, 15%, and 30% weight percent tantalum were prepared, and the ceramic samples were coated and sintered. Each sample was analyzed through various characterization methods, including SEM, EDS, XRD, nanoindentation, and Raman spectroscopy to observe how the solution impacted each sample’s microstructure and mechanical properties. Although our results are still in progress, we found evidence of an inverse relationship between tantalum concentration and grain size.

Proton conductivity in fluorite-structured RE 2 O 3 –ZrO 2 solid solutions (RE = Gd, Sm, and Nd) with the composition of [RE 2 O 3 ]/[ZrO 2 ] ∼ 1 was studied. By screening the proton solubility and diffusivity using the tracer diffusion technique with secondary ion mass spectrometry (SIMS) depth profiling, Nd 0.7 Zr 0.3 O 1.65 was found to exhibit the highest proton conductivity among the prepared RE 2 O 3 –ZrO 2 systems. Detailed electrical conductivity measurements at various atmospheric conditions and temperatures revealed that Nd 0.7 Zr 0.3 O 1.65 is a nearly pure proton conductor below 600 °C under a reducing atmosphere, whereas electron-hole conduction is dominant under an oxidizing atmosphere. The proton conductivity was 1 × 10−4 S cm−1 at 600 °C, which is approximately two orders of magnitude lower than that of Y 2 O 3 -doped BaZrO 3. Because proton solubility in Nd 0.7 Zr 0.3 O 1.65 and Y 2 O 3 -doped BaZrO 3 are similar, the lower conductivity was attributed to the lower proton diffusivity. • H+-conductivity in fluorite-structured RE 2 O 3 –ZrO 2 solid solutions (RE = Gd, Sm, and Nd) was studied. • Nd 0.7 Zr 0.3 O 1.65 is the best H+-conductor among the prepared systems (1 × 10−4 S cm−1 at 600 °C). • Nd 0.7 Zr 0.3 O 1.65 is a nearly pure H+-conductor below 600 °C under a reducing atmosphere. [ABSTRACT FROM AUTHOR]

Developing efficient and anti‐corrosive oxygen reduction reaction (ORR) catalysts is of great importance for the applications of proton exchange membrane fuel cells (PEMFCs). Herein, we report a novel approach to prepare metal oxides supported intermetallic Pt alloy nanoparticles (NPs) via the reactive metal‐support interaction (RMSI) as ORR catalysts, using Ni‐doped cubic ZrO2 (Ni/ZrO2) supported L10−PtNi NPs as a proof of concept. Benefiting from the Ni migration during RMSI, the oxygen vacancy concentrations in the support are increased, leading to an electron enrichment of Pt. The optimal L10−PtNi−Ni/ZrO2−RMSI catalyst achieves remarkably low mass activity (MA) loss (17.8 %) after 400,000 accelerated durability test cycles in a half‐cell and exceptional PEMFC performance (MA=0.76 A mgPt−1 at 0.9 V, peak power density=1.52/0.92 W cm−2 in H2−O2/−air, and 18.4 % MA decay after 30,000 cycles), representing the best reported Pt‐based ORR catalysts without carbon supports. Density functional theory (DFT) calculations reveal that L10−PtNi−Ni/ZrO2−RMSI requires a lower energetic barrier for ORR than L10−PtNi−Ni/ZrO2 (direct loading), which is ascribed to a decreased Bader charge transfer between Pt and *OH, and the improved stability of L10−PtNi−Ni/ZrO2−RMSI compared to L10−PtNi−C can be contributed to the increased adhesion energy and Ni vacancy formation energy within the PtNi alloy. [ABSTRACT FROM AUTHOR]

Hydrogen atoms can enter into metallic materials through penetration and diffusion, leading to the degradation of the mechanical properties of the materials, and the application of hydrogen barrier coatings is an effective means to alleviate this problem. Zirconia coatings (ZrO2) have been widely studied as a common hydrogen barrier coating, but zirconia undergoes a crystalline transition with temperature change, which can lead to volumetric changes in the coating and thus cause problems such as cracking and peeling of the coating. In this work, ZrO2 coating was prepared on a Q235 matrix using a sol-gel method, while yttria-stabilized zirconia (YSZ) coatings with different contents of rare earth elements were prepared in order to alleviate a series of problems caused by the crystal form transformation of ZrO2. The coating performances were evaluated by the electrochemical hydrogen penetration test, pencil hardness test, scratch test, and high-temperature oxidation test. The results show that yttrium can improve the stability of the high-temperature phase of ZrO2, alleviating the cracking problem of the coating due to the volume change triggered by the crystalline transition; improve the consistency of the coating; and refine the grain size of the oxide. The performance of YSZ coating was strongly influenced by the yttria doping mass, and the coating with 10 wt% yttria doping had the best hydrogen barrier performance, the best antioxidant performance, and the largest adhesion. Compared with the matrix, the steady-state hydrogen current density of the YSZ coating decreased by 72.3%, the antioxidant performance was improved by 65.8%, and the ZrO2 coating hardness and adhesion levels were B and 4B, respectively, while YSZ coating hardness and adhesion were upgraded to 2H and 5B. With the further increase in yttrium doping mass, the hardness of the coating continued to improve, but the defects of the coating increased, resulting in a decrease in the hydrogen barrier performance, antioxidant performance, and adhesion. In this work, the various performances of ZrO2 coating were significantly improved by doping with the rare earth element, which provides a reference for further development and application of oxide coatings. [ABSTRACT FROM AUTHOR]

Although advancements in CAD/CAM technology allow for more personalized treatments, it is not clear how modifications in the CAD/CAM milling process could affect the restoration surface conditions and their mechanical behavior. The objective of this study was to evaluate the effect of different CAD/CAM milling protocols on the topography and fracture behavior of zirconia monolithic crowns (3Y-PSZ) subjected to a chewing simulation. Monolithic 3Y-PSZ premolar crowns were milled using three protocols (n = 13) (slow (S), normal (N), and fast (F)). Crowns were cemented on a dentin analog abutment and subjected to mechanical aging (200 N, 2 Hz, 1,500,000 cycles, 37 °C water). Surviving crowns were subjected to compressive load test and analyzed using fractography. Fracture load data were analyzed with two-parameter Weibull analysis. The surface topography of the crowns was examined with a stereomicroscope and a 3D non-contact profiler. All crowns survived the chewing simulation. Crowns milled using the F protocol had the greatest characteristic fracture load, while crowns produced with the S protocol showed high Weibull modulus. Groups N and S had a more uniform surface and detailed occlusal anatomy than group F. The CAD/CAM milling protocol affected the topography and mechanical behavior of 3Y-PSZ monolithic crowns. [ABSTRACT FROM AUTHOR]

Brine magnesia and fused Al 2 O 3 –ZrO 2 powder were used as raw material to prepare MgO–Al 2 O 3 –ZrO 2 (MAZ) refractory brick which was sintered at 1690 °C for 8 h in a tunnel kiln. Its resistance to slag corrosion of non-ferrous metallurgy was investigated. The phase and microstructure of the samples before and after corrosion were characterized by XRD, SEM and EDS. The results show that MAZ ternary metastable phase was formed during sintering, which then decomposes to finely dispersed MgO, MgAl 2 O 4 , and ZrO 2. Thus, highly uniform distribution of ultra-fine MgAl 2 O 4 and ZrO 2 in the matrix was achieved. The non-ferrous metallurgical slag is mainly composed of FeO and SiO 2. At high temperatures, when the material is subjected to slag corrosion, both (Mg, Fe)Al 2 O 4 and 2MgO·SiO 2 with high-temperature melt point were formed in the corrosion layer, effectively preventing further infiltration and corrosion of MAZ samples by slag. A model for the formation process of high dispersion of MAZ was explained, and a model for the corrosion mechanism between non-ferrous metallurgical slag and MAZ samples was established. [ABSTRACT FROM AUTHOR]

Objective: To investigate the fracture resistance and failure modalities of anterior endocrown restorations fabricated employing diverse ceramic materials, and bonded using various cementation methodologies. Materials and methods: Forty maxillary central incisors were divided into two main groups based on the ceramic materials used; GroupI (Zir): zirconia endocrwons (Zolid HT+, Ceramill, Amanngirrbach) and GroupII (E-Max): e-max endocrowns (IPS e.max CAD, Ivoclar Vivadent). Both groups were further split into two subgroups depending on the cementation protocols; subgroup IA "ZirMDP": endocowns cemented with MDP primer + MDP resin cement, subgroup IB (ZirNon-MDP): cemented with MDP primer + non-MDP resin cement, subgroup IIA (E-maxMDP): cemented with MDP primer + MDP resin cement, subgroup IIB (E-maxNon-MDP): cemented with MDP primer + non-MDP resin cement. (n = 10/subgroup). Endocrowns were manufactured using CAD/ CAM. Teeth were subjected to 10,000 thermal cycles. The fracture test was performed at 45o with a palatal force direction until the fracture occurred. Test results were recorded in Newton. The failure mode was examined using a stereomicroscope. A One-way ANOVA test was utilized to compare different groups regarding fracture strength values. Tukey's Post Hoc was utilized for multiple comparisons. Results: The comparative analysis of fracture strength across the diverse groups yielded non-significant differences, as indicated by a p-value exceeding 0.05. Nonetheless, an observable trend emerged regarding the mode of failure. Specifically, a statistically significant prevalence was noted in fractures localized within the endocrown/tooth complex below the cementoenamel junction (CEJ) across all groups, except for Group IIB, "E-max Non-MDP," where fractures within the endocrown/tooth complex occurred above the CEJ. Conclusions: Combining an MDP-based primer with an MDP-based resin cement did not result in a significant effect on the anterior endocrown fracture strength. Clinical relevance: Regardless of the presence of the MDP monomer in its composition, adhesive resin cement achieved highly successful fracture strength when used with MDP-based ceramic primers. Additionally, ceramic materials exhibiting elastic moduli surpassing those of dentin are discouraged due to their propensity to induce catastrophic fractures within the tooth structure. [ABSTRACT FROM AUTHOR]

The study investigated the viability of 3D-printed zirconia specimens created using solvent-based ceramic slurry stereolithography (3S), focusing on their utility in dental ultra-thin laminate veneers. Solvent debinding was employed to minimize defect risks, with the debinding process designed based on thermogravimetric analysis. The study evaluated how solvent debinding affected the microstructural and mechanical properties of the zirconia specimens. Optical properties of 0.1 mm and 0.3 mm thick ultra-thin veneers were characterized, focusing on color parameters and relative translucency (RTP 00) values. Following solvent debinding, the green bodies exhibited noticeable surface pores, although this did not compromise density or dimensional accuracy. The sintered specimens treated with solvent debinding showed a slight increase in tetragonal phases, a significant reduction in surface roughness, and improvements in Vickers hardness and flexural strength. Cell viability tests confirmed more than 90% viability for NIH-3T3 cell lines, highlighting excellent biocompatibility. Veneers with a 0.1 mm thickness demonstrated RTP 00 values between 16.57 and 19.38, and the shade of the dental substrate notably influenced their color. The study demonstrated that the solvent debinding process effectively reduced porosity, consequently improving the mechanical properties of specimens fabricated using the 3S technique. Ultra-thin zirconia veneers produced by this method exhibited high RTP 00 values, indicating their potential suitability for anterior dental applications. Notably, the substrate shade emerged as a critical factor in achieving optimal aesthetic results. [ABSTRACT FROM AUTHOR]

(ZrO2)1 − x −y(Y2O3)x(CeO2)y (x = 0.08–0.10; y = 0.0–0.01) solid solution crystals were grown by skull melting technique. The effects of CeO2 addition on the crystal structure and high-temperature conductivity of the crystals have been investigated. According to X-ray absorption near-edge structure spectroscopy, it was found that Ce cations in crystals are present mainly as Ce4+ ions. The study of the grown crystals by X-ray diffraction, Raman spectroscopy, and transmission electron microscopy showed that all the grown crystals were single-phase and had either a tetragonal t'' or cubic structure, the latter having crystals containing 10 mol% Y2O3 and doped with CeO2. Doping of the crystals with CeO2 was accompanied by a linear increase in the lattice parameter. This indicates the entry of CeO2 into the crystal lattice with the formation of a solid solution. The study of the ionic conductivity of crystals by impedance spectroscopy in the temperature range 400–900 °C showed that the substitution of Zr4+ ions with Ce4+ ions manifests itself in different ways and can either increase or decrease the value of high-temperature conductivity depending on the content of stabilizing yttrium oxide. Possible reasons for this behavior are discussed. [ABSTRACT FROM AUTHOR]

Objectives: This RCT aimed to compare zirconia and titanium dental implants in the maxillary premolar region. The comparison was based on marginal bone level (MBL) changes, clinical parameters, aesthetic outcomes, and patient related outcome measures (PROMs) 1 year after prosthetic loading. Materials and Methods: Fifty patients were randomly assigned to receive either a zirconia (ZrO2, n = 25) implant or a titanium (Ti, n = 25) bone‐level implant. Implants were provided with a lithium disilicate crown 3 months after placement. Follow‐up was at 1 month and after 1 year. The primary outcome pertained to changes in MBL. Reported secondary outcomes consisted of implant survival, peri‐implant tissue health, aesthetics, and PROMs. Results: Mean MBL change after 1 year was 0.01 mm (SD = 0.45; min = 0.72, max = 0.86) for ZrO2 and −0.09 mm (SD = 0.34; min = 0.53, max = −1.06) for Ti (p =.439). Scores for the other clinical outcome parameters and PROMs were generally favorable, with no significant differences. However, significant differences were found for the aesthetic outcomes regarding two criteria: (a) level of facial mucosa (p =.022), in favor of Ti, and (b) root convexity/soft tissue color and texture (p =.005) in favor of ZrO2. Conclusion and clinical implications: The ZrO2 and Ti implant types used in this study, replacing a single missing maxillary premolar, show a comparable outcome in terms of MBL change after 1 year. Clinical and aesthetic parameters, as well as PROMs, are favorable and similar between both implant types after 1 year of prosthetic loading. These short‐term study results suggest that both are suitable for clinical use. [ABSTRACT FROM AUTHOR]

Diamond films were prepared on silicon nitride and zirconia ceramic substrates using hot filament chemical vapor deposition (HFCVD). The surface morphology, friction, and wear properties of the diamond films prepared with different methane concentrations (2%, 4%, and 6%) were compared using scanning electron microscopy, Raman spectroscopy, X-ray diffraction, and friction and wear testing machines. The results showed that, with an increase in the methane concentration, the diamond particles gradually changed from micro- to nanodiamonds, and the grain size first increased and then decreased. The diamond films on silicon nitride substrates were of excellent quality, with good wear resistance, strong adhesion, and wear rates of 2.857 × 10−8 mm−3•m−1•N−1, 5.151 × 10−8 mm−3•m−1•N−1, and 1.334 × 10−7 mm−3•m−1•N−1, respectively. The diamond films on zirconia substrates had more impurities on the surface, higher internal stress, poorer wear resistance, and weaker adhesion, with wear rates of 3.789 × 10−8 mm−3•m−1•N−1, 5.899 × 10−8 mm−3•m−1•N−1, and 2.074 × 10−7 mm−3•m−1•N−1, respectively. Hence, the deposition of diamond films on ceramic substrates significantly reduced the friction coefficient, and the performance of diamond films on silicon nitride substrates was excellent. [ABSTRACT FROM AUTHOR]

This in vitro study was carried out to compare the cutting efficiency of diamond grinders on zirconia and resin-based composite materials. Grinders were employed with a special holder for the handpiece to apply a constant load (160 g) for resin-based composite (8 cuts, 40 s each) and zirconia materials (4 cuts, 5 min each; n = 10 for each material and grinder). To assess the efficiency of the grinders, weight measurements of the material were taken before and after the grinding process. Scanning electron micrographs were captured for instrument surfaces before and after testing and for the resulting surface of the materials. In the resin-based composite group, there were significant differences in weight removal between the burs for both the baseline (first cut; p = 0.009) and removal after the eighth cut (p = 0.049). Statistically significant decreases in weight removal compared to the baseline values were noted for the third, fourth, sixth, and seventh steps (p ≤ 0.046). For the zirconia group, significant differences existed in weight removal between the burs for the baseline (first cut; p < 0.001) and removal after the fourth cut (p < 0.001). A significant positive correlation was observed between removal and the number of cuts (Pearson: 0.673; p < 0.001). A statistically significant decrease in removal compared to the respective baseline value was found for the fourth step (p = 0.006). The initial wear removal and durability significantly differed between the grinders used on resin-based composite and zirconia. Achieving comparable weight removal took five times longer when grinding zirconia compared to the resin-based composite. [ABSTRACT FROM AUTHOR]

This article considers the features and fundamental difficulties of studying low-temperature phase equilibria associated with an exponential increase in the required duration of syntheses with a decrease in temperature. Methods for accelerating the achievement of equilibrium, including the use of salt solvents, are also considered. The results of phase equilibria studies in the SrF2–LaF3 system using sodium nitrate and in the ZrO2–Sc2O3 system using sodium sulfate as fluxes are presented. The methods of extrapolation of phase diagrams to absolute zero temperature in accordance with the third law of thermodynamics are considered. Phase diagrams of the Au–Cu, Cu–Pd, Ni–Pt, and ZrO2–Y2O3 systems are presented. Phase equilibria with plagioclase ordering are considered separately, and the phase diagram of the albite–anorthite (NaAlSi3O8–CaAl2Si2O8) system is presented. As the temperature approaches absolute zero, the homogeneity region of labradorite shrinks to the compound NaCaAl3Si5O16. [ABSTRACT FROM AUTHOR]

To investigate the effect of the stability of oxygen vacancies on the low-temperature degradation (LTD) resistance of two kinds of commercial zirconia-based materials (3Y-TZP ceramics and Ce-TZP/Al 2 O 3 composites) via the dielectric probing methods. The commercial 3Y-TZP ceramics and Ce-TZP/Al 2 O 3 composites were prepared via conventional solid-state methods. Density, phase content, microstructure, strain, and biaxial flexural strength (BFS) of two materials were investigated using Archimedes method, XRD, SEM, strain-electric field (S-E) loops and ball-on-ring methods, respectively. The concentration of oxygen vacancies before and after LTD of two materials were evaluated using dielectric probing and XPS methods. The XRD analysis revealed that compared to the 3Y-TZP ceramics, the Ce-TZP/Al 2 O 3 composites showed better LTD resistance, without clear LTD. The greater LTD resistance for Ce-TZP/Al 2 O 3 composites was associated with their stability of oxygen vacancies, by higher activation energy based on the dielectric measurements and XPS results. For the 3Y-TZP ceramics that underwent the tetragonal to the monoclinic phase transition during the LTD treatment, the concentration of their oxygen vacancies decreased after LTD. In addition, the Ce-TZP/Al 2 O 3 composites exhibited higher flexural strength and potential fracture toughness based on the BFS testing and strain vs electric field measurement results, indicating a great potential for use in fixed restorative dental applications. This work suggested the stability of oxygen vacancies played a key role in the resistance to LTD. Optimizing the stability of the oxygen vacancies is key to the development of more reliable zirconia- based dental biomaterials with greater resistance to LTD. • LTD observed in the 3Y-TZP ceramics, accompanied with their decrease concentration of oxygen vacancies. • The stability of oxygen vacancies in the Ce-TZP/Al 2 O 3 composites played an important role in their resistance to LTD. • Dielectric probing was proved to be a useful method to investigate the LTD of zirconia bio-ceramics. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the ability of the water glass treatment to penetrate zirconia and improve the bond strength of resin cement. Material and methods: Water glass was applied to zirconia specimens, which were then sintered. The specimens were divided into water–glass-treated and untreated zirconia (control) groups. The surface properties of the water–glass-treated specimens were evaluated using surface roughness and electron probe micro-analyser (EPMA) analysis. A resin cement was used to evaluate the tensile bond strength, with2 and without a silane-containing primer. After 24 h in water storage at 37 °C and thermal cycling, the bond strengths were statistically evaluated with t-test, and the fracture surfaces were observed using SEM. Results: The water glass treatment slightly increased the surface roughness of the zirconia specimens, and the EPMA analysis detected the water glass penetration to be 50 μm below the zirconia surface. The application of primer improved the tensile bond strength in all groups. After 24 h, the water–glass-treated zirconia exhibited a tensile strength of 24.8 ± 5.5 MPa, which was significantly higher than that of the control zirconia (17.6 ± 3.5 MPa) (p < 0.05). After thermal cycling, the water–glass-treated zirconia showed significantly higher tensile strength than the control zirconia. The fracture surface morphology was mainly an adhesive pattern, whereas resin cement residue was occasionally detected on the water–glass-treated zirconia surfaces. Conclusion: The water glass treatment resulted in the formation of a stable silica phase on the zirconia surface. This process enabled silane coupling to the zirconia and improved the adhesion of the resin cement. [ABSTRACT FROM AUTHOR]

This review article focuses on recent advances in zirconia-based polymer matrix composites. Zirconia (ZrO2), as a non-black inorganic filler, has attracted a lot of attention owing to its attractive and rich materialistic properties. Considerable number of reports are documented in literature in which the effects of zirconia incorporation into polymeric matrix have been studied from different perspectives. These include studies on mechanical, thermal, dynamic mechanical, morphological, rheological, optical, electrical, and antimicrobial properties of the zirconia-filled polymer composites. In those studies, zirconia is highly recognised for its capability to improve the ultimate composite properties. In some of the studies, zirconia has been used in combination with other metal oxides to take advantage of the hybrid filler. In current report, we present an overview on zirconia-based polymer composites in context of the precise role of zirconia on the composite properties, their significance, and the outcome of the studies. Overall, zirconia appears as a potential candidate for the development of industrially important polymer composites, and ongoing work in this area is expected to bring more novel and fascinating results to further enrich this area. [ABSTRACT FROM AUTHOR]

Zirconia (ZrO 2) ceramics uniquely exhibit transformation-induced plasticity, allowing plastic deformation prior to failure, setting them apart from most other ceramics. However, our understanding of ZrO 2 plasticity is hindered by the challenge of simulating stress-induced atomic-scale phase transformations, owing to lack of an efficient interatomic potential accurately representing polymorphism and phase changes in ZrO 2. In this work, we introduce a novel deep neural network interatomic potential, DP-ZrO 2 , constructed using a concurrent-learning approach. DP-ZrO 2 reproduces properties of various ZrO 2 phases, matching their phase diagrams as well as transformation pathways with accuracy comparable to ab initio density functional theory. Leveraging DP-ZrO 2 , we conducted molecular dynamics simulations of temperature-induced interphase boundary migration and nanocompression. These simulations demonstrate the potential's efficiency and applicability in studying deformation microstructures involving phase transformations in ZrO 2. Our approach opens the door to large-scale simulations under complex loading conditions, which will shed light on the conditions favouring ZrO 2 transformation-induced plasticity. [ABSTRACT FROM AUTHOR]

Finite element analysis assists in the understanding of the biomechanical behavior of implants with different designs and material characteristics. Through this analysis, this study aimed to compare the biomechanical behaviors of different designs and configurations of titanium (tapered or cylindric) and zirconia dental implants in the edentulous anterior maxilla. Three-dimensional models of the edentulous maxilla, dental implants, and prosthetic structures were modeled, and different loading conditions were applied to simulate realistic conditions. A total of 6 different models were evaluated: the model (M1) in which tapered implants were located bilaterally in the central canine, the model (M2) in which tapered implants were located bilaterally in the lateral canine, the model (M3) in which cylindric implants were located bilaterally in the central canine, the model (M4) in which cylindric implants were located bilaterally in the lateral canine, the model (M5) in which zirconia implants were located bilaterally in the central canine, and the model (M6) in which zirconia implants were located bilaterally in the lateral canine. Maximum tensile and compressive stress values were recorded at M4 under vertical loading and at M6 under oblique loading, whereas minimum stress values were recorded at M1 under all loading conditions. Maximum von Mises stress values under vertical and oblique loading conditions were observed at M3 and M4, while the minimum stress was observed at M1 and M2. In conclusion, zirconia implants may present a biomechanically convenient and esthetic alternative treatment option in edentulous anterior maxilla rehabilitation compared with tapered and cylindric implants. [ABSTRACT FROM AUTHOR]

Background: This study aimed to investigate the (1) survival probabilities of prefabricated zirconia crowns (PZCs) placed on primary teeth and (2) identify demographic and tooth‐related factors that might affect survival probability. Methods: This study prospectively followed children treated under general anaesthesia by a single practitioner between 2012 and 2020. Demographic variables including the age at treatment, gender and tooth‐related variables including FDI tooth number, crown size used and any procedural complications at postoperative reviews were collected. Results: A total of 155 children involving 319 teeth with PZCs were followed up between 12 and 78 months postoperatively with a mean of 38 months. Of the 319 crowns followed, five failures were observed in three patients requiring extraction. Other procedural complications noted included fracture (n = 3), overhangs (n = 3), internal resorption (n = 5) and 24% of crowns showed signs of radiographic changes on postoperative radiographs when these were taken. Age at treatment, tooth type and need for pulp therapy were not statistically associated with clinical success (P > 0.1). Conclusions: PZCs provide an aesthetic and durable solution in the management of children with early childhood caries. This study shows very good clinical success and survival extending up to 78 months for PZCs placed on primary teeth under general anaesthesia. [ABSTRACT FROM AUTHOR]

Abstract—For structurally homotypical specimens different in the ZrO2 content from the (94WC–6Co) + ZrO2 matrix material used in diamond-containing Сdiamond–(WC–Co) composites formed by spark plasma sintering, the dependences of the relative density ρrel, the ultimate strength under compression Rcm and bending Rbm, the microhardness НV, and the fracture toughness KIс on the zirconia content have been established. The addition of 6 wt % zirconia to the WC–6Co composite leads to an increase in the relative density from 0.948 to 0.990, the ultimate compression strength Rcm from 4950 ± 110 to 5600 ± 120 MPa, the ultimate bending strength Rbm from 1935 ± 80 to 2660 ± 115 MPa, and the fracture toughness KIс from 13.8 ± 0.71 to 16.9 ± 0.76 MPa m0.5 at a slight decrease in hardness (from 15.9 ± 0.72 to 15.1 ± 0.33 GPa). Such values are caused by the decrease of main WC phase grains in size with tetragonal t-ZrO2 phase transformation and, correspondingly, by the growing role of transformation strengthening mechanism and the active action of inner mechanical compressive microstresses. When the ZrO2 additive to the WC–6Co composite is increased to 10%, the parameters ρrel, Rcm, Rbm, and KIс are gradually decreased. At the same time, the material at the indentor imprint edge begins to destruct, and crack propagate in a chaotic way. It has been revealed that the properties ρrel, Rcm, Rbm, and KIc are worsened at a zirconia nanopowder content above 6 wt % in the WC–Co composite due to the formation of agglomerates during the mixing of components, their separation under sintering, and the formation of micropores and microcracks. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Pd/ZrO2 and Pd/ZrO2SiO2 catalysts prepared by wet impregnation and reduced with H2 under mild (30°C, aqueous suspension) or harsh (320°C) conditions are compared in the hydrodechlorination of the microecotoxicant diclofenac (DCF) in an aqueous solution at 30°С. According to the TPR and XPS data, the addition of SiO2 to the support reduces the degree of metal-support interaction and facilitates the reduction of palladium. Despite the lower Pd0 fraction, the Pd/ZrO2 catalyst is more active in the batch reactor: after reduction at 320°С, it slightly, and after mild reduction, significantly (7 times), exceeds Pd/ZrO2SiO2 in catalytic activity. XRD and TEM show a wider size distribution of palladium nanoparticles in the Pd/ZrO2 sample, while low-temperature N2 adsorption, XPS, and TPR demonstrated better accessibility of palladium on the Pd/ZrO2 surface due to the reduced decoration by the support components and increased pore size. These features explain the increased activity of Pd/ZrO2. Testing in the flow system demonstrated higher DCF conversion in the presence of catalysts reduced at 320°C and higher stability of Pd/ZrO2SiO2 compared to Pd/ZrO2. The stability is ensured by the increased reducibility of Pd2+ with H2 and by the developed surface of Pd/ZrO2SiO2, which prevents deactivation under the action of HCl released in hydrodechlorination. [ABSTRACT FROM AUTHOR]

The application temperature and exposure time of lightweight, high performance aerogel insulation is limited by the thermal stability of the aerogel system used. Elevated temperatures cause rapid densification of the porous structures accompanied by increases in thermal conductivity and density. Previous studies have demonstrated the importance of doping concentration to thermal stability in doped metal oxide aerogel systems. The compositional route remains insufficient for stabilizing the pore structures of yttria-stabilized zirconia aerogels at elevated temperatures above 1100 °C. Non-compositionally, modifying synthetic parameters in the aerogel synthesis have been known to change the as dried pore structures. However, few studies have investigated the microstructure evolution of these pore structures under heat treatment. The current work investigates YSZ aerogels prepared via a sol-gel method at 30 mol% YO1.5, varying solids loadings and water contents. The results inform the ways in which the aerogel pore structure at high temperatures is sensitive and insensitive to the variation in synthetic parameters. An improved understanding of the relationships between synthetic parameters, as dried structure, and thermal stability will inform future efforts in the design and synthesis of aerogels with thermal stability in extreme environments. Highlights: Synthetic parameters of solids loading and water content modify the pore structure of YSZ aerogels. Microstructural evolution of a full factorial set of aerogels is characterized to 1200 °C. Higher specific surface areas contribute to significantly greater densification to 1000 °C. The change in densification with synthetic parameters is small compared to change with composition. [ABSTRACT FROM AUTHOR]

Zirconia is a ceramic material having a wide range of applications in industries owing to its excellent properties like high strength-to-weight ratio, biocompatibility, insulating, high wear, thermal resistance, and chemical stability over conventional materials. These properties pose a significant challenge for machining at the micro-level with considerable accuracy and preciseness. The ECDM is a low-cost hybrid machining technique with great potential to machine such materials. Barely any simulated or numerical work has been available for machining zirconia material through the ECDM process. In this study, a finite element model (FEM) is developed to predict the material removal rate (MRR) of the zirconia material using the temperature distribution plots through the electrochemical discharge machining process (ECDM) for different parametric conditions using a single spark mechanism. The simulation results reveal the increase of 316.9 µg in MRR by increasing electrolytic concentration from 15% to 30% wt. However, a small error was found between simulated and experimental results, which might be due to the assumptions during the study. This study will provide new guidelines during the processing of zirconia material for predicting the material removal rate for future manufacturing engineers. [ABSTRACT FROM AUTHOR]

The insulating ceramic materials owning to their properties are being useful in modern industrial applications. The same desirable properties make the processing of ceramics difficult by the conventional techniques. The wire electrical discharge machining (WEDM) is well known for its three-dimensional intricate shape generation capability in hard materials. Applying the WEDM to process insulating ceramic materials require electrical conductivity to establish the initial electric contact. This can be provided by covering the insulating ceramic surface with electrically conductive assisting electrode (AE) material. The present study applies the AE technology to machine yttria-stabilized zirconia ceramic with graphite powder additive mixed distilled water. The study verifies the feasibility of applying WEDM to cut the insulating ceramic materials successfully. The secondary electroconductive layer generation on the insulating ceramic surface to maintain the electrical contact on exposure of ceramic is also supported by the composition analysis of the ceramic surface. With the replacement of the kerosene dielectric, this paper highlights the use of distilled water offering a sustainable approach. The sustainability index obtained for graphite additive mixed dielectric is 78.0 compared with 50.33 of EDM oil and 48.67 of kerosene dielectric. [ABSTRACT FROM AUTHOR]

Background: The advent of three-dimensional (3D) printing technology has revolutionized the field of dentistry, enabling the precise fabrication of dental implants. By utilizing 3D printing, dentists can devise implant plans prior to surgery and accurately translate them into clinical procedures, thereby eliminating the need for multiple surgical procedures, reducing surgical discomfort, and enhancing surgical efficiency. Furthermore, the utilization of digital 3D-printed implant guides facilitates immediate restoration by precisely translating preoperative implant design plans, enabling the preparation of temporary restorations preoperatively. Methods: This comprehensive study aimed to assess the postoperative oral health status of patients receiving personalized 3D-printed implants and investigate the advantages and disadvantages between the 3D-printed implant and conventional protocol. Additionally, variance analysis was employed to delve into the correlation between periodontal status and overall oral health. Comparisons of continuous paired parameters were made by t-test. Results: The results of our study indicate a commendable one-year survival rate of over 94% for 3D-printed implants. This finding was corroborated by periodontal examinations and follow-up surveys using the Oral Health Impact Profile-14 (OHIP-14) questionnaire, revealing excellent postoperative oral health status among patients. Notably, OHIP-14 scores were significantly higher in patients with suboptimal periodontal health, suggesting a strong link between periodontal health and overall oral well-being. Moreover, we found that the operating time (14.41 ± 4.64 min) was less statistically significant than for the control group (31.76 ± 6.83 min). Conclusion: In conclusion, personalized 3D-printed implant surgery has emerged as a reliable clinical option, offering a viable alternative to traditional implant methods. However, it is imperative to gather further evidence-based medical support through extended follow-up studies to validate its long-term efficacy and safety. [ABSTRACT FROM AUTHOR]

Copyright of West China Journal of Stomatology is the property of Sichuan University, West China College of Stomatology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of West China Journal of Stomatology is the property of Sichuan University, West China College of Stomatology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Retrieval of cement-retained implant-supported restorations is intriguing in cases of screw loosening. Detecting the estimated size of the screw access hole (SAH) could decrease destruction to the prosthesis and preserve the crown. Objectives: To precisely localize loose implant screws through cemented crowns to reduce crown damage after screw loosening. Materials and methods: In this in vitro study, 60 cement-retained implants supported 30 zirconia-based, and 30 ceramics fused to metal (CFM) lower molar crowns were invented, and each was subdivided into three subgroups (10 each). In group I (AI/BI) (control), SAH was created with the aid of orthopantomography (OPG). In contrast, in group II (zirconia-crown), SAH was created with the aid of CBCT + 3D printed surgical guide with a 2 mm metal sleeve in subgroups IIA/IIIA and CBCT + MAR was used to develop SAH in subgroups IIB/IIIB. SEM and Micro-CT scanned the SAH openings to determine the diameter of the hole, cracking, chipping, and chipping volume. Results: Regarding the effect of plane CBCT and CBCT + MAR on prepared crowns, a highly significant association between group I with group II (p = 0.001) and group III (p = 0.002) was detected. Regarding the cracking of SAH, significant differences between the zirconium crown and CFM restoration (p = 0.009) were found, while for the chipping, no significant association was seen between groups (p = 0.19). Conclusions: CBCT, either as a plane CBCT or with MAR, significantly improved the accuracy of drilling the screw channel and decreased injury to the existing restoration and abutment, aiding in better localization of SAH in loosened implant abutment screws. [ABSTRACT FROM AUTHOR]

Cutlery and flatware designs are an everchanging phenomenon of the manufacturing industry. Worldwide hospitality businesses demand perpetual evolution in terms of aesthetics, designs, patterns, colours, and materials due to customers' demands, modernisation, and fierce competition. To thrive in this competitive market, modern fabrication techniques must be flexible, adoptive, fast, and cost effective. For decades, static designs and trademark patterns were achieved through moulds, limiting production to a single cutlery type per mould. However, with the advent of laser engraving and design systems, the whole business of cutlery production has been revolutionised. This study explores the possibility of creating diverse designs for stainless steel 304 flatware sets without changing the entire production process. The research analyses three key laser process parameters, power, scanning speed, and number of passes, and their impacts on the resulting geometry, depth of cut, surface roughness, and material removed. These parameters are comprehensively studied and analysed for steel and zirconia ceramic. The study details the effects of power, scanning speed, number of passages, and fluence on engraved geometry. Fluence (power*number of passages/scanning speed) positively influences outputs and presents a positive trend. Medium power settings and higher scanning speeds with the maximum number of passages produce high-quality, low-roughness optimised cavities with the ideal geometric accuracy for both materials. [ABSTRACT FROM AUTHOR]

Hf0.5Zr0.5O2-based materials have garnered significant attention for applications requiring ferroelectricity at the nanoscale. This behavior arises due to the stabilization of metastable phases at room temperature. However, the synthesis of phase pure Hf0.5Zr0.5O2 remains a challenging problem in both thin films and nanoparticles. Herein, the crystallization of Hf0.5Zr0.5O2 nanoparticles from an as-synthesized amorphous phase is studied. By tailoring the aggregate nature of the intermediate amorphous nanoparticles via different drying processes, the crystallization pathway can be altered, resulting in significant differences in crystal structure, crystallite size, and crystallite morphology after calcination. X-ray diffraction (XRD) and Rietveld refinement show the dominant crystallographic phase changes from a monoclinic structure to a cubic structure for samples with decreased aggregation. Samples prepared via freeze drying exhibit the most aggregation control and correspond with the observation of singlecrystalline particle aggregates and branching structures attributed to a crystallization by particle attachment mechanism. Herein, differing crystallization pathways lead to unique crystal morphologies that stabilize the traditionally high-temperature phases of Hf0.5Zr0.5O2-based materials that are necessary for functional applications. [ABSTRACT FROM AUTHOR]

Osteogenic differentiation and bone regeneration can be effectively aided by porous scaffolds with multiscale cellular structures, making it easier to repair defects in bone tissue. Due to the scarcity of pore-forming agents, it is extremely challenging to fabricate interconnected hierarchically porous zirconia at multi-scale. This work described a novel and straightforward method for directly imprinting a slurry containing two pore-forming agents (microspherical and filamentary) to produce strong and highly porous zirconia (ZrO 2) ceramics with four levels of porosity ranging from nanometers to millimeters. The concentration of hemp fibers significantly affected printability when the rheological behavior of a zirconia slurry was examined. Utilizing a scanning electron microscope (SEM) to monitor the development of powder interstices under various sintering techniques. The permeability performance was assessed when simulated plasma had fully filled the scaffolds. The structure had a high compressive strength of 24.18 MPa, a porosity of 80.9 %, an apparent porosity of 55.7 %, and took just 1.11 s to fill a scaffold that was 15 mm high. It is anticipated that the proposed route will be expanded to include various engineering materials for structural and practical applications. [ABSTRACT FROM AUTHOR]

The marginal accuracy of fit between prosthetic restorations and abutment teeth represents an essential aspect with regard to long-term clinical success. Since the final gap is also influenced by the luting techniques and materials applied, this study analyzed the accuracy of the fit of single-tooth zirconia copings before and after cementation using different luting materials. Forty plaster dies with a corresponding zirconia coping were manufactured based on a single tooth chamfer preparation. The copings were luted on the plaster dies (n = 10 per luting material) with a zinc phosphate (A), glass–ionomer (B), self-adhesive resin (C), or resin-modified glass–ionomer cement (D). The accuracy of fit for each coping was assessed using a non-destructive digital method. Intragroup statistical analysis was conducted using Wilcoxon signed rank tests and intergroup analysis by Kruskal–Wallis and Mann–Whitney U tests (α = 0.05). Accuracy of fit was significantly different before/after cementation within A (0.033/0.110 µm) and B (0.035/0.118 µm; p = 0.002). A had a significantly increased marginal gap compared to C and D, and B compared to C and D (p ≤ 0.001). Significantly increased vertical discrepancies between A and B versus C and D (p < 0.001) were assessed. Of the materials under investigation, the zinc phosphate cement led to increased vertical marginal discrepancies, whereas the self-adhesive resin cement did not influence the restoration fit. [ABSTRACT FROM AUTHOR]

The aim of this paper was to evaluate the fracture resistance of 3D-printed zirconia occlusal veneers (OVs) of different thicknesses and supported by different abutment materials. Materials and Methods: The standard OV of a natural molar was prepared and digitized using a laboratory 3D scanner. The resulting digital tooth abutment was milled either using cobalt–chromium (CoCr) or a fiber-reinforced composite (FRC). All the abutments were digitized and standardized OVs (30° tilt of all the cusps) designed with 0.4 mm, 0.6 mm, or 0.8 mm wall thicknesses. The OVs were fabricated using either the Programill PM7 milling device (Ivoclar Vivadent, PM) or one of two 3D zirconia printers, Cerafab 7500 (Lithoz, LC) or Zipro-D (AON, ZD). The ZD samples were only tested on CoCr abutments. The completed OVs were luted to their abutments and subjected to artificial aging, consisting of thermocycling and chewing simulation before fracture testing with a steel sphere (d = 8 mm) as an antagonist with three contact points on the occlusal OV surface. Besides the total fracture resistance Fu,tot, the lowest contact force Fu,cont leading to the local fracture of a cusp was of interest. The possible effects of the factors fabrication approach, wall thickness, and abutment material were evaluated using ANOVA (α = 0.05; SPSS Ver.28). Results: The total fracture resistance/contact forces leading to failure ranged from Fu,tot = 416 ± 83 N/Fu,cont = 140 ± 22 N for the 0.4 mm OVs fabricated using LC placed on the FRC abutments to Fu,tot = 3309 ± 394 N (ZD)/Fu,cont = 1206 ± 184 N (PM) for the 0.8 mm thick OVs on the CoCr abutments. All the factors (the fabrication approach, abutment material, and OV wall thickness) had an independent effect on Fu,tot as well as Fu,cont (p < 0.032). In pairwise comparisons for Fu,tot of the OVs luted to the CoCr abutments, the ZD samples statistically outperformed the LC- and PM-fabricated teeth irrespective of the thickness (p < 0.001). Conclusions: Within the limitations of this study, the printed occlusal veneers exhibited comparable fracture resistances to those of the milled variants. However, more resilient abutments (FRC as a simulation of dentine) as well as a thinner wall thickness led to reduced OV fracture resistance, suggesting that 0.4 mm thick zirconia OVs should not be unreservedly used in every clinical situation. [ABSTRACT FROM AUTHOR]

The grain growth behavior during an AC flash event was examined in 8 mol% yttria‐stabilized cubic zirconia (8Y‐CSZ) polycrystals. The effects of current/power densities on the grain growth behavior were investigated in 8Y‐CSZ samples with different specific surface areas at a constant sample temperature and applied field strength. The grain growth rate of flash‐treated 8Y‐CSZ was 300 times faster than that of heat‐treated 8Y‐CSZ at the same sample temperature in the absence of an electric current/field, suggesting that the promoted grain growth cannot be ascribed only to a thermal effect but also to an athermal effect occurring during the AC flash event. Moreover, the grain growth during the flash treatment strongly depends on the applied current/power densities and grain size; in particular, the grain growth showed enhancements with increasing applied current/power densities and for relatively small grain sizes. This result suggests that the grain boundary diffusivity of cations, which are regarded as the rate‐controlling species for grain growth, could be accelerated by tuning the current/power densities during the flash event. The grain growth mechanism was characterized using a grain growth exponent (n) value of 4.8 for the flash treatment at high current/power densities and using a conventional value of n = 3 under normal heat treatment conditions. The dependence of the grain growth behavior on the AC current/power density suggests that because the cation diffusivity is accelerated due to the formation of numerous point defects during the AC flash event, the grain growth mechanism might depend on the current/power densities and differ from that of conventional grain growth. [ABSTRACT FROM AUTHOR]

Recently, CaO‐doped (≤4 mol.%) tetragonal zirconia (CaSZ) ceramic was recommended as a potential alternative to yttria‐stabilized ZrO2 (YSZ). Here, we investigate the limits of starting particle sizes on the stability of tetragonal (t) phase and other associated benefits on measured properties. Synthesized CaSZ powders calcined with different temperatures were used as a mono‐sized or mixed (i.e., two different calcination temperatures) batch fraction for making dense CaSZ ceramic. The mixed‐batch powders were found to be far more efficient in stabilizing the t‐phase in ceramic. Compared to YSZ, CaSZ recorded remarkable enhancement in toughness (up to 8.3 MPa m$\sqrt {\mathrm{m}} $). Contrary to YSZ, CaSZ ceramic demonstrated outstanding thermal stability. [ABSTRACT FROM AUTHOR]

This 3D finite element analysis study aimed to investigate the effect of reinforcing CAD-CAM bars on stress distribution in various components of a posterior composite bridge. A virtual model mimicking the absence of an upper second premolar was created, featuring class II cavity preparations on the proximal surfaces of the adjacent abutment teeth surrounding the edentulous space. Five distinct finite element analysis (FEA) models were generated, each representing a CAD-CAM reinforcing bar material: 3-YTZP (IPS. emax ZirCAD MO; Zr), lithium disilicate (IPS e.max CAD; EX), nano-hybrid resin composite (Grandio Blocs; GB), Fibre-reinforced composite (Trilor; Tri), and polyetheretherketone (PEEK). A veneering resin composite was employed to simulate the replacement of the missing premolar (pontic). In the FEA, an axial force of 600 N and a transverse load of 20 N were applied at the center of the pontic. Subsequently, maximum von Mises (mvM) and maximum principal stresses (σmax) were computed across various components of the generated models. Additionally, shear stresses at the interface between the CAD-CAM bars and the veneering resin composite were determined. CAD-CAM materials with high modulus of elasticity, such as Zr and EX, exhibited the highest mvM stresses and shear stresses while transferring the lowest stress to the veneering resin composite in comparison to other materials. Conversely, PEEK demonstrated the lowest mvM stresses but produced the highest stresses within the veneering resin composite. There was a uniform distribution of mvM stresses in the remaining tooth structure among all groups, except for a noticeable elevation in the molar region of Zr and EX groups. Reinforcing CAD-CAM bar materials with a high modulus of elasticity, such as Zr and EX, may result in debonding failures at the connector sites of posterior composite bridges. Conversely, GB, PEEK, and Tri have the potential to cause fracture failures at the connectors rather than debonding. [ABSTRACT FROM AUTHOR]