This study aimed to evaluate the flexural strength (FS), surface wear, and optical properties of 3D-printed dental resins subjected to different post-printing conditions. A total of 240 specimens (2 × 2 × 25 mm³) were 3D-printed using resin materials for permanent (VaresoSmile Crown Plus) VSC and temporary (VaresoSmile Temp) VST restorations. Specimens underwent five post-printing conditions: no post-printing cure; post-cured in a Form Cure curing unit; Visio Beta Vacuum; Ivoclar Targis; or heat-cured (150 °C) for 30 min. Each group of specimens (n = 24) was tested either directly after post-curing, after 24 h of dry storage, or following hydrothermal accelerated aging in boiling water for 16 h. The three-point bending test was used to evaluate the FS. The two-body wear test was performed on 50 disc-shaped specimens (n = 5/group). Surface gloss and translucency were measured for permanent VSC specimens (n = 5/group). SEM/EDS and statistical analyses were performed. The Form Cure device yielded the highest FS and lowest wear depth (p < 0.05). Hydrothermal aging significantly reduced FS. There were no statistical differences in FS and wear values between materials subjected to same post-printing conditions. VSC groups exhibited similar optical properties across different post-printing treatments. Post-printing treatment conditions had a significant impact on the FS and wear of the 3D-printed resin, while optical properties remained unaffected.

Wire rope has different degrees of surface wear under long-distance transmission conditions, which leads to performance degradation and greatly threatens its safety and reliability in service. In this paper, friction and wear tests between the transmission wire rope and sheave under different sliding velocities (from 0.8 m/s to 1.6 m/s) were carried out using a homemade test rig. The material of the steel wires was low carbon steel, and pulley material was ASTM A36 steel plate. The sliding friction coefficient (COF), friction temperature rise, wear characteristic parameters and wear mechanisms of the wire rope were analyzed. Additionally, the effect of different wear on the fracture behavior of the wire rope was investigated by a breaking tensile test. The results show that the average COF in the relatively stable stage decreased from approximately 0.58 to 0.51 with the increase of sliding velocity. The temperature rise of the wire rope increased rapidly with an increase of sliding velocity, from approximately 52.7 °C to 116.2 °C. The maximum wear width was the smallest when the sliding velocity was 1.2 m/s (approximately 1.5 mm). The surface wear was characterized by spalling, furrowing and plastic deformation, which are strongly affected by the sliding velocity. The wear mechanisms of the wire rope were mainly adhesive wear and abrasive wear. Surface wear changes the fracture morphology of the wire rope and accelerates its fracture speed.

The aim of this in vitro study was to analyse the performance of CAD/CAM resin-based composites for the fabrication of long-term temporary fixed dental prostheses (FDP) and to compare it to other commercially available alternative materials regarding its long-term stability. Four CAD/CAM materials [Structur CAD (SC), VITA CAD-Temp (CT), Grandio disc (GD), and Lava Esthetic (LE)] and two direct RBCs [(Structur 3 (S3) and LuxaCrown (LC)] were used to fabricate three-unit FDPs. 10/20 FDPs were subjected to thermal cycling and mechanical loading by chewing simulation and 10/20 FDPs were stored in distilled water. Two FDPs of each material were forwarded to additional image diagnostics prior and after chewing simulation. Fracture loads were measured and data were statistically analysed. SC is suitable for use as a long-term temporary (two years) three-unit FDP. In comparison to CT, SC featured significantly higher breaking forces (SC > 800 N; CT < 600 N) and the surface wear of the antagonists was (significantly) lower and the abrasion of the FDP was similar. The high breaking forces (1100-1327 N) of GD and the small difference compared to LE regarding flexural strength showed that the material might be used for the fabrication of three-unit FDPs. With the exception of S3, all analysed direct or indirect materials are suitable for the fabrication of temporary FDPs.

Titanium is considered to be a metal material with the best biological safety. Studies have proved that the titanium implanted in the bone continuously releases titanium particles (Ti particles), significantly increasing the total titanium content in human body. Generally, Ti particles are released slowly without causing a systemic immune response. However, the continuous increased local concentration may result in damage to the intraepithelial homeostasis, aggravation of inflammatory reaction in the surrounding tissues, bone resorption and implant detachment. They also migrate with blood flow and aggregate in the distal organ. The release of Ti particles is affected by the score of the implant surface structure, microenvironment wear and corrosion, medical operation wear, and so on, but the specific mechanism is not clear. Thus, it difficult to prevent the release completely. This paper reviews the causes of the Ti particles formation, the damage to the surrounding tissue, and its mechanism, in particular, methods for reducing the release and toxicity of the Ti particles.

OBJECTIVE: Ionizing radiation therapy (RT) is the main option for head and neck cancer treatment, but it is associated with multiple side effects. This study aimed to evaluate the effect of RT associated with chewing simulation on the surface of human enamel and Yttria-partially stabilized zirconia (Y-TZP).
METHODS: Maxillary premolar cusps and Y-TZP slabs were divided in 7 experimental groups: CO: no RT (control); EZ groups had irradiation applied to both, enamel and zirconia samples (simulating restoration prior to RT); E groups had irradiation applied to enamel only (simulating restoration after RT). RT doses were either 30, 50 or 70 Gray (Gy). Enamel cusps were abraded against zirconia slabs in a chewing simulator (CS - one million cycles/ 80 N/ 60 mm/min, 2 mm horizontal path, artificial saliva, 37˚ C). Zirconia hardness was evaluated before CS; zirconia roughness and enamel volume (wear) were evaluated before and after CS. Hardness and wear data were analyzed by one-way Analysis of Variance and Tukey post hoc test. Roughness was analyzed by Repeated Measures test and Bonferroni test (p=0.05).
RESULTS: There was no significant effect of enamel or zirconia irradiation on enamel cusp wear (p=0.226), regardless of the irradiation dose used - up to 70 Gy. Irradiation also did not affect Y-TZP surface roughness (p=0.127) and hardness (p=0.964).
CONCLUSIONS: RT does not promote significant changes to the surface characteristics of zirconia. Irradiated enamel abraded against zirconia does not show higher wear volume when compared to non-irradiated enamel.

The article assesses the strength and structural parameters of load-bearing layers of metal biobearings made of CoCrMo alloy. The research material consisted of unicompartmental knee joint endoprostheses used in the human body, removed due to excessive wear. No patient participated in the examinations. The endoprostheses used as research material underwent the liquidation procedures in the hospital, which has all necessary permissions and certifications to perform endoprosthetic procedures. Endoprostheses selected for the examinations had been used for 6 to 12 years at similar load conditions as declared by the patients, i.e., body weight of F = 835 N, declared activity expressed as the number of load cycles up to 100 thousand/year, and no artificial joint infections. To assess the homogeneity of the research material, the analysis of chemical composition using a Joel scanning electron microscope with EDS (Energy-dispersive X-ray spectroscopy) was made to exclude endoprostheses with various alloying additives. Microscopic examinations were performed using the Phenom XL microscope, while the wear surface was examined using a Keyence VHX-900F microscope. Several experimental tests were also carried out on load-bearing surfaces to assess changes in strength parameters of the base material after a known life cycle and load conditions. Material hardness using the Vickers method, yield point, critical value of stress intensity coefficient, and the coefficient of friction µ were evaluated. The examinations allowed for the systematization of wear in the knee and femoral components of unicompartmental hip endoprostheses. The statistical evaluation of the number and costs of hip joint replacement surgeries in Poland was also made.

OBJECTIVE: To compare in vitro fracture load, surface wear, and roughness after thermal cycling and cyclic mechanical fatigue loading among cemented microhybrid resin-based composite and ceramic occlusal veneers fabricated at two thicknesses (1.5 and 2.5 mm).
METHODS: Sixty-four extracted premolars without root canal treatment were prepared and restored with occlusal veneers of two thicknesses (1.5 and 2.5 mm), using four different materials: microhybrid composite (MC), fiber-reinforced microhybrid composite (FMC), heat-pressed lithium disilicate ceramic (HPC), and computer-aided design/computer-aided manufactured lithium disilicate ceramic (CCC). The specimens underwent thermal cycling and cyclic mechanical fatigue loading, and were then subjected to fracture testing, with loads at failure recorded as fracture load. Wear and surface roughness were recorded before and after fatigue loading. Results were analyzed using one-way ANOVA, two-way ANOVA (α = 0.05).
RESULTS: All specimens survived thermal cycling and cyclic mechanical fatigue loading. At 1.5-mm thickness, the mean fracture load of FMC was highest (3926.48 ± 556.54 N), while that of CCC was highest (3066.45 ± 559.94 N) at 2.5 mm. Regardless of thickness, the fracture load of CCC was higher than that of HPC (p = 0.004 and p = 0.023). The wear of MC and FMC was significantly higher than those of HPC and CCC (p ≤ 0.001), but was similar in terms of the wear rate of tooth enamel. HPC exhibited the lowest surface roughness after fatigue loading (p ≤ 0.001).
CONCLUSIONS: All tested occlusal veneers exhibited a fracture load considerably exceeding the maximum occlusal force in the posterior dentition. When the attainable space for restoration varies, different occlusal veneer materials should be considered. The surface wear and roughness also need to be considered when selecting materials.

This in vitro study assessed morphological changes and efficiency of reciprocating files after multiple uses. Sixty standardized Endo Training Blocks and 10 ReciprocR25 files were selected (six blocks for each file). Each file was its own control (before use vs. after each instrumentation). The instruments were used according to the manufacturer\'s instructions, and scanning electron microscopy was used to observe fatigue cracks, metal strips/metal flash, pitting, fretting, debris, disruption of the cutting edge, and plastic deformations after each instrumentation. The presence of seven wear variables was scored semiquantitatively by viewing micrographs collected before and after use. The prepared areas in resin blocks were calculated and compared by using AutoCAD software. The control group had significantly lower values for all wear variables except fretting and plastic deformation. The presence of fatigue cracks and metal strips/metal flash significantly differed between unused instruments and instruments used four or five times, in all observed sections. The area of instrumented Endo Training Blocks significantly differed in relation to the number of instrument uses. The Reciproc files wore progressively, and repeated use affected their shaping efficiency in simulated canals.

Orthodontic treatments with Invisalign® require the use of attachments, which are composite resin buttons attached to tooth surfaces. Attachments constitute one of the most powerful tools for improving the efficiency of orthodontic tooth movement. The main purpose of this study was to evaluate surface wear over six months in two resin composites (Filtek Z350 XT, 3MESPE and Amelogen Plus TW, Ultradent Products Inc. ) used for making Invisalign® attachments. These composites were selected for their esthetic and mechanical properties. Forty attachments were bonded to the buccal surface of maxillary teeth. Materials were randomized and assigned in a double blind manner. Impressions were taken of the attachments using a preestablished technique immediately after bonding and following 6 months of clinical use. The impressions were examined by Scanning Electron Microscopy (SEM) at 12-fold magnification to identify changes in surface texture and attachment shape. Data were analyzed using Mann-Whitney\'s test on the overall ranking of detected changes in those variables. Statistically significant differences (P<0. 001) were found for surface wear, with greater changes in Amelogen Plus. Attachment shape did not change significantly in either material (P>0. 05). According to the results of this study, the alteration of the attachment surface during the first six months of treatment depends on the composite used, while attachment shape does not appear to be affected, so the clinical performance of the materials evaluated could be considered acceptable.
Los tratamientos ortodóncicos con alineadores Invisalign® utilizan aditamentos construidos en resinas compuestas llamados \"attachments\" adheridos a la superficie dentaria. El \"attachment\" es una de las herramientas más potentes para mejorar la eficiencia del movimiento dental. El propósito de este estudio fue evaluar el desgaste superficial de dos resinas compuestas utilizadas para construir los \"attachments\" en el tratamiento de ortodoncia con la técnica de alineadores Invisalign®. Se evaluaron 40 \"attachments\" adheridos a la superficie vestibular de piezas dentarias del maxilar superior en un período de 6 meses. Los \"attachments\" fueron construidos en forma aleatoria y a doble ciego con dos resinas compuestas (Filtek Z350 XT de 3M ESPE y Amelogen Plus TW Ultradent Products Inc) elegidas de acuerdo con las propiedades estéticas y mecánicas requeridas. Los \"attachments\" fueron impresionados con una técnica preestablecida inmediatamente luego de ser adheridos y a los 6 meses. Las muestras fueron preparadas para su observación mediante Microscopía Electrónica de Barrido (MEB) a 12 aumentos. Se observaron los cambios producidos en la textura superficial y la forma entre el inicio y los seis meses de tratamiento. Los datos fueron analizados y comparados utilizando la prueba de Mann-Whitney, realizada en función del ordenamiento global, de menor a mayor según el cambio producido en esas variables. Los materiales analizados mostraron una diferencia estadísticamente significativa (P<0, 001) en el desgaste superficial, siendo el Amelogen Plus el material que evidenció mayor cambio. Las modificaciones en la forma de los \"attachments\" no fueron estadísticamente significativas en ambos materiales (P>0, 05). Según los resultados obtenidos en este estudio, la modificación de la superficie de los \"attachments\" durante los primeros seis meses de tratamiento varía en función del composite empleado, en tanto la forma del \"attachment\" no parece ser afectada de manera similar, por lo que el desempeno clínico podría ser considerado aceptable cuando se emplean los materiales evaluados.

Hip resurfacing offers advantages for young, active patients afflicted with hip osteoarthritis and may also be a beneficial treatment for adult canines. Conventional hip resurfacing uses metal-on-metal bearings to preserve bone stock, but it may be feasible to use metal-on-polyethylene bearings to reduce metal wear debris while still preserving bone. This study characterized the short-term wear behavior of a novel hip resurfacing implant for canines that uses a 1.5 mm thick liner of highly cross-linked polyethylene in the acetabular component. This implant was tested in an orbital bearing machine that simulated canine gait for 1.1 million cycles. Wear of the liner was evaluated using gravimetric analysis and by measuring wear depth with an optical scanner. The liners had a steady-state mass wear rate of 0.99 ± 0.17 mg per million cycles and an average wear depth in the central liner region of 0.028 mm. No liners, shells, or femoral heads had any catastrophic failure due to yielding or fracture. These results suggest that the thin liners will not prematurely crack after implantation in canines. This is the first hip resurfacing device developed for canines, and this study is the first to characterize the in vitro wear of highly cross-linked polyethylene liners in a hip resurfacing implant. The canine implant developed in this study may be an attractive treatment option for canines afflicted with hip osteoarthritis, and since canines are the preferred animal model for human hip replacement, this implant can support the development of metal-on-polyethylene hip resurfacing technology for human patients. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1196-1205, 2018.