Manufacture Of Dental Prostheses Research Articles

Перспективы применения принтованных временных ортопедических конструкций при длительной эксплуатации

The non-removable temporary structures are used in orthopedic dentistry to provide high-quality treatment. The approaches in prosthetics are conditionally divided into conventional and digital. These approaches imply the use of both common materials for prosthetics and unique options. When the conventional approach is used, the quality of orthopedic dental treatment depends on the manual skill of the provider (dental technician). Unlike the conventional approach, the digital one uses a wide range of libraries with ready-made templates for various options for the dentoalveolar system aesthetic and functional characteristics. This fact allows the attending physician to do without any intermediary for the manufacture of dental prostheses, if the material and technical resources permit. The use of 3D printing in dentistry has only recently begun. From our point of view, the active use of photopolymer 3D resins can become a promising option in terms of economic and strength characteristics.

The Evaluation of the Trueness of Dental Mastercasts Obtained through Different 3D Printing Technologies.

In contemporary dentistry, several 3D printing techniques, including a stereolithography apparatus (SLA), digital light processing (DLP), liquid crystal display (LCD), and PolyJet 3D inkjet printing technology (PolyJet), are employed for model production. Despite their widespread use, there remains a paucity of the literature regarding the trueness and precision of these devices in dental applications. Existing studies comparing the accuracy of dental models manufactured by different printing technologies yield disparate conclusions regarding dental prosthesis manufacturing. This study aimed to test two null hypotheses: first, that the trueness of various new-generation 3D printers is equivalent, and second, that the trueness of printing by these printers is sufficient for achieving high-precision mastercasts in dental prosthodontics manufacturing. The research focuses on evaluating the trueness of five contemporary dental 3D printers: Anycubic Mono X 6Ks (Hongkong Anycubic Technology Co., Hongkong, China), Asiga Max (Asiga, Sydney, Australia), Creo C5 (Planmeca Oy, Helsinki, Finland), Form 3B (Formlabs, Boston, MA, USA), and J5 Dentajet (Stratasys Ltd., Eden Prairie, MN, USA). The methodology employed involved the creation of a digital test object using Blender software, adhering meticulously to the dimensions outlined in ISO standard 20896-1. These dimensions were chosen to be both relevant for this study and representative of clinical scenarios. Subsequently, the test object was printed and precise measurements were conducted utilizing a metrology-type Nikon XTH225 ST Reflection target in conjunction with VGStudio MAX analysis software. The results of our investigation revealed clinically negligible deviations in ball dimensions across all printers, with the maximum observed deviations ranging between 1.17% and 2.03% (notably observed in the Creo C5 printer). Transversal distortion exhibited variance based on the linear accuracy of each printer, with Stratasys21 and Formlabs 3B demonstrating superior accuracy among the evaluated printers. Distortions in the analyzed dimensions (specifically, anterior b-c, posterior a-d, and oblique a-c) were found to be uniform. In conclusion, while the first null hypothesis was rejected, indicating variations in trueness among the 3D printers assessed, our findings affirm the suitability of all five analyzed 3D printers for clinical applications. Consequently, these printers can be utilized for the fabrication of high-precision mastercasts in dental prosthodontics manufacturing.

Synthesis of Nickel-Based Medical Alloys via Mechanochemical Processing and Powder Metallurgy Techniques

In this study, medical nickel alloys suitable for dental applications were synthesised by a combination of force chemical synthesis and powder metallurgy. Titanium and base powders were used, processed in a hydrogen atmosphere to obtain sub-micron particle sizes and homogeneously mixed by mechanical alloying techniques to optimise sintering and compaction properties. This method ensures perfect consistency of particle composition and morphology, essential for the subsequent sintering process, which densifies the material to a relative density of 98.96% while maintaining the precise shape and weight specifications required. Manganese, boron and cerium are added in moderate amounts to enhance bond strength with porcelain veneers without sacrificing corrosion resistance or causing discolouration. Boron content is controlled below 0.1 weight percent to reduce brittleness, and silicon is adjusted to maintain mechanical strength. The alloy's coefficient of thermal expansion is optimised and determined by dilatometry techniques to ensure compatibility with porcelain and compliance with industry standards for nickel-based dental alloys. Tested mechanical properties including yield strength, tensile strength and Vickers hardness showed robustness and resistance that surpassed most nickel-based alloys and competed with cobalt-based alternatives. The study concluded that the advanced synthesis technology used to produce the nickelcontaining medical alloy has improved mechanical, thermal and aesthetic properties, making it ideal for the manufacture of dental prostheses that require high precision.

Bibliographic review on acrylic materials modified with nanoparticles for the development of dental prostheses

Nanoparticles used in the making of dental prostheses reduce the microbial load in the oral cavity. The aim of the study was to interpret acrylic materials modified with nanoparticles for the development of dental prostheses with a view to describing their antimicrobial properties against Candida Albicans. An exhaustive bibliographic review of scientific articles selected through databases such as PubMed, Elsevier, Science Direct, and SciELO was developed, using MeSH terms in both English and Spanish. The literature selection was guided by the PRISMA methodology. The results of this study demonstrate the positive impact of nanoparticles in the field of dentistry, especially in the manufacturing of dental prostheses. It has been shown that acrylics modified with nanoparticles offer effective antimicrobial properties against pathogens such as Candida Albicans, in addition to presenting greater biocompatibility with oral tissues. Likewise, these nanoparticle-enriched prostheses stand out for their improved resistance to wear and greater hardness, compared to conventional prostheses. The main conclusion of the study highlights the relevance of nanotechnology as a revolutionary tool in improving the materials used in dentistry, particularly in dental prostheses. The incorporation of nanoparticles into the acrylics not only enhances the antimicrobial properties and biocompatibility of these prostheses but also significantly improves their durability and resistance. These advances represent a significant step towards the development of more effective and safer solutions for patients

3Y-TZP electrostatic painting to increase bond strength to dentin and dental prostheses

Although the clinical method used to improve the adhesion of zirconia prostheses to other materials is sandblasting or acid etching surface, the failure rate of the bond is high. The present work aims to propose an innovative method of zirconia surface painting with an electrostatic technique using epoxy powder paint with antibacterial and antifungal properties to improve the adhesion to dentin. The zirconia samples were divided into 4 groups: without surface painting (GC), painted without surface treatment (G1), hydrofluoric acid etching before painting (G2), and blasted with alumina before painting (G3). The samples were characterized by X-ray diffraction, scanning electron microscopy, Vickers hardness, 3D roughness, and cytotoxicity. Shear bond strength (SBS) tests were used to measure the zirconia bonding to synthetic dentin (NG-10 polymer). The opacity of painted zirconia was evaluated using a spectrophotometer with contrast ratio as a translucency parameter. The results showed the sintered zirconia had high densification, and submicrometric tetragonal (t-ZrO2) and cubic (c-ZrO2) grains. The bonding shear strength of zirconia without surface painting and surface treatment (3.51 MPa) was the lowest. The highest bonding strength was painted zirconia without surface treatment (15.51 MPa). The zirconia etched with HF had a lower shear strength (5.75 MPa) than the zirconia blasted with alumina (7.76 MPa). As the painting coating thickness increased, the opacity increased. The cytotoxicity tests showed that the coated zirconia is biocompatible. The zirconia painting with epoxy powder paint methodology facilitates the manufacture of dental prostheses and increases the shear bonding strength to dentin.

BEYOND APPEARANCE

The history of dentistry has origins that are lost in time, with ancient records that date back to the manufacture of dental prostheses. In the contemporary scenario, dentistry has experienced remarkable progress, especially in the field of dental prostheses, where new materials have emerged with the aim of harmoniously integrating with the natural structure of the teeth. One of the notable advances is the innovation of alternatives for Removable Partial Dentures, moving away from conventional metallic components and adopting plastic materials. These polymeric options provide greater flexibility, minimize allergy risks, and facilitate adaptation. From a methodological perspective, an extensive literature search was undertaken, using the renowned PUBMED database, covering the time interval between 2013 and 2023. The chosen keywords, “Dentistry”, “dental prosthesis” and “partial prosthesis flexible”, were adopted to guide the consultation. By compiling the samples extracted from the examined literature, it is possible to deduce that flexible prostheses inherently offer superior aesthetic and comfort attributes to patients, thus surpassing conventional alternatives. Despite the ergonomic and aesthetic advantages that they present, the use of flexible prostheses as a permanent prosthetic solution lacks justification, due to the potential harmful impact on periodontal support, mainly associated with the lack of occlusal support. Therefore, it is undeniable that flexible prostheses provide remarkable comfort and admirable aesthetics, which puts them in an advantageous position compared to traditional alternatives. However, there are still intrinsic aspects that deserve attention and improvement. In this context, the continuous search for excellence in the balance between the desired aesthetics and the necessary durability is evident, aiming to offer patients a complete and satisfactory prosthetic experience. The present work proposes to elucidate the advantages and permanence inherent to flexible partial dentures, in addition to making a comparison regarding their quality and durability as opposed to conventional partial dentures. This analysis is primarily based on the review of the relevant scientific literature, thus allowing a grounded and objective approach to the subject in question.

The effect of gamma irradiation on the synthesis, microbiological sterility, and improvement of properties of PMMA-Al2O3 composite used in dental prosthesis manufacturing

Polymethyl methacrylate (PMMA) is a polymer material widely used in dental applications due to its excellent biocompatibility, stable physicochemical properties, easy manipulation, and low cost. The combination of biocompatible polymers and ceramics has great potential for the development of materials in the dental industry with improved mechanical properties. The addition of Al2O3 nanoparticles to PMMA can significantly improve its compressive and flexural strengths and wear resistance. Since this material is used in dental applications, it requires a high degree of product sterility. This can easily be achieved with gamma radiation treatment. Gamma radiation not only ensures the sterility of the product but can also affects changes in numerous material properties.The aim of this paper is to determine the influence of different doses of gamma radiation on the microbiological purity and changes in the mechanical and thermal properties of the PMMA/Al2O3 composite as well as the microstructural and color changes. It was found that the dose of radiation of 25 kGy is sufficient for complete sterilization of the product. This radiation dose improves the mechanical properties of the material and thermal stability. On the other hand, the dose of 25 kGy does not affect the morphology of the exposed sample and has small effect on the color change.

Effect of Spindle Speed on Microstructure and Flexural Strength of Dental Direct Bio Zirconia

Dental direct block are dental mill blanks made from Yttrium stabilised, presintered and zirconium oxide blanks for the manufacture of dental prostheses. Dental direct presintered blocks with disk-shapede were used to machining the specimens at different rotational speed (10000,20000,40000) r.p.m by After that, the specimens were put through a uniaxial flexure test using balls and loaded in a universal testing machine at a cross-head speed of 0.5 mm/min until they failed. Computer Numerical Control machine (CNC) then sintered at 1600℃. The rotating speed affected the flexural strength, microstructure, crystal phase, and grain size of the studied zirconia. The characterization of samples were conducted using field emission scanning electron microscopy (FESEM) and analyzed with X-ray diffraction (XRD). The results XRD analysis showed the presence of a tetragonal phase in all rotational speeds. The differences in morphology and grain size due to different in rotational speed and grain size increase with increasing the rotational speed about 36%. The best flexural strength was observed at low speed, while Hardness showed little varation (decreasing10%) with increasing rotational speed.

Effect of enzymatic degradation and hydrolysis on 3D-printed resin-based composite material for temporary dental crowns and bridges

Abstract Additive manufacturing of dental prostheses e.g. composite materials is continuously finding broader application in dentistry. In the oral environment, the materials are subjected to hydrolysis and accelerated hydrolysis by enzymes. With the aim to compare an additively manufactured composite with a self-curing and a CAD/CAM material of the same composition, the effect of enzymatic degradation and hydrolysis on the materials were investigated. The experimental composites consisted of 50 wt. % inorganic filler and 50 wt. % monomer matrix (BisEMA, BisGMA, TEGDMA). The influence of hydrolysis via a buffer system was investigated in comparison to enzymatic degradation by cholesterol esterase over 22 days. The detection of degradation products over time was conducted by HPLC-DAD analysis. Degradation products and monomers calibrated were: TEGDMA, BisGMA, BisEMA, MA, TEGMA, Bis-HPPP and E-bis-PA. Surface roughness of polished specimens was measured by AFM and hardness with a Vickers micro hardness tester. After enzymatic degradation and hydrolysis, BisGMA was detected in the eluates of the additively manufactured composites. The samples fabricated by CAD/CAM behaved similar during hydrolysis, where additionally MA was detected. After enzymatic degradation, furthermore TEGMA and BisEMA were detected qualitatively. In contrast, the self-curing material exhibited traces of MA, TEGMA, TEGDMA and BisGMA after enzymatic degradation. Hereof detectable upon hydrolysis were MA, TEGMA and BisGMA. Surface roughness was comparable for all manufactured samples whereas the hardness was lowest of the 3D printed material. Enzymatic degradation and hydrolysis had no effect on surface roughness and hardness. The additively manufactured composite appeared to have low susceptibility to enzymatic degradation and hydrolysis. Due to the manufacturing process, the polishability and initial hardness are poorer.

The harnessing of the waste arising from Y-TZP dental ceramics manufactured by CAD/CAM to be used as alternative dental materials

A large amount of yttria-stabilized zirconia (Y-TZP) waste is produced during the manufacture of dental prostheses by the CAD/CAM milling process. This work investigated the recycling and processing of zirconia waste powder (ZWP), generated from the manufacture of dental prostheses (CAD/CAM milling process). The physical and mechanical characteristics of the bodies produced with ZWP were evaluated. The received ZWP was calcined at 500 °C and de-agglomerated with a roll jar mill under different experimental conditions. The grinding condition with a relation between grinding medium mass (GM) and ZWP mass of 13 and a milling time of 90 min presented the best results. This procedure produced ZWP with the smallest mean particle size (0.4 μm) and the lowest tetragonal-monoclinic transformation (16.9%). The water absorption, apparent porosity, bulk density, and mechanical properties were evaluated from ZWP non-deagglomerated and ZWP de-agglomerated after sintering at 1300 °C, 1400 °C, and 1500 °C. ZWP de-agglomerated samples reached bulk density, microhardness, and flexural strength values of 5.8 ± 0.1 g/cm3, 1523 ± 173 HV, and 342.8 ± 66.7 MPa, respectively. The achieved values of bulk density and microhardness were similar to those of commercial ZrO2 bodies processed under the same conditions, 6.0 ± 0.1 g/cm3 and 1412 ± 70 HV, respectively. But flexural strength of ZWP bodies was lower than that of commercial ZrO2, 680.5 ± 96.0 MPa. However, the achieved strength is higher than that observed for porcelain and glass-ceramic dental materials used for single-unit anterior or posterior prostheses (<200 MPa), which depicts the ZWP potential as an alternative low-cost and high-strength material in ceramic prostheses.

Prevention of Occupational Hazards Due to Asbestos Exposure in Dentistry. A Proposal from a Panel of Experts.

Asbestos in all its forms is a Group 1 material agent with proven carcinogenic effects in the human being since 1977. Exposure to asbestos can be considered unsafe. The use of asbestos in the field of dentistry had a common use in the manufacture of dental prostheses in the 1960s and 1970s. Taking into account the long induction period of this agent and the plausibility for being a risk factor in dentistry, the objective of this study is to propose a plan for the prevention of occupational risks due to asbestos exposure in dentistry by means of the contribution of a panel of experts. An Expert Panel (EP) approach was used in which a group of nine experts identified and documented the use of asbestos in the dental profession. EP was created and followed the protocol in accordance with the EuropeAid Assessment Guidelines. As a result of this study, EP documented the common use and sources of asbestos in dentistry in prosthetic materials, dental dressings, and in the coating of casting cylinders. EP also created a consensus document on the priority measures for the Plan for the Prevention of Risks from Asbestos in Dentistry, based on previous reports from the European Commission Senior Labour Inspectors’ Committee. The document concluded that obtainment of information, receiving specific training on the subject and performing epidemiological studies, and the proper risk assessments were the priority measures to adopt.

The Effect of Gamma Irradiation on the Synthesis, Microbiological Sterility, and Improvement of Properties of Pmma-Al2o3 Composite Used in Dental Prosthesis Manufacturing

The Effect of Gamma Irradiation on the Synthesis, Microbiological Sterility, and Improvement of Properties of Pmma-Al2o3 Composite Used in Dental Prosthesis Manufacturing

Comparative Analysis of Biofilm Formation on Materials Used for the Fabrication of Implant Supported Prostheses.

Background:Zirconia and other dental pottery, heat-restored polymethyl methacrylate, titanium and other metal amalgams, or a mix of these materials are utilized to fix inserts. It is important to choose a material that is resistant to bacterial colonization for implant-supported prostheses, but durability and aesthetics are important factors as well.Aim:Biofilm generation on materials used in implant-supported dental prosthesis manufacturing was an objective of this investigation.Methods and Materials:In this study, 90 discs were prepared. These discs were divided into three groups: group PMMA, group Y-TZP, and group CP-Ti. Each group consisted of 30 discs. As helpful materials, 30 discs (D = 15 mm, H = 3 mm) each were created from either monetarily unadulterated titanium (CP-Ti), yttria tetragonal zirconia polycrystal (YTZP), or hotness-restored polymethyl methacrylate (PMMA). The examples were cleaned as per acknowledged practices. The non-contact profilometer (NPFLEX, Bruker, UK) was utilized to survey the surface rougness of each disc, and the outcomes were accounted for as Ra (m). An assortment of gram-negative microbes, including Aggregatibacter actinomycetemcomitans, Tannerella forsythia, Porphyromonas gingivalis, Prevotella intermedia, and Tannerella albicans, were refined close by cleaned discs produced using heat-relieved PMMA, Y-TZP, or CP-Ti to see which type of biofilm is shaped best. CFU/mL was the unit of estimation (state framing units per milliliter).Results:Y-TZP discs have a substantially higher Ra (349 41 m) than PMMA and CP-Ti discs. Some bacteria that have been associated with peri-mucositis and peri-implantitis may be less prevalent on Y-TZP or CP-Ti discs. Biofilm development must be considered while making implant-supported prostheses using Y-TZP and CP-Ti.Conclusion:Y-TZP and CP-Ti are preferred materials for implant-supported prosthesis production because of biofilm development.

THE PROSTHODONTIC TREATMENT OF THE MANDIBLE EDENTULOUSNESS. CLINICAL CASE

The article presents a clinical case of the prosthodontic treatment of the mandible edentulousness.&#x0D; Edentulousness is a widespread pathology that depends on the social and economic situation in the country, the demographic situation, the level of dental care and prevention organization. The current worldwide trend of population aging leads to an increase in the number of the elderly, and this number is expected to increase in the future. According to the WHO, today about 600 million people are people over 60, and this number will have doubled by 2030 and will constitute 2 billion in 2050 mostly in developed countries. The situation in Ukraine is not better.&#x0D; Functional and aesthetic rehabilitation of patients with edentulousness requires a comprehensive approach to the prosthodontic treatment planning. Complete removable laminar dentures on the mandible have a number of disadvantages. Insufficient fixation, stabilization, diction problems, aesthetic problems, decreased self-esteem of the patient are among the key ones. Modern protocols of the prosthodontic treatment require the manufacture of dental prostheses based on intraosseous dental implants.&#x0D; Complete dentures based on intraosseous dental implants have a number of advantages over the fixed dentures. Compensation for deficient bone support of the facial soft tissues occurs by means of the basis. Patients’ possibility to remove a secondary restoration by themselves lead to proper hygiene of the oral cavity and peri-implant area in particular.&#x0D; The clinical research conducted by S. Wolfart (2016) showed the possibility of fixed/removable dental prosthesis fixation in 14-31 days (early loading) after the surgical stage of implantation provided that 4-6 intraosseous dental implants were installed. The maximum mobilization of the patient to comply with the recommendations and prescriptions is the main task considering the limited postoperative period before the dental prosthesis fixation.&#x0D; Our publication describes the treatment of a patient born in 1967, who was diagnosed with a mandible complete absence of teeth. Diagnosis, examination and treatment were performed on the basis of the Department of Dentistry Postgraduate Education of Ivano-Frankivsk National Medical University.&#x0D; The described prosthodontic treatment plan involves the manufacture of a complete denture with bar system based on four intraosseous dental implants according to the early loading protocol in a patient with primary treatment of mandible edentulousness.&#x0D; The choice of treatment plan was based on the results of past medical history, the patient’s disease, basic and additional methods of examination, analysis of individual indications and contraindications and readiness for the selected treatment plan.&#x0D; This treatment protocol has its advantages over the protocol of manufacturing a fixed prosthesis based on intraosseous dental implants such as a higher level of proprioceptive sensations, increased level of hygiene, lower complexity of clinical and laboratory stages, affordability.&#x0D; The term of clinical and laboratory stages of manufacturing (from the surgical stage of implant treatment to the fixation of the dental prosthesis) constituted 16 days.&#x0D; Additional opportunities for success in clinical and laboratory stages of treatment, the accuracy of manufacture and minimization of complications in the future were created as a result of the combination of digital and analog treatment methods in dental prosthesis manufacturing.

MODERN TECHNOLOGIES FOR THE MANUFACTURE OF GLASS-CERAMIC DENTAL PROSTHESES

The relevance of the problem of improving the quality of life and protecting human health in the context of the successful development of the modern society was presented. A literary review of well-known modern technologies for the design and manufacture of dental prostheses was carried out, as well as the leading domestic and foreign companies that were engaged in this were given. The history of the development of materials for obtaining clinical restorations (crowns, inlays, onlays, etc.) was considered and the main directions of the development of innovative ceramic materials for dental prosthetics were outlined. Based on the analysis of the properties of various types of materials for dental prosthetics, the prospects of using glass-ceramic materials in the development of dental prostheses have been substantiated. The chemical compositions of lithium silicate glasses for the synthesis of the glass matrix have been developed and the technological parameters for the production of glass-ceramic dental prostheses have been selected (Тgl. melting = 1350–1400 °С, Тheat treatment = 600–650 °С). Preliminary heat treatment before the formation of products ensures the formation of the required number of the nucleus of crystalline phase and the prerequisites for creating a volume crystallized structure under conditions of short-term heat treatment. The glass-ceramic prosthesis with a formed interpenetrating sitallized structure was obtained by the method of hot pressing with a short exposure (18-20 min). It was found that the obtained glass-ceramic material containing lithium disilicate as a crystalline phase in an amount of 40-60 vol. %, had high values of bending strength (σ = 400 MPa) and fracture toughness. The indicated mechanical properties of the developed materials, along with the approximate values of their modulus of elasticity to natural teeth, will significantly extend the service life of products under conditions of significant alternating loads that arise during the chewing cycle. A comparative assessment of the competitiveness of the developed dental prostheses based on lithium disilicate with world analogues was carried out, in particular the products of Ivoclar Vivadent and Vita Zahnfabrik, in terms of the main operational parameters. The positive effect of the introduction of domestic developed glass-ceramic dental prostheses to reduce import dependence has been determined.

Diş Laboratuvarı Teknisyenlerinde IL-1Ra ve IL-4 Geni VNTR Polimorfizmlerinin Analizi: Genotip-Fenotip Çalışması

For people working in dental prosthesis laboratories (DPL), metal alloys and methylmethacrylate-based monomers and polymers used in the laboratory can pose occupational risks. These risks can cause occupational health problems and toxic effects on human health. This study purposes of researching the effects of occupational exposure because of dental prosthesis manufacturing operations on variable number tandem repeat (VNTR) polymorphisms in IL-1Ra and IL-4 genes. 29 DPL workers, the experimental group, were given a questionnaire, including the symptoms that might arise due to occupational exposure, and their responses were compared with 30 participants as a control group. Genotype distributions and allele frequencies for IL-1Ra intron 2 (rs2234663) and IL-4 intron 3 (rs79071878) VNTR polymorphisms were analyzed using the PCR technique. Both IL-1Ra intron 2 and IL-4 intron 3 polymorphisms identified from the experimental and control groups were not statistically significantly different (p &amp;gt;.05). However, runny nose, burning throat, dyspnea and dryness and rash on the skin were significantly different when DPL workers were compared with the control group according to logistic regression analysis (p &amp;lt;.05). No statistical difference was found in other phenotypic characters. However, due to the limited sample size, our results need to be confirmed in large-scale studies.

Al2O3 Preforms Infiltrated with Poly(methyl methacrylate) for Dental Prosthesis Manufacturing

The combination of biocompatible polymers and ceramics shows great promise in the development of composites with suitable mechanical properties for dental applications. In an attempt to further expand this research line, Al2O3 commercial powders (Vitro-ceram, Alglass, In-ceram) were sintered at 1400 °C for 2 h and infiltrated with poly(methyl methacrylate) for potential use in dental prostheses. The infiltration was performed using a homemade apparatus under a pressure of 7 bar for 6 and 12 h. The microstructure (studied using a scanning electron microscope), Archimedes density, 3-point bending flexural strength and Vickers hardness of the prepared composites were assessed and quantitatively compared. In general, microstructural analyses showed ceramic- and polymer-based interpenetrating network in all materials. The preforms infiltrated for 12 h showed superior properties; among them, the Vitro-ceram-based composite also demonstrated a near-zero open porosity and optimum mechanical characteristics. Specifically, its density, strength and hardness were 2.6 ± 0.07 g/cm3, 119.3 ± 5.0 MPa and 1055.1 ± 111.0 HV, respectively, passing the acceptance criteria of ISO 6872 and making it suitable for consideration as a metal-free structure for dental crowns and fixed partial prostheses until three anterior units.

Investigation of morphological abnormalities in red blood cells among dental laboratory technicians.

A variety of materials are used in dental prosthesis laboratories (DPL), especially metal alloys and methyl methacrylate (MMA)-based monomers and polymers. These metal alloys contain elements such as cobalt, chromium, nickel, molybdenum, lead, and mercury that can have toxic effects on human health when excessive amounts of exposure occur. This study aims to investigate the cytotoxic effects of occupational exposure due to dental prosthesis manufacturing operations on erythrocyte cells. Thirty DPL workers were compared with the 30 control group and the questionnaire forms were applied including the symptoms due to their occupational exposure. Blood was taken from the experimental group and the control group into tubes with EDTA, and the erythrocyte morphologies were examined by the peripheral smear technique. Morphological anomalies determined from the experimental group and the control group are statistically significant (p < .005, p < .01). On the other hand, it was revealed that the sub-variables, namely age range, alcohol, and smoking, did not significantly affect the anomalies. With these results, it was concluded that DPL employees should strictly comply with occupational health precautions.

Relationship between Phase Fractions and Mechanical Properties in Heat‐Treated Laser Powder‐Bed Fused Co‐Based Dental Alloys

AbstractMetal additive manufacturing of dental prostheses consisting of cobalt−chromium−tungsten (Co−Cr−W) alloys poses an alternative to investment casting. However, metal additive manufacturing processes like Laser Powder‐Bed Fusion (LPBF) can impact the elastic constants and the mechanical anisotropy of the resulting material. To investigate the phase compositions of mechanically different specimens in dependence of their postprocessing steps (e. g. heat treatment to relieve stress), the current study uses X‐ray Diffraction (XRD), Electron BackScatter Diffraction (EBSD), and Transmission Electron Microscopy (TEM) for phase identification. Our studies connect plastic deformation of Remanium star CL alloy with the formation of the hexagonal ϵ‐phase and heat treatment with the formation of the D024‐phase, while partially explaining previously observed differences in Young's moduli.

Features of physical and mechanical properties of materials used in orthopedic rehabilitation of patients

Basic materials have been studied. Types of applied basic materials, readings for application are considered. In a comparative aspect, their physical and mechanical properties are considered, and features arising in the manufacture of dental prostheses are indicated.