Tsanka Dikova

Medical University of Varna · Department of Dental Materials Science and Propaedeutic of Prosthetic Dentistry

Titanium is the most used material for implant production. To increase its biocompatibility, continuous research on new coatings has been performed by the scientific community. The aim of the present paper is to prepare new coatings on the surfaces of the pure Ti Grade 2 and the Ti6Al4V alloy. Three types of coatings were achieved by applying anodi...

Additive manufacturing technologies (AMTs) offer a new approach for cost-effective production of goods and services and are therefore quite rightly included as part of the Fourth Industrial Revolution, Industry 4.0. Last years great attention is paid to the AMTs as technologies of the future development in many countries all over the world includin...

The aim of the present paper is to investigate the microstructure of laser-melted surface layers of austenitic steel for biomedical applications. The surface of prismatic specimens from AISI 321 stainless steel was treated by continuous CO2 laser. Three modes of laser processing were used, ensuring surface melting. The microstructure was observed b...

Introduction: After laser melting during welding and heat treatment processes, the melted zone of the austenitic steel is characterized by a specific fine-grained microstructure formed as a result of the high heating and cooling rates. This causes additional difficulties when the microstructures of the molten zone and the base metal have to be inve...

The present paper aimed at investigating the influence of surface treatment on the failure of porcelain coating on Ti6Al4V alloy fabricated by milling and selective laser melting (SLM). The titanium alloy surface was treated by three different ways: sandblasting, application of a layer of bonding agent and combined (sandblasting and subsequent bond...

Nanosilicate-polysaccharide composite hydrogels are a well-studied class of materials in regenerative medicine that combine good 3D printability, staining, and biological properties, making them an excellent candidate material for complex bone scaffolds. The aim of this study was to develop a hydrogel suitable for 3D printing that has biological an...

In recent years, the application of titanium and its alloys for production of metal frameworks for metal-ceramic fixed partial dentures has been increasing. They are fabricated mainly by casting, CAD/CAM milling and selective laser melting. Manufacturing technologies affect the surface characteristics of the metal, which in turn affects the adhesio...

The aim of the present paper is to develop laboratory protocols for fabrication of metal-ceramic fixed partial dentures (FPD), the infrastructure of which is manufactured from Ti6Al4V alloy by milling and selective laser melting (SLM). It has been established that milled and SLM metal frameworks must be sandblasted prior to porcelain application. T...

The purpose of this overview is to analyze the application of different types of lasers and laser processing technologies in modern dentistry. The analysis is based on the classifications of lasers according to several main characteristics, including active medium and spectral range, mode of operation and power, energy efficiency and accuracy. Two...

The aim of the present paper is to investigate the hardness and elastic modulus of Ti6Al4V alloy produced by CAD/CAM milling and selective laser melting. The Vickers micro-hardness is measured, while the modulus of elasticity is determined by new developed methodology consisting of bending test and finite element analysis. It was established that t...

The aim of the present paper is to investigate the influence of factors in photopolymerization process that govern microhardness of three types of dental composites—universal (UC), bulk-fill (BC), and flowable (FC). Cylindrical specimens with different thicknesses are made and light cured. The significance of light intensity, irradiation time, and...

The aim of the present paper is to examine the morphology and surface roughness of Ti6Al4V alloy produced by CAD/CAM milling and selective laser melting (SLM) in as-produced state and after sandblasting. Surface morphology is investigated by optical microscopy and BAC and ADC curves of its profile. The Ra, Rq and Rz parameters are used for evaluati...

The object of this review article is to follow the current trends in the scientific literature on corrosion in biological fluids of chromium-nickel stainless steels after laser treatment. The paper is organized in three sections. The first section presents the main types of stainless steels according to their microstructure and the application of t...

The aim of the present paper is to investigate the geometrical characteristics and density of Ti6Al4V alloy produced by CAD/CAM milling and selective laser melting (SLM). Two groups of prismatic samples (plates) were manufactured by milling and SLM. The width and thickness of the specimens were measured and the average value was used in the analysi...

The present study aims to develop recipe compositions and technology for producing sponge cakes from wholemeal flour, partially replaced with a functional plant component dry blossom flour of Sambucus nigra L. Three designs of sponge cakes with 5, 10, and 15% content of flour of Sambucus nigra L. corrected up to 100% with whole-grain oat flour were...

The design of the developed equipment for catalytic water purification with a gas-saturated reactor is described. Promising composite materials for the manufacture of the main structural elements of its units are presented. The results of water purification are presented, indicating the high efficiency of the equipment.KeywordsEquipmentCatalytic wa...

The aim of the present paper is to investigate the bond strength of dental ceramic to Ti6Al4V alloy fabricated by milling and selective laser melting (SLM). The adhesion strength is studied by 3-point flexural test of samples with porcelain coating. Two groups of specimens are manufactured by milling and SLM. Four different surface treatments are u...

Quartz-tungsten halogen light curing units (LCUs) have been the main source of light for the polymerization of resin based composites (RBCs) for several decades. Since the beginning of the 20th century, however, their use has been reduced due to the invention and improvement of LED LCUs. Various factors can cause a decrease in the light intensity o...

Purpose: of the present paper is to investigate the micro-hardness of three types of resin-based composites – conventional, bulk fill and flowable. Design/methodology/approach: Cylindrical specimens with a diameter of 5 mm and thicknesses of 2, 3 and 4 mm were made from each composite. They were light cured for 20, 40 and 60 s with light intensity...

The aim of this paper is to perform optimization of photopolymerization process of dental composites in order to obtain maximum hardness. Samples (5 mm diameter; 2, 3 and 4 mm thickness) were made of Universal Composite (UC), Bulk fill Composite (BC) and Flowable Composite (FC). Light curing of specimens was performed with 600, 1000 and 1500 mW/cm2...

The present paper deals with studying the surface morphology of commercially pure (cp) Ti Gr-2 and Ti6Al4V treated by a picosecond laser and with determining the optimal technological parameters for fabricating cavities with a regular shape and a depth of about 10 μm. The surfaces of disk-shaped samples were treated by a commercial picosecond laser...

The aim of the present paper is to study the stresses and strains in fillings of V-shaped tooth defects made of universal photo-cured nanohybrid composite (UPC) using incremental technique. Numerical modeling with FEA and microleakage test are performed. Inhomogeneous distribution of the equivalent Von Mises stresses after polymerization of the two...

Coated flat metal tensile specimens are widely used for determination mechanical properties of the coating-substrate system. These properties are identified by а comparison of an analytical model with experimentally observed delamination. Present paper deals with study the problem of a ceramic coating on a Co-Cr dental alloy substrate under tensile...

The aim of the present paper is to study the microleakage of wedge-shaped defects, filled with restorative materials of different groups. Thirty six human teeth (incisors, canines and premolars) with V-shaped defects, prepared on them, were used. The cavities were obturated with auto-cured resin-modified glass-ionomer cement (RMGIC), flowable photo...

The aim of the present paper is to use analytical methodology by 2D shear-lag model in parametric analysis of the normal stress in the coating. The tension of a substrate with coatings on its top and bottom surfaces is considered. The parametric study is performed by varying coating thickness and elastic properties both the coating and the substrat...

The process of selective laser melting (SLM) is an alternative to the conventional technologies and can be used to solve many of their problems. During SLM process, an object is produced directly from a virtual 3D model by melting a metal powder layer by layer using a laser. Incorrectly selected process parameters can lead to defects decreasing the...

In recent years, LED light curing units (LCUs) have become the main source of light for the polymerization of resin based composites (RBCs). Various factors can affect the normal functioning of LCUs, one of which is the battery charge of the wireless models. The aim of this study is to evaluate the stability of the light intensity of different bran...

The aim of the present paper is to investigate the deformation-stress state of fillings of V-shaped tooth defects by finite element analysis (FEA). Two different materials are used-auto-cured resin-reinforced glass-ionomer cement (GIC) and flowable photo-cured composite (FPC). Two materials are placed into the cavity in one portion, as before the a...

Selective laser melting (SLM) is an additive manufacturing technique that is designed to produce objects by melting and fusing of metal powder with a laser. As a result, parts with high accuracy, fine-grained microstructure and high mechanical properties are obtained which is a precondition for application of SLM process in dentistry. The aim of th...

The aim of the present paper is to investigate the morphology of titanium surfaces treated with picosecond laser. Round samples of cpTi Gr-2 and Ti6Al4V alloy were treated by a commercial picosecond laser. Two variables were used: average power (1W, 0.5W, 0.2W) and pulse number (1,000-20,000). The samples were investigated by OM, SEM, EDX and non-c...

One of the most significant current discussions in dentistry is the great variety of devices used for light curing of dental composites. It is possible to assess the benefits of light polymerization only if we look at them historically. The aim of this study is to examine the devices used for light curing of dental composites, to compare them and t...

Present paper deals with the specifics in production of fixed partial dentures (FPD) using 3D printed cast patterns. The cast patterns of four-part dental bridges were manufactured of polymer NextDent Cast using RapidShape D30 printer. Two cases of application of cast patterns were discussed – for production of press-ceramic and metallic constructi...

INTRODUCTION: Temporary crowns and bridges are the main elements in the treatment with fixed partial dentures. They are usually manufactured from methacrylate polymers and composites by heat-curing or CAD/CAM milling. Additive technologies (ATs) offer a number of advantages in the production of temporary dental restorations. However, there is a lac...

Present paper deals with investigation the failure of ceramic coatings on cast and selective laser melted (SLM) Co-Cr dental alloys by tensile test and finite element analysis (FEA). It is established that the failure mode of porcelain coatings is mixed/cohesive in SLM alloy and mixed/adhesive in cast. In both alloys, maximum shear and normal stres...

In recent decades, the development of new materials and new production technologies has been carried out under exponential law, and these two processes have constantly exchanged their leading role. According to the rules of the modern market economy, equipment manufacturers try to implement it as quickly as possible in the real production, which is...

В последните десетилетия създаването на нови материали и развитието на производствените технологии се осъществява по експоненциален закон, като тези два процеса постоянно разменят своята водеща роля. Съгласно правилата на съвременната пазарна икономика, фирмите-производителки на апаратура и оборудване се стремят да ги внедрят възможно най-бързо в р...

The adhesion of IPS InLine ceramics to a cast dental Ni–Cr (Wiron light) alloy is experimentally studied during the tensile test of flat coated specimens, and the results of a numerical simulation and multicriteria optimization using the MADMML software package are presented. Casting patterns were printed on a 3D Rapidshape printer at angles of 0°...

ooth restoration is one of the most common procedures in dental practice. The replacement of the whole restoration leads to loss of tooth structure and it’s weakening, there is a risk of pulp injury, it’s time and cost consuming. According to the minimally invasive approach when minimal defects have occurred, or the diagnosed defect is localized on...

The aim of this paper is to investigate the fracture during bending test of Co-Cr dental bridges, produced by additive technologies. Three groups of samples (four-part dental bridges from 1-st premolar to 2-nd molar) were produced by conventional casting with handmade wax patterns, casting with 3D printed patterns and selective laser melting (SLM)....

Purpose: To compare the dimensions accuracy and surface roughness of polymeric dental bridges produced by different 3D printers. Design/methodology/approach: Four-part dental bridges were manufactured by three printing systems working on the basis of digital light projection (DLP) stereolithography (SLA), laser-assisted SLA and fused deposition mod...

In this study, tribological characterization of cast and selective laser melting (SLM) processed Co-Cr-Mo alloys under dry and wet conditions were investigated. Cast alloy (64.80Co-28.50Cr-5.30Mo-0.50Si-0.50Mn-0.40C, wt.-%) was produced by lost-wax casting method, while SLM processed alloy (65.20Co-28.30Cr-5.48Mo-0.75Si-0.16Fe-0.03V, wt.-%) was man...

INTRODUCTION: Gas discharge visualization (GDV) is a method for a complete diagnosis, which is based on natural physical phenomena in human body. Since the invention of GDV, till present, there has been an increasing interest in its application in different areas of life. The most important use of GVD is in medicine. GDV provides the possibility fo...

The present paper is a case report of prosthetic treatment built upon 3D technologies for manufacturing of dental restorations. The case shows laboratory protocol of 3D printed full coverage provisional crowns and cast patterns for press ceramic crowns for a patient with need of replacement of the old prosthetic constructions of his upper left firs...

Purpose: of the present paper is to offer treatment protocol with fixed partial dentures, produced by selective laser melting, including clinical and laboratory parts. Design/methodology/approach: The treatment protocols with selective laser melted fixed partial dentures was developed on the basis of literature survey and our previous research abou...

Purpose: of this paper is to investigate the accuracy of Co-Cr dental bridges, manufactured using 3D printed cast patterns. Design/methodology/approach: Four-unit dental bridges are fabricated from the alloys i-Alloy and Biosil-f by lost-wax process. The polymeric cast patterns are 3D printed with different layer’s thickness (13 μm, 35 μm and 50 μm...

Purpose: of the present paper is to develop prosthetic treatment protocol for fixed partial dentures made of 3D printed cast patterns. Design/methodology/approach: The clinical and laboratory protocols for manufacturing of fixed prosthetic constructions upon 3D cast patterns are developed on the basis of the literature review and our previous exper...

The aim of the present paper is to make a review of the properties of dental alloys, fabricated using Additive Technologies (AT). The microstructure and mechanical properties of Co-Cr alloys as well as the accuracy and surface roughness of dental constructions are discussed. In dentistry two different approaches can be applied for production of met...

The aim of the present paper is to investigate the fitting accuracy of Co-Cr dental bridges, manufactured by three technologies, with the newly developed method using CAD software. The four-part dental bridges of Co-Cr alloys were produced by conventional casting of wax models, casting with 3D printed patterns and selective laser melting. The margi...

The necessity of precise estimation of the gap between the crowns-retainers and abutments of dental bridges requires the development of new methods for their measurement. The introduction of rapid prototyping technologies, including 3D scanning and printing, enables trouble-free creation of virtual models of complex objects in terms of form. The de...

The study and application of the materials that are stable in the temperature range up to 1000°C are necessary to repair forming dies operating in this range. Nickel-based alloys can be used for this purpose. The structural state of a nickel alloy layer deposited onto a KhV4F tool steel and then heat treated is investigated. KhV4F tool steel (RF GO...

Studying the fracture characteristics of porcelain coatings plays a main role in selection of materials for metal-ceramic restorations. The aim of this work is to study the effect of the substrate manufacturing process on the adherence of the porcelain. The coatings of porcelain IPS.Inline (Ivoclar Vivadent) are fused onto dental Co-Cr alloys fabri...

The aim of the present paper is to study the factors, influencing on the quality of Co-Cr dental alloys, cast using 3D printed patterns. Three groups of factors are discussed: the properties of the materials for 3D printing, the special features of the 3D printing process and the peculiarities of the casting. As mainly polymers are used for 3D prin...

The purpose of the present paper is to evaluate the geometric accuracy and surface roughness of polymeric samples manufactured by Digital Light Projection (DLP) Stereolithography. The standard cubic samples with dimensions 5 mm х 5 mm х 5 mm were printed of two polymers: NextDent C+B (white-yellowish color A3.5, VITA shade guide) and NextDent Cast...

The aim of the present paper is to evaluate and compare the strength properties and deformation characteristics of cast and Selective Laser Melted (SLM) Co-Cr dental alloys by using CAD/CAE software. The Solid Works Simulation software is used for simulation of chewing load of the virtual 3D model of a four-part dental bridge. Two Co-Cr dental allo...

The additive technologies characterize with the building of one layer at a time from a powder or liquid that is bonded by means of melting, fusing or polymerization. They offer a number of advantages over traditional methods: production of complex personalized objects without the need of complex machinery; manufacturing of parts with dense as well...

Cobalt-chromium based alloys are widely used in dental applications due to their excellent mechanical properties, high corrosion resistance and good biocompatibility. Although they are generally fabricated by casting for dental restorations, recently selective laser melting (SLM) has become an attractive production method since it allows complex ge...

The aim of the present paper is to investigate the mechanical properties (hardness and tensile strength) of dental Co-Cr alloys fabricated via casting and selective laser melting (SLM). Two groups of metallic specimens (four-part dental bridges and standard tensile test specimens) made of Co–Cr dental alloys were produced by lost-wax casting and SL...

The aim of the present paper is to review the application of 3D printing technologies for manufacturing of patterns for investment and sand casting. The additive technologies are characterized with building the object by addition of the material layer by layer. They offer a number of advantages over the traditional methods: easy, controllable and r...

30 години технологиите за про-изводство на дентални конструкции претърпя-ват бурно развитие, което се изразява в три ос-новни направления: цифровизация, симулация и въвеждане на технологиите за послойно изра-ботване на детайлите. В зъботехническите ла-боратории това доведе до: 1. коренна промяна в професията на зъботехника – свеждане на ръч-ния тру...

Purpose: Purpose of this paper is to investigate the accuracy of dental bridges produced via digital light projection stereolithography process. Design/methodology/approach: 3D printer Rapidshape D30 was used for manufacturing of two groups of samples – temporary four-part bridges and cast patterns for permanent bridges. The temporary bridges were...

Abstract: Ti and its alloys are mostly used for implant production. Their biocompatibility depends on the formation of thin TiO2 layer on the surface. It can be improved by modification of oxide structure in tubular. For biomedical applications, the adhesion of the coating layers is essential. The aim of the present paper is to investigate the adhe...

The purpose of the present paper is to make a review of applications of 3D-printing in contemporary prosthetic treatment as this modern technology has become widely spread not only in industry but in medicine and dentistry too. It is a form of additive manufacturing technology where a three dimensional object is created by laying down successive la...

The purpose of the present paper is to establish experimentally the possibilities of the 3D printer Rapid-shape D30 for the manufacturing of standard cubic samples from different types of monomers and to evaluate their geometrical accuracy and roughness. Standard cubic samples with dimensions 5mm х 5mm х 5mm were printed from all the materials, giv...

The aim of the present paper is to make a review of the modern trends in the development of the technologies for production of dental constructions. Three are the main trends in production technologies in dentistry last 30 years: digitalization, simulation and implementation of additive technologies. The simulation occurred first and due to the com...

Austenitic stainless steel is one of the materials commonly used for manufacturing of orthodontic appliances and brackets. In this study, samples of AISI 321 (EN X6CrNiTi 18-10) steel in initial condition and after laser surface melting were investigated in artificial saliva with pH 5.6. Two tests were conducted: measurement of open circuit potenti...

Abstract The aim of this study was to investigate the in-depth structure transformations of the laser-melted layers of the steels mostly used in tool production – T1 and D2 steels. The experiments of laser surface melting of T1 and D2 steels were done with continuous wave CO2 laser (wavelength λ = 10.6 μm). The sample’s microstructure was investiga...

INTRODUCTION The application of concentrated energy for treatment of the materials takes an important place in the fundamental research of physics in the second half of 20th century, as the 1960 years are the period with significant discoveries. The intensive scientific and scientific-applied investigations, leading to the final goal - industrial...

Purpose: The additive technologies characterize with building of one layer at a time from a powder or liquid that is bonded by means of melting, fusing or polymerization. The methods, mostly used in dentistry, include selective laser sintering, selective laser melting and 3D printing. The aim of the present paper is to investigate the microstruc...

Настоящото пособие се състои от две обособени части - теория и протоколи на лабораторни упражнения. Това е втората част на учебника „Дентално материалознание“, който е предназначен за студентите по дентална медицина. Темите на теоретичната част и лабораторните упражнения са разработени по утвърдена учебна програма на Факултета по дентална медицина...

The aim of the present paper is to investigate the surface and microstructural defects of four-part dental bridges, manufactured of Co-Cr alloy by three different technologies: standard lost-wax casting, using silicon key for wax models preparation; casting of wax models, produced by prototyping technology; Selective Laser Melting (SLM). The surfac...

The aim of this study was to investigate the in-depth structure transformations of the laser-melted layers of the steels mostly used in tool production–T1 and D2 steels. The experiments of laser surface melting of T1 and D2 steels were done with continuous wave CO 2 laser (wavelength λ = 10.6 μm). The sample’s microstructure was investigated, and t...