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974 http://www.journal-imab-bg.org / J of IMAB. 2015, vol. 21, issue 4/ MODERN TRENDS IN THE DEVELOPMENT OF THE TECHNOLOGIES FOR PRODUCTION OF DENTAL CONSTRUCTIONS Tsanka Dikova 1 , Dzhendo Dzhendov 2 , Maksim Simov 3 , Iveta Katreva-Bozukova 2 , Svetlana Angelova 3 , Diana Pavlova 3 , Metodi Abadzhiev 2 , Tsvetan Tonchev 4 1) Department of Medical and Biological Sciences, Faculty of Dental Medicine, Medical University of Varna, Bulgaria 2) Department of Prosthetic Dentistry and Orthodontics, Faculty of Dental Medicine, Medical University of Varna, Bulgaria 3) Medical College, Medical University of Varna, Bulgaria 4) Department of Oral and Maxillofacial Surgery, Faculty of Dental Medicine, Medical University of Varna, Bulgaria Journal of IMAB - Annual Proceeding (Scientific Papers) 2015, vol. 21, issue 4 Journal of IMAB ISSN: 1312-773X http://www.journal-imab-bg.org ABSTRACT 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 computers development it underwent fast progress from the mathematical calculations and analytical analysis to the 3D modeling and visualization. Thus Computer Aided Engi- neering (CAE) was developed, allowing dental constructions with optimal design to be produced by optimal technologi- cal regimes. The first Computer Aided Design (CAD) – Compu- ter Aided Manufacturing (CAM) systems were created in 1970s as a result of the digitalization. In this mode of op- eration at first virtual 3D model is generated by CAD, which then is used for production of the real construction by CAM. The CAD-CAM systems allow fabrication of dental resto- rations which is difficult or impossible to be manufactured by conventional technologies. The development of CAD unit runs from indirect scanning of the plaster model for obtaining data for the 3D model to direct scanning of the prosthesis area. While the development of CAM unit leads to direct manufacturing of the real dental construction us- ing subtractive or additive technologies. The future devel- opment of the CAD-CAM systems as a whole characterizes with transition from closed to open access systems, which make them more flexible. In the late 1980sthe new approach to the production of constructions appeared – by addition of material layer by layer. The additive technologies were developed. They characterize with building of one layer at a time from a pow- der or liquid that is bonded by means of melting, fusing or polymerization. Stereo lithography, fused deposition modeling, selective electron beam melting, laser powder forming and inkjet printing are the methods, mostly used in dentistry. Due to the great variety of the additive manu- facturing processes various materials can be used for pro- duction of different dental constructions for application in many fields of dentistry. The simulation, digitalization and implementation of additive technologies in dentistry led to fast development of the technologies for production of dental constructions last decade. As a result many of manual operations were eliminated, the constructions’ accuracy increased and the production time and costs decreased. Key words: dental constructions, simulation, digitali- zation, CAD-CAE-CAM, additive technologies, dentistry. INTRODUCTION The technologies for production of dental construc- tions undergo fast development last 30 years. This process characterizes with three main trends: digitalization, simu- lation and implementation of additive technologies. Histori- cally, the simulation occurs first. Computers, facilitating the mathematical calculations, led to the Computer Aided En- gineering (CAE), which is intended to simulate the perform- ance of the construction in order to improve its design. As a result of the digitalization the first Computer Aided De- sign (CAD) – Computer Aided Manufacturing (CAM) sys- tems were created in 1970s. Implementation of CAD-CAM systems in dentistry led to elimination of many manual op- erations, increase of the constructions’ accuracy and de- crease of the production time. In the late 1980sthe new ap- proach to the production of constructions appeared – by ad- dition of material layer by layer. The additive technologies were developed as alternative of subtractive ones. Their main advantages are: production of complex objects by dif- ferent materials – polymers, composites, metals and alloys; manufacturing of parts with dense structure and predeter- mined surface roughness; controllable, easy and relatively quick process. The aim of the present paper is to make a review of the main modern trends in the development of the technolo- gies for production of dental constructions. 1. Simulation The first simulations occurred in aviation, military http://dx.doi.org/10.5272/jimab.2015214.974

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Page 1: MODERN TRENDS IN THE … · the modern trends in the development of the technologies for production of dental constructions. Three are the main trends in production technologies in

974 http://www.journal-imab-bg.org / J of IMAB. 2015, vol. 21, issue 4/

MODERN TRENDS IN THE DEVELOPMENT OF THETECHNOLOGIES FOR PRODUCTION OF DENTALCONSTRUCTIONS

Tsanka Dikova1, Dzhendo Dzhendov2, Maksim Simov3, Iveta Katreva-Bozukova2,Svetlana Angelova3, Diana Pavlova3, Metodi Abadzhiev2, Tsvetan Tonchev4

1) Department of Medical and Biological Sciences, Faculty of Dental Medicine,Medical University of Varna, Bulgaria2) Department of Prosthetic Dentistry and Orthodontics, Faculty of DentalMedicine, Medical University of Varna, Bulgaria3) Medical College, Medical University of Varna, Bulgaria4) Department of Oral and Maxillofacial Surgery, Faculty of Dental Medicine,Medical University of Varna, Bulgaria

Journal of IMAB - Annual Proceeding (Scientific Papers) 2015, vol. 21, issue 4Journal of IMABISSN: 1312-773Xhttp://www.journal-imab-bg.org

ABSTRACTThe aim of the present paper is to make a review of

the modern trends in the development of the technologiesfor production of dental constructions. Three are the maintrends in production technologies in dentistry last 30 years:digitalization, simulation and implementation of additivetechnologies. The simulation occurred first and due to thecomputers development it underwent fast progress from themathematical calculations and analytical analysis to the 3Dmodeling and visualization. Thus Computer Aided Engi-neering (CAE) was developed, allowing dental constructionswith optimal design to be produced by optimal technologi-cal regimes.

The first Computer Aided Design (CAD) – Compu-ter Aided Manufacturing (CAM) systems were created in1970s as a result of the digitalization. In this mode of op-eration at first virtual 3D model is generated by CAD, whichthen is used for production of the real construction by CAM.The CAD-CAM systems allow fabrication of dental resto-rations which is difficult or impossible to be manufacturedby conventional technologies. The development of CADunit runs from indirect scanning of the plaster model forobtaining data for the 3D model to direct scanning of theprosthesis area. While the development of CAM unit leadsto direct manufacturing of the real dental construction us-ing subtractive or additive technologies. The future devel-opment of the CAD-CAM systems as a whole characterizeswith transition from closed to open access systems, whichmake them more flexible.

In the late 1980sthe new approach to the productionof constructions appeared – by addition of material layerby layer. The additive technologies were developed. Theycharacterize with building of one layer at a time from a pow-der or liquid that is bonded by means of melting, fusing orpolymerization. Stereo lithography, fused depositionmodeling, selective electron beam melting, laser powderforming and inkjet printing are the methods, mostly usedin dentistry. Due to the great variety of the additive manu-facturing processes various materials can be used for pro-duction of different dental constructions for application in

many fields of dentistry.The simulation, digitalization and implementation of

additive technologies in dentistry led to fast developmentof the technologies for production of dental constructionslast decade. As a result many of manual operations wereeliminated, the constructions’ accuracy increased and theproduction time and costs decreased.

Key words: dental constructions, simulation, digitali-zation, CAD-CAE-CAM, additive technologies, dentistry.

INTRODUCTIONThe technologies for production of dental construc-

tions undergo fast development last 30 years. This processcharacterizes with three main trends: digitalization, simu-lation and implementation of additive technologies. Histori-cally, the simulation occurs first. Computers, facilitating themathematical calculations, led to the Computer Aided En-gineering (CAE), which is intended to simulate the perform-ance of the construction in order to improve its design. Asa result of the digitalization the first Computer Aided De-sign (CAD) – Computer Aided Manufacturing (CAM) sys-tems were created in 1970s. Implementation of CAD-CAMsystems in dentistry led to elimination of many manual op-erations, increase of the constructions’ accuracy and de-crease of the production time. In the late 1980sthe new ap-proach to the production of constructions appeared – by ad-dition of material layer by layer. The additive technologieswere developed as alternative of subtractive ones. Theirmain advantages are: production of complex objects by dif-ferent materials – polymers, composites, metals and alloys;manufacturing of parts with dense structure and predeter-mined surface roughness; controllable, easy and relativelyquick process.

The aim of the present paper is to make a review ofthe main modern trends in the development of the technolo-gies for production of dental constructions.

1. SimulationThe first simulations occurred in aviation, military

http://dx.doi.org/10.5272/jimab.2015214.974

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and automotive industry in the beginning of the last cen-tury. The military was a major impetus in the transfer ofmodeling and simulation technology to medicine. The defi-nition of medical simulation as “an imitation of some realthing, state of affairs, or process” describes its historicalroots [1]. Physical models of anatomy and disease were con-structed long before the advent of modern plastic or com-puters. But the computers facilitated the mathematical de-scription of the human physiology and pharmacology, theworldwide communication, and the design of virtual worlds[2]. Nowadays mathematical modeling and 3D visualizationare used in learning of dental anatomy, morphology of theteeth and analysis of the state of the teeth and the surround-ing tissues in different impacts [3-6]. 3D digital models ofselected anatomy are intended to support activities such asproper diagnosis, preoperative planning, orthodontic andsurgical simulations, leading to successful treatment, riskreduction and increased patient safety [3, 7-9].

The simulation is very often used in manufacturingof dental constructions, because it gives fast and standard-ized results on the prognosis of prosthetic restorations incomparison with the clinical trials [10, 11]. Laboratorysimulation is used in two ways: 1) for investigation thebiomechanical behavior of dental constructions to under-stand the failure behavior of complex structures [12, 13];2) to optimize the experiments through the mathematicalsimulation and selection of the best design to perform thetest and the manufacturing process [11, 14]. The complexprocess of simulation is called Computer Aided Engineer-ing (CAE). It consists of three stages: simulation, valida-tion and optimization.

The simulation stage, when simplified specimens likedisks and micro-bars are used, is fast, but with low accu-racy because the influence of the restoration geometry onthe stress distribution is not taken into account. When themodels are with the shape of the crown and bridges, themechanical behavior is closer to the clinical situation, butthe evaluation of the stress distribution within complexgeometries is limited [11]. In this case the Finite ElementAnalysis (FEA) - fast and a relatively low cost method isused. In the FEA, a large structure is divided into a numberof small simple shaped elements, for which individual de-formation (strain and stress) can be more easily calculatedthan for the whole undivided large structure [15]. DuringFEA the model should be created, material properties andsoftware limitations should be input, the mesh and conver-gence analysis should be done, loading and boundary con-ditions should be applied. The computer software solves aset of simultaneous equations with thousands of variablesto achieve the desired results. Finally, the graphical pres-entation of results, including qualitative and numerical re-sults, is given [11, 12, 15]. Using FEA biomechanicalbehavior of different dental constructions such as crown,bridges, implants, implant-bone interfaces etc., made of dif-ferent materials or combination of materials – metal alloys,porcelain, metal-ceramic, composites and polymers can beinvestigated. The main advantage of FEAis the virtual simu-lation of real structures that are difficult to be clinicallyevaluated which makes it a low cost alternative in compari-

son to the other in vitro methods. But there are some limi-tations of the FEA models concerning mainly to the spe-cific patient anatomy, the wet environment and the damageaccumulation under repetitive loading [12].

For investigation of complex structures by FEA usu-ally 2D or 3D models are used depending on the complex-ity of the geometry, the type of analyses required, expecta-tions of accuracy as well as the general applicability of theresults. The main limitation of the 2D models is the loweraccuracy and reliability comparing to the 3D ones. In con-trast, a 3D model has acceptable accuracy/reliability whileproperly capturing the geometry of complex structures.However, the higher the complexity of 3D models the higherthe difficulty in generating appropriate mesh refinement forsimulation [11,12]. The 3D models can be generated by twoways depending on the structure of interest and the purposeof study. The first one is manually by using the appropri-ate software such as AutoCad, SolidWorks, Pro/Engineer orRhino 3D. The second is the imaging approach which in-volves transformation of available medical imaging filesfrom computed tomography (CT) scans, magnetic resonanceimages (MRI), ultrasound, and laser digitizers into wireframe models that are then converted into FE models [11,12, 13].

Validation is the second stage of CAE which meanscomparing the behavior of the model with data of the ana-lytical and experimental in vitro or in vivo investigations.In vitro validation allows the loads and boundary conditionsto be carefully controlled in order to assess the validity ofthe model’s geometry and elastic properties [12]. A combi-nation of in vitro and in vivo experimentation potentiallyoffers the best validation which leads to the third stage ofCAE process – optimization. As a result dental construc-tions with optimal design can be produced with optimaltechnological regimes.

The digitalization and the computers developmentplayed leading role in the CAE implementation into thebiomechanical investigation of dental constructions. CAElet to make the engineering calculations and analysis with-out manufacturing of physical model, resulting in optimaldesign of dental constructions produced with optimal tech-nological regimes in considerably reduced time and costs.

2. DigitalizationAs a result of the digitalization the first CAD–CAM

systems for application in dentistry were created in 1970s[16, 17]. In the first CAD stage the geometry of the parts,which should be produced, is defined. While during the sec-ond, CAM stage, the information for the production ismerged and mostly the control of the production machinesis made [18]. So, the all CAD-CAM systems have threefunctional components: 1) a digitalization tool (scanner) thattransforms geometry into digital data that can be processedby a computer; 2) software which processes scanned dataand produces a data set readable by a fabrication machine;3) a manufacturing technology that takes the data set andtransforms it into the desired product by fabricating the res-toration [17, 19].

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Fig. 1. First stage of the CAD-CAM systems development. Plaster model – a), scanning of the plaster model –b), virtual 3D model – c), 3Dprinter and stereo lithography process – d); 3D polymer model – e), casting wax up – f), ascasted dental bridge – g).

On the first stage of the CAD development the datafor the 3D model are obtained by indirect scanning of theplaster model (Fig.1). In this case the first operations formanufacturing of a dental construction are manually doneby the dentist (taking an impression) and the dental techni-cian (pouring the plaster model). After that the plaster modelis scanned by contact [13, 15] or the more modern contactless scanning methods [11, 12]. Using scanned data the vir-tual 3D model is generated with specialized software whichis then transferred to the CAM unit for manufacturing. Thus,the real dental construction can be made of porcelain bymilling, or the polymer casting model - by stereo lithogra-phy (3D printing) [17].

On the next stage of the CAD development the dataare obtained by direct scanning of the prosthesis area in the

patient’s mouth (Fig.2). This stage is a result of the recentintroduction of the intra-oral scanners. Thus the process ofgenerating the 3D model is shortened several times as wellas the accuracy of dental restoration arises, because the firstmanual operations are eliminated. Now there are many soft-ware packages available for the design of dental crowns,bridges and partial denture frameworks, as some of themcan survey, design and wax a partial denture framework inless than 20 min [17].

The development of CAM unit leads to direct manu-facturing of the real dental construction (Fig.2). It can bedone by milling of sintered porcelain and metal alloys withultrasonic machine which ensures very smooth surfaces andhigh accuracy, or by selective laser melting machine, guar-anteeing predetermined surface roughness.

Fig. 2. Second stage of CAD-CAM development: direct scan with intraoral scanner – a), virtual 3Dmodel – b),selective laser melting machine – d); dental bridge made of Co-Cr alloy by SLM process – e).

a)

b)

c)

d)

e)

f)

g)

a) b) c) d)

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The further development ofthe CAD-CAM systemsas a whole is the transition from the closed to open accesssystems, which means that the componentparts of a CAD-CAM system can be purchased separately. As a consequencethe following advantages can be ensured: 1) the data canbe obtained from different sources; 2) appropriate designsoftware can be used for 3D modeling of different dentalconstructions;3) the mostappropriate manufacturing tech-niques can be selected for wide range of materials [17].

Due to the digitalization and exponential develop-ment of computers the CAD-CAM systems were imple-mented in dentistry. Their development from closed to openaccess gives opportunities for fast production of dental res-torations from direct scan of the prostheses field, generat-ing of 3D model and direct manufacturing of the real con-struction. This approachleads to more flexibility ofCAD-CAM systems, elimination of manual operations, increaseof the constructions’ accuracy and decrease of their produc-tion time and cost.

3. Subtractive/additive technologiesThe first CAD-CAM systems in dentistry are based

on the process of subtractive manufacturing in which therestoration is produced from a prefabricated block withguaranteed properties by cutting or milling with bursor dia-mond disks on conventional numerical controlled millingmachine [17, 19, 20]. Subtractive processes characterizewith carefully planned tool movements to cut the material.This technology is used in dentistry for manufacturing ofmetallic and ceramic crowns. The main advantage of thesubtractive fabrication is that the complexshapeswhich aredifficult or impossible to make by the conventional dentalprocesses can be effectively created in reduced time. Nowa-days new highly sophisticated technologies are developed:electrical discharge machining, electrochemical machining,electron beam machining, photochemical machining, ultra-sonic machining and so called laser “milling” (material re-moval by laser ablation) [17, 21, 22].

But there are still some limitations, concerning to:1) the precision fit of the inside contour of the restorationwhich depends on thesize of the smallest usable tool; 2) thewaste of considerable amount of raw material, as in somecases approximately 90 percent of the initial bock could beremoved [17]; 3) abrasion wear of the milling tool and itsshort running cycles; 4) microscopic cracks on the ceramicsurfaces due to machining of the brittle material [19].

They can be overcome by using of Additive Manu-facturing (AM). American Society for Testing and Materi-als (ASTM) defined additive manufacturing as: „the proc-ess of joining materials to make objects from 3Dmodel data,usually layer upon layer, as opposed to subtractive manu-facturing methodologies” [17, 23].

AM technologies produce parts by polymerisation,fusing or sintering of materials in predetermined layerswithout need of tools, thus enable production of geometriesthat arealmost impossible to produce using other machin-ing or moulding processes and nearly with no waste. Thelayers of all AM parts are created by slicing CAD data withspecialized software. Each sliceis then printed one on topof the other to create the 3D object – the so called “3 Di-mensional printing” process [17, 24]. These processes arealso known as “layered manufacturing”, “freeform fabrica-tion”, “rapid prototyping”, “rapid manufacturing” [23, 25].

Additive manufacturing processes started to beusedin the 1980s when Hull invented stereo lithography (SLA)- the first 3D printing technology [26]. The earliest appli-cations of these technologies were mainly for manufactur-ing of prototypes, models and casting patterns. That is whythis process was called “Rapid Prototyping”(RP). But to-day the additive manufacturing technologies are usedthroughout the whole product cycle: from pre-production,i.e. rapid prototyping, to full scale production, known asRapid Manufacturing (RM) [17, 23, 24, 27].

The ASTM International committee, dedicated to thespecification of standards for AM, formed in 2009 (knownas ASTM F42) created a categorization of all 3D printingtechnologies into seven major groups [25]. According to itthe 3D printing technologies with application inbiomaterials are as follows: 3D plotting/direct ink writing,laser-assisted bioprinting, selective laser sintering, stereo li-thography, fused deposition modeling, robotic assisteddeposition/robocasting.

The additive manufacturing processes mostly used indentistry include: stereo lithography, Fused DepositionModeling (FDM), Selective Electron Beam Melting(SEBM), laser powder forming (selective laser sintering,selective laser melting), inkjet printing [17,19, 28].

During the stereo lithography process (Fig.3) a con-centrated beam of UV light is focused onto thesurface of atank filled with liquid photopolymer and, as the light beamdraws the object onto the surface of the liquid,each time alayer of resin is polymerized or cross linked. Thedetail isbuilt up layer by layer, to give a solid object [17, 19, 24,28]. At first SLA was used in medicine and dentistry forproduction of physical models of the human anatomy,forplanningof surgical procedures and as a means of construct-ing customized implants such as cranioplasties, orbitalfloors andonlays. Nowadays the application of SLA proc-esses is extended to manufacturing of surgical guides forplacement ofdental implants, temporary crowns and bridgesas well as resin models for loss wax casting [17, 19].

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Fig. 3. 3D printer and stereo lithography process – a) and various dental constructions manufactured by it – b)and c).

The process of fused deposition modeling charac-terizes with extruding of the thermoplastic materialsthrough heated nozzle or the material is fed from a reser-voir through a syringe. Depending on the strength and ther-mal properties several types of polymers are used: acrylo-nitrile butadiene styrene (ABS) polymer, polycarbonates,polycaprolactone, polyphenylsulfonesand waxes. Duringmanufacturing process a water-soluble material is used fortemporary supports. This technology is mostly used forproduction of wax patterns for subsequent casting [19, 29].

By selective electron beam meltingnear net shapemetal parts can be produced. Theparts are manufacturedby melting of metal powder layerper layer with an elec-tron beam in a high vacuum [17]. This technology permitsproduction of porous structures from biocompatible met-als and alloys such as commercially pure Ti, Ti-6Al-4V al-loy and Co-Cr alloys. But the accuracy of SEBM is in therange of 0,3–0,4 mmand the surface finish tends to berough with an Ra value in therange of 25 µm. So, this tech-nology is applied mainly in production of customized im-plants for orthopedics and maxillofacial surgery and is notgood enough for crown and bridges frameworks [17].

Laser powder forming technique consists of two

processes - Selective Laser Sintering (SLS) and SelectiveLaser Melting (SLM). In this technology layers of particu-lar powder material are fused into a 3D model by adoptinga computer-directed laser [19]. When processing polymersand ceramic the term of“selective laser sintering” is used,whereas the processes for manufacturing of metals andmetal alloys are known as “selective laser melting” (Fig.4)or “Direct Metal Laser Sintering”(DMLS) [17, 24].Thistechnology is very attractive for dentistry, particularly forprosthodontics, because a large variety of materials can beused as building materials – thermoplastic polymers, invest-ment casting wax, metallic materials (Ti and its alloys, Co-Cr alloys, stainless steel), ceramics and thermoplastic com-posites. When using polymers and composites, facial pros-thesis, functionally graded scaffolds and customized scaf-folds for tissue engineering can be produced by SLS. Whileusing of metals and alloys, orthopedic and dental implantseven with porous surface [17, 30], dental crowns andbridges as well as partial denture frameworks can be manu-factured by SLM [31-34]. During production process manyconstructions can be packed in one powder bad (Fig.4), thusensuring high productivity of the laser powder forming tech-nique.

A B

C

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Fig. 4. Possibilities of the SLM technology: dental constructions made of Co-Cr alloy – a) and skull with porousstructure made of Ti – b).

In inkjet printing technology an extremely small inkdroplet is ejected towards the substrate. Different substancescan be used as ink -aqueous solution of coloring agents andbinders to a ceramic suspension, such as used in some stud-ies to produce zirconiadental restorations [17, 19, 35]. An-other variant of the inkjet printing technology is thatbuildsup layer by layer by depositing droplets of a polymer andeach formed layer is cured by UV light [17].This technol-ogy found wide range of dental applications for reproduc-tion of dental models, orthodontic bracketguides, surgicalguides for implant placement, mouth guards and sleep apneaappliances.

Additive manufacturing technologies offer a numberof advantages over subtractive technologies and traditionalmethods of production: 1) the objects with complex geom-etry can be produced, without need of any complex machin-ery setup; 2) the method of production is a controllable, easyand relatively quick process; 3) the objects can be made ofthe same or different materials and depending on the tech-nological regimes the desired properties can be obtained;4) due to the great variety of the additive manufacturingprocesses various materials can be used for production ofdifferent dental constructions for application in many fieldsof dentistry. The undoubted advantages of the additive tech-nologies led to their exponential development and wide ap-plication in dentistry last decade.

CONCLUSIONThree are the main trends in the development of the

technologies for production of dental constructions last 30years - digitalization, simulation and implementation of theadditive technologies.

As a result of the digitalization the first CAD–CAMsystems were created in 1970s. In this mode of operation

at first virtual 3D model is generated by CAD, which thenis used for production of the real construction by CAM. Onthe first stage of development the data for the 3D model areobtained by indirect scanning of the plaster model. On thenext stage the data are in result of direct scanning of theprosthesis area in the patient’s mouth. Implementation ofCAD-CAM systems in dentistry led to elimination of manymanual operations, increase of the constructions’ accuracyand decrease of the production time and costs.

Computer aided engineering is an intermediate unitin the CAD-CAM system, which is intended to simulate theperformance of the construction in order to improve its de-sign. It consists of three processes: simulation, validationand optimization. Using the CAE helps dentists and dentaltechnicians to create the optimal construction concerning tomechanical properties and accuracy and to manufacture itby the optimal process.

In the late 1980sthe new approach to the productionof constructions appeared - by addition of material layer bylayer. The additive technologies were developed, whichcharacterize with building of one layer at a time from a pow-der or liquid that is bonded by means of melting, fusing orpolymerization. Stereo lithography, fused depositionmodeling, selective electron beam melting, laser powderforming and inkjet printing are the methods, mostly usedin dentistry. Their advantages include: production of com-plex objects of various materials - polymers, composites,porcelains, metals and metal alloys; manufacturing of partswith dense structure and predetermined surface roughness;controllable, easy and relatively quick process. Due to thegreat variety of the additive manufacturing processes andthe various materials used, different dental constructions canbe produced for application in many fields of dentistry.

AcknowledgementsThe present study is supported by the project with contract B02/19, 12 Dec 2014, of the Fund for Scientific In-

vestigations, Ministry of Education and Science.

A B

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Abbreviations:AM - Additive ManufacturingASTM - American Society forTesting and MaterialsCAD - Computer Aided DesignCAE - Computer Aided EngineeringCAM – Computer Aided ManufacturingCT- Computed TomographyDMLS - Direct Metal Laser Sintering

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Address for correspondence: Assoc. Prof. Dr. Tsanka Dikova,Vice Dean, Faculty of Dental Medicine, Medical University - Varna55, Marin Drinov Str., Varna 9000, Bulgariamob. tel.: +359 899 883 125E-mail: [email protected]

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Please cite this article as: Dikova T, Dzhendov D, Simov M, Katreva-Bozukova I, Angelova S, Pavlova D, Abadzhiev M,Tonchev T. MODERN TRENDS IN THE DEVELOPMENT OF THE TECHNOLOGIES FOR PRODUCTION OF DEN-TAL CONSTRUCTIONS. J of IMAB. 2015 Oct-Dec;21(4):974-981. DOI: http://dx.doi.org/10.5272/jimab.2015214.974

Received: 12/09/2015; Published online: 03/12/2015