Computer design systems in dentistry cad cam. CAD-CAM Technology in Modern Dentistry

MANUFACTURING OF DENTAL PROSTHESES USING CAD/CAM TECHNOLOGIES IN ORTHOPEDIC DENTISTRY

MANUFACTURING OF DENTAL PROSTHESES USING CAD/CAM TECHNOLOGIES IN ORTHOPEDIC DENTISTRY

Prof. T.I. Ibragimov, Assoc. ON THE. Tsalikova

The promise of CAD/CAM technology in dentistry lies in the fact that it makes it possible to manufacture dentures in one visit, practically in front of the patient, and at the same time do without a dental technician. The main advantage of this technique lies in the method of processing the material for restoration - the so-called cold processing. Cold processing (milling) is more gentle and allows you to keep the specified properties of the material unchanged.

At present, the technique of modeling and manufacturing precision parts for various purposes using CAD / CAM technologies has found wide application around the world, including in dentistry.

Abbreviation CAD means computer simulation, CAM- computer-aided production of prostheses.

In 1970, the idea of ​​automated manufacturing of dental restorations was born. It took more than 10 years to implement it, and in 1983 in Paris, at the International Congress of Dentists, a restoration was demonstratively made using a CAD / CAM system for the first time. The patient was Madame Duret, wife of Francis Duret, the developer of the then fantastic idea of ​​using computer modeling for the manufacture of structures in dentistry. The idea was implemented jointly with Henson International. This is how the Duret system for computer modeling and fabrication of restorations was born.

Almost in parallel with this, the Swiss Cerec system was being developed. The developers are Verner Moermann and Marco Brandestini.

The Duret system still exists, however, unfortunately, it did not find a worthy place in the dental market.

This was the beginning of the era of CAD / CAM technologies in dentistry. At present, each year, not one, but several new systems declare themselves.

For some time, two directions, symbolizing the innovative development of dentistry, existed in parallel, but it was obvious that sooner or later they would intersect. The manufacture of suprastructures on implants by computer milling is already widely practiced in the clinic of orthopedic dentistry. Single crowns and bridges of various lengths are produced by almost all CAD/CAM systems.

Listed below are the CAD/CAM steps that need to be used to fabricate dentures using this technology.

Getting information about an object. This can be done with an intraoral camera, a stationary scanner, or a contact profilometer.

Processing the received information by a computer program and transferring the data into a coordinate system.

Virtual modeling of restorations on a computer using a virtual catalog and special software.

Fabrication of virtually simulated restorations using a milling machine.

OBTAINING THE OPTICAL IMPRESSION

To obtain an optical impression from the prepared tooth or model, intraoral cameras or stationary scanners are used. The intraoral camera is designed to receive information directly from the oral cavity, and its use eliminates the steps of taking an impression and casting a model. Thanks to this, the principle of manufacturing restorations in one visit in the presence of the patient is implemented. When using a stationary scanner, this advantage is lost, but it becomes possible to have a centralized laboratory for the manufacture of CAD/CAM restorations.

For modern cameras and scanners, the accuracy of reading information reaches 25 microns. According to the literature, an edge clearance of less than 100 µm is acceptable. Scanning is done using laser radiation or polarized light. Advantage of modern collinear scanning technology

is that the incident and reflected rays propagate along the same axis. This eliminates the formation of dead zones, i.e. dark areas, however, it makes it difficult to read information from diverging walls due to the large distance between the scanned points. AT Russian system"OpticDent" beams diverge at an angle of 90°, the angle of divergence is 8-9° in a vertical position.

As the scanning depth increases, the beam scatters, which degrades image accuracy. In modern optical systems used in dentistry, the scanning depth reaches 1 cm. In this case, the camera should be as close to the tooth as possible. To improve the quality of the optical impression, it is better to take pictures in several projections. From this point of view, it is more convenient to use a stationary scanner.

When scanning the working surface of the model, the area of ​​the working surface of the scanning head must be greater than the projection area of ​​the object under study. This is fairly easy to determine with a diffraction grating built into the camera. It projects several parallel stripes onto the tooth. The restoration is modeled as a set of cross sections for a series of longitudinal coordinates.

When taking an optical impression in the oral cavity, there are certain clinical features that should be considered when working with an intraoral camera. First of all, they are associated with hand trembling in the process of obtaining an impression (image) and the difficulty of correctly positioning the camera in relation to the object.

In this regard, the illumination of the object is of great importance. It does not depend on the projection of the stripes, since the stripes can be blurred when the hand shakes. In addition, the type of lighting is important: constant or pulsed. Pulsed lighting allows you to neutralize the negative effects of hand shake to a greater extent than constant lighting. To obtain a high-quality optical print, it is also desirable to minimize the shooting time.

The most important condition for obtaining a high-quality optical impression is the correct OD, taking into account the optical capabilities of the camera or scanner. Before taking an optical impression, to reduce glare, the surface of the subject is covered with aqueous solution polysorbate for uniform adhesion of subsequent

anti-reflective layer, and then coated with an anti-reflective layer of TiO 2 powder and take an optical impression. After evaluating the quality of the obtained optical print, all information about the geometric dimensions of the object is converted into a coordinate system and processed using a computer program.

The next step in the manufacture of CAD/CAM restorations is modeling anatomically shaped tooth. You can use the database for this. computer program, containing standard forms of teeth, or a catalog of teeth created individually. The doctor can also create a personal catalog of teeth.

The best option for modeling the anatomical shape of the tooth is to use the model of the initial situation before destruction or preparation as a template, or a symmetrically located tooth using the mirror reflection function. In various CAD/CAM systems, individualization of the tooth shape occurs in different ways. In modern systems, there is a function to automatically fit the margin of the restoration to the line of the tooth preparation. Fitting can also be done manually. The density of proximal and occlusal contacts also lends itself to adjustment.

At the same time, the parameters of the thickness of the restoration depending on the material of manufacture are included in the database. In the case of modeling crown frameworks, instead of the anatomical shape of the tooth, the thickness of the restoration is set according to the material chosen for its manufacture. When modeling with the help of software frameworks of bridge prostheses, the shape and spatial position of the intermediate part are set.

Milling. To mill a denture structure, a standard block of material is clamped in the machine, selected depending on the size and length of the structure. Then proceed to the calibration. The material is processed with diamond or carbide cutters. Older machines used two discs, then a disc and a cutter, and now 2 cutters are used on newer machines. The minimum cutter diameter is 1 mm. This means that the thickness of the scanned tooth must be at least 1.2 mm. For example, in the Hintell system (Germany) 12 cutters were used, of which the computer itself selects 2 cutters of the diameter required for a particular situation.

Milling of metal is carried out with carbide cutters, and other materials with diamond cutters.

The quality of milling depends, among other things, on the number of rotation axes in the machine. AT modern systems there are 4-5 of them. The use of water cooling or oil lubrication in the process of turning the restoration allows you to simultaneously precipitate a suspension of material particles in the air, cool the restoration and lubricate the working surface.

Laser sintering. Currently, the principle of laser sintering of metal powder is used. This method is used in the processing of chromium-cobalt alloy, since its milling is associated with a large consumption of cutters and time. The sintering mechanism involves the application of metal powder on a rounded plate. The virtual model of the design of the denture is conditionally divided into 50 layers, and, accordingly, each layer is sintered metal powder according to the principle “we sinter here - we don’t sinter here”, until the denture is completely sintered. By the same principle, it is possible to make not only crowns and bridges, but also clasp prostheses.

Materials:

Zirconia (Y-TZP ZrO 2 HIP), Ti, Fu;

Zirconium oxide (fully sintered and semi-sintered);

Glass ceramics (shrinkage after re-firing reaches 25%);

Ceramics;

Composites (for temporary crowns);

Chrome-cobalt alloy, which includes additives of manganese, tungsten, molybdenum, iron, cadmium;

Titanium alloys;

Titan etc.

Thus, the fundamental difference between materials for the manufacture of dentures using CAD / CAM technology lies not only in the chemical composition of the blanks, but also in the phase state of the material used.

CAD/CAM restorations for prosthetics on implants. The history of modern dental implantation goes back over 50 years. It all started when Ingvar Brånemark, in the process of studying microcirculation in bone tissue using a titanium observation chamber embedded in the vital bone, discovered an unusual fusion of metal with bone tissue and formulated the concept of osseointegration. Later he developed the basic principles of dental implantation.

The first step is always to obtain information about the object. Information can be obtained both optically and tactilely, as, for example, in the Procera system. If the system has an intraoral camera, as in the Cerec and Duret systems, this information can be obtained directly from the oral cavity from both natural and artificial supports. The procedure is identical to the manufacture of conventional restorative crowns on natural teeth. The abutment installed in the oral cavity and the tissues surrounding it are coated with anti-reflective powder, after which an optical impression is obtained. If an implant with a separate suprastructure is used, the screw hole in the abutment is pre-sealed. The second picture is taken in order to register occlusal contacts, after which a virtual modeling of the restoration is performed, which is then made in the grinding block.

This method allows you to make a frameless ceramic restoration in one visit.

Another option for manufacturing an orthopedic structure is indirect scanning using a stationary scanner. After that, a model is made with implant analogues and abutments are selected. The finished model is scanned and the restoration is made.

When using such laboratory systems as "Everest", "Cerec inLab" and others, it is allowed to manufacture frame ceramics, including bridges.

The third option for the production of restorations is the CAM fabrication of structures. In this case, the stage of virtual modeling is absent, but double scanning is performed. First, a model with an abutment is scanned, then a wax or plastic replica of the design, made according to traditional technology in dental laboratory. Next, the restoration is made in a grinding block.

A few years ago, when evaluating the effectiveness of implantation, aesthetic parameters were not taken into account at all. Only the degree of osseointegration and the functionality of implant-supported structures mattered. However, due to the growing requirements for aesthetics, individual abutments are increasingly being used, which allow taking into account the characteristics of the gingival mucosa, the direction of the implant axis, and bite. With their help, a large number of

number of highly aesthetic designs. However, there are disadvantages traditional for the casting technique: the possibility of underfilling, the formation of internal pores, and the lack of a guarantee of metal quality. From the point of view of the safety of the soft tissues surrounding the implant, the possibility of removing residual cement and for hygienic reasons, the shoulder of the abutment should not be located below the level of the marginal gingiva. However, when it comes to implantation in the area of ​​the anterior teeth, the level of the shoulder is dictated by aesthetic considerations. With a transparent thinned mucosa, the edge of the metal abutment can create gray shadow in the cervical region. In addition, in the manufacture of metal-free structures covering implants, it is more logical to use metal-free abutments, since one of the conditions for ensuring the aesthetics of implant-supported restorations is a harmonious combination of mechanical, biological and aesthetic properties of structural materials.

Currently, manufacturers of implantation systems offer zirconia abutments as a standard blank complete with a fixing screw. Abutments are corrected by a technician. It is possible to mark the abutment and grind it with diamond or carborundum tools.

With the expansion of the software functions of CAD / CAM systems, it becomes possible to produce not only superstructures on implants, but also the abutments themselves. The advantage of the technique lies in the possibility of virtual modeling of the shape of the abutment, taking into account the features of the relief of the mucous membrane and other aesthetic and functional requirements.

Currently, there is a tendency to combine the efforts of manufacturers of implant and CAD/CAM systems. An example is the collaboration between Straumann and Sirona, which resulted in a joint project "CARES" (Computer Aided Restoration Service), and Astra-Tech and Atlantis, which also announce the joint production of abutments not only from zirconium oxide, but also from titanium, as in Procera system and others.

Conventionally, there are two methods for the automated production of zirconium oxide abutments: CAD/CAM production, which includes virtual modeling of the design, and CAM production, which replicates a wax or plastic blank made by a technician.

On the example of the CARES system, we will consider the first option.

Necessary equipment: Sirona inLab system, inEos stationary scanner, special abutment blanks for scanning, the diameter corresponding to the implant. The option of using a temporary abutment with a temporary restoration for the preliminary formation of soft tissues is considered optimal.

After taking an impression and obtaining a master model, another model is made from scan plaster with a scan abutment installed. They scan the abutment, as they say, in situ either in "inEos" or with the laser scanner of the "inLab" system. It is also possible to scan in the oral cavity with an intraoral SD camera. Then the procedure resembles the modeling of a bridge prosthesis. Outline the perimeter of the abutment and carry out further modeling. This requires an abutment design program.

The best option is to use a silicone index or a temporary structure during the modeling process.

Care must be taken to ensure that the thickness of the implant-covering restoration is uniform.

Using the Procera system as an example, it is possible to demonstrate the CAD manufacturing of abutments. The first part of the procedure is similar to the fabrication of individually cast abutments. Abutment blanks are available to match the implants, which are individualized in the dental laboratory. After that, they are scanned. In the Procera system, the scanner is tactile. After converting the received information and reproducing the individual model of the abutment on the screen, it is installed in a virtual cylinder to correlate with the block from which the finished abutment will be ground.

CAD / CAM translated from English - computer-aided design / computer-aided production (CAD). It has been used since the 80s in the manufacturing industry for the production of precision machine tools, various parts and vehicles. Over the past couple of decades, CAD / CAM technologies have been increasingly used in dentistry and dental practice.

CAD / CAM technologies are used by dentists and dental laboratories in conjunction with metal-free materials to manufacture milled ceramic crowns, all-ceramic bridges, veneers and inlays. CAD / CAM technologies are also used in dentistry in the manufacture of abutments for dental implants.

As the various materials and innovative technologies applied to CAD/CAM systems have improved over the years, this moment high-quality dental restorations have appeared, which are widely used by dentists and dental technicians in prosthetics. Today, dental restorations made using CAD/CAM technology have best performance fit, they are more durable and have more natural look(colorful and translucent, similar to natural teeth) than dentures made without the use of computer modeling and production.

Stages of using CAD/CAM systems in dental laboratories

CAD/CAM technologies are available for dental practice, which allows laboratory assistants and dental technicians to design restorations directly in a computer program.

1. At the first stage in the CAD/CAM-system, the computer displays a 3-dimensional image of the restored tooth or several teeth obtained by scanning with an optical scanner. In addition, 3-D images can be obtained by scanning a traditional model obtained from conventional casts.
2. The resulting 3-D images are used in special software for modeling and finalizing the restoration. The amount of time the technician needs depends on his skill, which has practical experience and complexity of the entire treatment process. In some cases, this process may take only a few minutes. In others, it may take half an hour or more to guarantee the perfect quality of the final work.
3. After the modeling is completed, the developed crown, inlay, onlay, veneer or bridge is milled from a single piece of ceramic material on a special computer machine (grinding chamber).
4. To give the denture a more natural look, it can be covered with ceramics.
5. At the penultimate stage, the workpiece is placed in a furnace and fired.
6. After firing and hardening of the material, the restoration is finally ground and polished.

Advantages of CAD/CAM technologies

Research and experience show that modern milled dental CAD/CAM restorations are stronger than work performed without computer-aided design and computer-aided manufacturing. They have a longer service life.

One of the advantages of CAD/CAM technology is that dentistry with the right equipment is able to offer the patient to restore the tooth in one visit.

CAD/CAM dental systems such as CEREC can be used to fabricate inlays, crowns or veneers in just one visit to the dentist.

If your dentist has the ability to make a prosthesis using CAD / CAM technology, then for the patient this is a great opportunity not to make traditional impressions and get by with just one visit to the laboratory. Another plus is that the patient will only be given a single local anesthesia for prepared teeth. An exception to this situation is the all-ceramic bridge, as it is created in laboratory conditions using CAD/CAM technology. All-ceramic bridge restorations require a return visit to the clinic for placement. In such cases, temporary restoration will be necessary.

The subtleties of using CAD / CAM systems in dentistry

CAD/CAM technology is not a substitute for the professionalism, precision and talent of dentists and dental technicians. Using computer-aided design and manufacturing, dentists are bound to be highly skilled in creating initial tooth preparations; dentists and technicians must be precise when creating a digital impression and image of a restoration.

Also important is the accuracy and skill with which dental technicians model future prostheses. This is especially important and critical to preventing future damage to the tooth. For example, poorly designed crowns, veneers, inlays, and onlays can leave gaps between teeth or between a tooth and a restoration. This can lead to an increased risk of infection or illness.

When are CAD/CAM systems used in dentistry?

It should be noted that not every case of prosthetics can be performed using CAD / CAM systems. Only the dentist can determine whether it is possible to use computer technology to work with each specific case. In addition, despite the improved esthetics of the materials used in CAD/CAM manufacturing today, patients may find that some CAD/CAM restorations appear too opaque or unnatural.

Depending on the restoration option, the dentist may suggest more primitive fabrication methods, which include more manipulations for precision manufacturing and fitting. Therefore, patients should discuss each individual case and their preferences with their dentist. Only a dentist can make the final decision in the technique and technology of prosthetics, based on a thorough examination.

Cost of CAD/CAM restoration

All-ceramic restorations, including those fabricated in a dental laboratory using CAD/CAM technology, have high cost. However, in some cases, the high cost of the materials used is charged to the clinic or laboratory and is not reflected in the patient's bill.

The final price for a prosthesis made using CAD can vary from several thousand to several tens of thousands of rubles.

Candidate of Medical Sciences, Orthopedic Dentist Yervandyan Harutyun Geghamovich

Publication date — 4.10.2015

Since the invention of the computer by man, a new era has come in science, technology and simply in human life. While most people are able to use computers to the maximum to communicate in in social networks, skype and online shopping, others have long used computers to perform complex mathematical measurements, 3D design, programming, study the strength of materials and fatigue loads, as well as in the field of CAD/CAM technologies. CAD/CAM is an acronym that stands for computer-aided design/drafting and computer-aided manufacturing , which literally translates as computer help in design, development and computer assistance in production, but in terms of meaning it is production automation and computer-aided design / development systems.

With the development of technology, orthopedic dentistry has also evolved from the time of the bronze man, when they were tied artificial teeth gold wire to neighboring teeth, before modern man which uses CAD/CAM technology. At the time of the advent of CAD / CAM, the main technologies for the manufacture of crowns and bridges were the old and flawed stamping and soldering technology, the more promising and advanced casting technology, and the less common technologies, also devoid of the disadvantages of stamping and soldering, superplastic molding and sintering. On the other hand, the latter two technologies can be applied to a very limited number of materials, such as superplastic forming only for titanium. CAD/CAM technology is devoid of all the disadvantages inherent in casting technologies, such as shrinkage, deformation, including the extraction of cast crowns, bridges or their frameworks. There is no danger of technology violations, for example, overheating of the metal during casting or reuse of sprues, which leads to a change in the composition of the alloy. There is no shrinkage of the frame after applying ceramic lining, possible deformation when removing wax caps from a plaster model, pores and shells during casting, unspilled areas, etc. The main disadvantage of CAD / CAM technology is the high cost, which does not allow this technology to be widely orthopedic dentistry. The original CAD/CAM technology was a computer with the necessary software on which 3D modeling was performed fixed prosthesis followed by computer milling with an accuracy of 0.8 microns from a solid metal or ceramic block.

Respectively, consumables for this procedure, expensive blocks and cutters, mostly carbide, became. Thanks to the further evolution of CAD / CAM technology, computer milling was replaced by 3D printing technology, which made it possible to reduce the cost and made it possible to manufacture objects of any shape and complexity that could not be produced before by any of the existing technologies. For example, thanks to 3D printing, it is possible to produce a solid hollow object with any shape of the inner surface. In relation to orthopedic dentistry, it is possible to make a hollow body of the prosthesis, which will reduce its weight without reducing the strength of the structure. The uniqueness of 3D printing technology can be seen in the video.

In dentistry 3D printing method depends on the printed material and therefore the technology itself can be conditionally divided into several branches:

1. Wax printing
2. Plastic printing
3. Metal printing
4. Plaster/ceramic printing

First branch It's 3D printed with wax. It refers to thermal printing technology, i.e. the wax heats up and turns into liquid state, and accordingly in this state it is applied drop by drop. After application, it cools down and turns into a solid state. In fact, this method is a more advanced technology for modeling prosthesis structures with all the disadvantages of casting inherent in it. Those. you can model on a computer and print the perfect frame from wax, but when casting, you will again encounter all the problems inherent in casting. Thus, this technology eliminates all the disadvantages of modeling a wax frame, but does not eliminate the disadvantages of casting technology.

Second branch This is 3D printed plastic. This technology makes it possible to obtain both collapsible models of the jaws, frameworks made of ashless plastic for casting, as well as finished prostheses, such as crowns or bridges made of composite, as well as printing removable prostheses.

In turn, there are two methods of 3D printing with plastic:

1. tolerating
2. Light curing printing

Thermal printing can be used for 3D printing with thermoplastics, such as removable dentures, or for printing with ash-free plastics. Light-curing printing can be used to print both crowns made of composites and frameworks made of ashless plastic, removable dentures made of acrylates and polyurethane.

The technology of wax and plastic thermal printing is similar and somewhat similar to the printing principle of a conventional color inkjet printer. The material is heated to the melting temperature and applied with microdroplets, but unlike a color inkjet printer that prints only in one plane, a 3D printer prints in three planes and, accordingly, not with paint, but hard materials. Due to the application of the material with microdroplets, complete compensation of material shrinkage is achieved. In addition, there is another method of thermal plastic printing, in which a plastic wire is heated and continuously fed to the surface of the printed object (FDM 3D printing). This technology is the cheapest and most common in the world, but it has not found wide distribution in dentistry, since it does not have high accuracy.

A more advanced method of thermal printing is selective thermal sintering technology. SHS» (Selective Heat Sintering). A detailed description of the method is presented in the Metal 3D Printing section.

photopolymer printing

There are 2 ways of photopolymer 3D plastic printing in dentistry:

1. Stereolithographic 3D printing (SLA)

Inkjet photopolymer 3D printing (MJM)

Light polymerization (photopolymer) printing is similar to thermal printing and differs only in that the material does not need to be heated, since it is already liquid, and hardening i.e. polymerization occurs under the influence of light blue spectrum 455-470 nm.

Stereolithographic printing (SLA)

A radically different principle is used in stereolithographic printing technology. The essence of the method is to print in a bath filled with photopolymer plastic or composite. Unlike other printing methods, this method prints from top to bottom and the printed object is upside down. Many readers will have a question, how can you print in a bath filled with photopolymer material, since all the material in the bath must be cured. Everything is ingeniously simple. The fact is that the platform on which the growth of the printed object begins is immersed in the thickness of the photopolymer composite, not reaching the bottom by 6-20 microns (depending on the printer), i.e. there remains a layer of photopolymer material with a thickness of 6-20 microns and, accordingly, only this layer is cured in the right places. After curing, the platform rises up, tearing off the cured polymer from the bottom of the bath, then re-immerses without reaching 6-20 microns with the polymerized part to the bottom. Thus, a layer of uncured photopolymer material is again created between the bottom of the bath and the already printed layer. The process is repeated as many times as the number of layers needed to be printed for the complete readiness of the object.

Benefits stereolithographic printing technologies are:

1. High accuracy;
2. High resolution;
3. Smooth surface.

disadvantages stereolithographic printing are:

1. Possibility to print in one color only;
2. Background illumination of the photopolymer, since a small power of light radiation is scattered in total mass photopolymer. Thus, part of the photopolymer material deteriorates, which leads to an increase in the cost of printing;
3. Limited bathroom resource. Due to the fact that the polymer must constantly come off the bottom of the bath, it is made of silicone or a similar material, and over time it fails, and therefore requires replacement;
4. Limited resource of an expensive laser.

Third branch– 3D metal printing. The essence of the method lies in the spot melting of the metal powder with a beam until a homogeneous structure is obtained. There are several ways to 3D print metal:

1. DMD« direct metal deposition» (Direct Metal Deposition);
2. LDT « laser deposition technology» (Laser Deposition Technology);
3. LCT « laser deposition technology» (Laser Cladding Technology);
4. LFMT « free-form laser production technology» (Laser Freeform Manufacturing Technology);
5. LMD « laser metal deposition» (Laser Metal Deposition);
6. LMF « metal laser fusion» (Laser Metal Fusion);
7. SLS« selective laser sintering» (Selective Laser Sintering);
8. DMLS « direct laser sintering of metals» (Direct Metal Laser Sintering);
9. SLM « selective laser melting» (Selective Laser Melting);
10. LC « laser focus» (LaserCusing);
11. EBM « electron beam melting"(Electron Beam Melting);
12. SHS « selective thermal sintering» (Selective Heat Sintering).

Selective laser sintering technology ( SLS) was invented by Carl Deckard and Joseph Beeman of the University of Texas (Austin, USA) in the mid-1980s.
Selective laser melting technology ( SLM) was invented by Wilhelm Meiners and Konrad Wissenbach of the Fraunhofer Institute for Laser Technology (ILT) (Aachen, Germany) together with Dieter Schwarze and Matthias Fokele of F&S Stereolithographietechnik GmbH (Paderborn, Germany) in 1995.

All these methods can be used in dentistry. Conventionally, they can be divided into two groups, differing only in the method of applying metal powder. The first group includes powder feeding methods with simultaneous microwelding. The second group includes methods for applying a layer of powder followed by microwelding of the powder.

Group I of metal 3D printing methods.

3D printing method by direct metal deposition ( DMD) is very similar to the powder laser welding technique. The essence of the method is shown in the diagram.

The laser beam heats the area pointwise and an aerosol of metal powder in an inert gas environment is also fed there. Under the action of the laser, the powder melts and passes into the liquid phase, which solidifies after cooling. Then the process is repeated and in this way the metal is layered drop by drop. In the case of laser welding, everything is done by a dental technician in manual mode. With 3D printing, the process is controlled by a computer, so it is produced as quickly and accurately as possible.

DMD, LFMT, LMD, LDT and LCT methods are no different, the only difference is that LDT and LCT methods are used to restore damaged objects, for example, during abrasion.

II group of metal 3D printing methods.

With the layer-by-layer method, a layer of metal powder having a microscopic thickness (10-50 microns) is applied to the substrate and sintering or, more precisely, microscopic laser welding in an inert gas medium of microscopic metal grains in the necessary areas of the layer. After that, another layer of metal powder is applied on top, and laser microwelding of metal micrograins is performed not only among themselves, but also with the lower layer.

Micro welding of metal powder

Thus, a three-dimensional metal object is printed in layers. After printing is completed, the finished metal object is removed from the powder. The remaining powder can be reused. This technology is waste-free production, which ultimately leads to a reduction in the cost of construction. And thanks to the use of computer technology, high quality and accuracy of the order of 1-10 microns are achieved. The accuracy of the method is limited only by the diameter laser beam and the size of the micrograins of the printed material. But it must be remembered that the higher the accuracy of the print, the slower the print. We bring to your attention a video about 3D metal printing in dentistry.

honors SLS(selective laser sintering) from DMLS(direct laser sintering of metals) lies in the fact that the second method can only be used for metal printing. And by the method SLS can be used for printing with any thermoplastic. SLS from SLM differs only in that in the first case, sintering is performed, and in the second, powder is melted. This difference is conditional, since metal melting also occurs during sintering, and the difference in the name and description of the method is associated with commercial issues. The same goes for the method. LC and LMF. Therefore, the separation of all these methods is far-fetched, although according to the creators of technologies SLS and DMLS The density of the printed object can be adjusted using these printing methods.
electron beam melting (EBM) differs from other methods in that a high-power electron beam (beam) is used instead of a laser beam, and the printing itself is performed under vacuum conditions.
Selective thermal sintering(SHS) differs from other methods in that a thermal head is used instead of a laser or electron beam. This technology makes it possible to create 3D printers. small size. But the downside of the technology is low temperature printing and therefore it can only be used for printing fusible metals and thermoplastics.

Fourth branch– 3D printing with plaster/ceramics. The principle of plaster printing is similar to the technology SLS, but instead of a laser, a bonding agent is used, the so-called glue, connecting the particles of gypsum or ceramics. However, plaster printing did not find use in dentistry, as models began to be printed from plastic. Printing with ceramics is promising and will allow printing frameworks or finished designs of crowns and bridges.

Using an article in a bibliographic list“Yervandyan, A.G.CAD/CAM technologies in orthopedic dentistry[Electronic resource] /Harutyun Gegamovich Yervandyan, 4.10.2015.–

CAD/CAM is short for Computer-Aided Design and Computer-Aided Manufacture. For many years, CAD/CAM systems have been used in various industries, especially in the automotive industry. Computers facilitate all stages of automotive production, from the initial design concept through to the final production of the parts that make up the car. Nowadays, such technologies find a wide variety of applications in medicine and dentistry.

CAD (Design using computer technology)

Design using computer technology is the use computer systems for product design and development. The computer is used as a highly advanced substitute for a drawing board, allowing for three-dimensional modeling and design without pen and ink. A model created in such a system can be shown from any angle, and can also be modeled to view its projection in a specific light. Individual elements of the drawing can be revised, replaced, and the entire model as a whole can be rebuilt. Once the design has been finalized, detailed and dimensional drawings can be printed out for use in the manufacturing process. Or, on the other hand, they can be passed on, and information about the shape of the part can be turned into manufacturing instructions, which will be transferred directly to the machines that manufacture this part.

In particularly progressive systems, it is possible to take into account also structural properties materials. Mathematical modeling of a structure using these values ​​makes it possible to obtain an assessment of certain aspects of its behavior even before it leaves the drawing board. This technology is known as Finite Element Analysis. It is possible to assess the consequences of certain changes in the design in relation to the behavior of the part, even before it is even made in the form of a physical model.

CAM (Computer Based Manufacturing)

Computer-assisted fabrication is the use of computer systems to control power tools. This allows you to give materials a certain shape in order to create structures and fixtures from them. Computers controlling power tools can act according to instructions received from a design system using computer technology. Thus, there is a complete integrated system. The object to be made is constructed on a computer screen, after which the project is brought to life by the computer, which transmits its instructions directly to mechanized tools.

With regard to fillings, dentistry has always been limited to a certain range of manufacturing technologies available. One-visit dental fillings have always been limited to the use of dental amalgam, acid-base mixtures, or resin polymerization. Laboratory-made fillings have been limited to lost wax casting, porcelain agglomeration, and resin polymerization. This severely limited the range of materials that could be used. Giving us new methodology object shape control, CAD/CAM systems in dentistry open up access to whole systems of new materials.

CAD/CAM technology in dentistry makes possible use ceramic materials with very good performance and composite materials based on glass binder, which were produced under optimal factory conditions, while observing the necessary technological characteristics. Such materials have huge advantages over those that are traditionally used here.

Compared to other filling materials, ceramic materials have a number of advantages. They can be mixed in such a proportion that they match the color of the tooth very closely. They have a very high biocompatibility and are very wear resistant. It is also very important that, through appropriate processing of both the ceramic itself and the surfaces of the tooth, it is possible to achieve a strong bond, so that the filling and the tooth itself become a single functional element. This advantage means that a damaged tooth can be strengthened by being bonded to a ceramic filling. Although it is possible to do the same with polymer-based composite materials, these fillings, in terms of their strength, cannot be put next to the manufactured ones. mechanically ceramic fillings.

The range of structural polymers that can be used to create the main body of composite fillings is relatively small. Most of these composite materials are based on BIS-GMA.

Smile - everything will be fine!

The use of CAD / CAM systems in dentistry allows for the design and manufacture of prosthetic orthopedic structures using a computer.

CAD, short for Computer-Aided Design, is used instead of a drawing board and allows you to create a 3D model of dentures.

The advantages of such a design include the following:

• a model designed on a computer can be viewed from different angles and its projection can be studied in a certain light;
• not only individual details of the drawing can be replaced, but the entire model can be redesigned;
• the finished project can be turned into instructions that will be passed on to machines for their consciousness of this detail.

There are state-of-the-art systems that create 3D models based on the structural properties of materials.

CAM or Computer-Aided Manufacture refers to the manufacture of an orthopedic structure by a computer in accordance with a previously designed 3D model.

Capabilities and types of cad/cam systems

Making a dental bridge on a machine

CAD CAM systems allow you to make:

• and various lengths;
• for ;
• provisional crowns.

There are 2 types of CAD CAM systems:

• closed systems that work with a specific consumable, usually produced by one company;
• open systems that work with various consumables from different manufacturing companies.

Stages of prosthetics using CAD CAM systems

Prosthetics using CAD CAM systems is as follows:

1. The dentist prepares one or more teeth. Then he scans the teeth and bite with a 3D camera, as a result of which an optical model is obtained. Ordinary casts can also be scanned.
2. Next, the resulting image is processed with a special program that draws a 3D model of the restored teeth. She chooses the shape of the future restoration herself, taking into account the rest of the teeth, but the doctor can correct the proposed design with the movement of a computer mouse. The amount of time to create a 3D model depends on the skill of the specialist and on the complexity clinical case. This can take anywhere from a few minutes to half an hour or more.
3. When the simulation is completed, the file with the design of the manufactured part is transferred to the control unit of the milling machine. And here, from a piece of solid material, a 3D model of a part is cut, which was previously modeled by a computer. In time it takes about 10 minutes. To make the design look more natural, it can be covered with translucent and reflective ceramics.
4. When used as a material, then the fabricated structure is then placed in a sintering oven, as a result, it acquires the final shade, size and strength.
5. After firing and hardening of the material, the part is ground and polished. Next, you can install the product on the prepared tooth.

Advantages and disadvantages of computer prosthetics

The advantages of using CAD CAM include the following:

The disadvantages include the following:

• not any prosthetics can be performed using CAD CAM systems, whether it is possible to use it in each specific case should be decided by the dentist;
• some restorations may look opaque and unnatural;
• high price.

CAD CAM system allows you to make crowns and bridges to the maximum short time. Therefore, for those who dream of having beautiful and healthy teeth, but does not want to visit the dentist over and over again, it is worth contacting a clinic where such technologies are used.