Dental technology
The dentistry is a craft whose job it is to all types of dental prostheses such as crowns , bridges , partial and full dentures , inlays , orthodontic treatment devices, known as bruxism as well as rails for broken jaws or mouthguards establish for certain sports. Dental technology is therefore an important part of dental treatments.
Dental work is carried out in a dental laboratory (also called a dental laboratory) , which either exists as an independent commercial laboratory or is affiliated with a dental practice .
Commercial laboratory
A commercial dental laboratory is a craft business and as such is a member of the locally responsible Chamber of Crafts. Many companies are also organized through the appropriate guild . In Germany, commercial dental laboratories are required to be a master . So at least one person (usually the owner) with a large certificate of competence must be responsible. Even after the reform of the master craftsman regulations in 1999, numerous skilled trades are still subject to compulsory master craftsmen. This also includes dental technology.
Practice laboratory
Dentists are allowed to maintain a practice laboratory in which dentures are manufactured. In Germany, the prices applicable to practice laboratories for legally insured patients in accordance with Section 57 (2) SGB V are reduced by 5% compared to the prices that commercial laboratories are allowed to charge according to the Federal Standard List of Services (BEL II), since a commercial laboratory - in contrast to the practice's own laboratory - is subject to trade tax . A master dental technician can also be employed in the practice laboratory, but this is not mandatory. In the area of private billing, the practice laboratory can only calculate the proven costs + profit share according to §9, §10 GOZ. The VDZI offers specifications (so-called designation lists ) to calculate the working and set-up times involved.
Cooperation between dentist and dental technician
Close cooperation between the practice and the laboratory is essential. Both the process sequences and the treatment options must be coordinated between the two. In some cases, dental technicians are also involved in try-ins or color selection so that they can get a better idea of the individual. As a rule, several treatment methods are presented to the patient during the dental consultation. Since questions about optics, handling and material often arise in addition to medical questions, there are now also dental laboratories that offer independent information. The close proximity of a dental laboratory to the dental practice is an advantage. The knowledge and ability of the triad of color, form and function is part of the dental production.
Areas of work in dental technology
dentures
Model creation
In almost every job, impressions of the jaws and teeth are the basis for dental work. Depending on the process, alginate , silicone or polyether can be used for the impression . With the help of these impressions, the dental technician creates plaster models (mostly made of hard plaster ), so that he then has the situation that is also given in the patient's mouth. In addition, he creates the positional relationship of the jaws to one another in an articulator by determining the jaw relation (previously: bite registration). Such a jaw relation determination can be a simple wax bite , but also a complex (and expensive) axiography , depending on the type of work to be done and the demands of the dentist and patient .
The models are also prepared differently for the following measures. In the case of an individual impression tray , a registration template (previously: bite template) or a simple prosthesis , you can continue working directly on the model. However, if precious metal work (crowns, bridges, combined dentures , superstructures on dental implants ) are to be made, a saw model is made in which the individual teeth can be processed separately, but can be clearly set back on the model base. In the case of superstructures, the dental technician integrates prefabricated parts that are tailored to the respective implant system into the construction.
Upper alginate impression
Upper jaw silicone impression
Saw model
Superstructure - the cylindrical parts are prefabricated.
Modeling of the (precious) metal parts in wax
The dental technician models a wax model on the tooth stump, which is a true-to-scale reproduction of the tooth ground by the dentist, which corresponds to the later crown or bridge. In addition, a wax sprue is connected to the model, through which the metal can be poured in during casting.
The casting is modeled in wax.
Casting the wax models
The wax model is embedded in a special, plaster-based investment material , which is located within a casting muffle . After hardening, the wax is burned out in a burnout oven. At the same time, the investment material expands to such an extent that the shrinkage of the alloy during cooling is precisely compensated for. An accuracy of fit to the natural tooth of 10 µm is aimed for. The metal is melted by a flame (out of date), electrical resistance heating, induction current or an electric arc and pressed into the now existing cavity of the investment by vacuum pressure casting (previously by centrifugal force: casting centrifugal). It is a lost shape cast . As a rule, larger cast parts are now also cast in one piece (one-piece casting). However, individual parts can also be cast and these can then be connected by soldering , welding ( using an arc or laser ) or adhesive technology .
The casting is embedded.
The wax is burned out in the burnout furnace.
Raw casting, the casting pins have not yet been removed.
Veneering with ceramics or composites
Metal frameworks can be coated with ceramic materials ( veneering metal-ceramic , VMK) in order to make them appear deceptively real compared to natural teeth in terms of shape, surface design and color structure. Light effects of the natural mineral tooth enamel, such as opalescence , fluorescence , translucency , layers of color of different intensity, etc. are built up individually by hand from moist ceramic powder and fired under vacuum at 780 ° C to 900 ° C.
Plastics mixed with ceramic ( composites ) are also suitable for veneering, even if the result does not appear as natural as with ceramic veneering. For this purpose, plastics mixed with ceramics ( composites ) are layered in a kneadable consistency and polymerized with halogen light .
The ceramic mass is composed of several colors,
applied in layers with a brush
and burned again and again.
Partial denture - model casting
In the case of model cast prostheses, a base with the necessary holding and support elements (brackets) is cast in one piece from a chrome-cobalt-molybdenum alloy . Due to the spring force of the clamps or anchors, attachments, bars or telescopic crowns , such prostheses are held in place on the remaining teeth. For casting, a complete model made from a special investment material is embedded, on which the casting was previously modeled in wax. The position of the brackets is measured exactly with a parallelometer , whereby the prosthetic tooth equator is decisive.
On the denture saddles are retentions modeled at which the plastic that simulates the gums, mechanically anchored. The artificial teeth, in turn, are attached to the plastic mechanically, but also by chemical reaction. The industry makes teeth in many different shapes, sizes and colors. The plastic and also the teeth are an acrylate , which is initially available as a powder ( polymer ) and liquid ( monomer ) and polymerizes when it hardens, either with heating in a hot air oven (hot polymerization) or without heat as a cold polymer. For more details see below under Total Prosthesis .
The model casting base has been cast and is removed from the investment mold.
The model casting base in its raw state. The sprues have not yet been removed.
A model casting base on the working model
A completed model cast prosthesis
Partial denture - plastic base
For simple (provisional) prosthesis without denture base, the holding elements are made of V2A - wire with a thickness of 0.7 mm to 0.8 mm bent. The teeth and the plastic parts correspond to those of a model cast prosthesis.
A simple (temporary) prosthesis
Full denture
A full denture is manufactured hand in hand with the dentist. For the production of a full denture (in technical jargon: according to the number of teeth: "14" for one jaw and "28" for both jaws) the technician first creates an individual plastic tray on a simple situation model . The dentist takes a functional impression with this tray . With this impression, the dental technician creates the working model, i.e. the basis for the further work steps. This is followed by the production of bite templates, with the help of which the dentist sets the relationship between the jaws, determines the occlusal plane , and draws in the midline and the so-called smile line. The smile line is the area where the upper teeth are visible when the upper lip is raised slightly. The color and shape of the artificial teeth must now be determined and sent to the technician.
Dental production of the full denture
After the dental technician has set the models in the articulator with these specifications , he sets up the teeth on a wax base (often reinforced by an acrylic plate). The dentist tries this wax-up on the patient and corrects it if necessary.
This prosthesis is then converted into plastic in the laboratory. To do this, the wax model with the denture teeth is embedded in a cuvette. After the plaster of paris has hardened, the wax can be melted with hot water, leaving the teeth in the flask. Various methods are possible for the introduction of the plastic and its hardening:
- Tamping-press method: A dough-like mixture of monomer and powdery polymer is stuffed into the cavity of the two-part, opened curette. Then the cuvette halves are pressed together. Advantage: little effort, disadvantage: inaccuracy of fit due to raised bite .
- Injection process: The machine-mixed plastic is pressed (injected) into the closed cuvette as a hot or cold polymer. Advantage: optimal mixing ratio, disadvantage: high technical effort.
- Casting process: Cold polymer is poured into a pouring flask and polymerized under pressure at approx. 50 ° C in a water bath. Disadvantage: high shrinkage and thus inaccurate fit.
- Injection molding process: an already polymerized thermoplastic (mostly polymethyl methacrylate (PMMA)) is liquefied by heating and placed in an injection cuvette under high pressure. Advantages: no polymerisation shrinkage , so high accuracy of fit. Extremely low residual monomer content. Disadvantages: The denture teeth are not polymerized, so they do not form a chemical bond, but have to be provided with mechanical retentions. High technical effort.
- Melt-press process (Luxene®): Combination of tamping-press and injection technology. Pre-polymerized, heated gel is stuffed into an open cuvette and, after sealing, the plastic is pressed and compacted. The final polymerization takes place in a water bath.
After devesting, the prosthesis is put back in the articulator to correct the occlusion , if necessary , and is then finished and polished.
Individual tray for a toothless upper jaw
Functional impression of a toothless upper jaw
Lower jaw bite template for determining the jaw relation
The plastic teeth are set up on an acrylic plate in wax.
Wax model of a total upper jaw prosthesis
The prosthesis is embedded in the cuvette.
After scalding, the teeth remain in the other half of the flask.
The plastic is pressed into the cuvette using an injection process.
The finished, high-gloss polished upper jaw prosthesis
Inlay fillings
The dental procedure for inlays and onlays (gold cast fillings) largely corresponds to that of the production of crowns and bridges. The production of ceramic fillings also corresponds to the procedure for ceramic veneers, but no metal base is used.
Finishing of a finished cast inlay under the stereo microscope
An onlay is worked out.
Highly polished onlays on the saw model.
Orthodontic appliances
Removable Orthodontic treatment devices (the laity under the terms regulation , braces or brackets are known) either removable appliances (each a pine) or bimaxillary (both jaws) Regulations mono blocks (or rather functional orthodontic appliance ) that act together on both jaws.
Plates are anchored to the remaining dentition with specially shaped wires (e.g. Adam's clamps ). Additional wires (e.g. labial arch , which holds the lip and its pressure off) or screws serve as active elements. Monoblocks, on the other hand, are deliberately not firmly anchored, but work through the function (mouth opening and closing). Even if these wire elements are partially prefabricated, it is up to the dental technician to adapt them exactly and to manufacture the plastic parts.
In orthodontic appliances, the implementation in plastic differs from that in prostheses:
In both procedures, the models are first thoroughly watered in order to prevent air bubbles from rising in the pressure pot during the subsequent polymerization . They are then isolated so that the plastic can be easily removed from the model after it has hardened.
- Scattering method: Without embedding the model, the powder (polymer) is scattered directly onto the model with slight pendulum movements and then wetted with liquid (monomer). It should be noted that only as much liquid is applied as can be absorbed by the powder, otherwise the material will flow.
- Modeling Technique: This technique is preferred when making bimaxillary devices. Here, 2.5 parts of powder are mixed with 1 part of liquid in a mixing vessel and after a soaking time of 4 to 7 minutes, the plastic can be applied directly to the isolated model. After approx. 10 minutes the polymerization starts.
In both processes, the final polymerization takes place at 2 to 3 bar in a pressure pot and a water temperature between 35 ° C and 45 ° C for 25 minutes.
Upper and lower jaw expansion plates
Other work areas
Occlusal splints
A bite splint (also Miniplast rail called) to produce, in a thermoforming unit mm an about 1 to 4 mm thick plastic film plasticized by heat (softens) and compressed air and evacuation pressed on the jaw model. Then the desired section can be milled out of the film and worked out. Splints produced in this way are used, among other things, to produce temporary bridges as a carrier film or to splint traumatically (accident-related) loosened teeth. They can also serve as a drug carrier for gels in the case of fluoridation of the teeth. To use them as a grinding splint , they can be customized by applying plastic that fixes the desired position of the opposing jaw.
Thermoforming device
Bite splint on the model
Occlusal splint
Mandibular protrusion splints
In patients with mild to moderate obstructive sleep apnea syndrome (OSAS) and upper airway resistance syndrome (UARS), two forms of sleep-related breathing disorders, mandibular protrusion splints are sometimes used as therapy . These adjustable splint systems, which are individually manufactured after taking an impression of the teeth, are positioned in the laboratory and the lower jaw, tongue and other structures are positioned forward and the bite is opened. This reduces the constriction of the pharynx, the airways are mechanically kept open during sleep and the airway resistance decreases.
Anti-snoring splints
Anti-snoring devices are absurdly often referred to as "snoring devices". In the narrower sense, they are anti-snoring splints. There have been and are a number of attempts to counteract snoring with the help of appliances attached to the teeth. There are currently around 70 different models reportedly. The dental technician is also responsible for making such devices after being commissioned by the dentist . Protrusion splint and oral atrial plate . An anti-snoring splint is not a statutory health insurance benefit . It is also not included in the service catalog of the fee schedule for dentists . It is calculated there as analog power . The dental technology costs are calculated according to the federal uniform designation list (BEB) for private services.
See also: snoring
Finishing and polishing
For all dental work it is necessary to carefully finish the work pieces and polish them to a high gloss . A high gloss polish is a surface refinement. Roughness peaks of the surface structure are plastically and partially plastically deformed and thus leveled (press polishing; Burnishing). On the other hand, depending on the type of polishing, a very small to small amount of material is removed (polishing). The smoothness of the workpiece reduces the adhesion of dental plaque
The lips and especially the tongue of the patient feel and feel every tiny unevenness or even sharp edge. The tongue perceives all irregularities many times greater.
The polishing is done from coarse to fine. The processed medium is getting finer and finer: depending on the material (e.g. milling machine, sandpaper of different grain sizes, pumice powder , goat hair brush and linen buff - the last two each with polishing pastes).
Prices
The prices for dental technology services, insofar as they are dental prostheses for patients with statutory insurance, are set out in a maximum price list ( Federal Uniform List of Services for Dental Technology Services (BEL)). In the case of private patients , prices can be calculated according to the principles of appropriateness and local custom. The uniform national designation list for dental technology services (BEB) is the basis for this.
The prices applicable to practice laboratories for patients with statutory insurance are reduced by 5% compared to the prices that commercial laboratories are allowed to charge. Quote: "The amounts according to sentence 6 are reduced by 5 percent for dental technology services that are provided by dentists." The background is that a commercial laboratory - in contrast to the practice's own laboratory - is subject to trade tax .
According to Section 12 (2) No. 6 UStG, dental work is subject to the reduced VAT rate of 7% (as of 2017).
The legislator wants to offer inexpensive dentures . That is why many statutory health insurance companies recommend their patients to find out about cheap dentures from abroad. Some health insurance companies also give their insured persons recommendation lists that contain German dental laboratories that produce dentures at comparatively low prices. However, this ignores the fact that the well-rehearsed cooperation between dentist and dental technician is decisive for the treatment result.
Tendencies
Future developments in dental technology will be directed towards particularly biocompatible materials, an improvement and simplification of the process technology and a further improvement in the individualization of dentures in order to avoid any impression of the "artificial". This requires optimal cooperation between patient, dentist, practice staff and dental technicians. Because more and more patients value not only natural-looking dentures, but also their firm hold and high functionality, the proportion of dentures attached to implants has been increasing for years. This tendency will continue.
Dental technology will also change in the next few years in such a way that increasingly highly specialized automation will find its way into the highly technical, but still manual craft . Various CAD / CAM systems are available that record the jaw situation through mechanical scanning, laser or optical scans in order to design the dentures on the screen. These data are transferred to a production machine that mills or sintered the dentures from a wide variety of materials . Framework materials such as zirconium , zirconium oxide , aluminum oxide , titanium , etc., which are characterized by their particular strength, are increasingly being used.
Individual evidence
- ↑ Notes on the master's examination regulations for dental technicians
- ↑ Berliner Zeitung of January 10, 2004
- ↑ Bavarian TV, Health program from November 4, 2008 ( Memento from March 22, 2009 in the Internet Archive )
- ↑ BZÄK / KZBV (July 2015): Dentistry and Zahntechnik - Legal bases and information for the dental practice. P. 4
- ↑ Merger of dental laboratories
- ↑ a b Terminology and nomenclature of the German Society for Functional Diagnostics and Therapy (DGFTD) and the German Society for Dental Prosthetics and Materials (DGzPW), V 2.0 of September 1, 2005, accessed on April 14, 2013.
- ↑ Fee schedule for dentists (GOZ 2012) Functional analytical and functional therapeutic services, Section J (PDF file; 2.85 MB)
- ↑ a b c d e Klaus de Cassan: Dental Knowledge Lexicon.
- ↑ Active Plate - Loose Braces for Children - Orthodontics. In: 360gradzahnspange.de. April 16, 2019, accessed April 16, 2019 .
- ↑ Functional orthodontic devices
- ^ R. Janda, K. Greiner: about: Plastics for removable orthodontic appliances. ( Memento of December 22, 2010 in the Internet Archive ) (PDF file; 111 kB)
- ↑ S3 guideline for non-restful sleep / sleep disorders of the German Society for Sleep Research and Sleep Medicine (DGSM). In: AWMF online (as of 2009)
- ↑ Susanne Schwarting, Ulrich Huebers, Markus Heise, Joerg Schlieper, Andreas Hauschild: Position paper on the use of mandibular advancement devices in adults with sleep-related breathing disorders . In: Sleep and Breathing . Vol. 11, No. 2 , 2007, p. 125–126 , doi : 10.1007 / s11325-007-0116-z , PMID 17464519 , PMC 2211364 (free full text) - (English).
- ↑ Social Security Code, Book Five, Statutory Health Insurance, Section 57, Paragraph 2
- ↑ Tax rate / 7 Dental technology services - § 12 Paragraph 2 No. 6 UStG , haufe.de
- ↑ Aerzteblatt.de (February 25, 2009)
Sources / literature
- Arnold Hohmann, Werner Hielscher: Lexicon of dental technology. Verlag Neuer Merkur, 1998, ISBN 3-929360-28-4 .
- Horst Gründler, German Bär: Masters can do for dental technicians. 3. Edition. Verlag Neuer Merkur, 2005, ISBN 3-929360-64-0 .
- Walter Hoffmann-Axthelm : Lexicon of dentistry. Quintessenz-Verlag, Berlin.
- D. Haunfelder, L. Hupfauf, W. Ketterl, G. Schmuth and others: Praxis der Zahnheilkunde. Chapter C1. Urban and Schwarzenberg publishing house, Munich / Vienna / Baltimore.
- Paul Weikart: Materials science for dentists. 4th edition. Carl Hanser Verlag, Munich.
- Dominik Groß: Dictionary of Dentistry and Dental Technology - Dictionary of Dentistry and Dental Technology. Volume 1, Neuer Merkur publishing house, Munich 2002.
