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What is the first stage of fabrication of metal-ceramic restorations?
What is the purpose of the die spacer in the fabrication process?
What material is used to eliminate the die spacer application stage and wax modeling stage in contemporary dentistry?
What technique is used to mill the infrastructure designed in the computer-aided design (CAD) unit?
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In which stage does the process of lost-wax and casting technique occur?
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How are wax infrastructures produced, apart from the subtractive technique mentioned in the text?
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What is the most popular method for melting metal alloy in today's system?
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How is the molten metal alloy sent into the casting cavity in the third component?
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What is the biggest disadvantage of both hard and soft processing methods in milling technique?
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What does the shrinkage during sintering result in?
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What is another term used to refer to additive manufacturing systems in dentistry?
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What is the basic principle of obtaining restoration in the subtractive method?
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Which technique involves creating a mass with the help of a laser and uses commercially available powder materials?
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What is the first step in the common stages of additive systems as mentioned in the text?
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Which technique allows the fusion of powdered particles with the help of a carbon dioxide laser?
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Which technique involves melting the powdered material completely instead of sintering?
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Which technique does not need a support unit during production and has a wide range of materials?
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Which technique can use thermoplastic materials, ceramics, metals, and composites, and allows material recycling and reuse?
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In stereo lithography apparatus (SLA) technique, how is the three-dimensional solid material constructed?
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What is the main purpose of the sprues in the traditional casting consolidated with lost-wax technique?
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What is a disadvantage of fused deposition modeling (FDM) technique?
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What are the basic components of stereo lithography apparatus (SLA) technique?
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What is the purpose of the investment material in traditional casting method consolidated with lost-wax technique?
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What is a characteristic feature of fused deposition modeling (FDM) equipment?
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What is the key factor for the long-term success of metal-ceramic restorations?
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What is the purpose of the key-lock mechanism (micromechanical interlocking) formed between the alloy and the porcelain?
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Why is it important to thin the thick oxide layer before veneer porcelain application?
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What is added as trace elements to some noble alloys to create an adequate oxide layer for metal-porcelain connection?
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How does the thermal expansion of the metal compare to that of porcelain?
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What is the purpose of adding high melting point elements like platinum and palladium to the alloy structure?
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What is the purpose of the heat treatment that the metal infrastructure undergoes before porcelain veneering?
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Why is it important for the porcelain material to have an appropriate thermal expansion coefficient according to the selected dental alloy?
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What is the purpose of applying opaque powder to the metal surface before porcelain application?
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What is the purpose of using a desiccant paper in the porcelain application process?
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What happens during the degasing process in the heat treatment of the metal infrastructure?
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What is the recommended consistency for the opaque mixture applied to the metal surface?
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What should be done after applying opaque mixture to the metal surface before firing?
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Why is it necessary to keep porcelain moist during application?
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What does the firing shrinkage compensation entail in the porcelain application process?
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What is used to moisten the opaque surface before applying cervical porcelain?
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What is the purpose of the die spacer in the fabrication process?
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How are wax infrastructures produced, apart from the subtractive technique mentioned in the text?
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What is added as trace elements to some noble alloys to create an adequate oxide layer for metal-porcelain connection?
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What is the purpose of the heat treatment that the metal infrastructure undergoes before porcelain veneering?
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What is the purpose of the investment material in traditional casting method consolidated with lost-wax technique?
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What is the key factor for the long-term success of metal-ceramic restorations?
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What are the basic categories into which milling systems are divided?
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What is the biggest indication that the additive method will soon replace milling techniques?
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What are the different names used to refer to additive manufacturing systems in dentistry?
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What are the two types of metal blocks used in the hard machining method?
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What is the main disadvantage of the hard processing method in milling technique?
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What is the ASTM definition of additive manufacturing?
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What is the selective laser sintering technique and how does it differ from selective laser melting?
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What are the precautions taken to minimize complications in the selective laser sintering technique?
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How does the selective laser melting technique overcome problems such as shrinkage, fracture, distortion, and surface hardening?
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What materials can be used in selective laser sintering, and what is one of its significant features?
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What are the reported advantages of restorations produced with the selective laser melting technique compared to conventional casting techniques?
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What are the benefits of using the selective laser sintering and selective laser melting techniques in terms of reducing technical complications in dental laboratory steps?
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What are the four components of the metal-porcelain connection in metal-ceramic restorations?
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What is the key factor for the long-term success of metal-ceramic restorations?
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What is the purpose of adding trace elements such as iron, gallium, indium, and tin to some noble alloys?
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Why is it important to thin the thick oxide layer before veneer porcelain application?
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What is the purpose of applying opaque porcelain to alloys with a relatively light oxide layer?
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What role do metal elements with high melting degrees play in the metal-ceramic connection?
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Explain the process of manufacturing a 3-dimensional model using the stereo lithography apparatus (SLA) technique.
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Describe the process of layer by layer extrusion in fused deposition modeling (FDM) technique.
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What are the primary purposes of the wax sprues in the traditional casting consolidated with lost-wax technique?
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Explain the significance of the investment material in the traditional casting method consolidated with lost-wax technique.
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What are the disadvantages of fused deposition modeling (FDM) technique?
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What is the basic principle of obtaining restoration in the subtractive method?
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What is the role of the degasing process in the heat treatment of the metal infrastructure before porcelain veneering?
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How does the recommended opaque firing temperature compare to the temperature for cervical porcelain firing?
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What is the critical role of the porcelain material with the appropriate thermal expansion coefficient in relation to the selected dental alloy?
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Why is it important to keep the porcelain moist during application?
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What is the significance of the fusion of powdered particles with the help of a carbon dioxide laser?
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Why is it necessary to remove excess moisture with a desiccant paper in the porcelain application process?
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What is the purpose of the key-lock mechanism (micromechanical interlocking) formed between the alloy and the porcelain?
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What does the shrinkage compensation entail in the porcelain application process?
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What is the characteristic feature of fused deposition modeling (FDM) equipment in the context of dental applications?
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What is the purpose of thinning the thick oxide layer before veneer porcelain application?
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The first stage of fabrication of metal-ceramic restorations is the wax modeling of the ______ (coping, framework) to be produced.
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The infrastructure designed in the computeraided design (CAD) unit is milled (subtractive technique) in the CAM unit using either wax or PMMA ______.
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After the wax replica (model) is obtained from the CAM unit, the process continues with conventional lost-wax and casting ______.
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Wax infrastructures are not only produced by the subtractive ______ as above.
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In contemporary dentistry, wax blocks or PMMA resin blocks from various companies are used in order to standardize fabrication, eliminate die spacer application stage, wax modeling stage and thus possible errors that may occur during these ______.
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The dental technician performs the wax-modeling of the ______ on the patient's cast model.
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SLA technique in which 3 dimensional models are manufactured by photosensitive polymer is the most widely used among the additive techniques. The technique defined by Hull in 1984, systematically consists of 3 basic components: (i) pool with a photosensitive liquid, (ii) platform where the model is manufactured, (iii) ultraviolet (UV) ______.
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When photopolymer resin is exposed to UV light, the first layer at a certain thickness hardens. Following the hardening of the first layer, the platform where the model is produced is lowered at a certain distance in the pool and a new layer of photopolymer resin is applied on the previous ______.
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Fused deposition modeling is the second widely used fast prototyping technique after stereo lithography enabling the layer by layer extrusion of the thermoplastic material with the help of a nozzle controlled by ______.
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In this technique, the filament of the thermoplastic polymer material feeds the extrusion nozzle controlled by ______.
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The wire-like plastic material in strips leads to extrusion nozzle and here the material is melted by ______.
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The extrusion nozzle forms the first layer of the product by spraying the distilled molten material on the platform. At this stage, the heat of the platform is kept at lower degrees and thus, the sprayed thermoplastic material is immediately (in 0.1 second) ______.
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The selective laser sintering technique allows the fusion of powdered particles with the help of a ______ laser.
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The selective laser melting technique completely melts the powder material, creating a ______ pool.
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The SLM technique produces a mass with the help of a ______ and uses commercially available powder materials.
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In selective laser melting, problems such as shrinkage, fracture, distortion, and surface hardening are expected, which can be minimized by using fine-grained powder materials and the process taking place in ______ gas.
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Selective laser sintering technique allows the use of thermoplastic materials, ceramics, metals, and composites, and also allows material recycling and ______.
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In the selective laser sintering technique, the temperature applied by the laser should be kept below the melting range of the material and the heat should be enough to allow the particles in the material to be ______.
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The difference between the thermal expansion coefficients of metal and porcelain should be approximately ______ degrees
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The mixture should have a brush-like consistency and not too ______
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The fully processed crown or bridge needs to be processed approximately ______% larger than the normal form
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Enamel porcelain can be applied by spatula removing the required parts after the original form has been formed by stacking enamel porcelain to all layers, or enamel porcelain can be stacked towards the ______ edge
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Porcelain is never left completely ______
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After the second opaque firing, the metal should never be seen under the opaque. Also, the baked opaque surface should not have a rough ______ appearance
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The metal infrastructure is subjected to a heat treatment before porcelain veneering. This application is generally done in vacuum at about 1000 degrees for 8-10 minutes. This is called ______, by which all gases and contaminants come to the surface under heat and move away from metal
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The space available for porcelain in a metal-porcelain crown is often limited. For this reason, the opaque powder to be applied must have superior ______ properties
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The metal-porcelain connection has four components: van der Waals forces, mechanical retention, chemical connection, and ______ connection.
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Secondary forces (van der Waals forces) formed between charged atoms are important in metal-porcelain connection of metal-ceramic restorations. It can also be expressed as the minimal attraction force formed between the electrons and nuclei of atoms in a molecule and the nuclei and electrons of the atoms of neighboring molecules. Increased wettability of the metal surface also increases the effectiveness of van der Waals forces. The key-lock mechanism (micromechanical interlocking) is formed between the alloy and the porcelain in the mechanical connection. Ceramic is infiltrated on the metal surface, which is microscopically roughened with aluminum oxide particles (air-borne particle abrasion), during porcelain firing. Mechanical connection is important in terms of increasing the wettability of the metal by porcelain and helping chemical connection by increasing the surface area. However, in cases where excessive roughening is performed, stress accumulation occurs on the interface and sharp edges and corners caused by incorrect blasting reduce the wettability and cause gaps in the interface. The chemical connection between metal and porcelain is established through oxides on the metal surface. The thickness and composition of the metal oxide layer is very important in the long-term success of the connection. Metal oxide formation takes place spontaneously in many base metal alloys; sometimes the oxide layer formed can be very thick. In these cases, the thick oxide layer should be thinned before veneer porcelain application and the layer thickness should be kept at optimum values. However, due to the low reactivity of gold, not enough oxide layers can be formed in high noble and some noble alloys to establish metal-porcelain connection. Metals such as iron, gallium, indium, and tin are added as trace elements to create an adequate oxide layer for these alloys. Since these elements burn easily during casting; these alloys do not overheat. While the thickness and composition of the metal oxide layer is important for the metal-porcelain connection, the color of the layer is also very important in terms of aesthetics. High gold alloys have a relatively light oxide layer. In this case, the layer can be easily masked with opaque porcelain. However, since many alloys based on silver, nickel, and cobalt form a darker, grayish oxide layer; thicker layer opaque porcelain application is required to mask the layer in these alloys. The thin or thick oxide layer increases the risk of failure in the metal-ceramic connection because occlusal stresses are concentrated in the Near East University, Faculty of Dentistry 12 Assoc. Prof. Dr. Özay ÖNÖRAL oxide layer. The thickest oxide layer formation occurs in nickel and cobalt based alloys because these alloys contain elements that can easily form oxides at the initial oxidation stage. As a result, sufficient oxide formation that does not endanger the expansion, durability, color, and opacity properties of porcelain is a desired feature. The last component that plays an active role in metal-porcelain connection is ______.
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Connection in the ______ style is provided depending on the thermal expansion of the materials. Alloys and ceramics expand when heated; they shrink when cooled. The dimensional increase (amount of expansion) of the material per unit of heat is expressed as the coefficient of thermal expansion and its unit is (ºC) -1. It should be remembered that shrinkage will increase as the thermal expansion coefficient increases. The thermal expansion of the metal is greater than porcelain. After the porcelain is baked with metal, both begin to shrink during cooling. Metal shrinks faster than porcelain. A tension occurs in metal that shrinks faster than porcelain, and a compression occurs in porcelain. When metal and porcelain are connected, three possible relationships can occur in thermal expansions. These are; (1) the thermal expansion of the porcelain is greater than that of the metal, (2) the thermal expansion of the porcelain is equal to that of the metal, or (3) the thermal expansion of the metal is greater than that of the porcelain. The porcelain is quite resistant to stresses in the style of tension. In the first relationship, since such stresses will occur, porcelain deformed with the formation of fast cracks and crack propagation. In the second relationship, no stress occurs in porcelain. However, it is impossible to achieve such a relationship practically. In the third relationship, since the metal will shrink more than porcelain; compression stresses occur in porcelain.
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Metal elements (platinum, palladium) with high melting degrees are added to the structure in order to increase the melting degree of the alloys. Not all ceramics are compatible with alloys. Therefore, manufacturers indicate which ceramic can be used with which alloy. Connection in the ______ style is provided depending on the thermal expansion of the materials.
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The last component that plays an active role in metal-porcelain connection is ______.
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Connection in the ______ style is provided depending on the thermal expansion of the materials. Alloys and ceramics expand when heated; they shrink when cooled.
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In the first component, the metal alloy rod is melted at the point where it opens out or in a separate crucible located in the casting device. In the second component, the metal alloy is melted using gas-air torch, oxyacetylene torch, electric induction heating or one of the electric resistance melting methods. In the third component, the molten metal alloy is sent into the casting cavity with the help of gravity, air pressure, steam pressure or centrifugal / centrifugal force. In today's most popular system, metal alloy is melted in a separate crucible with electric induction heating and the molten metal is sent to the casting cavity with ______ force (Ulusoy & Aydın, 2010, p. 571-574).
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More than 20 milling systems have been developed from past to present and these systems are basically divided into 2 categories as hard machining and soft machining. Near East University, Faculty of Dentistry 6 Assoc. Prof. Dr. Özay ÖNÖRAL Fully sintered nonporous ingots are used in the hard machining method, which is defined as obtaining the restoration by milling from the sintered mono-block. In this method, milling is done quite hard. However, they do not need to be subjected to sintering again. Soft processing, on the other hand, finds expression as the process of obtaining restoration by milling from the block that will later be sintered. Pre-sinterized ingots are porous and allow a rapid milling process. In order for the porous structure to be eliminated, they must be subjected to a sintering process (Ebert et al. 2009; Griggs, 2007). The processing steps of soft metal blocks developed in recent years are almost similar to the processing steps of zirconia in pre-sinterized form (Kim et al., 2016). Since both systems are subtractive methods, the biggest disadvantage of both systems is significant ______ expenditure because the parts are no longer usable after milling, and it is not possible to recycle the ______. While the restorations produced with the hard processing method offer advantages such as obtaining the correct shape and full size. One of the most important disadvantages of the method is that the processing of sintered blocks is an expensive and time-consuming process. Also in this method, the tools are exposed to severe abrasion (Kim et al., 2016; Kocaagaoglu et al., 2016). In addition, there is a risk of microscopic cracks forming on the metal surface during the processing of the ______. This does not occur during soft machining because milling is done before sintering process. In addition, milling of pre-sintered mono-blocks ensures both shorter machining times and longer tooling cycles (Kim et al., 2016; Kocaagoglu et al., 2016). However, the accuracy and shape of the restorations produced by the soft processing method is a bit more troubled than the hard processing. The reason for this is the shrinkage that will occur during the sintering that will be done later (Bindl & Mörmann, 2007; Ebert et al., 2009; Wong & Hernandez, 2012). For example, after soft metal milling, metal infrastructures are subjected to high sintering in argon gas environment. This application results in 11% shrinkage (Kim et al., 2016; Kocaağaoğlu et al., 2016). With these techniques, many laboratory steps such as wax modeling (waxing), spruing, investing, wax elimination, and casting are eliminated (Lapcevic et al., 2016). Thus, technical complications that may occur at these stages are also eliminated. Although subtractive methods still have widespread use in the clinic; additive manufacturing techniques, which have important Near East University, Faculty of Dentistry 7 Assoc. Prof. Dr. Özay ÖNÖRAL advantages and superior features, continue to develop rapidly. This is the biggest indication that the additive method will soon replace milling techniques. 3. Layering (Additive Manner) Additive manufacturing systems are defined as systems that enable the production of an object with three dimensional designs (CAD) with computer support by adding a layer on the layer (Azari and Nikzad, 2009; Madhav and Daule, 2013; Ruiz et al., 2015; Torabi et al., 2015; Van Near East University, Faculty of Dentistry 8 Assoc. Prof. Dr. Özay ÖNÖRAL Noort, 2012). Additive manufacturing is expressed by the American Society for Testing and Materials (ASTM) as follows: “Contrary to subtractive production methods, it is the process of layering the ______s (adding layers on the layer) in order to produce objects from the computer data of the three-dimensional model” Additive manufacturing system, which is widely used in dentistry today, can be referred as 3D printing, additive fabrication, rapid prototyping, layered manufacturing or solid freeform fabrication (Azari and Nikzad, 2009; Madhav & Daule, 2013; Sun & Zhang, 2012; Torabi et al., 2015; Van Noort, 2012).
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