10.0 Communicating with the Dental Laboratory, Working Casts and Dies, Wax Patterns, Framework Design and Metal Selection for Metal-Ceramic Restorations

Question 1

1. the key to the technical success of the dental team
2. • The dentist should provide ______________ to the laboratory or dental technician. The dentist should provide the laboratory technician with accurate________________________________________. Also, they should provide ______________________ to proceed with a laboratory procedures or make any appropriate changes.
3. REQUIREMENTS FORGOOD CASTSWHEN MAKING WAX PATTERNS
   A. They must be _____________, especially along the finish lines of the prepared teeth.
   B. All portions of the cast must be ____________
   C. The cast must be _______ to ensure access for carving wax pattern margins.
4. committed to upholding and advancing the commercial dental laboratory activity.
5. an independent board established by the NADL, offers voluntary certification in dental laboratory technology. Certification can be obtained in six specialty areas: crowns and bridges, ceramics, partial dentures, complete dentures, implants, and orthodontic appliances.
6. basic working cast and die systems used in the dental laboratory (2)

Answer 1

1. • Good communication
2. written instructions; impressions, casts, occlusal registrations and/or mounted casts; verbal or written approval
3. free of bubbles; free of distortion; trimmed
4. NATIONAL ASSOCIATION OF DENTAL LABORATORIES
5. National Board for Certification in Dental Laboratory Technology
6. working cast with a separate die; B. Working Cast with a Removable Die

Question 2

1. the simplest means of fabricating a working cast and die because no procedures are required to create a die other than making a sectional cast and a full-arch cast.
2. Dies that can be removed from the working cast have become very popular. They are convenient to use because wax patterns or copings need not be removed from their respective dies transferred to the working cast.
3. If a removable die system is used, it should satisfy these three requirements:
   1). The dies must return to their ________________________.
   2.) The dies must remain _____, even when inverted.
   3.) The cast containing the dies must be ____________ on an articulator.
4. Single dowels are simple to use, but they do not provide as much ________________ as double dowels
5. Types of antirotational devices used for removable dies: (3)
6. The _______________ as a means of orienting dies has been in use for a number of years, and most of the dowel systems are modifications of it. The _______________ is one of the most accurate dowel types in terms of resisting horizontal displacement and the second lowest in vertical deviation of four types of removable dies.
7. a reverse drill press is used to create a master cast with dies that can be removed and replaced repeatedly with great precision (Fig 18-28). The impression is poured without positioning and attaching dowel pins beforehand. The machine accurately drills parallel holes from the underside of a trimmed cast.

Answer 2

1. working cast with a separate die
2. Working Cast with a Removable Die
3. exact original positions; stable; easy to mount
4. antirotational resistance
5. (a) flat-sided single dowel; (b)
   double straight dowels with a common head; (c) two separate parallel dowels
6. straight dowel pin; brass dowel pin
7. Pindex system

Question 3

● The written instructions are referred to as a _____________(1); elsewhere, it may be referred to as a laboratory work order or prescription. In addition to certain general information that is required by law, a work authorization form should include the following:
○ __________ description of the restoration to be made
○ _______ specification (e.g., anatomic contour zirconia)
○ Desired __________ scheme
* _________ design for fixed dental prostheses
○ _____ design, including the material specification for tissue contact
○ _________ design for metal-ceramic restorations
○ Information regarding the _____________ for esthetic restorations
○ Proposed partial __________________ design (if applicable)
○ ______ of the patient’s next scheduled appointment and the stage of completion required by then
2. - ____________ comprise a group of synthetic polymer-based impression materials that are chemically cross-linked when set and that can be stretched and yet rapidly recover to their original dimensions, like vulcanized natural rubber when the applied stress is released. Chemically, there are three elastomers based on the backbone of polymer chains: _________, ___________ (condensation and addition), and ______.

Answer 3

1. work authorization
   - General
   - Material
   - occlusal
   - Connector
   - Pontic
   - Substructure
   - shade selection
   - removable dental prosthesis
   - Date
2. Elastomers
   - polysulfide
   - silicone
   - polyether

Question 4

Explain how dies are prepared?
1. The die is first _______ on a cast trimmer.
2. A properly trimmed die handle is slightly _____ in diameter than the preparation.
3. Improperly trimmed die with a handle that meets the preparation at an ______
4. The handle should be ______ long
5. The die is trimmed with an ___________.
6. Shaping of the die handle near the ____________ is completed with a scalpel.
7. The die is smoothed below the finish line with the ____________ of a Tanner carver.
8. This die is ___________, and it does not allow adequate access for margin finishing.
9. ___________ should be similar to those of a natural tooth.
10. ________ of the wax pattern are influenced by die trimming
11. The preparation finish line on the die should be outlined with a ________.
12. _____________ is painted on the preparation portion of the die

Answer 4

1. trimmed
2. larger
3. angle
4. 1 inch
5. acrylic bur
6. finish line
   7/ discoid end
7. too short
8. Die contours
9. Axial contours
10. red pencil
11. Die relief agent

Question 5

• The die and cast should have a hard enough surface to prevent surface abrasion when the wax pattern is fabricated. Therefore, one of the _______________(class II, Densite) or high-strength, high-expansion type V stones should be used for fabricating the die. An impression should be washed under cold running tap water to remove mucus and saliva that may cover it before disinfecting it in an appropriate solution.
• A measured amount of water is placed in a plastic mixing bowl (Vac-U-Mixer), and a measured amount of die stone is added to the water.
• Water and stone are mixed by hand with the spatula until the powder is completely wet.
• A small instrument is used to carry stone to the impression of the prepared tooth. A small amount of stone is placed on the side of the impression above the preparation, and the impression is vibrated until stone reaches the “bottom” (ie, incisal or occlusal surface) of the preparation.
• To pour a full-arch impression, the tray is placed on the vibrator. It should not be rested on the impression material. Small increments of stone are added to the distalmost area of one side of the impression

Answer 5

high-strength type IV ; high-strength, high-expansion type V

Question 6

1. What are the type of acrylic bur used to trim the diet of the prepared abutment?
2. ● _________________________________________ below the finish line is not advised because the instrument used for finishing the margins of the wax pattern will rest against this portion of the die, its angulation can be exaggerated by the undercut. This will result in a ____________ on the restoration and an axial contour that is not conducive to good gingival health.
3. What are type of waxes used in the fabrication of wax patterns extraorally?
4. The ____________ is the precursor of the finished cast restoration that will be placed on the prepared tooth. Inasmuch as the wax pattern will be duplicated exactly through the investing and casting technique, the definitive restoration can be no better than its wax pattern (ie, errors and oversights in the wax pattern will be perpetuated in the casting).
   There are two accepted ways of fabricating a wax pattern:
5. The ________________, in which the pattern is waxed on the prepared tooth in the mouth
6. The _______________, in which the pattern is waxed on a stone cast made from an accurate impression of the prepared tooth

Answer 6

1. ● A pear-shaped acrylic bur
2. Sharply undercutting or “ditching” the die; thick gingival area;
3. ● Type 2 waxes are used for the fabrication of wax pattern extraorally which have a slightly lower melting point
4. wax pattern; direct technique; indirect technique

Question 7

● Conventional facial margin for a metal ceramic crown has a narrow metal collar. To avoid___________ on highly visible teeth, the facial finish line was often placed subgingivally, which contributed to ___________________ or more serious periodontal problems. Gingival recession may occur from the ___________________, ________________, or an ______________________________. Following cementation, 60% of subgingival margins become visible within a 2-year period.

Answer 7

metal display; chronic gingival inflammation
trauma of tooth preparation; impression taking; improperly contoured provisional restoration

Question 8

1. The metal coping in an MCR is covered with three layers of porcelain (3)
2. ● Metal ceramic restorations are combined with cast metal ___________________ with the esthetics of porcelain
   ● the MCR remains the “_______________” of predictability with indirect tooth-colored systems. It is generally accepted that, in spite of development of high- strength ceramic materials
   ● MCRs are more resistant to _____________
3. What type of waxes are formulated for making intraoral wax patterns?

Answer 8

1. 1). Opaque porcelain conceals the metal underneath, initiates the development of the shade, and plays an important role in the development of the bond between the ceramic and the metal.
   2.) Dentin, or body, porcelain makes up the bulk of the restoration, providing most of the color, or shade.
   3.) Enamel, or incisal, porcelain imparts translucency to the restoration.
2. strength and accuracy; gold standard; fracture
3. Type I WAXES(19#335)

Question 9

1. Four mechanisms have been described to explain the bond between the ceramic veneer and the metal substructure:
2. creates attachment by interlocking the ceramic with microabrasions in the surface of the metal coping, which are produced by finishing the metal with noncontaminating stones or disks and air abrasion. When compared with unprepared metal, surface finishing enhances the metal-ceramic bond. 7 Air abrasion appears to enhance wettability, provide mechanical interlocking, and increase the surface area for chemical bonding. 8 The use of a bonding agent, such as platinum spheres, 3 to 6 μm in diameter, also can increase bond strength significantly
3. The slight difference in coefficients of thermal expansion, or thermal contraction as is the case during cooling, will cause the porcelain to draw toward the metal coping when the restoration cools after firing.
4. comprise an affinity based on a mutual attraction of charged molecules. They contribute to bonding, but they are a minor force that is not as significant as was once thought. 10 Although the molecular attraction makes only a minor contribution to overall bond strength, it is significant in the initiation of the most important mechanism, the chemical bond
5. indicated by the formation of an oxide layer on the metal 11,12 and by bond strength that is increased by firing in an oxidizing atmosphere. 13,14 When fired in air, trace elements in the gold alloy, such as tin, indium, gallium, or iron, migrate to the surface, form oxides, and subsequently bond to similar oxides in the opaque layer of the porcelain. A gold alloy containing minute amounts of tin and iron creates a significantly stronger bond with porcelain than a pure gold alloy does.

Answer 9

1. Mechanical entrapment ; Compressive forces ; Van der Waals forces ; Chemical bonding
2. Mechanical entrapment
3. Compressive forces
4. Van der Waals forces
5. Chemical bonding

Question 10

● Melting range of the alloy used in coping must be ___________________than the fusing temperature of the porcelain applied to it.
● Similar melting range of the 2 materials would result in the distortion or melting of the coping during firing and glazing of the porcelain.
● Noble Metal coping is subject to flow or creep when it is heated to _________
● Porcelain used must not require that the metal be heated much beyond this point. Porcelains most commonly used for this purpose have a fusing temperature at 870 C to 930 C and noble alloys melt at near 1,260 C

High Noble: (3)
Noble: (2)
Predominantly Base: (3)

A _______________ refers to restorations that can be fabricated inside the mouth. These restorations can be completed during a single dental appointment because they do not require the use of a dental lab for fabrication. The most common direct restoration used by cosmetic dentists are _______________.

_________________ it refers to permanent or semi-permanent fixed restorations that must be fabricated outside of the mouth. These types of restorations generally need to be fabricated by a dental laboratory, however they can also be fabricated using an in-office milling machine. An example of indirect restoration includes: crowns and bridges, dental implants, inlays & onlays, and porcelain veneers.

Answer 10

170 C to 280 C higher .
980 C
Gold-Platinum-Palldium, Gold-palladium-silver, Gold-palladium
Palladium-silver, High palladium
Nickel-chromium, Nickel-chromium-beryllium, Cobalt-chromium
direct restoration
composite fillings
indirect restoration