Metal ceramics /certified fixed orthodontic courses by Indian dental academy

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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
0091-9248678078

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  • Metal ceramics /certified fixed orthodontic courses by Indian dental academy

    1. 1. METAL CERAMICS INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
    2. 2. 1.HISTORY. 2. TERMINOLOGY. 3. CHEMISTRY & COMPOSITION. 4. ALLOYS FOR THE METAL CERAMICS. 5.TOOTH PREPARATION FOR THE METAL CERAMIC RESTORATION. 6. METAL CERAMIC SUB STRUCTURE DESIGN. www.indiandentalacademy.com
    3. 3. 7. FUNDAMENTALS OF THE SPRUING, INVESTING&CASTING. 8. BONDING BETWEEN THE METAL &POCELAIN. 9. SOLDERING &FINISHING OF THE METAL SUB STRUCTURE 10. PORCELAIN APPLICATION METHODS www.indiandentalacademy.com
    4. 4. 11.FURNACE 12. FIRING PROCEDURES. 13. FINISHING &ADJUSTMENTS www.indiandentalacademy.com
    5. 5. Chinese were the first to introduce porcelain in 1000A.D. D’Entrecolles is first person to use porcelains in the dentistry. Dental porcelains were used first to fabricate the complete dentures. The technology for the metal ceramics introduced in 1950’s Dechaeteau 1985 was the first person to make a pair of complete dentures for himself. www.indiandentalacademy.com
    6. 6. Italians in 1808 made porcelain teeth. Claudius Ash 1985 created an artificial tooth that could be placed over the complete dentures & fixed partial dentures. Land Went 1985 developed low fusing porcelains & porcelain jacket crown www.indiandentalacademy.com
    7. 7. TERMINOLOGY:METAL CERAMIC RESTORATION:-A fixed restoration that employs a metal substructure on which a ceramic veneer is fused. ALLOY:-A mixture of two or more metals that are mutually soluble in the molten state, distinguished as binary,tertnary,quaternary. NOBLE METAL:-A term applied to metal that are corrosion and oxidation resistant because of inherent chemical inertness. (Craig 1989) www.indiandentalacademy.com
    8. 8. There are at least seven noble metals used in dentistry.Gold,Platinum,Palladium,Iridium,Osmium, Rhodium,Ruthenium & Silver. NON NOBLE:-Alloys that composed of metal that are not noble. E.g.:-nickel,chromium,cobalt & aluminum. COPING:-A term used to describe the metal sub structure. DEGASSING:-A term used to describe the process of heating a metal structure believed to release entrapped gases and burn off organic surface impurities. www.indiandentalacademy.com
    9. 9.  OXIDATION:-The process of heat treating a metal ceramic alloy to produce an oxide layer for porcelain bonding.  OXIDE LAYER:-The colored film that forms on a metal ceramic alloy after the metal has been heated .  VACCUM FIRING:-The firing of dental porcelain in a furnace in which the air or atmosphere in order to create denser porcelain restoration. www.indiandentalacademy.com
    10. 10. COMPONENTS OF METAL CERAMIC RESTORATION 1.METAL SUB STRUCTURE . 2.THE OXIDE LAYER. 3.THE OPAQUE PORCELAIN LAYER. 4.THE DENTIN PORCELAIN. 5.THE ENAMEL PORCELAIN. www.indiandentalacademy.com 6.THE EXTERNAL GLAZE.
    11. 11. CHEMISTRY OF THE DENTAL PORCELAIN  The chemical components of the porcelain: 1.Feldspar:-feldspar is the primarily responsible to the glass matrix.  It occurs in a pure form but is a mix of two substances.  Potassium aluminum silicate & sodium aluminum silicate.  This is also called as albite. www.indiandentalacademy.com
    12. 12.  Potassium feldspar:-it adds translucent qualities to fired restorations.  When melted between 2280°c to 2730°c potash fuses with the kaolin & quartz to become glass  The potash form of feldspar increases the viscosity & controls the pyroplastic flow of the porcelain.  Sodium feldspar:-lowers the fusion temperature of the porcelain. www.indiandentalacademy.com
    13. 13. QUARTZ:  This has high fusion temperature and serves as a frame work around the other ingredients can flow.  It helps to prevent the porcelain build up from slumping on the metal substructure by stabilizing the mass at high temperature  Quartz also strengthen the porcelains. www.indiandentalacademy.com
    14. 14. ALUMINA It is considered as hardest & strongest oxide. Its CTE is similar to the low fusing porcelains. It also strengthens the porcelain. www.indiandentalacademy.com
    15. 15. KAOLIN: This particular ingredient of the porcelain is clay.  This is formed from the igneous rock containing alumina.  It is not include in the enamel porcelains because of the opaque character of the kaolin. www.indiandentalacademy.com
    16. 16. BASIC COMPONENTS The basic components of a traditional porcelain kit include 1.opaque porcelain. 2.dentin porcelains 3.enamel porcelains Modifiers,stains &glazes. Newest products has high fusing shoulder porcelains. www.indiandentalacademy.com
    17. 17. www.indiandentalacademy.com
    18. 18. OPAQUE PORCELAINS:These porcelains made opaque by the addition of the insoluble oxides like, Tin. Titanium. Zirconium. Cerium oxides. Such oxides have high refractive,so they scatter light. www.indiandentalacademy.com
    19. 19. The opaque layer serves three primary functions:1.It masks the color of the metal substructure. 2.It wets the metal surface &establishes the metal porcelain bonding. 3.It initiates the development of the selected shade. www.indiandentalacademy.com
    20. 20. DENTIN PORCELAINS The dentin porcelains correspond to the dentin of the natural teeth. The dentin porcelain is the major component of the porcelain restoration. www.indiandentalacademy.com
    21. 21. ENAMEL PORCELAIN Enamel porcelains are more translucent than dentin porcelains. The enamel porcelains are usually in the violet to grayish range &impart a combination of true translucency & the illusion of the translucency by virtue of their grayish or some times bluish appearance. www.indiandentalacademy.com
    22. 22. TRANSLUCENT PORCELAIN Translucent porcelains are not transparent.they do not allow the transmission of all lights. They are applied as a veneer over nearly the entire surface of the typical porcelain build up. The translucent enamel imparts the depth & enamel like translucency without substantially altering the body shade that is being overlaid www.indiandentalacademy.com
    23. 23. BODY MODIFIERS These porcelains are more color concentrated & were designed to aid in the achieving internal color modifications. They are used to distinguish the dentin,enamel&translucent porcelains,because they have the same basic physical &chemical properties. All these powders are basically same materials,they do differ in the appearance because of the modifiers. www.indiandentalacademy.com
    24. 24. STAINS & GLAZES Stain powders contain less silica or alumina &more sodium &potassium oxides. They contain high concentration of metallic oxides. They are created by mixing the metallic oxides with lower fusion point glasses www.indiandentalacademy.com
    25. 25. Glazes are generally colorless,low fusing porcelains. They possess considerable fluidity at high temperatures. They fill small surface porosities & irregularities.when fired helps to recreate the external glazy appearance of the natural tooth www.indiandentalacademy.com
    26. 26. ALLOYS FOR THE METAL CERAMICS www.indiandentalacademy.com
    27. 27.  REQUIREMENTS. (skinners 10th &Naylor's)  CLASSIFICATION.  A)BASED ON COLOR & COMPOSITION.  B)BASED ON FUNCTION.  C)AN ALTERNATIVE CLASSIFICATION.  D)ADA CLASSIFICATION.  DIFFERENT CONSTITUENTS &THEIR ROLE  DIFFERENT ALLOY SYSTEMS THEIR ADVANTAGES & DISADVANTAGES www.indiandentalacademy.com
    28. 28. Requirements of the alloys:1.A ceramic alloy must be able to produce surface oxides for chemical bonding with dental porcelain. 2.A metal ceramic alloy should be formulated so its coefficient of thermal expansion is slightly greater than that of the porcelain veneer to maintain the metal porcelain attachment.Even though oxides form & and the metal chemically bonds to the porcelain,fracture of the ceramic veneer may occur if the metal & the porcelain are not thermally compatible. www.indiandentalacademy.com
    29. 29. The alloy must have melting range considerably higher than the fusing range of the dental porcelain fired on to it. The alloy must not under go distortion at the the firing temperatures of the porcelain. The first four requirements must be balanced with technicians need for ease of handling. A casting alloy should be biocompatible. www.indiandentalacademy.com
    30. 30. CLASSIFICATION OF THE DENTAL CASTING ALLOYS They are classified based on :1.Alloy classification based on function. 2.Alloy classification based on color &composition. 3.The ADA classification for cast alloys. 4.An alternative classification system for metal ceramic alloys. www.indiandentalacademy.com
    31. 31. CLASSIFICATION BASED ON FUNCTION One of the oldest & simplest methods used to categorize casting alloys was devised by the NATIONAL BUREAU OF STANDARDS IN 1932. The gold based crown & bridge metals of that time were organized according to function into only four categories & described type1,2,3,or4alloys Alloys in each classification or type were arranged based on their gold &platinum group composition as well as the associated VHN. www.indiandentalacademy.com
    32. 32.  TYPE –1– SOFT.--- USED FOR THE SMALL INLAYS   TYPE –2– MEDIUM.--- USED FOR THE THREE QUARTER CROWN,THIN BACKINGS.  TYPE –3– HARD.--- USED FOR THE FULL CROWNS, ABUTMENTS & PONTICS.  TYPE –4—EXTRA HARD---DENTURE BASE BARS,PARTIAL DENTURE FRAME WORK, www.indiandentalacademy.com LONG SPAN FIXED PARTIAL DENTURE.
    33. 33. ALLOY CALSSIFICATION BASED ON COLOR &COMPOSITION A second method of classification is to describe alloys according to their color & principal element. 1.Yellow golds:- yellow color,greater than 60% of the gold content. 2.White golds:-white color but more than 50%of the gold content. 3.Low golds:-usually yellow colored with less than 60%of the gold. www.indiandentalacademy.com
    34. 34. High palladium:-white colored ,with palladium the major component.also contains small amount of gold &copper,cobalt. Silver- palladium:-white colored predominantly silver with substantial amounts of the palladium to provide nobility &to help control tarnish. Palladium- silver :-white colored with palladium the major component ,plus substantial component of silver. www.indiandentalacademy.com
    35. 35. ADA CLASSIFICATION In 1984 ADA prepared a new classification for cast alloys. The system was devised for the identification in dental procedure codes,where the intrinsic value of the metals in the castings provided to patient would influence the amount of reimbursement from insurance carriers. This system of the classification was not intended to indicate usage or performance levels. www.indiandentalacademy.com
    36. 36. ADA CLASSIFICATION  HIGH NOBLE:CONTAINS 40% GOLD,60% OF THE NOBLE METALS.(Au-Ir-Os-Pt-Ru)  NOBLE METAL:CONTAINS 25% OF THE NOBLE METAL ELEMENTS.  PREDOMINANTLY BASE METAL:CONTAINS LESS THAN 25% OF THE NOBLE METAL ELEMENTS. www.indiandentalacademy.com
    37. 37. AN ALTERNATIVE CLASSIFICATON SYSTEM With this method the alloys are classified based on composition & level of the constituent of the major content. The alloys are first divided into two groups, 1.Noble metal 2.Non noble metals. Each system further divided into constituent groups. www.indiandentalacademy.com
    38. 38. THE ROLE OF DIFFERENT CONSTITUENT ELEMENTS  Aluminum:-lowers the melting range of the nickel based alloys.  It acts as a hardening agent.  It influences the oxide layer formation.  With cobalt chromium alloys used for the metal ceramic restoration, aluminum is one of the element that is etched from the alloy surface to create micro mechanical retention for resin bonded retainers.  Melting range:660 degree centigrade; CTEwww.indiandentalacademy.com o.236
    39. 39. IRON: Iron is added to some gold based porcelain for hardening & oxide production.  Melting range:1527degree centigrade; CTE0.123  NICKEL:-it is base for the porcelain alloys.  Its CTE similar to the gold  It provides resistance to corrosion.  Melting range:1453degrees; CTE-0.133. www.indiandentalacademy.com
    40. 40. PALLADIUM: Palladium added to increase the corrosion, strength,hardness,tarnish resistance of the gold based alloys.  It increases the melting temperature.  Improves the sag resistance.  M.T.-1552; CTE-0.0188  PLATINUM:-It increases the strength,hardness,of the gold based alloys.  It improves the corrosion,tarnish &sag resistance.  It improves the density of the gold & non gold based alloys.  M.T.-1769; CTE-0.089 www.indiandentalacademy.com
    41. 41. SILICON: Silicon primarily as an oxide scavenger.  It also act as a hardening agent.  M.T.-1410; CTE-0.073.  SILVER: It lowers the melting range,improves the fluidity,&helps to control the CTE.  It has high affinity for the oxygen, which can lead to the porosity&gassing of the casting.  It is not universally regarded as noble in the oral cavity.  M.T.-960.8; CTE– 0.197. www.indiandentalacademy.com
    42. 42. TIN: Tin is the hardening agent that acts as a lower melting range of the alloy.  It also assists in oxide layer production for the porcelain bonding in gold based & palladium based alloys.  Tin is the one of the key trace elements for the oxidation of the palladium silver alloys.  M.T.-231.9;CTE-0.23 www.indiandentalacademy.com
    43. 43. BERYLLIUM:Lowers the melting temperature of the nickel based alloys. It improves the castability,improves polish ability. Helps to control the oxide layer formation. BORON:Boron is a de oxidizer. It reduces the surface tension there by increases the castability. Reduce the ductility & increase the hardness. www.indiandentalacademy.com
    44. 44. CHROMIUM: Chromium is a solid solution hardening agent that contributes to corrosion resistance.  M.T.-1875; CTE– 0.062.  COBALT:-used as alternative to the nickel based alloys.  Cobalt included in the high palladium alloys to increase the CTE.  It also acts a strengthener.  M.T.-1495; CTE– 0.138. www.indiandentalacademy.com
    45. 45. COPPER: The properties of the copper is same like aluminum.  M.T.—1083; CTE– 0.165.  GALLIUM: Gallium is added to silver free alloys to compensate the decreased CTE.  GOLD:-it provides the high levels of the tarnish &corrosion.  It increases melting range.  It improves the wettability,burnishability &increases the density.  M.T.—1063; CTE– 0.142. www.indiandentalacademy.com
    46. 46. DIFFERENT ALLOY SYSTEMS THEIR ADVANTAGES &DISADVANTAGES www.indiandentalacademy.com
    47. 47. HIGH NOBLE ALLOY SYSTEMS www.indiandentalacademy.com
    48. 48. Au-Pt-Pd       Advantages Excellent castability&porcelain bonding Easy to adjust &finish Tarnish&corrosion resistance Biocompatible Not technique sensitive  disadvantages  Poor sag resistance  Low hardness  Low density  High cost www.indiandentalacademy.com
    49. 49. COMPOSITION:Gold:75%-88% Platinum:-8% Palladium:-11% Silver:-5% www.indiandentalacademy.com
    50. 50. Au-Pd-Ag Composition:Gold:39%-53% Palladium:25%-35% Silver:12%-22% www.indiandentalacademy.com
    51. 51.  Advantages  Disadvantages  Less  Silver expensive  Improved rigidity&sag resistance  High nobility level content creates potential for porcelain discoloration.  High cost  High CTE  Tarnish &corrosion resistance www.indiandentalacademy.com
    52. 52. GOLD-PALLADIUM ALLOY SYSTEMS Gold:44%-55% Palladium:35%-45% Gallium:5% Indium & tin:8%-12% www.indiandentalacademy.com
    53. 53.  Disadvantages Advantages  Excellent castability  Good bond strength  Corrosion & tarnish resistance  Improved hardness & strength  Low density.  Not thermally compatible with expansion  High cost www.indiandentalacademy.com
    54. 54. NOBLE ALLOY SYSTEMS. www.indiandentalacademy.com
    55. 55. PALLADIUM – SILVER ALLOY SYSTEM Composition: Palladium:55%-60% Silver:28%-30% Indium & tin are used. The melting range of the this alloy system is 1021degrees-1099degrees centigrade. www.indiandentalacademy.com
    56. 56.  Advantages  Disadvantages  Low  Discoloration cost & density  Good castability & porcelain bonding  Low hardness  Excellent sag ,tarnish & corrosion resistance  Suitable for long span fpd’s  Pd-Ag prone to absorb gases  High CTE  May form internal oxides.  Should not be cast in carbon crucible www.indiandentalacademy.com
    57. 57. NICKEL-CHROMIUM-BERYLLIUM ALLOYS COMPOSITION: Nickel:62%-82% Chromium:11-20% Beryllium:2% www.indiandentalacademy.com
    58. 58.  Advantages   Low  cost  Low density  High resistance  It can produce thin castings  Poor thermal conductor  Can be etched.      Disadvantages Cannot be used with Ni sensitive patients Beryllium may be toxic to the technician & patients Bond failure may occur High hardness Difficult to solder Difficult to cut through cemented castings www.indiandentalacademy.com
    59. 59. NICKEL-CHROMIUM ALLOYS Composition: Nickel :62%-77% Chromium :-11%-22% www.indiandentalacademy.com
    60. 60. •Advantages  Do not contain beryllium  Low cost  Low density means more castings per ounce.  Disadvantages  Cannot be use with nickel sensitive patients  Produce more oxides than Ni-Cr-Be alloys.  May not cast as well as Ni-Cr-Be alloys www.indiandentalacademy.com
    61. 61. COBALT – CHROMIUM ALLOYS Composition: Cobalt:53%-68% Chromium:25%-34% Trace elements of molybdenum ruthenium are added. www.indiandentalacademy.com
    62. 62.  Advantages   Do  not contain nickel  Do not contain beryllium  Poor thermal conductors  Low density  Low cost    Disadvantages More difficult to process than Ni base alloys High hardness Oxide more than both Ni based alloys No information on long term clinical studies. www.indiandentalacademy.com
    63. 63.  THE MELTING TEMPARATURE OF THE HIGH NOBLE ALLOYS IS 1271DEGREE CENTIGRADE TO 1304 DEGREE CENTIGRADE.  FOR NOBLE METALS 1232 DEGREE CENTIGRADE TO 1304 DEGREE CENTIGRADE. www.indiandentalacademy.com
    64. 64. TOOTH PREPARATION FOR THE METAL CERAMIC RESTORATION www.indiandentalacademy.com
    65. 65.  Depth orientation grooves flat end tapered diamond. www.indiandentalacademy.com
    66. 66. www.indiandentalacademy.com
    67. 67.  Make at least two vertical cuts in the incisal portion of the facial surface. www.indiandentalacademy.com
    68. 68.  Next align the flat end tapered diamond with the gingival portion of the facial surface. www.indiandentalacademy.com
    69. 69.  Sink the side of the diamond into the mesiodistal center of the facial surface,maintain the instrument alignment parallel to the gingival surface of the facial segment. www.indiandentalacademy.com
    70. 70.  Make two incisal orientation grooves that are 2mm deep.The diamond should be parallel to the incisal edge faciolingally. www.indiandentalacademy.com
    71. 71.  Incisal reduction is done with the flat end tapered diamond. www.indiandentalacademy.com
    72. 72. www.indiandentalacademy.com
    73. 73.  Facial reduction; incisal half,flat end tapered diamond. www.indiandentalacademy.com
    74. 74.  If there sound tooth structure inter proximally, wing preparation is done. www.indiandentalacademy.com
    75. 75.  Begin the lingual reduction with the small round diamond with diameter of 1.4mm. Sink this instrument into the lingual tooth structure up to 0.7mm. www.indiandentalacademy.com
    76. 76.  Lingual axial reduction torpedo diamond and carbide finishing bur. www.indiandentalacademy.com
    77. 77.  Lingual reduction is done with the small wheel diamond. www.indiandentalacademy.com
    78. 78.  Smooth the entire facial surface with no.171 bur .Round over the any sharp angles on the incisal angle or along the edges of the incisal notches with no.171 bur. www.indiandentalacademy.com
    79. 79.  After the tooth preparation gingiva has to be retracted,impression is made with materials such as rubber base,which is the best material available for the impression procedures.  After this the working cast is obtained and the die pins are placed .  Apply die hardener,then die spacer and die separator.  Now the die ready for the wax pattern fabrication. www.indiandentalacademy.com
    80. 80. METAL SUB STRUCTURE DESIGN. www.indiandentalacademy.com
    81. 81.  FUNCTIONS.  DESIGN.  WAX PATTERN FABRICATION. www.indiandentalacademy.com
    82. 82. ESSENTIALS OF METAL CERAMIC SUB SRUCTURE  FUCTIONS OF THE METAL CERAMIC SUBSTRUCTURE:  1.Primary functions: The casting provides fit of the restoration to the prepared tooth.  The metal forms oxides that bond chemically to the dental porcelain.  The coping serves as a rigid foundation to which the brittle porcelain can be attached for increased strength & support. www.indiandentalacademy.com
    83. 83.  The sub structure restores the tooth's proper emergence profile. www.indiandentalacademy.com
    84. 84.  Metal SECONDARY FUNCTIONS:- occlusal & lingual articulating surfaces generally less destructive to the enamel of the opposing natural tooth.  Fabrication of the restoration with minimal occlusal clearance has more potential for the success with metal substructure than all ceramic alloys.  Occlusal surfaces can be easily adjusted &  repolished intraorally.  The metal axial walls can support the removable partial denture. www.indiandentalacademy.com
    85. 85. SUB STRUCTURE DESIGN FOR THE SINGLE UNIT RESTORATIONS.  Procedure for the maxillary anterior sub structure:  When restoring anterior teeth,more emphasis is placed on esthetics than any other single requirement.  There important factors to be considered for the restoration of the anterior teeth:  1.Location of the occlusal contacts.  2.Amount of the clearance. www.indiandentalacademy.com
    86. 86. LOCATION OF OCCLUSAL CONTACTS:  The mandibular anterior teeth contact the lingual surfaces of the lingual surfaces of the maxillary anterior teeth in the centric occlusion.  The location of the those contact areas should be identified with articulating film.  When these occlusal contacts appear in the incisal one half of the restoration,then the porcelain veneer may be extended over incisal edge for the occlusion in the porcelain. www.indiandentalacademy.com
    87. 87.  According to the concept of the mutually protected occlusion in centric occlusion the anterior teeth are out of the contact by approximately 25 microns or two thickness of shimstock.  The design of the lingual aspect of the metal ceramic depend on the clinician & patient. www.indiandentalacademy.com
    88. 88.  When the anterior teeth contact in the incisal region,it is often necessary to consider a design with lingual surface in porcelain to avoid functioning on or over the porcelain metal junction. www.indiandentalacademy.com
    89. 89.  Do not design the sub structure so contact occurs at the porcelain metal junction. www.indiandentalacademy.com
    90. 90.  When the anterior teeth occlude in the gingival half of the maxillary teeth or when the lingual tooth reduction is less than 1mm it is best to design the sub structure with occlusion in the metal. www.indiandentalacademy.com
    91. 91. AMOUNT OF THE CLEARENCE  One of the advantage of the restoring the lingual occlusion in the metal is less tooth reduction is required than for the full ceramic restoration.  It is depend on the clinician & dentist to give ceramic or the metal. www.indiandentalacademy.com
    92. 92. WAX PATTERN FABRICATION . www.indiandentalacademy.com
    93. 93.  THERE ARE THREE METHODS OF WAX PATTERN FABRICATION:  1.CUT BACK METHOD.  2.PLASTIC SHELL TECHNIQUE.  3.DIPPING MEHTOD. www.indiandentalacademy.com
    94. 94. STEP BY STEP PROCEDURE www.indiandentalacademy.com
    95. 95. CUT BACK PROCEDURE www.indiandentalacademy.com
    96. 96.  Scribe a line across the labial surface between 0.5-1mm above the marginal finish line.Also scribe a line across the labial surface 1.5mm from the incisal edge www.indiandentalacademy.com
    97. 97.  After completing the full contour wax up determine the location of the patient’s centric & eccentric occlusal contacts, then scribe a line for the porcelain metal junction. www.indiandentalacademy.com
    98. 98.  Remove the die & wax pattern form the master cast.connect the lines drawn for the porcelain metal junction. www.indiandentalacademy.com
    99. 99.  Reduce the incisal edge by at least 1.5mm to provide sufficient space to re-create the appearance of natural translucency yet avoid un supported porcelain. www.indiandentalacademy.com
    100. 100.  The wax pattern is now ready to be cut back.The objective of the cut back procedure is to remove a uniform thickness of approximately 1mm wax from all proximal surfaces of the substructure to receive porcelain. www.indiandentalacademy.com
    101. 101. use discoid carver,or similar instrument to refine the porcelain metal junction on the labial&lingual surfaces. www.indiandentalacademy.com
    102. 102.  Evaluate the cut back in the master cast for proper extension & adequate clearance by viewing it from all anglelabial,lingual&incisal. www.indiandentalacademy.com
    103. 103.  Measure the thickness of the wax pattern with the rounded tips of the Iwanson wax pattern. www.indiandentalacademy.com
    104. 104.  Smooth any sharp line angles to produce rounded contours.A cotton swab or Q-tip moistened with debubblizer and warmed by a flame can be used for this procedure. www.indiandentalacademy.com
    105. 105.  Finished www.indiandentalacademy.com wax pattern.
    106. 106. The recommended thickness of the wax pattern is0.3mm-0.5mm. It may vary the type of the alloy is used. www.indiandentalacademy.com
    107. 107. PROCEDURE FOR THE POSTERIORTEETH(CERAMIC FACING) www.indiandentalacademy.com
    108. 108.  WAX THE RESTORATION TO FULL CONTOUR & ASSES ITS CONTOUR FROM OCCLUSAL & FACIAL VIEWS. www.indiandentalacademy.com
    109. 109.  SCRIBE A LINE ON ON THE INNER INCLINE OF THE BUCCAL CUSP FROM DISTAL TO MESIAL THAT IS 2MM FORM ANY AREA OF THE OCCLUSAL CONTACT. www.indiandentalacademy.com
    110. 110.  Scribe the gingival & inter proximal lines for the proposed cut back.remove the die & wax pattern from the master cast and connect the occlusal inter proximal scribe line for the cut back. www.indiandentalacademy.com
    111. 111.  Complete the cut back then view the completed wax pattern from the occlusal and facial views. www.indiandentalacademy.com
    112. 112.  Carefully examine the cut back to make certain enough wax has been removed to ensure that ceramic veneer will be uniform in all areas www.indiandentalacademy.com
    113. 113. If the interproximal contact area is to be restored in porcelain rather than metal extend the cut back of the porcelain metal junction further lingually.  www.indiandentalacademy.com
    114. 114. www.indiandentalacademy.com
    115. 115. www.indiandentalacademy.com
    116. 116. www.indiandentalacademy.com
    117. 117. The disadvantage of cut technique are  Thinning the wax in the areas to be veneered with porcelain can create problems. The wax become fragile & breaks easily. Forces generating during th4e cut back procedure may distort the adaptation of the pattern. www.indiandentalacademy.com
    118. 118. WAX PATTERN FABRICATION FOR THE FIXED PARTIAL DENTURES. www.indiandentalacademy.com
    119. 119.  First full contour of the wax pattern is made.carefully inspect the inspect the wax pattern for the proper contours,& inter proximal areas. www.indiandentalacademy.com
    120. 120.  Mark the occlusion scribe line on the lingual surface of the wax up . www.indiandentalacademy.com
    121. 121.  Place a scribe line on the facial surface to indicate the extent of the incisal cut back. www.indiandentalacademy.com
    122. 122.  Place depth cuts in each unit & perform the facial cut. www.indiandentalacademy.com
    123. 123.  Refine the lingual surfaces with a carving instrument www.indiandentalacademy.com
    124. 124.  After the cut back,view the sub structure form the facial,incisal, and lingual views.There should be a 1mm gap between the pontics area and the soft tissue which will be covered by ceramic later www.indiandentalacademy.com
    125. 125. PALSTIC SHELL TECHNIQUE www.indiandentalacademy.com
    126. 126. Armamentarium 1. 4.0 cm spacer disks 2. 4.0 cm coping disks 3. Wire holding frame 4. Iris scissors www.indiandentalacademy.com
    127. 127.  Spacer disk is placed over the coping disk. www.indiandentalacademy.com
    128. 128.  Place the coping material and the spacer disk onto a wire holding frame www.indiandentalacademy.com
    129. 129.  Heat the disk slowly and evenly by holding them, approximately 10 cms above the flame. www.indiandentalacademy.com
    130. 130.  Place the heated coping disk and the spacer over the mouth of the moulding apparatus, a plastic jar filled with silicone putty. www.indiandentalacademy.com
    131. 131.  Press the trimmed die forcefully against the softened spacer and the coping disk until the finished line of the preparation completely submerges. www.indiandentalacademy.com
    132. 132.   This closely adapts the two disks over the tooth preparation.continue to exert the pressure against the disks with die until the sheet becomes cloudy.This will take approximately 10seconds. www.indiandentalacademy.com
    133. 133. • Heating the coping disk stretches it to the desired thickness of 0.3mm. www.indiandentalacademy.com
    134. 134.  Three cuts are made in the unadapted skirt of the disks with pair of iris scissors. www.indiandentalacademy.com
    135. 135.  The disks are pulled of the tooth preparation die. www.indiandentalacademy.com
    136. 136.  The spacer disks are peeled out of the coping shell. www.indiandentalacademy.com
    137. 137.  Excess border material is cut off 1.0mm above the preparation line. www.indiandentalacademy.com
    138. 138.  The trimmed shell is placed over the.the edges of the copings are about 1.0mm short of the finish line on the die. www.indiandentalacademy.com
    139. 139.  The 1.0mm gap between the shell and the finish line is filled with the wax. www.indiandentalacademy.com
    140. 140.  The benefits of the using plastic shell copings becomes apparent during the cut back stage.  The plastic coping provides rigidity & resist distortion. www.indiandentalacademy.com
    141. 141. FUNDAMENTALS OF SPRUING,INVESTING& CASTING www.indiandentalacademy.com
    142. 142.  SPRUING  TECHNIQUES  A)Methods (1)direct spruing.  (2)indirect spruing.  Sprue former placement.  Sprue former gauge.  Sprue former length.  Orientation of wax pattern.  Location of the reservoir. www.indiandentalacademy.com
    143. 143.  Sprue former composition:wax Vs plastic.  Prefabricated Sprue former. www.indiandentalacademy.com
    144. 144. TECHNIQUES A spruing system is intended to create a channel or series of channels in the set investment though which molten alloy flows to reach the pattern areas.  There is no single method of spruing that is universally accepted.  The manufacturer’s recommendations has to be followed for their alloy productions. www.indiandentalacademy.com
    145. 145. METHODS  Wax patterns can be sprued in one of two different methods.each method has it’s advantages & disadvantages. www.indiandentalacademy.com
    146. 146. DIRECT SPRUING With the direct spruing the flow of the molten metal is straight from the casting crucible to pattern area in the ring.  This method requires less time  PROCEDURE:  A straight Sprue former is luted to the thickest part of the wax pattern.  One end is to the wax pattern & other end is secured to the crucible former. www.indiandentalacademy.com 
    147. 147.  The sprue former can be modified by placing a ball or round reservoir between the pattern and the button.  Even with the ball reservoir, the spruing method is still direct.  Direct spruing is used to most frequently for the single units.  The draw back of this method is the potential suck back porosity at the junction of the restoration & the sprue. www.indiandentalacademy.com
    148. 148. INDIRECT TECHNIQUE  With the indirect spruing,the molten metal does not flow directly form the casting crucible into the pattern area.  The casting alloy takes a circuitous root before it reaches the pattern areas.  With this method of spruing,the connector bar is 6gauge or 8-gauge round wax to which the wax pattern sprue formers are attached on one side with two larger ingot sprue formers on the other side. www.indiandentalacademy.com
    149. 149.  Here the connector acts as a reservoir.  The composition of the alloy will influence the manner in which it fills the mold.  For Example: Palladium-Silver alloy fill the mold unidirectionally.  Type III gold fills the mold in a random fashion. www.indiandentalacademy.com
    150. 150.  The value of the indirect spruing for single crowns&bridges.  Although direct spruing can produce acceptable results, in many instances indirect spruing offers advantages such as greater predictability & reliability in the casting plus enhanced control of solidification shrinkage. www.indiandentalacademy.com
    151. 151. SPRUE FORMER PLACEMENT  The sprue former attached to the wax up should be luted to the thickest part of the pattern to allow the molten alloy to flow from regions large volume to lesser volume.  Placing the sprue former else where may result in the improper casting.  The most practical sprue location is the mid incisal area. www.indiandentalacademy.com
    152. 152. www.indiandentalacademy.com
    153. 153. SPRUE FORMER GAUGE A pattern sprue former of the sufficient size should be selected to supply the volume of alloy required of the patterns to the cast.  The round wax sprue former are conveniently identified with gauge No.10,8,6.  The larger the No. smaller the size of the sprue formers diameter. www.indiandentalacademy.com
    154. 154. SPRUE FORMER LENGTH.  With the direct spruing method, the sprue former should be long enough to position the wax patterns out side the heat center of the ring.  The length of the sprue former should be vary with the type & size of the crucible former & the casting ring used.  5mm of the pattern sprue former is often sufficient to connect the wax pattern & the connector bar. www.indiandentalacademy.com
    155. 155. ORIENTATION OF THE WAX PATTERN.  Attach the sprue to the thickest portion of the wax pattern.  Do not cerate sharp 90 degrees angles between the sprue former and the wax pattern or position the pattern so the alloy would have to flow back towards the ring entrance.  It is essential to take advantage if the gravitational force and the centrifugal forces by positioning the wax pattern such that the alloy is cast towards the thinner sections. www.indiandentalacademy.com
    156. 156.  Position the margins trailing edge of the casting ring. www.indiandentalacademy.com
    157. 157. LOCATION OF THE RESERVOIR  The reservoir of the spruing system,should be placed in the heat center of the ring.  This permits the reservoir to remain molten longer & enables it to furnish alloys to the patterns until they complete the solidification process.  This should have the largest mass of any part of the sprue system. www.indiandentalacademy.com
    158. 158. SPRUE FORMER COMPOSITION WAX Vs PLASTIC  Casting wax melts out by leaving 0.1% residue.  www.indiandentalacademy.com
    159. 159. PRE FABRICATED SPRUE FORMERS.  READY SPRUES:  The design of the prefabricated indirect sprue formers permits rapid placement of the pattern in the accompanying sprue former & consistent location of the reservoir bar in the oval casting ring. www.indiandentalacademy.com
    160. 160. TRI WAX SYSTEM:  The pre fabricated TRI WAX system from Williams dental company available as direct and indirect sprues.  Three sizes are available 6,8,10 gauge number.  The large indirect patterns are useful for the large pontics and thick molar wax patterns. www.indiandentalacademy.com
    161. 161. CASTING  TORCH SELECTION.  CHOICE OF THE FUELS.  CRUCIBLES.  LAWS OF CASTINGS. www.indiandentalacademy.com
    162. 162. TORCH SELECTION.  There are two types of the torches when selecting for the casting equipment.  1.Multi orifice torch.  2.Single orifice torch.  The tip mostly used for the metal ceramics is multi orifice.  Its main advantage is the distribution of heat over a wide area for more uniform heating of a alloy.  The single unit orifice concentrate more heat in one area. www.indiandentalacademy.com
    163. 163. www.indiandentalacademy.com
    164. 164. CHOICE OF FUELS  ACETYLENE:  This is a colorless gas with distinctive garlic odor.  It will burn in air & can generate a flame approaching 3000 degrees.  Acetylene is usually contaminated with the carbon and other elements.so it should not be used for the metal ceramic alloys. www.indiandentalacademy.com
    165. 165.  NATURAL GAS:  This fuel is a by product of the natural decomposition of the organic matter.  When mixed with air the natural gas flame approaches 2,200degrees.  Replacing the air with oxygen enables natural gas to attain temperatures required to melt high fusing noble & base metal alloys. www.indiandentalacademy.com
    166. 166.  Inadequate pressure in the gas lines,fluctuations in pressure levels,water contamination, variations in the compositions among the companies are some of the problems encountered by the natural gas users. www.indiandentalacademy.com
    167. 167.  PROPANE:  The problems with the natural gases are avoided when using bottle propane gas.  The constant regulated mix of pure,uncontaminated propane & oxygen provides a clean,consistent burn leading to a more ideal melt. www.indiandentalacademy.com
    168. 168. CASTING CRUCIBLES  Either zircon-alumina or quartz casting crucible are recommended for noble & base metal alloys.  Carbon crucible well suits for the gold alloys.  But there is chance of the carbon contamination leads to lessen the strength of the alloys. www.indiandentalacademy.com
    169. 169.  After selecting the appropriate type of the casting crucible,pre heat it in the oven to avoid spalling & prolongs the life of the crucible.  Never cast different alloys in the same crucible as this causes contamination.  Carve the alloy name on the crucible for identification.  Do not use the asbestos liner in the crucible or flux in the molten metal. www.indiandentalacademy.com
    170. 170. THE LAWS OF CASTING  INGERS0LL & WANDLING formulated an expanded set of 17 separate recommendations for spruing, investing, burnout, melting & casting. Collectively, these guide lines are referred to LAWS OF CASTING. www.indiandentalacademy.com
    171. 171. THE FIRST LAW OF CASTING  Attach the pattern sprue former to the thickest part of the wax pattern.  As the molten alloy moves from the reservoir to the pattern margins it should flow from greater volume to lesser volume areas.  Lute the pattern sprue former to the most practical portion wax pattern.  Molten metal flowing form a thin area to a thicker region may solidify before the mold is completely filled. www.indiandentalacademy.com
    172. 172.  The penalty for not obeying this law are cold shuts, short margins, & incomplete castings www.indiandentalacademy.com
    173. 173. SECOND LAW OF CASTING.  Orient wax patterns so all the restorations margin will face the trailing edge when the ring is positioned in casting machine.  To identify the orientation add a wax dot to the crucible former.This helps as guide to place the ring in the crucible.  The penalties for not obeying this laws are cold shuts, & short margins. www.indiandentalacademy.com
    174. 174. THIRD LAW OF CASTING  Position the wax pattern in the cold zone of the investment mold & the reservoir in the heat center of the casting.  The coolest part of the mold are at the end of ring & along the ring periphery.  The hottest portion of the casting ring is located near the center of the ring.  Limit the amount of the investment covering the pattern to no more than ¼ in.  The penalty for not obeying this law shrinkage, porosity in the restoration. www.indiandentalacademy.com
    175. 175. FOURTH LAW OF CASTING A reservoir must have sufficient molten metal to accommodate the shrinkage that occurs with in the restoration.  Alloy that fills the restoration solidify first.as that solidifies,it shrinks and create a vacuum.For completing casting , the vacuum must be able to draw additional metal form an adjacent source – the reservoir.  The penalties for not obeying this law are shrinkage porosity& suck back porosity. www.indiandentalacademy.com
    176. 176. FIFTH LAW OF CASTING  Do not cast a button if a connector bar or other internal reservoir,is used.  With indirect spruing, largest mass of the metal should be the reservoir.A button is counter productive because it can draw available molten alloy from the bar.  Shift the heat center & reduce the feed of the metal to the restorations.  Like wise the wax patterns should not be larger than connector bar. www.indiandentalacademy.com
    177. 177.  The penalties not obeying this law are shrinkage porosity, distortion, & suck back porosity. www.indiandentalacademy.com
    178. 178. SIXTH LAW OF CASTING  Turbulence must be minimized if not totally eliminated.  Pathways for the flow of the metal should be smooth, gradual & with out impediments.  Eliminate sharp turns retractions,points,or impingements.  That might create turbulence & occlude air in the casting.  The penalties not obeying this law are voids,surface pitting,mold wash. www.indiandentalacademy.com
    179. 179. SEVENTH LAW OF CASTING  Select a casting ring of a sufficient length & diameter to accommodate the patterns to be invested.  The casting ring should permit the patterns to be ¼ in.apart & 1/4in from the top of the investment with minimum 3/8in of the investment between them & the ring liner.  Less investment-alloy break through the investment.  Too much investment-impairs the escape of the gases. www.indiandentalacademy.com
    180. 180.  Mold fracture casting fails & shrinkage porosity. www.indiandentalacademy.com
    181. 181. EIGHTTH LAW OF CASTING  Increase the wettability of the wax patterns.  A wetting agent should be brushed or sprayed on the patterns and dry before investment.  A clean wax surface better enables the casting investment to wet the patterns more completely.  Too much of the wetting agent-weaken the investment & produce bubbles.  The penalties for not obeying this law are :bubbles www.indiandentalacademy.com
    182. 182. NINTH LAW OF CASTING  Weigh the bulk of the investment & measure the investment liquid for a precise powder:liquid ratio.  The correct proportions of powder to liquid and any dilution of the liquid with distilled water should be established for each alloy.  Thick mix of the investment-more expansionloose fittings.  Thin mix of the investment-less expansion-tight fittings. www.indiandentalacademy.com
    183. 183. TENTH LAW OF CASTING  Eliminate the incorporation of air in the casting investment and remove the ammonia gas by product of phosphate bonded investment by mixing under vacuum. www.indiandentalacademy.com
    184. 184. 11th LAW OF CASTING  Allow the casting investment to set completely before initiating the burnout procedure.  The penalties for not obeying this law are mold cracking, blow out. www.indiandentalacademy.com
    185. 185. 12th LAW OF CASTING.  Use a wax elimination (burnout) procedure that is specific for the type of pattern involved & recommended for the particular type of casting alloy selected.  Plastic sprues has to be heated slowly so they can soften gradually & not exert pressure on the mold.  If burnout is incomplete,the spruing system channels may be blocked by plastic or wax residue. www.indiandentalacademy.com
    186. 186.  The penalties for not obeying this law colds shuts, short margins, cold welds, mold cracks. www.indiandentalacademy.com
    187. 187. 13th LAW OF CASTING  Adequate heat must be available to properly melt and cast the alloy.  Prolonged heating-by improperly adjusted torchprevent the alloy from attaining the fluidity.  Too much of heat or too high temperature can off minor alloying elements.  The penalties for not obeying this law are cold shuts, short margins, cold welds, rough castings, investment break down. www.indiandentalacademy.com
    188. 188. 14th LAW OF CASTING  When torch casting, use the reducing zone of the flame to melt the alloy & not the oxidizing zone.  Improperly adjusted torch-adds carbon.  Reducing zone- minimize the gas absorption.  Penalties:gas porosity,change in alloy’s CTE www.indiandentalacademy.com
    189. 189. 15th LAW OF CASTING  Provide enough force to cause the liquid alloy to flow in to the heated mold.  Adjust the casting machine to the requirements of each alloy.  Low density metal generally needs 4 winds of a centrifugal casting arm.  Penalties:cold shuts, short margins, cold welds, mold fracture. www.indiandentalacademy.com
    190. 190. 16th LAW OF CASTING  Cast towards the margins of the wax patterns.  Place the heated in the casting cradle using the orientation dot.So the pattern margin face the trailing edge.  In the centrifugal casting machine the metal will flow downwards and to the right,taking advantage of centrifugal, rotational, gravitational forces on the molten alloy.  Penalties: cold shuts, short margins, incomplete castings. www.indiandentalacademy.com
    191. 191. 17th LAW OF CASTINGS  DO NOT QUENCH THE RING IMMEDIATELY AFTER CASTING.  UNEVEN COOLING-APPLY TENSILE FORCES TO THE CASTING.  AFTER CASTING THE ALLOY MAY NOT HAVE THE SUFFICIENT STRENGTH TO RESIST THESE FORCES & RESTORATION COULD TEAR. www.indiandentalacademy.com
    192. 192. Thank you For more details please visit www.indiandentalacademy.com www.indiandentalacademy.com

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