Alloys for pfm /cosmetic dentistry training


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  • Alloys for pfm /cosmetic dentistry training

    1. 1. ADA CLASSIFICATION • In 1984 ADA given classification of alloys that are used for the metal ceramic restorations. • They are classified as, • High noble. • Noble. • Predominantly base
    2. 2. HIGH NOBLE METAL ALLOYS. INDIAN DENTAL ACADEMY Leader in continuing dental education
    3. 3. HIGH NOBLE ALLOY SYSTEMS. • Au-Pt-Pd. • Au-Pd-Ag. • Au-Pd.
    5. 5. Au-Pt-Pd
    6. 6. COMPOSITION:- Gold:75%-88% Platinum:-8% Palladium:-11% Silver:-5% Trace elements of indium,iron,&tin are used for the porcelain bonding.
    7. 7. 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. •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.
    8. 8. •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.
    9. 9. 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
    10. 10. •GOLD:-it provides the high levels of the tarnish &corrosion. •It increases melting range. •It improves the wettability,burnishability &increases the density.
    11. 11. Au-Pd-Ag Composition:- Gold:39%-53% Palladium:25%-35% Silver:12%-22%
    12. 12. • Advantages • Less expensive • Improved rigidity&sag resistance • High nobility level • Disadvantages • Silver content creates potential for porcelain discoloration. • High cost • High CTE • Tarnish &corrosion resistance
    13. 13. GOLD-PALLADIUM ALLOY SYSTEMS Gold:44%-55% Palladium:35%-45% Gallium:5% Indium & tin:8%-12%
    14. 14. • Excellent castability • Good bond strength • Corrosion & tarnish • Improved hardness & strength • Low density. • Disadvantages • Not thermally compatible with expansion • High cost Advantages
    16. 16. • Pd-Au. • Pd-Au-Ag. • Pd-Ag. • Pd-Cu. • Pd-Co. • Pd-Ga-Ag
    17. 17. PALLADIUM – SILVER ALLOY SYSTEM Composition: Palladium:55%-60% Silver:28%-30% Indium & tin are used.
    18. 18. • PALLADIUM:-- palladium is added to increase the strength, hardness, corrosion&tarnish resistance. • It elevates the alloy’s melting temperature. • It improves the sag resistance. • Palladium possess the a high affinity for the hydrogen,oxygen& carbon. • It lowers the density of the gold based alloys.
    19. 19. • TIN:- • Tin is the hardening agent that acts as a lower melting range of the of an 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.
    20. 20. • Advantages • Low cost & density • Good castability & porcelain bonding • Low hardness • Excellent sag ,tarnish & corrosion resistance • Suitable for long span fpd’s • Disadvantages • Discoloration • Pd-Ag prone to absorb gases • High CTE • May form internal oxides. • Should not be cast in carbon crucible
    21. 21. PALLADIUM-COBALT • composition: • palladium78%-88%. • cobalt 4%-10% • • trace elements of gallium,indium are used.
    22. 22. • Cobalt is used for alternative of the nickel based alloys, but the cobalt based alloys are difficult to process.] • Cobalt is added to in palladium alloys to increase the CTE,& acts as a strengthener.
    23. 23. • Advantages. • Low cost • Good sag resistance • Good castability,polishabiliy • Easier to solder • Disadvantages • Compatible with high expansion porcelains. • Produce a thick,dark.oxide colored layer may cause bluing of the porcelain. • More prone to gas absorption.
    24. 24. PALLADIUM-COPPER • palladium 70-80% • copper 9-15% • gold 1-2% • platinum 1-2%
    25. 25. • COPPER:- • Copper serves as hardening agent. • Lowers the melting range of alloy. • It helps to form an oxide layer for porcelain bonding. • It lowers the density.
    26. 26. • Advantages. • Good castability. • Low cost than gold. • Good tarnish and corrosion resistant. • Compatible with dental porcelains. • Produce dark,thick oxide layer. • May discolor some porcelains. • Should not be cast in the carbon crucibles. • Absorbs gases. • Suitable for the long span bridges. • Difficult to polish. • High hardness
    27. 27. Pg-Ag-Au • composition: • palladium 75-86% • silver 1-7% • gold less than 1% • Trace amounts of indium & gallium are found.
    28. 28. • Advantages • Low cost • Low density • Improved sag resistance. • Light colored oxide layer. • Relatively new alloy group no data on long term performances. • Prone to gaseous absorption. • Should not be cast in carbon crucibles.
    29. 29. • INDIUM:- • Lowers the melting range of the alloy. • It improves the fluidity. • It has strengthening effect. • It is added to non gold based alloys to form an oxide layer. • It enhances the tarnish & corrosive resistance.
    30. 30. • GALLIUM: • It is added to the silver free porcelains to compensate for the decreased CTE created by silver removal.
    32. 32. • Ni-Cr-Mo-Be • Ni-Cr-Mo • Co-Cr-Mo
    33. 33. NICKEL-CHROMIUM-MOLYBDENUM- BERYLLIUM ALLOYS COMPOSITION: Nickel:62%-82% Chromium:11-20% Beryllium:2%
    34. 34. •NICKEL:-it is base for the porcelain alloys. •Its CTE similar to the gold •It provides resistance to corrosion. Lowers the melting temperature of the nickel based alloys. It improves the castability,improves polish ability. Helps to control the oxide layer formation BERYLLIUM:-
    35. 35. • 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 the on of the element that is etched from the alloy surface to create micro mechanical retention for resin bonded retainers.
    36. 36. • IRON:- • Iron is added to some gold based porcelain for hardening & oxide production. SILICON:- •Silicon primarily as an oxide scavenger. •It also act as a hardening agent.
    37. 37. • 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
    38. 38. NICKEL-CHROMIUM ALLOYS Composition: Nickel :62%-77% Chromium :-11%-22%
    39. 39. •Chromium is a solid solution hardening agent that contributes to corrosion resistance. CHROMIUM:-
    40. 40. BORON:- Boron is a de oxidizer. It reduces the surface tension there by increases the castability. Reduce the ductility & increase the hardness.
    41. 41. • 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
    42. 42. COBALT – CHROMIUM ALLOYS Composition: Cobalt:53%-68% Chromium:25%-34% Trace elements of molybdenum ruthenium are added.
    43. 43. CHROMIUM:- • Chromium is a solid solution hardening agent that contributes to corrosion resistance. • 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.
    44. 44. • Molybdenum improves corrosion resistance,influences the oxide layer,helpful in adjusting CTE in nickel based alloys.
    45. 45. • RUTHENIUM: • It acts as a grain refiner. • It improves the tarnish resistance.
    46. 46. • 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.
    47. 47. SOLDERING.
    48. 48. • SOLDERING:-A group of process that join metal by heating them to a suitable temperature below the solidus of the substrate metals & applying a filler metal having liquidus not exceeding 450 degree centigrade that melts and flows by capillary attraction between the parts with out appreciably affecting the dimension of joined structure. • In dentistry,many metals are joined by brazing,although,the term soldering is used.
    49. 49. • BRAZING:The process of joining metals above 450 degree centigrade. • WELDING:-The joining of two or more metal pieces by applying heat, pressure,or both with or without filler material, to produce localized union across the interface through fusion or diffusion. • SOLDERING FLUX: A material used to prevent the formation of,or to dissolve & facilitate removal of,oxides & other undesirable substances that may reduce the quality or strength of the soldered metal structure.
    51. 51. PHYSICAL REQUIREMENTS OF SOLDER MATERIALS • Resistance to tarnish & corrosion. • Fusion temperature 90-180 degree Fahrenheit below the parts to be joined. • Free flowing when melted. • Resistance to pitting. • At least as strong as the parts to be joined. • Color compatible with the parts to be joined.
    52. 52. SOLDERING FLUXES • Flux is Latin word means flow.Dental do not flow or wet the metallic surfaces that have an oxide layer.The flux aid in the removal of the oxide layer so as to increase the flow of the molten solder. • In addition the flux also dissolves the impurities,prevents the oxidation of the metals. • Fluxes used commonly are: • Borax glass– 55%. • Boric acid --35% • Silica-- 10%.
    53. 53. • ANTI FLUX • Anti flux is a material that is used to confine the flow of the molten solder over the metals being joined. • The commonly used anti fluxes are pencil markings, graphite lines, iron rouge.
    54. 54. Fundamental considerations • Position accurately the uncontaminated parts to be joined. • Determine the solder gaps and configuration. • Place the flux and solder within the joint space. • Heat the parent metal and solder until the solder flows, filling the joint space. • Remove the heat as soon as possible. • Inspect the connection and correct f necessary. • Gap to be maintained is 0.3mm.
    55. 55. • ARMAMENTAIRUM • Plaster bowl & spatula • Impression plaster. • Bite registration paste. • Index tray or tongue blade. • Petrolatum. • Laboratory knife with no.25 blade. • PKT waxing instrument no 1& 2. • Straight hand piece. • Soldering investment. • Vibrator.
    56. 56. • Fisher burner & matches. • Tripod screen. • Solder • Blow pipe. • Tooth brush.
    57. 57. • Remove the provisional restoration from the patient’s mouth make certain that there are no temporary cement left on the tooth preparation. • Try in the single retainer first and then retainer pontic combination, verify the marginal fit • Adjust the occlusion, do not polish the casting at this stage.because polishing rouge is iron-di- oxide, a specific anti flux for soldering.
    58. 58. • Mix a small amount of fast setting impression plaster & place it on plastic index tray or thoroughly wet tongue depressor.
    59. 59. 1. Place the tray in the mouth over the castings.once the plaster set, remove the template and check for the accuracy
    60. 60. • Trim the excess plaster so that after seating the template, it is possible to cover their margins with soldering investment.lute the castings with the sticky wax.
    61. 61.
    62. 62. • A strip of boxing wax 2.5mm thick wide wrapped around the index.
    63. 63.
    64. 64. • Mix the soldering investment according to the manufacturer instructions.completel y fill the interior of the retainer castings. Care to avoid burying the prosthesis in the investment.
    65. 65. • Remove the plaster template & trim the investment so, that soldering model allows the ready access of heat to the joint area.
    66. 66. • Heat the soldering model sufficiently to vaporize wax remaining in the joint.
    67. 67. • While the joint is still warm coat the solder with flux and place the solder in the place.
    68. 68. • Reheat the soldering model until the solder flows. • Remove the flame, apply bluish flame in circular manner around the solder model. • As the solder is about to flow; it slumps and loses rectangular definition. • Use only reducing portions of the flame, characterized by shiny areas on the metal directly under the flame. • Allow the prosthesis for the bench cool to heat treat the metals properly. • Try the assembled prosthesis in the mouth after finishing &
    70. 70. • Try in the units in the mouth & make necessary adjustments. • Remove the FPD from the mouth,cut the joint using disk. • A soldering index is made with the quick setting plaster.
    71. 71. • Making the plaster index.
    72. 72.
    73. 73. • Cyanoacrylate liquid resin is squeezed onto the joint space.
    74. 74. • To prevent investment form contaminating the ceramic place 1.0mm thick ivory wax over gingival one half to 2/3rd of the facial surfaces of the retainer and pontic.
    75. 75. • Mix a small amount of the soldering investment and carefully vibrate into the crowns.
    76. 76. • Soldering investment is placed over the flat surface.
    77. 77. • Put the FPD into the investment.
    78. 78. • Investment is pushed over the lingual surfaces of the FPD
    79. 79. • The investment is trimmed leaving 3.0mm around the castings. The entire block is beveled.
    80. 80. • A V shaped notch is placed over the lingual surface.
    81. 81. • The wax layer separates the investment and porcelain.
    82. 82. • After the wax removal, a space between porcelain and investment protects the porcelain.
    83. 83. MECHANISM OF PORCELAIN –METAL ATTACHMENT • Four theories have been proposed to explain the processes that lead to porcelain-to-metal bonding: • 1. Van der waals forces. • 2. Mechanical retention. • 3. Compression bonding. • 4. Direct chemical bonding.
    84. 84. VAN DER WAALS FORCES. 1. The attraction between charged atoms that are in intimate contact yet do not actually exchange electrons is derived from van der waals forces. 2. These secondary forces are generated more by a physical attraction between charged particles than by an actual sharing or exchange of electrons in primary(chemical) bonding. 3. Van der waals forces are generally weak, because nearly all the positive and negative charges present in these atoms are satisfied in a single molecule.
    85. 85. 4. It is also believed that bonding entails some measure of true adhesion based on the extent to which the metal substructure is wetted by the softened dental porcelain. 5. The better the wetting of the metal surface, greater the vanderwaal’s forces. 6. Furthermore, porcelain’s adhesion to metal can be diminished or enhanced by alterations in the surface characters(texture) of the porcelain-bearing surface on the substructure.
    86. 86. 7. A rough, contaminated metal surface will inhibit wetting and reduce the vanderwaals bond strength. On the other hand, a slightly textured surface, created by finishing with uncontaminated aluminum oxide abrasives and followed by air abrasion(blasting) with 50 microns aluminium oxide, reportedly will promote wetting by the liquid porcelain. 8. Improved wetting is then accompanied by an increase in adhesion through vanderwaals forces.
    87. 87. MECHANICAL RETENTION: • 1. The porcelain-bearing area of a metal casting contains many microscopic irregularities into which opaque porcelain may flow when fired. • 2. Air abrading the metal with aluminum oxide is believed to enhance mechanical retention further by eliminating surface irregularities ( stress concentrations) while increasing the overall surface area available for bonding.
    88. 88. 3. Despite it’s presence, mechanical retention’s contribution to bonding may be relatively limited. 4. Dental porcelain does not require a roughened area to bond to metal. In fact porcelain will fuse to a well polished surface, but some surface roughness is effective in increasing bonding forces.
    89. 89. COMPRESSION BONDING • Dental porcelain is strongest under compression and weakest under tension. • Hence , if the coefficient of thermal expansion of the metal substructure is greater than that of the porcelain placed over it, the porcelain should be placed under compression on cooling. • 1. When cooling a restoration with a full- porcelain veneer, the metal contracts faster than the porcelain but is resisted by the porcelain’s lower coefficient of thermal expansion.
    90. 90. • 2. This difference in contraction rates creates tensile forces on the metal and corresponding compressive forces on the porcelain. Without the wraparound effect created in a full porcelain restoration, there is less likelihood this compression bonding will develop fully.
    91. 91. THERMAL EXPANSION • Generally substances increase in the length and volume when they are heated. This phenomenon is called as thermal expansion. • The specific rate of change in length of a particular substance per unit change in temperature is called coefficient of linear expansion. • The rate of change in volume is called coefficient of cubical expansion. • These may generally be called coefficient of thermal expansion or simply thermal expansion.
    92. 92. RELATION BETWEEN METAL AND PORCELAIN • When porcelain is fused to metal, three possible relations can exist in thermal expansion: • 1. Thermal expansion (or contraction) is greater in porcelain than in metal. • 2. Thermal expansion (or contraction) is equal between metal and porcelain. • 3. Thermal expansion (or contraction) is greater in metal than in porcelain.
    93. 93. THERMAL EXPANSION IS GREATER IN PORCELAIN THAN IN METAL. • Greater thermal expansion in porcelain means that during the time after porcelain has lost thermoplastic fluidity in the course of cooling, but after melting of porcelain at high temperature, porcelain is apt to contract to be smaller and shorter than metal until it reaches room temperature. • Therefore, assuming that they are separated, there will be a difference in length between them.
    94. 94. • Hence porcelain becomes shorter after cooling although they had the same length before heating. • In the ceramo-metallic system, porcelain side is subjected to tensile stress while the metal side is subjected to compressive stress as they are fused together. As a result, the porcelain, which is very weak against tensile stress, will crack immediately.
    95. 95. THERMAL EXPANSION IS EQUAL BETWEEN METAL AND PORCELAIN • As metal and porcelain expand or contract at the same rate, there will be no difference in dimensions between them at all. • As a result, porcelain receives no stress from metal and thus cracking does not occur in the stable porcelain unless undue external force is applied. • It is very difficult, however, to obtain the identical curves for coefficient of thermal expansion between porcelain and metal, and under ordinary conditions there is a discrepancy to some
    96. 96. THERMAL EXPANSION IS GREATER IN METAL THAN IN PORCELAIN. • In general, this thermal expansion relationship exists between metal and porcelain in the dental metal-ceramic system. • The objective of such a relationship is to obtain the most stable assembly after firing. • Fractures do not usually occur since porcelain has very high compression strength, although the porcelain side is subjected to compressive stress as the metal contracts more than porcelain during cooling to ambient temperature after firing.
    97. 97. • However, this does not mean that cracking will never occur. • If there is a significant difference in thermal expansion between metal and porcelain, a shearing force acts on their interface, and if stress is sufficiently great, cracking, or fracture may occur.
    98. 98. CHEMICAL BONDING • The single most significant mechanism of porcelain-metal attachment is a chemical bond between dental porcelain and the oxides on the surface of the metal substructure. • There are those who believe that two mechanisms might exist within the chemical (or molecular) bonding theory. • According to one hypothesis,the oxide layer is permanently bonded to the metal substructure on one side while the dental porcelain remains on the other.
    99. 99. • The oxide layer itself is sandwiched in between the metal substructure and the opaque porcelain. • This sandwich theory is undesirable in that a thick oxide layer might exist that would weaken the attachment of metal to porcelain. • The second, and more likely, theory suggests that the surface oxides dissolve, or are dissolved by the opaque porcelain layer. • The porcelain is then brought into atomic contact with the metal surface for enhanced wetting and direct chemical bonding so metal and porcelain share electrons.
    100. 100. • From a chemical standpoint, both covalent and ionic bonds are thought to form but only a monomolecular( single) layer of oxides is believed to be required for chemical bonding to occur.
    101. 101. PORCELAIN METAL BOND FAILURES • Metal ceramic alloys, whether noble or base metals, all oxidize differently because of variations in their composition. • If the oxidation process is not performed properly,the subsequent porcelain-metal bond may be weak. The consequences of bond failure,be the failure immediate or delayed,obviously costly.
    102. 102. PORCELAIN DELAMINATION • With base metal alloys, the separation of porcelain veneer from the metal sub structure can be more a loss of the attachment of the oxide layer that is either too thick or is poorly adherent to the metal sub structure. • The porcelain and oxide film retain their bond yet become detached or delaminated at the porcelain-metal junction. • Over oxidation is the particular problem with heavily oxidizing base metals
    103. 103. • In some instance bond failure may not be due to chemical bond contrarary,it may be due to too thick of the oxide layer or poor adherence of the oxide layer to the metal structure. • Excessive absorption of the oxides by porcelains can lower the coefficient of thermal expansion.
    104. 104. INCOMPITENT MATERIALS • Bond failure may occur due to physical incompatibility between porcelain and metal. • The difference in the coefficient of thermal expansion of porcelain and the metal may contribute to the failure of the bonding.
    105. 105. OVER OXIDATION/UNDER OXIDATION • The oxidation procedure varies for alloys of different the process it self should not be taken for granted. • No one technique can be used for every type of metal ceramic alloy. • Careful processing followed by an assessment of post oxidation appearance of each casting will ensure that the procedure was accomplished correctly.
    106. 106. • Over oxidation or under oxidation should be reprocessed accordingly until uniform oxide of desired color and thickness recommended for the alloy involved.
    107. 107. CONTAMINATION • That that are demonstrated some form of contamination may not have to be remade. • Simple finishing, a substructure’s porcelain bearing area may be all that is necessary when surface de bonding becomes evident.
    108. 108. POCELAIN APPLICATION METHODS • INSTRUMENTS AND EQIUPMENTS: • Brushes • Carving instruments • Spatula • Razor knifes • Hemostat • Condensation mallet or instrument. • Glass or ceramic mixing slab
    109. 109. PORCELAIN FURNACE • Three types of the furnaces are available: • Manual. • Automatic. • Programmable. • There certain futures common to all types of the furnaces. • For example all low fusing porcelain are fired under vacuum rather than in atmospheric, all furnaces are equipped so the firing chamber or muffle can be sealed and, with the aid of a pump,establish & maintain a vacuum during firing.
    110. 110. • In the event the vacuum does not reach an adequate level, or if the firing chamber does not properly seal, resulting in a loss of vacuum during the firing cycle, the quality of the fired porcelain will be compromised. • There will be significant loss of the translucency, And vitality in the fired porcelain. A porcelain furnace should have an adjustable rate of climb from the low entry temperature up to high firing temperature.
    111. 111. • Most furnaces can also be set to hold the work at a temperature for a a specified length of time as determined by case by case. • There two basic categories depending on the manner of entry into the muffle. • Form front to back • Front loading furnaces. • The front loading furnaces hotter near back of the muffle and cooler near door. • Those sub structures oxidized in the rear most portion of the muffle will have a significantly heavier oxide layer
    112. 112. • Furnaces in the second category have a vertical entry in to the muffle. With the vertical loading design,the muffle flat form with the restoration in the center is raised up to furnace muffle. • The vertical loading design reportedly provides a more uniform temperature distribution throughout the muffle and allows the work to be completely surrounded by the heating elements.
    113. 113. PORCELAIN CONDENSATION • Capillary action. • Vibration. • Spatulation. • Whipping. • Dry powder addition.
    114. 114. CAPILLARY ACTION • The technique of bottling a wet build up with absorbent paper uses surface tension to with draw liquid and packs the porcelains particle together. • Capillary action or surface tension alone does not remove all available liquid. • The cyclic action of vibration,or whipping followed by bottling is repeated until free liquid can no longer be forced to the surface of porcelain. • Usually delicate touch require to initiate this mechanism.
    115. 115. • An overly aggressive technique could dislodge the porcelain buildup form underlying metal sub structure.
    116. 116. VIBRATION • The easiest and simplest form of vibration created by passing serrated instrument over the neck of the hemostat. • If the restoration is left on the cast,the entire cast can be tapped or vibrated. • Whether the restoration is vibrated on hemostat or on cast the end result of vibration will be to force the excess water to the porcelain surface. • At this point, with the help of tissue paper the surface liquid is removed.
    117. 117. • There several devices to provide mechanical vibration such as, vibrating brushes, spatulas,and ultrasonic condensers. • Surface tension is the force that causes all liquids to contract to their smallest possible surface area. • This property accounts for the transformation of the water droplets in to the spherical mass. • In a wet bulk of porcelain, this force helps to pack the porcelain more tightly when vibrating & bottling.
    118. 118. SPATULATION • With this form of condensation,a spatula or porcelain carver is used to apply,rub the porcelain buildup to force the liquid to the surface. • This technique brings with it a greater likelihood of porcelain dislodgement, particularly if too much pressure is used especially with initial build up.
    119. 119. WHIPPING • This method actually be nothing more than variation of vibration technique. • As the porcelain built up, a no. 10 sable brush is rapidly moved over the porcelain surface with a whipping motion.the whipping action brings the liquid to the out side surface of the bottling.
    120. 120. DRY POWDWER ADDITION: • This method is less widely used. • This technique also referred as brush application method. • Dry porcelain powder sprayed over the wet porcelain surface. • This uses the existing liquid to moisten the powder addition.
    123. 123. GLASS ROD TECHNIQUE • First, lightly wet the oxidized metal metal substructure to be veneered with distilled water and gently vibrate the casting for thorough wetting.
    124. 124. • Use point end of glass rod to apply the opaque porcelain.begin the opaquing most convex portion of the metal.
    125. 125. • Move the opaque towards the porcelain metal junction from one inter proximal area to to other & cover the incisal area.
    126. 126. • Lightly tap the hemostat with metal instrument to condense the opaque porcelain and excess opaquing liquid will raise to the surface.
    127. 127. • Place the edge of tissue,against the an edge of the moist opaque porcelain.hold the tissue in place until the liquid is absorbed and takes on a dull appearance.
    128. 128. • Blend the opaque at the porcelain metal junction to establish a gradual transition from opaque to external surface.
    129. 129. BRUSH TECHNIQUE • Opaque can also be applied with the brush.load the brush tip with opaque porcelain and carry it to the coping.
    130. 130. • Application of the opaque twice is also recommended.initially thin layer of the opaque and complete masking is followed.
    132. 132. • Carefully return the cleaned,opaqued coping to the master folded tissue or bottling paper on the lingual side of the restoration.
    133. 133. • To minimize the potential for entrapping air in the porcelain, move the tip of the pointed brush through the mixed dentin porcelain.remove the brush with dentin porcelain captured on the brush tip.
    134. 134. • Apply the porcelain to the most convex area on the restoration.
    135. 135. • Gently push the porcelain to the intrproximal,incisal areas.
    136. 136. • Move the porcelain down to the incisal edge and lightly blot the build up to condense the porcelain on the substructure.
    137. 137. • To create the mesial- facial line angle,wipe the brush to dry it slightly and reduce the pointing then lightly move from the mesial gingival area to mesial-incisal area.
    138. 138. • Point the brush and add additional dentin porcelain to lingual aspect of the incisal edge.smooth and condense the incisal edge from the lingual and facial aspects.
    139. 139.
    140. 140.
    141. 141. • Use a razor knife to cut back the incisal edge from between 1.0to1.5mm
    142. 142. • Remove dentin porcelain at the mesial inter proximal line angle.extend the cut to the junction of the middle and gingival 1/3rd for younger patients.
    143. 143. • At the distal intrproximal line angle,make a cut form the incisal edge towards the gingival 1/3rd as far as required for the esthetics.
    144. 144. • Examine the restoration from an incisal view for symmetry and adequacy of the cut back.
    146. 146. • With pointed brush,apply enamel porcelain to one corner of cutback.
    147. 147. • Add more enamel porcelain and move it across the facial surface in the incisal one third.
    148. 148. • Blend the enamel porcelain at the junction of middle and gingival 1/3rd &begin to establish the incisal edge & condense the porcelain by blotting periodically.
    149. 149. • Blend the enamel porcelain into gingival 1/3rd on the facial surface.Recreate the interproximal contours and line angles.
    150. 150. • Shape the mesial- incisal corner as required for each case.examine the build up form incisal view&evaluate the overall shape .
    152. 152. • Apply the opaque to mask the underlying metal.
    153. 153. • Complete & smooth the dentin buildup.
    154. 154. • Create three developmental lobes with the pointed brush.
    155. 155. • Invert the cast & place translucent porcelain in the two developmental groove.apply enamel porcelain to the inter proximal areas.
    156. 156. • Continue this process until the entire crown is built to full contour.
    157. 157. • Finally, use the whipping brush to gently smooth the entire porcelain build up.
    158. 158. • Once the porcelain has been fired,you should be able to observe demonstrable mamelons in the restoration.
    160. 160. • Apply and condense opaque porcelain.Cover any gray areas,and fire the prosthesis.
    161. 161. • Return the opaqued FPD to the master cast with a piece of tissue paper cut to cover the entire pontic area.
    162. 162. • Add a small portion of dentin porcelain to the under side of the pontic on the FPD frame work.
    163. 163. • Return the frame work to the master cast and gently rock it back and forth until it seats completely.Remove the frame work and inspect the tissue side of the pontic.this area should cover completely with porcelain and well condensed.
    164. 164. • Place the frame work back on the master cast and apply dentin porcelain or add and condense opacous dentin to the cervical areas of the three components.
    165. 165. • Complete the dentin build up.
    166. 166. • Create the developmental lobes.Use thin razor knife to cut through inter proximal areas and individualize the teeth.
    167. 167. • Add enamel veneering material.
    168. 168. • Condense the porcelain build up.
    169. 169. • Measure the mesial- distal width of each tooth with a Boley that measurement with porcelain build up.
    170. 170. • Use a knife or other instrument to make any necessary adjustments in the mesial-distal width.
    171. 171. • Facial view of the build up.
    172. 172. • Lingual view of the build up.
    173. 173. • Three unit FPD after firing.
    174. 174. FIRING PROCEDURES. • The large bulk of the build up will require more time to dry and pre heat than the opaque porcelain. • Put the restoration on saggar tray place it on the muffle stand of the furnace. • Properly matured porcelain have a slightly orange peel appearance when fired correctly. • Do not under fire the porcelain.porcelain that has not matured properly has no shine to the surface & internally has cloudy appearance.
    175. 175. • Restorations that are under fired porcelain often have to be stripped form metal and rebuilt. • Over fired porcelains appears to be glazed and the surface has little or none of the pebbly appearance. • The firing temperature is usually lowered 10 degrees with each correction firing, so that initial build up does not get affected.
    176. 176. Thank you For more details please visit