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


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

  1. 1. METAL FREE CERAMICS INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2. Introduction : Ceramics in dentistry is a recent phenomenon, the desire for a durable and esthetic material is ancient. Although metals have many characteristics that make them useful in dentistry they do not look like natural teeth. In contrast a superb esthetic and biocompatible result can be achieved with ALL CERAMICS’s. Ceramic is the most natural appearing prosthetic restorative material for missing tooth substance.
  3. 3. Dental porcelain play an important role in the fabrication of the most esthetic fixed partial dentures. Translucency, light transmission, and biocompatibility give dental ceramics highly desirable esthetic properties. However, the brittle nature of dental porcelains, which are basically noncrystalline glasses composed of structural units of silicon and oxygen (SiO tetrahedra) limit the use of this material. 4
  4. 4. Selection :  The primary advantage of using metal free ceramic system is to increase the depth of translucency and light transmission in the crown either deep into the crown or across the entire crown.  Esthetic results vary from system to system, and in a laboratory setting several factors influence the choice one crown system over another….
  5. 5. Factors influence the selection of crown system : Strength.  Simplicity of fabrication.  Potential for high volume production.  Marginal and internal fit.  Cost-benefit analysis.  Personal experience.  Esthetic performance. 
  6. 6. Indications : The fracture resistance of all-ceramic crown is based on adequate support by the preparation, proper patient selection, strength of crown material and type of luting cement. Indications include…. ♣ All anterior teeth where esthetics is of prime factor.
  7. 7. Conservation of tooth structure and maintenance of periodontal health. ♣ Lower incisors where space is available. ♣ Limited use on the premolar teeth where the occlusion allows some protection of the buccal shearing cusps. ♣
  8. 8. Contra-indications:     In the cases of parafunctional activity of the mandible,e.g. bruxism. Or any deflective malocclusions remain uncorrected. Where occlusal clearance after after tooth preparation is less than 0.8 mm, e.g. very thin teeth, deep incisal over jets with lingual wear facets. Insufficient tooth support or where the preparation design causes sudden changes of thickness in the porcelain. Molar teeth.
  9. 9. Aluminous Porcelain Vs Metal Ceramics
  10. 10. Aluminous porcelain : Advantages : 1. Good esthetics is easily obtained if the core porcelain is placed correctly. 2. Full lingual core porcelains protect the crown against opposing incisors. 3. The resistance to pyroplastic flow or slump of the core porcelain can produce better fits than regular porcelains. 4. Greater depth of translucency obtained.
  11. 11. Aluminous Porcelain : Disadvantages : 1. Cannot be used in posterior regions. 2. Parafunctional movements. 3. Long span bridges. 4. Tooth preparation is even more.
  12. 12. Metal Ceramics : Advantages : 1. Very high strength due to prevention of crack propagation. 2. Improved fit. 3. Long span bridges. 4. Availability. 5. Economical.
  13. 13. Disadvantages :       Increased opacity and light reflectivity. Risk of over contouring – metal .5 mm and the rest is ceramic material. Metal margin exposure. The fit of long span bridges may be affected by the creep of the metal during successive bakes of porcelain. Difficult to obtain good esthetics. Porcelains used in the metal-ceramic technique are more liable to devitrify which can produce cloudiness.
  14. 14. Constituents of Dental Porcelain : Silicon dioxide – SiO2 – Glass forming matrix, glass formers. Boric oxide –B2O3 – (Glass modifiers /Flux) Lowers the softening point, lower viscosity, higher expansion. Oxides of potassium, Sodium, calcium, lithium, magnesium (Glass modifiers). Aluminum oxide – Al2O3 – (intermediate oxides) reduces viscosity, lowers firing temperature. Phosphorus pentoxide – P2O5 – opalescence, glass forming oxide.
  15. 15. Properties of Dental Porcelain : Low fusing temperature.  High viscosity.  Resistance to devitrification.  Translucent. 
  16. 16. Strength of All Ceramic Crowns : The objective of fabricating all ceramic crown is to provide the patient with lasting esthetic restorations. New materials are been advocated as replacement for metal ceramic restoration. The strength of ceramic is greatly influenced by the presence of surface flaws acting as stress initiators and causing widening and propagation of microcracks through the material from the surface. Therefore dental porcelain is much weaker in tension than in compression and is prone to brittle fracture.
  17. 17. Dental porcelain is also susceptible to “static Fatigue”which is generally caused by a stress dependent chemical reaction between water vapor and the surface flaws in the restoration. This causes flaws to grow to critical dimensions, allowing spontaneous crack propagation, resulting in a fracture with comparatively little occlusal loading, particularly over long periods.
  18. 18. Surface Flaws : A high strength ceramic with a badly flawed surface may perform worse in a clinical situation than a weaker ceramic with comparatively flaw-free surface. The fracture pattern of cast glass ceramic, aluminous porcelains is always initiated at the surfaces and usually at the locations involving porosities. Kelley et al classified porcelain defects into Processing defects – Machining scratches, porosities, and impurity inclusions. Inherent material defects – large grains, residual stresses and microcracks.
  19. 19. Core Thickness : The rigidity and thickness of the ceramic core play an essential role in the flexural strength of the whole restoration.sections less than 1mm should be avoided, and ideally dentist should aim for cross sections of 1.5 mm. The ideal aluminous porcelain coping for incisors should exhibit: * a lingual surface atleast 1 mm thick: *a lingual collar extended proximally, similar to a metal coping: *the incisal labial area thinned to 0.3 mm for esthetics.
  20. 20. Strengthening Mechanisms : Crack-tip interactions : Dispersion strengthening with Alumina, Leucite, Zirconia and Magnesium aluminum oxide spinell crystals. Obstacles in the microstructure impede crack propagation by reorienting and deflecting the plane of fracture.
  21. 21. Crack-tip Shielding : Events triggered by the high stresses in the crack tip region act to reduce the stresses. Dispersion strengthening by Glass Infusion of slip cast alumina ceramics, (Micro-crack toughening). Dispersion strengthening of PSZ ceramics, (Transformation toughening).
  22. 22. Crack Bridging : The second phase crystalline structure acts as a “bandage”to prevent crack from opening further.Crystallization of Glasses by Ceramming.
  23. 23. Crystalline dispersion Strengthening : Strengthening method Clinical system Fused Alumina sintered into a Hi – Ceram matched expansion (Vident) glass. Characteristics Alumina reinforced ceramics Leucite crystals dispersed through the body of the crown Optec(Jeneric/Pent Leucite reinforced ron) IPS Empress Heat pressed (ivoclar) leucite-reinforced Crystallized magnesiun aluminum oxede spinell Al-Ceram (Innotek Dental Corp.) formerly Cerestore. Shrik-free alumina ceramic.
  24. 24. Glass infiltration strengthening : Reinforcing crystals Clinical System Charestrestics Alumina In-Ceram Alumina (Vita) High alumina coping infused with a low fusing glass Zirconia In-Ceram Zirconia (Vita) High Zirconia coping infused with a low fusing glass Magnesium oxide spinell In-Ceram Spinell (Vita) High Spinell coping infused with a low fusing glass
  25. 25. Crystallization of Glasses : Strengthening method Clinical system Characteristics Conversion by “Ceramming” Dicor (Dentsply) Castable glass ceramic with tetrasilic fluormica crystals Conversion by Cerapearl “Crystallization” (Kyocera america Inc.) Castable apatite ceramic
  26. 26. Classification of Dental Porcelain A L L -C E R A M IC S R e i n fo rc i n g M a te ri a l G e n a ra l S y s te m F i r i n g T e m p e ra tu re A lu m in a M a g n e s iu n s p in e l P o w d e r s l u rry C a s ta b l e H ih g F u s in g Z ir c o n iu m L e u c it e P re s s a b l e In fi l t ra te d L o w F u s in g Z i r c o n i a W h i s k e rs H ig h A lu m in a M a c h in a b le M e d iu m F u s in g Summary
  27. 27. Firing Temperature : High Fusing : 1290`C – 1370`C These are used for the manufacture of porcelain teeth. Composed of Feldspar=70%-90%, Quart= 11%-18%, Kaolin= 1%-10%.
  28. 28. Low / Medium Fusing Porcelains Low and medium fusing porcelains are manufactured by a process called Fritting.
  29. 29. General Classification 1. Conventional powder ceramics 2. Castable ceramics 3. Pressable ceramics 4. Infiltrated ceramics 5. Machinable ceramics
  30. 30. Castable Ceramics : These products are supplied as solid ceramic ingots, which are used for fabrication of cores or full contour restorations using a lost wax and centrifugal casting technique. Generally, one shade of material is available. Which is covered by conventional feldspathic porcelain or is stained to obtain proper shading and characterization of the final restoration. e.g. DICOR (Corning glass, Dentsply). CERAPEARL (Bioceram, Kyocera)
  31. 31. Powder Slurry Ceramics : These products are supplied as powders to which the technician adds distilled water to produce a slurry, which is build up in layers on a die material to form the contours of the restoration. The powders are available in different shades and translucencies, and are supplied with characterizing stains and glazes. e.g. OPTEC H.S.P (Jeneric/Pentron) DUCERAM L.F.C (Ducera Inc) Vita Hi-Ceram (Vita Zahnfabrik)
  32. 32. Pressable Ceramics : These are also supplied as ingots, these product are melted at higher temperatures and pressed into a mould using a lost wax technique. These pressed form can be made into full contour, or can be used as a substrate for conventional feldspathic porcelain buildup, or can be built up by layering technique. e.g. IPS Empress I, II (Ivoclar vivadent) OPC (Optec Pressable Ceramic) ALCERAM (Cerestore, Innotek dental corp)
  33. 33. Infiltrated Ceramics : These are glass infiltrated core ceramics. This involves slipcasting technique for making the core, and the contours of the restoration are obtained by individual layering and staining techniques. e.g. In-CERAM (Vita Zahnfabrik) Alumina Zirconia Spinell
  34. 34. Machinable Ceramics These products are supplied as ingots in various shades and are milled into desired form. These machined restorations can be stained and glazed to obtain desired characterization. They are of two types : CAD-CAM = Computer Aided Designing – Computer Aided Milling. e.g. CEREC (Sirona) Ivoclar ProCAD (Ivoclar, Spring) Dicor M.G.C (Dentsply) Copy Milling = CELAY (Mikrona Technologies)
  35. 35. Preparations for All-Ceramic Crowns : The role of the tooth preparation for a porcelain jacket crown is to provide support for the prosthesis with uniform porcelain thickness. It was recognized that the most frequent cause of JC failure was improper tooth preparation.
  36. 36. The Design : The design of an ideal all-ceramic crown preparation is to provide maximum strength of the crown by establishing flat planes at right angles to the forces of mastication and avoiding sharp line angles. A shoulder margin is also required because it offers superior strength as compared to chamfer.
  37. 37. Length of the preparation : When a load is applied from a lingual direction, the labial shoulder is placed under compression and only the length of the preparation at the incisal lingual aspect provides significant resistance to this force.short preparations cause considerable stresses and may lead to fracture.
  38. 38. Length of the preparation : The ideal incisal reduction 2 mm and must not exceed more than 1/3rd of the anatomical crown . If the incisal reduction is too thin, it should be thickened and placed at a right angle to the direction of stress by reducing the preparation to a length of 2/3rd of the anatomical crown.
  39. 39. Shoulder : A well defined shoulder with adequate width improves the fracture resistance of the crown because it provides additional bulk at the margins that is placed at right angles to the direction of stresses The more the intimate the contact between the preparation and the ceramic crown higher the resistance to fracture on occlusal
  40. 40. Shoulder / Chamfer : When the shoulder angle of the preparation to the longitudinal axis of the tooth is greater than 90`, the risk if porcelain fracture increases. The internal shoulder angle should be rounded to reduce the stress concentration factor up to 50% and because sharp internal line angles cannot be easily reproduced with porcelain. Similarly , the internal rounded shoulder is recommended for the In-Ceram* crown to facilitate the adaptation of the aluminous oxide slip on the die.
  41. 41. Shoulder / Chamfer : A chamfer is conservative and simpler to execute and has been described as an option for cast glass ceramic restorations.
  42. 42. Shoulder width : A shoulder of uniform thickness may round the preparation excessively and compromise resistance form. For a maxillary central incisor, the lingual and facial shoulder width should be I mm with a minimum of 0.8 mm, and the interproximal width should be 0.5 mm because the proximal walls of the crown flare out and provide sufficient strength in the proximal area
  43. 43. Shoulder width : These specifications for a shoulder of non uniform width provide for conservatism, support, and resistance of the preparation to stresses.
  44. 44. Shoulder curvature (interproximally) : The finish lines should follow a smooth curvature that it is not too steep inter-proximally to avoid a potential v shaped notch that could split the labial off the lingual aspect of the crown.
  45. 45. Facial & Lingual reduction : The minimal acceptable facial thickness of porcelain from an esthetic standpoint is 1.0mm, and the ideal depth of reduction on the midfacial aspect of a typical maxillary central incisor for an aluminous porcelain jacket crown should be 1.3 mm. Facial depths of reduction up to 1.5mm have also been recommended for molded, castable, and slip-cast ceramics. Lingual thickness values of 1.5 mm are ideal but are difficult to achieve routinely.
  46. 46. Facial & Lingual reduction : Practically lingual thickness should be in the 1 – 1.3 mm range, and the absolute minimum should be 0.8 mm. The lingual aspect of the preparation should be shaped to avoid uneven sections of the crowns and sharp line angles must be avoided.
  47. 47. Taper : Minimal taper is recommended for maximum surface area and support of the preparation. Excessive taper of the preparation correlates with a reduction in breaking strength and increase in stress concentration in the area where support is lacking. A 5`taper is ideal and would ensure maximum resistance form with only one path of insertion of the crown but it is also difficult to achieve without producing undercuts. The safest and most practical convergence angle of all-ceramic preparations is 10`taper, which represents an acceptable compromise between taper and strength.
  48. 48. Taper : Excessive porcelain bulk has an adverse effect on strength. It is not the bulk that gives the strength to the crown, it is the resistance to flexure provided by the support from the preparation and the accuracy of the fit.
  50. 50. DICOR The castable glass ceramic system History Material Advantages & Disadvantages Indications & Contraindications Clinical procedures Laboratory procedures 
  51. 51. History : The DICOR castable glass ceramic is one of the pyoceram ceramics manufactured by Corning glass ware.  Founded in the year 1978, after 6 years of intensive research this ceramic system was introduced to dentistry.  The present system represents the cumulative efforts of Peter.J.Adair of BIOCOR Inc., David Grossman Ph.D of the Corning Glass ware & Dentsply International. 
  52. 52. Composition  Consists of three crystalline forms, SiO2, = 45% -70% (w/w) K2O, = 20% (w/w) MgO, = 3% - 13% (w/w) MgF2 = 4% - 9% (w/w)(Fluoride as a nucleating agent forming nucleation sites to aid the crystal growth during the process of ceramming, ;eading to a growth of approx 1 micron small tetrasilicic crystals). Small amounts of AlO3, ZrO2,BaO Fluorescing agents.
  53. 53. Material :    Technically described as Tetrasilicic fluoromica glass ceramic. Tetrasilicic fluoromica crystals 55% vol Glass 45% vol These miniscule crystals lie interlaced within the glass phase in the direction of the casting. On the surface of the cerammed glass are Enstatite crystals of thickness microns. These occur through fluorine depletion which occurs through the interaction with the embedment material needed for the ceramming process. These crystals are in orthogonal in direction to the surface and are whitish and opaque.
  54. 54. Advantages :  Strength - Feldspathic porcelains and some all porcelains, are glasses, and they are subject to the inherent frailties of glass (super cooled liquids).  The tetrasilicic mica crystals(K2Mg5Si8O20F4) are similar to mica.  These crystals stop the propagation Griffith flaws. 
  55. 55. Marginal adaptation : Dicor casting are statistically more consistent in terms of “fit”than were the gold crowns.  The thermal expansion of coefficient of cast glass ceramic is close to that of natural enamel. This means expansion and contraction during normal temperature fluctuations, thus maintaining a good marginal seal. 
  56. 56. Biocompatibility :  Lesser plaque accumulation. good marginal fit.  Fluoride content inhibits bacterial colonization.  The surface of the restoration is smooth and non porous. 
  57. 57. Wear Potential : This system has a microhardness closely matched to enamel, while the microhardness of feldspathic porcelains is one third greater.  Cast Ceramic (KHN) = 362.  Enamel (KHN) = 343.  contd….
  58. 58. Wear potential…..  The surface can be polished to a very smooth non porous finish smoother than glazed feldspathic porcelain.  Lingual contours that represent a physiologic anterior guidance are also a crucial factor in minimizing wear.
  59. 59. Thermal conductivity :  Low thermal conductivity that insulates the underlying tooth from temperature changes. Simplicity
  60. 60. Esthetics : There is a close match in translucency between the cast ceramic material and enamel.  The numerous, small mica crystals that constitute the structure of the castable ceramic are loosely matched in the index of refraction to the surrounding glass phase that bonds the material. Thus the intensity of light scattering at each glass crystal interface is less, that is more suitable. Increase in crystalinity ensures more scattering.  Veneering porcelains also can be used to modify translucency and better color depth.  This material is capable of producing chameleon effect, where part of the color of the restoration is picked up from the adjacent teeth as well as the 
  61. 61. Disadvantages :  Special equipment and cost.  Moderate strength.  No fixed partial denture application.  High failure rate in posterior regions of the mouth, as well as recent developments of other materials, led to the phasing of this product.
  62. 62. Indications :  Anterior PJC.  Inlays, onlays, three quarter crowns.  Partial veneers, especially in periodontally compromised teeth
  63. 63. Contraindications :  Clinical crown length is short.  FPD.
  64. 64. Clinical Procedure :  The tooth structure is sufficiently removed to allow an adequate thickness of the material for strength and color saturation.  For castable ceramics, the tooth reduction on all surfaces must be no less than 1.2mm.  Heavy chamfer (135`)`or shoulder margin.  6`- 8`taper and all line angles rounded.  Standard impression procedures are followed.
  65. 65. Tooth preparation :  Incisal or occlusal - 1.5 mm- 2.0 mm.  Facial or lingual - 1.0 mm – 1.5 mm.
  66. 66. Laboratory Procedures : Die preparation.  Waxing & Spruing.  Investing & Mold conditioning.  Casting.  Divesting.  Sprue removal.  Embedding.  Ceramming & post ceram divesting.  Finishing, coloring. 
  67. 67. Die Preparation : Casts shoulb free of 0cclusal artifacts,air bubbles and other inaccuracies. Dies must be prepared with proper indexing. The dies should be sectioned, trimmed and refined with care. Any existing undercuts must bu blocked out to ensure wax pattern removal without distortion. Die sealant should be used. A die spacer of appropriate shade is applied on evenly to the die to within 1 mm of margin.
  68. 68. Prepared Die :
  69. 69. Waxing :     Die lubricant is applied over the die spacer to prevent adherence of the wax to the die. All contours of the wax crown should have a minimum thickness of at least 1mm to ensure adequate strength of the crown. A smooth and completely formed internal surface of the waxed crown is necessary. A wild-Leitz stereomicroscope with fibre optic light can be used to avoid any over extensions in the margins.
  70. 70. Wax Pattern :
  71. 71. Spruing :     One 8 or 10 gauge wax sprue, attached to the incisal surface of the anterior patterns, provides an adequate gate for the ingress of the ceramic material. Posterior patterns are usually require 10 gauge sprues attached to the lingual and buccal cusp tips. Sprue placement on molar patterns should be diagonally opposed for more uniform flow of the fluid ceramic. A sprue design incorporating a perpendicular reservoir has also produced adequate casting.
  72. 72. Spruing : Length must be approx 3 – 4 mm.  The pattern should be located so that its most distal point is approx 6 – 7 mm from the open end of the casting ring to allow adequate diffusion of the mold glass through the investment. 
  73. 73. Spruing :
  74. 74. Investment :      Wax pattern must be cleansed with a debublizing agent, any excess must be removed. Non-corroding casting rings that are resistant to oxidation at high temperature must be used. 2 layers of Kaoliner* a ring liner material (an asbestos liner)is placed inside the ring,to permit suffficient expansion. The ring liner is saturated eith water for about 10 sec before ceating the ring on to the crucible former. A special phosphate bonded investment is used
  75. 75. Castable ceramic investment* :
  76. 76. Investment :     This material exhibits no setting expansion but produces approx 1.5% thermal expansion at high temperatures. 8 ml of distilled water must be mixed with 60 gm of investment powder for 30 sec under vacuum with power spatulation. After spatulation additional vibration under vacuum is carried for 20 – 30 sec. The mixed investment should be carefully applied on to the wax pattern with a camel’s hair brush.
  77. 77. Investment : After the wax pettern is carefully filled and coated, the remaining material should be vibrated into the ring allowing an excess to remain above the open ends of the ring.  After bench setting for 1 hr the excess material should be trimmed even with the top of the casting flask. 
  78. 78. Investment :
  79. 79. Mold conditioning :    A two stage mold conditioning is employed. The invested pattern is placed in a cold furnace, the temperature is raised to 249`C, and maintained for 30 min (heat soak), 10 min of additional time for each ring should be added if more than three rings are placed at a time. The temperature is raised to 899`C, and maintained for 2 hrs (heat soak), similarly 10 min added for each ring.
  80. 80. Casting : A 4 gm ceramic ingot is loaded in the ceramic crucible. The amount of ceramic material required to make a good casting can be determined when multiplied by a conversion factor of 2.6, the weight of the wax pattern, sprues and button should not exceed 4gm . Two patterns can be cast into one flask.
  81. 81. Ceramic ingot; Ceramic crucible:
  82. 82. Casting Machine : The Dentsply DICOR casting machine features a platinum electric resistance-type muffle mounted on a electrically driven straight centrifugal casting arm.  The machine is fitted with a special receptacle to hold the Dicor crucible. 
  83. 83. Dentsply DICOR Casting Machine :
  84. 84. Dentsply DICOR Casting Machine :
  85. 85. Casting Procedure :      An ideal temperature of 1100`C is maintained for 10 min to stabilize the muffle. The crucible containing the ceramic ingot is inserted through the rear muffle door. The crucible is properly positioned in the muffle for melting the glass by the help if a special tool. The rear door is closed, the melting temperature is adjusted to 1360`C, and the melt switch is turned on. After reaching the determined temperature, this will be maintained for 6 min.
  86. 86. Casting Procedure :     The rear muffle door is opened . The casting ring is removed from the burnout furnace and placed in the cradle with the crucible and gate facing the muffle. The front muffle door is opened and the muffle assembly is slid forward towards the casting ring until it is seated. The casting machine cover is shut and the casting switch is turned on. The casting arm spins automatically for 4 ½ min and then stops. By the end of the spin cycle the casting will cool down
  87. 87. Casting Procedure :  The casting ring is removed form the machine and allowed to dool for 45 min before divesting. Divesting : •After cooling, the investment is removed from arround the edges of the casting ring to a depth of approx 6 –8 mm. The investment mass can be forced out of the retaining ring by pushing with the fingers.
  88. 88. Divesting :    The bulk of the investment material can be broken away from the casting with finger pressure. The remaining casting should be removed with an air abrasive tool using 25 micron aluminum oxide at 40 p.s.I. The margin areas should be protected by covering with the finger to prevent chipping.
  89. 89. Sprue removal : The cast crown is cut off at the junction of sprue and button using a suitable single or double side diamond disc.  The sprue is cut near the glass button to avoid chipping.  The remaining button must be dicsarde and cannot be reused because the glass is altered during melting cycle.  The casting at this stage is non-crystalline. 
  90. 90. Casting :
  91. 91. Embedding :     The casting is embedded in the ceramic embedment material, so that the ceramming process can take place. During this ceramming procedure the glass is concerted into a 55% crystalline form. The glass casting is embedded in a mixture of 18 ml distilled water and 50gm of embedment powder. Hand mixing is sufficient. The inside of the crown is carefully filled with the embedment mix and then it is placed on a tray with a concave receptacle in which additional material is placed.
  92. 92. Embedding :  Additional embedment is used to cover and protect the glass crown. The material should be allowed to set for 45 – 60 min.
  93. 93. Ceramming :    This process is accomplished by a precisely controlled ceramming furnace. The furnace temperature is gradually increased to 1075`C for 3 ½ hrs, this temperature should be maintained for 6 hrs. the furnace is cooled to 200`C and the embedment tray is removed. The ceramming process involves a two-stage heat treatment. The first heat treatment is carried at the temperature for maximum nucleation of crystals, so maximum no: of crystals are formed. The temperature is held for some time for the crystal growth to take place, to attain the maximum size.
  94. 94. DICOR Ceramming Furnace :
  95. 95. Ceramming tray :
  96. 96. DICOR Ceramming Furnace :
  97. 97. Ceramming   The proper ceram cycle is verified by the use of a pyrometric cone. The characteristic droop will provide verification that proper time and temperature has allowed the development of the desired crystalline properties in the casting.
  98. 98. Ceramming verification :
  99. 99. Postceram divesting : The tray is allowed to cool to room temperature.  The embedment is broken.  The crown is cleaned by air-blasting with 25 micron aluminum oxide at 40 p.s.I at a distance of approx 6inches.  The margins should be protected from chipping during air-blasting. 
  100. 100. Wax pattern – Glass form - crystalline form - finished crown
  101. 101. Crown finishing :    Crystalline glass crown is inspected for internal nodules or irregularities, which may interfere with seating of the casting on the die. These irregularities csn be removed with extrafine diamond points. The crows is seated on to the die and examined for marginal overextensions. If any, must be removed with fine white point or rubber wheel rotating at low speed. The remaining sprue is removed with a double sided diamond disc rotating at slow speed.
  102. 102. Crown finishing :     The fine opaque white skin covering the crown must be removed. The sprue is finished and the skin is lightly removed with a fine rubber abrasive wheel. After removal of the skin the crown is air blasted with 25 microns aluminum oxide at 40 psi. The primary and secondary occlusal anatomy can be defined with small round and inverted cone T.C burs. Corrections can be done with an add-on material. The casting is dried in front of the open muffle at 593`C and introduced into muffle under vacuum to a temperaturewww.indiandentalacademy.commin and can be of 968`C for 1 shaped and adjusted to desired contours.
  103. 103. Characterization & Glazing :     After the ceramming process the casring is achromatic, the desired hue is decided by the shading porcelains. The blending of enamel and body colors must occur while they are wet. The first and the second shading porcelains should be fired at a slightly lower temperature to prevent over glazing and glassy appearance of the crown. Castable ceramics can be fired repeatedly in a conventional glazing oven without affecting the physical properties or marginal integrity of the material
  104. 104. Characterization & Glazing :
  105. 105. Unglazed & Glazed crowns :
  106. 106. Completed crown :
  107. 107. Cementation :    The color value is modified by a series od dentsply shaded cements.these cements are color coordinated with the die spacers that are earlier used. If a natural colored tooth preparation exists, a translucent glass ionomer cement is indicated. In those cases the tooth structure or a metal core is present, the use of properly colored cement can be of good esthetic value. During cementation process, controlled, positive finger pressure should be used to seat the crown onto the prepared tooth. Excess cement is completely removed after the setting is complete.
  108. 108. Dicor shaded cements :
  109. 109. CERAPEARL : Introduction  Composition  Properties  Lab technique 
  110. 110. Introduction : Bioceram group have developed castable ceramic material (Hobo & Kyocera) which may be classified as CaO.P O .MgO.SiO glass ceramic.  Its crystalline structure is similar to that of enamel.  Biocompatible and is indicated for crowns and inlays.  2 5 2
  111. 111. Composition : It is composed of CaO.P O .MgO.SiO plus traces of other elements.  CaO.P O - are the main ingredients and aid in glass formation. Essential to form hydroxyapatite crystals.  Mg O. CaO – decrease the viscosity.  SiO in combination with P O – form the matrix.  2 2 2 5 2 5 2 5
  112. 112. Properties : Melts at 1460`C and can be cast. The casting has an amorphous microstructure and when it is reheated at 870`C for 1 hr, it forms crystalline oxyapatite. This apatite is clinically unstable and when exposed to moisture becomes crystalline hydrooxyapatite.  It has similar crystalline arrangement as enamel but the crystals are irregular providing superior mechanical strength. 
  113. 113. Lab Technique :      Casts are poured in type IV dental stone. After the die sealant,spacer and separator is applied, the wax up is done and sprue is attached. Invested in phosphate bonded investment in a silicone mold. After seraration of the silicone mold 60 min later, it is dried in an oven at temperature less than 100`C for 30 min. Then the temperature is raised to 500`C and then to 800`C for 30 min.
  114. 114. Lab Technique :     The investment mold is transferred to a high heat processor specially developed for this system. 8 – 10 gm of new Cerapearl is placed in the ceramic crucible and melted under vacuum at 1400`C and cast into a mold. Upon completion of casting the ring is transferred to crystallization mold. The process by which the casting is re-heated under appropriate conditions to develop the micro-crystals of apatite is termed crystallization. It makes the casting highly dense, strong, hard and chemically stable.
  115. 115. Lab Technique : The crystalization starts at 750`C then maintained for 15 min =, then reached at 870`C for 1 hr.  Translucency is similar to enamel.  External stains can also be given after cooling. 
  116. 116. Conventional POWDER SLURRY CERAMICS Vita Hi-Ceram* Optec HSP* Duceram LFC* Summary
  117. 117. VITA Hi-Ceram : Material properties  Laboratory procedures. 
  118. 118. Material : This is a aluminum oxide reinforced hard core porcelain.  Alumina reinforced core consists of 50% of aluminous crystals in a matrix of low fusing glass of matching thermal expansion.  Aluminous core porcelains are twice stronger than regular porcelains. 
  119. 119. A comparision of the bending strengths of vita Hi-Ceram and Vitadur-N core porcelains
  120. 120. Merits : Highly accurate margins.  Higher melting points and greater stability.  For both anterior and posterior crowns, veneers. 
  121. 121. Clinical Procedures : Heavy chamfer or shoulder with internal angles rounded.  Regular impression procedures. 
  122. 122. Lab Procedures : Preparing the refractory die.  Hard core porcelain framework.  Crown buildup. 
  123. 123. Refractory Die :  Prepared die on the master model.
  124. 124.  To create the necessary space for the cement, apply Vita interspace varnish on to the die in 2 or 3 coatings.
  125. 125.  Apply a coat of thin insulating grease onto the duplicating base and ring, fix the die into the duplicating base and then place the ring into position.
  126. 126.  The hi-ceram duplicating paste consists of paste, liquid and catalyst, should be stirred quickly to obtain a homogenous mix. NOTE : first mix the paste and liquid together and then stir in the catalyst.
  127. 127.  To avoid any creating bubbles, fill the mold by pouring in the mixture in a fine stream. Working time approx 2 ½ min. Setting time – 20 – 30 min.
  128. 128.  Remove the die from the solidified cast of duplicating paste, and clean off the interspace varnish using the interspace varnish thinner.
  129. 129.  Mix the refractory HiCeram die material together with the die material liquid: for this, the liquid should be drawn into the dosing syringe to the 3 ml mark, for one 15 gm sachet of powder. *Stir the two materials for at least 1 min.
  130. 130.  On a vibrator without any bubbles fill the mold that is to be duplicated. While it is still soft, set a porcelain retaining pin into the die material, so as to later be able to safely fix the die onto a porcelain firing tray.
  131. 131.  The setting time for Hi-Ceram die material varies between 1 ½ - 2 hrs, depending on the room temperature. After no more than 6 hrs the die is removed from the mold.
  132. 132.  The die should be set on a porcelain tray for the refractory material to harden. Pre dry the die in the VITA Vacumat 200 /100 : with the furnace on standby(or prog A), lower the firing tray by manual control key and the place the die onto it. Only when the die material has turned light green the following prog is initiated ……….
  133. 133.  In the Vita Vacumat 200 : prog 5.5, end temp 1,000`C, pre-drying time 10 min, heating time 10 min, hold time 3 min. In the Vita Vacumat 100 : prog 5, end temp 1000`C, predrying time 10 min, heating time 10 min, hold time 3 min.
  134. 134. Constructing the hard core porcelain
  135. 135.  The Hi-Ceram hard core porcelain has to be applied and fired in three layers altogether : 1. The wash firing.; 2. Half of the required thickness with protuberances for later checking on the thickness of the porcelain.; 3. Full build-up as a smaller version of the crown it is to become. Minimum thickness0.5mm.
  136. 136.  Prior to each new application of Hi-Ceram hard core porcelain, the die should first be allowed to cool and then left to soak in water until no more bubbles are being emitted.
  137. 137.  Excess water should be soaked up. Next, Hi-Ceram hard core porcelain powder is mixed together with Vita modeling liquid “P” to a thin, creamy consistency. This is then applied as a thin wash onto the die.
  138. 138.  Pre dry the die on the lowered firing tray of the furnace until it has again turned light green, and then fire as follows, using a standby temperature of 600`C :
  139. 139. In the Vita vacumat 200: programme 6.6, end temperature 1170`C, pre-drying time 6 min, heating time 10 min, hold time 0 min, vacuum firing time 10 min.  In the Vita vacumat 100: programme 6, end temperature 1170`C, predrying time 6 min, heating time 10 min, hold time 0 min, vacuum firing time 10 min. 
  140. 140.  Soak the die in water again, and then apply the hard core porcelain for second firing. To make sure of having the correct thickness of HiCeram hard core porcelain, protuberances or points can be constructed for control purposes. The firing instructions are the same as for the 1st hard core porcelain firing.
  141. 141.  The fully built up hard core porcelain in its final form before the third firing. For this, fire fire as follows, using a standby temperature of 600`C
  142. 142. In the Vita vacumat 200: Programme 6.7, end temperature 1170`C, predrying tome 6 min, heating up tome 6 min, hold time 3 min, vacuum firing time 10 min.  In the Vita vacumat 100: Programme 6, end temperature 1170`C, predrying time 6min, heating up tome 10 min, hold time 3 min, vacuum firing time 10 min. 
  143. 143. The thickness of hard core porcelain framework should not be less than 0.5 mm.  For additional stability, a collar in HiCeram hard core porcelain can be added palatally or lingually. 
  144. 144.  Just as with Vita VMK metal-ceramic porcelain, Hi-Ceram hard core porcelains can also be shaded individually using the Hi-Ceram COLOR hard-core porcelains, e.g. ti reinforce the shade from within in cases where the thickness of the dentin porcelain is thinner than normal.
  145. 145.  The refractory die should be blasted away using glass beads at a pressure of 1- 2 bar.
  146. 146.  The finished HiCeram hard core frame work on the stone die. Any areas of interface or feathered edges should be carefully ground down or removed using a fine-grained diamond.
  147. 147.  As the Hi-Ceram hard core framework has not been constructed on the model, any areas that are now found to have been built up too high or too thick can be corrected using a fie grained diamond.
  148. 148. The build up of the crown :
  149. 149.  The crown should be built up to its desired shape using Vitadur-N dentin porcelain, although to compensate firing shrinkage it must be built longer incisally. The cervix of the hard core framework can be coated before hand using Vitadur-N opacous porcelain.
  150. 150.  A little Vitadur-N opacous dentin can also be applied palatally, so that even in cases where there is a deeper than normal bite by the occluding teeth, any shining through of the HiCeram hard core porcelain will be completely avoided.
  151. 151.  To create the necessary space for the enamel porcelain, the dentin should have a crescent carved away incisally and for the smooth transition between the dentin and enamel, then also be smoothened using a flattened brush.
  152. 152.  For individual shading and characterizatio n, there are 5 Vitadur-N opacous dentin, 6 dentin effect, 2 enamel effect and 7 COLOR porcelains available.
  153. 153.  The shape of the crown is now built up in Vitadur-N enamel porcelain. It should be somewhat over dimensioned to compensate firing shrinkage.
  154. 154.  The crown is fired as follows: either by placing it onto a fibrous pad firing support (in which case raise the temperature by 10`C), or by wrapping a normal crown stand in the fibrous pad material and then placing the crown loosely onto it:
  155. 155. In the Vita vacumat 200: Programme 6.4, end temperature 960`C, predrying time 6 min, heating up time 6 min, hold time 1 min, vacuum firing time 6 min.  In the Vita vacumat : Programme 6, end temperature 960`C, predrying time 6 min, heating up time 6 min, hold time 1 min, vacuum firing time 6 min. 
  156. 156.  The fired Hi-Ceram crown should be ground all over in the normal way, using a diamond or a green silicon carbide bur. For corrections, clean without using any cleansing agent but with a clean brush under running water, or a steam jet blaster. Then reapply the appropriate porcelain and fire as for the main vacuum firing, except with the temperature reduced by 10`C.
  157. 157.  Before each firing, it is also possible to improve the accuracy of fit and esthetics of the cervical margin: the stone die should first be insulated using one drop thin bodied super glue. This sealing of the surface will prevent the die from soaking up any moisture from the porcelain. Next, to prevent to prevent the modeled porcelain from sticking to the die, the chamfer should be thinly coated with Hi-Ceram die release before applying the cervical porcelain.
  158. 158.  The cervical porcelain should be mixed with Vita modeling liquid, applied onto the cervical margin, condensed and then bottled. Excess cervical porcelains should then be removed using either a clean finger or a dry brush.
  159. 159.  Without being tilted, the crown should be removed and fired as ……
  160. 160. Cervical porcelain firing in the Vita vacumat 200 programme 6.8, end temperature 940`C, predrying time 6 min, heating up time 6 min, hold time 1 min, vacuum firing time 6 min. Cervical porcelain firing in the Vita vacumat 100 programme 6, end temperature 940`C, predrying time 6 min, heating up time 6 min, hold time 1 min, vacuum firing time 6 min.
  161. 161. Glaze firing :  Applying the Vitachrom ”L” glaze No. 725 allows the temperature for the glaze firing to be lowered, thereby guarantying that the cervical margins retain w its accurate
  162. 162. Glaze firing in the Vita vacumat 200: Programme 5.4, end temperature 920`C, predrying time 4 min, heating up time 3 min, hold time 1 min.  Glaze firing in the Vita vacumat 100: Programme 5, end temperature 920`C, predrying time 4 min, heating up time 3 min, hold time 1 min. 
  163. 163. Finished Vita Hi-ceram crowns
  164. 164. Optec HSP
  165. 165. Introduction: Optec HSP(Jeneric / Pentron) is a Leucitereinforced feldspathic porcelain that is condensed and sintered like aluminous porcelain and traditional porcelain. Has greater strength than traditional feldspathic porcelains due to increased amount of leucite. The manufacturer disperses the leucite crystals in a glassy matrix by controlling their nucleation crystal growth during the initial production of the porcelain powder.
  166. 166.  Because of its increased strength, Optec HSP* does not require a core when used to fabricate all ceramic restorations, as is necessary with aluminous PJC’s. the body and incisal porcelains are pigmented to provide the desired shade and translucency. The leucite and glass components are fused together during the baking process (1020`C). The buildup and contouring of the crown is done on a special semi-permeable die material. It has a moderately opaque core compared with a metal or an aluminous porcelain core, it is more translucent than alumina-core crowns and glass infiltrated alumina core crowns.
  167. 167. Advantages: Lack of metal or opaque substructure.  Good translucency.  Moderate flexural strength.  No special laboratory equipments needed. 
  168. 168. Disadvantages: Potential marginal inaccuracy caused by porcelain sintering shrinkage.  Potential to fracture in posterior teeth. Leucite reinforced porcelain that is condensed and sintered shrinks when fired because of the volumetric decrease caused by sintering, and the fit of the crowns made from this ceramic is not as good as that of PFM crowns with metal margins. 
  169. 169. Duceram LFC:
  170. 170. Introduction:  The development of very low fusing ceramics(fusing temperature 660`C) meant that a simple and accurate technique for building up and firing all-ceramic restorations.
  171. 171. Method of Fabrication: Tooth preparation. Die preparation. Ceramic core. Ceramic buildup.
  172. 172. Tooth preparation: Preparation for a CJC with a peripheral shoulder.
  173. 173. Ceramic coping preparation : Refractory die.  Initial ceramic connector layer.  Ceramic core buildup. 
  174. 174. Ceramic connector: A fine layer of initial ceramic over the refractory die the refractory die (Ducera-lay) is fired at 980`C. This connector layer should be bright and even
  175. 175. Ceramic Core: Lamination in Duceram ceramic directly on the refractory die to produce a ceramic coping of 0.3 mm thickness
  176. 176. Lamination in Duceram ceramic directly on the refractory die to produce a ceramic coping of 0.3 mm thickness
  177. 177. Lamination in Duceram ceramic directly on the refractory die to produce a ceramic coping of 0.3 mm thickness
  178. 178. The coping is fired at 940`C. Various shades can be introduced at this stage.
  179. 179. After firing the coping is gently sandblasted off the refractory material using 50 micron aluminum powder.
  180. 180. Prepared coping
  181. 181. Ceramic Buildup: The coping is replaced on the plaster cast. Lamination can the be completed using a low-fusing ceramic, which will be fired at 660`C in a vacuum.
  182. 182. Completed Duceram-LFC Crown: Facial view ^
  183. 183. Completed Duceram-LFC Crown: Lingual view (Courtesy : Marc Cristou)
  184. 184. Properties: Flexural strength – 110 Mpa.  Hardness is close to that of natural tooth due to absence of leucite.m  Opalescence of the natural tooth can be reproduced.  Fluorescence of LFC is very close to that of natural tooth. 
  185. 185. Fluorescence:  Comparison of fluorescence of natural teeth(green), Duceram LFC(blue),
  186. 186. Fluorescence: LFC (circle left); traditional ceramic material (circle right); natural tooth (middle).
  187. 187. Advantages: Excellent marginal adaptation.  Use of plaster master cast.  No special equipment required.  Allows for modification by repeated firings.  Abrasion rate close to that of natural tooth.  Good visual qualities, including best reproduction of opalescence of natural teeth. 
  188. 188. Indications: Laminate veneers.  Jacket crowns.  Inlays.  Onlays.  If high transparency ceramic is required. 
  189. 189. Contraindications: Masking grossly discolored tooth.  When aiming for high fracture resistance.  All other common contraindications. 
  190. 190. MACHINABLE CERAMICS Summary
  191. 191. Classification: M a c h in a b l e C e r a m ic s C A D -C A M C e r a m ic s a ceramic restoration fabricated by use of a computer aided design computer aided milling C o p y -M il l e d C e r a m ic s a process of milling a structure using a device that traces the surface of a metal, ceramic or a polymer pattern and transfers the traced spatial positions to a cutting station.
  193. 193. Introduction: The introduction of Computer-Aided-Designing & Computer-Aided-Milling(CAD-CAM) systems to prosthetic dentistry represents a major technological breakthrough. It is now possible to design and fabricate ceramic restorations at a single appointment, as opposed to the traditional method of making impressions, fabricating of provisional prosthesis, and using a lab for development of the restoration. These restorations save dentists and patients time, provide an esthetic restoration, and have the potential for wear resistance.
  194. 194. History: Optical scanning and computer generation of restorations were attempted as early as 1971 (Altschuler, 1971/1973) but the continued improvement in technology, a number of systems are currently being investigated at this time……… Duret & Preston 1981 Brendestini et al 1985 Rekow 1987 Williams 1987 Duret et al 1988
  195. 195. Objectives: To eliminate traditional impression methods.  To design, the future restoration in accordance with the preparation, the function and natural anatomy,e.g. with the use of computer.  To produce the restoration chair side.  To improve the restoration qualities, mechanical resistance, marginal fit, surface quality and esthetics. 
  196. 196. Types of CAD – CAM Devices: DIRECT: Fully integrated CAD – CAM devices for chair side restorative approach. CAD & CAM stations are located at the dental office.  INDIRECT: System that consists of several modules with at least, distinctive CAD & CAM stations. 
  197. 197. Indirect Method: The optical impression is taken in the dental office, where CAD is done; data are transmitted to CAM station for restoration fabrication.  The optical impression is taken in the dental office; collected information is then transmitted to a central station, where CAD & CAM modules operate. 
  198. 198. Indirect Method:       Because of the overall dimensions and the cost of the indirect CAD – CAM devices, they are usually not located in the dental office, but more likely in a central laboratory where data is collected from different treatment places. E.g. …. Duret system*. Procera system* (Noble Bio-Care). Cicero system* (Elephant Industries). President system* (DCS Dental). CEREC SCAN* & CEREC InLAB* (Sirona Dental company)
  199. 199. Direct CAD - CAM CEREC, CEREC 2, CEREC 3
  200. 200. C E R E C S Y S T E
  201. 201. CEREC Systems: The CEREC system, developed in Zurich, Switzerland has been marketed for several years with the improvised CEREC 2 introduced in mid 1990’s, upgraded to CEREC 3 in the year 2000.
  202. 202. The equipment consists of a computer integrated imaging and milling system, with the restorations designed on the computer screen
  203. 203. Materials used with CEREC’s: Dicor MGC*(Machinable Glass Ceramic)(Dentsply): This is a mica based machinable glass ceramic containing 70% vol of crystalline phase. The unique “House of Cards” microstructure found in Dicor MGC is due to the inter locking of the small platelet shaped micacrystals with an average size of 1 – 2 microns. This particular structure leads to multiple crack deflections and ensures greater strength than leucite containing ceramics. 
  204. 204. Materials used with CEREC’s: Vita Mark II (Vident): These contain sanidine (KALSi O ) as a major crystalline phase within a glassy matrix.  3 8
  205. 205. Materials used with CEREC’s: ProCad (Ivoclar): Like Ivoclar's popular Empress™ material, ProCAD is reinforced with tiny leucite particles, and has been referred to as: "Empress on a stick".  Shade cross-reference: 100 = A1, A2, B1, B2, C1 200 = A3, A3.5 300 = B3, B4 400 = C2, D2, D3 500 = A4, C3, C4, D4
  206. 206. Materials used with CEREC’s: Vita IN-Ceram Blanks (Vita Zhanfabrik): These are third generation blanks from Vita.  The Spinell MgAl O .  The Alumina Al O .  The Zirconia ZrO  2 2 4 3 2.
  207. 207. The Spinell Blanks:  The fine chemical and mechanical properties of the highly pure synthetic spinell are used with the aim to obtain an esthetically appealing, translucent ceramic structures.
  208. 208. The Alumina Blanks:  These uses the advantages of the synthetic corundum that is prepared from bauxite prepared in electric melting furnace. The result is a dental all ceramic system with convincing mechanical properties.
  209. 209. The Zirconia Blanks:  This combines the fracture toughness of the meta-stable tetragonal zirconium oxide which is also referred to as “ceramic steel”.
  210. 210. Clinical Procedure: Preparation design. Optical impression. Computer generated restoration design. Milling procedure.