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Dental ceramics/prosthodontic courses

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Dental ceramics/prosthodontic courses

  1. 1. DENTAL CERAMICS INDIAN DENTAL ACADEMY Leader in continuing Dental Education www.indiandentalacademy.com
  2. 2. INTRODUCTION www.indiandentalacademy.com
  5. 5. HISTORICAL PERSPECTIVE • Stone age more than 10,000 years ago …. flaking • In 700 B.C., the Etruscans made ivory teeth and bone teeth • Porcelain was obtained in China by fluxing white china clay with “ chine stone” to produce a white translucent stone ware in about 1000 A.D www.indiandentalacademy.com
  6. 6. • The first known case of industrial espionage… a Jesuit father named D’entrecolles in 1717… • In 1774 a French apothecary named Alexis Duchateau • Nicholas Dubious de chemant of Paris in collaboration with Alexis Duchateau considerably improved the method of fabricating dentures. • In 1838 Elias Wildman • Italian dentist Fonzi … terrometallic teeth • patents of Weinstein and Weinstein(1962) and Weinstein et al (1962) which described the formulations of feldspathic porcelain www.indiandentalacademy.com
  7. 7. • The first commercial porcelain was developed in 1965 by Vita Zahnfabrik. • A significant improvement in fracture resistance was reported by Hughes in 1965 with the introduction of aluminous core porcelain. www.indiandentalacademy.com
  8. 8. CLASSIFICATION ACCORDING TO HISTORY • Earthenware: • Fired at low temperature and is relatively porous. • Stoneware: • Appeared in china in about 100 B.C • Porcelain: • Obtained by fluxing white China with “Chine stone” to produce a white translucent stoneware. www.indiandentalacademy.com
  9. 9. CLASSIFICATION ACCORDING TO FIRING TEMPERATURE: • High fusing : 1300 degree centigrade • Medium fusing : 1101-1300 degree centigrade • Low fusing : 850-1100 degree centigrade • Ultra low fusing :< 850 degree centigrade www.indiandentalacademy.com
  10. 10. CLASSIFICATION ACCORDING TO USE: Anterior Posterior Crowns Veneers Post and cores FPD Stain ceramic Glaze ceramic www.indiandentalacademy.com
  11. 11. CLASSIFICATION ACCORDING TO COMPOSITION: Pure alumina Pure Zirconia Silica glass Leucite based glass ceramic Lithia based glass ceramic www.indiandentalacademy.com
  12. 12. CLASSIFICATION ACCORDING TO PROCESSING METHOD:  Sintering  Partial sintering  Glass infiltration  CAD-CAM  Copy milling • ACCORDING TO TRANSLUCENCY  Opaque  Translucent  Transparent www.indiandentalacademy.com
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  15. 15. FELDSPAR : They are mixtures of potassium aluminum silicate K2O.Al2O3.6SiO2, and albite Na2O.Al2O3.6SiO2. when feldspar is melted at approximately 1250- 1500 degree Celsius, it fuses to become a glass with a free crystalline silica phase.. When feldspar is heated at temperatures between 1150 and 1530 degree centigrade it undergoes INCONGRUENT MELTING to form crystals of leucite which is a K-Al-Silicate mineral with a large coefficient of thermal expansion. www.indiandentalacademy.com
  16. 16. KAOLIN: • Is hydrated aluminum silicate (Al2O3.2SiO2.2H2O) that acts as a binder to increase the moldability of the unfired porcelain . Because of its opaqueness it is present in only very small quantities if at all. QUARTZ: • It is a high fusing material forms the framework around which the other ingredients flow. It prevents the slumping of the crown during the liquid phase. ALUMINA: Many European tooth manufacturers use alumina in place of silica to strengthen the teeth, especially around the pins.www.indiandentalacademy.com
  17. 17. FLUXES: • Potassium, lithium, sodium and calcium oxide and boric acid are used as fluxes by interrupting the integrity of the SiO4 network, and lower the softening temperature of a glass by reducing the amount of cross linking between silica and oxygen The O: Si ratio in a glass is of greatest importance and increasing this ratio will cause reduced viscosity, lowered fusion temperature and increased thermal expansion.www.indiandentalacademy.com
  18. 18. COLORING AGENTS: The coloring pigments added to porcelain are known as color frit. These are prepared by fritting metallic oxides into the basic glass used in porcelain. Some of the common colors used are: • Pink : Tin chromium or chroma alumina • Yellow : Indium or praesmodyium • Blue : Cobalt salt • Green : Chromium oxide • Grey : Iron oxide or platinum www.indiandentalacademy.com
  19. 19. OPACIFYING AGENT : • translucency …..metal oxide ….refractive index . …..melting point FLUORESCENCE : • The natural teeth possess a yellow white fluorescence, • the uranium salt, sodium di urinate. • T his salt produces a strong greenish-yellow color. • radiation hazards of including uranium. www.indiandentalacademy.com
  20. 20. STRUCTURE • Dental porcelains contain a crystal phase and glass phase based on the silica structure. This structure is characterized by the Si-O tetrahedron in which a Si 4+ cation is positioned at the center of a tetrahedron with O- anions at each four corners www.indiandentalacademy.com
  21. 21. • Potassium, sodium and calcium oxides are used as glass modifiers • Boric oxide can act as a flux and also as a glass former. • Oxides like alumina may react either way, depending on other factors such as composition. Such oxides are called intermediates. www.indiandentalacademy.com
  22. 22. PORCELAIN CONDENSATION • Porcelain is supplied as a fine powder that is designed to be mixed with water or another vehicle and condensed to desired form. The particles are of a particular size distribution to produce the most densely packed porcelain when packed. This provides two benefits: Lower firing shrinkage Less porosity. The methods of condensation are: • Vibration technique • Spatulation technique • Brush technique www.indiandentalacademy.com
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  30. 30. SINTERING OF PORCELAIN The purpose of firing is simply to fuse the particles together, a process called sintering. The condensed porcelain mass is placed ….. Preheating for 5 min …. rapid production of steam White areas are powder particles and the area between are voids www.indiandentalacademy.com
  31. 31. STAGES IN FIRING • LOW BISQUE: The glass grains have softened and have started to flow. The fired article exhibits rigidity but it is very porous. The powder particles lack complete cohesion. A negligible amount of firing shrinkage occurs. • MEDIUM BISQUE: The glass grains have flowed to the extent that the powder particles exhibit complete cohesion. The article is still porous and at this stage there is definite shrinkage. • HIGH BISQUE: After the high bisque stage, the shrinkage is complete and the mass exhibits a smoother surface but the body does not appear glazed. The work can be removed from the furnace and cooled at any of these stages, so that additions can be made. www.indiandentalacademy.com
  32. 32. • The fewer the firing cycles to which the restoration is exposed, the higher will be the strength and better the esthetics. • Minimum of three firings are needed for fabrication of ceramometal restoration: • Opaque • Dentin and enamel • Stain and glaze • Porcelain shrinks 30-40 % during firing- oversize the buildup. www.indiandentalacademy.com
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  34. 34. Porcelain for PFM are fired under vacuum thus as the furnace door closes the pressure is lowered to 0.1 atmosphere and the temp is raise until firing tempo is reached . th e vacuum is then released and the furnace pressure returns to 1 atm- Dense pore free porcelain. GLAZING • After porcelain is cleaned stains required are applied and porcelain returned to furnace for final glaze firing. When the glazing temp is reaches a thin glassy film( glaze) is formed by viscous flow on the porcelain surface. Glazed porcelain is stronger than unglazed. • Glaze is effective in reducing crack propagation. If glaze is removed by grinding transverse strength is reduced to half. www.indiandentalacademy.com
  35. 35. Two types of glazes : • Over glaze • Self glaze. • Porcelains may be characterized with stains and glazes to provide a more life like appearance. • One method of ensuring that the stains remain permanently is by incorporating the stains internally www.indiandentalacademy.com
  36. 36. COOLING: • Must be carried out gradually and uniformly. • Too rapid – surface cracking and loss of strength • Too slow- might induce formation of additional leucite. Increased the overall coefficient of thermal expansion cracking, crazing. • Less is the no of firing higher is the strength and better the esthetics. Too many firing cycles – lifeless over translucent porcelain. www.indiandentalacademy.com
  37. 37. BONDING PORCELAIN TO METAL The primary requirement for …… • The nature of bond can be divided into three main components: • Mechanical • Compressive • Chemical www.indiandentalacademy.com
  38. 38. Mechanical: • It is dependent upon good wetting of the metal or metal oxide surface by porcelain. It is improved by a textured surface. A rough surface may enhance the bond resistance against induced shear stresses, especially for base metal alloys. E.g.: air abrasion. Advantages: • Enhances wettability • Additive bond strength • Increased surface area Compressive: • Ceramo-metal systems are deliberately designed with a very small degree of mismatch in order to leave the porcelain in a state of compression.www.indiandentalacademy.com
  39. 39. Chemical bonding: • When dental porcelain is fired onto metal with a definite oxide (indium, tin or zinc oxide) layer, the oxygen surface of the molten glass diffuses within the oxygen surface on the metal to reduce then no. of bridging oxygen and thus improves the screening of cations at the interface www.indiandentalacademy.com
  40. 40. Procedure: The metal is degassed by heating at 1000 degrees in vacuum for around 10 min and then slowly air cooled in normal atmosphere. This procedure will: Degas the casting. Induce age hardening of the alloy. Base metal atoms will diffuse onto the surface to form an oxide film. Shear strengths of enamel porcelain bonds:www.indiandentalacademy.com
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  43. 43. METHODS OF STRENGTHENING CERAMICS • Minimize the effect of stress raisers • Develop redidual compressive stresses • Minimize the number of firing cycles • Minimize tensile stress through optimal design of ceramic prosthesis • Ion Exchange • Thermal tempering • Dispersion strengthening This is reinforcement with a dispersed phase of a different material that is capable of hindering a crack from propagating through the material • Transformation tougheningwww.indiandentalacademy.com
  44. 44. ABRASIVENESS OF DENTAL CERAMICS• Abrasive wear mechanisms for ceramics and tooth enamel are predominantly due to micro fracture which results from gouging, asperities, impact, and contact stresses that cause cracks or localized fracture. • Steps to minimize wear:  Ensure cuspid guided disclusion  Eliminate occlusal prematurities  Use metal in functional bruxing areas  If occlusion in ceramic, use ultralow fusing ceramics  Polish functional ceramic surfaces  Repolish ceramic surfaces periodically  Readjust occlusion periodically if needed.www.indiandentalacademy.com
  45. 45. • 1. Contour with flexible diamond disks, diamond burs, heatless stones or green stones (Silicone carbide) • 2. Finish with white stones or abrasive impregnated rubber disks, cups or points. • 3. Polish with fine impregnated rubber cups, and points or diamond paste applied with a brush • 4. Apply an over glaze layer. www.indiandentalacademy.com
  46. 46. ALLOYS USED FOR METAL- CERAMIC RESTORATIONS • HIGH NOBLE: • Gold-platinum- palladium • Gold palladium-silver • Gold-palladium • NOBLE: • Palladium-silver • High palladium PREDOMINANTLY BASE: Nickel-chromium Nickel-chromium- beryllium Cobalt-chromium www.indiandentalacademy.com
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  48. 48. FACTORS AFFECTING THE COLOR OF CERAMICS: • “A dark red that is yellower and less strong than cranberry, paler and slightly yellower than average garnet, bluer, less strong, and slightly lighter than pomegranate, and bluer and paler than average wine” www.indiandentalacademy.com
  49. 49. The three dimensions of color: • Hue: dominant color of an object, wavelength • Chroma: saturation • Value: lightness or darkness ….independent of hue • Metamerism: objects that appear to be color matched under one type of light appear different under another light source • Fluorescence: the property of an object to emit light of different wavelength than the one incident upon it • Eincident=Escattered+Ereflected+Eabsorbed+Etrans mitteed+Efluoresced • In the dental operatory or laboratory color matching is usually performed by the use of shade guide. www.indiandentalacademy.com
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  52. 52. • Dentin is more opaque than enamel and will reflect light.. pale yellow in color • Enamel……crystalline……. different refractory indices at the incisal region ….bluish white (thick) at cervical margin-yellow (thin. reflects color of underlying dentin) • …..Translucence……DEPTH • “Northern light from a blue sky during the middle portion of day that is slightly overcast” www.indiandentalacademy.com
  53. 53. PROPERTIES • Discussion of mechanical properties… IN VACUUM……HOLISTIC Restorative materials at our disposal: • Metals-high tensile strength, toughness, hardness, resistance to abrasion, fracture resistance, elasticity, ductility fatigue resistance • Polymers-inferior in most of these properties….BRITTLE FRACTURE • Composites-BRITTLE FRACTURE superb aesthetics • Ceramics-No ductility, high compressive strength, low shear and tensile strengths excellent aesthetics www.indiandentalacademy.com
  54. 54. • COMPRESSIVE STRENGTH: • Maximal stress required to fracture a structure under compression. • Enamel:37,800 psi • Dentin: 44,200 psi • Porcelain : 25,000 psi • Metalceramic alloys : yield strength of 65- 80,000 psi • TENSILE STRENGTH: • Maximal stress required to fracture a structure under tension. • Porcelain: 5,000 psiwww.indiandentalacademy.com
  55. 55. • HARDNESS (KHN): • Enamel: 343 • Dentin: 68 • Porcelain: 460 • FLEXURAL STRENGTH (BENDING STRENGTH OR MODULOUS OF RUPTURE): • Force per unit area at the point of fracture of a test specimen subjected to flexural loading. • Feldspathic porcelain: 141 MPa • Aluminous porcelain: 139 MPa • IPS Empress2: 400 MPa • Gold alloy: 350-600 MPawww.indiandentalacademy.com
  56. 56. • FRACTURE TOUGHNESS: • Feldspathic porcelain: 0.9-1.5 MPa.m1/2 • Aluminous porcelain: 2-2.9 • Yttria stabilized zirconia: 9 • Gold alloy: 20 • Enamel: 0.7 • IPS Empress2: 3.3 • THERMAL COEFFICIENT OF EXPANSION: ( mm/mm.K)*10-6 • Change in unit length per unit rise in temperature • Tooth : 11.4 • Low fusing ceramic: 12.2-15.8 • IPS Empress 2: 10.6 • Ceramometal: ? www.indiandentalacademy.com
  57. 57. • THERMAL CONDUCTIVITY (cal.cm/cm2.sec.C): • Ability of a body to transfer energy • Enamel: 0.0022 • Dentin: 0.0015 • Porcelain: 0.0030 • THERMAL DIFFUSIVITY (cm2/sec): • Enamel: 0.0042 • Dentin: 0.0026 • Porcelain: 0.64 • “Effectiveness of a material in preventing heat transfer is directly dependent on its thickness and inversely dependent on itswww.indiandentalacademy.com
  58. 58. • MODULOUS OF ELASTICITY Porcelain: 69GPa Type IV gold alloy: 99.3 GPa Composite: 16.6Gpa • Because of their moderately high m of elasticity and relatively low tensile strength porcelains can undergo very little elastic deformation (0.1%) before they rupture i.e., they are not flexible www.indiandentalacademy.com
  59. 59. RECENT ADVANCES IN DENTAL CERAMICS www.indiandentalacademy.com
  60. 60. • METAL CERAMIC CROWNS BASED ON BURNISHED FOIL COPINGS: THE CAPTEK SYSTEM • Malleable Captek metal strips are burnished on a refractory die to fabricate the metal coping of a metal ceramic crown without the use of a melting and casting process. • The finished metal coping may be described as a composite material consisting of a gold matrix reinforced with small particles of a Pt-Pd-Au alloy. • The units are then veneered with two thin layers of opaque porcelain and other veneering porcelains. • The Captek coping has a thickness of 0.25 mm which is half of the traditional cast metals thus providing additional space for vennering porcelain. www.indiandentalacademy.com
  61. 61. •Indications: crowns and FPDs www.indiandentalacademy.com
  62. 62. • CASTABLE GLASS CERAMICS : DICOR Dicor is a castable glass (55% tetraflurosilicic mica crystals) that is formed into an inlay, facial veneer or full crown restoration by a lost wax casting process…….. , it is covered by a protective embedment material and subjected to heat treatment that causes mica to grow within the glass matrix. This process is called CERAMMING. Then it is fit on dies, ground as necessary and coated with veneering porcelain. www.indiandentalacademy.com
  63. 63. • ADV: Ease of fabrication Improved esthetics-chameleon effect Minimal shrinkage Good marginal fit High flexural strength Low thermal expansion Minimal abrasiveness of enamel • DISADV: Limited use in low stress areas (Low tensile strength) Inability to be colored internally www.indiandentalacademy.com
  64. 64. • PRESSABLE GLASS CERAMICS (IPS EMPRESS): • It is provided as core ingots that are heated and pressed until the ingot flows into a mold. It contains a higher proportion of leucite crystals that increase resistance to crack propagation. The hot pressing process occurs over a 45 min period at high temperature to produce the ceramic substructure. The crown form can be either stained and glazed or built up using a conventional layering technique. • ADV: • Lack of metal • Translucent ceramic core • High flexural strength • Excellent fit • Excellent esthetics • DISADV: • Potential to fracture in posterior areas • Need to use resin cementwww.indiandentalacademy.com
  65. 65. • INFILTRATED CERAMICS (INCERAM): – Available as two component system: – Powder: alumina/spinell/zirconia • - Low viscosity glass  A slurry of the powder is slip cast on a refractory die and heated in a furnace at 1120 degree centigrade for 10 hrs and then it is infiltrated with the low viscosity glass at 1100 degree centigrade for 4 hrs to eliminate porosity and to strengthen the slip cast core. • ADV: – Lack of metal substructure – High flexural strength – Excellent fit • DISADV:  Opacity  Special die material and high temperature oven is required  Have abrasive properties www.indiandentalacademy.com
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  67. 67. • CAD –CAM CERAMICS (PROCERA, CEREC, CELAY, DICOR MGC): • It stands for Computer aided design/Computer aided manufacturing. • It is supplied as ceramic ingots available in various shades. These are placed in a machinable apparatus to produce the desired contours. This machined restoration is checked for fit on the tooth. Occlusal adjustment is done followed by polishing, etching and bonding the restoration to the prepared tooth. www.indiandentalacademy.com
  68. 68. • ADV: • Negligible porosity levels • Freedom from making an impression • Need for a single patient appointment (with CEREC system) • Good patient acceptance • DISADV: • Need for costly equipment • Lack of computer controlled processing support for occlusal adjustment • Technique sensitive nature of surface imaging. www.indiandentalacademy.com
  69. 69. REVIEW OF LITERATURE Francois Duret, Jean Louis Blouin and Bernard Duret in 1988 discussed the role of CAD-CAM in dentistry. They explained the equipment needed in the dental office, the design of the clinical crown the build up required and the milling process. They concluded that CAD CAM had exciting possibilities in the coming years. www.indiandentalacademy.com
  70. 70. J.Robert Kelly, Ichiro Nishimura and Stephen D. Campbell in 1996 presented a brief history of dental ceramics and offerd perspectives on recent research aimed at the future development of ceramics for clinical use . They concluded that sound scientific and collaborative foundations exist for the continued understanding and improvement of dental ceramic systems. Frankie Sulaiman, John Chai, Lee M. Jameson and Wayne T. Wozniak in 1997 compared the marginal fit of In-Ceram, IPS Empress and Procera Crowns. They found In-Ceram to have the greatst marginal fit discrepancy followed by Procera and IPS Empress. The facial and lingual margins exhibited significantly larger marginal discrepancies than the proximal margins. www.indiandentalacademy.com
  71. 71. John Chai, Yukuta Takahashi, Frankie Suleiman, Kok- heng Chong and Eugene P.Lautenschlager in 2000 compared the probability of fracture of 4 systems of all ceramic crowns i.e.,Inceram, CEREC 2, IPS Empress and Procera. . Ten crowns of each system were fabricated and compressed at 45 degree . The data obtained was subjeced to statistical analysis. They found no significant difference in the probability of fracture among the 4 systems. www.indiandentalacademy.com
  72. 72. A study conducted in our department under the able guidance of Dr. N.P. Patil sir evaluated the shear bond strength of three porcelain repair systems with various surface treatments in response to thermal stress. This study was conducted on intentionally fractured 30 porcelain-fused-to-metal samples. 3M Scotchbond system, Clearfil Porcelain Bond and Ceramic Repair Materials were used to restore the fractured porcelain surface. The findings of the study suggests that Clearfil Porcelain Bond undergoes least changes in the bond strength of composite resin to porcelain or metal surface after thermocycling treatment. www.indiandentalacademy.com
  73. 73. Another study conducted in our department under the able guidance of Dr. N.P.Patil sir examined the effect of recasting of base metals on bond strength of porcelain. It was observed that the addition of one third new metal to the alloy once cast, restores the bonding characteristics of PFM and also that Ni-Cr had superior bonding properties with porcelain than Co-Cr alloys. www.indiandentalacademy.com
  74. 74. SUMMARY & CONCLUSION •Considerable advances in the field of dental ceramics has brought forth novel processing technologies which have enhanced the properties and clinical acceptability of these materials. •Yet, these have yet again highlighted our inability to comprehend its greatest deficiencies, i.e., inadequate tensile strength and brittleness. •It is this challenge to the upcoming prosthodontists that ceramics beckons, and to which we all should rise.www.indiandentalacademy.com
  75. 75. BIBLIOGRAPHY • Restorative dental materials – Robert G.Craig, John M. Powers,8th Edition. • Phillips’science of dental materials – Kenneth J.Anusavice,11th Edition. • Notes on Dental materials – E.C.Combe,6th Edition. • Ralph W.Philips- Skinner’s Science of Dental Materials. www.indiandentalacademy.com
  76. 76. • Dental Materials Properties and Manipulation – Robert G.Craig,O’Brien,Powers. • Clinical Handling of Dental Materials- Smith,Wright,Brown. • Clinical aspects of Dental Materials – Philips – 8th Edition. • Theory and Practice for Ceramo Metal Restorations – Masahiro Kuwata • The Science and Art of Dental Ceramics,Vol II : Bridge Design and Laboratory Proceedures In Dental Ceramics – John W.Mclean www.indiandentalacademy.com
  77. 77. •Evaluation and comparison of shear bond strength of three porcelain repair systems with various surface treatments in response to thermal stress – an in vitro study - Dr. Meenakshi T. •Kelly J.R.et al .Ceramics in Dentistry: Historical roots and Current Perspective.J Prosthet Dent 1996;75:18-32. •Duret F,Jean-louis Blouin,Duret Bernard. CAD-CAM in Dentistry.JADA 1988;117:715-720. •Sulaiman F,Chai J, Jameson LM, A Comparison of the Marginal Fit of In-Ceram,Ips Empress,and Procera Crowns. Int J Prosthodont 1997;10:478-484. •Chai J et al, Probability of Fracture of All-Ceramic Crowns. Int J Prosthodont 2000;13:420-424.www.indiandentalacademy.com
  78. 78. Thank Youwww.indiandentalacademy.com