Se ha denunciado esta presentación.
Utilizamos tu perfil de LinkedIn y tus datos de actividad para personalizar los anuncios y mostrarte publicidad más relevante. Puedes cambiar tus preferencias de publicidad en cualquier momento.

All Ceramics - Dental

All Ceramics - Dental

  • Sé el primero en comentar

All Ceramics - Dental

  1. 1. All Ceramics – Dr. Nithin Mathew 1
  2. 2. ALL CERAMICS (Material Aspect) Dr. Nithin Mathew
  3. 3. All Ceramics – Dr. Nithin Mathew CONTENTS 3 • Introduction • History • Classification • Composition • Advantages & disadvantages • Manufacture • Fabrication • Methods of strengthening ceramics • All Ceramic Systems • Selection of ceramics • Conclusion • References
  4. 4. All Ceramics – Dr. Nithin Mathew INTRODUCTION • Ceramic - First material to be artificially made by humans. • Ceramic is derived from the Greek word ‘keramos’, which means ‘potter's clay’. • Earliest techniques consisted of shaping the item in clay/soil and then baking it to fuse the particles together, which resulted in coarse and porous products. 4
  5. 5. All Ceramics – Dr. Nithin Mathew • The term CERAMIC refers to any product made essentially from a non metallic inorganic material processed by firing at a high temperature to achieve desirable properties. • DENTALCERAMIC (Anusavice) • A specially formulated ceramic material that exhibits adequate strength, durability and color that is used intraorally to restore anatomic form and function, and/or esthetics. 5
  6. 6. All Ceramics – Dr. Nithin Mathew • CERAMICS Compounds of one or more metals with a non metallic element (usually silicon, boron, oxygen) that may be used as a single structural component or as one of the several layers that are used in the fabrication of a ceramic based prosthesis. (Glossary of Prosthodontic Terms) • PORCELAIN A ceramic material formed of infusible elements joined by lower fusing materials. (Glossary of Prosthodontic Terms) 6
  7. 7. All Ceramics – Dr. Nithin Mathew Terminologies • COPY-MILLING • A process of machining a structure using a device that traces the surface of master metal, ceramic, or polymer pattern and transfers the traced spatial positions to a cutting station where blank is cut or ground in a manner similar to key-cutting procedure. • SINTERING • The process of heating closely packed particles to achieve interparticle bonding and sufficient diffusion to decrease the surface area or increase the density of the structure. 7
  8. 8. All Ceramics – Dr. Nithin Mathew • VITRIFICATION : • The development of a liquid phase by reaction or melting, which on cooling provides the glassy phase, resulting in a vitreous structure. • When the glass begins to crystallize , the process is called DE-VITRIFICATION. • GREEN STATE : • A term referred to as pressed condition before sintering. • SPINEL : • A crystalline mineral composed of mineral oxides such as magnesium oxide or aluminium oxide. 8
  9. 9. All Ceramics – Dr. Nithin Mathew • SLIP CASTING : • A process used to form “green” ceramic shapes by applying a slurry of ceramic particles and water or special liquid to a porous substrate, thereby allowing capillary action to remove water and densify the mass of deposited particles. 9
  10. 10. All Ceramics – Dr. Nithin Mathew 10 ADA SPECIFICATION  Dental ceramic : 69  Dental porcelain teeth : 45  Metal ceramic system : 38 ISO SPECIFICATION  Dental ceramic : 6872  Dental porcelain teeth : 22112  Metal ceramic system : 9693
  11. 11. All Ceramics – Dr. Nithin Mathew HISTORY  1728 : Proposed the use of porcelain in dentistry – Pierre Fauchard  1774 : Made first porcelain denture– Alexis Duchateau  1789 : First porcelain tooth material patented - de Chemant & Duchateau  1808 : Terrometallic porcelain tooth – Fonzi  1817 : Porcelain teeth introduced in the US – Planteau  1825 : Commercial production of porcelain teeth (SS White Company) – Samuel Stockton  1837 : Introduced improved version of porcelain- Ash  1887 : Introduced porcelain jacket crown using platinum foil matrix technique - CH. Land  1903 : First ceramic crowns introduced to dentistry – Charles Land  1957 : Introduced Vacuum firing - Vines & Sommelman  1962 : Formulation of feldspathic porcelain – Weinstein & Weinstein 11
  12. 12. All Ceramics – Dr. Nithin Mathew  1963 : First commercial feldspathic porcelain developed – Vita Zahnfabrik  1965 : Aluminous core ceramic – Mclean and Hughes  1968 : Use of glass ceramics – MacCulloh  1983 : Bonding composite resin to acid etched porcelain – Simonsen & Calamia  1983-84 : First castable ceramic – Dicor – Grossman & Adair  1985 : First CAD/CAM was publicly milled and installed in the mouth – Morman & Brandestini  1987 : CEREC 1 was introduced  1989 : First slip cast alumina ceramic- Inceram alumina- Sadoun  1991 : Pressable glass ceramics- Wohlwent  1994 : CEREC 2 was introduced 12
  13. 13. All Ceramics – Dr. Nithin Mathew  1997 : Sirona CROWN 1.0 program for producing full-ceramic posterior crowns was introduced  2000 : CEREC 3 was introduced  2008 : Sirona released the MCXL milling unit which can produce a crown in 4 mins 13
  14. 14. All Ceramics – Dr. Nithin Mathew CLASSIFICATION  Firing temperature  Use / Indications  Fabrication techniques  Crystalline phases  Microstructure  Translucency  According to system 14
  15. 15. All Ceramics – Dr. Nithin Mathew FIRING TEMPERATURE  High fusing : > 1300°C  Medium fusing : 1101 - 1300°C  Low fusing : 850 - 1100°C  Ultralow fusing : < 850°C 15 USE / INDICATIONS  Veneers  All ceramic crowns  Inlays and onlays  Ceramic dentures  Post & Cores  Orthodontic brackets  FPD
  16. 16. All Ceramics – Dr. Nithin Mathew FABRICATION TECHNIQUE  Sintered (Metal Ceramics)  Cast (Dicor)  Heat pressed (IPS Empress)  Slip cast (Inceram)  Machined (Cerec Vitablocs)  Partial sintering and glass infiltration  CAD CAM & copy milling 16 CRYSTALLINE PHASE  Alumina based (Optec HSP)  Feldspar based (Conventional Ceramics)  Leucite based (IPS Empress)  Spinel based (Inceram Spinel)
  17. 17. All Ceramics – Dr. Nithin Mathew TRANSLUCENCY  Opaque  Translucent  Transparent 17 MICROSTRUCTURE  Glass  Crystalline  Crystal containing glass
  18. 18. All Ceramics – Dr. Nithin Mathew COMPOSITION  Pure alumina  Pure Zirconia  Silica glass  Spinelle  Leucite based glass ceramic  Lithia based glass ceramic 18 APPLICATION  Core porcelain  Body porcelain  Enamel porcelain
  19. 19. All Ceramics – Dr. Nithin Mathew According To Systems • Metal ceramic systems • Cast metal systems and non cast systems • All –ceramic systems • Conventional powder slurry ceramic i. Alumina reinforced porcelain ii. Magnesia reinforced porcelain iii. Leucite reinforced iv. Zirconia-whisker fiber reinforced v. Low fusing ceramics 19
  20. 20. All Ceramics – Dr. Nithin Mathew • Castable Ceramics i. Flouormicas ii. Other Glass Ceramics • Machinable Ceramics i. Analogus Systems a. Copymilling a. Mechanical b. Automated b. Erosive Techniques a. Sono - erosion b. Spark - erosion ii. Digital Systems (CAD/CAM) i. Direct ii. Indirect 20 • Pressable Ceramics i. Shrink free ceramics ii. Leucite reinforced ceramics • Infiltrated Ceramics i. Alumina based ii. Spinel based iii. Zirconia based
  21. 21. All Ceramics – Dr. Nithin Mathew • Primary constituent • Minerals composed of potash (K₂O), soda(Na₂O) and silica (SiO₂) • 75-85% Feldspar • 4-5% • Increases the moldability of the plastic porcelain • Serves as a binder • Consists of Al₂O₃ 2SiO₂ 2H₂O (Hydrated Aluminium Silicate) • Kaolin is opaque and can lower the translucency of porcelain Kaolin • Present in concentrations of 13-14% • Provide strength, firmness and improve translucency of porcelain • Serves as a framework for other ingredients Quartz 21 Composition of Dental Ceramics
  22. 22. All Ceramics – Dr. Nithin Mathew 22 GLASS MODIFIERS • Potassium, sodium and calcium oxides • Serve as fluxes • Lower the viscosity of glass • Increase thermal expansion OPACIFYING AGENTS • Zirconium oxide • Titanium oxide • Tin oxide
  23. 23. All Ceramics – Dr. Nithin Mathew PIGMENTS • To obtain various shades to mimic natural tooth colour. • Made by fusing metallic oxide with fine glass and feldspar & regrinding to a powder. . 23 Metallic oxide Colour • Iron or nickel oxide ⎼ Brown • Copper oxide ⎼ Green • Titanium oxide ⎼ Yellowish brown • Manganese oxide ⎼ Lavender • Cobalt oxide ⎼ Blue
  24. 24. All Ceramics – Dr. Nithin Mathew ADVANTAGES of Dental Ceramics  Highly esthetic  Biocompatibility  Electrical Resistance  Thermal Insulation  Wear resistance  Can be formed to precise shapes  Ability to be bonded to tooth structure 24
  25. 25. All Ceramics – Dr. Nithin Mathew DISADVANTAGES  Brittleness  Fabrication : Technique sensitive  Wear of opposing natural teeth  Difficult to repair intraorally  High cost of fabrication 25
  26. 26. All Ceramics – Dr. Nithin Mathew MANUFACTURING OF CERAMICS • Pyro-chemical reactions during manufacture of porcelain: • Ceramic raw materials are mixed together in a refractory crucible and heated to a temperature well above their fusion temp • Series of reactions occur. 26 CaCO3 P2O5 BaCO3 SiO2 Al2O3 MgO MgF2 CaF2
  27. 27. All Ceramics – Dr. Nithin Mathew MANUFACTURING OF CERAMICS • After the water of crystallization is lost, • Flux reacts with the outer layers of silica, kaolin and feldspar • Feldspar fuses and intermingles with kaolin and quartz • Feldspar undergoes decomposition to form glass and leucite • The molten glass begins to dissolve the quartz and kaolin • Continuous heating results in total dissolution • Then the fused mass is quenched in water 27 CaCO3 P2O5 BaCO3 SiO2 Al2O3 MgO MgF2 CaF2
  28. 28. All Ceramics – Dr. Nithin Mathew • Internal stresses within the glass are produced and breaks into fragments frit • The process of blending, melting and quenching the glass is called FRITTING 28 CaCO3 P2O5 BaCO3 SiO2 Al2O3 MgO MgF2 CaF2 Crucible
  29. 29. All Ceramics – Dr. Nithin Mathew 29 Melting CaCO3 P2O5 BaCO3 SiO2 Al2O3 MgO MgF2 CaF2 Tank with cool water Quenching FritSieving MANUFACTURING OF CERAMICS
  30. 30. All Ceramics – Dr. Nithin Mathew • Ceramics : 2 phases • Glassy Phase (Vitreous) • Provides translucency • Makes ceramic brittle • Crystalline Phase • Added to improve the mechanical properties • Newer ceramics (35-90%) 30
  31. 31. All Ceramics – Dr. Nithin Mathew DISPENSING • Conventional dental porcelain kit supplied as a kit containing : • Fine ceramic powder in different shades of enamel, dentin, core/opaque • Special liquid or distilled water • Stains and colour modifiers • Glazes and add-on porcelain • Shade guide 31
  32. 32. All Ceramics – Dr. Nithin Mathew FABRICATION OF CERAMIC RESTORATIONS • The fabrication of conventional porcelain restoration is by : • Condensation • Sintering • Glazing • Cooling CONDENSATION : • Padding or packing of wet porcelain into position • The movement of particles is generated by vibration, spatulation or whipping, brush technique and spray opaquing. 32
  33. 33. All Ceramics – Dr. Nithin Mathew CONDENSATION : • Build-up of Cervical Porcelain • Build-up of Body Porcelain • Cut-back • Build-up of Enamel Porcelain • Condensation methods: • MANUAL CONDENSATION • ULTRASONICCONDENSATION 33
  34. 34. All Ceramics – Dr. Nithin Mathew Advantages of ultrasonic condensation: • Reduces the fluid content of layered ceramics; resulting in denser and more vibrant porcelain mass. • Enhances translucency and the shade qualities of the fired ceramic. • Shrinkage can be reduced to below 5% • Time-saving as it reduces the number of compensatory firing cycles 34
  35. 35. All Ceramics – Dr. Nithin Mathew SINTERING / FIRING : • Process of heating closely packs particles to achieve interparticle bonding and sufficient diffusion to decrease the surface area or increase density of the structure. • Process of partial fusion of compact glass • Steps: • Pre-heating the furnace • Condensed mass placed • Green porcelain is fired 35
  36. 36. All Ceramics – Dr. Nithin Mathew Pre-heating (Drying): • Placing the porcelain object on a tray in front of a preheated furnace at 650C for 5min for low fusing porcelain and at 480C for 8min for high fusing porcelains till reaching the green or leathery state. 36 • Significance: • Removal of excess water allowing the porcelain object to gain its green strength. • Preventing sudden production of steam that could result in voids or fractures. Ceramic particles held together in the “green state” after all liquid has been dried off
  37. 37. All Ceramics – Dr. Nithin Mathew SINTERING / FIRING : 37 FIRING TECHNIQUES According to temperature presetting: Temperature controlled method Temperature – time control method According to the media employed for firing: AIR FIRING Porosity due to air inclusion VACUUM FIRING Reduce porosity DIFFUSABLE GASES Helium, hydrogen or steam are substituted for the ordinary furnace
  38. 38. All Ceramics – Dr. Nithin Mathew Stages of Maturity of Porcelain during Firing Bisque bake A series of stages of maturation in the firing of ceramic materials depending on the degree of pyrochemical reaction and sintering shrinkage occurring before vitrification (glazing). • Low bisque • Medium bisque • High bisque 38
  39. 39. All Ceramics – Dr. Nithin Mathew • Low bisque • Surface of porcelain is very porous and will easily absorb water. • Medium bisque • Surface is still porous but the flow of the glass grains is increased and entrapped air will become sphere shaped. • High bisque • Surface is completely sealed and presents a smooth texture. • Overfired porcelain become milky or cloudy in appearance – Devitrification. 39
  40. 40. All Ceramics – Dr. Nithin Mathew STAGES OF MATURITY 40 Low bisque stage Medium bisque stage High bisque stage Characteristics Grains of porcelain start to soften and coalesce at the contact points Flow of glass grains increase and the residual entrapped furnace air becomes sphere shaped Firing shrinkage is complete, and has adequate strength, for any corrections by grinding prior to glazing Particle cohesion Incomplete Considerable Complete Porosity Highly porous and absorbs water Reduced although still porous Slight/absent depending upon the material used Shrinkage Minimal Majority / definite Complete Strength Weak & friable Moderate High Surface texture Porous Matte surface Egg shell appearance Color & translucency Opaque Less opaque Color and translucency developed
  41. 41. All Ceramics – Dr. Nithin Mathew GLAZING : • Produces smooth, shiny and impervious outer layer, also effective in reducing crack propagation. • 2 ways : • Add-on glazing • Self glazing – most preferred technique COOLING : • Carried out slowly • Rapid cooling results in cracking or fracture of glass and loss of strength. • After firing, placed under a glass cover to protect it from air current and contamination by dirt. 41
  42. 42. All Ceramics – Dr. Nithin Mathew Porcelain Surface Treatment  Natural or Autoglaze • Porcelain has the ability to glaze itself when held at its fusing temperature in air for 1-4 mins. • Porcelain loses its ability to form a natural glaze after multiple firings  Applied Overglaze • Applied overglaze is a low fusing clear porcelain painted on to the restoration and fired at a fusing temperature much lower than that of the dentin and enamel porcelain. • An applied overglaze is indicated in large restoration that have numerous corrections. 46
  43. 43. All Ceramics – Dr. Nithin Mathew Instrumentation for Finishing and Polishing Ceramic Restorations 47 Sequence Instruments 1 Medium to fine grit diamond instrument 2 30 fluted carbide burs 3 Rubber, abrasive impregnated porcelain polishing points 4 Diamond polishing paste
  44. 44. All Ceramics – Dr. Nithin Mathew Methods of Strengthening Ceramics • Minimize the effect of stress raisers • Develop residual compressive stresses • Minimize the number of firing cycles • Ion exchange • Thermal tempering • Dispersion strengthening • Transformationtoughening 48
  45. 45. All Ceramics – Dr. Nithin Mathew 1. Minimize the effect of stress raisers • Stress raisers are discontinuities in ceramic and metal ceramic structure that causes stress concentration. • Restoration should be designed in such a way that it avoids exposure of ceramic to high tensile stresses. • Use of maximum thickness of ceramic on the occlusal surface. • Abrupt changes in the shape or thickness in ceramic contour should be avoided. • Sharp line angles in the preparation can cause stress concentration. 49
  46. 46. All Ceramics – Dr. Nithin Mathew 2. Develop residual compressive stresses • The coefficient of thermal contraction of metal should be slightly higher than that of porcelain. • Metal contracts slightly more than the porcelain on cooling from firing temperature to room temperature • Leave porcelain in residual compression and provides additional strength for the prostheses. 50
  47. 47. All Ceramics – Dr. Nithin Mathew 3. Minimize the number of firing cycles • Leucite is a high expansion crystal phase which affects the thermal contraction coefficient of porcelain. • Multiple firings increases concentration of crystalline leucite. • Increasing the no. of firing cycles can increase the LCTE of veneering porcelain. This leads to stresses on cooling. 51
  48. 48. All Ceramics – Dr. Nithin Mathew 4. Ion exchange/ Chemical tempering • Effective method of inducing residual compressive stresses. • Sodium containing glass article is placed in a bath of molten potassium nitrate • Exchange of ions take place • Since potassium ion is 35% larger than sodium ion, squeezing of the potassium ion creates very large residual compressive stresses. • Potassium rich slurry, applied to ceramic surface and heated to 450°C for 30 mins. 52
  49. 49. All Ceramics – Dr. Nithin Mathew 5. Thermal Tempering • Creates residual compressive stresses by rapidly cooling the surface of the object while it is in the molten state. • Rapid cooling produces a skin of rigid glass surrounding a molten core. • The solidifying molten core as it shrinks, creates residual compressive stress within the outer surface. 53
  50. 50. All Ceramics – Dr. Nithin Mathew 6. Dispersion Strengthening • Process of strengthening ceramics by reinforcing them with a dispersed phase of a different material. • Most dental ceramics are reinforced by dispersion of crystalline substances. • Ex. Alumina in aluminous porcelain, spinel in In Ceram. • When crystalline material such as alumina (Al₂O₃) is added to a glass, the glass is strengthened and crack propagation does not take place easily. • Resulted in development of aluminous porcelain for porcelain jacket crowns. 54
  51. 51. All Ceramics – Dr. Nithin Mathew 7. Transformation Toughening • This method also relies on dispersion of a crystalline material within the ceramic. • Strengthening occurs due to a change in the crystal structure under stress which prevents crack propagation. • Dental ceramics based primarily on zirconia crystals when heated to a temperature between 1470°C and 2010°C undergo change in the crystal structure from tetragonal to a monoclinic phase at approx. 1150°C • The toughening mechanism results from the controlled transformation of metastable tetragonal phase to the stable monoclinic phase. 55
  52. 52. All Ceramics – Dr. Nithin Mathew ALL CERAMIC SYSTEMS • Classified according to the method of fabrication: • Conventional (powder – slurry) ceramics • Infiltrated / Slip Cast Ceramics • Castable Ceramics • Pressable Ceramics • Machinable Ceramics 56
  53. 53. All Ceramics – Dr. Nithin Mathew CONVENTIONAL CERAMICS (POWDER – SLURRY)
  54. 54. All Ceramics – Dr. Nithin Mathew • Supplied as powders in different shades & translucencies. • Mixed with water to form slurry • Slurry build up in layers on a refractory die 58
  55. 55. All Ceramics – Dr. Nithin Mathew ALUMINOUS CORE PORCELAIN • Mc Lean and Hughes developed a PJC with an alumina reinforced • Significant improvement in fracture resistance • Consisted of a glass matrix containing between 40-50 wt% of Al2O3. • Large sintering shrinkage (15-20%) • Inadequate translucency • Principle indication: maxillary anterior crown restoration 59
  56. 56. All Ceramics – Dr. Nithin Mathew DisadvantagesAdvantages • Improved Fracture Resistance 60 • Low CTE : 8 x 10-6/0C. • Large sintering shrinkage (15-20%) • Improvement in strength is insufficient to bear high stresses
  57. 57. All Ceramics – Dr. Nithin Mathew MAGNESIA – REINFORCED PORCELAIN • O’Brien in 1984 • High expansion ceramics • Core material • Crystalline magnesia (40-60%) ‘Forsterite’. • Magnesia crystals strengthen glass matrix by both dispersion strengthening and crystallization within the matrix . • Flexural strength is 131 MPa • Doubled upto 269 MPa by the addition of glaze. 61
  58. 58. All Ceramics – Dr. Nithin Mathew Advantages 62 • Increased co-efficient of thermal expansion • Improved strength (glass infiltration of magnesia core) • High expansion property
  59. 59. All Ceramics – Dr. Nithin Mathew LEUCITE-REINFORCED PORCELAIN • They are feldspathic porcelains, dispersion strengthened by crystallization of leucite crystals in the glass-matrix. • The leucite and glassy components are fused during the baking process at 10200C. • Leucite crystals in the glass - matrix (50%). • Strength : Nucleation and growth of leucite crystals. • Translucency : Closeness of the refractive index of leucite with that of the glass matrix. • Flexure strength : approximately 140 MPa. 63
  60. 60. All Ceramics – Dr. Nithin Mathew DisadvantagesAdvantages • High strength (leucite reinforcement) • Good translucency • Moderate flexural strength 64 • Marginal inaccuracy due to sintering shrinkage. • Fracture in posterior teeth. • High abrasive effect on opposing teeth.
  61. 61. All Ceramics – Dr. Nithin Mathew INFILTRATED / SLIP CAST CERAMICS
  62. 62. All Ceramics – Dr. Nithin Mathew GLASS INFILTRATED CORE CERAMICS • Inceram Alumina • Inceram Spinel • Inceram Zirconia • 2 components : Powder & Glass • Fabrication: • Powder mixed with water to form suspension called “SLIP” • SLIP is painted onto refractory die : absorbs water – leaving solid alumina • Baked at 11200C for 10 hours : opaque, porous core • Glass powder applied to core and fired at 11000C for 3-4hrs • Molten glass infiltrates the porous alumina or spinel by capillary action • Veneering 66
  63. 63. All Ceramics – Dr. Nithin Mathew Die preparation Mixing aluminous powder with water to produce slip The slip is painted onto the die with a brush The water is removed by the capillary action of the porous gypsum, which packs the particles into a rigid porous network Sintering : 10 Hrs 11200C Porous network
  64. 64. All Ceramics – Dr. Nithin Mathew Glass powder is used to fill the pores in the alumina core. Glass Infiltration (4hrs 11000C) Glass becomes molten and flows into the pores by capillary diffusion Removal of excess glass Veneering with esthetic porcelain
  65. 65. All Ceramics – Dr. Nithin Mathew • The internal surface is sandblasted (with 50µ A12O3) • Since the density of In-ceram core makes conventional methods of etching with HF acid ineffective for bonding with a resin-cement. 69
  66. 66. All Ceramics – Dr. Nithin Mathew INCERAM ALUMINA • Developed by a French scientist and dentist Dr. Michael Sadoun (1980) and first introduced in France in 1988. Composition: Two three-dimensional interpenetrating phases : • Alumina/ Al2O3 crystalline : 99.56 wt% • An Infiltration of glass lanthanum aluminosilicate 70
  67. 67. All Ceramics – Dr. Nithin Mathew • Lanthanum • Decreases the viscosity of the glass to assist infiltration • Increases its refractive index to improve translucency. Fabrication stages : • Slip casting • Veneering of core 71
  68. 68. All Ceramics – Dr. Nithin Mathew PROPERTIES STRENGTH : • Densely packed crystalline particles (70% alumina) limit crack propagation and prevent fracture. • Flexure strength : 450 MPa range 72
  69. 69. All Ceramics – Dr. Nithin Mathew PROPERTIES COLOR : • Final color : influenced by the color of the alumina core (opaque). • Colorants used : transitional metal ions incorporated into the glass structure itself • Spinel ceramic : the core is more transparent and its corresponding infiltration glass is slightly tinted. 73
  70. 70. All Ceramics – Dr. Nithin Mathew DisadvantagesAdvantages • Minimal firing shrinkage, hence an accurate fit. • High flexure strengths (3 times) • Aluminous core (opaque) : used to cover darkened teeth or post/ core. • Wear of opposing teeth is lesser • Biocompatible : less plaque accumulation. 74 • Requires specialized equipment. • Poor optical properties or esthetics (opaque alumina core) • Incapability of being etched • Slip casting is a complex technique • Considerable reduction of tooth surface
  71. 71. All Ceramics – Dr. Nithin Mathew IN-CERAM SPINELL • Introduced due to the comparatively high opacity of the alumina core. • Incorporating magnesium aluminate (Mg A12O4) results in improved optical properties characterized by • Increased translucency • About 25% reduction in flexural strength • Spinel or Magnesium aluminate (Mg A12O4) is a composition containing A12O3 and Mg2O. 75
  72. 72. All Ceramics – Dr. Nithin Mathew DisadvantagesAdvantages • Spinel renders greater strength characteristics. • Spinell has extended uses (Inlay / Onlay, ceramic core material and Veneers.) 76 • Incapable to be etched by HF • 25% reduction in flexural strength.
  73. 73. All Ceramics – Dr. Nithin Mathew IN-CERAM ZIRCONIA • A mixture of zirconium oxide / aluminium oxide is used as a framework material,. • Physical properties were improved without altering the proven working procedure. • The final core of ICZ consists of • 30 wt% zirconia • 70 wt% alumina. 77
  74. 74. All Ceramics – Dr. Nithin Mathew DisadvantagesAdvantages • High flexural strength • 1.4 times the stability • 2-3 times impact capacity compared to ln-Ceram Alumina • Excellent Marginal Accuracy • Biocompatibility 78 • Poor esthetics due to increased opacity • Inability to etch
  75. 75. All Ceramics – Dr. Nithin Mathew 79 CASTABLE CERAMICS
  76. 76. All Ceramics – Dr. Nithin Mathew • Introduced by Mc Culloch in 1968 • Di-Cor • New types • Cera pearl • Canasite glass ceramic • Optimal pressable ceramic • Olympus castable ceramics • Castable phosphate glass ceramic 80
  77. 77. All Ceramics – Dr. Nithin Mathew • Supplied as ceramic ingots • Fabricated using Lost Wax technique and Centrifugal casting technique • Steps: • Wax pattern – invested • Dewaxing • Molten glass cast into mould using centrifugal casting machine • Glass core : ceramming (heat treatment process) • Microscopic plate-like crystals grow within the glass matrix • Veneeredusing feldspathic ceramics : Dicor Plus 81
  78. 78. All Ceramics – Dr. Nithin Mathew DI-COR (Dentsply + Corning Glass Co) • First commercially available castable ceramic material. • Non porous, non homogenous, microstructure with uniform crystal size which is derived from the controlled growth of crystals within an amorphous matrix of glass. • Dicor composed of: • Tetrasilicicfluormica crystals : 55 % • Glass ceramic : 45 % 82
  79. 79. All Ceramics – Dr. Nithin Mathew 83 Major Ingredients Minor Ingredients • SiO2 : 45-70% • K2O : upto 20% • MgO : 13-30% • MgF2 (nucleating agent) • A12O3 : upto 2% (durability & hardness) • ZrO2 : upto 7% • Fluorescing agents (esthetics) • BaO : 1 to 4% (radiopacity) Supplied as : • Special Dicor casting crucibles, 4.1 gm Dicor glass ingot • Dicor shading porcelain kit.
  80. 80. All Ceramics – Dr. Nithin Mathew PROPERTIES • Flexural strength : 81 ± 6.8 Mpa • Strength : 440-505 KHN • Biocompatible • Less bacterial counts : smooth surface, low surface tension, fluoride content. 84
  81. 81. All Ceramics – Dr. Nithin Mathew PROPERTIES Esthetics : • Gross man and Adiar • Hue and chroma of metal ceramics and Castable ceramics matched natural teeth. • Value of only Castable ceramics matched natural teeth. • Presence of mica crystals scatter light similar to enamel rods. • Chameleon effect i.e. the restoration acquires a part of the color from adjacent teeth and fillings as well as the underlying cement lute. 85
  82. 82. All Ceramics – Dr. Nithin Mathew PROPERTIES Cementation : • Zinc phosphate, light activated urethane resin • Etching with ammonium difluoride for 2 min (Bailey & Bennet 1988) Survival rate : • Kenneth et al 1999 - 14yr study • Crowns : 82% • Cores : 100% • Inlay and onlay : 90% • Partial coverage : 92% • Expenstein et al 2000 : Posterior 70%, anterior 82.7% 86
  83. 83. All Ceramics – Dr. Nithin Mathew DisadvantagesAdvantages • Chemical and physical uniformity. • Excellent marginal adaptation • Compatibility with lost-wax casting process. • Ease of adjustment • Low thermal conductivity • Radiographic density is similar to that of enamel 87 • Requires special equipments • Veneers failure rate as high as 8% • Must be stained with low fusing feldspathic porcelain
  84. 84. All Ceramics – Dr. Nithin Mathew CASTABLE APATITE GLASS CERAMIC (CERAPEARL) • 1985 -Sumiya Hobo & Iwata • Available as Cera Pearl • Crystalline microstructure similar to natural enamel • Mechanical properties superior to enamel 88
  85. 85. All Ceramics – Dr. Nithin Mathew Composition • CaO : 45% - reacts with P2O5 • P2O5 : 15% - Aids in glass formation • SiO2 : 35% - Forms the glass matrix. • MgO : 5% - Decreases the viscosity (anti flux) • Other : Trace elements (Nucleating agents during ceramming) 89
  86. 86. All Ceramics – Dr. Nithin Mathew CHEMISTRY 90 CaPO4 1460°C – 1510°C Amorphous Mass 750°C – 870°C Crystalline Oxyapatite Exposed to moisture Hydroxy Apatite Ceramming Ceramming : The ceramming oven is preheated at 750°C for 15 minutes. After the cast glass ceramic is placed in the oven the temperature is raised at the rate 500C / min until it reaches 870°C and held for 1 hr. External staining : Cerastain ( Bioceram )
  87. 87. All Ceramics – Dr. Nithin Mathew PROPERTIES • Cerapearl is similar to natural enamel in Composition • Density : 2.97 gm/cm2 • Refractive index : 1.66 • Thermal conductivity : 0.002 • Hardness : 343 • Clinical success : (crowns) 2 year success rate –100% 91
  88. 88. All Ceramics – Dr. Nithin Mathew 92 PRESSABLE CERAMICS
  89. 89. All Ceramics – Dr. Nithin Mathew • Supplied as ceramic ingots • Fabricated using Lost Wax technique and heat pressed into the mould • Steps: • Wax pattern – invested in phosphate bonded investment • Placed in specialized mould with alumina plunger • After burnout, ceramic ingot is placed under plunger and heated to 11500C • Veneeredusing feldspathic ceramics 93
  90. 90. All Ceramics – Dr. Nithin Mathew CLASSIFICATION • Shrink free ceramics • Cerestore • Al-ceram • Leucite reinforced glass ceramics • IPS empress • Optec/OPC • Lithia reinforced glass ceramic • IPS empress 2 • OPC 3G 94
  91. 91. All Ceramics – Dr. Nithin Mathew CERESTORE (Shrink Free Ceramics) • Consists of Al2O3 and MgO mixed with Barium glass frits. • On firing crystalline transformation produces Magnesium aluminate spinel, which occupies a greater volume than the original mixed oxides compensates for the conventional firing shrinkage. 95
  92. 92. All Ceramics – Dr. Nithin Mathew • Unfired Cerestore core : • Al2O3 • MgO • Glass frit • Silicone resin • Fillers 96 • Fired Cerestore core : • α- Al2O3 (Corrundum) • MgAl2O4 (Spinel) • Ba Mg2Al3 (Si9Al2O3) – Barium osumilite
  93. 93. All Ceramics – Dr. Nithin Mathew Chemical And Crystalline Transformation • Silicone Resin SiO SiO2 Alumina Aluminosilicate (160-8000C) (900-13000C) • Al2O3 + MgO MgAl2O4 (decreased shrinkage ) 97
  94. 94. All Ceramics – Dr. Nithin Mathew PROPERTIES • Flexural strength : 225 Mpa • Fit : exceptional fit because of direct moulding process. • Low thermal conductivity • Radiodensity similar to enamel • Biocompatible 98
  95. 95. All Ceramics – Dr. Nithin Mathew Advantages • Dimensional stability of the core material in the molded (unfired) and fired states • Better accuracy of fit and marginal integrity • Esthetics • Biocompatible (inert) and resistant to plaque formation (glazed surface) • Radio density similar to that of enamel • Low thermal conductivity; thus reduced thermal sensitivity • Low coefficient of thermal expansion and high modulus of elasticity results in protection of cement seal 99
  96. 96. All Ceramics – Dr. Nithin Mathew Disadvantages • Complex • Specialized laboratory equipment and cost • Inadequate flexural strength compared to the metal-ceramic restorations • Poor abrasion resistance, hence not recommended in patients with heavy bruxism or inadequate clearance • LIMITATIONS and high clinical failure rates of the Cerestore led to the withdrawal of this product from the market. • Improved version : 70 to 90% higher flexural strength - marketed as Al Ceram. 100
  97. 97. All Ceramics – Dr. Nithin Mathew IPS-EMPRESS • Hot pressed ceramics • 2 types: • Leucite reinforced (K2O – Al2O3 – 4 SiO2) • Lithium Disilicate reinforced (SiO2 – LiO2 – P2O5 – ZrO2) 101
  98. 98. All Ceramics – Dr. Nithin Mathew COMPOSITION • Pre cerammed, pre colored : INGOTS • SiO2 : 63% • Al2O3 : 17.7% • K2O : 11.2% • Na2O : 4.6% • B2O3 : 0.6% • CaO : 1.6% • BaO : 1.6% • TiO2 : 0.2% • Contains higher concentration of leucite crystals, which increases the resistance to crack propagation 102 Leucite content Conventional Porcelain Dicor IPS Empress Pressable ceramic 30-35% 50-60% 80-85%
  99. 99. All Ceramics – Dr. Nithin Mathew FABRICATION Lost-wax technique: • Wax pattern is invested • Burnout (at 850°C) • The ceramic ingot plunger and the entire assembly is preheated to 11000C • After 20 minute holding time the plunger presses the ceramic under vacuum (0.3-0.4 MPa) into the mould • Held under pneumatic pressure (45-mins) to allow complete and accurate fill of the mould. 103
  100. 100. All Ceramics – Dr. Nithin Mathew PROPERTIES • Flexural strength : 160-180 Mpa • The increase in strength has been attributed to : • Pressing step which increases the density of leucite crystals • Subsequent heat treatments which initiate growth of additional leucite crystals • Esthetics : High esthetic value (translucent, fluorescent) • Clinical survival : 95% survival rate of 2-4 years (Deniz G et al 2002) • Marginal adaptation : Better marginal adaptation compared to aluminous core material. 104
  101. 101. All Ceramics – Dr. Nithin Mathew Advantages • Lack of metal or an opaque ceramic core • Moderate flexural strength (160-180 MPa) • Excellent fit (low-shrinkage ceramic) • Improved esthetics (translucent, fluorescent) • Etch-able • Less susceptible to fatigue and stress failure • Less abrasive to opposing tooth • Biocompatible material 105
  102. 102. All Ceramics – Dr. Nithin Mathew Disadvantages • Potential to fracture in posterior areas. • Special laboratory equipment such as pressing oven and die material (expensive) • Inability to cover the color of a darkened tooth preparation or post and core, since the crowns are relatively translucent. • Compressive strength and flexural strength lesser than metal-ceramic or glass-infiltrated (In- Ceram) crowns. 106
  103. 103. All Ceramics – Dr. Nithin Mathew IPS EMPRESS 2 (IVOCLAR) • Second generation of pressable materials for all- ceramic bridges. • Lithium disilicate crystal >60vol%. • The apatite crystals are layered which improved optical properties (translucency, light scattering) which contribute to the unique chameleon effect. 107 IPS Empress IPS Empress 2 Flexural strength Upto 150 MPa > 400 Mpa
  104. 104. All Ceramics – Dr. Nithin Mathew • Other applications : • Core build-up system with the pre-fabricated zircon oxide root canal posts Advantages • High biocompatibility • Excellent fracture resistance • High radiopacity • Outstanding translucency 108
  105. 105. All Ceramics – Dr. Nithin Mathew IPS E.MAX PRESS • Introduced in 2005. • Considered as an enhanced lithium disilicate press-ceramic material when compared to Empress II. • Better physical properties and improved esthetics 109
  106. 106. All Ceramics – Dr. Nithin Mathew Strength 110
  107. 107. All Ceramics – Dr. Nithin Mathew MACHINABLE CERAMICS
  108. 108. All Ceramics – Dr. Nithin Mathew Impression Casts & Die Wax Pattern Investing Casting Lost Wax Technique Camera Contact Digitizer Laser Machine Sinter Computerised Design CAD / CAM System Traditional Technique Higher Technology Data Acquisition Restoration Design Restoration Fabrication Electrical Discharge Machine
  109. 109. All Ceramics – Dr. Nithin Mathew • Application of CAD/ CAM techniques was actively pursued by three groups of researches • Group supported by Henson International of France. • Combined group effort between the University of Zurich and Brains, Brandestini Instruments of Switzerland. • University of Minnesota, supported by the U.S. National Institute of Dental Research. 113
  110. 110. All Ceramics – Dr. Nithin Mathew FRENCH SYSTEM • Optical impression – Laser scanner • Data processing – By Shape recognition software • It has a library (memory) describing theoretical teeth. • The system uses: • 3-D probe system based on electro-optical method • Surface modelling and screen display • Automatic milling by a numerically controlled 4-axis machine 114
  111. 111. All Ceramics – Dr. Nithin Mathew SWISS SYSTEM • Optical impression - Optical topographic scanning using a 3-D oral camera • Data processing - By an interactive CAD unit • The system uses: • A desk top model computer • Display monitor permitting visual verification of quality of data being acquired • Electronically controlled 3-axis milling machine 115
  112. 112. All Ceramics – Dr. Nithin Mathew MINNESOTA SYSTEM • Optical impression - Photograph based system using a 35-mm camera with magnifying lens. • Data processing - Data obtained in the dental office is sent to another location for processing and machining. • 3-D Reconstruction uses : • Direct line transformation and an alternative technique proposed by Grimson • Milling with a 5-axis milling machine 116
  113. 113. All Ceramics – Dr. Nithin Mathew CLASSIFICATION - Machinable Ceramics 117 ANALOGOUS SYSTEM DIGITAL SYSTEMS I. Direct II. Indirect i. 3-D scanning ii. CAD modelling iii. Fabrication I. Copy milling i. Fabrication of prototype for scanning ii. Copying and reproduction by milling II. Erosive techniques i. Sono Erosion ii. Spark Erosion
  114. 114. All Ceramics – Dr. Nithin Mathew FINE SCALE FELDSPATHIC PORCELAIN I. CEREC VITABLOC MARK I: • Feldspathic porcelain • Larger particle size (10-50 micron) II. CEREC VITABLOC MARK II: • Feldspathic porcelain reinforced with aluminium oxide (20-30%) • Fine grain size (4 micron) GLASS PORCELAIN I. DICOR Flurosilica Mica Crystals Plates (2 microns) II. MGC F Tetrasilica mica (enhance fluorescence, machinability) III. PRO CAD Leucite - Reinforced Glass Ceramic (high strength) 118 • 2 Classes of Machinable Ceramics
  115. 115. All Ceramics – Dr. Nithin Mathew DIGITAL SYSTEMS CAD-CAM: • Uses digital information about the tooth preparation or a pattern of the restoration to provide a computer-aided design (CAD) on the video monitor for inspection and modification. • The image is the reference for designing a restoration on the video monitor. • Once the 3-D image for the restoration design is accepted, the computer translates the image into a set of instructions to guide a milling tool [CAM] in cutting the restoration from a block of material. 119
  116. 116. All Ceramics – Dr. Nithin Mathew STAGES OF FABRICATION All systems ideally involve 5 basic stages: 1. Computerized surface digitization 2. Computer - aided design 3. Computer - assisted manufacturing 4. Computer - aided esthetics 5. Computer - aided finishing • The last two stages are more complex and are still being developed for including in commercial systems. 120
  117. 117. All Ceramics – Dr. Nithin Mathew Scanning 3D Miniature Camera • Microprocessor unit stores the pattern • Video display serves as a format for manual construction • Final 3-D restoration is developed from above again by microprocessor CAD-CAM Procedure (10-15mins)
  118. 118. All Ceramics – Dr. Nithin Mathew • Electronic information is transferred to miniature multiple axis milling device • Milling device generates a precision fitting restoration from a standard ceramic block
  119. 119. All Ceramics – Dr. Nithin Mathew CEREC SYSTEM • Brains. A. G, Switzerland in 1980 • Manufactured in West Germany, Siemens group • Consists of: • 3-D video camera (scan head) • Electronic image processor with memory unit • Digital processor • Miniature Milling machine 123
  120. 120. All Ceramics – Dr. Nithin Mathew DisadvantagesAdvantages • Translucency and color of porcelain very closely to natural dental tissues • Quality of ceramic is not changed during processing • Can be placed in one visit • Prefabricated ceramic is wear resistant 124 • Occlusal anatomy to be developed • Inaccuracies in fit • Poor esthetics systems
  121. 121. All Ceramics – Dr. Nithin Mathew CEREC 2 SYSTEM • Morman & Brandestini in 1994 • Constant further development • Major changes include: • Enlargement of grinding unit from 3 to 6 axes • Sophisticated software technology : occlusal surfaces • Minor technical innovations: • Magnification factor increased from 8x to 12x • Improved grinding precision by 24 times • Improved accuracy of fit 125
  122. 122. All Ceramics – Dr. Nithin Mathew CEREC 3 SYSTEM • Operator can record multiple images in seconds • Creates a virtual cast for entire quadrant 126
  123. 123. All Ceramics – Dr. Nithin Mathew OTHER DIGITAL SYSTEMS • DURET SYSTEM • Francois Duret : produced by Sopha (France) • CICERO SYSTEM • COMET SYSTEM 127
  124. 124. All Ceramics – Dr. Nithin Mathew ADVANTAGES : Machinable Ceramics • Single visit • Good patient acceptance • Eliminates procedures like impression model making and fabrication of temporary prosthesis • Void free porcelains without firing shrinkage • Better adaptation • Inlay,onlay can be fabricated chair side • Eliminates asepsis • Since its computer assisted crowns of correct dimensions can be obtained • Glazing is not required : can be polished • Less abrasion of tooth structure : homogenous material 128
  125. 125. All Ceramics – Dr. Nithin Mathew DISADVANTAGES : Machinable Ceramics • Limitations in fabrication of multiple units • Inability to characterize shades and translucency • Inability to image in wet environment • Techniquesensitive • Expensive • Limited availability 129
  126. 126. All Ceramics – Dr. Nithin Mathew ANALOGUS SYSTEMS : COPY MILLING CELAY SYSTEM • Switzerland in 1992 • High precision manually operated • Key duplication • Advantage : Recreation of all surfaces. 130 COPYING SIDE • Various size probes represent size of diff milling burs is run over surface of pattern MILLING SIDE • At same time matched rotary instru-mills same shape out of restorative block
  127. 127. All Ceramics – Dr. Nithin Mathew ANALOGUS SYSTEMS : EROSIVE TECHNIQUES SONO EROSION: • Based on ultrasonic methods. • The ceramic blank is surrounded by an abrasive suspension of hard particles, such as boron carbide, which are accelerated by ultrasonics, and thus erode the restoration out of the ceramic blank. 131
  128. 128. All Ceramics – Dr. Nithin Mathew ANALOGUS SYSTEMS : EROSIVE TECHNIQUES SPARK EROSION: • 'Electrical Discharge Machining' (EDM) • Metal removal process using a series of sparks to erode material from a workpiece in a liquid medium under carefully controlled conditions. • Liquid medium : light oil called the dielectric fluid. 132
  129. 129. All Ceramics – Dr. Nithin Mathew CERCON & LAVA ZIRCONIA CORE CERAMICS 133 • Fabrication Tooth preparation Impression made Wax pattern made on model Anchored on to the Cercon Brain Presintered zirconia blank attached on other side of brain unit Unit activated Pattern scanned Milled prosthesis then removed from unit and placed in the cercon furnace (13500C for 6 hrs) Trimming Finished ceramic core framework Veneering
  130. 130. All Ceramics – Dr. Nithin Mathew BONDING OF PORCELAINS RESIN–CERAMIC BONDING • Function of the silane primer between porcelain and the composite resin plays an important role. • Etching of ceramic surface with 7.5 to 10% hydrofluoric acid for 2-10mins and then followed by silanization increased the bond strength to porcelain (Peremuter and Montagonon, 1981) 134
  131. 131. All Ceramics – Dr. Nithin Mathew METAL-CERAMIC BONDING 1. Chemical bonding across the metal-porcelain interface: • Diffusion between surface oxide on the alloy and ceramic 2. Mechanical interlocking: • Due to surface irregularity of the alloy • Air abrasion with aluminium oxide particles 3. Residual compressive stresses: • Core has slightly higher CTE than porcelain • Porcelain draws towards the coping on cooling : residual compressive forces 135
  132. 132. All Ceramics – Dr. Nithin Mathew REPAIR OF CERAMIC RESTORATIONS 1. PORCELAIN REPAIR : • Fracture is totally in porcelain • Simplest repair • Preparation of porcelain surface by bonding : • Surface roughening by using diamond burs, air abrasion and acid etching with 9.5% HF acid • Application of silane coupling agent & allowed to dry for 1 min. • Application of bonding agent • Shade matched composite 136
  133. 133. All Ceramics – Dr. Nithin Mathew 2. MIXED (PORCELAIN/METAL ) REPAIR : • Involves exposed metal • More complicated • If remaining porcelain: • Adequate : exposed metal and remaining porcelain is veneered with composite opaquer & subsequently with layers of shade matched composite. • Inadequate : exposed metal surface is used as an adhesive substrate after preparation for bonding with composite opaquer layer followed by shade matched composite. 137
  134. 134. All Ceramics – Dr. Nithin Mathew 3. METALREPAIR: • Involves the exposed metal with or no remaining porcelain • Most difficult • 2 methods : • Veneering exposed metal surface with direct bonding of shade matched composite after preparation of exposed metal surface for bonding. • Fabrication of an over casting: small areas of remaining porcelain are removed if present. Crown / pontic is reduced circumferentially to provide room for both porcelain and metal, & provide margin for the laboratory technician and a thin metal overcasting with fused porcelain veneer is fabricated. 138
  135. 135. All Ceramics – Dr. Nithin Mathew OTHER APPLICATIONS OF CERAMICS • ALL CERAMIC POST & CORES DRAWBACKS of conventional Metal Post & Core • Decrease depth of translucency of restoration • Shine through in cervical root, altering appearance of thin gingival tissue • Corrosion products 139
  136. 136. All Ceramics – Dr. Nithin Mathew ADVANTAGES of All-ceramic Post & Core • All ceramic restoration transmits certain percentage of incident light to ceramic core & post . • Color of final restoration will be derived from an internal shade • Depth of translucency in cervical root area • Biocompatible MATERIALS USED • In–ceram • Dense – sintered alumina ceramic • Zirconium oxide ceramics 140
  137. 137. All Ceramics – Dr. Nithin Mathew CERAMIC-DENTAL IMPLANTS • Ceramic oxides : resistant to corrosion • Tissue grow into surface porosity • Ceramic Coating for Implant • Bioactive Ceramics : High density Alumina, TriCalcium Phosphate, High Alumina polymer composite • Inert Ceramics : Alumina, Zirconium Oxide 141
  138. 138. All Ceramics – Dr. Nithin Mathew CERAMIC INSERTS • Megafillers for direct posterior composite restorations • Reduce bulk of composite resin • Decrease shrinkage • Minimize wear Composition • Glass inserts • Lithium – alumino-silicate glass (heat treated & silanated) eg: Beta –Quartz Glass –ceramic inserts 142
  139. 139. All Ceramics – Dr. Nithin Mathew CEROMERS • Ceramics + Polymers = Ceromers • Ceramics: • Abrasion resistance • High stability • Esthetics • Composites • Ease of final adjustments • Excellent polishability • Bonding with luting cement • Possibility of repair 143
  140. 140. All Ceramics – Dr. Nithin Mathew ZIRCONIA IMPLANTS • A radical new solution to immediate dental implant placement. • Patient’s extracted tooth is laser scanned and modified in CAD software • Machined out of zirconium • Implanted in the still healing socket • Provides incredibly natural looking results. 144
  141. 141. All Ceramics – Dr. Nithin Mathew 145
  142. 142. All Ceramics – Dr. Nithin Mathew • An increase of the crystalline content as seen in the pressable materials and the fully sintered zirconia generally corresponds to an improvement of the mechanical properties. • An increase of crystalline content of a glass–ceramic is accompanied with an increase of the strength and fracture toughness. 146 Strength, Fracture Toughness and Microstructure of a Selection of All-Ceramic Materials. Part I. Pressable and Alumina Glass-Infiltrated Ceramics Part II. Zirconia-based dental ceramics Guazzatoa, Mohammad Albakrya, Simon P. Ringerb, Michael V. Swain Dental Materials (2004) 20, 441–448
  143. 143. All Ceramics – Dr. Nithin Mathew • Vita Inceram crowns exhibited significantly higher fracture strength than conventional all- ceramic crowns. 147 An Evaluation of Two Modern All-Ceramic Crowns and their comparison with Metal Ceramic Crowns in terms of the Translucency and Fracture Strength Girish Nazirkar, Suresh Meshram International Journal Of Dental Clinics 2011:3(1):5-7
  144. 144. All Ceramics – Dr. Nithin Mathew • The fracture strength of monolithic high translucent zirconia crown is considerably higher than that of porcelain-veneered zirconia crown cores, porcelain-veneered high translucent zirconia crown cores and monolithic lithium disilicate crowns. 148 Fracture strength of monolithic all-ceramic crowns made of high translucent yttrium oxide-stabilized zirconium dioxide compared to porcelain-veneered crowns and lithium disilicate crowns Camilla Johansson, Gratiela Kmet, Johnny Rivera, Christel Larsson & Per Vult Von Steyern Acta Odontologica Scandinavica 2014; 72: 145-153
  145. 145. All Ceramics – Dr. Nithin Mathew • Lithium Disilicate glass-ceramic restorations had higher fracture resistances than leucite reinforced glass-ceramic restorations. 149 Dynamic fatigue and fracture resistance of non-retentive all-ceramic full-coverage molar restorations. Influence of ceramic material and preparation design Jan-Ole Clausen, Milia Abou Tara∗, Matthias Kern Dental Materials 26 (2010) 533–538
  146. 146. All Ceramics – Dr. Nithin Mathew • Observations regarding zirconia-based all ceramic restorations compared with PFM restorations: • Better esthetically than typical PFM restorations • Long-term color stability probably will be the same as that with PFM restorations • Margins of the restorations have a more acceptable appearance than those of PFM. • Strength and service record of PFM restorations and zirconia based restorations in three-unit prostheses is similar. • Gingival sensitivity to metal will be reduced or eliminated with use of zirconia-based. 150 Choosing an all-ceramic restorative material Porcelain-fused-to-metal or zirconia-based? Gordon J. Christensen JADA, Vol. 138; May 2007
  147. 147. All Ceramics – Dr. Nithin Mathew SELECTION OF CERAMIC MATERIALS • Four broad categories or types of ceramic systems:  Category 1: Powder/liquid feldspathic porcelains  Category 2: Pressed or machined glass-ceramics  Category 3: High-strength crystalline ceramics  Category 4: Metal ceramics 151 Ceramics: Rationale for material selection, Cosmetic Dentistry:2,2013
  148. 148. All Ceramics – Dr. Nithin Mathew 152 Clinical Parameters To Evaluate : • Individual teeth evaluated for specific material selection • Assessing four environmental conditions in which the restoration will function 1. Substrate 2. Flexure risk assessment 3. Excessive shear and tensile stress risk assessment 4. Bond/seal maintenance risk assessment Ceramics: Rationale for material selection, Cosmetic Dentistry:2,2013
  149. 149. All Ceramics – Dr. Nithin Mathew 153 1. Substrate • Is it enamel? • How much of the bonded surface will be enamel? • How much enamel is on the tooth? • How much of the bonded surface will be dentine? • What type of dentine will the restoration be bonded to? Is it a restorative material (e.g. composite, alloy)? • High bond strength : Enamel • Dentine surfaces/composite : Less predictable • More stress - between dentine and composite - more damage to the restoration and underlying tooth structure
  150. 150. All Ceramics – Dr. Nithin Mathew 154 2. Flexure risk assessment • Each tooth and existing restorations are evaluated for signs of past overt tooth flexure. • Signs • Excessive enamel crazing • Tooth and restoration wear • Tooth and restoration fracture • Micro-leakage at restoration margins • Recession • Abfraction lesions
  151. 151. All Ceramics – Dr. Nithin Mathew 155 2. Flexure risk assessment • Low risk • Low wear; minimal to no fractures or lesions • Patient’s oral condition is reasonably healthy • Medium risk • Signs of occlusal trauma • Mild to moderate gingival recession along with inflammation • Bonding mostly to enamel is still possible • There are no excessive fractures
  152. 152. All Ceramics – Dr. Nithin Mathew 156 2. Flexure risk assessment • High risk • Evidence of occlusal trauma from parafunction; • More than 50 % of dentine exposure exists • Significant loss of enamel due to wear of 50 % or more • Porcelain must be built up by more than 2 mm.
  153. 153. All Ceramics – Dr. Nithin Mathew 157 3. Excessive shear and tensile stress risk assessment • All types of ceramics (especially porcelains) are weak in tensile and shear stresses. • Ceramic materials perform best under compressive stress • If a high-stress field is anticipated : Stronger and tougher ceramics are needed • The substructure should reinforce the veneering porcelain by utilising the reinforced- porcelain system technique
  154. 154. All Ceramics – Dr. Nithin Mathew 158 4. Bond/seal maintenance risk assessment • Glass-matrix materials : powder/liquid porcelains and pressed or machined glass-ceramics, require maintenance of the bond and seal for clinical durability. • If the bond and seal cannot be maintained, then high-strength ceramics or metal ceramics are the most suitable, since these materials can be placed using conventional cementation techniques.
  155. 155. All Ceramics – Dr. Nithin Mathew 159 4. Bond/seal maintenance risk assessment • Clinical situations in which the risk of bond failure is higher are • Moisture control problems • Higher shear and tensile stresses on bonded interfaces • Variable bonding interfaces (different types of dentine) • Material and technique selection of bonding • The experience of the operator
  156. 156. All Ceramics – Dr. Nithin Mathew 160 Category 1: Powder/Liquid Feldspathic Porcelains Aesthetic Factors • 0.2–0.3 mm is required for each shade change Substrate Condition • 50 % or more remaining enamel on the tooth • 50 % or more of the bonded substrate is enamel • 70 % or more of the margin is in enamel Flexure risk assessment • Higher risk and more guarded prognosis when bonding to dentine • Increased enamel, prognosis improved • Depending on the dentine/enamel ratio, the risk : low to moderate Tensile and shear stress risk assessment • Low to low/moderate risk. • Large areas of unsupported porcelain, deep overbite or overlap of teeth, bonding to more-flexible substrates : Increase the risk of exposure to shear and tensile stresses Bond/seal maintenance risk assessment • Absolute low risk of bond/seal failure Indications • Indicated for anterior teeth
  157. 157. All Ceramics – Dr. Nithin Mathew 161 Category 2: Pressed or Machined Glass-ceramics Aesthetic Factors • Minimum working thickness of 0.8 mm • 0.2–0.3 mm for each shade change is required Substrate Condition • Less than 50 % of the enamel on the tooth • Less than 50 % of the bonded substrate is enamel • 30 % or more of the margin is in dentine Flexure risk assessment • Risk is medium for Empress, VITABLOCS Mark II and Authentic-type glass-ceramics and layered IPS e.max Tensile and shear stress risk assessment • Flexure risk is medium to high (and full crown preparation is not desirable) • Monolithic IPS e.max has been 100 % successful for as long as 30 months in service. Bond/seal maintenance risk assessment • Risk is medium for Empress, VITABLOCS Mark II and Authentic-type glass-ceramics, and layered IPS e.max. • Medium to medium/high for bonded monolithic IPS e.max Indications • Thicker veneers, anterior crowns, and posterior inlay and onlays • Only indicated in clinical situations in which long-term bond and seal can be maintained.
  158. 158. All Ceramics – Dr. Nithin Mathew 162 Category 3: High-strength Crystalline Ceramics Aesthetic Factors • Minimum working thickness of 1.2 mm is required. Substrate Condition • Substrate is not critical, since a high-strength core supports veneering material. Flexure risk assessment • Risk is high or low • For high-risk situations, core design and structural support for porcelain become more critical Tensile and shear stress risk assessment • Risk is high or low • High-risk situations : Preparations should allow for a 0.5 mm core plus 1 mm of porcelain • Anteriors: There should not be more than 2 mm of unsupported incisal porcelain. • Molars : Better to use zirconia cores rather than alumina cores • High risk molar : Full-contour zirconia restorations recommended. Bond/seal maintenance risk assessment • If the risk of obtaining or losing the bond or seal is high, then zirconia is the ideal all-ceramic to use. Indications • When significant tooth structure is missing • Unfavourable risk for flexure and stress distribution is present • It is impossible to obtain and maintain bond and seal
  159. 159. All Ceramics – Dr. Nithin Mathew 163 Category 4: Metal ceramics Aesthetic Factors • 1.5–1.7 mm is required for maximum aesthetics Substrate Condition • Substrate is not as critical, since the metal core supports the veneering material. Flexure risk assessment • Risk is high or low • For high-risk situations, core design and structural support for porcelain become more critical Tensile and shear stress risk assessment • Risk is high or low • For high-risk situations, core design and structural support for porcelain become more critical Bond/seal maintenance risk assessment • If the risk of obtaining or losing the bond or seal is high, then metal ceramics are an ideal choice for a full-crown restoration. Indications • Indicated in all full-crown situations, esp when all risk factors are high.
  160. 160. All Ceramics – Dr. Nithin Mathew CONCLUSION • Dental ceramic technology is one of the fastest growing areas of dental material research and development. The past decades have seen the development of several new groups of ceramics. • Each system has its own merits, but may also have shortcomings. • Combinations of materials and techniques are beginning to emerge which aim to exploit the best features of each. • Glass-ceramic and glass-infiltrated alumina blocks for CAD-CAM restoration production are examples of these. • The diversity and sophistication of the CAD-CAM systems may prove to be influential in the future. 164
  161. 161. All Ceramics – Dr. Nithin Mathew REFERENCES • Philips science of dental materials - Anusavice • Craig’s restorative materials • Dental materials & their selection - William ’O’ Brien • Clinical operative dentistry - principles and practice - Ramya Raghu • Textbookof Dental materials – Mahalekshmi • Theory and practice of fixed prosthodontics - Tylmann 166
  162. 162. All Ceramics – Dr. Nithin Mathew 167

×