Castable ceramics/ dentistry training


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Castable ceramics/ dentistry training

  1. 1. CASTABLE CERAMICS INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2. Glass-ceramics are polycrystalline materials developed for application by casting procedures using the lost wax technique, hence referred to as “castable ceramic”. Glass ceramics in general are partially crystallized glass and show properties of both crystalline and amorphous (glassy) materials. They are fabricated in the vitreous (Glass or non- crystalline/amorphous) state and converted to a ceramic (crystalline state) by controlled crystallization using nucleating agents during heat treatment.
  3. 3. History of evolution of glass ceramics: 1837 – Murphy was probably the first dentist to melt glass onto a platinum sheet that had been fit in the cavity preparation. 1891 – Herbst made glass restoration out of pulverized coloured glass particles with a gas flame directly on the plaster model. 1930 – Frederick Carder, the founder of Steuben division of the Corning Glass Works perfected fabricating 3- dimensional glass articles for decorative purposes using the lost wax technique. Although delicate objects were cast accurately, the mechanical properties of glass restricted its use to artistic application.
  4. 4. 1957 – S.D. Stookey from the Corning Glass Works observed how an industrial impure glass changed into ceramic with organic crystalline form and coined the term “Glass-ceramic”. Thus ‘Pyroceram’ an industrial glass ceramic which had the properties of both glass and ceramics was developed. 1968 W.T. MacCulloch realised the usefulness of glass ceramics and proposed its use for dental restorative purposes (denture teeth; crowns; inlays). He used a continous glass molding process to produce denture teeth, and suggested fabrication of crowns/ inlays by centrifugal casting of molten glass. 1973- Dr. David Grossman developed and patented the MaCor (Machninable Corning), a predecessor of Dicor (Grossman D.G.).
  5. 5. Since 1978 – Peter Adair of Biocor Inc, in association with the Corning Glass Works and Dentsply international, researched and developed the clinical application of glass- ceramics. 1984 – Peter Adair patented Dicor, the commercial glass ceramic material. 1985 – Sumiyo Hobo & Iwata developed a castable apatite glass ceramic Cerapearl. 1986 – The world wide patent for the castable glass-ceramic material and its entire processing system was given to the manufacturing company De Trey/ Corning ware. 1988 – Tamura reported on fabrication of hydroxyapatite crowns.
  6. 6. Glass-ceramic systems for dental application: Li2 O ZnO – SiO2 Li2 O - Si2 O Li2 O – CaO - Al2 O3 – SiO2 - Na2 O– K2 O– Cao – Mgo - Al2 O3 - P2 O5 - SiO3 – F CaO P2 O5 CaO – MgO - P2 O5 – SiO2 R2 O – Mg - SiO2 – F
  7. 7. Most glass ceramics are opaque or cloudy and are not suitable for dental use. The first glass ceramic employed in dentistry was introduced by MacCulloch (1968) for the construction of denture teeth, and was based on the Li O2 - ZnO - SiO2 - systems. At that time, the use of acrylic denture teeth was becoming popular and the idea of glass ceramics was not exploited further. The exploration of glass-ceramic for dental use was taken up by other researchers and has resulted in at least two major commercially available products
  8. 8. Castable dental Glass-Ceramics Fluoromicas Apatite Glass-Ceramic OtherGlass-Ceramics (SiO2 K2 MgOA12 O3 ZrO2 (CaOMgOP2 O5 SiO2 system) Based on a) Lithia E.g Dicor E.g: Cera Pearl (Kyocera Bioceram) b)Calcium phosphate
  9. 9. Dicor: Dicor, the first commercially available castable glass-ceramic material for dental use was developed by The Corning Glass Works (Corning N.Y.) and marketed by Dentsply International (Yord, PA, U.S.A). The term “DICOR” is a combination of the manufacturer’s names: Dentsply International & Corning glass. Dicor is a castable polycrystalline fluorine containing tetrasilicic mica glass-ceramic material, initially cast as a glass by a lost-wax technique and subsequently heat - treated resulting in a controlled crystallization to produce a glass - ceramic material.
  10. 10. Composition of Dicor is based on the SiO2 K2 OmgOA12 O3 ZrO2 system. Its composition (w/w) according to different statements. Supplied as : Dicor castable ceramic cartridges- special DICOR casting crucibles each containing a 4.1 gm DICOR ingot and the Dicor shading porcelain kit. Equipment  DICOR Casting Machine  DICOR Ceramming Furnace with Ceramming Trays Major Ingredients Minor Ingredients SiO2 45-70%, K2 O upto 20%; MgO 13- 30% MgF2 (nucleating agent & flux 4 to 9%) A12 O3 upto 2% (durability & hardness) ZrO2 upto 7%; Fluorescing agents (esthetics) BaO 1 to 4% (radiopacity)
  11. 11. Fabrication of castable ceramics restoration consists of mainly 2 steps:  Casting: The glass liquefies at 1370°C to such a degree that it can be cast into a mold using lost-wax and centrifugal casting techniques. • The wax pattern of the proposed restoration made on the model/ die is invested in Castable Ceramic Investment (a carbon-free, phosphate-based investment, specially formulated to match DICOR castable ceramic) in a double-line casting ring and burned out in a conventional burnout at 900°C for 30 mins. • Glass ingots of castable ceramic material is placed in a special zirconia crucible (melted at 1360°C / 2600°F) and centrifugally cast .in the electronically-controlled DICOR Casting Machine (Dentsply Int), maintaining the spin pressure for upto 4 minutes and 30
  12. 12. • The transparent glass casting obtained is amorphous and fragile. After cooling, it is divested, sandblasted (25um Al2O3 particles at 40 psi) and carefully separated from the sprue.  Ceramming: The cast glass material is subject to a single-step heat treatment called as 'Ceramming' to produce controlled crystallization by internal nucleation and crystal growth of microscopic plate like mica crystals within the glass matrix. This procedure gives glass-ceramic the special physical and mechanical properties of DICOR. Method: The transparent fragile casting is embedded in castable ceramic embedment material (Gypsum-based) and placed in a Ceramming tray in the DICOR Ceramming Furnace.
  13. 13. Ceramming cycle: 650-1075 °C for 1 1/2hours and sustained upto 6 hours. The cerammed glass-ceramic casting is achromatic and appears as a whitish opaque semi-crystalline material; hence external colourants are required to develop the required shade (by veneering self - glazing, pre-mixed DICOR shading porcelain provided by the manufacturer).
  14. 14. The computer controlled ceramic process is adjusted so that the cast glass ceramic is composed of:  Tetrasilic flouromica crystals (crystalline) - 55% by volume.  Glass matrix (non-crystalline) - 45% by volume. The microstructure after ceramming consists of multiple interlocking small plate-like crystals of tetrasilicic flouromica (K2 Mg5 -Si4 O10 F2 ) approximately 1 µm thick and 5- 6mm in diameter. On the surface of the cerammed glass are ‘Enstatite crystals’ at a thickness of 15-50µ m, which occur through fluorine depletion (that occurs through interactions with the embedment material used for the ceramming process. The enstatite crystals are in an orthongnal direction to the surface and are whitish and opaque in
  15. 15. The crystals function in following ways:  Improved strength: Interlocking of randomly oriented small plate-like mica crystals increases the resistance to fracture. The mica crystals readily cleave along its long axis, causing cracks to deflect, branch or blunt; thus disrupting crack propagation. Strength also depends upon crystal diameter and crystal-glass expansion mismatches.  Improved esthetics - The varying crystal sizes and the difference in the refractive indices of the glass and crystalline phase makes the glass appear transparent. The refractive index of the mica crystals is matched to that of the surrounding glass phase thus reducing light scatter (as in aluminious porcelains) and results in transparency close to that of enamel. Reduced abrasive property - Since mica crystals replace the more abrasive leucite crystals found in traditional feldspathic
  16. 16. Following the ceramming process a “Ceram layer” or ‘skin’ of 25-100µm thickness is formed on the surface of the DICOR restoration. Contained within that ‘ceram layer’ is what has been described as crystal ‘whiskers’ oriented perpendicular to the external surface. According to the manufacturer’s laboratory manual, the ‘rod-like crystals that form on the surface of the casting during ceramming increase its opacity ’. Therefore, the outer ‘skin’ may or may not be removed following the ceramming process, depending on the level of translucency desired in the final restoration.
  17. 17. Therefore, a shaded Dicor restoration should be viewed as a non - homogenous material composed largely of the internal (parent) castable glass-ceramic veneered with a thick, hard cerammed “skin” covered with multiple layers of shading porcelain. DICOR components KHN KHN The Ceram layer 505 Dental porcelain After adding shading porcelain 447 460 Internal/parent Dicor glass- ceramic material located below the cerammed skin 369 Dental enamel 343
  18. 18. Chameleon effect of Dicor The transparent crystals scatter the incoming light. The light and also its color, is disbursed as if the light is bouncing off a large number of small mirrors that reflect the light and spread it over the entire glass-ceramic. This property is called the ‘chameleon effect’. This means Dicor glass – ceramics change color according to their surroundings, which enhances its esthetic properties. Dicor restoration surfaces were reported to have an appreciable decrease in plaque accumulation compared to that of natural teeth. Probable theories suggest the ability of Dicor surface to interfere with the bacterial adhesion to different proteins (plaque) normally found on natural teeth due to the following reasons :  It has a smooth non-porous surface  Presence of an electrical charge inhibiting plaque formation or fluoride in the chemical
  19. 19. Advantages of Dicor  Chemical and physical uniformity  Excellent marginal adaptation (fit)  Compatibility with lost-wax casting process  Uncomplicated fabrication from wax-up to casting, ceramming and colouring  Ease of adjustment
  20. 20.  Excellent esthetics resulting from natural translucency, light absorption, light refraction and natural colour for the restoration.  Relatively high strength (reported flexural strength of 152 MPa), surface hardness (abrasion resistance) and occlusal wear similar to enamel.  Inherent resistance to bacterial plaque and biocompatible with surrounding tissues.  Low thermal conductivity.  Radiographic density is similar to that of enamel.
  21. 21. Disadvantages  Requires special and expensive equipments such as Dicor casting machine, ceramming oven. (High investment cost for the lab)  Although short term clinical studies, verified the efficacy of the Dicor system in laboratory studies for use as veneers and inlays, failure rates as high as 8% (# of the restoration) were reported, especially in the posterior region. In addition, failure rates as high as 35% have been reported with full coverage Dicor crowns not bonded to tooth (The poor strength is thought to be caused by porosity, especially in the outermost "ceram layer").  Dicor must be shaded/ stained with low fusing feldspathic shading porcelain to achieve acceptable esthetics, however the entire stain/ colors maybe lost during occlusal adjustment (use of abrasives), during routine dental prophylaxis or through the use of acidulated fluoride gels.
  22. 22. Two ceramic products were introduced to overcome the above problem:  Dicor plus (Dentsply, Trubyte division) : Consists of a cast cerammed core (Dicor substrate) and shaded feldspathic porcelain veneer. However, as Dicor plus is a feldspathic porcelain that contains leucite, the abrasiveness is expected to be similar to other feldspathic porcelains.  Willis Glass : Consists of a Dicor cast cerammed core and a Vitadur-N porcelain veneer similar in nature to that used for Dicor Plus.
  23. 23. CASTABLE APATITE GLASS CERAMIC Castable apatite ceramic is classified as CaO-P2 O5 -MgO- SiO glass ceramic. 1985 -Sumiya Hobo & Iwata developed a castable apatite glass-ceramic which was commercially available as Cera Pearl (Kyocera Bioceram, Japan).
  24. 24. CERA PEARL (Kyocera San Diego, CA): contains a glass powder distributed in a vitreous or non-crystalline state. Composition: Approximately (By weight)  Calcium oxide (CaO) -45%  Phosphorus Pentoxide (P2 O5 ) -15% Aids in glass formation  Magnesium oxide (MgO) -5% Decreases the viscosity (antiflux)  Silicon dioxide (SiO2 ) -35% Forms the glass matrix.  Other -Trace elements Nucleating agents(during ceramming). Chemistry: Apatite glass-ceramic melts (1460°C) and flows like molten glass and when cast (1510°C) it has an amorphous microstructure.
  25. 25. Apatite Glass-Ceramic Molten glass CaPO4 (CaO-P2O5 -MgO-SiO2) (Amorphous) The amorphous CaPO4 formed after melting and casting changes into a crystalline oxyapatite on heat treatment (ceramming) at 870°C for 1 hour. The chemically unstable oxyapatite when exposed to moisture (water) further converts to crystalline hydroxyapatite (HA crystals). CaPO4 Oxyapatite Hydroxyapatite (Amorphous) (Crystalline) (Crystalline) Ca10 (PO4 )8 20H Strength is dependent on these crystals and the bond between the 1460°C melting 1510o C casting 1460°C Ceramming Exposure to moisture
  26. 26. Natural Enamel Cerapearl Composition of HA crystals Similar Arrangement of H.A. crystals Regular Irregular Light Refractive Index (Xo) 1.655 1.63 PH of solute in water 8.0 7.9 Density (g/cm3 ) 2.97 2.9 Thermal conductivity (Cal. Cm/cm2 Sec. °C) 0.0022 0.0023 Compressive strength (Mpa / psi) 384/0.05 x 106 590 / 0.08 x 106 Young’s Modulus of Elasticity (Gpa / Psi) 84.1 / 12.2 x 106 103 / 15.0 x 106 Tensile strength (Mpa) 103 150 Knoop Hardness Number (KHN) 343 350 Comparison of Physical Properties of Natural Enamel and Cerapearl
  27. 27. Other Physical Properties:  Coefficient of thermal expansion : 11.0 x 10-6 /°C  Young's Modulus : 103Gpa  Casting Shrinkage : 0.53%  Flexural strength similar to Dicor Biologic properties : Dense material, Chemically stable, pH similar to natural enamel, Non toxic/ biocompatible
  28. 28. Fabrication  Casting: The wax pattern of the proposed restoration is invested in phosphate-bonded high heat investment developed exclusively for this system (CTE to match Cera Pearl's casting shrinkage of 0.53%). Following burnout, the investment is transferred to an automatic casting machine designed especially for this system. The Cera Pearl crystals (8-10gms) are placed in the ceramic crucible, melted under vacuum (at 1460o C) and cast (at 1510o C) into the mold. Annealing is done one hour after the casting in an automatic furnace to release the inner stresses of the cast structure. The investment material around the cast structure is removed by sandblasting (25-30um Al2 O3 beads) and ultrasonically cleaned. The annealed casting is reinvested (CP crystal mold, Kyocera Corp.) for
  29. 29.  Ceramming: The ceramming oven is preheated at 750°C for 15 minutes. After the cast glass ceramic is place in the oven the temperature is raised at the rate 50o C/min until it reaches 870°C and held for 1 hour. After crystallization, the casting is dis-invested, and cleaned by sandblasting (201µm Al2 O3 powder). It appears white in comparison with natural enamel and requires the application of an external stain. Eg, Cerastain (Bioceram), which consists of B2 O3 -SiO2 -Al2 03 -K2 O glass, traces of various metal oxides.
  30. 30. Desirable characteristics of Apatite Ceramics  Cerapearl is similar to natural enamel in composition, density, refractive index, thermal conductivity, coefficient of thermal expansion and hardness. Similarity in hardness prevents wear of opposing enamel.  Bonding to tooth structure - Glass ionomer cements adhere to tooth structure (dentin and enamel) primarily bonding to the apatite component, and thus should also bond to the apatite phase within the glass-ceramic. To enhance this possibility, Cerapearl surface is activated by air abrading (to provide mechanical interlocking effect) or treatment with activator solution (etching of with 2N HCI preferentially removes the glassy phase from the surface, thus exposing the apatite phase). The glass ionomer can then bond to this apatite phase both chemically (ion-exchange) and mechanically (interlocking effect)
  31. 31. Lithia Based Glass-Ceramic Developed by Uryu; and commercially available as -Olympus Castable Ceramic (OCC) Composition: It contains mica crystals of NaMg3 (Si3AlO10) F2 and Beta Spodumene crystals of LiO.AI2O3.4SiO2 after heat treatment.
  32. 32. Calcium Phosphate Glass-Ceramic Reported by Kihara and others, for fabrication of all- ceramic crowns by the lost wax technique. It is a combination of calcium phosphate and phosphorus pentoxide plus trace elements. The glass ceramic is cast at 1050°C in gypsum investment mold. The clear cast crown is converted to a crystalline ceramic by heat treating at 645°C for 12 hours. Reported Flexural strength (116 Mpa); Hardness close to tooth structure. Disadvantages  Weaker than other castable ceramics;  Opacity reduces the indication for use in anterior
  33. 33. Advantages of castable glass ceramics  High strength because of controlled particle size reinforcement.  Excellent esthetics resulting from light transmission similar to that of natural teeth .and convenient procedures for imparting the required colour.  Accurate form for occlusion, proximal contacts, and marginal adaptation.  Uniformity and purity of the material.  Favorable soft tissue response.  X-ray density allowing examination by radiograph
  34. 34.  Hardness and wear properties closely matched to those of natural enamel  Similar thermal conductivity and thermal expansion to natural enamel  Dimensional stability regardless of any porcelain corrective procedure and subsequent firings
  35. 35. Advantage of cast glass-ceramics over metal-ceramics  The component chemical compounds are standardized, eliminating any inaccuracies, The forming procedures can be quality controlled.  Superior compressive strength because of its semi- crystalline form and is also a machinable material, Crack propagation's are interrupted by the crystalline structure.  Utilized conventional lost-wax technique similar to casting alloys. Hence, casting and finishing can be easily done.  Colour control, optical effects allow predictable and esthetic results.  Cast glass ceramics are thermal resistant.  Bacterial plaque adherence on the surface is inhibited, thus maintaining the tissues surrounding the
  36. 36.  Radiolucency allows for a dimension of depth in the observation of marginal integrity.  Wear rate values are similar to that of human enamel.
  38. 38. Regardless of the advanced state of the 300-year old technique of casting, each of its steps could induce error in the final casting. Until 1988, indirect ceramic dental restorations were fabricated by conventional methods (sintering, casting and pressing) and neither were pore-free. Pore-free restorations can be alternately produced by machining blocks of pore-free industrial quality ceramic. The tremendous advances in computers and robotics could also be applied to revolutionize dentistry and provide both precision and reduce time consumption. With the combination of optoelectronics, computer techniques and sinter-technology, the morphologic shape of crowns can be sculpted in an automated way. Registration of the mandibular jaw movements or of the functionally generated path in the mouth provides the necessary data for an interference-free escape of cusps from their fossae.
  39. 39. CAD/CAM is an acronym for Computer Aided Design / Computer Aided Manufacturing (or Milling). History of machining systems: 1971 - CAD/CAM technologies were introduced to the dental profession. 1979 - Heitlinger and Rodder followed by, 1980 -Moermann &Brandestini began to share this approach. 1983 -First dental CAD/CAM prototype was presented at the Garanciere conference in France. 1985 -The first CAD/CAM crown was publicly milled and installed in a mouth without any laboratory involvement. 1986 -The first generation Cerec 1 (Siemens Corp) was introduced. 1994 -The second generation Cerec 2 (Siemens Corp) was
  40. 40. 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.
  41. 41. Although each group had a slightly different philosophy and approach, they worked towards a common goal of integrating engineering applications of automation in the creation of dental restorations.  French system: Optical impression -Laser scanner, Data processed 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
  42. 42.  Swiss system: Optical impression - Optical topographic scanning using a 3-D oral camera; Data processed 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 N/C milling machine  Minnesota system: Optical impression -Photographic based system using a 35-mm camera with magnifying lens. 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 N/C machine.
  43. 43. Triad of fabrication: Fabrication of a restoration whether with traditional lost-wax casting technique or a highly sophisticated- technology such as a CAD/CAM system has three functional components:  Data acquisition  Restoration design  Restoration fabrication SUBTRACTIVE METHODS Grinding of porcelain restorations out of a preformed block either by means of CAD/CAM or by using a copy milling unit can be done by the so-called subtractive methods.
  44. 44. Machinable Ceramic system (MCS) for dental restorations:  Digital Systems (CAD/CAM): •Direct •Indirect Three steps :  3-dimensional surface scanning  CAD -Modelling of the restoration  Fabrication of restoration.
  45. 45.       Analogous systems (Copying methods) •Copy Milling / Copy Grinding or Pantography Systems Two steps :           Fabrication of prototype for scanning;          Copying and reproducing by milling •Erosive techniques         Sono Erosion         Spark Erosion
  46. 46. MACHINING SYSTEMS CAD/CAM (Digital) COPYING SYSTEMS (Analogous) Direct Indirect Copy Milling Erosion Cerec 1 & Cerec 2 Automill, DCS- President, Cicero, Denta, Denti CAD, Sopha – Bioconcept Manual Automatic Sono- erosion Spark – erosion Celay Ceramatic II DCP DFE Eroson ic DFE Procer a
  47. 47. Traditional technique High technology Data acquisition or information by impressions and translated into articulated stone casts Data acquisition or information is captured electronically, either by a specialized camera, laser system, or a miniature contact digitizer. Restoration design is the process of creating the wax pattern Restoration design is done by the computer – either with interactive help from the user or automatically. Restoration fabrication includes all the procedures from dewaxing upto the final casting (lost wax technique) Restoration fabrication includes machining with computer controlled milling machines, electrical discharge machining and sintering
  49. 49. DIGITAL SYSTEMS Computer  aided  design  and  computer  aided  manufacturing  (CAD/ CAM) technologies have been integrated into systems  to  automate  the  fabrication  of  the  equivalent  of  cast  restorations.  CAD/CAM milling  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  (computer-assisted  manufacturing  [CAM])  in  cutting the restoration from a block of material.
  50. 50. Stages of fabrication: Although  numerous  approaches  to  CAD/CAM for restorative dentistry have evolved, all systems  ideally involve 5 basic stages:         Computerized surface digitization       Computer - aided design       Computer - assisted manufacturing       Computer - aided esthetics       Computer - aided finishing (The  last  two  stages  are  more  complex  and  are  still  being  developed for including in commercial systems).
  51. 51. Computerized surface digitization: 3D-surface digitizing  or scanning methods are separated into :  •     Direct (at the tooth) •          Indirect  methods(via  impression  making  &  model  fabrication or via pro-inlay) •     Mechanical •     Optical sensors
  52. 52. Types of computerized surface digitization techniques:       Photogrammetry        Moire       Laser scanning       Computerized tomography (CT) scanning       Magnetic resonance imaging (MRl)       Ultrasound       Contact profilometry
  53. 53. Mechanical  scannings  conducted  by  a  profilometer  or  pinpoint  sensor  are  very  precise,  but  have  several  shortcomings.  Among  the  various  methods  of  optical  surface scanning, the active (laser) triangulation has been  proven  the  most  suitable,  however  it  requires  non- reflective surfaces for scanning (contact powder coating).  Laser  technique  and  contact  digitization  are  the  most  promising approaches from the point of view of cost and  accuracy.
  54. 54. FLOW CHART SHOWING SEQUENTIAL EVENTS OCCURING DURING CAD – CAM TECHNIQE OF FABRICATING A CERAMIC RESTORATION : The cavity preparation is scanned stereo-photogrammetrically, using a three- dimensional miniature video camera The small microprocessor unit stores the three dimensional pattern depicted on the screen The video display serves as a format for the necessary manual construction via an electric signal The microprocessor develops the final three-dimensional restoration from the two dimensional construction The processing unit automatically deletes data beyond the margins of the preparation The electronic information is transferred numerically to the miniature three-axis milling device Driven by a water turbine unit, the milling device generates a precision fitting restoration from a standard ceramic block
  55. 55. CEREC SYSTEM The CEREC (Ceramic Reconstruction) system ( Siemen/sirna corp) was originally developed by Brains AG in Switzerland  and  first  demonstrated  in  1986,  but  had  been  repeatedly  described since 1980. Identified as CEREC CAD/CAM system,  it  was  manufactured  in  West  Germany  and  marketed  by  the  Siemens group. Cerec System consists of :       A 3-D video camera (scan head)    An  electronic  image  processor  (video  processor)  with  memory unit (contour memory)       A digital processor (computer) connected to,       A miniature milling machine (3-axis machine)
  56. 56. The Optical impression: A small hand held video camera  with  a  1-cm  wide  lens  (scanner)  when  placed  over  the  occlusal  surface  of  the  prepared  tooth,  emits  infrared  light  which passes through an internal grid containing a series of  parallel  lines.  The  pattern  of  light  and  dark  stripes  which  falls  on  the  prepared  tooth  surface  is  reflected  back  to  the  scanning head and onto a photoreceptor, where its intensity  is recorded as a measure of voltage and transmitted as digital  data to the CAD unit.
  57. 57. Procedure: •        The prepared and surrounding tooth surfaces are coated  with CEREC powder (L.D. caulk -Ti02 and talc) to eliminate  light  reflections  and  to  obtain  an  opaque  reflective  surface  (few µm thick only). •        The hand - held camera is positioned over the prepared  tooth, and an image of the preparation is then simultaneously  projected onto the screen. •         The  camera  is  adjusted  until  the  image  is  clear  and  properly angulated for all aspects of the prepared tooth to be  visible in complete focus.
  58. 58. •        The video search mode enables assessment whether  the camera viewing axis is compatible with the inlay/ onlay  path  of  insertion.  If  viewing  is  acceptable  the  three  dimensional  scanning  is  triggered  by  release  of  the  foot  pedal. •         The  operator  now  checks  the  preparation  and  its  three-dimensional  representation  for  corrections  or  modifications  to  be  made,  if  necessary.  Once  the  appropriate optical orientation is generated, the operator can  'freeze-frame' the preparation into a static image.
  59. 59.  Designing the Restoration:  The  proposed  restoration  is  designed  by  tracing  frame  lines  on  the  optical  impression  (fixed  image)  which  is  projected  onto  the  screen.  A  cursor  controlled  by  reverse  'mouse'  located  on  top  of  the  unit  is  used  to  define  the  limits/boundaries,  starting  from  the  gingival margin and moved along the internal line angles at  intermediate positions commands the computer which draws  a continuos line, through all placed points and displays it on  the  screen.  The  operator  can  carefully  examine,  edit  and  if  necessary,  even  modify  the  pattern  at  any  moment  in  the  procedure.  After  the  margins,  walls,  proximal  contour  and  contact  as  well  as  the  location  of  marginal  ridges  are  established, the electronically designed proposed restoration  can be viewed as a 3-dimensional model on the monitor, and  stored automatically on the program disk (floppy).
  60. 60. Milling of the Ceramic restoration:  The  restoration  is  milled  (4  –  7minutes)  with  a  diamond  wheel  from  a  pre- manufactured and standardized ceramic block in the milling  chamber of the CAM unit. Factory standardized, preformed  dental porcelain blocks are homogenous and almost pore- free (Vita Cerec blocks; Dicor-Cerec blocks).
  61. 61. The CAM unit:  A pump system with an attached water reservoir located at  the  base  of  the  mobile  cart  maintains  the  water  pressure  required for the hydraulic driven water turbine in the milling  chamber.  During  milling  about  5  litres  of  water  is  cycled  internally  which  eliminates  the  need  for  external  water  supply  and  drainage.  The  water  reservoir  system  also  contains a microporous filter that traps any of the loosened  diamond  particles  separated  from  the  wheel  for  future  retrieval.
  62. 62.  Procedure:        The  appropriate  ceramic  block  is  selected  from  a  series  consisting of different sizes and shades.        The  ceramic  block  is  mounted  on  a  metal  stub  (retainer),  inserted into the milling unit and grinding operation is initiated.        Grinding  of  the  ceramic  restoration  is  done  by  a  diamond- coated disk/ wheel in conjunction with a high velocity water-spray,  which  simultaneously  cools  and  cleans  the  milling  disk.  The  restoration is milled from the mesial to the distal proximal surfaces  with  the  block  rotating  along  its  central  axis  and  being  steadily  advanced  forward  during  the  milling  process.  In  addition,  the  diamond wheel not only rotates but also translates up and down over  the porcelain block being milled. A series of steps (200-400) or cuts  are required for milling a ceramic restoration.     At the end of the milling operation, the completed restoration  falls  to  the  bottom  of  the  chamber  from  where  it  can  be  readily
  63. 63.  The computer program associated with the milling process has additional interesting features such as:        Before  the  milling  process,  the  screen  displays  the  dimensions  of  the  restoration  from  one  proximal  surface  to  the other in 1/900th   of a mm.        During  the  milling  operation,  the  screen  continuously  informs the operator of the percentage of the completion. A  continuous  readout  is  displayed  concerning  the  cutting  efficiency  of  the  diamond  wheel,  thereby  indicating  the  probable need for replacement.
  64. 64. Clinical shortcoming of Cerec 1 system:            Although the CEREC system generated all internal  and external aspects of the restoration, the occlusal anatomy  had  to be developed by the  clinician using  a flame-shaped,  fine-particle diamond instrument and conventional porcelain  polishing procedures were required to finalize the restoration.              Inaccuracy of fit or large interfacial gaps.       Clinical  fracture  related  to  insufficient  depth  of  preparation.             Relatively poor esthetics due to the uniform colour  and lack of characterization in the materials used.
  65. 65. Cerec 2 system The  Cerec  2  unit  (Siemen/Sirona),  based  on  the  process  developed  by  Morman  &  Brandestini  was  introduced  in  September 1994, and is the result of constant further development  via different generations of Cerec units to eliminate the previous  limitations.  The maior changes include :          Enlargement of the grinding unit from 3 axis to 6 axis.    Upgrading of the software with more sophisticated technology  which allows machining of the occlusal surfaces for the occlusion  and the complex machining of the floor parts. Other technical innovations of Cerec 2 compared to Cerec 1:        The improved Cerec 2 camera : new design, easy to handle,  a  detachable  cover  (asepsis/sterilization),  reduction  in  the  pixel  size/picture element to improve accuracy and reduce errors.
  66. 66.       Data representation in the image memory and processing  increased by 8 times, while the computing capacity is 6 times  more efficient.        Magnification  factor  increased  from  x8  to  x12  for  improved accuracy during measurements.       Monitor can be swiveled and tilted, thus facilitating visual  control of the video image. Other changes include modification  of foot control, keys and their positions on the keyboard.       Simultaneous grinding using cylindrical diamonds (2mm  diameter,  particle  #64um,  77,000rpm  and  cutting  speed  8m/s)  and radial infeed grinding of the grinding disk (6um particle #,  18000rpm and cutting speed 38m/s).
  67. 67.        Extended  matching  options  facilitate  grounding  of  complex  floor  shapes  in  inlays/  onlays.    Provides  three  different  programs  for  Extrapolation,  Correlation  and  Veneer.        Cerec  2  software  (cos  4.20)  permits  custom  veneer  preparation  and  class  IV  preparations  with  incisal  edge  coverage.        Improved  in  rigidity  and  grinding  precision  by  24  times.          Improved accuracy of fit (reduction in inter-facial  gap from 84+38um/ Cerec 1 to 56+27um/ Cerec 2).
  68. 68. Machinable ceramics ( Ceramics used in machining systems) are  pre-fired  blocks  of  feldspathic  or  glass  -  ceramics.   Composition : Modified  feldspathic  porcelain  or  special  fluoro-alumino-silicate  composition  are  used  for  machining  restorations. Properties       Excellent fracture and wear resistance       Pore-free       Possess both crystalline and non-crystalline phase (a 2- phase composition permits differential etching of the internal  surface for bonding).
  69. 69.  Ceramic CAD/ CAM restorations are bonded to tooth structure by :        Etching for a bond to enamel       Conditioning, priming and bonding (when appropriate)       Etching (by HF acid) and priming (silanating)       Cementing with luting resin.   CAD/CAM  restorations  (inlay/onlays)  are  fabricated  primarily  from  ceramic  materials,  while  subtractive  fabrication  of  metal  alloys  or  titanium  have  only  been  investigated for crowns, copings and bridges.
  70. 70. Machinable Ceramics The industrially prefabricated ceramic ingots/ blank used are  practically  pore-free  which  do  not  require  high  temperature  processing and glazing, hence have a consistently high quality.  The  blanks  measure  approximately  9  x  9  x  13  mm  and  are  industrially  fabricated  using  conventional  dental  porcelain  techniques.  Eg:  Vitadur  353N  (Vita  Zahnfabrik,  Bad  Sackingen, West Germany) frit powder is mixed with distilled  water, condensed into a 10 x 10 x l5 mm steel die and fired  under  vacuum  (the  temperature  is  increased  at  a  rate  of  60O C/min to 950o C and held for one minute). Two classes of machinable ceramics available are:       Fine-scale feldspathic porcelain       Glass-ceramics
  71. 71.  Cerec Vitabloc Mark I : This feldspathic porcelain was the first  composition  used  with  the  Cerec  system  (Siemens)  with  a  large  particle size (10 - 50µm). It is similar in composition, strength, and  wear  properties  to  feldspathic  porcelain  used  for  metal-ceramic  restorations. Cerac Vitabloc Mark II  :  This  is  also  a  feldspathic  porcelain  reinforced with aluminum oxide (20-30%) for increased strength and  has a finer grain size (4µm) than the Mark I composition to reduce  abrasive wear of opposing tooth. Dicor MGC (Dentsply, L.D. Caulk Division)  : This  is  a  machinable glass-ceramic composed of fluorosilica mica crystals in  a glass matrix. The micaplates are smaller (average diameter 2 um)  than  in  conventional  Dicor  (available  as  Dicor  MGC  -  light  and  Dicor  MGC  -  dark).  Greater  textural  strength  than  castable  Dicor  and  the  Cerec  compositions.  Softer  than  conventional  feldspathic  porcelain. Less abrasive to opposing tooth than Cerec Mark I, and  more than Cerec Mark II (invitro study results).
  72. 72. MGC -F (Corning Inc.) : Machinable glass ceramic developed to  overcome the deficiencies of the Vita Mark II and Dicor MGC. It is  a  tetrasilicic  mica  glass  -  ceramic  with  minor  compositional  and  microstructural  changes  from  Dicor  MGC  to  enhance  its  fluorescence and machinability.  Pro CAD (Ivoclar AG, Liechtenstein) :  The  Pro  CAD  line  (Professional  Computer  Assisted  Design)  is  a  product  package  suitable for all Cerec 2 applications. It is a high-strength optimized,  leucite-reinforced  glass  ceramic  material,  available  as  blocks  in  different sizes and in the chromascop shades. Celay :  This  material  can  be  used  in  both  copy  milling  and  CAD/CAM techniques. According to the manufacturer, it is a fine- grained  feldspathic  porcelain  used  to  reduce  abrasiveness  with  a  composition  identical  to  that  of  Cerec  Vitablocs  Mark  II.  In  addition,  both  In-Ceram  and  Spinell  (Vita)  are  available  for  processing in the green state in conjunction with Celay.
  73. 73. Other machinable ceramics being developed include:        Bioglass (Alldent Corp., Rugell, Liechtenstein)        DFE  -Keramik/Krupp  Medizintechnir  GmbH,  Essen,  Germany; Bioverit / Mikrodenta Corp       Empress / Vivadent –lvoclar Corp, Schaan, Liectenstein.
  74. 74. Clinical procedures for Cerec CAD/CAM:  Tooth  preparation  &  Optical  registration  :    Simple,  box  shaped  preparations  suffice  for  the  Cerec  three-dimensional  scanning  and  fabrication  process.  The  procedure  is  not  dependent  on  any  cavity  preparation  size.  Simple  and  complex  proximal  preparations  for  both  inlays  and  onlays  are  readily  and  correctly  milled.  Undercuts  in  cavity  walls do not affect the optical scanning and are tilled in with composite  resin  during  the  cementation.  Straight  walls  with  right  angles  are  recommended The 4 to 6 degree divergence required for cast inlays is not  necessary  using  Cerec  system;  parallel  walls  suffice,  thereby  ensuring  maximal  preservation  of  hard  dental  tissues.  The  occlusal  and  proximal  cavity margins are not beveled. Instead, the cavity walls and enamel edges  are finished using diamond coated finishing stones. The gingival floor is  horizontal  or  declines  between  5  and  15  degrees  towards  the  gingival  margin. The optical scanning is facilitated by having clearly defined walls  and  cavity  margins  and  by  the  use  of  rubber  dam  during  the  optical  scanning  and  cementation  stages.  Gingival  margins  of  the  preparation  must be made clearly visible by placement of retraction cord, or by use of  electrosurgery incision surgery.
  75. 75. The optical scanning is facilitated by having clearly defined  walls  and  cavity  margins  and  by  the  use  of  rubber  dam  during  the  optical  scanning  and  cementation  stages.  Gingival margins of the preparation must be made clearly  visible  by  placement  of  retraction  cord,  or  by  use  of  electrosurgery incision surgery. Cementation:  The  small  quantities  of  composite  resin  cement  required  for  cementation  ensures  a  thin  layer  between  the  ceramic  and  the  enamel.  This  thin  layer,  together  with  the  microretentive  bond  within  the  ceramic  and  enamel  apparently  minimizes  the  negative  aspects  of  the  polymerization  shrinkage  and  the  high  thermal  expansion  of  the  cement.  Composite  resin  cements  blend  esthetically with porcelain and enamel.
  76. 76.  The clinical advantages of the Cerec system:       The restorations made from prefabricated and optimized,  quality-controlled ceramic porcelain can be placed in one visit.        Transluency  and  color  of  porcelain  very  closely  approximate the natural hard dental tissues.        Further,  the  quality  of  the  ceramic  porcelain  is  not  changed by the variations that may occur during processing in  dental laboratories.        The  prefabricated  ceramic  is  wear  resistant.  The  optimized structure of the ceramic enables optimal polishability  of  the  material  and  low  abrasion  of  the  cusp  enamel  of  thCICERO System
  77. 77. •         Porcelain  ceramic  etching  (HF  5%  for  60  seconds):  microrentive  adhesive  bond  between  porcelain/ceramic  and  the bonding agent/composite resin cement.                       Enamel-etching  technique  (H3PO4  35%  for  30  seconds):  microretentive  adhesive  bond  between  composite  resin cement/bonding agent and enamel.
  78. 78. CICERO System    Computer  Integrated  Crown  Reconstruction  (Elephant  industries).  This  Dutch  system  was  marketed  with  the  Duret  (French)  system,  Sopha  Bioconcept  and  the  Minnesota system (Denti CAD) as the only three systems  capable  of  producing  complete  crowns  and  FPD's.  The  Cicero CAD/CAM system developed for the production of  ceramic-fused-to-metal restorations, makes use of :       Optical scanning       Nearly net -shaped metal and ceramic sintering   Computer-aided  crown  fabrication  techniques.  Alloy  sintering eliminates casting and therewith many processing  steps in the fabrication of metal-ceramic
  79. 79. The  unique  feature  of  the  Cicero  system  is  that  it  produces Crowns, FPD's and inlays with different layers  such  as  metal  and  dentin  and  incisal  porcelains,  for  maximum strength and esthetics.
  80. 80. COMET System (Coordinate M Easuri ng Technique, Steinbichler Optotechnik,  GmbH,  Neubeurn,  Germany)    This  system  allows  the  generation  of  a  3-dimensional  data  record  for  each  superstructure  with  or  without  the  use  of  a  wax-pattern.  For  imaging,  2  -  dimensional  line  grids  are  projected  onto  an  object,  which  allows  mathematical  reproduction  of  the  tooth  surfaces.  It  uses  a  pattern  digitization  and  surface  feedback  technique, which accelerates and simplifies the 3-dimensional  representation  of  tooth  shapes  while  allowing,  individual  customization and correction in the visualized monitor image.
  81. 81. Other Digital Systems:   The Duret System (Hanson International):  The Duret CAD-CAM system was developed by Francois Duret and produced by Sopha (Lyon, France). It was made  of 3 discrete units :       A camera module       A CAD module  The milling module.
  82. 82. Optical impression was made using Electro-optical method (a  laser  scanner)  combining  Holography  and  Moire.  The  digitized  data  from  the  CAD  unit  is  combined  with  data  relating to the dynamic movements of jaw which is provided  by  a  proprietary  articulator.  called  the  Access Articulator  linked  to  the  CAD  unit.  This  original  Duret  system  using  highly  sophisticated  and  complex  imaging/  designing  procedure  was  designed  primarily  to  fabricate  full  crowns.  However, since its introduction, both the original system and  the derivative version The SOPHA system have had limited  commercial success.
  83. 83. The SOPHA System (Sopha Bioconcept, Inc Los Angeles, CA) was commercially introduced in 1990/91 in France, but  is apparently no longer available.   The REKOW Svstem (Digital Dental System)  was  developed  by  Dr. Diane Rekow  at  the  University  of      Minnesota.  This  system  initially  used  a  photogrammetric  method  for  intraoral  surface  digitization  of  the  preparation  using  a  pen  digitizer,  but  later  used  mechanical  -  manual  scanning  and  was  marketed  for  dental  laboratory  use  in  Europe by Bego (Bremen, Germany).
  84. 84. The Denti CAD svstem:  Used  a  miniature  mechanical  linkage  designed  by  Foster  Miller  Inc  (Wallham,  Mass  USA)  (unique  robotic  arm  digitizer)  which  can  be  used  both  intraoral1y  or  an  traditional  models  and  dies  for  tracing the image. The Denti CAD system is capable of  producing  restorations  from  alloys,  composites  and  ceramics.  It  uses  a  unique  robotic  arm  digitizer  (a  miniature mechanical linkage), designed by Foster Miller  Inc  (Waltham,  Mass,  U.S.A.)  that  can  be  used  both  intraorally or  traditional  models and  dies  for tracing the  image.
  85. 85. The DUX s stem/The Titan System (DCS groups Dental, Allschwill, Switzerland)  was  introduced  in  1991  by  DCS/GIM -Alldent. It consists of ; A miniature contact digitizer (pantograph) A central computer A milling unit.  The  digitizer  consists  of  a  table  that  shifts  a  die  or  model  beneath ~ contact stylus. This system is currently distributed  under the brand name DCS -President (DCS/ Girrbach).
  86. 86. Advantage of CAD/CAM (Cerec system)over other systems        Eliminates impression model making and fabrication of  temporary prosthesis.        Dentist  controls  the  manufacturing  of  the  restoration  entirely without laboratory assistance.       Single visit restoration and good patient acceptance.       Alternative materials can be used, since milling is not  limited to castable materials.       The use of CAD/ CAM system has helped provide void  free porcelain restorations, without firing shrinkage and with  better adaptation.
  87. 87.        It  can  construct  various  types  of  ceramic  restorations.  Hence,  can  be  used  as  an  alternative  to  metallic  restorations  allowing  placement  of  esthetic  inlays/onlays  in  stress  bearing  areas  of  posterior  teeth  (because  of  its  high  resistance  to  abrasion, good marginal adaptation and also as an alternative to  complete  or  full  coverage  crowns  that  require  extensive  tooth  reduction).  Half  and  three-quarter  crowns  and  Cerec  veneer  laminates can also be directly placed as easily.        CAD  -  CAM  device  can  fabricate  a  ceramic  restoration  such as inlay/ onlay at the chair-side.       Eliminates the asepsis link between the patient, the dentist,  operational field and ceramist.         The shapes created in the CAD unit are well defined, and  thus a factor such as correct dimensions can be evaluated and  corrections/modifications  can  be  carried  out  on  the  display  screen itself .
  88. 88.       Using industrially prefabricated ceramic blanks compared  to that fabricated by the dental technician is the maintenance of  consistently  optimally  high  quality  of  the  material  under  industrial conditions controlled by the manufacturer.       Glazing is not required and Cerec inlay onlays can easily  be polished.       Minimal abrasion of opposing tooth structure because of  homogeneity of the material (abrasion does not exceed that of  conventional and hybrid posterior composite resins).        The mobile character of the entire system enables easy  transport from one dental laboratory to another.
  89. 89. Disadvantages:  Limitations in the fabrication of multiple units.  Inability to characterize shades and translucency.  Inability to image in a wet environment (incapable of obtaining an accurate image in the presence of excessive saliva, water ore blood).  Incompatibility with other imaging system.  Extremely expensive and limited availability.  Still in early introductory stage with few long-term studies on the durability of the restorations.
  90. 90.  Lack of computer-controlled processing support for occlusal adjustment.  Technique sensitive nature of surface imaging that is required for the prepared teeth.  Time and cost must be invested for mastering the technique and the fabrication of several restorations, to develop proficiency in the operator.
  91. 91. ANALOGOUS SYSTEMS (COPYING / PANTOGRAPHY METHODS ) Copy milling It is the mechanical shaping of an industrially prefabricated ceramic material, which is consistent in quality and its mechanical properties (an improvement over conventional ceramics). Copy milling includes fabrication of a prototype (pro-inlay or crown) usually via impression making and model preparation. Based on the model, a replica of inlay / crown is made and fixed in the copying device and transferred 1: 1 into the chosen material such as ceramic.
  92. 92. Materials used -The choice of material depends in mostly on the type of margin required for the restoration. Virtually any geometry and size can be copy milled as long as there is direct access of the finger guide and cutting tool to the surfaces involved. Because titanium has a very high melting temperature, it is difficult to conveniently cast; however it can be copy milled easily and inexpensively. Composite and ceramic materials are most commonly used for copy milling dental restorations.
  93. 93. Sono erosion -is based on ultrasonic methods. First, metallic negative moulds (so-called sonotrodes) are produced of the desired restoration, both from the occlusal as well as from the basal direction. Both sonotrodes fitting exactly together in the equational plane of the intended restoration are guided onto a ceramic blank after connecting to an ultrasonic generator, under slight pressure. 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.
  94. 94. Spark Erosion refers to 'Electrical Discharge Machining' (EDM) which was used by the tool and die industry during the 1940's and was adapted into dentistry in 1982. It may be defined as a metal removal process using a series of sparks to erode material from a workpiece in a liquid medium under carefully controlled conditions. The liquid medium usually, is a light oil called the dielectric fluid. It functions as an insulator, a conductor and a coolant and flushes away the particles of metal generated by the sparks.
  95. 95. Advantages of EDM desirable for dental applications: •EDM is not affected by metal-hardness because it is a thermal process. •Adhesive characteristics of the workpiece do not affect EDM because it is a non-contact method of removing metal. •EDM provides a smooth bur-free surface. •EDM can be used to machine thin objects without distortion because there are virtually no mechanical forces created. •EDM can be used to make long, small diameter cuts because there is little, if any, torque on the electrode to cause breakage. •EDM is accurate to within 0.0001 inch. The major disadvantage is the cost of the equipment.
  96. 96. Spark Erosion (SAE) unit (Dental Arts Laboratories, Inc, Illinois). A graphite or copper electrode acts as a tool that invades the piece of base metal and erodes a negative form in the shape of the electrode. The process is accomplished by lightning like sparks generated between the electrode and the restoration. The sparks melt the alloy by heating it to between 3000°C and 5000°C. These sparks remove small amounts of the metal substrate within microseconds. The entire process takes place in a dielectric liquid bath that prevents the alloy from burning. Stress characteristics can be eliminated through the application of spark erosion before or after the ceramic or acrylic resin surface is added. The spark erosion method can be applied to any type of conductible metal/ alloy such as gold, base metal and titanium. This method of erosion has been named as SAE Secotec.
  97. 97. CELAY System The Celay System (Mikrona AG, Spreintenbach, Switzerland) became first commercially available in 1992. It is a high precision, manually operated copy milling machine and the fabrication principle is the same as for 'Key' duplication. This system was originally. designed and intended for use in the dental laboratory; however., it may also be used at the chairside. Method:  An impression (silicone) of the prepared tooth is made and poured in die stone.  A prototype resin coping of the restoration (prototype) called 'pro-inlay' (a provisional inlay) is fabricated on the die using a blue light-cured resin (Celay-Tech, Mikrona Technologies, AG, Switzerland).
  98. 98.  The cured resin prototype is removed from the die and fixed on the left side of the relay unit using a special retaining device (rod shaped).  A prefabricated ceramic blank (eg-aluminous core ceramic'In- Ceram') is fixed in the carving chamber on the right side of the relay unit.  The reference disk (tracing tool) mechanically traces or scans the surface of the prototype (pro-inlay).
  99. 99.  Duplicating the movements of the reference disk, the rough milling disk (a coarse diamond instrument with a grit size of 126 µm) and a high speed turbine driven by air pressure, machines the rough contour of the ceramic restoration by synchronized grinding over 8-axes for effective bulk reduction. For milling a coping, the lumen of the coping is scanned and milled with coarse ball and round tipped diamonds. Both sides of the relay unit are connected by a geometric transfer mechanism to link the three- dimensional movement of the tracing device with the milling device. During the milling process, the milling chamber is protected with a clear cover and a cooling liquid (Celcool, Mikrona AG) is sprayed on the blank and on the instrument.
  100. 100.  Since the rough milling disk is slightly smaller than the scanning disk, it produces a slightly oversized restoration. The final contour of the restoration is developed with 64µm grit finishing diamond instruments.  To ensure a complete and accurate tracing, the pattern is coated with contact or indicating powder (Celtouch, Mikrona AG). This powder is removed on contact with the tracing instruments so that areas already scanned can be differentiated from un scanned areas.  The external surfaces are finished with -disks and the internal surfaces with round-tipped and sharp/ fine-tipped diamond stones.  Final fit of the machined inlay/ coping is examined, and internal discrepancies marked and reworked with repeated scanning  The internal surface is either acid etched or air-abraded before silanization and
  101. 101. By combining the Celay system, with elements of In-Ceram technology, copy milled glass-infiltrated aluminous core restorations can be fabricated. In-Ceram or In-Ceram Spinell materials are machined by Celay and then infiltrated with a sodium-lanthanum glass in a manner similar to that of conventional In-Ceram restorations, and finally veneered with Vitadur Alpha porcelain. The fabrication of copy-milled In- Ceram crown substructures with the Celay system combines the positive mechanical properties of glass-infiltrated aluminous core materials with the advantages of industrially prefabricated ceramics.
  102. 102. Advantages over conventional In-Ceram technology:  The processing time is considerably shorter because die duplication and 10 hour sintering are not necessary.  Glass infiltration can be performed in a conventional ceramic furnace in 40 minutes, because of the higher capillary effect of the industrially sintered alumina blank (homogenous structure, even particle distribution).  The industrially prefabricated material also has a higher flexural strength than the conventional In-Ceram material.
  103. 103. PROCERA System : The Procera System (Nobel Biocare, Gioteborg, Sweden) embraces the concept of CAD/CAM to fabricate dental restorations. It was developed by Andersson .M & Oden .A in 1993, through a co-operative effort between Nobel Biocare AB (Sweden) and Sandvik Hard Materials AB (Stockholm, Sweden). It consists of a computer controlled design station in the dental laboratory that is joined through a modern communication link to Procera Sandvik AB in Stockholm, Sweden, where the coping is manufactured with advanced powder technology and CAD/CAM technique.
  104. 104. Procedure requires 3 steps for fabrication:  Scanning : At the design station, a computer controlled optical scanning device maps the surface of the master die and is sent via modem to the Procera production facility.  Machining : At the production facility, an enlarged die is fabricated that compensates for the 15-20% sintering shrinkage of the alumina core material. High-purity alumina powder is pressed onto the die under very high pressure, milled to required shape, and fired at a high temperature (1550°C) to form a Procera coping.
  105. 105.  Veneering : The sintered alumina coping is returned to the dental laboratory for veneering thermally compatible low fusing porcelains (All Ceram veneering porcelain) to create the appropriate anatomic form and esthetic qualities. All Ceram veneering porcelain (Ducera) has a coefficient of thermal expansion adjusted to match that of aluminium oxide (7x10-6 /°C). It also has the fluorescent properties similar to that of natural teeth and the veneering procedures require no special considerations. The reported flexural strength of the Procera All Ceram crown (687 Mpa) is relatively the highest amongst all the all-ceramic restorations used in dentistry (attributed to the 99.9% alumina content).
  106. 106. This system can be used to fabricate two types of dental restorations :  A Porcelain-fused-to-metal restoration made of titanium substructure with a compatible veneering porcelain using a combination of machine duplication and spark- erosion (The Procera Method, Noble Biocare).  An all-ceramic restoration using a densely sintered high-purity (99.9%) alumina coping combined with a compatible veneering porcelain.
  107. 107. Porcelain-fused-to-metal restoration : The Procera System was initially used to fabricate veneered crowns and fixed partial dentures by combining a titanium substructure with compatible low-fusing veneering porcelain such as Ti- Ceram. Components used: Rods of pre-fabricated cold-worked bars or solid cylindrical blanks of Commercially pure Titanium (CpTi) and a low fusing veneering porcelain Ti-Ceram fired at 750°C.
  108. 108. Procedure: The working time required to fabricate the titanium coping is about 35 minutes. It requires two procedures : •Mechanical milling process -external surface of titanium coping is milled from the cylindrical titanium blank in 5-6 minutes. •Spark erosion process -The internal configuration of the titanium coping is developed in about 8 to 10 minutes. The internal surface of the titanium coping is air abraded (120µm particles of Al2 O3 ) to remove the surface oxide layer accumulated during the spark erosion process. The external surface is also air abraded and then veneered with a low-fusing veneering porcelain compatible with titanium such as Ti-Ceram in the conventional manner and fired at 750°C. •This method can also be used for milling implant system restorations.
  109. 109. Advantages (mainly related to use of titanium) : •Biocompatibility of titanium - suitable for use mainly in metal sensitive patients. •Low-cost of titanium relative to noble metal alternatives. •Standardization of procedure for fabricating titanium coping with consistent results. •Accuracy of fit •Ti-Ceram is less abrasive than conventional porcelain.
  110. 110. All-ceramic restoration: The Procera system has also been used to produce an all-ceramic crown known as Procera All Ceram Crown which is composed of a densely sintered, high-purity (99.9%) alumina coping combined with a compatible veneering low fusing porcelain such as All Ceram Porcelain (Ducera). Other copying systems  Ceramatic II Svstem (Askim Corp. Sweden): In this system scanning is performed automatically, and this applies to the DCP system as well.  The DFE -system and Erosonic (ESPE Dental Medizin Corp., Seefeld Germany) both make use of ultrasonic erosion for the machining of ceramic. For this purpose sonotrodes must be made in advance as negative forms of the inner and outer contours of the restoration.
  111. 111. Advantage of milling methods : •Reducing the labour time needed. •Single appointment restorations (in a period of 3 to 13 minutes). •Can be used for both direct and indirect fabrications. Advantages of Celay system over the Cerec system : •Celay could recreate all surfaces of a restoration whereas Cerec I could not make the occlusal surface. •Celay has the potential to fabricate crowns and short-span bridges with In-Ceram system (Vita, Germany).
  113. 113. PRESSABLE CERAMICS Shrink-free Ceramics Leucite-reinforced Glass-ceramics Cerestore IPSEmpress Al-Ceram Optec Pressable Ceramic (OPC)
  114. 114. SHRINK FREE ALUMINA CERAMICS The shortcomings of the traditional ceramic material and techniques; like failures related to poor functional strength and firing shrinkage limited the use of "all-ceramic" jacket crowns. The development of non-shrinking ceramics such as the systen'l was directed towards providing an alternate treatment. Brief History : 1983 - Sozio & Riley described the use of shrink-free ceramic coping. 1987 - Hullah & Williams described the formulation of shrink free ceramics Shrink-free ceramics were marketed as two generation of materials under the commercial names :  Cerestore (Johnson & Johnson. NJ, USA)  Al-Ceram (Innotek Dental Corp, USA)
  115. 115. CERESTORE Non-Shrink Alumina Ceramic (Coors Biomedical Co., Lakewood, Colo.) is a shrink-free ceramic with crystallized magnesium alumina spinel fabricated by the injection molded technique to form a dispersion strengthened core. Composition Of Shrink Free Ceramic Unfired Composition Fired Composition (Core) A12 O3 (small particles) 43% A12 O3 (large particle) 17% MgO 9% Glass frit 13% Kaolin Clay 4% Silicon resin (Binder) 12% Calcium Stearate 1% Sterylamide 1% A12 O3 (Corundum) 60% MgA12 O4 (Spinel) 22% BaMg2 A13 (Barium Osomilite) 10%
  116. 116. Chemistry: The shrink-free ceramic material essentially consists of Al2 O3 and MgO mixed with a Barium glass frits. On firing a combination of chemical and crystalline transformation produces Magnesium aluminate spinel, which occupies a greater volume than the original mixed oxides (raw ingredients), and thus compensates for the conventional firing shrinkage of ceramic.  Chemical transformation: During firing from 160 °C to 800°C, the silicone resin (binder) converts from SiO to SiO2 which in turn combines with alumina to form aluminosilicate.  Crystalline transformation: The primary inorganic reaction involves MgO, Al2 O3 and the glass frit. The aluminosilicate formed reacts with the incorporated magnesia to form spinel, which is also one of the strongest ceramic oxides.
  117. 117. Alumina (AI2 O3 ) + Magnesia (MgO)  Magnesium Aluminate Spinel (MgAl2 O4 ) Al2 O3 + MgO  MgAI2 O4 Density (g/cm3 ) 3.9 + 3.58  3.60 Mol wt(g) 101.96 + 40.31  142.27 Volume cm3 25.72 + 11.26 (36.98)  39.52 (Net Volume Increase - 2.54 cm3 ) Net % volume expansion - 6.87% Net % linear expansion - 2.35%
  118. 118. During firing from 900 to 1300°C, the glass frit takes MgO & Al2 O3 into solution and subsequently precipitates the spinel phase which in conjunction with the coarser alumina particles acts as strengthener in the fired core. The final microstructure of the core material consists of a multiphased mixed oxide system of aluminates. Flexural strength is similar to that of the traditional alumina core. Fabrication: By Transfer Molding process which is identical to injection moulding of acrylic resin denture bases. Copings are formed by transfer-molding the ceramic directly onto non- shrinking heat stable epoxy master dies  The wax pattern on the epoxy die is sprued, invested and burned out.
  119. 119.  The flask is placed on a heating element (oven) and removed after it reaches the molding temperature.  Shrink-free ceramic material supplied as dense pellets is heated until the silicone resin binder is flowable (160°C) and then transferred by pressure (under a plunger) directly on the master die. The silicone resin binder is thermoplastic and thermosetting, hence after injection into the mold and around the master die, it automatically sets.  The flask is quenched and the ceramic coping is fired in a micro-processor controlled furnace (1300°C) to achieve zero- shrinkage.  The sintered coping is replaced on the die and veneered with conventional aluminous porcelain.
  120. 120. Physical properties of First Generation Cerestore Core Material : Compressive Strength : 10.48 MN/m2 ; Flexural Strength : 120 MN/m2 Modulus of elasticity : 1.23 x 105MN/m2 Density : 2.9 gm/cm3 Linear coefficient thermal expansion : 5.6xl0-6 /°C Poison's ratio : 0.23
  121. 121. Advantages :  Innovative feature is the dimensional stability of the core material in the molded (unfired) and fired states. Hence, failures related to firing shrinkage are eliminated.  Better accuracy of fit and marginal integrity.  Esthetics enhanced due to depth of colour due to the lack of metal coping.  Biocompatible (inert) and resistant to plaque formation (glazed surface).  Radiodensity similar to that of enamel (presence of Barium osumilite phase in the fired core allows radiographic examination of marginal adaptation and visualization under the crown).  Low thermal conductivity; thus reduced thermal sensitivity.  Low coefficient of thermal expansion and high modulus of elasticity results in protection of cement seal.
  122. 122. Disadvantages :  Complexity of the fabrication process.  Need for specialized laboratory equipment (Transfer molding process) and high cost.  Inadequate flexural strength (89MPa) 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. The material underwent further improvement and developed into a product with a 70 to 90% higher flexural strength. This was marketed under the commercial name Al Ceram (Innotek Dental, Lakewood, Colo.)
  123. 123. Advantage second generation Cerestore Core Materials :  Recrystallization of residual glass - Flexural strength > 22.5 MN/m2 (32,000psi)  High polycrystalline content - static fatigue potential comparable to high glass content systems.  Same relative thermal conductivity of core and veneer porcelain - Interfacial stress comparable to ceramometal systems.  Low coefficient of thermal expansion - Thermal shock resistance, Interfacial stress.  High modulus of elasticity - Low stress on cement.
  124. 124. LEUCITE REINFORCED PORCELAINS ( Transfer-molded ) Leucite reinforced porcelains can be broadly divided into two groups:  Pressed – • IPS Empress & IPS Empress 2 (Ivoclar) • Optec Pressable Ceramic / OPC (Jeneric/Pentron)  Non-Pressed • Optec HSP & Optec VP (Jeneric / Pentron) • Fortress (Mirage)
  125. 125. Pressed Ceramic / Injection Molded Glass Ceramic are leucite- reinforced, vacuum-pressed glass-ceramic, also referred to as Heat transfer-molded glass ceramics. Eg: IPS Empress (Ivoclar Williams); Optec (Jeneric Pentron) IPS EMPRESS (Ivoclar Williams) is a pre-cerammed, pre- coloured leucite reinforced glass-ceramic formed from the leucite system (SiO2 -AI2 O3 -K2 0) by controlled surface crystallization, subsequent process stages and heat treatment. This technique was first described by Wohlwend & Scharer; and marketed by Ivoclar (Vivadent Schaan, Liechtensein). The glass contains latent nucleating agents and controlled crystallization is used to produce leucite crystals measuring a few microns in the glass matrix. The partially pre-cerammed product of leucite-reinforced ceramic powder available in different shades is pressed into ingots and sintered. The ingots are heated in the pressing furnace until molten and then injected into the investment
  126. 126. Composition : (wt %)  SiO2 -63%  Al2 O3 -17.7%  K2 O -11.2%  Na2 O -4.6%  B2 O3 -0.6%  CeO2 -0.4%  CaO -1.6%  BaO -1.6%  TiO2 -0.2%
  127. 127. It is a type of feldspathic porcelain containing a higher concentration of leucite crystals, which increases the resistance to crack propagation. A special furnace Empress EP500 designed for this system is capable of high temperatures. The pressing furnace contains an enlarged heat dome, a pneumatic pressure system, a reducing valve, and a monometer to control the pressure. Leucite content Conventional Porcelain Dicor Glass- ceramic IPS Empress Pressable ceramic 30-35% 50-60% 80-85%
  128. 128. Brief history of the evolution of pressable ceramics : 1936 - A patented heat-press technique was first described for the construction of ceramic complete dentures. 1969 - Droge described a ceramic press technique based on the hot-press resin technique. McPhee improved Droge's technique to produce complete coverage metal-ceramic restorations that accurately duplicated occlusal surfaces. 1983 - To overcome the disadvantage of additional ceramic shrinkage during ceramming of castable glass-ceramic, a heat- pressed technique (Empress) was researched and developed by Arnold Wohlwend of the Dept. of Fixed and Removable Prosthodontics and Dental Materials at the University of Zurich, Zurich, Switzerland. Since 1986, the development has proceeded in conjunction with a dental company Ivoclar (Schaan Liechtensein)
  129. 129. Fabrication:  Lost-wax technique: The wax pattern of the proposed restoration is invested in a special flask (specially designed cylindrical crucible former) using IPS Empress special investment material (phosphate bonded).  Pressing Procedure : Following burnout (at 850°C) the crucible former is placed into the base of a specialized automated furnace (EP 500 Press furnace) that has an alumina plunger. The ceramic ingot of the selected dentinal shade is placed under the plunger and the entire assembly is preheated to 1,1000 C (at which temperature the ceramic plasticizes). When the temperature reaches 11500 C after a 20 minute holding time the plunger presses the ceramic under vacuum (0.3-0.4 MPa) into the mold, in which it is held under pneumatic pressure (for a 45-minute period) to allow complete and accurate fill of the mold.
  130. 130.  Veneering: Shade reproduction may be carried out either by the : • Staining technique : In the staining technique, the selected dentinal stain is applied and thinned to the desired consistency with glazing stains before firing and repeated until the necessary shade is achieved Individual characterization can be achieved with final stain firing. • Layering technique : In the layering technique, the dentinal core is cut back and wash fired. The latter provides an optimum bond between the dentinal core and layering material. Appropriate incisal and neutral materials are mixed with IPS Empress build-up liquid and then applied in thin layers before drying. This is repeated until the correct shape and shades are achieved. The final restoration is glazed and fired before polishing is carried out. Internal crown surfaces can be roughened by etching; silaned and bonded to tooth using resin-based luting
  131. 131. Properties : Reported flexural strengths are in the range of 160 to I80MPa. The increase in strength has been attributed to :  The pressing step which increases the density of leucite crystals.  Subsequent heat treatments which initiate growth of additional leucite crystals. Uses :  Laminate veneers and full crowns for anterior teeth  Inlays, Onlays and partial coverage crowns  Complete crowns on posterior teeth.
  132. 132. Advantages :  Lack of metal or an opaque ceramic core  Moderate flexural strength (120-180MPa range)  Excellent fit (low-shrinkage ceramic)  Improved esthetics (translucent, fluorescence)  Etchable  Less susceptible to fatigue and stress failure  Less abrasive to opposing tooth  Biocompatible material  Unlike previous glass-ceramic systems IPS Empress does not require ceramming to initiate the crystalline phase of leucite crystals (They are formed throughout the various temperature cycles)
  133. 133. Disadvantages :  Potential to fracture in posterior areas.  Need for special laboratory equipment such as pressing oven and die material (expensive)  Inability to cover the colour of a darkened tooth preparation or post and core, since the crowns are relatively translucent.  Difficulty in removing the crown and cementing medium during replacement.  Compressive strength and flexural strength lesser than metal-ceramic or glass-infiltrated (In-Ceram) crowns.
  134. 134. OPTEC (Optimal Pressable Ceramic/OPC): Optec stands for Optimal Technology. It is a type of feldspathic porcelain with increased Ieucite content designed to press restorations using leucite-reinforced ceramic in a press furnace that doubles as a conventional porcelain furnace. The manufacturer claims that the crystalline leucite particle size has been reduced with a more homogenous distribution without reducing the crystalline content and this leucite content increase has resulted in an overall increase in flexural strength of OPC (over 23,000 psi and compressive strength upto 187,320 psi). However, because of its high leucite content, it can be expected that its abrasion against natural teeth will be higher than that of conventional feldspathic porcelain. Fabrication is similar to IPS Empress
  135. 135. Uses :  Full contour restorations (inlays, veneers full crowns)  Alternately used as a core material, veneered with conventional feldspathic porcelain (similar to Optec HSP).
  136. 136. Leucite content Convention al Porcelain Dicor Glass- ceramic IPS Empress Pressable ceramic 30-35% 50-60% 80-85%
  137. 137. IPS EMPRESS 2 (Ivoclar) -Second generation of pressable materials for all-ceramic bridges. It is made from a lithium disilicate framework with an apatite layered ceramic. The glass-ceramic ingots are made from lithium silicate glass crystals with crystal content of more than 60 volume%. The apatite crystals incorporated are responsible for the improved optical properties (translucency, light scattering) which contribute to the unique chameleon effect of leucite glass- ceramic materials. IPS Empress 2 is used with special investment material, an EP500 press furnace and a fully automatic high-tech furnace. Other applications : Cosmopost and IPS Empress cosmoingot - core build-up system with the pre-fabricated zircon oxide root canal posts and the optimally coordinated ingot.
  138. 138. IPS Empress IPS Empress 2 (frame work) Flexural strength Upto 150 MPa > 400 Mpa
  139. 139. Advantages claimed by manufacturer :  High biocompatibility  Excellent fracture resistance  High radiopacity  Outstanding translucency.
  141. 141. In-Ceram Alumina In – Ceram In – Ceram Spinell In – Ceram Zirconia
  142. 142. In-Ceram: Strengthening of porcelain by incorporation of crystalline material like alumina particles is limited due to the resultant porosity in the final product. An improved high aluminous porcelain system termed In-Ceram (Vita Zahnfabrik, Bad Sackingen, Germany) was developed by a French scientist and dentist Dr. Michael Sadoun (1980) and first introduced in France in 1988. The In-Ceram Crown (Vident) process involves three basic steps :  Making an intensely dense core by slip casting of fine grained alumina particles and sintering.  The sintered alumina core is infiltrated with molten glass to yield a ceramic coping of high density and strength.  The infiltrated core is veneered with feldspathic porcelain and fired.
  143. 143. The densely packed alumina crystals limit crack propagation, while the glass infiltration eliminated residual porosity and improves flexural strength upto 2-5 times that of glass-ceramic and feldspathic porcelain. Composition: In-Ceram ceramic consists of two three- dimensional interpenetrating phases :  Alumina/ Al2 03 crystalline (Volume fraction) 99.56 wt% of with a particle size distribution averaging 3.8µm  An Infiltration glass lanthanum aluminosilicate with small amounts of sodium and calcium (Lanthanum-decreases the viscosity of the glass to assist infiltration and increases its refractive index to improve translucency)
  144. 144. Fabrication stages :  Slip casting  Glass infiltration  Veneering of core Slip casting : A slip is a suspension of fine insoluble particles in a liquid. Slip casting is the art or science of preparing stable suspensions and forming ware by building up a solid layer on the surface of a porous mold that sucks up the liquid phase by means of capillary forces (Kingery, 1958). Slip casting is an ancient process used to make common objects such as beer steins, where a much more watery slip (a dispersion of alumina particles in water) is poured into a porous split mold (usually Plaster Of Paris). Slip casting was also used for the fabrication of ceramic tableware. Sadoun (1989) refined the slip casting technique to produce
  145. 145. Slip casting for In-Ceram restorations :  A special ultrasonic device (In-Ceram Vitasonic II) is used for the preparation of the slip. Liquid (water), fine grained (1- 5um) alumina powder and an additive are combined and stirred under ultrasonic agitation until a homogenous mass with so-called rheopex properties (when a liquid mass stiffens under sudden pressure) is achieved.  The slip is painted on a special plaster model made of porous refractory matrix (In-Ceram Special Plaster, Vita Zahnfabrik) needed to compensate for the sintering shrinkage of the slip casting (The slip is applied with an acrylic brush in quick strokes, so that previously applied masses do not dry).  As the liquid from the slip cast is absorbed into the die by capillary action, additional layers are added (0.5 to 0.7mm thick) causing the porcelain particles to aggregate and condense tightly forming a dense layer.
  146. 146.  The mass can be cut with a scalpel, so that the framework is shaped roughly before the first firing.  The alumina layer is allowed to dry (30 mins), and a stabilizer is applied to the frame-work, followed by sintering (10 hour firing cycle of upto 1120 0 C) in a special furnace (In- Ceramat, Vita Zahnfabrik) to produce an organized microstructure with 0.3% sintering shrinkage. The sintered alumina particles in the coping are partially fused at their grain boundaries, hence the coping is fragile and porous in nature.  The plaster shrinks during sintering, so that the sintered frameworks are easily removed from the die.
  147. 147. Glass – infiltration : A specially formulated low-fusing glass-infiltrate (lanthanum glass) powder of appropriate shade and matching thermal expansion is mixed with distilled water. The frameworks are set on a platinum-gold foil (Pt-95; Au-5) and the glass-water slurry is amply applied (to avoid air impactions) over the external surface of the porous substructure. The infiltration firing is performed for 4 to 6 hours at 11000 C (in the In-Ceramat furnace), depending on the size of the restoration (number of units). The glass infiltrate melts at 800°C and at 1100°C the molten glass infiltrates / diffuses through the interstitial spaces of the porus alumina core by capillary action and encapsulates the fine grain alumina particles. This infiltration firing with glass not only confers the selected shade to the core, it also increases the strength of the core to about 20 times its original strength and flexural strength of upto 446 Mpa have been
  148. 148. The plaster (gypsum die) shrinks during sintering so the glass-infiltrated coping can be easily removed from the die. Excess glass is removed by sandblasting (35-50um corundum for 3-6 hrs.) and grinding with diamond stones. Another firing (10 mins at 960°C) is necessary to check for excess glass, which would have to be removed by blasting.
  149. 149. Veneering of core: Aluminous veneering porcelain (Vitadur N, Vident) of the required shade is applied by conventional powder- slurry method. Resistance to devitrification during repeated firings and matching thermal expansion to pure alumina makes aluminous porcelain suitable for veneering.  Final firing is followed by adjustments and glazing of external surface.  The internal surface is sandblasted (with 50µ A12 O3 ) since the density of In-Ceram core makes conventional methods of etching with HF acid ineffective for bonding with a resin-cement (eg: Panavia 21 TC). The final In-Ceram structure consists of two 3-dimensionally interpenetrating phases :  Alumina /A12 O3 (crystalline phase)  Glassy phase
  150. 150. Strength: The densely packed crystallin.e particles (70% alumina) limit crack propagation and prevent fracture. The flexure strength is extremely high in the 450 MPa range (the strongest all-ceramic dental restoration presently available). Reports from studies have shown that though the compressive strength of In-Ceram lies between that of IPS Empress pressable glass-ceramic and metal-ceramic restorations, its fracture resistance did not differ significantly from the metal- ceramic restorations.
  151. 151. Colour: The final colour of the In-Ceram restorations is generally influenced by the colour of the alumina core, which tends to be opaque. The colourants used generally consist of transitional metal ions incorporated into the glass structure itself. However, in the spinel variety, the core is more transparent and its corresponding infiltration glass is slightly tinted. Uses:  Single anterior & posterior crowns  Anterior 3-unit FPD's
  152. 152. Tvpes of In-Ceram Core Material:  Alumina -reinforced: In-Ceram Alumina  Spinell ceramics (magnesium aluminous spinell): In- Ceram Spinell  Zirconium -oxide reinforced: In-Ceram Zirconia  Copy-milled In-Ceram Alumina
  153. 153. Advantage :  Minimal firing shrinkage, hence an accurate fit.  High flexure strengths (almost 3 times of ordinary porcelain) makes the material suitable even for multiple-unit bridges.  Aluminous core being opaque can be used to cover darkened teeth or post/ core.  Wear of opposing teeth is lesser than with conventional porcelains.  Improved esthetics due to lack of metal as substructure.  Biocompatible, diminished plaque accumulation, biochemical stability.
  154. 154. Disadvantages :  Requires specialized equipment to fabricate the restoration, hence laboratory expense is more.  Poor optical properties or esthetics (opaque alumina core reduces the translucency of the final restoration).  Incapability of being etched with HF acid, hence inability to create micromechanical retentive surface on the internal aspect of crown and difficulty in removing the In-Ceram crown and cementing medium when replacement is necessary.  Slip casting is a complex technique and requires considerable practice.  Requires considerable reduction of tooth surface all over for adequate thickness of restoration.  Insufficient long-term results to justify the
  155. 155. In-Ceram Spinell (Vita Zahnfabrik) Improvement in optical properties can be done by modification of the slip. Incorporating magnesium aluminate (Mg A1204) results in improved optical properties characterized by increased translucency with about 25% reduction in flexural strength. Spinel or Magnesium aluminate (Mg A12 O4 ) is a composition containing Al2 O3 and Mg2 O (a natural oxide of Mg2+ AI3+ ). Fabrication: similar to In-Ceram crowns
  156. 156. Advantage:  Strength of Spinel I renders greater strength characteristics.  Spinell has extended uses: Inlay / Onlay, ceramic core material and even Veneers. Disadvantage: Incapable to be etched by HF. (The Bateman Etch Retention Svstem (BERS) is suggested to overcome this disadvantage It consists of incorporating plastic chips (50µ - 300µ diameter) on the fitting or internal surface of In-Ceram during their fabrication, which are subsequently burnt out leaving behind a roughened surface)
  157. 157. In-Ceram Zirconia (VitaZahnfabrik) The In-Ceram technique was expanded to include its modified form with zirconia. Using a mixture of zirconium oxide/ aluminium oxide as a framework material, the physical properties were improved without altering the proven working procedure. The In-Ceram Zirconia material is said to feature a high flexural strength (2 to 3 times the impact capacity and 1.4 times the stability as the ln-Ceram Alumina), excellent marginal accuracy and bicompatibility. According to the manufacturer this technique allows fabrication of all-ceramic bridges even in the posterior molar area. Disadvantage: Poor esthetics due to increased opacity.
  158. 158. Procera (Sandvick) It has alumina content more than 99.9% (flexural strength upto 650 Mpa) has been used. in :  Ceramic core for single tooth replacement (Cera One, Branemark system, Nobel Biocare) Ceramic abutment for implant supported single crowns (CerAdapt, Branemark system, Nobel Biocare).
  159. 159. Copv-milled In-Ceram-Alumina: The In-Ceram Alumina (Vita Zahnfabrik) and its fabrication process was adapted to the Celay Copy-milling method (Mikrona) as an alternative to the slip-casting technique. The Celay system is a manually guided copy-milling process in which a resin prototype is surface traced and copied in ceramic. The ceramic substructures are prefabricated blanks made of pre-sintered alumina ceramic (Celay Alumina Banks, Vita Zahnfabrik). In- Ceram restorations made with this technique present a 10% higher flexural strength (about 500 MPa) than the conventional In-Ceram restorations. (Fabrication of Copy milled alumina frameworks with the Celay system, requires a modification of the milling machine by using the Celay Crown-Kit (Mikrona AG) which contains an altered metallic vise, an improved set of scanning and milling instruments together with a basic instrument set for the
  160. 160. Uses :  Inlay / Onlay  Veneers  Crown / Bridge framework  Post & core
  161. 161. Procedure :  Die spacer (2 layers) are applied on the working dies and the prototype resin copings are directly modeled using light-activated resin (Celay Tech, ESPE, Seefeed, Germany) equivalent in thickness (incisal- 0.7mm, axial wall-0.5mm) to that of conventionally produced In-Ceram alumina cores.  The prototype structures are scanned using the modified Celay system and simultaneously milled from an industrially sintered alumina blank (Vita Celay Alumina Blank, Vita Zahnfabrik).  The milled units are glass-infiltrated. Because of the higher capillary effect of the alumina blanks, the glass infiltration is shortened to 40 minutes and followed by veneering with aluminous porcelain (Vitadur Alpha, Vita Zahnfabrik) as in conventional In-Ceram