Dental ceramics part II

ALL Ceramics in detail

1. DENTAL CERAMICS Part II Dr. Kriti Trehan MDS I

2. Contents Introduction Advantages and disadvantages Conventional ceramics Castaable ceramics Pressable ceramics Infiltrated ceramics Machinable ceramics References

3. Currently available all-ceramics can be broadly categorized according to their method of fabrication : Conventional (powder – slurry) ceramics Castable ceramics Pressable ceramics Infiltrated ceramics Machinable ceramics “ All-Ceramic” refers to – Any restorative material composed exclusively of ceramic, such as feldspathic porcelain, glass ceramic,alumina core systems and certain combination of these materials. ( J.Esth Dent 1997, 9 (2): 86).

4. : Advantages of all ceramic Most life like and esthetically pleasing restoration. It is translucent, color stable. If constructed over a uniformly reduced and balanced preparation, it has a long life expectancy in most patients. The advent of vacuum firing has reduced bubbles, producing a fine textured restoration with improved translucency and increased impact strength.

5. Porcelain is biologically acceptable, and well tolerated by the soft tissues. Porcelain crowns cemented on natural abutments and those cemented on artificial supports have the same incidence of fracture; therefore, a porcelain crown can be successfully used after a cast-metal post and core has been placed on a non-vital tooth.

6. Disadvantages of all ceramic Cost and time Brittlesness of ceramics Wear of opposing dentition Low repair potential

7. Alumina – Reinforced porcelain ( Aluminous Porcelain ) Hi-Ceram Vitadur – N core Magnesia – Reinforced porcelain ( magnesia core ceramics ) Leucite Reinforced (Non-pressed) Optec HSP Optec VP CONVENTIONAL CERAMICS

8. The high-strength ceramic core was first introduced to dentistry by McLean and Hughes in 1965. It is composed of aluminum oxide (alumina) crystals dispersed in a glassy matrix. Alumina has a high tensile strength, fracture toughness and hardness. Examples : Hi-Ceram (Vident), Vitadur – N core (Vident) Aluminous core ceramics

9. One method of producing aluminous porcelain crowns was to form a tin oxide coating on platinum foil.

10. Advantages: Withstand torque better than conventional porcelains with fracture rate of slightly less than 0.5%. As Abramowsky states, pure alumina is 6 times stronger than standard porcelains. By combining an alumina core with standard porcelain, the restoration is twice the strength of porcelain alone. Low thermal conductivity. During processing, alumina and porcelain unite by a chemical bond, so there is practically no problem in adhesion. Good color consistency. Provided the porcelain‘s maturing temperature is not exceeded, the crowns may be fired 3 or 4 times without color loss.

11. Hi- ceram Dispersion Strengthened Core. Similar to traditional Alumina Core, with increased alumina. Fired Directly On The Refractory Die - Rough Surface Which aids in Retention. Modifications

12. Feldspathic porcelain higher leucite crystal content. The leucite and glassy components are fused during the baking process at 1020ºC. Advantages: More esthetic due to a more translucent core. Greater strength. No special processing equipment required. Leucite reinforced porcelain

13. Drawbacks: 1. Increased leucite content contributes to the relatively high in vitro wear of opposing teeth. 2. Potential to fracture in posterior teeth. 3. Potential marginal inaccuracy Uses : Inlays Onlays Low stress crowns.

14. 1968 - W.T. MacCulloch realised the usefulness of glass ceramics and proposed its use for dental restorative purposes. 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. CASTABLE CERAMICS Glass-ceramics are polycrystalline materials developed for application by casting procedures using the lost wax technique, hence referred to as “ castable ceramic”.

15.       ( SiO 2 K 2 MgOA1 2 O 3 ZrO 2 ) Dicor (CaOMgOP 2 O 5 SiO 2 ) CeraPearl ( KyoceraBioceram ) Castable Dental Glass-Ceramics Fluoromicas Apatite Glass-Ceramic OtherGlass -Ceramics Based on Lithia b) Calcium phosphate

16. The first commercially available castable glass-ceramic. Developed by ‘The Corning Glass Works’ (Corning N.Y.) and marketed by Dentsply International ( Yord , PA,U.S.A). Dicor is a castable polycrystalline fluorine containing tetrasilicic mica glass-ceramic (55 vol %) material. Dicor

17. 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. Ceramming : The cast glass material is subject to a single-step heat treatment called “ Ceramming ” to produce controlled crystallization by internal nucleation and crystal growth of microscopic plate like mica crystals within the glass matrix.

18. Cast glass ceramic is composed of: Tetrasilicic flouromica crystals (crystalline) - 55% by volume. Glass matrix (non-crystalline) - 45% by volume. The microstructure after ceramming consists of multiple interlocking crystals of tetrasilicic flouromica approximately 1 μ m thick and 5-6mm in diameter. On the surface of the cerammed glass are ‘ Enstatite crystals’ which occur through fluorine depletion.

19. The crystals function in following ways : Improved strength : Interlocking of randomly oriented small plate-like mica crystals increases the resistance to fracture. Improved esthetics : The refractive index of the mica crystals is matched to that of the surrounding glass phase thus reducing light scatter (as in aluminous 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 porcelain.

20. Wax pattern Spruing Investing Burnout Divesting Cast glass coping Ceramming 1750 for 1\2hr 450 for 1\2 hr Centrifugal casting 2600 f

21. Ceramming Ceramming oven Crystallised glass coping Conventional porcelain application & Firing Finished crown Cerramming done in temperature- 650-1075 C for 1½ hrs and sustained for 6hrs in order to form tetra silicic flouro mica crystals

22. ADVANTAGES: Excellent esthetics resulting from Chameleon effect. 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 biocompatibility with surrounding tissues. Low thermal conductivity.

23. DISADVANTAGES: Requires special and expensive equipments .   Laboratory studies for use as veneers and inlays, failure rates as high as 8% in the posterior region. The original cast form was colorless and prostheses had to be colored by the application of a thin layer of shading porcelain.

24. INDICATIONS: Used for anterior single crown (low stress area) Used in situations where high translucency is required. CONTRAINDICATIONS: Not used as posterior crowns. Not used in high stress bearing areas.

25. 70% Tetrasilicic fluromica crystal. Particle size 1-5 microns, volume 65 %. Provided as CAD/CAM blanks No longer sold Disadvantages Limited use in low stress bearing areas Unable to color internally Dicor MGC

26. 1985 - Sumiya Hobo & Iwata developed a castable apatite glass-ceramic which was commercially available as Cera Pearl (Kyocera Bioceram , Japan). CERA PEARL (Kyocera San Diego, CA): contains a glass powder distributed in a vitreous or non-crystalline state. Castable apatite glass ceramic

27. Composition : Approximately (By weight) Calcium oxide ( CaO ) -45%  Phosphorus Pentoxide (P 2 O 5 ) -15% Aids in glass formation. Magnesium oxide ( MgO ) -5% Decreases the viscosity ( antiflux )  Silicon dioxide (SiO2)- 35% Forms the glass matrix. Other - Trace elements and nucleating agents. Chemistry : Apatite Glass-Ceramic Molten glass CaPO 4 (CaO-P 2 O 5 -MgO-SiO 2 ) Amorphous 1460°C melting 1510°C casting

28. CaPO 4 Oxyapatite Hydroxyapatite ( Amorphous) ( Crystalline) ( Crystalline ) Ca 10 (PO 4 ) 8 20H Strength is dependent on these crystals and the bond between the crystals and the non-crystalline inorganic matrix . 1460  C Ceramming Exposure to moisture

29. Desirable characteristics of Apatite Ceramics Cerapearl is similar to natural enamel in composition, density, refractive index, thermal conductivity, coefficient of thermal expansion and hardness. Bonding to tooth structure : 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).

30. 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. Favorable soft tissue response .

31. 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.

32. 1.Shrink free ceramics: Cerestore Al- ceram 2.Leucite reinforced glass ceramics: IPS empress Optec/OPC 3.Lithia reinforced glass ceramic: IPS empress 2 OPC 3G PRESSABLE CERAMICS

33. 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 Cerestore system 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 Alumina Ceramics

34. Shrink-free ceramics were marketed as two generation of materials under the commercial names : Ø       Cerestore (Johnson & Johnson. NJ, USA) Al-Ceram ( Innotek Dental Corp, USA) Chemistry : The shrink free ceramic material essentially consists of Al 2 O 3 and MgO mixed with 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.

35. 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 aluminosilicate formed reacts with the incorporated magnesia to form spinel , which is also one of the strongest ceramic oxides . During firing from 900 to 1300°C, the glass frit takes MgO and Al 2 O 3 into solution subsequently precipitates the spinel phase.

36. 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 ).

37. Low thermal conductivity ; thus reduced thermal sensitivity. Low coefficient of thermal expansion and high modulus of elasticity results in protection of cement seal. Disadvantages : Complexity of the fabrication process. Need for specialized laboratory equipment (Transfer molding process) and high cost . .

38.   Inadequate flexural strength (89MPa) compared to the metal-ceramic restorations.   Poor abrasion resistance, hence not recommended in patients with heavy bruxism or inadequate clearance. 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 ).

39. Leucite reinforced porcelains can be broadly divided into: ·         IPS Empress ( Ivoclar Williams) ·         Optec Pressable Ceramic / OPC ( Jeneric / Pentron ) Leucite reinforced porcelains (transfer moulded ) Pressed Ceramic / Injection Molded Glass Ceramic are leucite - reinforced,vacuum -pressed glass-ceramic, also referred to as Heat transfer-molded glass ceramics.

40. IPS EMPRESS ( Ivoclar Williams ) is a pre- cerammed , pre- coloured leucite reinforced glass-ceramic formed from the leucite system (SiO 2 -AI 2 O 3 -K 2 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.

41. It is a type of feldspathic porcelain containing a higher concentration of leucite crystals, which increases the resistance to crack propagation. Leucite content Conventional Porcelain Dicor Glass- ceramic IPS Empress Pressable ceramic 30-35% 50-60% 80-85%

42. 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.

43. The crucible former placed into automated furnace that has an alumina plunger. Fabrication Wax pattern is invested in a special flask

44.   Uses :    Laminate veneers and full crowns for anterior teeth    Inlays, Onlays and partial coverage crowns

45. Advantages :   Lack of metal or an opaque ceramic core 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).

46. 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. Compressive strength and flexural strength lesser than metal-ceramic or glass-infiltrated (In-Ceram) crowns.

47. IPS Empress 2 ( Ivoclar Vivadent ) and Optec OPC 3G ( Pentron Laboratory Technologies) contain approximately 65% to 70% by volume of lithia disilicate (Li2O•2SiO2) as the principal crystal phase. The lithia disilicate materials used as glass-ceramics have a narrow sintering range, which makes processing of ceramic prostheses very technique sensitive. Composition :70% lithium disilicate 30% glass. It is fairly translucent but somewhat more opaque with a stronger core than leucite -based glass-ceramic. Lithia reinforced porcelains

48. Uses : Anterior and posterior crowns Anterior three unit bridges Although the core ceramic fracture resistance is moderately high, veneered prostheses have been reported to be susceptible to chipping, which may require replacement

49. Advantages: Improved fracture resistance. Very high chemical resistance of both framework and layering ceramics. High translucency. Outstanding light optical properties due to apatite (also a component of natural teeth). Wear behavior similar to that of natural enamel. Ingots available in the most popular Chromoscope shades. Excellent aesthetic appearance.

50. IPS e.max

51. INDICATIONS Thin veneers (0.3 mm) Inlays , onlays , occlusal veneers Crowns in the anterior and posterior region Bridges in the anterior and premolar region Implant superstructures Hybrid abutments and abutment crowns

52. INFILTRATED CERAMICS In-Ceram Alumina In – Ceram Spinell In -Ceram Zirconia

53. 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. Developed by a French scientist and dentist Dr. Michael Sadoun (1980) and first introduced in France in 1988 . In-Ceram Alumina

54. Duplication In-Ceram refractory dies In-Ceram application Al 2 O 3 slip 10 hrs 1120 c- 2hrs vita inceramat Working model Glass infiltration 4hrs 1100c Shrinkage of dies

55. Application of body and incisal porcelain Postoperative veiw of In-Ceram crowns Finished crowns Application of body and incisal porcelain Postoperative veiw of In-Ceram crowns Finished In-Ceram copings (Air abraded) Finished crowns Preoperative veiw

56. 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 : Ø   Alumina / Al 2 3 crystalline (Volume fraction) 99.56 wt% of with a particle size distribution averaging 3.8  m An Infiltration glass lanthanum aluminosilicate with small amounts of sodium and calcium.

57. Advantages : 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. Uses: Single anterior & posterior crowns Anterior 3-unit FPD's

58. 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). Slip casting is a complex technique and requires considerable practice. Requires considerable reduction of tooth surface all over for adequate thickness of restoration.

59. The primary difference is a change in composition to produce a more translucent core. The porous core is fabricated from a magnesium alumina powder after sintering.This type of material has a specific crystalline structure referred to as ―SPINELL‖. The porous spinell is secondarily infiltrated with a low viscosity, lanthanum aluminosilicate glass, which produces a more translucent substructure upon which Vitadur Alpha is veneered to form the final restoration. In-Ceram Spinell ( VitaZahnfabrik )

60. INDICATIONS: Anterior crowns, particularly In clinical situations where maximum translucency is needed. CONTRAINDICATIONS: Posterior restorations. Anterior and posterior FPDs. In discolored preparations and cast posts as the level of translucency is excessive and leads to an overly glassy low value appearance.

61. Advantage : The translucency closely matches that of dentin and is twice more than Inceram alumina. 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 (50  - 300  diameter) on the fitting or internal surface of In-Ceram during their fabrication, which are subsequently burnt out leaving behind a roughened surface).

62. A second-generation material based on INCERAM fabrication technique. Pure ZrO2 has a monoclinic crystal structure at room temperature and transforms to tetragonal and cubic zirconia at elevated temperatures. Inceram zirconia Zirconia is a nonmetal with an extremely low thermal conductivity—about 20% as high as that of alumina (Al2O3). It is chemically inert and highly corrosion resistant.

63. Structural expansion and high tensile stresses causes zirconia to crack during cooling from the processing temperatures. Stabilizing oxides such as magnesium oxide ( MgO ), yttrium oxide (Y2O3), calcium oxide ( CaO ), and cerium oxide (Ce2O3) are added to zirconia to provide stability. The “ transformation toughening ” mechanism of crack shielding results from the controlled transformation of the metastable tetragonal phase to the stable monoclinic phase next to the crack tip.

64. In this process a 3% expansion by volume of the ZrO2 crystals or precipitates occurs that places the crack under a state of compressive stress and crack progression is arrested. Because of this strengthening and toughening mechanism, the yttria -stabilized zirconia ceramic is sometimes referred to as “ ceramic steel .”

65. Disadvantages The risk for catastrophic wear of opposing enamel and dental restorations is one of the major potential challenges to the effective, safe use of solid zirconia prostheses. Difficulty in adjusting occlusion when significant premature contacts are present. The cutting difficulty The heat generated in removing defective crowns or when making an endodontic access opening with diamond burs.

66. From 1998 , machined ceramics came into being. There are two major systems for the fabrication of this technique. Digital systems CAD CAM technology 2. Analogous systems Copy milling / grinding technique Erosive techniques MACHINABLE CERAMICS

67. Development of CAD-CAM systems for the dental profession began in the 1970‘s with Duret in France, Altschuler in the US and Mormann and Brandestini in Switzerland. CAD-CAM ceramic prostheses can be produced either as monolithic lithia disilicate glass-ceramic or zirconia ceramic structures or as bilayer structures made from milled copings and layered manually, by hot pressing, or by fusing a CAM-produced veneer to the framework (CAD-0n method). CAD-CAM prostheses can be produced either by industrial milling processes or by chair-side milling units.

68. Materials for CAD/CAM processing The following materials can normally be processed on dental CAD/CAM devices: Silica based ceramics Grindable silica based ceramic blocks are offered by several CAD/CAM systems for the production of inlays, onlays , veneers, partial crowns and full crowns. In addition to monochromatic blocks, various manufacturers now offer blanks with multicoloured layers [ Vitablocs TriLuxe (Vita), IPS Empress CAD Multi ( IvoclarVivadent )], for the purpose of full anatomical crowns.

69. Due to their higher stability values, lithium disilicate ceramic blocks are particularly important in this group; They can be used for full anatomical anterior and posterior crowns, for copings in the anterior and posterior region and for three-unit FPD frameworks in the anterior region due to their high mechanical stability of 360 MPa . Glass ceramics are particularly well suited to chairside application as a result of their translucent characteristics, similar to that of natural tooth structure; they provide aesthetically pleasing results even without veneering.

70. 2. Infiltration ceramics Grindable blocks of infiltration ceramics are processed in porous, chalky condition and then infiltrated with lanthanum glass. All blanks for infiltration ceramics originate from the Vita In-Ceram system (Vita) and are offered in three variations: Vita In-Ceram Alumina (Al2 O3 ):

71. Vita In-Ceram Zirconia (70% Al2 O3, 30% ZrO2 ): VITA In-Ceram Spinell (MgAl2 O4 ):

72. 3. Oxide high performance ceramics At present, aluminum oxide and zirconium oxide are offered as blocks for CAD/CAM technology. Aluminum Oxide is indicated in the case of crown copings in the anterior and posterior area, primary crowns and three-unit anterior FPD frameworks. The ground frames can be individually stained in several colours with Vita In-Ceram AL Coloring Liquid. Examples of grindable aluminum oxide blocks: In-Ceram AL Block (Vita), inCoris Al ( Sirona ) available in an ivory-like colour (Color F 0.7).

73. Yttrium stabilised zirconium oxide (ZrO2 , Y-TZP) Zirconium dioxide is a high-performance oxide ceramic with excellent mechanical characteristics. Its high flexural strength and fracture toughness compared with other dental ceramics offer the possibility of using this material as framework material for crowns and FPDs, and, in appropriate indications, for individual implant abutments. Examples of Zirconium oxide blocks: Lava Frame (3M ESPE), Cercon Smart Ceramics ( DeguDent ), Everest ZS und ZH ( KaVo ), inCoris Zr ( Sirona ), In-Ceram YZ (Vita), zerion ( etkon ) and Zeno Zr (Wieland- Imes )

74. ADVANTAGES Less chairside time Reduced porosity & greater strength Single appointment Decreases fabrication time by 90% DISADVANTAGES Cost Technique sensitive Inability to build layers of porcelain

75. The first commercially available CAD/CAM system has been CEREC, developed by Mormann and Brandestini . Since its introduction to the dental field in 1986 as the CEREC 1, this system has evolved through a series of software and hardware upgrades up to the CEREC 3D. Cerec System

76. The CEREC 1 System First introduced in 1986. It consisted of a mobile unit containing : A small camera A computer with scan. 3-axis-of rotation milling machine- water-pressure driven. Clinical shortcomings: Occlusal anatomy had to be created by the clinician Inaccuracy of fit or large interfacial gaps Clinical fracture Relatively poor esthetics

77. CEREC 2 system The major changes include : Enlargement of the grinding unit from 3 axes to 6 axes. Upgrading of the software allows machining of the occlusal surfaces and the complex machining of the floor parts. CEREC 3 system Different parts could be magnified in detail more finer details noted. Disadvantage: not capable of producing margins of restoration.

78. CEREC 3-D System Marginal fit good 3 dimensionally movable camera The clinical advantages of the Cerec system :   Quality-controlled ceramic porcelain can be placed in one visit.   Translucency and color of porcelain very closely approximate the natural tooth.    Further , the quality of the ceramic porcelain is not changed by the variations that may occur during processing in dental laboratories .

79. The prefabricated ceramic is wear resistant. The optimized structure of the ceramic enables optimal polishability of the material and low abrasion of the opposing tooth. A tight marginal fit is provided by the adhesive system used between the etched ceramic porcelain and enamel surfaces.

80. The Celay System ( Mikrona AG, Spreintenbach , Switzerland) became first commercially available in 1992. It is a high precision,manually operated copy milling machine This system was originally designed and intended for use in the dental laboratory, however it may also be used at the chairside . Celay System

81. Milling instruments Block being milled Composite resin pro inlay Pro inlay being scanned

82. Finished restoration Milled Restoration

83. 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.

84. The Procera System (Nobel Biocare , Gioteborg , Sweden) 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. Procera System

85. 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.

86. 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. 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).

87. ADVANTAGES Flexural strength 687mpa . Procera coping is translucent , thus will not allow any staining of the underlying dentin Occulsal surface will not damage the opposing natural tooth Aluminum oxide coping material does not show any leakage or dissolution of aluminum at any of the pH levels

88. Cercon and lava zirconia core ceramics FABRICATION: Tooth preparation Impression made Wax pattern (0.8 mm)made on model Anchored on to the Cercon Brain A presintered zirconia blank is attached on to the other side of the brain unit Unit activated..pattern scanned

89. Milled prosthesis then removed from unit and placed in the Cercon furnace (1350 ºc for 6 hours) Trimming

90. Finished ceramic core framework After veneering Greatest potential fracture toughness and flexural strength(>900 MPa )

91. Contraindications: Severe bruxism Extensive wear of tooth structure or restorations Excessive bite-force capability Previous history of all-ceramic inlay or crown fractures . Principles governing the selection of dental ceramics

92. Six criteria should be considered to minimize the risks of poor esthetics, clinical failures, remakes, and possible disagreements and misunderstandings between dentists, patients, technicians, and manufacturers: . The dentist should not consider all-ceramic crowns for patients with evidence of extreme bruxism , clenching, or malocclusion. In this case, metal-ceramic or all metal prostheses should be used. The experience of the laboratory technician should be extensive and only technicians who demonstrate meticulous attention to detail should be selected. Specific patient would yield more predictable outcomes and longevity than an all ceramic prosthesis.

93. 4. Use all-ceramic crowns when the adjacent teeth exhibit a high degree of translucency. 5. Informed consent must be obtained from the patient, preferably in writing. 6. The dentist should be skillful and be able to take perfect impressions derived from smooth preparations free of undercuts with continuous, well-defined margins, and with adequate total tooth reduction

94. Bonding of resin ceramic to dental ceramics

95. Phillips science of dental materials –First South Asia edition. Craig’s Restorative dental materials –13th edition. Qualtrough A, Piddock V.Dental ceramics:whats new?Dent Update 2002; 29: 25–33. Guess et al.All -Ceramic Systems: Laboratory and Clinical Performance Dent Clin N Am 2011 ;55:333–352 References

96. Freedman M, Quinn F, Sullivan MO.Single unit CAD/CAM restorations: a literature review.JIDA 2007; 53(1):38-45 . Jones D. W. - Developments in Dental ceramics – JDR 1999( Abst );44(2):61. Marc.A.Rosenblum , Allan.Schulman - A Review of All-Ceramic Restorations. – JADA 1997;128:297-307. J. Robert Kelly, I. Nishimura, S. D. Campbell - Ceramics in dentistry : Historical roots and current perspectives - JPD1996;75(1):18-32. J. K. Dong, H. Luthy , A. Wohlwend , P. Scharer - Heat Pressed Ceramics : Technology and Strength – IJP 1992;5(1):9-16.