RECENT ADVANCES IN DENTAL CERAMICS.pptx

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1. GOOD MORNING

2. RECENT ADVANCES IN DENTAL CERAMICS R. PRIYA DARSHINI IST YEAR MDS

3. CONTENTS Introduction Definition Composition Properties of dental porcelains Classification - According to type - According to use - According to processing method - According to firing temperature - According to substructure material - According to microstructure

4. Recent advances in ceramics - According to processing technique and their major crystalline phase Sintered porcelains - Leucite - reinforced Feldspathic porcelain Alumina based porcelain Magnesia based core porcelain Zirconia based porcelain Glass ceramics Conclusion References Slip cast ceramics – Alumina based (in- ceram ) Hot pressed, injection-molded ceramics – L eucite -based S pinel –based Machinable ceramics – Cerec system Celay system Procera system

5. Introduction Dental ceramics : An inorganic compound with non-metallic properties typically consisting of oxygen and one or more metallic or semimetallic elements ( eg.,Al , Ca, Li, Mg, K, Si, Na, Ti, Zr ) that is formulated to produce the whole or part of a ceramic based dental prosthesis. Over the past forty years, the technological evolution of ceramics for dental applications has been going on, as new materials and processing techniques are steadily being introduced

6. CERAMICS: Compounds of one or more metals with a nonmetallic element, usually oxygen. They are formed of chemical and biochemical stable substances that are strong, hard, brittle, and inert nonconductors of thermal and electrical energy ; the art of making porcelain dental restorations (GPT- 8) PORCELAIN: a ceramic material formed of infusible elements joined by lower fusing materials. Most dental porcelains are glasses and are used in the fabrication of teeth for dentures, pontics and facings, metal ceramic restorations including fixed dental prostheses, as well as all-ceramic restorations such as crowns, laminate veneers, inlays, onlays , and other restorations. (GPT-8) DEFINITIONS :

7. Composition Feldspar: Mixture of potassium and aluminium silicates soda tends to lower fusion temperature potash increases the viscosity of molten glass Kaolin (china clay) : hydrated aluminium silicate, acts as binder Silica (in the form of quartz, and remains as a fine dispersion after firing) Aluminum oxide

8. Conventional dental porcelain is a ceramic based on a network of silica and potash feldspar or Soda feldspar or both. Pigments opacifiers and glasses are added to control the fusion temperature, sintering temperature, thermal contraction coefficient and solubility. Boric oxide – ceramic flux included in glass to lower softening temperature. It acts as a glass former.

9. Silica – It is a polymorphic material and can exist in 4 different forms. Crystalline quartz Crystalline cristobalite Crystalline tridymite Non crystalline fused silica Hard ,infusible and stable material. Acts as a refractory skeleton and provides strength and hardness to porcelain during firing

10. Glass modifiers or fluxes : Silica has high sintering temperature and low thermal coefficient of contraction. So, veneering of ceramic to metal alloy is difficult , so, glass modifiers are added. These decreases viscosity, lower sintering temperature and increase thermal expansion These are also added to produce dental porcelain with different firing temperatures. Medium and high fusing – production of denture teeth Low and ultra low fusing – crown and bridges Some ultra low fusing porcelains – titanium alloys

11. PROPERTIES OF DENTAL CERAMICS Chemically stable Excellent esthetics Thermal conductivity and coefficient of thermal expansion similar to enamel and dentin Flexural strength – combination of compressive, tensile and shear strength. Glazed porelain stronger than ground porcelain. Compressive strength – high (350- 550 MPa ) Tensile strength – low (20-60 Mpa ) results in surface micro cracks. Shear strength – low – (110 Mpa ) due to lack of ductility Richard Van Noort ; Introduction To Dental Materials

12. CLASSIFICATION OF CERAMICS By type : F eldspathic porcelain Aluminous porcelain Leucite reinforced porcelain. Glass infiltrated alumina Glass infiltered spinel Glass infiltrated zirconia Glass ceramic

13. CLASSIFICATION Based on use Denture teeth Metal ceramic Veneers, inlays, crowns, anterior and posterior bridges Based on method Sintering Casting Machining

14. By their firing temperature High fusing -1300°C Medium fusing ---1100 - 1300° C Low fusing--850 - 1100° Ultralow fusing < 850 °C Air fired i.e. at atmospheric pressure Vacuum fired i.e. at reduced pressure By substructure material Cast metal Swaged metal Glass ceramic CAD CAM porcelain Sintered ceramic core

15. By their area of application : Opaque porcelain Body dentine porcelain Gingival dentin porcelain Overlay enamel Incisal enamel According to microstructure Glass Cystalline Crystal containing glass

16. Classification 3 main divisions to the spectrum of dental ceramics : 1) predominantly glassy materials 2) particle filled glasses 3) polycrystalline ceramics Highly esthetic dental ceramics – predominantly glassy Higher strength substructure ceramics – generally crystalline History of development of substructure ceramics involves an increase in crystalline content to fully polycrystalline. J.Robert Kelly, Dent Clin N Am 48(2004) 513-530

17. Predominantly GLASSY CERAMICS Mimics the optical properties of enamel and dentin. Structure – amorphous or without form. Glasses in dental ceramics derive principally from a group of mined minerals called FELDSPAR and are based on SILICA(silicon oxide) and ALUMINA( aluminium oxide) – hence FELDSPATHIC PORCELAINS belong to the family called ALUMINIOSILICATE GLASSES. Glasses based on feldspar are 1) resistant to crystallization during firing 2) have long firing ranges 3) biocompatible.

18. PARTICLE-FILLED GLASSES Filler particles added to the base glass composition to improve mechanical properties and to control optical effects such as opalesence , color, and opacity. These fillers are usually crystalline but can also be particles of higher melting glass.

19. First fillers to be used – LEUCITE Leucite used in dispersion strengthening at conc of 40-55 mass% is much higher than needed for metal ceramics. Beyond thermal expansion/contraction behaviour , 2 major benefits to leucite as a filler are – 1) refractive index of leucite is close to that of feldspathic glasses, an important match for maintaining some translucency. 2) etches at a much faster rate than the base glass, and it is this “selective etching” that creates a myriad of tiny features for resin cements to enter, creating a good micromechanical bond.

20. Moderate strength increases can also be achieved with appropriate fillers added and uniformly dispersed throughout the glass, a technique termed “Dispersion Strengthening”. First successful strengthened substructure ceramic was made of feldspathic glass filled with particles of Aluminium Oxide.

21. Glass-ceramics (special subset of particle-filled glasses) Crystalline filler particles mechanically added to glass. Recent approach – filler particles grown inside glass object after the object has been formed, the it is given a special heat treatment causing precipitation and growth of crystallities within glass. b’cos these fillers are derived chemically from atoms of glass itself, it stands to reason that the composition of remaining glass is altered- such particle-filled composites are called GLASS CERAMICS Eg.,Dicor -filler particles of crystaline mica (at 55vol%) Recently , a glass ceramic containing 70% crystalline lithium disilicate filler (IPS EMPRESS 2) is commercialized for dental use.

22. POLYCRYSTALLINE CERAMICS No glassy components All atoms densely packed into regular arrays that are difficult to drive a crack through. Tougher and stronger than glassy ceramics. More difficult to process into complex shapes. Opaque compared to glassy ceramics, so, these cannot be used for whole wall thickness in esthetic areas of prostheses. So, these higher strength ceramics serve as sub-structure materials upon which glassy ceramics are veneered to achieve pleasing esthetics.

23. Recent Advances In Dental Ceramics Sintered porcelains - Leucite - reinforced Feldspathic porcelain Alumina based porcelain Magnesia based core porcelain Zirconia based porcelain Glass ceramics Slip cast ceramics – Alumina based (in- ceram ) Hot pressed, injection-molded ceramics – L eucite -based S pinel –based Machinable ceramics – Cerec system Celay system Procera system According to processing technique and according to their major crystalline phase – ISABELLA L. DENRY, Crit Rev Oral Biol Med 1996, 7(2): 134-143

24. Sintered porcelains : LEUCITE REINFORCED FELDSPATHIC PORCELAIN- Optec HSP material is a feldspathic porcelain containing up to 45 vol % tetragonal leucite The greater leucite content of Optec HSP porcelain compared with conventional feldspathic porcelain for metal-ceramics leads to a higher modulus of rupture and compressive strength . The large amount of leucite in the material contributes to a high thermal contraction coefficient.

25. In addition, the large thermal contraction mismatch between leucite (22 to 25 x 10"6/°C) and the glassy matrix (8 x 10~6/°C) results in the development of tangential compressive stresses in the glass around the leucite crystals when cooled. These stresses can act as crack deflectors and contribute to increase the resistance of the weaker glassy phase to crack propagation.

26. After heat treatment of Optec HSP for one hour at temperatures ranging from 705 to 980°C, a second metastable phase identified as sanidine (KAlSi3O8) forms at the expense of the glassy matrix The crystallization of sanidine is associated with a modification of the optical properties of the material from translucent to opaque. However, sanidine does not appear when the porcelain is heated to 980°C, since sanidine is metastable in the temperature range 500-925°C.

27. ALUMINA-BASED PORCELAIN - Aluminous core porcelain is a typical example of strengthening by dispersion of a crystalline phase. Alumina has a high modulus of elasticity (350 GPa ) and high fracture toughness (3.5 to 4 MPa.m05). Its dispersion in a glassy matrix of similar thermal expansion coefficient leads to significant strengthening of the core.

28. The first aluminous core porcelains contained 40 to 50% alumina by weight. The core was baked on a platinum foil and later veneered with matched-expansion porcelain. Hi-Ceram(1985) is a more recent development of this technique. Aluminous core pocelain is now baked directly onto a refractory die.

29. MAGNESIA-BASED CORE PORCELAIN Magnesia core ceramic was developed as an experimental material in 1985. Its high thermal expansion coefficient (14.5 x 10'6/°C) closely matches that of body and incisal porcelains designed for bonding to metal (13.5 x 10"6/°C). The flexural strength of unglazed magnesia core ceramic is twice as high (131 MPa ) as that of conventional feldspathic porcelain (65 MPa ).

30. The core material is made by reacting magnesia with a silica glass within the 1100-1150°C temperature range. This treatment leads to the formation of forsterite (Mg2Si04) in various amounts, depending on the holding time. The proposed strengthening mechanism is the precipitation of fine forsterite crystals . The magnesia core material can be significantly strengthened by glazing, thereby placing the surface under residual compressive stresses that have to be overcome before fracture can occur .

31. ZIRCONIA-BASED PORCELAIN Mirage II (Myron International, Kansas City, KS) is a conventional feldspathic porcelain in which tetragonal zirconia fibers have been included. Zirconia undergoes a crystallographic transformation from monoclinic to tetragonal at 1173°C. Partial stabilization can be obtained by using various oxides such as CaO , MgO , Y2O3, and CeO , which allows the high-temperature tetragonal phase to be retained at room temperature.

32. The more recent core material for all- ceramics are Y- TZP The addition of yttrium oxide -stabilized zirconia to a conventional feldspathic porcelain - produced improvement in fracture toughness, strength, and thermal shock resistance. The transformation of partially stabilized tetragonal zirconia into the stable monoclinic form can also occur under stress and is associated with a slight particle volume increase.

33. The result of this transformation is that compressive stresses are established on the crack surface, thereby arresting its growth. This mechanism is called transformation toughening. However, other properties, such as translucency and fusion temperature, can be adversely affected. Y-TZP showed flexural strength of 900-1200 Mpa Fracture resistance - 1800-2000N.

34. GLASS-CERAMICS MICA-BASED Glass-ceramics are obtained by controlled devitrification of glasses with a suitable composition including nucleating agents. Advantage of this process is that the dental restorations can be cast by means of lost wax technique, thus increasing the homogenicity of the final product compared with conventional sintered feldspathic porcelains.

35. Dicor is a mica-based machinable glass-ceramic. In Dicor glass-ceramic - tetrasilicic fluormica (KMg25Si4O10F2) is the major crystalline phase. Micas are classified as layer-type silicates. Cleavage planes are situated along the layers, and this specific crystal structure dictates the mechanical properties of the mineral. Crack propagation is not likely to occur across the mica crystals and is more probable along the cleavage planes of these layered silicates.

36. In the glass-ceramic material, the mica crystals are usually highly interlocked within the glassy matrix, achieving a "house of cards" microstructure. The interlocking of the crystals is a key factor in the fracture resistance of the glass-ceramic, and their random orientation makes fracture propagation equally difficult in all directions After being cast , Dicor is converted in to a glass ceramic by means of single step heat treatment with 6 hr dwell at 1070 c This facilitates controlled nucleation and growth of mica crystals.

37. Hydroxyapatite – based Cera -Pearl crown is a castable glass ceramic crown, which involves the conversion of calcium-phosphate glass to a partially crystalline apatite glass ceramic. The crown is produced in a similar fashion to the Dicor crown but by using a special pressure-vacuum apparatus, and results in a restoration with light refractive index, density, hardness, thermal expansion and thermal conductivity, similar to natural enamel.

38. LITHIA-BASED Crystalline phase that forms is lithium disilicate (70%) of glass ceramic Experimental glass-ceramics in the system Li2O-Al2O3-CaO-SiO2 are currently the object of extensive researchwork . Lithium disilicate has unusual microstructure that consists of many small , interlocking, plate like crystals that are randomly oriented. Needle like crystals cause the crack to deflect, branch or blunt. Thus propagation of crack is arrested by lithium disilicate crystals, thus providing increase in flexural strength Flexural strength -350-450 Mpa . Fracture toughness 3 times that of leucite fledspar glass ceramic.

39. Slip-cast ceramics ALUMINIA – BASED (IN-CERAM) ln -Ceram is a slip-cast aluminous porcelain . The alumina-based slip is applied to a gypsum refractory die designed to shrink during firing. The alumina content of the slip is more than 90%, with a particle size between 0.5 and 3.5 micrometers. After being fired for four hours at 1100°C, the porous alumina coping is shaped and infiltrated with a lanthanum-containing glass during a second firing at 1150°C for four hours. After removal of the excess glass, the restoration is veneered with matched expansion veneer porcelain. This processing technique leads to a high-strength material due to the presence of densely packed alumina particles and the reduction of porosity .

40. 2 modified porcelain compositions for inceram technique - Inceram spinell – MgAl2O4 with traces of alpha alumina – to improve translucency of final restoration For inlays and anterior crowns due to flexural strength of 350 Mpa . - Tetragonal zirconia and alumina For posterior crowns due to high flexural strength of 700 Mpa and is also opaque.

41. HOT PRESSED, INJECTION MOLDED CERAMICS Leucite based – IPS Empress is a leucite -containing porcelain. Ceramic ingots are pressed at 1150°C (under a pressure of 0.3 to 0.4 MPa ) into the refractory mold made by the lost-wax technique. This temperature is held for 20 minutes in a specially designed automatic press furnace. The ceramic ingots are available in different shades. They are produced by sintering at 1200°C and contain leucite crystals obtained by surface crystallization. The leucite crystals are further dispersed by the hot-pressing step. The final microstructure of IPS Empress exhibits 40% by volume of tetragonal leucite . The leucite crystals measure 1-5 um and are dispersed in a glassy matrix.

42. 2 finishing techniques can be used with IPS Empress: - staining technique or - layering technique involving the application of veneering porcelain. The two techniques lead to comparable mean flexure strength values for the resulting porcelain composite. The thermal expansion coefficient of the IPS Empress material for the veneering technique (14.9 x 10"6/°C) is lower than that of the material for the staining technique (18 x 10~6/°C) to be compatible with the thermal expansion coefficient of the veneering porcelain. The flexural strength of IPS Empress material was significantly improved after additional firings IPS Empress permits easy, time saving procedure to fabricate veneers, inlays and onlays but not 3-unit FPDs as its flexural strength is below 200 Mpa .

43. So, IPS EMPRESS 2 which consists of lithium disilicate glass-ceramic core that is veneered with fluoroapatite based veneering porcelain is developed. The flexural strength of the frame work material – 350 – 400 MPa .

44. Spinel -based – Alceram is a material for injection-molded technology and contains a magnesium spinel (MgAl2O4) as the major crystalline phase This system was initially introduced as the "shrink-free" Cerestore system, which relied on the conversion of alumina and magnesium oxide to a magnesium aluminate spinel . Advantage – excellent marginal fit of the restorations .

45. Machinable ceramics CAD-CAM (computer assisted design-computer assisted manufacture) systems have also recently been introduced to the dental profession . All CAD/CAM systems are technically complex and involve three distinct steps: 1)Collection of information 2)Design of the restoration and 3)Fabrication. The popular CAD/CAM systems used in dentistry are: a)The CELAY system b)The CEREC system c)The Procera system

46. CELAY SYSTEM- The Celey system employs a copy-milling machine and uses manufactured porcelain blanks to mill out ceramic inlays, onlays , crowns and bridge is the CELAY system. This system is a precision copy-milling machine. The Celay system is unique in its milling capabilities; its milling are able to move in 8 axes of freedom, which allows the milling of complex, three-dimensional shapes. Thus, it can mill the occlusal aspects of restorations in very fine detail.

47. The marginal fidelity of these milled restorations are excellent; according to the manufacturer, marginal gap of only 50  m can be achieved. The Celay system provides the ability to fabricate both direct and indirect ceramic restorations. Copy milling technology requires the generation of a pattern of the desired restoration. This pattern can be fabricated directly in the mouth or on a working cast and dies. This pattern is then copy milled using the Celay machine to generate the final restoration. The system uses an approach similar to the pantographic method of duplicating keys.

48. CEREC SYSTEM - CEREC is a dental CAD/CAM machine. CAD/CAM stands for computer assisted design, computer aided manufacturing. Mormann's work led to the development of Siemens' CEREC CAD-CAM system. It was developed in Zurich Switzerland. It uses COPY MILLING technique to fabricate inlays, onlays , 3/4 crowns, 7/8 crowns and veneers. This system enables the direct chair side placement of ceramic restoration without auxiliary laboratory support.

49. The CEREC technique consist of: 1) 3 dimensional scanning of the cavity or taking an optical impression, 2) Immediate data transformation and 3) 3 axial milling which is integrated into a mobile unit. CEREC: The CEREC was first introduced in 1986. It consisted of a mobile unite containing a small camera, a computer with scan and 3-axis-of-rotation milling machine. This old milling machine was water-pressure driven “hydro” version.

50. The  cavity preparation  is first  photographed  and stored as a  three dimensional  digital model and  proprietary software  is then used to approximate the restoration shape using biogeneric comparisons to surrounding teeth. The practitioner then refines that model using 3D  CAD  software. When the model is complete a milling machine carves the actual restoration out of a ceramic block using  diamond  head cutters under computer control. When complete, the restoration is bonded to the tooth using a  resin . CEREC is an acronym for Chairside Economical Restoration of Esthetic Ceramics.

51. Advantages Time savings. Patients usually only have to go one time, as opposed to two trips for a traditional crown; this also reduces the number of local anesthetic injections needed. More conservation of tooth structure. Oftentimes a partial coverage restoration can be completed vs a full conventional crown. Stronger porcelain. Milled ceramic is stronger than hand layered and pressed. Aesthetics. Homogeneous porcelain blends in better than other porcelains. Natural. Ability to copy what was there previously can yield restorations that are duplicates of the pre-prepared tooth. Disadvantages 1. Requires investment of time and money for dentist to obtain and learn, however there are no disadvantages for the patient who receives the filling.

52. 1.  CEREC ( Sirona Dental Systems GmbH, Bensheim , Germany) form-grinding evolution: feldspathic block ceramic.  A.  Basic grinding trial with diamond-coated wheel.  B.  CEREC 1: water turbine drive.  C.  CEREC 1: inlay emerging from a block.  D.  CEREC 1: E-drive.  E.  CEREC 2: cylindrical diamond bur and wheel.  F.  CEREC 3: cylindrical diamond and tapered burs.  G.  In 2006, a "step bur" replaced the cylinder diamond.

53. CEREC 2 : It consists of a mobile unit containing a small camera, a computer with scan and 3-axis-of-rotation milling machine. The milling machine has an electric motor called “E” version to provide a better and smoother cutting of ceramic resulting in better fitting restorations.

54. The restoration produced by the CEREC I system must be ground and polished to develop the proper occlusal contacts and anatomy . The new CEREC II systems also mills the occlusal surface of the restoration, and may be used to fabricate crowns in addition to inlays, onlays and veneers The precision of Cerec 2 grinding unit has been found to be 2.4 times higher than Cerec .

55. CEREC 3: It is the modular CAD/CAM system. It provides rapid imaging, design and milling processes and additional advantages like saving space, design, handling hygiene through the integration of the SIDEXIS intraoral X-ray system and the SIROCAM 2 intraoral camera.

56. CEREC 3 TECHNIQUE The CEREC 3 system has several technical improvements over CEREC 2, including the 3 dimensional CEREC 3 intraoral camera, manipulation of the picture, and the grinding unit. Intraoral camera: The most significant factor for surveying with the CEREC 3 intraoral camera is that tooth All points of interest can be seen from a single visual angle, i.e., the angle of preparation or insertion. .

57. Double grinding unit: the computer controlled doubled grinding unit dispenses with the grinding wheel and uses 2 individual cutting devices. The 2 instruments act together symmetrically in a shaping process providing morphologically better adaptation as well as better appearance of the occlusal design.

58. 60 The CEREC 3D CAD/CAM system The latest incarnation of the CEREC system is the CEREC 3D,which provides a versatile, relatively simple, user-friendly method for fabricating esthetic restorations without involving a dental laboratory. It has expanded on the concepts of computer imaging by utilizing three –dimensional viewing capacities . There are distinct advantages to using the CEREC 3D as compared with its predecessors (CEREC 1, CEREC 2, and CEREC 3). The primary difference is the software, which requires far fewer steps than the CEREC three and makes it easier for the dentist to proceed.

59. Fun in the Dunn 61 Technique The optical impression is made. The restorations are designed on the computer using one of the two modes, “correlation” or “Dental Data Base ”. Correlation utilizes a preoperative optical impression of the unprepared tooth. Dental Data Base utilizes the software’s virtual library of tooth morphology to create the anatomy and contours of the restoration. From this impression a virtual model is created on the screen. The restoration is designed and carved from a solid block of porcelain.

60. 62 Features The 3D feature of the software allows the model to rotate 360 degrees in every plane. With the CEREC 3D, the margins are created automatically by the software, reducing the chance of operator error. The software makes this a user friendly process through an automatic margin finder. Once the dentist is satisfied with the margin line, the software will design the restoration and place it on the die for viewing. Further modifications can be made using edit window which offers the dentist six different tools; edit, drop, scale, shape, position and rotate .

61. MILLING OF DRY PRESSED POWDER FOR ENLARGED DIES: Procera system Densely sintered alumina-based ceramics produced by dry pressing, followed by sintering are used Procera system employs the procera scanner to scan surface of prepared tooth and transmit data to the milling unit. The technique involves computer aided production of an enlarged die in order to compensate for sintering shrinkage (12 to 20%)

62. High-purity aluminum oxide powder with a defined grain size is then pressed on to the die using very high pressures. This enormous pressure gives the material a high packing density, a main factor in the materials strength. The outside shape of the coping is then milled before the sintering process. By sintering at very high temperatures (over 1,550ºC) the coping will shrink to the original dimensions and will have excellent marginal fit.

63. LOW FUSING CERAMICS Low fusing ceramics have been developed primarily for the use with titanium frame works. Titanium is now being used for metal ceramic restorations because of its biocompatibility and corrosion resistance. Low fusing porcelains are required to adequately match the thermal expansion coefficient of titanium, to reduce residual stress, which may result in failure of the ceramic, in contrast to high fusing materials, which may suffer from dissolution of crystalline components. METAL CERAMIC RESTORATIONS

64. These lower temperatures can result in a more natural, life like appearance of the porcelain. Flexural strengths are similar to that of conventional feldspathic porcelain. Ducera presently makes a low fusing ceramic, Ducera LFC, which can be fired at 660ºC. This ceramic can be used to fabricate all-ceramic inlays, onlays and veneers. Additionally, repairs and corrections of porcelain or metal ceramic margins may be accomplished with this ceramic.

65. DUCERA LOW FUSING CERAMICS It is composed of an amorphous fluorine glass containing hydroxyl ions and the base layer composed of Duceram Metal Ceramic leucite containing porcelain. Duceram LFC is then layered on base layer as a powder-slurry. It is then strengthened by ion exchange mechanism involving hydroxyl ions thus decreases the surface micro flaws and increase fracture resistance. It has a firing temperature of 702  C

66. Conclusion The new generation of ceramic materials present interesting options, both in terms of material selection and in terms of fabrication techniques. A closer understanding of the dynamics of the materials with respect to design of the restoration and the intended use is required to enable these restorations to perform productively.

67. REFERENCES Isabella L.Denry , Recent Advances In Ceramics For Dentistry; Crit Rev Oral Bio Med 1996, 7(2): 134-143 J. Robert Kelly, Dental Ceramics: Current Thinking And Trends; Dent Clin N Am 48 (2004) 513-530 Ariel J. Raigrodski ; Contemporary All-ceramic Fixed Partial Dentures : A Review; Dent Clin N Am (2004) 531-544 Jason A. Griggs , Recent Advances In Materials For All-ceramic Restorations; Dent Clin N Am 51(2007) 713-727 Lazer ; Y_TZP Ceramic Processing From Coprecipitated Powders: A Comparative Study With 3 Commercial Dental Ceramics; Dental Materials 24(2008) 1676-1685. J W Mclean; Evolution Of Dental Ceramics In Twentieth Century; J Prosthet Dent 2001,85(1),61-66. Richard Von Noort ;Introduction To Dental Materials K J Anusavice ; Science Of Dental Materials R G Craig ; Restorative Dental Materials