dental materials CERAMICS


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anil    on Mar 01, 2012 Says :

Good information on dental cementing
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1 : Ceramics
2 : Ceramics The word “ceramic” is derived from the Greek word “keramos” that translates to mean, “burnt earth.” Defination : Compounds of one or more metals with a non metallic element (usually silicon, boron, oxygen) that may be used as a single structural component or as one of the several layers that are used in the fabrication of a ceramic based prosthesis G.P.T 7, Anusavice.
3 : Porcelain A ceramic material formed of infusible elements joined by lower fusing materials. Most dental porcelains are glasses and are used in fabrication of teeth for dentures, pontics and facings, crowns, inlays, onlays and other restorations
4 : Classification of dental ceramics Based on chemical composition According to type According to use According to firing temperature According to firing technique According to substrate metal Microstructural classification Processing technique
5 : Classification of Dental Ceramics According to use or indications Anterior Posterior Crowns Veneers Post and Cores FPDS Stain Ceramic Glaze Ceramic
6 : According to firing temperature Ultralow fusing< 8500C Low fusing 850-11000C Medium fusing 11010C-13000C High fusing>13000C:
7 : Contd.. High fusing: Minimizing the additives such as sodium or potassium, Maximizing the silicate cross links. Low solubility, high strength and high stability. Hardness exceeds enamel by 30%. Medium fusing: fired under vacuum with air admitted at the end of firing
8 : Contd.. Low fusing: increasing the amount of additives in porcelain reducing the number of crosslinks within the silicate network It helps to avoid overheating the metal framework slightly weaker and less stable than high fusing fired under vacuum Ultra low fusing: Coefficient of thermal expansion match titanium alloys. Lower firing temperatures -less oxide formation
9 : According to the processing method Sintering Partial sintering Glass infiltration CAD/CAM Copy milling
10 : According to composition/Type: Feldspathic porcelain Leucite-reinforced porcelain Aluminous porcelain Alumina Glass-infiltrated alumina Glass-infiltrated spinel Glass-infiltrated zirconia Glass ceramic
11 : Microstructural Classification Composition Category 1—Glass based systems (mainly silica) Composition Category 2—Glass based systems (mainly silica) with fillers, usually crystalline (typically leucite or, more recently, lithium disilicate) Composition Category 3—Crystalline-based systems with glass fillers (mainly alumina) Composition Category 4—Polycrystalline solids (alumina and zirconia)
12 : According to translucency Opaque Translucent Transparent
13 : According to application: Core Porcelain. Dentin or Body Porcelain Enamel or incisal porcelain
14 : According to the method of firing Air fired. Vacuum fired
15 : Classification All ceramic Machined Slip cast Heat pressed Sintered. Ceramic- metal Sintered. Denture teeth. Manufactured
16 : Applications of dental ceramics Single unit crowns. Porcelain Jacket Crowns. Metal Ceramic Crown or PFM crowns. Castable glass ceramic crowns. Veneers for crowns and bridges. Artificial teeth. Inlays and Onlays. Ceramic Brackets used in Orthodontia.
17 : Indications for ceramics: Esthetic alternative to discolored teeth. Esthetic alternative :grossly decayed carious teeth. Congenital anamolies Veneers Inlays Onlays Abutment retainers Denture tooth materials. Orthodontics as ceramic brackets.
18 : Contraindications: Young permanent teeth. Small short or thin crowns( relative contraindications) PFM not indicated in high lip line patients. Teeth round in cross section OR Teeth more axially tapered than usual. Abusive bite. Patient’s lifestyle susceptible to trauma
19 : Advantages Biocompatibility Esthetics Color and translucency Capable of being pigmented. Colour stability. Stain resistance. Chamaleon like effect Durability: Wear resistance and low solubility. Ability to form precise shapes High stiffness High melting point. Low thermal conductivity Low electrical conductivity
20 : Disadvantages: Brittle: Low fracture toughness. High firing shrinkage of conventional porcelains. Attrition of opposing teeth. More tooth reduction. Cervical bulge and metal line in case of PFM restoration Technique sensitive. Specialized training required. Expensive equipment required. Difficult to repair if fails. Cannot be repaired if the shade is altered. Patient may complain of crackling sound on biting
21 : Composition of Dental Porcelain Feldspar 60-80%( Basic glass former) Kaolin- 3-5%( Binder) Quartz- 15-25%( Filler) Alumina-8-20%( Glass former) Boric oxide-2-7%(Glass former and fluxes) Oxides of Na, K and Ca -9-15%(Fluxes or glass modifiers) Metallic pigments less than 1%(Color matching)
22 : Feldspar (60-80%) Basic glass former Naturally occurring double silicate of potassium and aluminium.K20.Al2O36SiO2 Dentistry: Potash Feldspar: Increased resistance to pyroplastic flow Increased viscosity. Functions of Feldspar: Basic Glass former. During firing fuses to form a matrix and the porcelain powder particles will fuse together by a process of liquid phase sintering. Acts as a flux and surface glaze.
23 : Feldspar: Properties Resistance to pyroplastic flow Large coefficient of thermal expansion (20-25 ppm/0C.) thermally compatible with dental casting alloys. Strengthening material.
24 : Kaolin( 3-5%)Binder Hydrated aluminium silicate. Functions: Binder. Pyrochemical reaction: rigidity. Opacity to the mass. Disadvantages: White : reduces the translucency of porcelain. added in small amounts. Starch or sugar.
25 : Quartz/ Silica (15-25%) Filler Below 5750C Alpha quartz Above 5750C Beta quartz Above 8700C Tridymite Above 1470oC Crystobalite Forms of silica Crystalline quartz Cristobalite Tridymite Amorphous fused quartz
26 : Functions: grinding pure quartz Refractory skeleton Provides strength and hardness to porcelain during fusing. Unchanged at the usual firing temperatures : stability to the mass during heating
27 : Aluminium oxide( 8-20% glass former) Functions: Strength and opacity to the porcelain. Alters softening point increases the viscosity of porcelain during firing.
28 : Fluxes (9-15%) Sodium carbonate Lithium carbonate low fusing glasses. Function: Lower the sintering temperature and increase flow of porcelain. They also absorb and remove impurities. Excess flux: Reduces the chemical durability Crystallization and devitrification
29 : Glass modifiers Lower the softening temperature. Increase the CTE. Decrease viscosity. Oxides : Sodium, Potassium and Calcium oxide( 9-15%) Boric oxide- 2-7% is also added for the same purpose. Water is an important but a weaker glass modifier. When porcelains are exposed to tensile stresses in moist environment for long periods H30+ replaces alkali metal ions in porcelain slow crack growth New ultra low fusing porcelains : large amount of sodium oxide and hydroxyl group to lower the fusion temperature to as low as 6600C.
30 : Pigments Feldspars are colorless or greyish. Color frits Ferric oxide, platinum Chromium oxide, copper oxide Cobalt salts Ferrous oxide,nickel oxide Titanium oxide Manganese oxide Chromium tin, Chromium alumina Indium Grey Green Blue Brown Yellowish brown Lavender Pink Yellow, ivory
31 : Opacifiers and Fluorescing agents. Opacifiers: Oxides of Cerium, titanium, zirconium and tin. Ground to a particle size of less than 5 µm. Fluorescing agents: Cerium oxide ( eg. Fluorescent bulbs and sunlight). Fluorescence is the phenomenon in which an object emits light when it is illuminated by a specific light source, in case of teeth, it gives an appearance of vitality. Uranium compounds: Health hazard.
32 : Properties of Ceramics Esthetic Properties: -Colour, translucency and vitality . Chemical stability: -Chemically inert Some form of fluoride can damage porcelain. -1.23 % ( APF) -8% stannous fluoride Dull and rough within min. -Hydrofluoric acid. -Stannous fluoride( 0.4%) or sodium fluoride(2%) :will not etch . -The etching of the interior with hydrofluoric acid: Bonding. -Phosphoric acid, has very little effect on dental porcelain.
33 : Thermal properties Shrinkage on heating: The linear shrinkage : 11.5% for high fusing porcelain 14% for low fusing porcelain. CTE should match tooth structure to minimize shrinkage and gap CTE should be slightly lower than that of the casting alloy keeping the porcelain in residual compression upon cooling from firing temperatures. CTE: 12-13X 10-60C Thermal shock failure: Caused by uneven heating or cooling. More severe on reheating or glazing a crown than cooling.
34 : Mechanical properties: Compressive strength :good. Tensile strength: Poor. Unavoidable surface defects like porosities and microscopic cracks. ? When porcelain is placed under tension, stress concentrates around these imperfections resulting in brittle fracture. Shear strength: low :due to the lack of ductility
35 : Property Strength -Flexure Strength -Compressive Strength -Tensile Strength( low) -Shear strength( low) -Modulus of elasticity( high) -Surface hardness Value -Ground-75.8Mpa(11,000psi) -Glazed141.1Mpa( 20,465psi -331Mpa(48,000psi) -34Mpa( 5000psi) -110 Mpa( 16.000psi) -60-70 Mpa( 10x106 psi) -460KHN 611-703VHN( Kg/mm2)
36 : Contd.. Property Coefficient of thermal expansion Thermal conductivity Specific gravity Value Feldspathic:6.4-7.8x10-60C. Reinforced:12.38-16.23 x10-60C 2.39 Mcal/s(cm2)( 0C/cm) 2.2-2.3( true is 2.242)
37 : The feldspathic porcelain are condensed by vibration or dry-pressed (Procera) and sintered at high temperatures. Eg -some aluminous porcelains (Vitadur-N, Hi- Ceram), -pure alumina ceramic (Procera All Ceram)
38 : Pressable ceramics when heated and subjected to hydrostatic pressure, flow into a mold and, after removal and divesting, are then veneered. Cast and crammed crowns, such as the obsolete product Dicor, are made using the lost-wax technique. The molten glass is cast into a mold, heat-treated to form a glass-ceramic, and colored with shading porcelain and surface stains Eg ., IPS Empress, IPS Empress2, Fineness All-Ceramic, OPC, and OPC-3G
39 : Slip casting ceramics A slip is a low viscosity slurry or mixture of ceramics powder particles suspended in fluid Slip casting involves forming a mold or negative replica of the desired framework geometry and pouring a slip into the mold The mold is made of material that extracts some water from the slips into the walls of the mold through capillary action, and some of the powder particles in the slip become compacted against the wall of the mold forming a thin layer of green ceramics that is to become the framework
40 : Contd… The remaining slip is discarded, and the framework can be removed from the mold after partial sintering to improve the strength to a point where the framework can support its own weight. Ceramics fabricated by slip casting can have higher fracture resistance than those produced by powder condensation because the strengthening crystalline particles form a continuous network throughout the framework. E.g. glass infiltration (In-Ceram, Vita Zahnfabrik) Limited application is because of complicated series of steps, which provide a challenge to achieving accurate fit & may result in internal defects that weaken the material from incomplete glass infiltration The original In-Ceram and some partially stabilized zirconia blocks are fabricated based on slip casting of alumina or zirconia.
41 : For CAD-CAM processes the ceramic block materials (Dicor MGC, Vita Cerec Mk I, and Vita Cerec Mk II) are shaped into inlays or crowns using a CAD-CAM system (Cerec). CAM refers to computer aided milling or machining. This process is some times referred to as a CAD-CIM process, where CIM refers to computer –integrated machining or milling These blocks can also be used in copy-milling devices (Celay) a key from a key blank, that is, by tracing over a master die of the shape to be produced out of the ceramic
42 : Composition Category 1 Glass-Based Systems Best mimic the optical properties of enamel and dentin. Derived from group of mined minerals called feldspar and are based on y silicon dioxide (also known as silica or quartz), and alumina ( aluminium oxide). Alumino-silicates occurs naturally, and contain various quantities of potassium and sodium, are known as feldspars. Glasses based on feldspar are -Resistance to crystallization -Have low firing ranges - biocompatible
43 : Composition Category 2 Glass-Based Systems with Fillers Fillers are added to the glass composition to increase - the mechanical properties -to control optical effects such as opalenscence, color and opacity It is further divided into three groups The composition is same as the pure glass category 1 The difference is varying amount of crystal types have been either added to or grown in the glassy matrix The primary crystal types are leucite, lithium disilicate or fluroappetite
44 : Contd… Leucite is created in the dental porcelain by increasing potassium dioxide in aluminosilicates glass. This fillers are added to the porcelain to create porcelain that could be successfully fired to the metal substructures. Lithium disilicate crystal are made by adding lithium dioxide to the aluminosilicates glass. It also acts as a flux, lowering the melting temperature of the material.
45 : Contd…. Subdivided into three groups: Low-to-moderate leucite-containing feldspathic glass High-leucite-containing (approximately 50%) glass Lithium-disilicate glass ceramic
46 : Low-to-moderate leucite-containing feldspathic glass These materials have been called “feldspathic porcelains” by default. Leucite - increases coefficient of thermal expansion -inhibit crack propagation, there by improving the material strength -the amount of leucite can be adjusted in the glass based on the type of core and required coefficient of thermal expansion.
47 : High-leucite-containing (approximately 50%) glass  The glassy phase is based on an aluminosilicate glass. These materials have been developed in both powder/liquid, machinable and pressable forms.
48 : Lithium-disilicate glass ceramic Lithium-disilicate glass ceramic is a new type of glass ceramic where the aluminosilicate glass has lithium oxide added. Examples: IPS Empress® II (now called IPS e.max®),
49 : Composition Category 3 Crystalline-based Systems with Glass Fillers Covers wide scope of all-ceramic restoration including veneers,inlays onlays, anterior, posterior crowns and bridge. E.g. In-Ceram spinnel-(alumina and magnesia matrix) is the most translucent and moderate strength and is used for anterior crowns .In-Ceram alumina(alumina matrix) has high strength and moderate translucency and used for both posterior and anterior crowns In-Ceram Zirconia( alumina and zirconia matrix) has very high strength and lower translucency and primarily used for three unit bridges
50 : Composition Category 4 Polycrystalline Solids Have no glossy components; all atoms are densly packed together without any intervening matrix to from a dense, air-free, glass-free, polycrystalline structure This structure makes difficult to drive cracks through atoms compared to atoms in less dense and irregular network found in glass These are relatively opaque and used as substructure material upon which glassy ceramics are veneered to achieve pleasing aesthetics There are several different processing techniques that allow the fabrication of either solid-sintered aluminous-oxide or zirconia-oxide frameworks.
51 : All ceramic systems Stronger materials that involve better fabricating techniques. Can be etched and bonded to the underlying tooth structure with newer dentin adhesives.
52 : Classification of all ceramic systems Processing technique and the major crystalline phase - Sintered Porcelains -Glass Ceramics -Machinable Ceramics -Slip Cast ceramics -Hot pressed injection molded
53 : Sintered Porcelains Leucite- reinforced feldspathic porcelain: Optec HSP Aluminous based porcelain: Vitadur- N TM core Alumina based porcelain: Hi ceram Magnesia based feldspathic porcelain( Experimental) Zirconia based porcelain: Mirage II Hydrothermal low fusing Ceramics: Duceram LFC.
54 : Mica based: Dicor Hydroxyapatite based: Cerapearl Lithia based: Experimental. Glass Ceramics. Machinable ceramics. Cerec system Celay system Procera system
55 : Slip Cast Ceramics Alumina based( In- Ceram) In – Ceram Spinell In – Ceram Zirconia In- Ceram 2000. Leucite based: IPS Empress Spinel based: Alceram Hot pressed, injection molded
56 : Mc Lean and Hughes in 1965. Vitadur N Core( Vident, Baldwin Park, CA) 123 Mpa Alumina: High modulus of elasticity( 350 Gpa) High fracture toughness( 3.5 to 4 Mpa). Dispersion in a glassy matrix of similar CTE . Significant strengthening of the core. Core was baked on a platinum foil. Later veneered with matched expansion porcelain. Aluminous based Porcelain
57 : Hi- Ceram 139 Mpa( compared to 65 Mpa). Alumina. directly baked on the refractory die. Aluminous core porcelain( Directly on the refractory die) Reduce the surface area of the matrix where microcracks form. Crack stoppers preventing propogation of crack. Alumina crystals:
58 : Why Alumina? Good Mechanical properties. Similar CTE and MOE. Interfacial region between alumina and porcelain virtually stress free. Crystals rather than fine powdered alumina used. Advantages of aluminous porcelains: Increased flexural strength, Increased elasticity and toughness.
59 : Poor esthetics ( Used as a core only). Extensive reduction, dentin preparation. Bonding is limited. High failure rates. Disadvantages of Aluminous porcelain
60 : Leucite reinforced feldspathic Porcelain: Feldspathic porcelain with 45% vol tetragonal leucite. Higher modulus of rupture and compressive strength. Does not require core unlike aluminous PJC. Leucite and glass fuse together at 10200C. Large thermal contraction mismatch: -leucite ( 22- 25x10-6/0C) -glassy matrix( 8x10-6/0C) To overcome this: -K ions -Formation of sanidine after heat treatment:705 to 980 0C
61 : Lack of metal or opaque substructure, Good translucency compared to alumina crowns. Moderate flexural strength( 146 Mpa), Ability to be used without special laboratory equipment. Can be etched. Advantages: Disadvantages: Marginal inaccuracy caused by sintering shrinkage. Potential to fracture in posterior teeth. Increased leucite content :relatively high invitro wear of opposing teeth. Requires a special die material. Uses: Leucite reinforced Feldspathic Porcelain. Inlays, onlays, crowns for low stress areas and veneers
62 : Magnesia based core porcelain Advantages High CTE: Same body and enamel porcelains used for PFM crowns can be used for all ceramic Flexural strength of magnesia core :131 Mpa Twice as high as feldspathic porcelain( 65 Mpa). Esthetics superior to PFM. Disadvantages Not used for fixed partial dentures.
63 : Zirconia based feldspathic porcelains. Fracture toughness Thermal shock resistance Î Properties such as translucency and fusion temperature can be adversely affected. Advantages Disadvantages:
64 : Hydrothermal Porcelains Non feldspathic composition that forms a plasticized surface layer when hydrated. Surface hardness Flexural strength Plastic nature of the hydrated surface ? Allows for deformation of surface flaws ? Prevents them from propagating through the bulk.
65 : Good flexural strength (110 MPa) and fracture toughness Greater density Low hardness – less abrasive Needs special die material Advantages: Disadvantages: Hydrothermal Porcelains
66 : Glass ceramic: Is a ceramic consisting of a glass matrix phase and at least one crystal phase that is produced by the controlled crystallization of the glass. Glass Ceramic
67 : Heat treatment that causes microscopic plate like crystals of crystalline material to grow within the glass. Ceramming Nucleating Agents Metallic colloids. Liquid phase separation. Halides Sulphides. Glass ceramics
68 : Rate of nucleation/growth Temperature T2 T1 2 stage heat treatment Dicor
69 : Method of fabrication of castable glass ceramic Phosphate bonded investment. Wax burn out and heat soak 950 0C Centrifugal casting of molten ceramic 13500C. Reinvest in leucite based gypsum bonded investment
70 : Heat treatment Fabrication castable glass ceramic 10750C for 10 hours Reduced translucency. Increased strength
71 : Mica based glass ceramics. Dicor 55% vol of tetrasilicic flouramica crystals increased strength and toughness increased resistance to abrasion thermal shock resistance chemical durability decreased translucency Nucleating agents: Flouride. House of cards: Microstructure.
72 : Difference between Dicor and Dicor MGC Dicor 55%vol of tetrasilicic fluoramica crystals. Crystallization done by the technician. Mechanical properties similar. Dicor MGC 70% vol of tetrasilicic flouramica crystals which are 2 µm in diameter Higher quality product that is crystallized by the manufacturer and provided as cadcam blanks or ingots. Less translucent than Dicor. Passage of light depends on: Crystal size. Difference in refractive index between glass matrix and crystal.
73 : Improved esthetics: Chamaleon effect. Uniformity and purity of the material. Minimal processing shrinkage Good fit. Low CTE equal to that of the tooth structure Minimal abrasiveness to the tooth structure. Radioopacity like dentin. Inherent resistance to plaque accumulation ( Seven times less than on natural teeth.) Moderately high flexural strength.(152 MPa) Advantages of Dicor:
74 : Disadvantages of DICOR Low tensile strength. Inability to be colored internally The colorant stains may be lost during occlusal adjustment. Chances of losing the low fusing feldspathic porcelain which are applied for good shade matching. Labour intensive High cost Inlays, Onlays,Complete crowns ,partial tooth coverage Indications
75 : Hydroxyapatite based castable glass ceramics: Cerapearl. Sumiya Hobo and Kyocera Bioceram group of Kyoto City, Japan . Castable glass ceramic :CaO- P205- MgO-Si O2 oxyapatite hydroxyapatite Cerapearl Moisture Enamel oxyapatite hydroxyapatite
76 : Properties of Cerapearl Melts at 14600C and flows like a melting glass. CTE small enough to obtain accurate castings. The cast material has an amorphous microstructure when reheated at 8700C forms crystalline HA. Biocompatible: Crystalline structure similar to enamel. Enamel: Regular arrangement. Cerapearl: Irregular arrangement. Hence same crystal components but superior mechanical strength. Modulus of rupture :150 Mpa. Enamel Cerapearl
77 : Procedure for Cerapearl Crowns thicker than metal ceramic because of poor flexural characteristics. Tooth preparation 2mm: occlusal reduction 1.5 mm: axial reduction. 1.2 mm on the margin. Heavy chamfer or shoulder finish line. All sharp edges should be rounded.
78 : Procedure for Cerapearl Waxing A full arch impression is made. Working cast fabricated with Type IV stone. Dowel pins are employed. Die spacer of 25µm is applied on the die except within 1 mm of the finish line Wax pattern is fabricated.
79 : Casting Procedure for Cerapearl Wax sprue 2.5 mm in diameter and 35 mm long is attached to the thick portion of the wax pattern. Other end -orifice of the ceramic crucible. A special phosphate bonded high heat investment exhibits the same CTE as Cerapearl’s casting shrinkage( 0.53%). The sprued wax pattern is located inside preformed silicone form used for fabrication of ringless investment mold and investment is poured.
80 : Burnout procedure for cerapearl. Temperature less than 1000C for 30 min. Temperature is raised to 5000C ,next 30 min. Temperature is held at 8000C for 30 min. Electric oven Ringless investment mold with ceramic crucible on the top
81 : Casting of cerapearl Investment mold is transferred to a specially designed casting machine. 8-10 g of raw Cerapearl is placed in the ceramic crucible, Melted under vacuum at 14600C and cast into the mold.
82 : Crystallization of Cerapearl. Started at 7500C ,maintained for 15 min. Temperature is then raised 500C per min until it reaches 8700C and then held for one hour. The apatite crystals would have occurred during the process.
83 : Trial insertion: Cerapearl. Investment mold is removed from the oven and cooled to room temperature. Air abrading with 20 µ alumina oxide of the casting. The sprue is cut and polishing is done.
84 : Staining and glazing: Cerapearl is very white compared to enamel Requires application of an external stain.
85 : Bonding to the tooth structure: Similar in structure to enamel and GIC will adhere. Activation Process by which the casting is mechanically and chemically treated to bond to the tooth structure. Mechanical Air abrasion. Chemical UHK 001 activator solution Once bonded, cerapearl is extremely strong. Currently in research phase, not commercially available.
86 : Bioactive glass. Bioactivity Characteristic of the material to form bond with the living tissue. Implants and implantable products such as DPC material.
87 : Pressable ceramics. Leucite based: IPS Empress and Optec OPC. IPS Empress Glass ceramic based on the leucite system. Subjected to bulk crystallization.
88 : Lack of metal. Translucent ceramic core Moderately high flexural strength Excellent fit Excellent esthetics.( Translucence, flouroscence and opalescence) Minimal shrinkage: only shrinkage that occurs is during cooling, that can be controlled with an investment having an appropriate expansion. IPS Empress Advantages: Disadvantages Potential to fracture in the posterior areas. Need to use resin cement to bond the crown micromechanically to the tooth structure. Expensive equipment.
89 : Laboratory procedure for IPS Empress lost wax technique material is pressed into the mold under pressure, not centrifugally driven Wax pattern fabrication Investment in phosphate bonded investment
90 : IPS Empress Burn out procedure. Specialized mold – Alumina plunger. Ceramic ingot is placed under the plunger. Entire assembly heated to 11500c. Plunger presses the molten ceramic into the mold.
91 : Final surface of the restoration: Stain/ veneer IPS Empress.
92 : IPS Empress Leucite containing glass ceramic that contains about 35% volume of leucite crystals. The veneering ceramic also contains leucite crystals in a glass matrix. Anterior crowns, veneers, inlays. IPS Empress II Core :Lithia disilicate crystals in a glass matrix Veneering ceramic: contains apatite crystals. All ceramic bridges Anterior and posterior crowns.
93 : IPS Empress II 70% vol of elongated Lithia disilicate crystals Crystal size: of 0.5 to 4 µm Small interlocking plate like crystals that are randomly oriented A second crystalline phase :lithium orthophosphate (Li3PO4) of a much lower volume, also present
94 : Empress Eris Leucite core ceramic is identical to the veneering ceramic Empress I Empress II CTE of core ceramic is 10.6 ppm/0C, hence a compatible layering ceramic was to be developed. Empress Eris Apatite glass ceramic.
95 : Low firing temperature: Superior compatibility with lithium disilicate. Apatite crystals influence translucency, brightness and light scattering ability of layering ceramics. Empress Eris
96 : Empress Esthetic New leucite reinforced glass ceramic
97 : Broader ingot shade range. Greater homogeneity. Greater density. Greater flexural strength. Natural translucency and fluorescence Excellent press results. Same processing and pressing temperature 1075/1967 0C as that of staining technique Empress esthetic
98 : OPC and OPC3G Optimal pressable ceramic. OPC: Similar to IPS Empress, Leucite containing. OPC3G: Similar to IPS Empress2, lithium disilicate.
99 : Spinel based pressed ceramic Non shrink ceramic Alumina and magnesium oxide Magnesium aluminate spinel( Higher volume) Cerestore Method of fabrication Wax pattern. Investing. Mold formation. A mixture of alumina, wax, silicone resin, magnesia and glass is then heated to allow flow and injected into the mold
100 : Cerestore method of fabrication. A series of reactions between the main oxide components. Formation of spinel( Magnesium aluminate. Volume expansion associated with spinel formation compensates for shrinkage during firing.) Advantage of Cerestore Excellent fit of the restoration.
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