Dental ceramics are the most natural appearing replacement material for missing teeth. available in a range of shades and translucencies to achieve life like results. Dental ceramics are known for their natural appearance and their durable chemical and optical property. Earlier esthetic was not as important for the patient as it is today.ceramics r increasingly used now a days,,, as esthetics is a major concern of the society today.
According to GLOOSARY OF PROSTHODONTIC TERMS.
Dental ceramics for ceramic-metal restorations belong to A family commonly referred to as dental porcelains.4CRAIGALL PORCELAIN ARE CERAMICS BUT ALL CERAMICS ARE NOT PORCELAIN.
DATES BACK TO 23000 BC
Ceramics are thought to be the first materials ever made by man.
. Animal bone and ivory from the hippopotamus or elephant were used for many years thereafter. Later, human teeth sold by the poor and teeth obtained from the dead were used
Reamer a scientist who was able to identify the components used by the Chinese as kaolin, silica and feldspar. His initials were represented in the name of the S.S.White company.
and the reduced use of amalgam and traditional cast metals.
USECOMPOSITIONPROCESSING METHODTRANSLUCENCYFIRING TEMPERATURE
IN CERAM ALUMINAIN CERAM ZIRCONIAIN CERAM SPINELIPS EMPRESS IS USED FOR INLAY, ONLAY VENEERS AND FULL COVERAGE CROWNS.
Several prosessing techniques are available,,,,,,SINTERING IS THE FUSION OF PORCELAIN PARTICLESSintered all-ceramic restorations are now being replaced by heat-pressed or machined all-ceramic restorations with better-controlled processing steps.2,APPLICATION OF EXTERNALPRESSURE TO SINTER AND SHAPE THE CERAMIC AT HIGH TEMP3.CAD CAM,COMP ASSISTED DESIGN,COMP ASSISTED MACHING.
1,OPAQUE PORCELAIN USED TO MASK THE METAL 2.TRANSLUCENT PORCELAIN USED AS ENAMEL PORCELAIN
Medium and high fusing teeth are used for denture teeth.High fusing are superior in strenghtand translucency.the main advantage is that they can be repaired,added to, stained and glazed without distortion,LOW FUSING AND ULTRA LOW FUSING IS USED FOR CROWN AND BRIDGE CONSTRUCTION.
Ceramics are compounds of metallic elements and non-metallic element such as oxides, nitrides, and silicates.
Ceramic metal restorations belong to this compositional range.
The feldspars are mixtures of potassium alumino silicate (K2O.Al2O3.6SiO2) and sodium alumino silicate, also known as albite (Na2O.Al2O3.6SiO2). Functions of Feldspar-During firing fuses to form a matrix and the porcelain powder particles will fuse together by a process of liquid phase sintering.When it fuses, it forms a glassy material that gives the porcelain its translucency.. Another important property of feldspar is its tendency to form the crystalline mineral leucite when melted.Leucite:Large coefficient of thermal expansion (20-25 ppm/0C.)thermally compatible with dental casting alloys.Strengthening material.KAOLIN is a clay - Al2O3.2SiO2.2H2O It is a hydrated aluminium silicateKaolin gives porcelain “Opaqueness”Acts as binderAids in formation of workable massProvides rigidity.
Quartz / silica acts as afiller and strengthening agent. Because it has a high melting point, so also provides a high strength Helps to maintain the form (shape) OF THE PORCELAIN during firing.Glass modifiers modify the properties of ceramics by interrupting the glass network.Lower the softening temperature.Increase the CTE.SADLY…..Decrease viscosity.
Aluminium oxideFunctions:Strength and opacity to the porcelain.increases the viscosity of porcelain during firing.
The translucency of porcelain is not suitable to produce dentin colors in particular, which requires greater opacity than that of enamel colors. Hence an opacifying agent maybe incorporated.
High-fusing porcelain is usually used for the manufactureof porcelain teeth. Main constituent of feldspar is silicon dioxideAluminium oxide increase the viscosity.
Since the potassium ionis about 35% largerThan the sodium ion, he squeezing of the potassium ion into the place formerlyoccupied by the sodium ion creates very large residual compressive stresses.Increases of100% in flexural strength have been achieved with several porcelain productsthat contained a significant concentration of small sodium ions.
MOST COMMON METHOD'l'his rapid cooling produces a skin of rigid glass surrounding a soft (molten) core.
Most Metals expand linearly with temp,, but porcelain do not…Metal will expand in the same amount when heated frm 50 to 60 degreeAs heated frm 200 to 210 degree celcious.
(particularly if porcelain is not glazed porperly).
In this article, factors related to the abrasion of enamel by dental ceramics are critically reviewed. Concepts of physical, microstructural, chemical, and surface characteristics of dental ceramics on wear are presented based on research published since 1950. A PubMed search for key words (wear of enamel and ceramic) was supplemented with a hand search to identify relevant peer-reviewed articles published in English.
Minimized by using lesser binder , proper condensation, build – up of restoration 1/3rd larger than original size firing in successive stages.
Porcelain has a coefficient of expansion slightly less than that of tooth structure. Porcelain and metalThe optimum difference between the twowould be no greater than 1 x 10-6°C. The coefficient ofthermal expansion of porcelain can be increased by the addition of an alkali suchas lithium carbonate., the coefficient ofthe metal can be lowered by adding palladiumor platinum.
1 isby reducing the cross linkages between oxygen and silicon with glass modifiers, such aspotassium oxide, sodium oxide, and calcium oxide. Unfortunately, these modifiers or fluxes also lower the viscosity. restorations shouldmaintain their basic shape during firing. This is accomplished by the use of an intermediate oxide, aluminum oxide, which is incorporated into the silicon-oxygen lattice.3.If too many modifiers are added to the porcelain to disruptthe SiO4 tetrahedra, the glass tends to devitrify, orCrystallize.When a porcelainis fired too many times, it may devitrify, becoming milkyand difficult to glaze.
To get the desired esthetic result,,,, its important that the shade of our res should match with the adjacent natural teeth.Each of these three factors is a variable and, when anyone is altered, the perception of color changes
BECAUSE THIS LIGHT CONTAIN THE MOST UNIFORM BALANCE OF LIGHT WAVELENGTHS.
There are speciallights that are colour corrected to emitlight with a more uniform distribution of colour thatcan be utilised.
, this is because of physiologic limitations of color receptors in the eye which make it difficult to distinguish between similar colours after 30 seconds.
Recently introduced glass ionomer cements are preferred for such restorations.
The shade pilot tooth shade analyser from dentsply features a digital camera linked to a led spectrophotometer.
Most widely used prosthesis system in fixed prosthodontics
To establish a chemical bond between metal andporcelain , a controlled oxide layer must be created on the metal surface.Process ,oxidising.
Mechanical…Presence of surface roughness on metal oxide surface can result in mechanical retention,Chemical is the primary bonding mechanism Presence of adherent oxide layer is essential for good bond formation.oxidising of degassingIn precious metal alloys tin oxide and indium oxide are responsible for the bond and in base metals chromium oxide does this role.In order to have good bonding, the metal subsurface should be free from contamination, cleaned by sandblasting, cleaned in an ultrasonic cleaner, washed and dried, it is then oxidized in the furnace for 5 minutes.
1In this wet porcelain mix is applied with a spatula and vibrated gently till the particles settle down.Excess water is then removed with a tissue paper.This is the most efficient way to remove excess water.2Here ,the wet porcelain mix is smoothened with a spatula to bring the excess water to the surface which is absorbed with a tissue.3The dry powder is placed with a brush on side opposite of wet porcelain,,AS THE WATER IS DRAWN TOWARDS THE DRY POWDERTHE WET PARTICLES ARE PULLED TOGETHER. WTHEVER MAY B THE METHOD USED IT IS IMP,,SURFACE TENSION OF WATER IS THE DRIVING FORCE IN THE CONDENSATION,,AND PORCELAIN SHUD NEVER BE ALLOWED TO DRY OUT UNTIL CONDENSATION IS COMPLETE.
The condensed mass is not inserted directly into the furnace. After preheating for approximately 5 minutes , the porcelain is placed into the furnace, and the firing cycle is initiated.
It is commonly accepted that cooling must be carried out slowly and uniformly.
DENTAL CERAMICS HAVE GLASSY PHASE SURROUNDING A CRSTALLINE PHASEGLASSY PHASE GIVES TRANLUCENCYCRYSTALLINE PHASE GIVES STREGTH/\\99% by volume of crystalline phase.
Leucite reinforcedADVANTAGES Alumina has a high modulus of elasticity (350Aluminous core porcelains have flexural strengths approximately twice that of feldspathic porcelains (139 to 145 MPa). GPa) and relatively high fracture toughness (3.5 to 4 MPa • m0.5), compared to feldspathic porcelains.
There is large mismatch in thermal contraction between leucite (20 to 25 × 10−6/° C) and the glassy matrix (8 × 10−6/° C)content (compared with conventional feldspathic porcelain for metal-ceramic restorations) ) results in the development of tangential compressive stresses in the glass around the leucite crystalsupon cooling, because the crystals contract more than the surrounding glassy matrix. These stresses can act as crack deflectors and contribute to increased resistance of the ceramic to crack propagation. .
IN SLIP CASTING, THE FIRED POROUS CORE IS GLASS INFILTRATED,,,,,MOLTEN GLASS IS DRAWN INTO THE PORES BY CAPPPILAARY ACTION AT HIGH TEMPERATURE,
Because of high level of opacity,,, icz is not used in anteriors.Ics is most translucent. Of threeIcz is the most toughest,,,strength
Cergo fit Cergo fit SPEED100 g : 21ml 100 g : 25 ml
,,,, lithium disilicate (Li2Si2O5) as a major crystalline phase. using the same equipment as for the leucite-based ceramics The amount of porosity after heat-pressing is about 1 vol%. Compared to first-generation leucite-based ceramics, the main advantage of the lithium disilicate–based ceramics is their enhanced flexural strength (300 MPa) compared to leucitebased.andfracture toughness (2.9 MPa • m0.5).
. Dental ceramic technology is one of the fastest growing areas of dental material research and development.
CERAMICS By: DR. BHARTI DUA PG IST YEAR1
CONTENTS1.INTRODUCTION2.HISTORY3.CLASSIFICATION4.COMPOSITION5. STRENGTHNING MECHANISM OF CERAMIC6. PROPERTIES7. SHADE MATCHING GUIDELINES 28. METAL CERAMIC SYSTEMS
9.ALL CERAMIC SYSTEM10.CRITERIA FOR SELECTION AND USE OF DENTAL CERAMICS11.RECENT ADVANCES IN CERAMIC12. REFERENCES13.CONCLUSION 3
DEFINITION1 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 energy1 – G.P.T-8 5
PORCELAIN1 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.G.P.T-8 6
HISTORY2,3,4 Historically, three basic types of ceramic materials were developed; Earthernware, Stoneware, & Whiteware. 8
In 700 B.C. the Etruscans made teeth of ivory and bone that were held in place by a gold framework. By the 10th century A.D, ceramic technology in China had advanced to a highly sophisticated stage. As trade with the far east grew, this infinitely superior material came to Europe from China, during the 17th 9 century.
HISTORY In 1717, a Jesuit missionary Father d’Entrecolles leaked the secret of Chinese porcelain and passed it on to M. de Reamer 1728 – Pierre Fauchard, a French dentist first proposed the use of porcelain in dentistry. By 1825- Samuel Stockton began fabrication of fused porcelain teeth in Philadelphia. 10
HISTORY A significant improvement in the fracture resistance of porcelain crowns was reported by Mc1ean and Hughes in 1965 when a dental aluminous core ceramic was used. 1983-84 – the first castable glass ceramic was introduced by Grossman and Adair called DICOR 1985 – CAD/CAM technique was developed by Mormann and Brandestini 11
The future of dental ceramics is bright because the increased demand for tooth-colored restorations will lead to an increased demand for ceramic- based restorations. 12
( Development of residual compressive stress) Ion exchange Thermal tempering. Thermal compatibility And( Interruption of crack propagation ) Dispersion of crack propagation 27 Dispersion of crystalline phase
Ion Exchange The ion-exchange process is sometimes called chemical tempering. When a sodium containing glass article is placed in a bath of molten potassium nitrate, potassium ions in the bath exchange places with some of the sodium ions in the surface of the glass article and remain in place after cooling. 28
THERMAL TEMPERING It is done by rapidly cooling (quenching) the surface of the object while it is hot and in the softened (molten) state. As the molten core solidifies, it tends to shrink, but the outer skin remains rigid. The pull of the solidifying molten core, as it shrinks, creates residual tensile stresses in the core and residual compressive stresses within the outer surface. 29
THERMAL COMPATIBILITY Ideally the porcelain should be under slight compression in the final restoration. Select an alloy that contracts slightly more than the porcelain on cooling to room temperature. 30
DISPERSION OF CRACKPROPAGATION Ceramic can be reinforced with a dispersed phase of a different material that is capable of hindering a crack from propagating through the material. 31
DISPERSION OF CRYSTALLINEPHASE When a tough , crystalline material is added to glass, the glass is toughned and strengthened because the crack can not penetrate the added crystalline particle. 32
ABRASION RESISTANCE2 Natural tooth - 343 KHN Porcelain 460 – KHN Hence , it causes wearing of natural tooth and metal restorations 35
Enamel wear by ceramics may adversely affect maintenance of the vertical dimension of occlusion and can increase the potential for thermal sensitivity. Based on the literature, it can be concluded that material factors, their proper handling, and control of the patients intrinsic risk factors related to wear are critically important for the reduction of enamel wear by dental ceramics. Oh WS, Delong R, Anusavice KJ.Factors affecting enamel and ceramic wear: A literature review.J Prosthet Dent 2002 Apr;87(4):451-9 36
SHRINKAGE3 Volumetric shrinkage – 28-37% - low fusing porcelain 28-34% - high fusing porcelain Linear shrinkage - 14 % - low fusing porcelain 11.5%- high fusing porcelain 37
COEFFICIENT OF THERMAL EXPANSION (CTE)3 CTE should match tooth structure to minimize shrinkage . 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 10-6/oC 38
Properties necessary for use of ceramics in thefabrication of dentalrestorations5 1. Low fusing temperature2. High viscosity3. Resistance to devitrification 39
COLOUR STABILITY Ceramics are the most stable tooth coloured materials . The metallic oxides used as colorants do not undergo any change in shade after firing is complete . 40
SHADE MATCHING GUIDELINES 2,4 Three factors upon which color is dependent: (1)the observer, (2) the object, (3) the light source. 41
The selection of tooth or restorative shades should be done at the start of a clinical session before the operator’s eyes become fatigued. Have the patient remove lipstick, heavy makeup or large jewelry that may influence the color perception. Do not use operatory light for shade selection. 42
Ideally the clinician should use illumination of northern light from a blue sky. Sunlight near the window can be used. 43
Hold the appropriate shade tab near the tooth to be restored , party covered with the patient’s lip. Shade selection should be done quickly within 30 seconds 45
Try to select the basic hue of the tooth by matching the shade of the patient’s canine, usually the most highly chromatic tooth in the mouth. With the correct hue group selected, work within the group on the shade guide to obtain the proper match. 46
Another factor that is important to the aesthetic qualities is the cementing medium. For example, an opaque material such as zinc phosphate cement, can change the shade of a translucent crown because of its light absorption and its color. 47
METAL CERAMICSMechanical properties Esthetic properties Metal Ceramic
REQUIREMENTS FOR A METAL- CERAMIC SYSTEM 2 High fusing temperature of the alloy. Low fusing temperature of the ceramic.(difference should not be more than 100oC.) The ceramic must wet the alloy readily . Adequate stiffness and strength of alloy core. An accurate casting metal coping is required. Adequate design of restoration is critical. 51
REQUIREMENTS2 Ceramic must have coefficient of thermal contraction closely matching to that of alloys. The optimum difference between the two should not be greater than 1 x 10-6/°C. Metal oxide is necessary to promote bonding . High melting ranges for gold alloys are necessary to prevent sag, creep, or melting of the coping during porcelain firing cycle. 52
BONDING PORCELAIN TO METAL2 Success of a metal ceramic restoration is the development of a durable bond between the porcelain and the alloy. Theories of metal ceramic bonding : Mechanical Chemical interlocking bonding 54
Bond failure classification: O’BrienType I: Metal porcelain: • When the metal surface is totally depleted of oxide prior to firing porcelain, or • When no oxides are available • Also on contaminated porous surface.Type II: Metal oxide- porcelain:• Base metal alloy system.• The porcelain fractures at the metal oxide surface leaving the oxide firmly attached to the metal.
Type III: Cohesive within porcelain:• Tensile fracture within the porcelain when the bond strength exceeds the strength of the porcelain. Type IV: Metal- metal oxide:• Base metal alloys• Due to the overproduction of Ni and Cr oxides• The metal oxide is left attached to ceramic. 56
5.Type V: Metal oxide- Metal oxide•Fracture occurs through the metal because of theoverproduction of oxide causing a sandwich betweenporcelain and metal6. Type VI :Cohesive within metal •Unlikely in individual metal ceramic crowns. •Connector area of bridges.
FABRICATION OF A METAL CERAMIC RESTORATION2,3,4 58
METAL PREPARATION 4 – Sharp angles or pits on the veneering surface of metal- ceramic restoration should be avoided . Convex surfaces and rounded contours should be created so that the porcelain is supported without development of stress concentration. The intended metal-ceramic junction should be as definite ( 90 0 ) and as smooth as possible. The metal framework should be sufficiently thick to prevent distortion during firing.( min 0.3 mm for noble metals & 0.2 mm for base metals) 59
Metal Preparation To establish a chemical bond between metal and porcelain , a controlled oxideOXIDIZING layer must be created on the metal surface. The oxide layer is obtained by placing the substructure on a firing tray , inserting it into the muffle of a porcelain furnace and raising the temperature to a specified level that exceeds the firing temperature of porcelain. 60
CONDENSATION The process of packing the powder particles together and removing excess water is known as condensation. During this step , the porcelain powder is mixed with distilled water or any other liquid binder and applied on the metal substrate in subsequent layers. 61
CERAMOSONIC CONDENSERULTRASONIC CONDENSING UNIT FOR PORCELAINBUILD-UP 63
Condensing porcelain 1. Build up porcelain using a brush or spatula and set the tweezers against the vibrating platform intermittently. Remove the moisture leaking up out of the porcelain with a tissue paper. 64
CONDENSATION Opaque porcelain applicationOpaque porcelain is applied first to mask the metal, to give the restoration its basic shade, and to initiate the porcelain- metal bond. 65
No attempt should be made to thoroughly mask the metal with this initial application. It is intended to completely wet the metal and penetrate the striations created by finishing. The coping is dried and fired under vacuum The second application of opaque porcelain should mask the metal . The powder and liquid are mixed to a creamy consistency and applied to the coping with a brush in a vibrating motion. opaque porcelain is condensed to a thickness of O.3mm and fired. 66
Dentin and Enamel Porcelain Application Mix dentin porcelain to a creamy consistency with distilled water or the manufacturers recommended liquid. Then apply it over the opaque with a sable brush or small spatula, starting at the gingivofacial of the coping, which is seated on the working cast. 67
First develop the full contour of the crown in dentin porcelain with a brush. Vibrate the porcelain to condense it, absorbing the liquid with tissue. The completed buildup should be over contoured . When the porcelain is condensed and dried to a consistency of wet sand, carve the dentin back to allow the placement of the enamel porcelain. 68
Apply the enamel porcelain to restore the full contour of the restoration. When completed, the restoration should be slightly larger incisally to compensate for the shrinkage . Overall, make the crown about one-fifth larger than the desired size to compensate for the 20% shrinkage that will occur during firing . 69
FIRING Firing is carried out for fusing (sintering) the porcelain. The compacted mass is placed on a fire clay tray and inserted into the muffle of the ceramic or porcelain furnace. PREHEATING It is first placed in front of the muffle of a preheated furnace and later inserted into the furnace(5 min) If placed directly into the furnace, the rapid formation of steam can break up the condensed mass. 70
TYPES OF FIRING AIR FIRING VACCUM FIRING GAS FIRING 71
HOW VACUUM FIRING REDUCES POROSITY 2 – When the porcelain is placed in the furnace , the powder particles are packed together with air currents around them. As the air pressure inside the furnace muffle is reduced to about one-tenth of atmosphere pressure by vacuum pump, the air around the particles is also reduced to this pressure. As the temperature rises, the particles sinter together, and closed voids are formed within the porcelain mass. The air inside these closed voids is isolated from furnace atmosphere. 72
At a temperature of about 55OC, below the upper firing temperature, the vacuum is released and the pressure inside the furnace increases a factor of 10, from 0.1 to 1 atm. Because the pressure is increased by a factor of 10, the voids are compressed to one-tenth of their original size, and the total volume of porosity is accordingly reduced. Not all air can be evacuated from the furnace , therefore a few bubbles are present in vacuum sintered porcelains, but they are markedly smaller than the ones obtained by air firing. 73
TEMPERATURE TIMEOXIDATION 9300C 15 MINBASE PASTE 960OC 19 MINSHADE PASTE 975OC 16 MIN 74
TEMPERATURE TIMEDENTINE 9350C 19 MINENAMEL 935OC 19 MINGLAZE 930OC 11 MIN 75
COOLING Too rapid cooling of outer layers may result surface crazing or cracking; this is also called thermal shock. Slow cooling is preferred, and is accomplished by gradual opening of the porcelain furnace. 76
PORCELAIN SURFACE TREATMENT 5 Once the desired contours and occlusion have been achieved, the restoration must receive a surface treatment i.e glazingGLAZING - After firing, Porcelains are glazed to a glossy surface. It enhances strength, esthetics and hygiene. Glazed porcelain is much stronger than unglazed. The glaze is also effective in reducing crack propagation. 77
TYPES OF GLAZE –1. Self glaze Porcelains can be self glazed by heating under controlled condition, i.e. it is heated to its fusion temperature and maintained for 5 minutes. it causes only the surface layer to fuse and flow over the surface to form a vitreous layer called glaze. Chemical durability of self glaze is better than over-glaze.2. Over glaze The glaze powder is mixed with liquid, applied over the smoothened crown and fired at temperature lower than that of body. But it should be avoided because it gives - Unnatural appearance Loss of contour and shade modification 78
Glass ceramic: Is a ceramic consisting of a glassmatrix phase and at least one crystal phase that isproduced by the controlled crystallization of the glass.These ceramics are supplied as ceramic ingots whichare used to fabricate the restoration using a lost waxand centrifugal casting technique.DICOR was the first commercially available castableceramic material for dental use.This has a glassy matrix and a crystalline phase.
MICA BASED GLASS CERAMICS DICORDeveloped by The Corning works and marketed bythe Dentsply.International Term DICOR is the combination of themanufacturers names.DICOR is a castable polycrystalline fluoridecontaining tetrasilic mica glass ceramicmaterial, initially cast by lost wax technique andsubsequently heat treated resulting in a controlledcrystallization to produce a glass ceramic material.
COMPOSITION SiO2-45-70% K2O- 20% MgO- 13-30% 55% vol of tetrasilicic flourmica crystals increased strength and toughness increased resistance to abrasion thermal shock resistance chemical durability 85 decreased translucency
Supplied as – DICOR castable ceramic cartridges Special DICOR casting crucibles each contain a 4.1 gm DICOR ingot and DICOR shading porcelain kit.EQUIPMENT REQUIRED –1. DICOR Casting machine2. DICOR Ceramming furnace with ceramming Trays. 86
FABRICATION OF CASTABLE CERAMICS RESTORATION CONSISTS OF MAINLY 2 STEPS –1. CASTING – The glass liquefies at 13700C 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 in a double line casting ring and burned out in a conventional burnout at 9000C for 30 minutes. 87
Glass ingots of castable ceramic material is placed in a special zirconia crucible and centrifugally cast in a electronically controlled DICOR casting machine maintaining the spin pressure for upto 4 minutes and 30 seconds. Transparent glass casting obtained is amorphous and fragile. 88
2.CERAMMING – The cast glass material is subjected 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 glass matrix. 89
METHOD – Transparent casting is embedded in castable ceramic embedment material ( gypsum-based ) and placed in a Ceramming tray in the DICOR Ceramming furnace.CERAMMING CYCLE –6500C-10750C for 1.5 hrs and sustained upto 6 hours. 90
Difference between Dicor and Dicor MGC(machinable glass ceramic)Dicor Dicor MGC55%vol of tetrasilicic 70% vol of tetrasilicicfluoramica crystals. flouramica crystals which are 2 µm in diameterCrystallization done by the Higher quality product that istechnician. crystallized by the manufacturer and provided as cadcam blanks or ingots.Mechanical properties Less translucent than Dicor.similar.
Advantages of Dicor:1) Uniformity and purity of the material.3) Minimal processing shrinkage.4) Good fit.5) Low CTE equal to that of the tooth structure.6) Minimal abrasiveness to the tooth structure.7) Radio opacity like dentin.8)Moderately high flexural strength.(152 MPa)
Disadvantages of DICOR• OPAQUE due to the presence of mica: Chamaleon effect the transparent crystals scatter the incoming light. The light and also its color, is distributed 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 CHAMALEON effect.•Low tensile strength.•Inability to be colored internally•Labour intensive•High cost Indications Inlays, Onlays ,partial tooth coverage
PROPERTIES OF CERAPEARL – CASTING SHRINKAGE is 0.53% COEFFIECIENT OF THERMAL EXPANSION is 11.0 X 10-6/0C Melts at 14600C and flows like a melting glass. The cast material has an amorphous microstructure when reheated at 8700C forms crystalline Hydroxyapetite. Biocompatible: Crystalline structure similar to enamel. Modulus of rupture :150 Mpa. 95
SINTERED CERAMICSLeucite- reinforced feldspathic porcelain: OptecHSPAluminous based porcelain( Pt foil): Vitadur- N TM coreAlumina based porcelain: Hi ceramMagnesia based feldspathic porcelain(Experimental)Zirconia based porcelain: Mirage IIHydrothermal low fusing Ceramics: Duceram LFC.
SINTERED ALL-CERAMIC MATERIALS2,3 Supplied as powders which can be mixed with water to form a slurry. This slurry can be built up in layers on a refactory die to form the restoration. The powders are avaliable in different shades and translucencies. These sintered ceramics are thus similar to the conventional feldspathic porcelains in their method of fabrication. However they are stronger as they are reinforced by crystalline phases. 98
Alumina-Based Ceramic Mclean and hughes (1965) developed Alumina reinforced porcelain core 99 materials
ALUMINOUS CORE CERAMICS They advocated using aluminous porcelain, which is composed of aluminum oxide (alumina) crystals dispersed in a glassy matrix. The technique devised by McLean used an opaque inner core containing 50% by weight alumina for high strength. This core was veneered by a combination of esthetic body and enamel porcelains with 15% and 5% crystalline alumina, respectively and matched thermal expansion. 10 0
The resulting restorations were approximately 40% stronger than those using traditional feldspathic porcelain. Why Alumina? Good Mechanical properties. Interfacial region between alumina and porcelain virtually stress free. Crystals rather than fine powdered alumina used. High modulus of elasticity( 350 Gpa) High fracture toughness( 3.5 to 4 Mpa). Significant strengthening of the core. 10 1
Advantages of aluminous porcelains: Increased flexural strength, Increased elasticity and toughness. Disadvantages of Aluminous porcelain Extensive reduction, dentin preparation. Bonding is limited. High failure rates. 10 2
LEUCITE REINFORCED FELDSPATHIC PORCELAIN In this type , the leucite crystals ( Potassium aluminium Silicate) are dispersed in a glass matrix. The leucite and glass components are fused together during baking process at 10200C. Leucite concentration 50 % wt. Eg .Optec HSP( Jeneric/ Pentron) Higher modulus of rupture and compressive strength. Does not require core unlike aluminous PJC. 10 3
Lack of metal or opaque substructure, Good translucency compared to alumina crowns. Advantages: Moderate flexural strength( 146 Mpa), Ability to be used without special laboratory equipment. Can be etched. Marginal inaccuracy caused by sintering shrinkage.Disadvantages: Potential to fracture in posterior teeth. Increased leucite content :relatively high invitro wear of opposing teeth. Requires a special die material. Uses: Inlays, onlays, crowns for low stress areas and veneers
Magnesia based core ceramic 6 •High expansion core material. •CTE :magnesia 13.5 x10-6/0C. Strengthening: Dispersion strengthening by the magnesia crystals in a vitreous matrix. Crystallization within the matrix.( Precipitation of fosterite crystals.)
Magnesia based core porcelain 6Advantages 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.
Zirconia based feldspathic porcelains ( Sintered) 6 Mirage II( Myron International, Kansas City). Tetragonal Zirconia fibers Advantages – •Fracture toughness •Thermal shock resistance Disadvantages: Properties such as translucency and fusion temperature can be adversely affected.
Slip Cast Ceramics Alumina based( In- Ceram) In – Ceram Spinell In – Ceram Zirconia In- Ceram 2000. 109
SLIP CAST ALL CERAMIC MATERIALS2 Slip-casting involves the condensation of an aqueous porcelain slip on a refractory die. The porosity of the refractory die helps condensation by absorbing the water from the slip by capillary action. 110
SLIP CASTING _ Is a process used to form “green” ceramic shapes by applying a slurry of ceramic particles and water or a special liquid to form a porous substrate( such as die material), thereby allowing capillary action to remove water and densify the mass of deposited particles.Green state – refers to an as- pressed condition before sintering. 11 1
The starting media in slip-casting is a slip that is an aqueous suspension of fine alumina particles in water with dispersing agents. The slip is applied onto a porous refractory die, which absorbs the water from the slip and leads to the condensation of the slip on the die. The piece is then fired at high temperature (1150° C). The refractory die shrinks more than the condensed slip, which allows easy separation after firing. 11 2
The fired porous core is later glass-infiltrated, a unique process in which molten glass is drawn into the pores by capillary action at high temperature. Materials processed by slip-casting tend to exhibit lower porosity and less processing defects than traditionally sintered ceramic materials. 113
In ceram is provided as one of the three core ceramics In-ceram spinel (ICS) In-ceram alumina(ICA) In-ceram zirconia (ICZ) Core of ICS- MgAl2O4 Core of ICA- 70wt% alumina infiltrated with 30wt% sodium lanthanum glass Core of ICZ- 70wt% alumina and 30wt% zirconia. 114
INDICATIONS2 ICS-anterior single unit inlays, onlays, crowns and veneers ICA-anterior and posterior crowns and anterior three unit FPD’s ICZ-posterior crowns and posterior FPD’s 115
LABORATORY PROCEDURE In-Ceram – is based on slip-casting of an alumina core with its subsequent glass infusion. An impression of the master cast preparations is made with an elastomeric impression material. A special gypsum supplied with In-Ceram is then poured into the impression to produce the die onto which In-Ceram alumina is applied. 116
Alumina powder(38 g) is mixed with 5ml of deionized water supply. One drop of a dispersing agent is added to help create a homogenous mixture of alumina in the water. one-half of the alumina is added to a beaker containing the water/dispersant and then sonicated for 3 minutes in a vitasonic. This initiated the Dispersion process. A second quantity of powder equal to one-half of the remaining amount is then added to the beaker and sonicated again for 3 minutes. 11 7
The remaining powder may be added and sonicated for 7 minutes , during the last minute, a vacuum is applied to remove air bubbles – this solution of alumina is referred to as “ SLIP” ,which is then painted onto the gypsum die with a brush. The alumina core is then placed in the furnace and sintered using program 1 – slow heating of approx 2OC/min to 120OC to remove water and the binding agent. 118
Second stage of sintering involves a temperature rise of approx 20OC/min to 1120OC for 2 hours to produce approximation of particles with minimal shrinkage of the alumina. 119
Advantages of the glass infiltrated systems: High flexural strength and fracture toughness.In-ceram alumina(ICA); STRENGTH- 600 MPa ,TOUGHNESS- 6In-ceram zirconia (ICZ); STRENGTH-900 MPa , TOUGHNESS-9 Esthetics. Biocompatibility. Ability to be used with conventional luting cements. 12 0
Disadvantages of glass infiltrated systems. High chemical solubility > 1000micro gms/cm2 Technique sensitive High cost. Long time period for fabrication(15-16 hrs for single crown) 12 1
Contraindication – If functionally appropriate design of the restoration is not ensured: Inadequate preparation Bruxism. Severe discoloration of prepared teeth. 12 2
HOT-PRESSED CERAMICS (Leucite based) – IPS Empress and Optec OPC. Hot-pressed ceramics are becoming increasingly popular in dentistry. The restorations are waxed, invested, and pressed in a manner somewhat similar to gold casting. Marginal adaptation seems to be better with hot-pressing than with the high-strength alumina core materials. 125
Most hot-pressed materials contain leucite as a major crystalline phase, dispersed in a glassy matrix. The crystal size varies from 3 to 10 µm, leucite content is 35% Glass65% Leucite is used as a reinforcing phase due to the tangential stresses it creates within the porcelain. 126
IPS Empress 6Uses a leucite (40 – 50 %) reinforced feldspathicporcelain. LEUCITE CRYSTALS ARE USED BECAUSE – they improve fracture toughness & strength. Conventional lost wax technique is used,except that it uses special investment and aprolonged burn out cycle. 12 7
Advantages: 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.
DISADVANTAGES Potential to fracture in the posterior areas. Need to use resin cement to bond the crown micromechanically to the tooth structure. Expensive equipment. 129
1. DIE PREPARATION The Cergo die spacer (one layer of approximately 15 μm in thickness) or the colored die spacer (two layers of approximately 15 μm in thickness) is used as a placeholder for the cementing gap. In the case of crowns, a special spacer fluid is applied to within 1 mm of the preparation margin on the die. 131
2. WAX MODELING Use only wax materials that burn out without residue. Use Isolit isolating liquid. For anterior teeth, the wall thickness of the wax model must be at least 0.7mm. Thickness of the framework should be more than 50% of the thickness of the veneer in the case of pressable ceramics 132
3. SPRUEING The wax models are sprued with wax sprues (5– 6 mm long for the Cergo press ceramic furnace, 2 – 3 mm for the Multimat Touch&Press). For smaller inlays and copings, the recommended sprue diameter is 3.0 mm, while it is 3.5 mm for more voluminous restorations. 133
4. INVESTING TECHNIQUE Place the muffle ring on the muffle former. Mix the investment material (Cergo fit or Cergo fit SPEED) as per the manufacturer’s instruction. Vibrate lightly into the muffle, avoiding bubble formation, until all objects are completely covered with investment. Top off the muffle without vibrating. 134
5. PRE-HEATING When using Cergo fit SPEED investment, you may place the muffle directly into the oven pre- heated to 850 ºC after a setting period of 15 minutes. 135
6. PRESSINGMaximum of 2 ingots can be used.If wax weight is less than 0.6 gms---- use one ingotIf wax weight is 0.61gm-1.4gms------ use two ingots 136
BURNOUT PROCEDURE After the investment has set for 15 to 20 minplace the ring in 8500C45 min for small ring60 min for large ring 137
7. DIVESTING Make a deep cut into the investment compound, preferably using a diamond-covered and sintered large carbide disc or(less costly) a carbide disc for metal castings. Separate the part of the muffle containing the alumina pressing die from the rest of the muffle using a plaster knife or, preferably, by turning in opposite directions. 138
7. DIVESTING Use a jet polisher (50 μm, 4 bar) or glass beads to remove the investment all the way to the pressed objects. Once the objects have become visible, continue abrading across the area using reduced pressure (2 bar). Clean the alumina pressing die using alumina abrasive and rinse. Do not use alumina for air- abrading. Do not concentrate the air- abrading force on small areas. 139
Lithium Silicate based 6 IPS Empress 2 is a recently introduced hot-pressed ceramic. The major crystalline phase of the core material is a lithium disilicate.( 85%) The material is pressed at 920° C (1690° F) and layered with a glass containing some dispersed apatite crystals . The initial results from clinical trials seem quite promising and may have application for anterior three-unit fixed partial dentures. 14 0
The equipment consists of a computer integrated imaging and milling system, with the restorations designed on the computer screen. At least three materials can be used with this system: Cerac Vitablocs mark 1 Cerac vitablocs mark 2 Dicor MGC 14 7
CERAC system consists of – 1. A 3D video camera 2.An electronic image processor with memory unit 3.A digital processor ( computer) connected to 4.A miniature-milling machine ( 3-axis machine) 148
CEREC1 6 Fabrication of simple inlays. Very sharp internal angles of the restorationscould not be administered. Large grinding wheels associated with theoriginal CEREC system. The occlusal surface cannot be fabricated withCEREC 1.
CEREC 2 6 CEREC2 was significantlyimproved. Addition of a further cylindricalgrinder Allowing the addition of occlusalpits and fissures. Concave and biconvex contouringof veneers. Occlusal surface can be groundwith CEREC2
CEREC 3 6 Radiocontrolled operating system whereby the design and milling chamber units can be deployed separately. Data acquisition and milling to be carried out simultaneously. The milling unit of CEREC 3 is also equipped with laser scanner A cylindrical floor and wall and a tapered cylindrical rotary diamondmilling tool( coated with 64 µm-grit diamonds) The angle of taper, which is 450, which is used to shape the occlusalsurface of the restoration. Simplifies occlusal and functional registration
CEREC 3D6 latest version. allows a 3D view of the preparation and proposedrestoration. “ Self Adjusting Crown” automated occlusion tool. Superior marginal fit.Precise ProximalContacts.
Celay System uses a copy milling technique to manufacture ceramic inlays or onlays.A resin pattern is fabricated directly on the prepared tooth or on a master, the pattern is used to mill a porcelain restoration. 15 3
As with the Cerec system, the starting material is a ceramic blank available in different shades This material is similar to Vita Mark II ceramic, used with the Cerec 2 system. Marginal accuracy seems to be good, a little better than the Cerec 2 system. 154
Procera AllCeram System6 - The Pro cera AllCeram system involves an industrial CAD/ CAM process. The die is mechanically scanned by the technician, and the data are sent to a work station where an enlarged die is milled using a computer-controlled milling machine. This enlargement is necessary to compensate for the sintering shrinkage. Aluminum oxide powder is then compacted onto the die, and the coping is milled before sintering at very high temperature (>1550° C). 15 5
The coping is further veneered with an aluminous ceramic with matched thermal expansion. The restorations seem to have good clinical performance and marginal adaptation, provided the scanning is done skillfully. They may be suitable for posterior crowns and FPDs, although long-term data are needed. 15 6
Lava System 6 – In a Lava System , a CAD/CAM procedure is used for the fabrication of zirconia frameworks all ceramic systems. The preparations are scanned and frameworks are milled from presintered zirconia blanks.Non contact optical scanner LAVA THERM Lava milling unit 15 7
Lava System 6– The size of the frameworks is precisely increased to allow for the shrinkage that occurs during sintering. Once a framework has been sintered, it is veneered with layered esthetic porcelains in a manner similar to that for the metal ceramic technique.Non contact optical scanner LAVA THERM Lava milling unit 15 8
CERCON Master models are prepared in the same way as when fabricating crowns and bridges using precious dental alloys. DeguDent Cergo die spacer (Order no. 6590 0001) is ideal as a spacer. One coat (thickness approx. 15 μm) of the die spacer is applied to the preparation surface of the die to approx. 1mm short of the preparation margin to allow a gap for the cement. 159
Single crowns in the anterior region should have 0.3 mm wall thickness with a 0.2 mm marginal edge.Single crowns in the posterior region should 0.4 mm wall thickness with a 0.2 mm marginal edge. Secure the pattern in the model frame. 160
Powdering Remove the model frame from the spindle. Cover the pattern and sticks with scanning powder. 161
THE TECHNIQUE – Cercon eyeMeans of data acquisition-Scanner 162
SINGLE VISIT CROWN (CAD/CAM) – Using CERAC 3D CEREC 3D uses CAD/CAM technology, incorporating a camera, computer and milling machine in one instrument. The dentist uses a special camera to take an accurate picture of the damaged tooth. This optical impression is transferred and displayed on a color computer screen, where the dentist uses CAD technology to design the restoration. Then CAM takes over and automatically creates the restoration while the patient waits. Finally, the dentist bonds the new restoration to the surface of the old tooth. 167 www.drsimonrosenberg.com www.dentsply.com
Before AfterWhat Are the Advantages CEREC 3D Offers?•The dentist performs the restoration in a single session,usually in about one-two hour(s).•No need for the dentist to make an impression and send it toa lab•No return visits for the patient•The restoration is natural looking, as it is made out of tooth-colored ceramic material 168
Before AfterWhat Are the Advantages CEREC 3D Offers? •Ceramic material is biocompatible, high- grade, anti-abrasive and plaque-resistant. •Metal-free -- no silver-colored fillings. •Allows dentist to save more of the healthy tooth •Extremely precise 169
CONCLUSION The difference with & without Ceramics is self evident
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