Dental ceramics

Dental ceramics

1. Dental Ceramics Dr. Deepak K. Gupta

2. Introduction Ceramic is defined as product made from non-metallic material by firing at a high temperature. Application of ceramic in dentistry is promising Highly esthetic stronger , wear resistant , impervious to oral fluids and absolutely biocompatible facebook.com/notesdental

3. Spring-retained maxillary and mandibular dentures of U.S. President George Washington , made from hippopotamus ivory by dentist John Greenwood . Two of the first dentures made for the president using extracted human teeth facebook.com/notesdental

4. Advantages & Disadvatages Advantages Biocompatible as it is chemically inert. Excellent esthetic. Thermal properties are similar to those of enamel and dentine Disadvatages High hardness - abrasion to antagonist natural dentitions and difficult to adjust and polish. Low tensile strength so it is brittle material facebook.com/notesdental

5. APPLICATIONS OF CERAMICS IN PROSTHETIC DENTISTRY Inlays and onlays Esthetic laminates (veneers) over natural teeth Single (all ceramic) crowns Short span (all ceramic) bridges As veneer for cast metal crowns and bridges (metal ceramics ) Artificial denture teeth (for complete denture and partial denture use) Ceramic orthodontic brackets facebook.com/notesdental

6. Classification: Craig Based on the Application M etal-ceramic : crowns, fixed partial prostheses A ll-ceramic : crowns, inlays, onlays , veneers, and fixed partial prostheses . Additionally , ceramic orthodontic brackets, dental implant abutments, and ceramic denture teeth Based on the Fabrication Method Sintered porcelain: Leucite , Alumina, Fluorapatite Cast porcelain: Alumina, Spinel Machined porcelain: Zirconia , Alumina, Spinel Based on the Crystalline Phase Glassy (or vitreous) phase Crystalline phases facebook.com/notesdental

7. Classification: Anusavice uses or indications Anterior and posterior crown, veneer, post and core, fixed dental prosthesis , ceramic stain , glaze composition ; principal crystal phase or matrix phase Processing method casting, sintering, partial sintering glass infiltration, slip casting and sintering, hot- isostatic pressing, CAD-CAM milling, and copy milling firing temperature ultralow fusing, low fusing, medium fusing, High fusing Microstructure amorphous glass, crystalline, crystalline particles in a glass matrix Translucency opaque, translucent, transparent F racture resistance : low, medium, high A brasiveness facebook.com/notesdental

8. Classification of Dental Ceramics by Sintering Temperature facebook.com/notesdental

9. Basic Structure Basically porcelain is a type of glass - three dimensional network of silica (silica tetrahedral) Since Pure glass melts at too high a temperature – Modifiers added to lower the fusion temperature Sodium or potassium But this weakens the strength and make it brittle facebook.com/notesdental

10. Composition It mainly consist of silicate glasses , porcelains , glass ceramics , or highly crystalline solids . Wide variety of porcelain products available in the market So its virtually impossible to provide a single composition for them all. So we will discuss about traditional porcelains - feldspathic porcelains facebook.com/notesdental

11. Composition (Percentage by Weight) of Selected Ceramics) facebook.com/notesdental

12. Basic Constituents: feldspathic porcelain Feldspars are mixtures of (K 2 o. Al 2 o 3 .6SiO 2 ) and (Na 2 o. Al 2 o 3 .6SiO 2 ), fuses when melts forming a glass matrix. Quartz (SiO 2 ), remains unchanged during firing, present as a fine crystalline dispersion through the glassy phase. Fluxes used to decrease sintering temperature . Kaolin act as a binder . Metal oxides : provide wide variety of colors facebook.com/notesdental

13. METAL CERAMIC RESTORATIONS Also known as Porcelain fused to metal ( PFM) It has the advantage of being esthetic as well as adequate strength. Most commonly used facebook.com/notesdental

14. Parts of PFM Core : cast metallic framework. Also known as coping Opaque Porcelain : first layer consisting of porcelain modified with opacifying oxides . Mask the darkness of the oxidized metal framework metal-ceramic bond Final buildup of dentin and enamel porcelain facebook.com/notesdental

15. METAL-CERAMIC BOND Most important requirement for good long-term performance. The bond is a result of chemisorption by diffusion between the surface oxide layer on the alloy and the porcelain. Roughening of surface interface also increases the bond strength increases surface area of wetting for porcelain. Micromechanical retention Noble metal alloys, which are resistant to oxidizing – easily oxidising metal like indium (In) and tin ( Sn ): form an oxide layer facebook.com/notesdental

16. FAILURE OF METAL-CERAMIC BONDING Cohesive failure : Porcelain - porcelain , metal - metal , oxide - oxide . Adhesive failure : Porcelain - oxide , metal - oxide , metal - porcelain . Mixed failure : Any combination of the previous failures. facebook.com/notesdental

17. CERAMICS FOR METAL-CERAMIC RESTORATIONS Must fulfill five requirements: simulate the appearance of natural teeth, fuse at relatively low temperatures, have thermal expansion coefficients compatible with alloys used for metal frameworks, Compatible in the oral environment, have low abrasiveness. Composition: silica (SiO2), alumina (Al2O3), sodium oxide (Na2O), and potassium oxide (K2O) Opacifiers (TiO2, ZrO2, SnO2), Various heat-stable coloring oxides Small amounts of fluorescing oxides (CeO2) - appearance of the dentin/enamel complex structure facebook.com/notesdental

18. METAL FOR COPING OF METAL CERAMIC RESTORATION The alloy must have a high melting temperature to withstand high firing temp of porcelain. Adequate stiffness and strength of the metal framework. High resistance to deformation at high temperature is essential. Adequate thickness of metal. facebook.com/notesdental

19. FABRICATION OF METAL-CERAMIC PROSTHESES Casting of Metal Core Wax framework is fabricated on the die. The framework is cast by lost wax technique. Sandblasting of the cast metal copy. Degassing is done to form oxide layer to improve bonding to ceramic. Processing of Porcelain over metal core Condensation and Build-up Firing or sintering Glazing Cooling facebook.com/notesdental

20. Condensation The plastic mass of powder and water is applied to the metal coping. Function of condensation Adapt the porcelain to the required shape. Remove as much water from the material as possible to decrease firing shrinkage. Methods of condensation Vibration Spatulation Brush facebook.com/notesdental

21. Build-up There are three types of porcelain used a . Opaque porcelain : Mask the color of the cement used for adhesion of the restoration. b. Body or dentin porcelain : Makes up the bulk of the restoration by providing most of the color or shade. c. Enamel porcelain : It provides the translucent layer of porcelain in the incisal portion of the tooth. facebook.com/notesdental

22. FIRING OR SINTERING It is to fuse the particles of porcelain powder producing hard mass. Stages of firing: a. Low bisque stage : Particles lack complete adhesion, low amount of shrinkage occur, and very porous. b. Medium bisque stage : water evaporates with better cohesion to the powder particles and some porosity. Most of the firing shrinkage occurs in this stage. c. High bisque stage: fusion of particles to form a continuous mass, complete cohesion and no more shrinkage. facebook.com/notesdental

23. SINTERING FURNACE facebook.com/notesdental

24. GLAZING The glazing is to obtain a smooth surface that simulates a natural tooth surface. It is done either by: Auto glazing : rapid heating up to the fusion temperature for 1-2 minutes to melt the surface particles. Add on glazing : applying a glaze to the surface and re-firing. Auto glazing is preferred to an applied glaze AUTOGLAZED VENEER CERAMIC facebook.com/notesdental

25. STRENGTHENING: DEFICIENCIES ARE IN DENTAL PORCELAIN facebook.com/notesdental

26. ALL-CERAMIC RESTORATION All-ceramic restorations use a wide variety of crystalline phases. Several processing techniques are available for fabricating all-ceramic restorations: Sintering: Alumina and leucite Heat-pressing: Inceram and IPS impress C asting : Dicor Slip-casting: Inceram Alumina, Iceram spinell , in- ceram zirconica CAD/CAM: VitaBlock , Dicor MGC Lava DVS Cross-Section facebook.com/notesdental

27. Sintered All-Ceramic Materials Two main types of all-ceramic materials Alumina-Based Ceramic developed by McLean in 1965 aluminous core ceramic used in the aluminous porcelain crown high modulus of elasticity and relatively high fracture toughness, compared to feldspathic porcelains Leucite -Reinforced Ceramic 45% by volume tetragonal leucite higher flexural strength (104 MPa ) and compressive strength increased resistance to crack propagation facebook.com/notesdental

28. VITA In-Ceram® SPINELL GLASS POWDER VITA In-Ceram® ALUMINA GLASS POWDER VITA In-Ceram® ZIRCONIA GLASS POWDER facebook.com/notesdental

29. Heat-Pressed All-Ceramic Materials Application of external pressure at high temperature to sinter and shape the ceramic Produce all-ceramic crowns, inlays, onlays , veneers, and more recently, fixed partial prostheses. Ceramic ingots are brought to high temperature in a phosphate-bonded investment mold produced by the lost wax technique . facebook.com/notesdental

30. Heat-Pressed All-Ceramic Materials facebook.com/notesdental

31. Heat-Pressed All-Ceramic Materials Leucite -Based Ceramic First-generation heat-pressed ceramics contain leucite (KAlSi2O6 or K2O • Al2O3 • 4SiO2) as reinforcer Heat-pressing temperatures: 1150° and 1180° C for 20 minutes. ceramic ingots: variety of shades amount of porosity in the heatpressed ceramic is 9 vol % Lithium Disilicate –Based Materials second generation of heat-pressed ceramics contain lithium disilicate (Li2Si2O5) major crystalline phase: 890° to 920° C temperature range 65% by volume of highly interlocking prismatic lithium disilicate crystals amount of porosity after heat-pressing is about 1 vol % Higher resistance to crack propagation facebook.com/notesdental

32. Slip-Cast All-Ceramic Materials Introduced in dentistry in the 1990s Condensation of a porcelain slip on a refractory die - aqueous slurry containing fine ceramic particles. Porosity of the refractory die helps condensation by absorbing the water from the slip by capillary action. Restoration is incrementally built up, shaped Finally sintered at high temperature on the refractory die Usually the refractory die shrinks more than the condensed slip Restoration can be separated easily after sintering Sintered porous core is later glass-infiltrated facebook.com/notesdental

33. Slip-Cast All-Ceramic Materials Alumina and Spinel -Based Slip-Cast Ceramics alumina content of the slip: more than 90%, with a particle size between 0.5 and 3.5 μm 1 st stage: drying at 120° C for 6 hrs 2nd stage: sintering for 2 hours at 1120° C and 2 hours at 1180° C 3 rd stage: porous alumina coping is infiltrated with a lanthanum-containing glass during a third firing at 1140° C for 2 hours 68 vol % alumina, 27 vol % glass, and 5 vol % porosity Indication: short-span anterior fixed partial prostheses facebook.com/notesdental

34. Slip-Cast All-Ceramic Materials facebook.com/notesdental

35. Slip-Cast All-Ceramic Materials Zirconia -Toughened Alumina Slip-Cast Ceramics Zirconia -toughened alumina slip-cast 34 vol% alumina, 33 vol% zirconia stabilized with 12 mol% ceria , 23 vol % glassy phase, and 8 vol % residual porosity. alumina grains appear in darker contrast whereas zirconia grains are brighter Main advantage of slip-cast ceramics: high strength; Disadvantages : high opacity facebook.com/notesdental

36. Machinable All-Ceramic Materials Machining can be done by either 2 ways Soft Machining Followed by Sintering Some all-ceramic materials can also be machined in a partially sintered state and later fully sintered Requires milling of an enlarged restoration to compensate for sintering shrinkage ceramics that are difficult to machine in the fully sintered state, such as alumina and zirconia facebook.com/notesdental

37. Machinable All-Ceramic Materials: Hard Machining Milled to form inlays, onlays , veneers, and crowns using CAD/CAM technology produce restorations in one office visit 3M ESPE Lava Chairside Oral Scanner C.O.S., 3M ESPE; CEREC AC, Sirona Dental Systems, LLC; E4D Dentist, D4D Technologies; iTero , Cadent, Inc facebook.com/notesdental

38. Computer Aided Designing/Computer Aided Milling (CAD/CAM) After the tooth is prepared The preparation is optically scanned and the image is computerized Restoration is designed with the aid of a computer Restoration is then machined from ceramic blocks by a computer-controlled milling machine facebook.com/notesdental

39. CEREC AC, Sirona Dental System facebook.com/notesdental

40. SUMMARY facebook.com/notesdental

41. facebook.com/notesdental

42. References Phillips' Science of Dental Materials- Phillip Anusavice_12 th Basic Dental Materials -2nd.ed Mannapalli Clinical Aspects of Dental Materials Theory, Practice, and Cases, 4th Edition Craig's Restorative Dental Material 13th edition facebook.com/ notesdental

43. THANKS…… Like, share and comment on https://www.facebook.com/notesdental http://www.slideshare.net/DeepakKumarGupta2 facebook.com/notesdental