CERAMICS and its properties,introductyion on ceramica ceramics.pptx

ceramics

1. DENTAL CERAMICS. ( INTRODUCTION AND PORCELAIN FUSED TO METAL CROWNS). PRESENTED BY : DR. MANSI DHIRAN. MDS I DEPT. OF PROSTHODONTICS. .

2. CONTENTS. INTRODUCTION. HISTORY. ADVANTAGES AND DISADVANTAGES. CLASSIFICATION. BASIC STREUCTURE. PROPERTIES. METAL CERAMIC CROWN. METAL CERAMIC BOND. CERAMICS IN PFM. METALS IN PFM. FABRICATION. STRENGTHENING. CONCLUSION. REFERENCES.

3. INTRODUCTION. CERAMICS : Compounds of one or more metals with a non-metallic element, usually oxygen . The word Ceramic is derived from the Greek word " keramos" , which literally means 'burnt stuff, but which has come to mean more specifically a material produced by burning or firing. The American Ceramic Society had defined ceramics as inorganic, non-metallic materials , which are: crystalline in nature compounds formed between metallic and nonmetallic elements such as aluminum & oxygen (alumina - Al2O3), calcium & oxygen ( calcia - CaO ), silicon & nitrogen (nitride- Si3N4). Datla , Srinivasa & Alla , Rama Krishna & Alluri, Venkata & P, Jithendra & Konakanchi , Anusha. (2015). Dental Ceramics: Part II – Recent Advances in Dental Ceramics. American Journal of Materials Engineering and Technology. 3. 19-26. 10.12691/materials-3-2-1.

4. HISTORY. Ceramic-like tools have been used by humans since the end of the Old Stone Age around 10,000 B.C. to support the lifestyles and needs of fisher-hunter-gatherer civilizations. The first porcelain tooth material was patented in 1789 by de Chemant, a French dentist in collaboration with Duchateau , a French pharmacist. In 1808 , Fonzi, an Italian dentist, invented a "terrometallic" porcelain tooth held in place by a platinum pin or frame. Planteau , a French dentist, introduced porcelain teeth to the United States in 1817 , and Peale, an artist, developed a baking process in Philadelphia for these teeth in 1822 . Charles Land introduced one of the first ceramic crowns to dentistry in 1903. The first commercial porcelain was developed by VITA Zahnfabrik in about 1963.

5. HISTORY 1965 -Mc Lean & Hughes used glass- alumina composite instead of feldspar porcelain resulting in stronger restorations. Improvement in all ceramic systems developed by controlled crystallization of a glass (Dicor) was demonstrated by Adair and Grossman ( 1984 ). 1989 -The concept of All-Ceramic post & core was introduced using Dicor glass-ceramic initially, followed by In-cream, IPS Empress and Zirconia ceramics. New generation of ceramics, including Cercon, Lava, In Ceram Zirconia, IPS Empress2, and Procera All Ceram were used for ceramic prostheses. Kelly JR. Nishimura I. Campbell SD. Ceramics in dentistry: Historical roots and current perspectives. J prosthet dent 1996:75 18-32.

6. ADVANTAGES AND DISADVANTAGES . Advantages : - Biocompatible as it is chemically inert. -Excellent esthetic (long lasting). Thermal properties are similar to those of enamel and dentin. High Compressive Strength. Disadvantages : -High hardness. -Abrasion to antagonist natural dentitions and difficult to adjust and polish. -Low tensile strength so it is brittle material.

7. Application of DENTAL 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.

8. CLASSIFICATION (CRAIG). 1) Based on the Application: Metal-ceramic : crowns, fixed partial prostheses. All-ceramic : crowns, inlays, onlays, veneers, and fixed partial prostheses. Additionally ceramic orthodontic brackets, dental implant abutments, and ceramic denture teeth. 2) Based on the Fabrication Method- Sintered porcelain : Leucite, Alumina, Fluorapatite. Cast porcelain : Alumina, Spinel. Machined porcelain : Zirconia, Alumina, Spinel. 3) Based on the Crystalline Phase- Glassy (or vitreous) phase. Crystalline phases.

9. CLASSIFICATION (ANUSAVICE). 1) Uses or Indications: Anterior and posterior crown, veneer, post and core, fixed dental prosthesis, Ceramic stain, Glaze. 2) Processing method: casting, sintering, partial sintering, glass infiltration, slip casting and sintering. hot-isostatic pressing. CAD-CAM milling, and copy milling

10. 3) Based on Principle Crystal Phase: a) Silica glass, b) Leucite based feldspathic porcelain, c) Leucite-based glass- ceramic. d) Lithia disilicate-based glass-ceramic, e) Aluminous porcelain. f) Alumina g)Glass-infused alumina, h) Glass-infused spinel, i) Glass-infused alumina/zirconia, j) Zirconia. 4) Microstructure: amorphous glass/ non-crystalline, crystalline, crystalline particles in a glass matrix. 5) Translucency: opaque, translucent, Transparent. 6) Fracture resistance: low, medium, High. A New Classification System for All Ceramic and Ceramic like Restorative Materials Stefano Gracis , DMD, MSDa /Van P. Thompson, DDS, PhDb /Jonathan L. Ferencz , DDSc /Nelson R.F.A. Silva, DDS, MSc, PhDd Estevam A. Bonfante , DDS, MSc, PhDe .

11. Classification based on sintering temperature.

12. BASIC STRUCTURE. Basically porcelain is a type of glass - three dimensional network of silica (silica tetrahedral). Since Pure glass melts at too high temperature Modifiers are added to lower the fusion temperature - Sodium or potassium. But this weakens the strength and make it brittle.

13. COMPOSITION. Dental Ceramics are mainly Composed of Crystalline Minerals and Glass Matrix.

14. PROPERTIES. Dental ceramics exhibit excellent biocompatibility with the oral soft tissues and are also chemically inert in oral cavity. Ceramics are good thermal insulators and their coefficient of thermal expansion is almost close to the natural tooth. Dental ceramics possesses very good resistance to the compressive stresses, however, they are very poor under tensile and shear stresses. This imparts brittle nature to the ceramics and tend to fracture under tensile stresses. Defects may arise in the form of micro-cracks of sub-millimeter scale; during fabrication of ceramic prostheses and also from application of masticatory forces in the oral cavity

15. OPTICAL PROPERTIES: Translucency is another critical property of dental porcelains. Incisal porcelains >body >opaque porcelains. Dental porcelains are translucent because there are no free electrons and can be colored by pigments such as metallic oxides to match the shade of teeth. Since the outer layers of a porcelain crown are translucent, the apparent color is affected by reflectance from the inner opaque or core porcelain. The thickness of the body porcelain layer determines the color obtained with a given opaque porcelain. The colors of commercial premixed dental porcelains are in the yellow to yellow-red range . In an all-ceramic restoration, incidental light is transmitted and partially diffused through. On the other hand, when entering a PFM restoration, light is primarily reflected. Raptis , Nicolas & Michalakis , Konstantinos & Hirayama, Hiroshi. (2006). Optical behaviour of current ceramic system. The International journal of periodontics & restorative dentistry. 26. 31-41.

16. METAL CERAMIC RESTORATIONS. Also known as Porcelain fused to metal (PFM). The porcelain-fused-to-metal (PFM) crown was developed in the late 1950s by Abraham Weinstein. It has the advantage of being esthetic as well as adequate strength. Most commonly used. Benefits of metal-ceramic prostheses: 1) The most outstanding advantage of metal-ceramic restorations is their resistance to fracture. 2) With metal occlusal surfaces, the fracture rate in posterior sites could be reduced further. 3) Less tooth structure needs to be removed to provide the proper bulk for the crown.

17. 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.

18. 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): forms an oxide layer.

19. FAILURE OF METAL CERAMIC BOND. Cohesive failure : Porcelain-porcelain, metal- metal, oxide-oxide. Adhesive failure : Porcelain-oxide, metal-oxide, metal-porcelain. Mixed failure : Any combination of the previous failures.

20. CERAMICS FOR METAL-CERAMIC RESTORATIONS. Must fulfil five requirements : 1) simulate the appearance of natural teeth, 2) fuse at relatively low temperatures, 3) have thermal expansion coefficients compatible with alloys used for metal frameworks, 4) Compatible in the oral environment, 5) Have low abrasiveness. Composition : silica (SiO2), alumina (Al2O3), sodium oxide (Na2O), and potassium oxide (K2O)Opacifiers (TiO2, ZrO2, SnO2),Various heat-stable colouring oxides. Small amounts of fluorescing oxides (CeO2)-appearance of the dentin/enamel complex structure.

21. METAL FOR COPING OF PFM CROWN. 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. Different Metals such as Base Metal Alloys ( Cobalt, Nickel, Chromium), Titanium Alloys and Gold Alloys Can be Used.

22. FABRICATION OF METAL CERAMIC CROWN. 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.

23. 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. Brushing.

24. Vibration : Mild vibrations are used to densely pack the wet powder upon the underlying matrix. The excess water comes to the surface and is blotted with a tissue paper. Spatulation: A small spatula is used, to apply and smoothen the wet porcelain. This action brings excess water to the surface where it is removed. Brush technique: The dry powder is placed by a brush to the side opposite from an increment of wet porcelain. As the water is drawn toward the dry powder, the wet particles are pulled together.

25. 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. The Cut-Back technique is used for monolithic crowns. Cut-back means the reduction of the incisal edge of the artificial anterior tooth with simultaneous individual layering and firing of ceramics based on the anatomical and aesthetic characteristics of the neighboring teeth. https://www.caddent.de/en/wiki/cut-back-technique

26. FIRING OR SINTERING. It is to fuse the particles of porcelain powder producing hard mass. After the condensation and building of a crown it is fired to high density and correct form. At this stage the green porcelain is introduced into the hot zone of the furnace and the firing starts, the glass particles soften at their contact areas and fuse together. This is often referred to as sintering.

27. The condensed porcelain mass is placed in front of or below the muffle of a preheated furnace at approximately 650 °C for low-fusing porcelain. This preheating procedure permits the remaining water to evaporate. After preheating for approximately 5 minutes, the porcelain is placed into the furnace and the firing cycle is initiated. As sintering of the particles begins, the porcelain particles bond at their points of contact and the structure shrinks and densifies. As the temperature is raised, the sintered glass gradually flows to fill the air spaces. Air becomes trapped in the form of voids because the fused mass is too viscous to allow all of the air to escape. Glazing and Finishing Dental Porcelain: A Literature Review Ahed Al Wahadni , BDS, MDSc , PhD, D. Muir Martin, BDS, MDSc , FDS.

28. VACUUM FIRING. During vacuum firing, porcelain powder particles are packed together with air channels around them. As the air pressure inside the furnace is reduced to about one tenth of atmospheric pressure by the vacuum pump , the air around the particles is also reduced to this pressure. As the temperature rises, the particles sinter together, and closed pores are formed within the porcelain mass. At a temperature about 55 °C below the sintering temperature, the vacuum is released and the pressure inside the furnace increases by a factor of 10, from 0.1 to 1 atm. • Because the pressure is increased by a factor of 10, the pores are compressed to one tenth of their original size, and the total volume of porosity is accordingly reduced.

29. ADVANTAGES OF VACUUM FIRING. There is a general increase in the strength of the porcelain, which probably is more significant in jacket crowns than bonded veneers. The porcelain will have greater translucence. Porcelain for vacuum firing can have a finer and graded particle size, thus increasing the wet strength of the materials and making it less difficult to carve a built-up mass. Shade is markedly affected by vacuum firing. The lessened number of air spaces decreases the internal reflective surfaces. Thus, with opacity reduced and density increased, it becomes impossible to reproduce precisely the shades made with air firing.

30. 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.

31. SINTERING FURNANCE.

32. GLAZING. The glazing is to obtain a smooth surface that simulates a natural tooth surface. It is done either by : 1) Auto glazing: All the constituents on the surface are melted to form a molten mass about 25 µm thick. Thus the porcelain is said to be self glazed. 2) Add on glazing: Applying a glaze to the surface and re-firing. Auto glazing is preferred to an applied glaze. Auto glazed feldspathic porcelain is stronger than unglazed porcelain. The glaze is effective in sealing surface flaws and reducing stress concentrations. •If the glaze is removed by grinding, the transverse strength is reduced and if this surface is left in rough condition it can cause increased wear of enamel.

33. BONDING MECHANISM. Three mechanism have been described to explain the bond between the ceramic veneer and the metal substructure. 1. Mechanical entrapment. 2. Compressive forces. 3. Chemical bonding.

34. 1) MECHANICAL ENTRAPMENT: This creates attachment by interlocking the ceramic into the micro abrasions on the surface of the metal coping which are created by finishing the metal with non contaminating stones / discs and are abrasives. Air abrasion appears to enhance the wettability, provide mechanical interlocking. The use of a bonding agent having platinum spheres 3-6 µm in diameter can also increase the bond significantly. 2) COMPRESSIVE FORCES: These are developed by a properly designed coping and a slightly higher coefficient of thermal expansion than the porcelain veneered over it. This slight difference will cause the porcelain to draw towards the metal coping when the restoration cools after firing. 3) CHEMICAL BONDING: It is indicated by the formation of an oxide layer on the metal. The trace elements like tin, indium, gallium/iron form oxides and bond to similar oxides in the opaque layer of the porcelain.

35. STRENGTHENING.

36. I. METHODS OF STRENGTHENING THE MATERIALS. In the oral environment tensile stresses are usually created by bending forces, and the maximum tensile stresses occur at the surface of the restoration. It is for this reason removal of the surface flaws can result in the increased strength of the material. Smoothing and reducing flaws is one of the reason for glazing of dental porcelain. Strengthening of the brittle materials can be done in a 2 ways. a) Development of residual compressive stresses within the surface of the material. b) Interruption of crack propagation through the material.

37. 1) Development of residual compressive stresses within the surface of the material: One widely used method of strengthening. Strength is gained by virtue of the fact that the residual stresses developed must first be negated by the developing tensile stresses before a net tensile stress develops in the material. THREE of the methods used in achieving this objective are: a) Ion Exchange Mechanism. b) Thermal Tempering. c) Thermal Compatibility Method.

38. A) Ion exchange mechanism : Also called as chemical tempering and is the most sophisticated and effective way of introducing residual compressive stresses. Sodium containing glass 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 particle. This process is best used on the internal surface of the crown, veneer/inlay as the surface is protected from grinding and exposure to acids.

39. B) THERMAL TEMPERING: Rapid Quenching(cooling) the surface while it is hot and in molten state which produces Residual Surface Compressive Stresses. Most Common Method to be used.

40. C) THERMAL COMPATIBILITY: Intentional ( slight) mismatch in their thermal contraction coefficient increases strength of porcelain. (0.5 × 10-6/°C). Applied for PFM.

41. 2) INTERRUPTION OF CRACK PROPAGATION: A) Dispersion of Crystalline Phase: Dispersing Alumina into the glasses or ceramics to strengthen them by interrupting the crack propagation. Produces tangential compressive stress near the crystal matrix interface. Such stresses divert the crack around particle.

42. B) TRANSFORMATION TOUGHENING: PSZ ( Partially Stabilized Zirconia) is capable of undergoing change in crystal structure when placed under stress and can improve the strength. One drawback of PSZ is an opacifying effect that may not be aesthetic in most dental restorations.

43. II) Methods of designing components to minimize stress concentrations and tensile stresses. The design should avoid exposure of ceramics to high tensile stresses. It should also avoid stress concentration at sharp angles or marked changes in thickness. 1) MINIMIZING TENSILE STRESSES: When porcelain is fired onto a rigid material the shape of the metal will influence the stresses set up in the porcelain. If it is a full coverage crown the metal being of higher thermal expansion will contract faster than the porcelain, as a result the metal is placed in tension and the porcelain in compression. For partial metal coverage the junction between the metal and porcelain is therefore a potential site for high stress as the area with only metal will have no balancing compressive forces.

44. 2) REDUCING STRESS RAISERS: -Stress raisers are discontinuities in ceramic structures in brittle materials that cause stress concentration. Abrupt changes in shape/ thickness in the ceramic contour can act as stress raisers. Sharp line angles in preparation and small particle of porcelain along internal margin of crown also causes tensile stresses. If the occlusion is not adjusted properly on a porcelain surface, contact points rather than contact areas will greatly increase the localized stresses. These contact stresses can lead to the formation of the so- called Hertzian cone cracks , which may lead to chipping of the occlusal surface.

45. Advantages OF METAL CERAMIC CROWNS. 1. A properly made metal-ceramic crown is more fracture resistant and durable than most all-ceramic crowns and bridges. 2. A metal coping or framework provides an advantage compared with zirconia-based ceramic prostheses when endodontic access openings through crowns are required. 3. Temporary repairs for ceramic fractures that extend to the metal framework are possible without the need for intraoral sandblasting treatment by using current resin bonding agents.

46. Disadvantages OF METAL CERAMIC CROWNS. Abrasive damage to opposing dentition. Potential for fracture. Excessive exposure to acidulated fluoride can enhance chemical degradation of ceramic surface. Patient may be exposed to siliceous dust by inhalation during grinding. The potential for metal allergy. Not the best esthetic choice for restoring a single maxillary anterior tooth. A dark line at the facial margin of a metal-ceramic crown associated with a metal collar or metal margin is a significant esthetic concern when gingival recession occurs.

47. CONCLUSION. Ceramics have established themselves as a pivotal material in prosthodontics due to their excellent aesthetic properties, biocompatibility, and mechanical strength. Over the years, advancements in ceramic materials have significantly enhanced their application in dental restorations, including crowns, bridges, veneers, and implants. The evolution from traditional feldspathic ceramics to advanced materials like lithium disilicate and zirconia has improved the durability and versatility of ceramic restorations. Ceramics have transformed restorative dentistry by providing reliable, durable, and aesthetically pleasing options for dental restorations. Their continued evolution promises further enhancements in patient care and satisfaction.

48. REFERRENCES. Phillips’ Science of Dental Material 12 th edition. Datla , Srinivasa & Alla , Rama Krishna & Alluri, Venkata & P, Jithendra & Konakanchi , Anusha. (2015). Dental Ceramics: Part II – Recent Advances in Dental Ceramics. American Journal of Materials Engineering and Technology. 3. 19-26. 10.12691/materials-3-2-1. Kelly JR. Nishimura I. Campbell SD. Ceramics in dentistry: Historical roots and current perspectives. J prosthet dent 1996:75 18-32. W. Patrick Naylor, Introduction to Metal - Ceramic Technology - Second edition A New Classification System for All Ceramic and Ceramic like Restorative Materials Stefano Gracis , DMD, MSDa /Van P. Thompson, DDS, PhDb /Jonathan L. Ferencz , DDSc /Nelson R.F.A. Silva, DDS, MSc, PhDd Estevam A. Bonfante , DDS, MSc, PhDe . Glazing and Finishing Dental Porcelain: A Literature Review Ahed Al Wahadni , BDS, MDSc , PhD, D. Muir Martin, BDS, MDSc , FDS. https://www.caddent.de/en/wiki/cut-back-technique . A History of Dental Ceramics, Gregg Helvey , DDS.