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dentistry ceramics

1. Dental ceramics

2. Contents Introduction History Classification Application in Dentistry Composition General Properties Special Types of Porcelain Metal Ceramic Restorations All Ceramic Restorations Conclusion References

3. Introduction Derived from the Greek word ‘ keramos ’, which means ‘ potter's clay ’.

4. According to Craig According to Anusavice Dental ceramic—A specially formulated ceramic material that exhibits adequate strength, durability, and color that is used intraorally to restore anatomic form and function and/or esthetics. The term ceramic is defined as any product made essentially from a nonmetallic material by firing at a high temperature to achieve desirable properties.

5. Definition Ceramics: Compounds of one or more metals with a non-metallic element, usually oxygen; they are formed of chemical and biochemically stable substances that are strong, hard, brittle, and inert non-conductors of thermal and electrical energy. (GPT 9)

6. CLASSIFICATIONS

7. According to Anusavice Firing temperature High fusing : > 1300°C Medium fusing:1100 - 1300°C Low fusing: 850-1100°C Ultralow fusing:< 850°C

8. Use / indications Anterior and posterior crown Veneer post and core fixed dental prosthesis ceramic stain glaze

9. Fabrication technique Casting, sintering, partial sintering Glass infiltration Slip casting and sintering Hot-isostatic pressing, Copy-milling CAD-CAM milling

10. Crystalline phase Alumina based (Optec HSP) Feldspar based (Conventional Ceramics) Lithia disilicate based Leucite based (IPS Empress) Spinel based (Inceram Spinel) Zirconia based

11. Translucency Opaque Translucent Transparent Microstructure Amorphous glass Crystalline Crystalline particles in a glass matrix Fracture resistance Low Medium High

12. According to Craig

13. DCNA 48 (2004) 513-530 dental ceramics: current thinking and trends( J Robert Kelly)

14. New Classification System for All-ceramic and Ceramic-like Restorative Materials By Gracis Et Al, The International Journal Of Prosthodontics Volume 28, Number 3, 2015

15. Applications in dentistry Inlays and onlays Esthetic laminates

16. Short span bridges Single crown

17. Veneer for PFM Artificial teeth Orthodontic bracket

18. Basic structure Ceramics : 2 phases Glassy Phase Provides translucency Makes ceramic brittle Crystalline Phase Added to improve the mechanical properties Newer ceramics (35-90%)

19. Composition Feldspar Primary constituent Minerals composed of potash (K₂O), soda(Na₂O) and silica (SiO₂) 75-85%

20. Kaolin Serves as a binder Consists of Al₂O₃ 2SiO₂ 2H₂O (Hydrated Aluminium Silicate) Increases the moldability of the plastic porcelain Give opacity to the mass

21. Quartz Present in concentrations of 13-14% Provide strength, firmness and improve translucency of porcelain Serves as a framework for other ingredients

22. Alumina Replaces some of the silica in the glass network. Gives strength & Opacity. Alters the softening point and increase the viscosity of porcelain during firing.

23. Glass modifiers Potassium, sodium and calcium oxides Lower the viscosity of glass Increase thermal expansion

24. Opacifying agents Opacifiers are added to increase its opacity in order to simulate color of natural teeth Zirconium oxide Titanium oxide Tin oxide Cerium oxide

25. Pigments • To obtain various shades to mimic natural tooth colour. • Made by fusing metallic oxide with fine glass and feldspar & regrinding to a powder.

26. Metallic oxide colour Cobalt oxide ⎼ blue Manganese oxide lavender Titanium oxide ⎼ yellowish brown Copper oxide green • Iron or nickel oxide ⎼ brown

27. Special Types of Porcelain

28. Opaque porcelain Wet the metal surface and establish a metal porcelain bond Mask the color of the metal substructure Initiate development of the selected shade

29. Body porcelain

30. Dentine porcelain Also described as body, gingival or cervical powders. These are routinely incorporated into areas of a restoration other than the gingival third of a crown. Major determinant of shade of any porcelain restoration.

31. Enamel porcelain Occasionally referred as incisal porcelain. Usually in the violet to gray range and impart a combination of true translucency and illusion of translucency by virtue of their grayish or sometimes bluish hue. Not restricted to any single area of tooth. When fired, enamel porcelains are more translucent that dentin porcelain.

32. Translucent porcelain They do not allow the transmission of all light To give a natural enamel like translucency without substantially altering the body shade.

33. Advantages of dental ceramics Highly esthetic Biocompatibility Thermal insulation Wear resistance Can be formed to precise shapes Ability to be bonded to tooth structure

34. Disadvantages Brittleness Fabrication : technique sensitive Wear of opposing natural teeth Difficult to repair intraorally High cost of fabrication

35. Metal ceramic system

36. Types of Metal Ceramic Systems 1. Cast metal ceramic restorations Cast noble metal alloys (feldspathic porcelain) Cast base metal alloys (feldspathic porcelain) Cast titanium (ultra low fusing porcelain) 2. Swaged metal ceramic restorations Gold alloy foil coping (Renaissance, Captek) Bonded platinum foil coping.

37. Cast metal ceramic restorations

38. Requirements Produce surface oxides for chemical bonding with porcelains. Cte should be slightly greater than porcelain veneer. Melting range higher than the fusing range of the dental porcelain. Must have high temperature strength or sag resistance → the ability to withstand exposure to high temperatures without undergoing dimensional change. Alloy should be biocompatible

39. Composition of metal ceramic Higher alkali content The opaquer powder -High content of opacifiers. Glazes – higher concentration of glass modifiers like soda, potash and boric oxide

40. Nature of metal-ceramic bond Van der Waals forces Mechanical retention/entrapment Compressive forces Direct chemical bonding

41. Van der Waals forces

42. Compressive forces

43. Direct chemical bonding

44. Bond failure Loss of attachment of an oxide layer In compatible materials Failure in oxidation Contamination

45. Manipulation Construction of the cast metal coping or frame work Metal preparation Degassing and oxidizing Opaquer Condensation Firing Glazing

46. Construction of cast metal copings and frameworks Copings are prepared by Casting pure metal Electrodeposition of metal on duplicate die Burnishing & heat treating metal foil on a die Cad- cam

47. Metal preparation Surface finished with ceramic bonded stones Sandblasting with alumina air abrasive Cleaned ultrasonically

48. Degassing and oxidizing Burn off impurities Specific oxides to form on the metal surface Helps in bonding

49. Application of opaquer Careful cleaning metal frame work Thin layer of opaque porcelain (0.2mm) is applied and baked.

50. Condensation Padding or packing of wet porcelain into position The movement of particles is generated by vibration, spatulation, whipping, brush technique or dry powder.

51. Condensation methods

52. Mixing using glass rod

53. Ceramist brushes Spatulas

54. Advantages of ultrasonic condensation: • Reduces the fluid content of layered ceramics; resulting in denser and more vibrant porcelain mass. • Enhances translucency and the shade qualities of the fired ceramic. • Shrinkage can be reduced to below 5% • Time-saving as it reduces the number of compensatory firing cycles

55. Build-up of Cervical Porcelain Build-up of Body Porcelain Cut-back Build-up of Enamel Porcelain

56. Cut back Removing dentine porcelain to allow placement of a layer of enamel

57. Sintering / firing Process of heating, closely packs particles to achieve interparticle bonding and sufficient diffusion to decrease the surface area or increase density of the structure. Steps: Pre-heating the furnace Condensed mass placed Green porcelain is fired

58. Pre-heating (Drying ) • Placing the porcelain object on a tray in front of a preheated furnace at 650 C for 5min for low fusing porcelain and at 480 C for 8min for high fusing porcelains till reaching the green or leathery state.

59. Significance Removal of excess water allowing the porcelain object to gain its strength. Preventing sudden production of steam that could result in voids or fractures.

60. Stages of Maturity of Porcelain during Firing Bisque bake A series of stages of maturation in the firing of ceramic materials depending on the degree of pyrochemical reaction and sintering shrinkage occurring before vitrification (glazing). • Low bisque • Medium bisque • High bisque

61. Low bisque Surface of porcelain is very porous and will easily absorb water. Medium bisque Surface is still porous but the flow of the glass grains is increased and entrapped air will become sphere shaped. High bisque Surface is completely sealed and presents a smooth texture. Overfired porcelain become milky or cloudy in appearance – Devitrification .

62. Glazing Produces smooth, shiny and impervious outer layer, also effective in reducing Crack propagation. 2 ways A dd-on glazing(fusing clear porcelain painted on to the restoration and fired at the fusing temperature) Self glazing – most preferred technique

63. Cooling Carried out slowly Rapid cooling results in cracking or fracture of glass and loss of strength. After firing, placed under a glass cover to protect it from air current and contamination by dirt.

64. Other metal ceramic systems Capillary cast [sintered gold alloy foil ceramic]restoration. Bonded platinum foil- ceramic crown

65. Capillary cast [sintered gold alloy foil ceramic] restoration. Developed by Shoher & Whiteman in 1993 Captek- Capillary casting technique

66. Supplied as thin strips in 2 forms: Captek P, Captek G Captek P – Pt/Pd/Au, porous, internal reinforcing skeleton Captek G – 97.5% Au and 2.5% Ag On heating in furnace – Captek P act as metal sponge, draws in liquid Au Captek G provides gold colour

67. Advantage Thinner foil alloy ,greater thickness of ceramic. Improves esthetics. Less reduction of tooth structure

68. Bonded platinum foil- ceramic crown Platinum foil coping adapted. To improve adaptation pure gold electrodeposited. Followed by minimal deposition of tin. Advantages : Gold enhance vitality thereby esthetics. Tin help in chemical bonding

69. Disadvantages:- Brittle so make clicking sound during contact. Require greater inter ridge distance. Higher density increases their weight.