ALL CERAMICS : Advancements, Applications, and Benefits.pptx

In prosthodontics, ceramics are pivotal for crafting restorations that blend function with aesthetics, essential for repairing or replacing damaged teeth. Various types of ceramics, including traditional porcelain, advanced lithium disilicate, and highly durable zirconia, are used to create crowns, bridges, veneers, and implants. Porcelain offers a natural tooth-like appearance, while lithium disilicate provides both strength and esthetic appeal, ideal for visible areas. The benefits of ceramic materials include their superior esthetics, biocompatibility, and durability. Advances in CAD/CAM technology have further enhanced the precision and customization of ceramic restorations, ensuring that they meet both functional demands and cosmetic desires, making ceramics a cornerstone in contemporary prosthodontic treatments.

1. ALL CERAMICS DR. SATVIKA PRASAD MDS DEPT. OF PROSTHODONTICS MMCDSR

2. CONTENTS Introduction What are ceramics ? Classification of dental ceramics Composition of ceramics Ceramic processing methods Manufacturing of ceramics Fabrication of ceramics Methods of strengthening ceramics Advantages and disadvantages of ceramics Various types of all ceramic systems Criteria for selection and use of dental ceramics Difference between pre- sintered and sintered zirconia Case report Conclusion

3. INTRODUCTION Ceramics is one of the most biological and esthetically acceptable material in dentistry. CERAMIC - first material to be artificially made by humans. Ceramic is derived from the Greek word ‘ keramos ’ which means ‘ potter’s clay ’ . DENTAL PORCELAIN in this domain is superior over polymer and reinforced polymers regarding tooth shade reproduction, translucency, biological compatibility, chemical stability and abrasive resistance.

4. WHAT ARE DENTAL CERAMICS ? Dental Ceramics - An inorganic compound with non metallic properties typically consisting of oxygen and one or more metallic or semi-metallic elements (e.g. – aluminum, calcium, lithium, magnesium, potassium, silicone, sodium, tin, titanium, and zirconium )that is formulated to produce the whole or part of a ceramic based dental prosthesis. - Acc. To Anusavice ADA Specification No.- 69 ISO Specification No.- 6872

5. CLASSIFICATION Based on sintering temperature Based on translucency Based on fracture resistance Classification by microstructure Based on crystalline phase Based on processing of ceramic (fabrication of techniques) Based on framework

6. Based on sintering temperature CLASS APPLICATIONS SINTERING TEMPERATURE RANGE High Fusing Denture teeth, and fully sintered alumina and zirconia core ceramics >1300 ̊C (>2372 ̊F) Medium Fusing Denture teeth, presintered zirconia 1101 ̊C- 1300 ̊C Low Fusing Crown and bridge veener ceramic 850 ̊C – 1100 ̊C (1562 ̊F- 2012 ̊F) Ultralow Fusing Crown and bridge veener ceramic <850 ̊C (<1562 ̊F)

7. Based on translucency Opaque Translucent Transparent

8. Based on fracture resistance Low Medium High

9. Based on microstructure Amorphous glass Crystalline Crystalline particles in a glass matrix

10. Methods of processing the ceramics (fabrication techniques)

11. Based on crystalline phase Alumina based (Optec HSP) Feldspar based (conventional ceramics ) Leucite Based (IPS Empress) Spinel based ( Inceram Spinel)

12. Based on frameworks Alumina – interpertaining phase/ glass infused :- In ceram blocks are fabricated by pressing the alumina based powder into a block shape similar to vitablocs . These blocks are 75% in density and then infused with different shades of glass to make it 100% Alumina – porous:- Fabricated by porous blocks of material. Pressing alumina powder with a binder into a molds produces the blocks

13. Partially stabilized zirconia – porous :- Fabricated similar to alumina blocks. But there are various methods to press the powder into a mold. Uni -axial- involves pressing from one direction Bi-axial- from 2 equal and opposite direction Isostatic - uniform pressing in all directions Partially stabilized zirconia- HIP blocks :- Fully dense zirconia is produced by hot isostatic pressing. Zirconia powder is pressed in a block or the mold, then vacuum sealed in air tight bag and placed into fluid filled chamber then pressure is applied evenly and then sintered to produce zirconia of full density

14. High Isostatic Pressing

15. Composition of ceramics

16. Pigments To obtain various shades to mimic natural tooth colour. Made by fusing metallic oxide with fine glass and feldspar and regrinding to a powder Metallic oxide Colour Iron or nickel oxide Brown Copper oxide Green Titanium oxide Yellowish brown Manganese oxide Lavender Cobalt oxide Blue

17. MANUFACTURING OF CERAMICS Ceramic raw materials are mixed together in a refractory crucible and heated to a temperature well above their fusion temperature. Series of reaction occur After the water of crystallization is lost. Flux reacts with the outer layers of silica, kaolin, and feldspar. Feldspar fuses and intermingles with kaolin and quartz and undergoes decomposition to form glass and leucite .

18. Continuous heating results in total dissolution Then the fused mass is quenched in water Internal stresses within the glass are produced and breaks into fragments frit. The process of blending, melting and quenching the glass is called FRITTING.

19. There are 2 phases of ceramics- GLASSY PHASE ( VITREOUS) Provides translucency Makes ceramic brittle CRYSTALLINE PHASE Added to improve the mechanical properties Newer ceramics (35-90%)

20. Fabrication of ceramic Condensation Sintering Glazing Cooling Manual Condensation Ultrasonic Condensation Glazing

21. Condensation Padding and packing of wet ceramic into position The movement of particles are generated by vibration, spatulation or whipping brush technique and spray opaquing . Build up of cervical portion Build up of body portion Cut back Build up of enamel

22. Sintering / Firing Process of heating closely packed particles to achieve inter-particle bonding and sufficient diffusion to decrease the surface area or increase density of the structure Process of partial fusion of compact glass Steps- Preheating the furnace Placing of condensed mass Green porcelain is fired

23. Pre heating (drying) Placing the porcelain object on a tray in front of a preheated furnace at 650 C for 5 min. for low fusing porcelain and at 480 C for 8 min. for high porcelain till reaching the green or leathery state. SIGNIFICANCE- removal of excess water allowing the porcelain object to gain its green strength Preventing sudden production of steam that could result in voids or fracture

24. 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 pyro chemical reaction and sintering shrinkage occurring before vitrification (glazing) Low bisque Medium bisque High bisque

25. LOW BISQUE- Surface of porcelain is very porous and will easily absorb water Fluxes start to flow MEDIUM BISQUE- Surface is still porous but the flow of the glass grains is increased and entrapped air will become sphere shaped Water evaporate and shrinkage occurs HIGH BISQUE- Surface is completely sealed and presents a smooth texture Fusion between particles to form a continuous mass Over fired porcelain become milky or cloudy in appearance

26. Cooling Produces smooth, shiny and impervious outer layer, also effective in reducing crack propagation 2 ways- Add- on glazing Self glazing - most preferred technique Glazing 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 Add on glazing

27. Instrumentation for finishing and polishing ceramic Instruments 1 Medium to fine grit diamond instruments 2 30 fluted carbide burs 3 Rubber ; abrasive impregnated porcelain polishing points 4 Diamond polishing paste

28. Methods of strengthening ceramics Minimize the effect of stress raisers Develop residual compressive stresses Minimize the no. of firing cycles Ion exchange / chemical tempering Thermal tempering Dispersion strengthening Transformation toughening

29. Minimize the effect of stress raisers- Restoration should be designed in such a way that it avoids exposure of ceramic to high tensile stress Use of minimum thickness of ceramic on occlusal surface Abrupt changes in shape and thickness should be avoided Sharp line angle should be avoided Develop residual compressive stress- As the COTE of metal is high than porcelain it contracts slightly more than that of porcelain on cooling from firing temperature to room temperature. Therefore , leave the porcelain in residual compression which will provide additional strength to the porcelain.

30. Minimize the no. of firing cycles- Multiple firing increases concentration of crystalline leucite which leads to stresses on cooling. Ion exchange / chemical tempering- Effective method of inducing residual compressive stresses Sodium containing glass particle is placed in a bath of molten potassium nitrate Exchange of ions take place Since potassium is 35% larger than sodium ion, squeezing of the potassium ion creates very large residual compressive stresses. Potassium rich slurry, applied to ceramic surface and heated to 450 C for 30 mins .

31. Thermal tempering- Creates residual compressive stresses by rapidly cooling the surface of the object while it is in molten state. Transformation toughening- Strengthening occurs due to a change in crystal structure under stress which prevents crack propagation. E.g.- zirconia= heated between 1470 C and 2010 C Its changes from tetragonal to monoclinic phase at approx. 1150 C

32. Dispersion strengthening- Process of strengthening ceramics by reinforcing them with a dispersed phase of a different material mostly by crystalline substances. E.g.: alumina in aluminous porcelain, spinel in In ceram When crystalline material such as alumina is added to a glass, the glass is strengthened and crack propagation does not take place easily. (Resulted in development of aluminous porcelain for porcelain jacket crowns)

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

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

35. Various types of all ceramic system

36. POWDER CONDENSATION Powder condensation is a traditional method to fabricate feldspathic ceramic restoration. It involves the use of powders, available in various shades and translucencies, and de- ionized water to produce slurry water The moist porcelain powder is applied over a refractory die, copings, or frameworks with a brush, and vibrated and compacted on sponge to remove excess moisture The ceramic restoration is fired under vacuum, which helps to remove the remaining air and improve the density and aesthetics. Ceramics fabricated by this technique have a great amount of translucency and are highly aesthetics and are used mainly as veneering layers. Condensation methods- Manual condensation Ultrasonic condensation E.g.:- VitaN , VitaD , Lava Ceram, Vitadur Alpha, Duceram LFC

37. Advantages of ultrasonic condensation- Reduces fluid content of layered ceramics resulting in denser and more vibrant mass. Enhances translucency and the shade qualities of the fired ceramic Shrinkage can be reduced to 5% Time consuming as it reduces the no. of compensatory firing cycles.

38. CASTABLE CERAMICS

39. 1. CENTRIFUGAL CASTING (DICOR) The first commercially available castable ceramic material for dental use, was Dicor . It is a castable glass that is formed into an inlay, facial veneer, or full crown restoration. {Because of that Dicor has recently been discontinued} ADVANTAGES - Good aesthetics because of chameleon effect Increased strength (55 vol % tetrasilicic fluormica crystals) Increased resistance to abrasion Thermal shock resistance Chemical durability Decreased translucency DISADVANTAGES - Limited use in low stress areas Low tensile strength Inability to be colored internally

40. FABRICATION-

41. 2. Heat Press Ceramics This method uses a piston to force a heated ceramic ingot through a heated tube into a mold , where the ceramic form cools and hardens to the shape of the mold . When the object has solidified, the refractory mold (investment) is broken apart and the ceramic piece is removed. It is then debrided and either stained and glazed (certain inlays) or veneered with one or more layers of a thermally compatible ceramic. E.g.:- IPS Empress, IPS Empress2, IPSe.maxPress

42. IPS Empress It is a leucite – reinforced glass ceramic (SiO2-Al2O3).26IPSEmpress It has a low flexural strength of 112±10 Mpa limiting its use to single unit complete coverage restorations in the anterior region. IPS Empress 2 It is a lithium- disilicate glass ceramic (SiO2-Li2O).7IPS Empress. It has a flexural strength of 400±40 Mpa which is much higher than IPS Empress, and makes it suitable for the usage for fabrication of 3- unit FPD in the anterior region, and can extend to the 2 nd premolar Both are recommended in situations where average to high translucency is needed. They are considered as monochromatic restorations which can be surface characterized to the desired shade and produce comparable aesthetics to the layering techniques.

43. Slip Casting 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, and 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. E.g. – Alumina and spinel based slip cast ceramics Zirconia toughened alumina slip cast ceramics

44. MACHINABLE CERAMICS

45. Computerised design Wax pattern Restoration design Data acquisition Cast & die impression Contact digitalizer laser camera Casting Investing Restoration fabrication Sinter Electrical discharge machine Machine CAD / CAM system Lost wax technique Traditional technique Higher technology

46. Dental CAD/CAM systems use a scanning device, design software, and a milling machine to fabricate coping, frameworks, and restorations from industrially prefabricated ceramic blocks. 2 methods are available to process the ceramic blocks Soft machining OR Green machining Hard machining

47. HARD MACHINING The first method was developed with the intention to machine fully sintered ceramic. However, machining of fully sintered ceramic blocks can result in significant tool wear and residual flaws at the ceramic surface, which can reduce the survival of the ceramic restorations. SOFT MACHINING OR GREEN MACHINING Most recently, CAD/CAM technology has been used with partially sintered ceramics. Requires milling of an enlarged restoration to compensate for sintering shrinkage

48. Computer Aided Designing (CAD) / Computer Aided Milling (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. E.g. CEREC CAD/CAM

49. Stages of fabrication All systems ideally involve 5 basic systems – Computerized surface digitalization Computer aided design Computer assisted manufacturing Computer aided aesthetics Computer aided finishing

50. How material is selected ?

51. To select the suitable type of ceramic dental material, there are important parameters to be considered :- Position – the clinician should consider the fact that the restoration will be used in as an anterior or posterior restoration. For anterior restorations - a more translucent ceramic material with lower mechanical strength lead to favourable aesthetic outcomes. For posterior restoration - where translucency is not of importance a stronger ceramic material such as alumina, zirconia or bonded lithium disilicate are indicated. Design- the clinician should consider the design of the ceramic restoration : single unit v/s splinted. Definitely, multiple splinted unit restorations , a stronger ceramic material is recommended.

52. Strength - a biomechanical risk assessment is necessary to analyse the amounts of expected occlusal forces. For a low to medium stresses – feldspathic OR lithium disilicate ceramics are recommended For medium to high – stronger ceramics such as alumina OR zirconia is recommended Substrate - 3 factors take into account % of enamel left % of dentin left Presence OR absence of discoloration

53. In anterior sextant = presence of >50% enamel substrate left (in the absence of any discoloration) – feldspathic porcelain is used = high translucency and optical properties Amount of enamel left <50% (in the presence of discoloration)- Lithium disilicate ceramic restorations is used In posterior sextants , feldspathic is contraindicated = due to low mechanical properties For alumina OR zirconia restorations- bonding is needed only if the retention is compromised ( <3mm height or a >20 convergence angle)

54. Translucency - to achieve successful aesthetics outcomes, it is important to consider translucency v/s opacity of the ceramic. Aesthetic zone - high translucent material desired Posterior region - high opacity is more favourable

55. GLASS MATRIX CERAMICS It is usually fabricated by precise crystallization of the glass nucleated evenly throughout the glass phase or by embedding one or more crystals in the structure. It provides- Better toughness Better translucency – decrease internal light scattering Improves mechanical strength - by inhibiting crack propagation and growth Less shrinkage Divided into 2 sub categories- Natural materials- feldspathic ceramic Synthetic materials- lithium disilicate ceramic

56. Feldspathic ceramics Known as traditional dental ceramics based on a natural feldspars i.e. potassium/sodium aluminosilicate , kaolin, quartz, some metal oxides. Improved strength of potassium containing feldspars known as Leucite - can be a suitable option for veneering material on metal and ceramic substrates or as reinforced resin bonded glass ceramic cores.

57. Lithium disilicate About 65 vol % dispersed in glassy matrix A glass ceramic ingot is plasticized at 920C and pressed into an investment mold under vacuum and pressure Their strength is TWICE than that of leucite reinforced ceramics Used as – Inlays Onlays Monolithic anterior crowns

58. Resin matrix ceramics Organic matrix + inorganic matrix ( ceramics, glasses, glass ceramics) Since it contains >50% inorganic particles hence comes under dental ceramics. It is suitable choice for CAD/CAM , providing superior properties as it mimics better with the elasticity of dentin and ease of milling and adjusting.

59. Polycrystalline Ceramics Non metallic inorganic ceramic without any glassy phase. Fine grain crystals are tightly arranged – by direct sintering- improve strength- by reducing crack propagation Despite improved mechanical properties, it has limited translucency To enhance the translucency = light scattering should be reduced By decreasing no. of grain boundaries By increasing grain size But by increasing the grain size, mechanical properties will get reduced

60. High strength oxide ceramics High strength ceramics in dentistry includes alumina and zirconia. Besides higher hardness, the superior wear and corrosion resistance along with biocompatibility have turned it into a popular material. The very fine grain size hinders static fatigue and deflects cracks while under load. Alumina ceramics are prone to bulk fractures owing to higher elasticity E.g.: Procera AllCeram , In-Ceram AL ALUMINA (Al 2 O 3 )

61. ZIRCONIA Zirconia is a polycrystalline ceramic with excellent toughness and fatigue resistance. Depending on the temperature it can be formed in 3 phases Cubic tetragonal monoclinic Temp >2300C 1100-2300C room temp – 1100C

62. The tetragonal to monoclinic transformation is accompanied by a shear strain and large (4%) volume increase. This volume increase can close cracks, leading to large increase in fracture toughness of the material. Using this transformation toughening in practice requires that the tetragonal or cubic phases must be stabilized at room temperature by alloying pure zirconia with oxides such as yttrium, magnesium, cerium.

63. It has elasticity similar to stainless steel but superior biocompatibility Decreased plaque retention results in healthier gums after application of zirconia. Physical strength and ability to resist fatigue fracture depends on manufacturing standard that is applied by a specific manufacturer. Yttria - stabilized zirconia (flexural strength >900MPa) is indicated for clinical situations including- Anterior & posterior crowns Implant abutments/crowns 3 unit inlay and onlay bridges Cantilever with a minimum of 2 abutment teeth and a maximum of 1 pontic of no more than 1 premolar width and multilong span ( upto 14 units)

64. To prevent volume expansion during phase transformations, several stabilizing oxides such as yttria or yttrium oxide and magnesium oxide are added to zirconia to stabilize the tetragonal and/or cubic phases by producing multiphase ceramic material known as partially stabilized zirconia (PSZ) Yttria is the most commonly used dopant stabilizing the cubic phase of zirconia due to- its high ionic conductivity at elevated temperature, its high chemical inertness thermal stability hardness.

65. Properties of zirconia High refractive index High hardness High melting point High spatial and thermal stability at elevated temperature Low coefficient of thermal expansion- good resistance to thermal shock Moderate to high thermal conductivity Low wettability of molten metal Clean and round grains – which can be bonded with little materials

66. Tooth preparation guidelines for zirconia For Anterior Thickness = 0.3 mm (ideally between 1-1.5mm) Incisal reduction =1.8-2mm Clear circumferential chamfer finish line with reduction of at least 0.5mm gingival margin 5 tapered angle For posterior Thickness= 0.5mm (ideally between 1-1.5mm) Occlusal reduction= 1.5-2mm Tapered= 4-8 Clear circumferential chamfer finish line with reduction of at least 0.5mm gingival margin

67. Difference between pre- sintered and sintered zirconia

68. Sintered Pre-sintered Zirconia is prepared by three main steps . The Zirconia powder is pressed and pre-sintered. This usually occurs by the manufacturer. The dental lab mills the pre-sintered blank and then sinters the coping or framework to achieve full density. Pre - sintered Compared to pre-sintered zirconia,  the fully sintered zirconia has a lower volume fraction of pores, a greater strength, and an improved resistance to hydrothermal aging . In addition, the fully sintered zirconia can be milled to the final desired dimensions because no further heat treatment, which would result in a dimensional change, is required

69. CASE REPORT Fabrication of zirconia – reinforced lithium silicate ceramic restorations using a complete digital workflow. Rinke S, Rödiger M, Ziebolz D, Schmidt AK. Fabrication of zirconia-reinforced lithium silicate ceramic restorations using a complete digital workflow. Case reports in dentistry. 2015 Sep;2015.

70. A 42 year old women required prosthetic treatment of the lower right 2 nd premolar and 1 st molar. She had insufficient cast partial crowns on 45 and 46 due to which repeated intervention had been necessary due to the loss of retention and secondary caries. Both abutment teeth were vital and overall periodontal situation was stable. The patient opted for replacement of cast gold restoration by a monolithic all ceramic crown on 1 st molar and an all ceramic partial crown fabricated from ZLS (zirconia reinforces lithium silicate) ceramic on premolar.

71. Clinical situation after removal of restoration and caries. Preparation of teeth for digital impression taking, after application of the retraction cords, a top layer of cotton coil is impregnated with epinephrine for haemostasis is applied.

72. Detailed views of the intraoral scanning process and the measuring function for the substance reduction after digital bite registration. Virtual design of the working models (model Builder 2013, 3 Shape, Copenhagen, Denmark)

73. Generatively manufactured working models

74. Construction of monolithic crown and partial crown restorations with CAD software (Dental Designer 2013, 3 Shape, Copenhagen, Denmark) ZLS crown and partial crown directly after the milling process.

75. Removal of the fixation pin and shaping of the ground ceramic restorations with water- cooled diamond instruments

76. Individual colouring of the crystallized ZLS restoration with special staining liquids. Final fit checking with proximal and occlusal contacts on the digitally fabricated working model Final polishing

77. Occlusal adjustments of the restoration during try in with a fine grit size diamond instrument Conditioning of the cementation surface with 5% hydrofluoric acid for 20 seconds. (it increases surface relief in micromechanical bonding of resin cement to ceramic) Application of silane on the cementing surfaces conditioning with 5% hydrofluoric acid. (it increase the wettability and form covalent bonds between ceramic and resin cement)

78. Situation 2 weeks after adhesive luting of the restorations. The good light optical properties of ZLS allow a perfect colour match

79. Newer trends in ceramics :- Next gen. lithium disilicate Unsurpassed strength due to high density micronization Bright and aesthetics Excellent marginal adaptation Highly versatile to use LiSi Press (GC)

80. Translucent zirconia (katana) 4 layer structure Enamel layer (35%) Transition layer 1 (15%) Transition layer 2 (15%) Body (dentin) layer (35%) This innovative multi layered technology creates the smooth transition of color gradiation

81. Celtra Press System ( Dentsply Sirona ) New generation of high strength glass ceramics, Zirconia reinforced lithium silicate Optimize balance of translucency and opalescence Reduced crystal size serves to increase flexural strength Fine microstructure for processing speed efficiencies

82. Conclusion Dental ceramic technology is one of the fastest growing areas of dental material research and development. These restorations offer extremely good aesthetics. But these restorations are technique sensitive and expensive. Careful case selection and proper tooth preparation should be there. Careful manipulation and fabrication of the restoration is to be mastered by the technician to achieve the best possible results.

83. References Phillips science of dental materials Craig’s restorative dental materials - 13 th edition Dental clinics of North America Journal- Oct, 2020 Dental Clinics of North America Journal- Apr, 2013 Rinke S, Rödiger M, Ziebolz D, Schmidt AK. Fabrication of zirconia-reinforced lithium silicate ceramic restorations using a complete digital workflow. Case reports in dentistry. 2015 Sep;2015. Gracis S, Thompson VP, Ferencz JL, Silva NR, Bonfante EA. A new classification system for all-ceramic and ceramic-like restorative materials. International Journal of prosthodontics. 2015 May 1;28(3). Babu PJ, Alla RK, Alluri VR, Datla SR, Konakanchi A. Dental ceramics: part I–an overview of composition, structure and properties. Am J Mater Eng Technol. 2015;3(1):13-8.