Tooth colored restorative materials

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Tooth Colored Restorative Materials describes in brief regarding the various materials used as cements and crown for loss of tooth structure either by caries or other factors like trauma, GERD, Abrasion etc

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  • Tooth colored restorative materials

    1. 1. Tooth Colored Restorative Materials Presented by:- Enosh Steward Nirmalkumar
    2. 2. Contents  Silicate cements  Acrylic resins  Glass ionomer cements  Resin based composite material  Ormocers  Silorane  Compomers  Giomers  Ceramics  Zirconia www.google.com
    3. 3. Ideal characteristics of restorative materials http://www.slideshare.net/hira_rahman/properties-of-dental-materials-lecture-two
    4. 4. Silicate cements  The use of dental cement as a restorative material began with silicate cement around the first half of the 20th century.  It is a fluoride-releasing cement based on silicate glass and phosphoric acid.  The silicate cements demonstrate anti-cariogenic potential because of the ability of Fluoride ions to inhibit demineralization.  Yet they are no longer used for permanent teeth because they become severely eroded within a few years due to marginal leakage Manappallil - Basic Dental Materials 3rd Edition
    5. 5. Acrylic resins  Acrylic resins replaced the silicates during the late 1940s and the early 1950s because of their tooth like appearance, insolubility in oral fluids, ease of manipulation, and low cost.  These acrylic resins too have relatively poor wear resistance and they shrink severely during curing, which causes them to pull away from the cavity walls and produce leakage along margins.  Their excessive thermal expansion and contraction cause further stresses to develop at the cavity margins when hot or cold beverages and foods are consumed. Manappallil - Basic Dental materials 3rd Edition
    6. 6. Glass ionomer cement  A glass ionomer cement (GIC) is a dental restorative material used in dentistry for dental fillings and luting cements. These materials are based on the reaction of silicate glass powder and polyalkenoic acid, an ionomer.  Developed in Britain, and firstly described by Alan Wilson and Brian Kent in 1972  Used for mostly Class V abrasion lesion/ Caries  Lack of aesthetic and translucency  Conserve tooth structure, assist in remineralization while maintaining appeal.  ƒƒFormed from the reaction of an ion--leachable calcium alumino-silicate glass powder and a poly-alkenoic acid.  “Glass polyalkenoate cements”  Types (1) Conventional (2) Resin Modified Manappallil - Basic Dental Materials 3rd Edition
    7. 7.  Wilson and Brian Kent established that the setting mechanism for these materials was an acid–base reaction between the glass powder and phosphoric acid, which formed a salt.  With this knowledge, they worked with Smith’s adhesive polyacid liquid and the more esthetic silicate powder to develop a glass-ionomer cement.  Hence, today’s glass-ionomer cements combine polyacrylic acid liquid with silicate cement powder, yielding a material that demonstrates the best properties of both. Components of Conventional Acid–Base Cements Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
    8. 8. Composition of glass ionomer cements Manappallil - Basic Dental Materials 3rd Edition
    9. 9.  In 1979 and 1980, there was a steady flow of new products, including Fuji Ionomer (GC International, Tokyo, Japan), Chemfil (Dentsply International Inc., Konstanz, Germany), and Ketac-fil (ESPE).  ESPE washed the glass powder with acid to remove calcium ions from the surface, thus delaying initial set and giving excellent working and setting characteristics.  ESPE was also the first company to use copolymers of acrylic and maleic acid, which is a stronger and more reactive acid, to accelerate setting. Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
    10. 10. GLASS-METAL IONOMER MIXTURES  In 1957, Massler published an article about using a restorative of amalgam powder mixed with zinc phosphate cement for pulp capping.  In 1962, Mahler and Armen showed that adding amalgam alloy to zinc phosphate cement improved the transverse strength, solubility, and disintegration of the resulting material compared with using zinc phosphate cement alone. Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
    11. 11.  In the early 1980s, prior to the introduction of radiopaque glass ionomers, lucent glass ionomer powders were mixed with amalgam powders to produce glass-metal ionomer mixtures that are radiopaque yet maintain many of the favorable properties of the glass ionomers.  These restoratives are called admixtures. And, some clinicians call this combination “miracle mix” and have made metal-ionomer mixtures popular as core buildups, bases, retrofills, endodontic sealers, and crown repairs. Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
    12. 12.  The major material disadvantage of the glassmetal ionomer mixture is the difficulty of achieving a homogeneous mix of silver and glass throughout the restorative.  In addition, the metal particles are not well bonded to the set material, which results in erosion and increased wear as the poorly attached metal particles are plucked from the surface.  Clinical problems also result from moisture contamination during setting. Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
    13. 13. Google images
    14. 14. CERAMIC-METAL GLASS IONOMERS  In 1987, the first cermet (ceramic + metal) glass ionomer, Ketac-Silver® (ESPE), was introduced.  ESPE researchers McLean and Gasser developed these ionomers filled with sintered metal and glass compositions.  Their intention was to improve the bond between the metal filler and the glass cement powder and produce a material with better wear properties.  Using a silver-impregnated coating around the aluminosilicate glass powder lowered the coefficient of friction, thereby significantly improving abrasion resistance. Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
    15. 15.  Cermet ionomers are prepared by sintering (at 800°C) compressed pellets made from a mixture of fine metal powders and ion-leachable glass fillers.  The bond between these metals and glass particles results in a seal that is similar to that of a porcelainfused-to-metal restoration.  The resulting metalfused- to-glass filler particles can be reacted with polyacid copolymers to form an ionomer restorative.  The most suitable metals for these cermet ionomers are gold and silver. Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
    16. 16. RESIN-MODIFIED GLASS IONOMERS  Resin-modified glass-ionomer materials attempt to combine the best properties of composite resins and glass ionomers.  They have some cariostatic properties, a low thermal expansion, and the hydrophilic qualities of the glass- ionomer cements.  The polymerizing resin matrix of resin-modified glass ionomers improves the fracture toughness, wear resistance, and polish of these materials compared with conventional glass ionomers. Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
    17. 17.  Antonucci and co-workers introduced the lightcured glass-ionomer cements in 1988. Vitrebond, the first commercially viable cement of this type, was developed by Mitra in 1989.  These early modified resin ionomers had two setting mechanisms: a lightintiated polymerization reaction and a glass ionomer acid–base reaction.  In 1992, Mitra added the first autocured resin capabilities to resin-modified glass-ionomer cements. Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
    18. 18.  These cements contained additional chemical initiators to allow the resin to polymerize without light.  These materials are available in auto- and dual-cure forms.  The dual-cured materials have three setting reactions:  Photocure,  Autocure, and  Acid–base reaction between the glass-ionomer powder and the polyacid. Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
    19. 19.  Regardless of their curing mechanism, the resinmodified glass-ionomer cements develop strength more rapidly because of the resin polymerization component of their setting reaction.  One problem with these materials is that the modified poly-acrylic acid is less soluble in water  Therefore, Hydroxyethyl methacrylate must be added as a co-solvent to avoid phase separation of the resin from the glass ionomer components Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
    20. 20. Google images
    21. 21. Classification by use There can be eight classes formed  1. Glass-ionomer luting cements used as luting agents. They are autocured.  2. Glass-ionomer restoratives used as restorative materials. The major difference between luting and restorative glass ionomers is that the restorative is available in more shades, has a higher filler load, and has a much higher film thickness. They are autocured.  3. Glass-metal ionomer mixtures are intended for bases and buildups. These are sometimes called admixtures. They are autocured. Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
    22. 22.  4. Cermet-ionomers are ionomers containing metal-fused-to-glass particles. Neither the glassmetal nor the cermet-ionomers are tooth-colored. They are autocured.  5. Glass-ionomer liners are rapid-setting radiopaque materials for dentin liners under composites and amalgams. They are light- cured.  6. Glass-ionomer bases intended as bases under other restoratives.  7. Glass-ionomer sealants for sealing pits and fissures. They are autocured.  8. Resin-modified glass ionomers include light- and dual-cured glass ionomers. Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
    23. 23. Advantages of glass ionomers  Form a rigid substance on setting  Good fluoride release (bacteriostatic, inhibit caries)  Low exothermic reaction on setting  Less shrinkage than polymerizing resins  Coefficient of thermal expansion similar to dentin  No free monomers  Dimensional stability at high humidity  Filler–matrix chemical bonding  Resistant to micro-leakage  Non-irritating to pulp  Good marginal integrity  Adhere chemically to enamel and dentin in the presence of moisture  Rechargeable fluoride component  Good bonding to enamel and dentin  High compressive strength Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
    24. 24. Disadvantages • Susceptible to dehydration over lifetime • Sensitivity to moisture at placement • Poor abrasion resistance • Average esthetics • Less tensile strength than composites • Technique sensitive powder-to-liquid ratio and mixing • Less color-stable than resins • Contraindicated for Class IV or other stressbearing restorations • Poor acid resistance Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
    25. 25. Bar graph illustrating the difference in simulated occlusal wear between amalgam, a composite, a resinmodified glass-ionomer cement, a glass-ionomer cement,and a silver cermet. Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
    26. 26. Average tensile strengths of crown buildup materials. Harry F. Albers. Tooth-colored restoratives principles and techniques. Ninth edition
    27. 27. Resin-based Composite Material  Dental composites, also called "white fillings", are a group of restorative materials used in dentistry.  Composite typically consists of a resin-based matrix, such as a bisphenol A-glycidyl methacrylate (BISGMA) resin like urethane dimethacrylate (UDMA), and an inorganic filler such as silica.  Compositions vary widely, with proprietary mixes of resins forming the matrix, as well as engineered filler glasses and glass ceramics.  The filler gives the composite wear resistance and translucency.  A coupling agent such as silane is used to enhance the bond between these two components.  An initiator package begins the polymerization reaction of the resins when external energy (light/heat, etc.) is applied. Wikipedia
    28. 28. Google images
    29. 29. Composition of Composite Resin  Enamel and dentin are good examples of natural composite materials as both consist of organic and inorganic materials, predominately hydroxyapatite crystals.  Enamel consists of 5% organic and 95% inorganic materials, while dentine consists of 25% organic and water and 75% inorganic material.  Like enamel and dentine, resin composite is mainly composed of an organic phase (resin matrix) and an inorganic or dispersed phase (filler particles).  In addition, resin composite also contains and another component which is a coupling agent (interfacial phase). (Feilzer and Dauvillier, 2003; Gonçalves et al., 2010; Gonçalves et al., 2011).
    30. 30. Resin matrix:  The resin matrix is a synthetic monomer that forms a cross-linked structure after polymerisation.  Monomers originally used in resin composites were methylmethacrylate [MMA].  The MMA was replaced by an aromatic dimethacrylate oligomer and the reaction product of Bisphenol-A and glycidyl methacrylate [Bis-GMA] (2,2-bis[4-(2-hydroxy-3- methacryloxypropoxy) phenyl] propane) was developed by Bowen in 1962 hence it is called Bowen’s resin, and still the most often used resin in many resin composites (Feilzer and Dauvillier, 2003; Gonçalves et al., 2010; Gonçalves et al., 2011).
    31. 31.  BisGMA is a highly viscous monomer with a high molecular weight, the difference in size of MMA and BisGMA monomers is significant.  This difference gives BisGMA the benefit of producing a material that has better mechanical properties and much less polymerisation shrinkage than materials in which small monomers such as MMA are used: 7.5 vol% compared to 22 vol%. (Feilzer and Dauvillier, 2003; Gonçalves et al., 2010; Gonçalves et al., 2011).
    32. 32.  The major problem with BisGMA is that the monomer is highly viscous and this makes the material difficult to handle.  This viscosity is due to the presence of two hydroxyl groups. In order to achieve adequate handling properties and adequate degree of conversion, BisGMA is diluted with monomers of lower molecular mass such as triethyleneglycol dimethacrylate [TEGDMA].  This dilution has the undesirable effect of increasing polymerisation shrinkage. A way to overcome the problem is by substituting the hydroxyl (-OH) groups with an ethoxy species (- CH2-CH2-O) to give an ethoxylated BisGMA. (Feilzer and Dauvillier, 2003; Gonçalves et al., 2010; Gonçalves et al., 2011).
    33. 33.  Many resin composites now contain urethane dimethacrylate (1,6- bis(methacryloyloxy-2-ethoxycarbonylamino)-2,4,4- trimethylhexan) [UDMA] either alone or in combination with other monomers.  This UDMA has the same molecular mass as BisGMA but it is less viscous, this property of UDMA makes it superior to a BisGMA and TEGDMA mixture because of a higher degree of conversion and lower polymerisation shrinkage (Peutzfeldt, 1997; Gonçalves et al., 2010).
    34. 34. Fillers  Filler particles are the dispersed phase of resin composite materials and can be defined as “the inorganic and/or organic resin particles that are designated to strengthen a composite, decrease thermal expansion, minimise polymerisation shrinkage, and reduce the amount of swelling caused by water sorption” (Anusavice and Phillips, 2003).
    35. 35.  Fillers positively influence many properties.  Such as increasing radiopacity , this radiopacity can be similar to that of enamel and thus distinguish it from any marginal gap or voids minimising polymerisation shrinkage, reinforce and increase the strength and reducing dimensional changes Alvarez-Gayosso et al., 2004; Gonçalves et al., 2011; Skovgaard et al., 2011
    36. 36.  Composites can be classified according to :-  Types of fillers (quartz, silica, etc)  Size of fillers (Macrofilled, microfilled, nano, hybrid)  Method of curing 1) Chemical activation (Use almost obsolete) 2) Light Activation Ramya Raghu
    37. 37. http://www.slideshare.net/biancawilda/composite-resin
    38. 38. Anusavice Phillips 11th Edition
    39. 39. Macro-filled resin composites  The original resin composites, often termed traditional or conventional, consisted of macro-filler particles. These were ground, crushed or milled, splinter shaped glass or quartz particles ranging from 1–100μm (later 5 – 30μm), typically the size of a human hair thickness (about 50μm)  Adding large particles improved physical properties like compressive strength  But there were several disadvantages: a reduced surface area to volume ratio meant there was a small interface between the two phases, reducing the bond between filler and matrix (Ferracane and Greener, 1984). (Venhoven et al., 1996)
    40. 40.  The difference in hardness between the phases meant that large particles eventually broke away leaving relatively deep holes and leading to inevitable failure of the filling due to poor wear resistance of the material.  The consequent surface roughness would leave the filling prone to staining and plaque accumulation over time. (Lutz and Phillips, 1983).
    41. 41.  Also, these materials were difficult to polish since the particles were larger than the wavelength of visible light.  Later use of smaller, rounder and softer filler improved polishability, but these materials continued to exhibit poor wear resistance because particles were still dislodged under masticatory force  Used for Class II and IV restorations mostly. (Lutz and Phillips, 1983).
    42. 42. Micro-filled resin composites  This type of composite has two subtypes, homogenous and heterogeneous.  In homogenous micro-filled resin composites all the filler particles are smaller than the wavelength of visible light (less than 0.04 μm) so the material is highly polishable and since there are no particles to be dislodged this lustre is maintained over time.  Using only micro-filler particles meant an increased surface area to volume ratio. (Jorgensen and Asmussen, 1978; Braem et al., 1989; Bayne et al., 1992; Venhoven et al., 1996).
    43. 43.  Decreasing the filler load has a deleterious effect on the physical properties of these materials and to overcome this problem, a solution is found by combining micro-filler particles with larger particles produced from prepolymerised pyrogenic silica in resin matrix to produce what is called heterogeneous microfilled composites.  Thus, allowing increased filler loading without increasing viscosity and jeopardizing handling characteristics.  Used mostly for class III and V carious lesions (Jorgensen and Asmussen, 1978; Braem et al., 1989; Bayne et al., 1992; Venhoven et al., 1996).
    44. 44. Hybrid resin composites  Most currently available commercial resin composites are hybrid composites.  Hybrid composites contain more than one size of filler particle in order to maximise filler loading and result in better mechanical properties.  Macro-filler particles are interspersed with smaller silica micro-filler particles.  These glass spheres are of the magnitude of 0.04μm (later 0.05 – 0.1μm). (Jorgensen and Asmussen, 1978; Braem et al., 1989; Bayne et al., 1992; Venhoven et al., 1996).
    45. 45.  Due to the varying size, the percentage of volume of filler could be increased which imparted increased stiffness, hardness, compressive strength and wear resistance  Presumably by increasing the particle surface area to volume ratio and reducing the area of unfilled resin exposed to food bolus fibres during mastication.  Indicated for class I II III IV and V carious lesions (Jorgensen and Asmussen, 1978; Braem et al., 1989; Bayne et al., 1992; Venhoven et al., 1996).
    46. 46. Nano-resin composites  More recently, developments in nanotechnology have produced potentially clinically superior resin composites for use in both aesthetic and load-bearing situations.  Nanotechnology permits the uses of nanoscale (1- 100nm) level of filler size. Thus microfilled composite could have been called nanofilled composite, but they were not due to lack of detection of nanotechnology at that period.  Nanometre-sized filler particles and larger groups of fused nano-particles (nano-clusters) are dispersed in a resin matrix to produce a nanocomposite. (Sharma et al., 2010). (Ferracane, 2011).
    47. 47.  Combining individual particles and clusters allows for increased filler loading without increased viscosity imparting improved physical properties and good handling characteristics.  The material is highly polishable and since nano-clusters will breakdown under force as opposed to becoming dislodged (Sharma et al., 2010). (Ferracane, 2011).
    48. 48. http://www.slideshare.net/biancawilda/composite-resin
    49. 49. http://www.slideshare.net/biancawilda/composite-resin
    50. 50. http://www.slideshare.net/biancawilda/composite-resin
    51. 51. http://www.slideshare.net/biancawilda/composite-resin
    52. 52. Coupling agent  A coupling agent is an agent applied to filler particles to ensure chemical bonding to the resin matrix.  This bond is essential to strengthen resin composite and distribute the force generated under function between the two pastes.  The most commonly used coupling agents are organosilanes, which are bipolar molecules, in particular γ-methacryloxypropyl trimethoxysilane.  The chemical bonding of fillers and resin matrix improves mechanical properties of resin composite materials and makes them stronger than materials with non silanated fillers Raghuramya
    53. 53. http://www.slideshare.net/biancawilda/composite-resin
    54. 54.  In addition, to the three main components resin composite there are some other components which are:  Activator-initiator system  Inhibitors  Optical modifiers Manappallil - Basice Dental Materials 3rd Edition
    55. 55. http://www.slideshare.net/biancawilda/composite-resin
    56. 56. http://www.slideshare.net/biancawilda/composite-resin
    57. 57. http://www.slideshare.net/biancawilda/composite-resin
    58. 58. http://www.slideshare.net/biancawilda/composite-resin
    59. 59. http://www.slideshare.net/biancawilda/composite-resin
    60. 60. Inhibitors  Added to prevent spontaneous polymerization of the monomers by inhibiting the free radical  Butylated hydroxyl toluene 0.01% is added as inhibitor in composite resins Raghuramya - Clinical operative dentistry 4th edition
    61. 61. Organically Modified Ceramics (Ormocers) Restorative Materials  Organically Modified Ceramic [Ormocers] is a hybrid material which is made by special processing based on nanoscale technology, mixing organic and inorganic components at a nanoscopic scale rather than by conventional means of physical mixing of different component of a matrix.  Ormocers have been developed as an alternative to the dimethacrylate based composites  The chemical structure of Ormocers is based on organically modified alkoxides and functionalised organic oligomers/polymers Moszner and Salz, 2001
    62. 62.  The organic constituent of Ormocers is used for cross linking the network whilst the inorganic component improves mechanical properties and other properties such as thermal and chemical stability.  Another advantage of these materials is that the large size of the monomer molecule minimises polymerisation shrinkage. Rosin et al 2002; Kournetas et al., 2004 and wear (Lutz and Krejci, 2000; Manhart et al. 2002)
    63. 63.  In a recent study, Ormocer-based material demonstrated the lowest decrease in hardness following immersion in solvent for a period of time compared with dimethacrylate-based composites and as a result it has been proved to be more resistant to solvent degradation than any other material tested (Cavalcante et al., 2011).
    64. 64. google images
    65. 65. Silorane Restorative Materials  The name silorane is derived from the combination of its chemical building blocks siloxanes and oxiranes  The siloxane block acts like a backbone for the silorane structure and also it improves the physical properties of composite by providing hydrophobicity to the silorane thus reducing the water sorption.  Moreover this hydrophobic nature tends to absorb less stain from a normal daily diet. Weinmann et al., 2005
    66. 66.  Silorane based materials have lower polymerisation shrinkage, but an overall mixed mechanical and higher flexural strength and fracture toughness than methacrylatebased restorative materials (Lien and Vandewalle, 2010).  A recent study has shown that silorane based materials exhibited higher colour change and surface degradation (Pires-de-Souza et al., 2011). Weinmann et al., 2005
    67. 67. Composition Filtek Silorane Posterior Restorative:  • Silorane resin  • Initiating system: camphorquinone, iodonium salt, electron donor  • Quartz filler  • Yttrium fluoride  • Stabilizers  • Pigments Braem M. J., Davidson C. J., Lambrechts P., Vanherle G. (1994), In vitro flexural fatigue
    68. 68. Silorane System Adhesive Self-Etch Primer:  • Phosphorylated methacrylates  • Vitrebond™ copolymer  • BisGMA  • HEMA  • Water  • Ethanol  • Silane-treated silica filler  • Initiators  • Stabilizers Braem M. J., Davidson C. J., Lambrechts P., Vanherle G. (1994), In vitro flexural fatigue
    69. 69.  Silorane System Adhesive Bond:  • Hydrophobic dimethacrylate  • Phosphorylated methacrylates  • TEGDMA  • Silane-treated silica filler  • Initiators  • Stabilizers  Available in A2 , A3 , B2 , C2 Braem M. J., Davidson C. J., Lambrechts P., Vanherle G. (1994), In vitro flexural fatigue
    70. 70. Compomers  A type of translucent hybrid dental resin which has the ben efits of composites and of glass ionomers which are used fo restorations of molars and cosmetic procedures  Introduced in 1990s  Compomer is a polyacid-modified composite resin.  Compomer is made predominantly from resin composite (90%) with the addition of a polyacid-modified molecule similar to that found in traditional GIC.  Compomers are initially light-cured, but subsequently absorb water, allowing for an acid-based reaction to set the polyacid-modified molecule.  They have normal adhesion to tooth structure and are always attached with resin dentin bonding agents Wikipedia ,Harry F. Albers
    71. 71.  Consequently, the material shrinks, initially due to polymerization contraction, and expands subsequently as water is absorbed.  The addition of a polyacid-modified molecule makes the material more hydrophilic.  Compomers are, therefore, relatively easy to handle and apt for preparation.  A dentin-bonding agent is required for their successful placement. Harry F. Alber
    72. 72.  Physically, their properties are similar to those of a composite.  The wear rates and fracture resistance are less than for a composite.  Compomers and composites have the same advantages .  Additional advantages of compomers include fluoride release and ease of handling. Harry F. Alber
    73. 73. Google images
    74. 74. Giomers  The material unites the chemistries of composite and GIC in an effort to combine the advantages of both materials, whilst minimizing the limitations of each.  Giomers are newly introduced hybrid aesthetic restorative materials for dental restorative therapy.  They are based on pre-reached glass-ionomer (PRG) technology.  Chemically, they consist of fluoroalumino silicate glass reacted with polyalkenoic acid in water prior to inclusion into the silica-filled urethane resin.  Giomers contain both of the essential components of glass-ionomer cements and resins but they cannot be classified as compomers, in which a variable amount of dehydrated polyalkeonic acid is incorporated in the resin matrix and the acid does not react with the glass until water uptake occurs. Journal of conservative dentistry, year 2002 Vol 5 issue 4
    75. 75.  Giomers can be subdivided into two distinct groups of materials, namely those in which the glass ionomer particles have been surface reacted and those which have been fully reacted.  Surface pre-reacted glass ionomer giomers are suitable for composite indications  Fully pre-reacted glass ionomer giomers are used in dentin adhesive systems, fissure sealants, and as restorative material for nonloaded-bearing areas Journal of conservative dentistry, year 2002 Vol 5 issue 4
    76. 76. Google Images
    77. 77. Ceramics  Ceramics derived from greek word keramos.  Dental ceramics are chemical mixtures of nonmetallic and metallic elements that allow ionic and covalent bonding to form periodic crystalline structures.  The most common dental ceramics are composed of metal oxides (SiO2, AL2O3, K2O) and other traditional ceramic materials.  They are semicrystalline, sillicates, oxides and derivative structures.  Simple structures are bonded ionically and complex involve ionic and covalent bonding. wikipedia
    78. 78.  When preparing inlay or onlay it is mandatory to adhere to the requirement profile of the ceramic material.  The adhesive technique box preparations used to achieve mechanical retention are not required and will also lead to unfavourable ceramic designs.  Observing the defined minimum layer thickness is essential.  To ensure increased resistance of material, shaping of deep fissures can be omitted.  Ceramics can be classified by their microstructure (i.e., amount and type of crystalline phase and glass composition).[6]  They can also be classified by the processing technique (power-liquid, pressed, or machined) wikipedia
    79. 79. google images
    80. 80. Zirconia  Zirconia is a very hard ceramic that is used as a strong base material in some full ceramic restorations. The zirconia used in dentistry is zirconium oxide which has been stabilized with the addition of yttrium oxide.  The full name of zirconia used in dentistry is yttria- stabilized zirconia or YSZ.  The zirconia substructure (core) is usually designed on a digital representation of the patients mouth, which is captured with a 3d digital scan of the patient, impression, or model.  The core is then milled from a block of zirconia in a soft pre-sintered state. Once milled, the zirconia is sintered in a furnace where it shrinks by 20% and reaches its full strength of approximately 850MPa. Wikipedia
    81. 81.  The zirconia core structure can be layered with aesthetic feldspathic porcelain to create the final color and shape of the tooth.  Because bond strength of layered porcelain fused to zirconia is not strong, "monolithic" zirconia crowns are often made entirely of the zirconia ceramic with no aesthetic porcelain layered on top.  Zirconia is the hardest known ceramic in industry and the strongest material used in dentistry. Monolithic zirconia crowns tend to be dense in appearance with a high value and they lack translucency and fluorescence. Wikipedia
    82. 82.  For aesthetic reasons, many dentists will not use monolithic crowns on anterior (front) teeth  By using crowns made of metal zirconia, then merge the porcelain on the outside, zirconia crowns allow light to pass as a normal tooth would and that gives a natural look, unlike other metal cores that block the light.  The normal too hot/cold sensations that can be felt with other crowns does not normally occur because of reduced thermal conductivity, this being another strong point for zirconia. : "Where and When Is It Appropriate to Place Monolithic vs. Layered Restorations," Inside Dentistry, August 2012, Vol. 8, Issue 8, E. McLaren, R. Margeas, N. Fahl.
    83. 83. Google images
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