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AN INSIGHT ON METAL FREE CERAMICS

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  1. www.rxdentistry.net

  2. AN INSIGHT ON METAL FREE CERAMICS www.rxdentistry.net

  3. METAL FREE CERAMICS www.rxdentistry.net

  4. CONTENTS • Introduction • Classification • Conventional powder slurry systems • Castable ceramics • Pressable ceramics • Infiltrable ceramics • Machinable ceramics • Recent advances • Conclusion • Bibliography www.rxdentistry.net

  5. INTRODUCTION The term ‘ceramics’ is derived from the greek word ‘keramos’ meaning burnt stuff. The first ceramics fabricated by man were ‘Earthenware’ pots used for domestic purposes. This material is opaque, relatively weak and porous . It consisted mainly of kaolin. The blending of this with other minerals such as silica and feldspar produce the translucency and extra strength required for dental restorations. This was given the name ‘porcelain’. www.rxdentistry.net

  6. Historically, strength concerns compromised some of the esthetics of the porcelain crowns. Because of the relatively low tensile strength and brittleness of the porcelain it has been generally fused to metal substrate to increase resistance to fracture. However this metal base can effect the esthetics of the porcelain by decreasing the light transmission through the porcelain and by creating metal ion discoloration, allergic reaction and sensitivity. These drawbacks together with the material and labour costs associated with metal substrate fabrication have promoted the development of new ceramic systems that do not require metal yet have the strength and precision fit. So with the increasing demand for esthetics, improvements in strength of ceramics and adhesives for bonding of ceramics, metal free ceramics have become an important part of contemporary dental practice. www.rxdentistry.net

  7. CLASSIFICATION • Conventional / powder slurry systems • Castable ceramics • Pressable ceramics • Infiltrated ceramics • Machinable ceramics www.rxdentistry.net

  8. Conventional / powder slurry systems • PORCELAIN JACKET CROWN • PJC with Aluminous core • Glass ceramics • Leucite reinforced porcelain (OPTEC HSP) • DUCERAM LFC www.rxdentistry.net

  9. PORCELAIN JACKET CROWN • Dr Charles Land introduced one of the first ceramic crowns in dentistry in 1903. • Used a platinum foil matrix and high fusing feldspathic porcelain. • Excellent esthetics but low flexural strength: half moon fracture. • Poor marginal adaptation. www.rxdentistry.net

  10. PLATINUM FOIL TECHNIQUE www.rxdentistry.net

  11. PJC with Aluminous core • Mc Lean and Hughes developed a PJC with an alumina reinforced core in 1965 which resulted in significant improvement in fracture resistance • It consisted of a glass matrix containing between 40-50 wt% of Al2O3. • Large sintering shrinkage (15-20%) and use of foil - excellent marginal adaptation difficult to achieve. • Inadequate translucency. • The principle indication: maxillary anterior crown restoration www.rxdentistry.net

  12. Glass ceramics • Glass-ceramics polycrystalline materials developed for application by casting procedures using the lost wax technique. • Glass ceramics partially crystallized glass crystalline and amorphous properties • Fabricated in the vitreous (Glass or non-crystalline/amorphous) state and converted to a ceramic (crystalline state) by controlled crystallization using nucleating agents during heat treatment. www.rxdentistry.net

  13. Leucite reinforced porcelain (OPTEC HSP) • Feldspathic porcelain higher leucite crystal content. • The leucite and glassy components are fused during the baking process…at 1020ºC. ADVANTAGES: 1. More esthetic due to a more translucent core. 2. Greater strength. 3. No special processing equipment required. DRAWBACKS: 1. Increased leucite content contributes to the relatively high in vitro wear of opposing teeth. 2. Potential marginal inaccuracy USES: Inlays,onlays,low stress crowns. www.rxdentistry.net

  14. DUCERAM LFC • In 1992 duceram lfc was marketed as an ultralow fusing ceramic with 3 unique features: 1. Hydrothermal glass:decrease in glass transition temp., increase in flexural strength and thermal expansion co efficient. 2. “Self healing”…forming a 1 micrometer thick hydrothermal layer. 3. Extremely small size of crystal particles…enhances opalescence of ceramics. USES: Inlays,veneers,full contour crowns. www.rxdentistry.net

  15. CASTABLE CERAMICS www.rxdentistry.net

  16. CASTABLE CERAMICS: • FLUOROMICAS eg: Dicor • APATITE GLASS CERAMICS eg: Cerapearl (bioceram) • OTHER GLASS CERAMICS … Lithia based … Calcium phosphate based www.rxdentistry.net

  17. DICOR Dicor, the first commercially available castable glass-ceramic material for dental use was developed by The Corning Glass Works and marketed by Dentsply International The term “DICOR” is a combination of the manufacturer’s names: Dentsply International & Corning glass. Dicor is a castable polycrystalline fluorine containing tetrasilicic mica glass-ceramic (55 vol%) material, initially cast as a glass by a lost-wax technique and subsequently heat - treated resulting in a controlled crystallization to produce a glass - ceramic material. www.rxdentistry.net

  18. ADVANTAGES • Excellent esthetics resulting from natural translucency, light absorption, light refraction and natural colour for the restoration.(Chameleon effect) •    Relatively high strength (reported flexural strength of 152 MPa), surface hardness (abrasion resistance) and occlusal wear similar to enamel. • Inherent resistance to bacterial plaque and biocompatible with surrounding tissues. •   Low thermal conductivity. •       Excellent marginal adaptation www.rxdentistry.net

  19. DISADVANTAGES •       Requires special and expensive equipments •   Laboratory studies for use as veneers and inlays, failure rates as high as 8% in the posterior region • Dicor must be shaded/ stained with low fusing feldspathic shading porcelain to achieve acceptable esthetics, however the entire stain/ colors maybe lost during occlusal adjustment (use of abrasives), during routine dental prophylaxis or through the use of acidulated fluoride gels. www.rxdentistry.net

  20. CASTABLE APATITE GLASS CERAMIC 1985 -Sumiya Hobo & Iwata …available as Cera Pearl. Chemistry:Apatite glass-ceramic melts (1460°C) and flows like molten glass and when cast (1510°C) it has an amorphous microstructure Desirable characteristics of Apatite Ceramics • Cerapearl is similar to natural enamel in composition, density, refractive index, coefficient of thermal expansion and hardness • Bonding to tooth structure www.rxdentistry.net

  21. Lithia Based Glass-Ceramic • Developed by Uryu • Commercially available as Olympus Castable Ceramic (OCC) • Composition: It contains crystals of LiO.AI2O3.4SiO2 after heat treatment. www.rxdentistry.net

  22. Calcium Phosphate Glass-Ceramic •   Given by Kihara and others, for fabrication of all-ceramic crowns by the lost wax technique. • It is a combination of calcium phosphate and phosphorus pentoxide plus trace elements. • The glass ceramic is cast at 1050°C which is converted to a crystalline ceramic by heat treating at 645°C for 12 hours. • Reported Flexural strength (116 Mpa); Hardness close to tooth structure. • Disadvantages •      Weaker than other castable ceramics • Opacity reduces the indication for use in anterior teeth. www.rxdentistry.net

  23. Advantages of castable glass ceramics • High strength because of controlled particle size reinforcement. • Excellent esthetics resulting from light transmission similar to that of natural teeth .and convenient procedures for imparting the required colour. •   Accurate form for occlusion, proximal contacts, and marginal adaptation. •     Uniformity and purity of the material. www.rxdentistry.net

  24. Favorable soft tissue response. •     X-ray density allowing examination by radiograph • Hardness and wear properties closely matched to those of natural enamel •     Similar thermal conductivity and thermal expansion to natural enamel • Dimensional stability regardless of any porcelain corrective procedure and subsequent firings www.rxdentistry.net

  25. PRESSABLE CERAMICS (Heat transfer molded or Injection molded) www.rxdentistry.net

  26. PRESSABLE CERAMICS 1.Shrink free ceramics: eg Cerestore Al-ceram 2.Leucite reinforced glass ceramics: eg IPS empress Optec/OPC 3.Lithia reinforced glass ceramic: eg IPS empress 2 OPC 3G www.rxdentistry.net

  27. CERESTORE This shrink-free ceramic material essentially consists of Al2O3 and MgO mixed with a Barium glass frits. On firing crystalline transformation produces Magnesium aluminate spinel, which occupies a greater volume than the original mixed oxides compensates for the conventional firing shrinkage. Advantages: • Good dimensional stability •    Better accuracy of fit and marginal integrity. •   Esthetics enhanced due to the lack of metal coping. • Biocompatible . •    Low thermal conductivity, Low coefficient of thermal expansion www.rxdentistry.net

  28. Disadvantages : • Complexity of the fabrication process. •      Need for specialized laboratory equipment • Inadequate flexural strength (89MPa) • Poor abrasion resistance, hence not recommended in patients with heavy bruxism or inadequate clearance. • Limitations and high clinical failure rates led to its withdrawal from the market. It underwent further improvement with a 70 to 90% higher flexural strength and was marketed under the commercial name Al Ceram www.rxdentistry.net

  29. AL CERAM • Recrystallization of residual glass – Fracture toughness 22.5 MN/m2 (32,000psi) • High polycrystalline content • Same relative thermal conductivity of core and veneer porcelain • Low coefficient of thermal expansion - Thermal shock resistance. • High modulus of elasticity - Low stress on cement. www.rxdentistry.net

  30. IPS EMPRESS • First described by Wohlwend & Scharer; • Is a precerammed glass ceramic having a high concentration of leucite crystals ie.35 vol%(KAlSi2O6). • It increases the resistance to crack propogation. • The manufacturer blends it with resin blocks,being thermoplastic allows the material to be injection molded. • Leucite-reinforced ceramic powder available in different shades is pressed into ingots and sintered. • The ingots are heated in the pressing furnace until molten and then injected into the investment mold. www.rxdentistry.net

  31. Properties : • Reported flexural strengths are in the range of 160 to I80MPa. • The increase in strength has been attributed to the pressing step which increases the density of leucite crystals.      • Subsequent heat treatments which initiate growth of additional leucite crystals. Uses : •     Laminate veneers and full crowns for anterior teeth •     Inlays, Onlays and partial coverage crowns •     Complete crowns on posterior teeth. www.rxdentistry.net

  32. ADVANTAGES •       Lack of metal or an opaque ceramic core •       Moderate flexural strength (120-180MPa range) •       Excellent fit (low-shrinkage ceramic) •    Improved esthetics (translucent, fluorescence) •     Etchable •     Less susceptible to fatigue and stress failure •     Less abrasive to opposing tooth •      Biocompatible material • Unlike previous glass-ceramic systems IPS Empress does not require ceramming to initiate the crystalline phase of leucite crystals (They are formed throughout the various temperature cycles). www.rxdentistry.net

  33. IPS EMPRESS 2 • Second generation of pressable materials for all-ceramic bridges. • Lithium disilicate framework with an apatite layered ceramic. • The glass-ceramic ingots are made from lithium silicate glass crystals with crystal content of more than 70 volume%. • The apatite crystals incorporated are responsible for the improved optical properties (translucency, light scattering) unique chameleon effect. • IPS Empress 2 is used with special investment material, an EP500 press furnace and a fully automatic high-tech furnace. www.rxdentistry.net

  34. ADVANTAGES •      High biocompatibility •      Excellent fracture resistance •      High radiopacity • Outstanding translucency. Uses :Anterior and posterior crown Premolar FPD. Other applications: Cosmopost and IPS Empress cosmoingot - core build-up system with the pre-fabricated zircon oxide root canal posts and the optimally coordinated ingot. www.rxdentistry.net

  35. INFILTRATED CERAMICS www.rxdentistry.net

  36. GLASS INFILTRATED CORE PORCELAINS 1. INCERAM ALUMINA 2. INCERAM SPINELL 3. INCERAM ZIRCONIA www.rxdentistry.net

  37. INCERAM • An improved high aluminous porcelain system termed In-Ceram was developed by a French scientist and dentist Dr. Michael Sadoun (1980) and first introduced in France in 1988. • Composition: • Alumina/ Al203 crystalline • An Infiltration glass lanthanum aluminosilicate with small amounts of sodium and calcium • Final ICA core contains 70 wt% alumina infiltrated with 30 wt% sodium lanthanum glass. www.rxdentistry.net

  38. Uses: •      Single anterior & posterior crowns • Anterior 3-unit FPD's www.rxdentistry.net

  39. Advantages : •     Minimal firing shrinkage, hence an accurate fit. •    High flexure strength (almost 3 times of ordinary porcelain) makes the material suitable even for multiple-unit bridges     • Aluminous core being opaque can be used to cover darkened teeth or post/ core. •   Wear of opposing teeth is lesser than with conventional porcelains. • Improved esthetics due to lack of metal as substructure. • Biocompatible, diminished plaque accumulation, biochemical stability. www.rxdentistry.net

  40. Disadvantages : • Requires specialized equipment • Poor optical properties. •    Incapability of being etched with HF acid. •   Slip casting is a complex technique and requires considerable practice. •     Requires considerable reduction of tooth surface all over for adequate thickness of restoration. www.rxdentistry.net

  41. In-Ceram Spinell • This is an offshoot of Inceram alumina. • Due to the comparatively high opacity of the alumina core,this material was introduced . • Incorporating magnesium aluminate (Mg A1204) results in improved optical properties characterized by increased translucency with about 25% reduction in flexural strength. • Spinel or Magnesium aluminate (Mg A12O4) is a composition containing Al2O3 and Mg2O (a natural oxide of Mg2+ AI3+). www.rxdentistry.net

  42. ADVANTAGE: • Increased translucency provides improved esthetics in clinical situations in which the adjacent teeth or restorations are quite translucent. DISADVANTAGES: • Lower strength and toughness. USES: • Anterior inlay, onlay ,veneers and anterior crowns. • Incapable to be etched by HF www.rxdentistry.net

  43. In-Ceram Zirconia • The In-Ceram technique was expanded to include its modified form with zirconia. • A mixture of zirconium oxide/ aluminium oxide is used as a framework material, the physical properties were improved without altering the proven working procedure. • The final core of ICZ consists of 30 wt% zirconia and 70 wt% alumina. www.rxdentistry.net

  44. ADVANTAGES: • The In-Ceram Zirconia material is said to feature a high flexural strength 700 MPa (2 to 3 times the impact capacity as the ln-Ceram Alumina), excellent marginal accuracy and bicompatibility. DISADVANTAGE: • Poor esthetics due to increased opacity. • Inability to etch. USES: • Posterior crowns and FPD’s. www.rxdentistry.net

  45. MACHINABLE CERAMICS www.rxdentistry.net

  46. Regardless of the advanced state of the 300-year old technique of casting, each of its steps could induce error in the final casting. • Until 1988, indirect ceramic dental restorations were fabricated by conventional methods (sintering, casting and pressing) and neither were pore-free. • Pore-free restorations can be alternately produced by machining blocks of pore-free industrial quality ceramic. • The tremendous advances in computers and robotics could also be applied to revolutionize dentistry and provide both precision and reduce time consumption. • With the combination of optoelectronics, computer techniques and sinter-technology, the morphologic shape of crowns can be sculpted in an automated way. www.rxdentistry.net

  47. CAD-CAM(DIGITAL) COPYING SYSTEMS (ANALOGOUS) MACHINING SYSTEM • INDIRECT • Automill • Denti CAD COPY MILLING EROSION 1.MANUAL 1.SONOEROSION eg:Celay eg:DFE Erosonic 2.AUTOMATIC 2.SPARK EROSION eg:Ceramatic eg:DFE Procera • DIRECT • Cerec 1 • Cerec 2 www.rxdentistry.net

  48. DIGITAL SYSTEMS CAD-CAM: • Uses digital information about the tooth preparation or a pattern of the restoration to provide a computer-aided design (CAD) on the video monitor for inspection and modification. • The image is the reference for designing a restoration on the video monitor. • Once the 3-D image for the restoration design is accepted, the computer translates the image into a set of instructions to guide a milling tool (computer-assisted manufacturing [CAM]) in cutting the restoration from a block of material. www.rxdentistry.net

  49. Stages of fabrication:All systems ideally involve 5 basic stages: 1.    Computerized surface digitization  2.    Computer - aided design  3.    Computer - assisted manufacturing  4.   Computer - aided esthetics  5.   Computer - aided finishing (The last two stages are more complex and are still being developed for including in commercial systems). www.rxdentistry.net

  50. CEREC SYSTEM The CEREC (Ceramic Reconstruction) was originally developed by Brains AG in Switzerland. Identified as CEREC CAD/CAM system, it was manufactured in West Germany Cerec System consists of : •   A 3-D video camera (scan head) •   An electronic image processor (video processor) with memory unit (contour memory) •    A digital processor (computer) connected to, •     A miniature milling machine (3-axis machine) www.rxdentistry.net