Ceramics II.-oxidceramics Dental CAD/CAM systems. Dr. Judit Borbely 2015

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1 Ceramics II.-oxid Dental CAD/CAM systems Dr. Judit Borbely 2015

2 All ceramic systems? Esthetics Biocompability No corrosion No allergy Optical properties (metal free restorations can reproduce natural aesthetics ) Driving force for developments has been the immense difference in reliability between metal-ceramic systems and all-ceramic systems and a public perception that metal-free restorations are more aesthetic

3 driving forces for developments: Public perception that metal-free restorations are more aesthetic Disadvantages of the metal ceramic systems include radiopacity, some questions centring around metal biocompatibility and lack of natural aesthetics Difference in reliability between metal-ceramic systems and all-ceramic systems

4 advances in industrial have included improvements: fracture toughness, wear resistance, machinability, solubility, hardness and flexural strength

5 Oxid

6 Silicate -Esthetics/Oxid-Strength Feldspar Silicate Glass Hydrothermal Feldspathic porcelain Dicor Duceram LFC Synthetic Veneering sintering CAD/CAM IPS Empress casting pressing CAD/CAM Duceram MK Oxid Glassinfiltrated In-Ceram Alumina In-Ceram Spinell In-Ceram Zirconia glass infiltration method CAD/CAM Polycrystalline Aluminiumoxide Zirconiumdioxide CAD/CAM

7 Oxide Polycrystalline materials: crystal phase > glassy matrix Greater flexural strength and Fracture tougness High functional strength thanks to excellent physical properties Very low transparency Images from KaVo Everest CAD/CAM system

8 Types of Oxide : Glass infiltrated o In-ceram Alumina o In-Ceram Spinell o In Ceram Zirconia Lab technology: Glass infiltration/cad CAM Polycrystalline o Aluminium-oxide o Zirconium-dioxide ceramic Lab technology: CAD/CAM

9 Glass infiltrated oxide 1989 In-Ceram technique: oxid for crown and bridge substructures The cast alumina sintered and then infiltrated with a Lanthana based glass. glass infiltrated alumina core on which a feldspathic ceramic baked to provide the functional form and aesthetic component of the restoration In-Ceram use variations of alumina as a toughened and high strength underlying core to support feldspathic veneering porcelain which gives the final shape and aesthetic attributes required for the restoration.

10 In-Ceram Alumina: anterior and posterior crown substructures and three unit anterior bridges Alumina is made of synthetically manufactured corundum which is extracted from bauxite In-Ceram Zirconia aluminium oxide is reinforced with zirconium oxide and combines the fracture toughness of ZrO2 with the high flexure strength of AlO In-Ceram Spinell aluminium oxide is reinforced with MgAl2O4 and offers anterior aesthetics: natural, translucent appearance, used for anterior crowns Corundum=Aluminium oxide (Al2O3) Spinell Zirconia

11 CAD/CAM In-Ceram technique aluminium oxide substructure is milled from industrially manufactured, porously presintered ceramic blanks The porosities are then sealed with glass infiltration Veneering with a thermal expansion coefficient matched to that of the substructure material Vita In-Ceram ceramic blanks and milled substructure

12 Polycrystalline oxide Aluminium-oxide Aluminium-oxide content >73% Zirconium-dioxide ZrO2 95%+ 5% Yttrium Tetragonal Zirconium Polycrystals (TZP) Phase transformation toughening : 5% Yttrium-oxide in addition, partially stabilised ZrO2

13 Ceramic steel ZrO2 exists in 3 forms (monoclinic, orthorhombic and tetragonal), each with a different crystal structure ZrO2 can be stabilized in its tetragonal hightemperature phase by addition of yttrium oxide When applying an external source of energy (for example in the case of a beginning crack) individual zirconium oxide grains are transformed locally and accompanied by an increase in volume to their stable mnoclonic form at room temperature= transformation strengthening Compressive stresses arising within the structure to prevent the growth of crack This phenomenon=tension expansion is only known in the case of steel

14 Application of science to dentistry Zirconium-dioxide can not be formed by conventional lab technologies( sintering, pressing, casting). CAD/CAM made it possible to work with a new generation of hard in dentistry. These materials cannot be cast so therefore must be machined. In order to machine something a cutting path is required. The cutting path is generated from digital scanned data. SCAN THE OBJECT CREATE DIGITAL DATA POINTS GENERATE CUTTING PATH MACHINE REPLICA OBJECT

15 CAD/CAM systems mills the contour from: Dense sintered ceramic blank or Presintered, porous ceramic blank-final sintering required for improving mechanical properties. Structure of porous ZrO2 before final sintering (A) densely sintered ZrO2 (B), Scanning elelectron microscop, magnification: X

16 Green processing Milling of presintered ceramic blocks advantage: easy to process, grinding instruments do not have to be replaced that often disadvantage: porous presintered zirconia shape shrinks during final sintering- enlarged substructures= software calculated Hard processing Milling of dense sintered ceramic blocks Takes more time, grinding instruments wear off HIP= Hot Isostatic Press : special sintering technique High temperature and pressure applied to densify the material, gaining 20% more in strength

17 Thank You for Your Attention!