Ceramic
Word ceramic is derived from Greek word “Keramikos” meaning burn stuff, i.e., materials produced by burning or firingCeramic can be defined as a non metallic inorganic material usually processed by firing at a high temperature to achieve desirable properties. The more restrictive term porcelain refers to a specific composition rang of ceramic materials made by mixing kaolin, quartz, and feld spar, and firing at high temperature.Classification of Dental Ceramics
1. Fusion Temperature The high-fusing ceramics, a fusing range 1315o -1370oC The medium-fusing ceramics, 1090o -1260oC The low-fusing ceramics, 870o -1065oC The ultra low-fusing ceramics, <850oC The composition has three major ingredients: quartz (or flint), feldspar, and clay (or kaolin).Classification of Dental Ceramics
1. Fusion Temperature The high-fusing ceramics, a fusing range 1315o -1370oC The medium-fusing ceramics, 1090o -1260oC The low-fusing ceramics, 870o -1065oC The ultra low-fusing ceramics, <850oC The composition has three major ingredients: quartz (or flint), feldspar, and clay (or kaolin).2. Applications
3 major applications in dentistry: *ceramic for ceramic-metal crowns and fixed partial dentures. *all-ceramic crowns, inlays, onlays, and veneers, when esthetics is apriority. *ceramic denture teeth. 3.Fabrication Technique One of the most common fabrication techniques for dental ceramics is called sintering slip casting, heat-pressing, and machining.CERAMIC-METAL RESTORATIONS
1. Oxidation of the metal framework to improve bonding. 2. Opaque layer. 3. Two layers of ceramics are applied on opaque layer 4. Buildup of dentin & enamel ceramics to obtain an esthetic appearance similar to that of a natural tooth. The ceramic-metal crown is sintered in a porcelain furnace. The alloys used for casting the and Base Metal substructure are usually: Nobile metal gold-based containing tin and indium. Gold-palladium, silver-palladium, and Base Metal: Co-Cr, Ni-Cr-Be, cp-Ti were initially developed as lower cost alternative.ALL- CERAMIC RESTORATIONS
Criteria for selection and use of dental ceramics 1. Not used in patients with bruxism, malocclusion, clenching. 2. Experience of technician is important. 3. Judgment of esthetic requirements of the patients. 4. Used in patients exhibiting highest translucent anterior teeth. 5. Patient should accept risks of all-ceramic crowns. 6. Skill of dentist is produced preparation without a undercuts and smoothest preparation without excessive reduction of teeth.FIBRICATION OF ALL-CERAMIC RESTORATION
Several processing techniques are available: 1. Sintered all-ceramic materials: a) Alumina-Based Ceramic. Feldspathic Porcelain. B) Lucite-Reinforce2. Heat-Pressed All-Ceramic Materials a) Lucite-Base Ceramic Ceramic ingots are pressed between 1150o and 1180oC (under a pressure of 0.3-0.4 Mpa). This temperature is held for about 20 mints in a specially designed automatic press furnace. The flextural these ceramic (120 Mpa) is about double than that of feldspathic porcelains. b) Lithium Disilicate-Based Materials They are heat-pressed in the 890o to 920oC Using the same equipment as for the Leucite-based ceramics The main advantage is good flexural strength (350 MPa) and fracture toughness (3.2 MPa m). c) Lithium phosphate-Based Ceramic
3. SLIP-CAST ALL-CERAMIC MATERIALS a) Inceram Alumina-Based Materials b) Inceram Spines-and Zirconia-Based Materials 4. MACHINABLE ALL-CERAMIC MATERIALS Procera Allceram It is a densely sintered high purity aluminum oxide core material. The ceramic material composed 99.9% alumina and one of the hardest ceramic around. Procera scanner is used to scan the surface of prepared tooth and core is prepared by transmitting the data to milling unit using CAD-CAM technology (Computer Aided Design and Computer Aided Manufacturing process). After coping is made veneering of ceramic material over the coping is done by ceramist using advanced powder technology. Used for anterior crowns, posterior crowns, veneers, onlays, inlays.
Zirconia Ceramics
In 2002 zirconia based machinable ceramic was introduced. The materials consists of zirconia polycrystals stabilized by addition of 3Y-TZP (yittria stabilized tetragonal zirconia polycrysals ceramic). Partially sintered blocks are machined by CAD- CAM system and later sintered at 1350oC for 2 hrs. Highest flexural strength and fracture toughness of all available materials, e.g. CERCON, LavaZirconium Frame construction
All-ceramic zirconium based anterior bridgeTissue management
Zirconium Frame construction* Preparation Anterior and posterior region
10.7
0.6
1.5
1 0.8
1 0.8
1.5
1.5
1.5
1 1 0.8
0.8
* Preparation Inlay / Onlay
1.5
1.5
1.5
1.5
Provide a preparation depth of at least 1.5 mm in the fissure area (central fissure). Provide an isthmus width of at least 1.5 mm. Round out internal angles to enable an accurate fit of the inlay. Avoid preparation margins in occlusal contact areas. Provide 1.5 mm space in the area of the cusps. An onlay preparation is indicated if the preparation margins are no more than 0.5 mm away from the cusp tip or if the enamel is severely underminded.
* Final preparation
Preparation before impression takingafter soft tissue management
Examples of the Different Sizes of CordsCourtesy Ultradent Products, Inc.
Retraction Cords
Either nonimpregnated or impregnated Impregnated cords contain astringent-vasoconstrictor agents to control bleeding and shrink tissue The chemicals most often used are epinephrine, ferric sulfate, and aluminum chloride Epinephrine is usually impregnated into the cord Ferric sulfate and aluminum chloride are available in liquid or gel form They are dispensed into a dappen dish where the nonimpregnated cords are soaked before placemen Available in a syringe that is injected into the sulcusRetraction Cords
Placed in sulcus with use of cord-packing instrument Cord is gently pushed into sulcus without damaging periodontal tissues Best retraction is placement of one smaller cord toward periodontal attachment and then larger cord at opening of sulcusMechanical Retraction
Occasionally necessary when other methods fail Dentist uses mechanical retraction to force tissue away from tooth with use of temporary crown Temporary crown extends beyond gingival margin into sulcus Patient wears temporary crown for several days and returns for the impression Requires an extra appointment for patientSurgical Retraction
Removal of hypertrophied or excess tissue interfering with gingival margin Tissue is removed with an electrosurge, surgical knife, or laser Electrosurge is a device with a wand that holds a wire tip Current runs through the wand to the tip to cut and cauterize tissue* Preparation – Basic rules Preparation margins should be supragingival or level with the gingival margins (adhesive cementation technique) Strictly observe the necessary minimum wall thickness Complete the preparation with even reduction and maintain the anatomical contours Block out undercuts Avoid sharp edges and angles to prevent stress and to facilitate placement
The impression can be taken with an addition-reaction silicone (e.g. Virtual) or by utilizing another suitable impression material or preferred impression-taking technique.
Impression taking
Bite Registration
Necessary for laboratory to articulate or fit together models of prepared and adjacent teeth with opposing arch Form of impression material placed in between maxillary and mandibular arch DA instructs patient to close mouth into a natural bite position and allow material to setShade matching of dental restorations
The dentist will usually specify a shade or combination shades for different parts of the restoration, corresponding to a set of bottles in the lab containing the porcelain powder. A common shade system used is the Vita guide (Vita Classical and Vita 3D Master).Current methods of shade matching
-Clinical color match of porcelain visual shade- matching systems. -Shading of ceramic crowns using digital tooth shade matching devices.* Try-in of the inlay bridge
complete the try-in and occlusal check isolate the working field by means of a rubber dam conduct another try-in to ensure that the final restoration can be seated effortlessly* Adhesive cementation
Adhesive cementation of metal-free restorations. Such a bond enhances the fracture resistance of the restoration. The translucent shade of the adhesive promotes the aesthetic appearance of the restoration.* Conventional cementation
Conventional cementation of metal-supported restorations The inside of the metal framework needs to be sandblasted with type 100 Al2O3 (in the lab)*
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Before adhesive cementation, roughen contact surfaces using a finishing diamond Silanize surfaces (Monobond S) to enable a chemical bond Apply Variolink II Inlays/Onlays apply Variolink II to the preparation and, if necessary, on the fitting surface of the restoration Crowns and Bridges apply Variolink II on the fitting surface of the restoration and, if necessary, on the preparation Veneers apply Variolink II directly on the preparation and, if necessary, on the internal aspects of the restoration.
*
Apply Variolink II into the cavity
Place inlay-retained bridge in-situ* Polymerization
Cover restoration margins with glycerin gelPolymerize all sides for 40 sec each
* Finishing and polishingAfter cementation SR Adoro restorations can be polished to a high gloss using conventional polishing devices. The homogeneous material structure of SR Adoro promotes the enamel-like gloss.
Cleaning pastes used for professional tooth cleaning must not be used, as these pastes roughen the surface and cause loss of gloss.
* Clinical situation and final restoration
* Clinical situationsBeniamino Foresi, Italy