Characteristics of Reversible Hydrocolloid Undergoes syneresis and imbibition like alginate.Uses special metal tray through which water circulates to cool & create gel.Gel is boiled to soften, then held in ready to use state at 150 degrees F, then put in 110 degree bath to temper for placement in syringe, tray, and use in the mouth.Hysteresis = Ability to be heated the gelled form to soften it and then cool it to create the gel form again.Hardening produces “brush-heap” intertwining of fibrils.Sol-Gel transformation (Sol = softened form and Gel = hardened form).
Potassium sulfate (an accelerator of the setting of gypsum) is added to counteract borax which is a retarder of gypsum setting. Not well suited for fixed prosthodontics. Undergoes distortion by syneresis (gives off water) and imbibition (imbibes or takes on water). Mixed with water to form a Sol and it hardens chemically to form a Gel. Nonaqueous elastomers Polysulfide Condensation reaction silicone Additional reaction silicone Polyether Alginate substitutes. Aqueous elastomers Irreversible hydrocolloid (alginate) Reversible hydrocolloid. Be made using a material that accurately records detail and maintains its dimensional stability for sufficient time to permit arrival at the dental laboratory so accurate fabrication procedures can be completed. Record unprepared teeth so their shape can be used to establish the morphology of the crown / prosthesis and their lingual & occlusal surfaces can be used to establish the proper occlusion. – With implants, record their position in the bone and relationship to teeth. Ideal Requirements of a Good Impression – Record all the prepared tooth surfaces and some of the unprepared tooth cervical to the finish line. 3Shape scanner was used to scan the cast Katana CAD/CAM system was used to design and mill the zirconia copings Fabrication Sequence Scan of cast Scan of wax pattern Milled green-state crown Fired zirconia crownSurface colors applied CAD/CAM Milled Zirconia Crown It is milled in an oversized form due to the shrinkage that will occur upon firing. Indirect Digital Scanning Wax Pattern Made on Cast The information can be recorded digitally Cerec Bluecam by Sirona. It can be made using a physical material or. It is used as a permanent record of the mouth and for the fabrication of a restoration or prosthesis. It is used to produce a positive replica of the oral structures recorded in the impression. 
It is a negative reproduction of the prepared teeth or implant(s), adjacent teeth, and surrounding soft tissues that provides the information required for fabrication of a crown or fixed prosthesis.No portion of this program of instruction may be reproduced, recorded or transferred by any means electronic, digital, photographic, mechanical etc., or by any information storage or retrieval system, without prior permission. Goodacre, DDS, MSD Professor of Restorative Dentistry Loma Linda University School of Dentistry This program of instruction is protected by copyright ©. Secondary impression materials in fixed prosthodontics Charles J.
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