Sequences of operations Fixed dentures: Full crown Made of metal alloy (gold or chromcobalt) 1. Phase in dental office Preparation Reduction 0,5 mm around, occlusaly 1 mm Preparation border – shoulderless or very slight round shoulder, located subgingivally 0,5 mm. Taking impression Elastomeric impression materials Polysulfid, silicon, elastomers.: Before the impression the retraction cord is applied around the tooth – subgingivally in order to open gingival sulcus and take an exact impression of this area. Dual viscosity technique. a) Dual viscosity technique – double impression or b) Simultaneous dual viscosity technique. Antagonal impression of alginate Occlusal registration (wax) 1. Phase in dental lab. Making the cast (model) of gypsum (pouring the impression). There are three types of base raw materials derived from partial dehydratation of gypsum rock: Plasters – fluffy, porous, least dense. Hydrocal – hihger density, more crystalline Densite – densest of the raw material. Plasters----- model plaster, lab plaster Hydrocal----dental stone Densite ------high strength dental stone High strength dental stone is used for fixed dentures. Wax pattern Lost wax method. – investment and casting, finishing. 2. Phase in dental office Try of the crown and its cementation. Metal ceramic crown Made of metal alloy ( usu chromcobalt) and ceramics which covers completely the metal framework These crowns are fully covered with ceramic material. 1. Phase in dental office Preparation Reduction 1 mm around, occlusaly 1, 5 mm. Preparation border - rounded shoulder located subgingivally 0,5 mm. Taking impression Elastomeric impression materials Polysulfid, silicon, elastomers.: Before the impression the retraction cord is applied around the tooth – subgingivally in order to open gingival sulcus - an exact impression of this area is necessary. Dual viscosity technique. a) Dual viscosity technique – double impression or – two phases b) Dual viscosity technique – one phase Antagonal impression of alginate Occlusal registration (wax) 1. Phase in dental lab. Making the cast (model) of gypsum (pouring the impression). There are three types of base raw materials derived from partial dehydratation of gypsum rock: Plasters – fluffy, porous, least dense. Hydrocal – hihger density, more crystalline Densite – densest of the raw material. Plasters----- Model plaster, lab plaster Hydrocal----dental stone Densite ------High strength dental stone On the model the technician makes wax pattern of the metal framework of the metalceramic crown. The wax is changed with the metal alloy used the lost wax method. – investment and casting, After casting follows the finishing of the framework 2. Phase in dental office Trying of the metal framework and choice of colour 2. Phase in dental lab Making of the ceramic coat (fully covered crown) special procedure – firing in a special oven in several phases. 3. Phase in dental office Trying of the crown and cementation Facette crown This crown is made of the metal alloy (golden or chromcobalt), partially covered with composite or methylmethacrylic resin. Resin covers the metal framework on the vestibular side. 1. Phase in dental office Preparation – Reduction 1 mm vestibulary, orally 0,5 mm, occlusally 1 mm Preparation border: rounded shoulder located 0,5 subgingivally Taking impression Elastomeric impression materials Polysulfid, silicon, elastomers.: Retraction cord around the tooth Dual viscosity technique. a) Dual viscosity technique – double impression or – two phases b) Dual viscosity technique – one phase Antagonal impression Alginate Occlusal registration (wax, elastomeric materials) 2. Phase in dental lab. Making the cast (model) of gypsum. There are three types of base raw materials derived from partial dehydratation of gypsum rock depending on on the nature: Plasters – fluffy, porous, least dense. Hydrocal – hihger density, more crystalline Densite – densest of the raw material. Plasters----- Model plaster, lab plaster Hydrocal----dental stone Densite ------High strength dental stone On the model the technician makes Wax pattern Lost wax method. – investment and casting, finishing of the framework 3. Phase in dental office Trying of the metalframework and choice of the colour 3. Phase in dental labe Making of veneer (partially covered crown) There are two possibilities: If the facette is made of the composite material – the material is applied directly on the metal framework and cured. If the facette is made od methylmetacrylic resin – te facette is modelled of wax, put into the flask (two parts) with plaster, after the plaster has been set, the wax is removed with hot water and replaced with resin dought, closed again and the resin is polymerized in hot water. The procedur eis principally the same as with jackette crown made of methylmetacrylic resin. Jackette crown – ceramics, resin, composite 1. Phase in dental office Preparation – Reduction 1 mm around, incisally 1, 5 mm Preparation border – rectangle shoulder Located subgingivally 0,5 mm. Taking impression Elastomeric impression materials Polysulfid, silicon, elastomers.: Retraction cord around the tooth Dual viscosity technique. a) Dual viscosity technique – double impression or – two phases b) Dual viscosity technique – one phase Antagonal impression Alginate Occlusal registration (wax, elastomeric materials) 1. Phase in dental lab. Making the cast (model) of gypsum. There are three types of base raw materials derived from partial dehydratation of gypsum rock depending on on the nature: Plasters – fluffy, porous, least dense. Hydrocal – hihger density, more crystalline Densite – densest of the raw material. Plasters----- Model plaster, lab plaster Hydrocal----dental stone Densite ------High strength dental stone On the model the technician makes Wax pattern – not of the casting wax, but of modelling wax (pink colour) The model must be isolated. The wax model of the crown is put into a flask (two parts), after the plaster has been set, the wax is removed with hot water and replaced with resin dought, the flask is closed and the resin is polymerized in hot water. 2. Phase in dental office Try and cementation. REMEMBER! BEFORE TAKING THE IMPRESSION THE GINGIVAL SULCUS MUST BE OPEN USING THE RETRACTION CORD! The cord is emoved after the imperssion with the thick materiál before the impression with cream is used. If one phase technique of the impression is used, the retraction cord is removed before taking the impression.