Impression Materials Lab 6 PDF

IMPRESSION MATERIALS DR. ADLA AHMED What is IMPRESSION MATERIAL? It is the material which is used to take an impression of teeth and soft supportive tissues. Ideal properties of Impression Material : Non-toxic and non-irritant ( Bio compatible ). Good flow. Easy manipulation. Di...

IMPRESSION MATERIALS DR. ADLA AHMED What is IMPRESSION MATERIAL? It is the material which is used to take an impression of teeth and soft supportive tissues. Ideal properties of Impression Material : Non-toxic and non-irritant ( Bio compatible ). Good flow. Easy manipulation. Dimensionally stable after setting. Acceptable price and availability. Good shelf life. Acceptable setting time. Pleasant taste, odour, and color. Non-elastic impression material: 1- Impression Plaster ▪ Earliest impression material in dentistry. ▪ Rigid impression materials (it has limited flow). ▪ Used in mild or no undercuts. ▪ Only used in edentulous patients (final impression). Uses of impression plaster : 1-Final impression of edentulous patient. 2-Bite registration. Properties : * Setting time 3–5 minutes. * Brittle and fractures easily. 2- Impression Compound ▪ one of the oldest impression materials. ▪ Rigid, Reversible. ▪ Thermoplastic (set by physical changes). Uses of Impression Compound: ▪ Preliminary impression of edentulous patient. ▪ Special tray. Composition ▪ Border molding. Ingredients Parts Resin 30 Copal resin 30 Carnauba wax 10 Stearic acid 5 Talc 25 Coloring agents Impression compound Type I Brown cake Type II Green stick Type I : brown cake impression compound non-elastic impression material Used to take a Primary impression ( poor details ). Softened with heat, harden with cooling. Used for edentulous patients with mild or no undercut. Type II : Green stick impression compound non-elastic impression material Border molding of custom tray. Softened with flame. Glossy when its soft, matt when its hard ( over heat will cause oil loss ). Impression compound component : Wax Natural resin Filler and pigments (fillers give viscosity which makes it rigid / pigment gives color). Stearic acid: as a lubricant material to make it to work with. Impression compound become Soft at 45 - 60 max and Hard at 37 degree. 3- Zinc Oxide Eugenol ( ZOE ) non-elastic impression material Comes in 2 tubes: 1-Base ( zinc oxide ) , white 2-Catalyst ( eugenol ) , colored ▪ Used for Secondary/final impression for edentulous patient. ▪ It have Sedative effect. ▪ Very thin and brittle “handle with care after taking an impression”. ▪ Used in patients with no undercuts (otherwise it will break ). ▪ It’s poured with stone not plaster. ▪ It’s mixed on a glass slab. ▪ Used as temporary filling. ▪ Used as bite registration material. 4- Impression waxes non-elastic impression material Elastic impression material: 1.1-Agar reversible Hydrocolloid elastic impression material 1.2-Alginate irreversible Hydrocolloid elastic impression material 1.1-Agar reversible Hydrocolloid elastic impression material It is an organic hydrocolloid extracted from certain types of seaweeds. Its reversible material, so it could be reused (change with heat). Used to take final impression. Supplied as 2 forms: 1-Syrings 2-Tray material Composition: 1. Agar 2. Borax 3. Potassium sulphate 4. Benzoate 5. Additives 1.2-Alginate irreversible Hydrocolloid elastic impression material It is an irreversible impression material. Replaced agar agar recently. Used for primary impression (poor details). Used with undercut. Comes in different colors. Composition 2 types of alginate: normal-setting alginate Setting time :2 - 5 minutes. Working time :2 minutes. Mixing time :60 sec. fast-setting alginate Setting time: 1 - 2 minutes. Working time :1 minute. mixing time :45 sec. CONTROLLING SETTING TIME 1. Powder / water ratio : More powder >> decreases setting time (sets faster) Less powder >> increases setting time (delayed setting) 2. Water temperature : Cold water >> increases setting time Warm water >> decreases setting time How to know that the alginate is set? - When it becomes rubbery. - Some alginates change color when it set. *You have to poor the impression within 30 mints. *If left more than 24 hours there will be dimensions distortion.  Syneresis : impression dry out and shrink. Imbibition : impression soak water and expand. Advantages Disadvantages Elastic material. Poor details production. Cheap material. Tears easily. Good taste. Poor dimension stability. Easy to mix & manipulate. Comfortable to patient. Hygienic. Disinfection of impressions: Iodophores Sodium hydrochloride Glutraldehyde Phenyl phenol 2.1-Polysulfide elastomer elastic impression material 2.2-Polyether elastomer elastic impression material 2.3-Sillicone elastomer elastic impression material 2.1-Polysulfide elastomer elastic impression material It is a synthetic elastomeric impression material. Supplied as 2 paste system : Base : white. Accelerator : gray or brown. Available in 3 viscosities : 1-Light bodies. 2-Medium bodies. 3-Heavy bodies. Working time : 5-7 minutes. Setting time : 8-12 minutes. Impression pouring : 30-60 minutes.  Advantages Disadvantages Good flexibility Long setting time Tear resistance Unpleasant odor High detail surface Long setting time Secondary impression 2.2-Polyether elastomer elastic impression material It is an elastic impression material used to take secondary impression. Come as Base and Accelerator. Available in 3 viscosities: 1- Light bodies. 2- Medium bodies. 3- Heavy bodies. Working time : 2-5 minutes Mixing time : 4-5 minutes Impression pouring : up to 1 week of storage Advantages Disadvantages Easy to mix and handle Allergic reaction High accurate Rapid setting time Good surface details Expensive Dimensionally stable High stiffness Non toxic Good on undercuts 2.3-Sillicone elastomer elastic impression material *It is an elastic impression material used with both stock and special trays to take final impression. *Supplied as : 2 pastes OR paste and liquid (Base : give the material thickness and Catalyst : accelerate the reaction). 2.3.1-Condensational Sillicone elastomer elastic impression material *Available as : 1-Light body. 2-Medium body. 3-Heavy body. 4-Very heavy body (putty). Working time : 3 minutes Setting time : 6-8 minutes Impressoin poured : within first 30 minutes  2.3.2-Additional Sillicone elastomer elastic impression material *Available as : low, medium, high, and very high consistencies. *Supplied as : jars, cartridge, syringes, and sausages. *The base is colored while the catalyst is white in color. Working time : 2-5 minutes Setting time : 3-7 minutes Impression poured : up to 1 week Advantages Disadvantages Dimensionally stable Expensive Excellent surface detail Short working time Non toxic, non irritant Can’t use it with latex Easy to use Fast setting 1.Light body additional silicone elastomer elastic impression material -Usually used in combination with another additional silicone -Used to take final impressions for crowns and bridges 2.Medium body additional silicone elastomer elastic impression material -Can be used alone or in combination to take final impressions 3.Heavy body additional silicone elastomer elastic impression material -Can be used alone or in combination 4.Putty additional silicone elastic impression material Used to take a primary impression or in combination with another silicone for final impression. Used for border molding in complete denture patients {sometimes instead of greenstick compound}. Latex in gloves affects the polymerization of the material {gloves should not be worn while mixing the product or use nitrile gloves}. One step technique 1. Mix putty (base & catalyst) and adapt on tray. 2. Immediately inject light body around prepared tooth or teeth. 3. Take an impression {both materials polymerize simultaneously}. Two step impression technique 1. Mix putty (base & catalyst). 2. Adapt on a tray and place separator on top. 3. Take an impression. 4. After the impression is set remove it from the patients mouth and Remove the separator. 5. Inject light body over the set putty impression and retake the impression again. 6. Wait until the impression sets and then remove it.