![]() Low-consistency material is injected with a syringe into critical areas.MEANWHILE, AN ASSISTANT MIXES THE HEAVY-BODIED MATERIAL.Mixture should be free of streaks and bubbles.THE LIGHT-BODIED MATERIAL IS THOROUGHLY SPATULATED.On separate pads (one for the tray and one for the syringe material), disperse equal amounts of base and accelerator.A simultaneous, dual viscosity technique (Heavy Body-Light Body Combination ) A simultaneous, dual viscosity techniqueġ. Inject the material by the syringe around the prepared toothĬommon methods for making crown and bridge impressions are:ġ.Some of the material is applied to the syringe while the rest is applied to the tray.The impression Material for the mono-phase technique has one viscosity for tray and syringe. Impression Making A) Single Mix (mono-phase) Technique These are placed on non-centric cusps of teeth that are not to be prepared. Stops are needed in the tray to maintain even space for the impression material. Retention is provided by perforations, rim-locks, and/or tray adhesives.Ī custom tray improves the accuracy of an elastomeric impression by limiting the volume of the material. Stock trays can be used with these impression materials. Newer products contain “ scavengers” that prevent the escape of gas at the polymer-cast interface.Īddition silicone that contains scavenger material can be poured immediately. If this is not done, a generalized porosity of the cast surface caused by gas from the impression material will develop. Pouring should be delayed with some of the earlier products. Comes in different viscosities (consistencies).Surfactants have been added to the material to decrease it hydrophobicity.Least affected by pouring delay of any material (due to no volatile by-product formation).Pouring can be delayed to produce accurate casts even more than a day after the impression has been made.No volatile by-product is formed which results in excellent dimensional stability.Silicone impression material is available in a variety of viscosities.(H2O for polysulfides and ethanol for Condensation Silicones) The above occurs due to the evaporation of the by- product of the condensation reaction.Dies produced from this material can be undersized.Can have pronounced shrinkage (poor dimensional stability).Will begin to shrink after one hour from removalĪlthough it is the least expensive elastomer, it is not well-liked by patients because of its unpleasant sulfide odor and long setting time in the mouth (about 10 minutes).Comes as two tubes of base and catalyst.Multiple pouring within 24 Hours after making impression.High accuracy (very small contraction It must be free of bubbles, especially in the area of the finish line and occlusal surfaces of the other teeth in the arch. Other teeth and tissue adjacent to the prepared tooth must be accurately reproduced to permit proper articulation of the cast and contouring of the restoration.ģ. It should be an exact duplication of the prepared tooth, including all of the preparation and enough un-cut tooth surface beyond the preparation to allow the dentist and the technician to be certain of the location and configuration of the finish line.Ģ. Requirements of an impression for a cast restoration:ġ. If it becomes necessary to store the impression before a cast will be made, the polyethers and addition silicones are preferable because they exhibit sufficient long-term dimensional stability the other materials, particularly the reversible hydrocolloids, must be poured immediately. They will allow the cast to be accurately articulated (to check occlusion) and will contribute to proper contouring of the planned restoration. Used to make the final impressions for indirect restorations and implants.Īll teeth in the arch and the soft tissues immediately surrounding the tooth preparation must be reproduced in the impression. ![]() They are synthetic polymers with rubber properties after setting. WHAT IS NON-AQUEOUS ELASTOMETRIC IMPRESSION?
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