Elastomeric impression techniques

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based on JPD articles.

Text of Elastomeric impression techniques

By Dr. Anupriya Singh P.G. 1 st Year

Impression Techniques Comparison Various commercially available Elastomers References

SIMULTANEOUS OR DUAL VISCOSITY

TECHNIQUE (single step putty wash technique) SINGLE VISCOSITY OR MONOPHASE TECHNIQUE TWO-STEP PUTTY WASH TECHNIQUE OTHERS 1. The matrix impression system Gus J. Livaditis . 2. A simplified custom impression technique Steven J. Sadowsky .

Before making an impression the following 2

criterias are to be kept in mind 1.

Which elastomer is to be used the current choice being condensation curing silicone, addition-curing silicone or polyether. Which technique is to be employed either single impression (using a material presented as one viscosity, as is often the case with polyethers and the so called monophase silicones), or using a two-body combination (as is generally the case with either form of silicone).Brown D.: Materials for Impressions 2003. Dent Update 2004; 31: 4045

2.

In this method the wash material is syringed

into place & then unset putty is seated over light body material.

Wu and Donovan in 2007 in the Journal of

Prosthetic Dentistry.

With the 1-step procedure, low viscosity

impression material is injected around the prepared tooth or teeth, and then the putty impression material is immediately placed intraorally and the materials polymerize simultaneously.

This article describes a modified 1-step putty-

wash technique using vacuum-formed resin sheets as spacers to control the wash bulk. PROCEDURE Use the original diagnostic cast or cast recovered from an impression of the diagnostic provisional restorations to fabricate the vacuum-formed spacer.

Cast recovered from impression for provisional restoration on mandibular right first premolar.

Place the cast and a 5 x 5-inch sheet of 0.08-inch-

thick soft clear ethyl vinyl acetate on a singlechambered vacuum-forming machine . Heat until a 0.5-inch droop develops, and then vacuum form the spacer on the cast.

Do not prepare occlusal stops because they

interfere with the removal of the spacer from the putty. Trim the spacer with scissors and a hot knife to cover approximately 2 to 3 mm of marginal gingiva on the buccal and lingual surfaces of the teeth.

Vacuum-formed spacer fabricated on cast recovered from impression for provisional restoration.

Complete essential gingival displacement

procedures on prepared teeth. Place the vacuum-formed spacer intraorally and verify stability. Make a transfer impression of the spacer with high-viscosity putty impression material in a stock tray .

Vacuum-formed spacer on internal surface of putty pick-up impression.

Before the putty impression material is

polymerized, remove the entire impression from the mouth and gently remove the spacer from the putty material. Simultaneously wash the putty tray with lightbodied vinyl polysiloxane impression material to make the definitive impression.

Internal surface of washed putty impression.

Also called as the Single Viscosity technique. A medium body material is used in this technique

intraorally at the prepared site and as a tray material . Stock trays are conventinally used in this

technique. Polyethers and Addition Silicones.Craigs Restorative Dental Materials Eleventh Edition

PROCEDURE Its a technique that uses monophase materials to

accomplish an impression in a single-step procedure, using materials with a medium viscosity to allow the material itself to record the finer details while avoiding the slumping of the material in the tray.

Caputi S.,Varvara G.: Dimensional accuracy of resultant casts made by a monophase, one-step and two-step, and a novel two-step putty/lightbody impression technique: An in vitro study. J Prosthet Dent. 2008 April;99(4):274-81

First , thick putty material is placed in stock tray. Primary impression is made , resulting in intraoral custom-made tray formed by putty. Space for light-body wash material is provided by cutting some tray putty or by using various spacers. After spacer is removed thin consistency wash material is placed into putty impression . Putty wash is seated in mouth to make final impression.

The wash impression material is used to -

obtain the detail of the prepared abutment tooth and adjacent teeth. 2. compensate for deformation that occurs when the prepolymerized putty impression material is removed from the mouth.1.

Chaimattayompol N, Park D.: A modified putty-wash vinyl polysiloxane impression technique for fixed prosthodontics. J Prosthet Dent 2007;98:483-485.

Chaimattayompol and Park - 2.0 mm of relief is

recommended to achieve predictable definitive impressions with dimensional accuracy when using a 2-step putty-wash impression technique. (J Prosthet Dent 2007;98:483-485) There are a number of spacers that provide the

recommended relief in the impression.

The spacers used are as follows 1.

2.

3. 4. 5.

A spacer created by grinding away some of the putty impression material after the impression is made. J. Nissan et al - a polyethylene spacer (plastic spacer used with the putty impression first and then the wash stage). ( J Prosthet Dent 2000;83:1615.) J. Nissan et al stainless steel prefabricated copings. ( J Prosthet Dent 2000;83:161-5.) Wu and Donovan - vacuum-formed resin sheets as spacers. (J Prosthet Dent 2007;98:245-246.) Monzavi and Siadat - baseplate wax as a spacer. (J Prosthet Dent 2005;93:494.)

Chaimattayompol and Park in 2007 in the Journal of

Prosthetic Dentistry. The technique presented in this article is a modification of a 2-step putty- wash impression technique without using a spacer. It uses the concept of primary pressure from partial polymerization (30 seconds after mixing) of a fast-set putty material that is impressed while placed around the prepared abutment tooth, which then helps push the wash impression material subsequently injected to record details of tooth preparation.

PROCEDURE Select a stock tray appropriate for the dental arch

to be impressed and apply vinyl polysiloxane impression tray adhesive Place retraction cord in the gingival sulcus. Mix putty base and catalyst impression material for 30 seconds, and quickly load into the impression tray. Insert the loaded impression tray intraorally while the retraction cord is still in place, and maintain the tray in position for approximately 30 seconds. Ensure that the tray handle is oriented to the facial midline for future reference. Remove the impression tray from the mouth.

Remove the retraction cord and immediately

syringe extra-light impression material onto the prepared abutment and adjacent teeth.

Extra-light-body impression material on prepared abutment and adjacent teeth.

In the meanwhile a dental assistant loads the

wash impression material onto the prepolymerized putty impression .

Extra-light-body impression material on impression surface of prepolymerized putty impression in impression tray.

Reinsert the impression tray into the same

position and allow the material to polymerize for the time period recommended by the manufacturer. Separate the impression tray from the mouth and examine the definitive impression.

Complete arch definitive impression. Note there is no delamination between 2 impression materials.

ADVANTAGES

it allows a prepolymerized putty impression material to anatomically form around the prepared abutment tooth and, therefore, in the authors opinion, create greater pressure, forcing the wash impression material so that it penetrates into the gingival sulcus more easily. 2. accurate detail can be obtained without the need for a custom- made matrix to assist in making a definitive impression. 3. it is less time-consuming when compared to the 2-step putty-wash impression technique. 4. there is no delamination between the 2 different viscosity impression materials (putty and wash).1.

The primary disadvantage of this technique is

that it is time-sensitive And requires coordination between a dentist and a dental assistant to inject the light-body material into the prepared tooth and prepolymerized fast-set putty impression immediately upon removal from the mouth. However, a single operator without a dental assistant can accomplish the same technique by using the regular set impression material. The use of a cheek retractor is also helpful to facilitate this process.

The matrix impression system Gus J. Livaditis .

A simplified custom impression technique Steven J. Sadowsky .

Gus J. Livaditis in 1998 in the Journal of Prosthetic

Dentistry. This technique focuses on making successful

subgingival impressions. Four forces that must be controlled when making

subgingival impressions are retraction forces, displacement forces, collapsing forces, and relapsing forces.

MATERIAL AND METHODS The MIS uses three impression materials:

a suitable elastomeric semirigid material required to form the matrix. 2. a high viscosity elastomeric impression material, which will preferably bond to the matrix-forming material, required to make an impression of the preparations in the matrix. 3. a stock tray with a medium viscosity elastomeric impression material to pickup the matrix impression and the remaining arch not covered by the matrix.1.

CLINICAL PROCEDURE Forming the matrix Immediately after tooth preparation and before

any retraction procedures, select or create a carrier for the matrix forming material.

Maxillary anterior teeth prepared for full crowns