Dental impression

Dental impression information

Dental impression research and comparisons.

Impression vs digital scan

There are reasons to use both of these in certain situations but often it comes down to doctor preference.

Dental impressions

Metal tray better than plastic.   Putty better than heavy/light. 

Dental digital scans

 List of most of the big names
  • CEREC® (learn more)
  • TRIOS® (learn more)
  • Lava™ C.O.S. (learn more)
  • 3M™ True Definition Scanner
  • Cadent iTero™
  • IOS FastScan®

Dental impression concepts

  1. Mucostatic impression technique (minimal pressure)
  2. Functional impression (pressure technique)
  3. Semi-functional impression (selective-pressure technique)

VSE v VPS v PE

VSE (vinyl siloxanether) is the newest impression material and reports to have the advantages of both PE (polyether) and VPS (vinyl polysiloxane or addition silicone).

VPS better Schaefer 2013 J Pros Dent

VSE acceptable Stober 2010 J Pros Dent

VSE better Pandey JDental Medical Sciences 2014

 

Many of these numbers are so small that they are clinically insignificant.  Also important to remember that setting expansion of modern Type IV die stones is designed to match the inherent volume loss of elastomeric impression material.  Any mild improvement of accuracy may actually be hurting.

Dental impression tricks

Use a block out material for patients with bone and tissue loss from periodontal disease.

Block out material use for dental impression.

The blue blockout material goes in as a flowable and we cure it in place and then remove after the dental impression.

Tips to help take an impression on a gagger.

There are several tricks to help you take a dental impression on a gagger. The upper is usually worse than the lower so I like to start on the lower to ease the person into the impression steps. Actually I prefer to do a digital impression on a gagger whenever possible. However, if that is not an option then the following are some great tips.

  • Have the patient tilt their chin down towards their chest and breath slowly through their nose. Pretend you are smelling some really nice flowers.
  • Rinsing with saltwater before helps a lot with gagging.
  • Standing on one foot and alternating back and forth while waiting for the material to set up. Or since usually sitting, focus on crunching up the toes on one side then the other.
  • Another tip for those sitting is ask them to lift their feet or legs up.
  • Using topical numbing spray on the back of the throat helps a lot too.

Tips to help take an impression on a really small mouth (microstomia) or restricted opening.

Microstomia can be seen most commonly in patients with scleroderma but will also be seen in other patients rarely as well. Taking an impression can be challenging or impossible for some of these patients. Therefore, first off we would once again take a digital impression whenever possible. That makes life way easier on everyone. If this is not an option there are some tricks. Most revolve around a hinge mechanism or two parts of a tray that separate somehow. Tulunoglu JPD 2018 There was another version very similar in JPD years ago that may be in the references section of the 2018 article.

Dental impression problems

A failure of impression material to set has many possible causes. Material that is bad or has expired can cause issues. Temperature plays a role as does not enough time. There are also many products that can interfer with the setting of the material, most common is bonding agent.

 

Below is an example of impression material failing to set. Possible causes are too short of time, expired or poor material, cold material, impression setting inhibited by some unknown product.

Dental impression failure to set.

To see the high resolution image click here.

 

 

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