lab technician working on dental impression

If you have ever had serious dental work done, it is likely that you had had a dental impression taken Dental impressions are very common and are used for a variety of purposes in the dental field. Impressions can be used to create mouth guards, whitening trays, retainers, crowns, bridges, veneers, dentures, and accurate models, among other things.

A dental impression is an imprint of the teeth and mouth from which shaped items can be formed. Dental impressions produce a close replica of your teeth and oral tissue. A metal or plastic “horseshoe” shaped tray is chosen to fit the teeth and gums comfortably. A tray can be molded for either the top teeth, the bottom teeth, or both.

How Dental Impressions Are Made

In order to make a dental impression, a thick liquid material, such as alginate or polyvinylsiloxane, is dispensed into an impression tray that is shaped like a U in order to properly fit into a mouth.

Alginate is found within the cell walls of brown seaweeds. The seaweed is part of the phylum Phaeophyceae family and is harvested internationally to be converted into the raw material sodium alginate. This substance is what’s used to create the Alginate product. Depending on the species of seaweed, various chemical structures can be found within each plant.

There are certain species of plant which will yield a product of higher gelling capacity; perfect for molding hands or feet. Some plants will offer a weaker gel that it’s used within the medical genre of application. The color of the gel is also dependent on the type of plant used as well.

As a naturally occurring product found within brown seaweed, Alginate is considered both food and dermatologically safe. Alginate is known for its ability to absorb water, making it a useful product in the medicinal field. It is currently found in some slimming aids (weight loss assistance), thickening agents for soups, jellies, ice cream, cosmetics, drinks and pharmaceutical preparations.

There are two main types of impression trays: stock trays and special trays. Stock trays are manufactured in bulk in a variety of shapes and sizes. A dentist will then select the closest-matching stock tray in size and shape for each individual patient. Special trays, which are also known as custom trays, are produced to the exact specifications of a particular individual.

The particular type of liquid that is utilized for impression taking varies based on what the impression is needed for. Some impressions call for a rigid mold, while other impressions require more elastic, or pliable material.

After the liquid material is poured into the tray, it is then placed onto either the upper or lower set of teeth so that it covers the entire dental arch. Like the material that is used, the area that the impression covers varies depending on what kind of work the patient needs to have done. The roof of the mouth is included for an upper impression, and the floor of the mouth and under the tongue is included in lower impressions.

After a preset amount of time, the liquid material sets and hardens, and become a solid rubber mass. The tray is then removed from the mouth and is sent to the clinical laboratory or dental laboratory for further processing.

Stone is poured into the hardened impression and when set a dental cast is produced. This forms an almost extra replica of the mouth from which it has been molded.

Uses of Dental Impressions

Dental impressions have many uses in the dental field and are commonly used in dentistry for making:

  • Custom mouthguards
  • Custom take-home whitening trays
  • Custom dental trays used for precise impression taking
  • Crowns, bridges, and veneers
  • Dentures
  • Custom abutments for dental implants
  • Models for diagnostic study
  • Model for a permanent dental record before and after dental treatment