Dental impressions are negative imprints of the teeth and oral cavity (gums, surrounding tissues, etc.). Impressions are used to create three-dimensional models are commonly used in prosthodontics, orthodontics, dental crowns and bridges, and oral and maxillofacial surgery.
What are the Types of Dental Impressions?
There are three main types of dental impressions — preliminary, final, and bite registration.
- Preliminary impressions are accurate reproductions of a patient's mouth, used for the diagnosis, documentation of dental arches, and visual aid for education.
- Final impressions have the exact details of the tooth structures and their surrounding tissues. They are used to make casts and dies with the precise details of the tooth structures and their surrounding tissues. Dental laboratory technicians utilize the forms to construct crowns, bridges, dentures, and other restorations.
- Bite registrations are employed to document the occlusal relationship between arches, which is essential when establishing the articulation of maxillary and mandibular casts.
Materials Used to Create Dental Impressions
The most widely used material, especially for preliminary impressions, is irreversible hydrocolloid. Hydrocolloids can exist in a sol or a gel state. The physical transformation from sol to gel called gelation can either be reversible – changed by thermal factors – or irreversible – changed by chemical elements, depending on the type of hydrocolloid used. Irreversible hydrocolloids do not change after gelation.
The most often used irreversible hydrocolloid is alginate. Alginate is a naturally-occurring polymer usually obtained from brown seaweed. This biomaterial has numerous applications in biomedical science as well as engineering due to its biocompatibility.
How Dental Impressions are Created
Impression material goes on an impression tray. Then, the tray goes in the mouth.
The trays are designed for different mouth areas and included quadrant trays that cover half an arch and fill and full trays that cover the complete maxillary or mandibular arch.
Metal, plastic, or disposable Styrofoam trays are available in various sizes suitable for children and adults. Trays may also be perforated or pierced with holes to promote a mechanical lock with the impression.
The liquid material, which varies depending on the impression's use, is poured into the tray. Impressions may demand a rigid mold or a more elastic or pliable material. Tray selection will also depend on the purpose of the impression.
Following the liquid's pouring into the tray, the tray is then placed onto either the upper or lower set of teeth, covering the entire dental arch. The impression covers also differ depending on the kind of dental work the patient's condition requires. Upper impressions include the mouth's roof. Lower impressions include the floor of the mouth and under the tongue.
After removing the tray, the material hardens and goes to a dental laboratory.
The Thing about Taking Dental Impressions is…
Because of how impressions are taken, you might feel like gagging. Before the trays go in, take some deep, relaxing breaths through your nose and continue to breathe through your nose.
What are Digital Dental Impressions?
Digital impressions utilize digital technology to create dental images on a computer, saying goodbye to the traditional method of impression tray and liquid material. No more gagging and no goop. Hawaii Family Dental uses state-of-the-art digital dental impressions.