Dental Impressions: What They Are and How to Take Them Correctly
Dental impressions of a patient’s oral cavity are intended to reproduce the tooth surface for the fabrication of prosthetics, orthodontic appliances, etc. Non-toxic materials and various trays are used to create a negative impression.
Some of the materials used include alginate and silicone. Mixing the components for dental impressions produces a homogeneous paste that hardens until it becomes completely solid. A cast is then made from the dental impressions to create a plaster model to work with.
The working time for dental impression materials is very short. The dental professional must neither exceed this time nor remove the tray from the oral cavity too early. Hence the importance of understanding the types of dental impressions and how to apply them.
How to Take Accurate Dental Impressions
Dental impressions must provide an exact replica of the tooth to reliably identify the location and configuration of the marginal line. The tissues adjacent to the tooth must be perfectly reproduced by the dental impressions to achieve an accurate model. Above all, the impression must be free of air bubbles.
The gum must be healthy and free of inflammation to ensure success. The marginal line of the preparation must be fully visible in the reproduction, avoiding fluid in the sulcus. To achieve this, retraction cord impregnated with chemicals that help keep the operative area of the dental impressions dry can be used.
The accuracy of dental impressions must take two aspects into account: that details can be reproduced and that dimensions do not vary. Materials with good dimensional stability maintain their shape and size for a longer period of time. It is important to consider whether the impressions will be sent to a laboratory or taken in the clinic itself. This determines whether greater or lesser dimensional stability is required.
The dental impression material must have the precise strength to allow it to be removed from the mouth without leaving any fragments behind. Although it must set quickly once placed in the mouth, it must remain soft while the mixture is prepared, loaded into the tray, and brought to the patient’s mouth.
Finally, dental impressions must be compatible with the materials used in the casting process.
