Accurate impressions of your prepared tooth are an essential part of the dental crown procedure. Even the tiniest flaw in the impression can result in a ill-fitting crown.
Once the tooth has been prepared, your dentist may decide to use a gingival retraction cord to gently push your gum tissue away from the margins of the prepared tooth. A gingival retraction cord is a thin piece of cord, similar to a piece of yarn, that is gently inserted around the tooth, into the gingival sulcus. Some dentists have adopted other techniques for isolating the tissue, such as gingival curettage.
When the tooth is ready for the impression, your dentist will then take an impression of your teeth. Your dentist will begin the impression by applying a polyvinyl siloxane impression material around the prepared tooth. The dental assistant will begin filling the impression tray with a corresponding impression material. Your dentist will insert the impression tray over your prepared tooth, and ask you to bite down. It is very important for you to remain biting into the impression until the material is fully set. This impression takes between three and five minutes to fully set, so patience is certainly a virtue during this step of the dental crown procedure. Once the impression material has set, your dentist will remove the tray from your mouth and inspect the impression for any air bubbles or other void in the impression. It may be necessary to repeat the impression several times in order to obtain a very accurate impression.