All ceramic crown

The case shown here involves taking an impression to make a ceramic on zirconium crown. The temporary crown has been removed and any residual cement has been cleaned off completely with an ultrasound scaler.

As this is for a single crown, the impression will be taken in occlusion using a dual arch tray. The impression tray is tried, checking that the patient can bite their teeth together easily. A retraction cord can then be put in place using a small flat plastic.
The cord should be positioned below the cervical margin, avoiding burying it completely in the sulcus. The cord should remain visible along the whole length of the preparation. Part of the cord should remain accessible on the lingual side so that it can be removed easily before taking the impression.
The retraction cord is then removed carefully.
A little impression material is taken up with the forefinger from the loaded dual arch tray and spread over the preparation, working in an apical direction. This ensures that the material goes into the opened sulcus. The dual arch tray is then seated on the arch and the patient is asked to bite their teeth together. Once the material has set completely the patient is asked to open their mouth wide in a straight line.
The impression tray can then be removed, helped if necessary by compressed air directed underneath it.
The impression can then be checked. Impression quality depends mainly on the quality of reproduction of the cervical margin.
An impression taken with Apol Classe can achieve an accuracy down to about 7 microns. Once the crown has been made in the laboratory it will be tried in and then cemented in the usual way. The cord will remain in place for a few minutes to open up the gingival margin so that the cervical margin will be recorded accurately.