Dr. Beatrice Leung Dentistry Professional Corporation

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A Difficult Crown Impression

When I started practicing, I was sometimes surprised to see a referral for a single crown.  And more often it is the second molar with a very limited opening where access is difficult and the distal margin has to finish subgingivally.  When I see a case like that, I will often treatment plan the case with a full coverage restoration and the possible need for crown lengthening.

These cases are difficult even if you plan for restorative crown lengthening because access is difficult even for the periodontist.

Despite the difficulty, I have always applied my basic principles of final impression taking and they have worked most of the time.

So here are some basic principles:

1/Make sure you have provided adequate tooth preparation and fabricate a well fitting temporary crown.  I know it is often easy said than done but if your temporary crown is not well contoured, then the tissue will be inflamed when you try to take the final impression.

2/If the tissue is quite beat up after the tooth preparation, then I put on well contoured temporary crown and ask the patient to come back.  Sometimes I would prescribe chlorhexidine, not for the patient to rinse, but for the patient to massage the gum in the area with a cotton applicator or a small toothbrush dipped in the chlorhexidine solution.

3/After proper tissue retraction, if the tissue is bleeding, then I need to wait until it is ready for final impression.  My usual technique is to dab the area with cotton pellets soaked in hemodent.  If the wet cotton pellet becomes red upon application over the gingival margin, then the tissue is not ready.  My visual cue is to see a new clean wet cotton pellet to be applied to the gingival margin and it remained clean after being dabbed over the entire finish margin.

4/If there is still a lot of bleeding, sometimes I infiltrate a bit of 2% lidocaine 1:50000 epinephrine directly over the bleeding site.  I will see a bit of blanching and then I go back and check with my new wet cotton pellet soaked in hemodent over the bleeding area to see if the tooth is ready.  Basically, I don’t want to see any seepage from the gingival sulcus.  If there is, my cotton pellet will tell me that there is as it will often pick up the pigment from the gingival seepage.  This can be red or brown.  I don’t want to see any pigments on my cotton pellets.  If there is, the tissue is not ready.  Continue to dab with cotton pellet with hemodent until it remains as one white cotton pellet.  When I see that, that is when I will take the final impression.

5/Be patient and don’t rush the procedure.  Take the time to manage the tissue properly before taking that final impression.

I hope you find these simple tips helpful.  Thanks for reading!