When doing treatment planning of veneers, crowns, or bridges in esthetic zone. It’s quite often that we have to place our preparation subgingivally but at the same time, we should preserve the biological width. Placing the margin subgingivally will aid in improving the esthetic as it will hide the margin of the restoration. It will also aid in retention, because we are including more tooth structure for bonding.
Before you start preparing teeth, it’s very important to measure the sulcus depth. Based on J. Kois & F. Spear, there are two rules.
1- If the probing depth is 1.5 mm or less, extend the preparation 0.5 – 0.7 mm subgingivally.
2- If the probing depth is more than 1.5 mm, go halfway the depth of the sulcus.
Now, you might be asking yourself how can i accurately place my margin subgingivally?
Well, the answer to that is quite difficult. It’s very hard to accurately place the margin by following precise measurements, however the following steps should help.
1- Place the margin juxtagingival. We mean by that, is placing it equigingival.
2- Place the first impression retraction cord. This will achieve vertical retraction of the tissues. It’s recommended that you use retraction cords with vasoconstrictor.
3- Now your margin will look like as its supragingival, prepare it more and back to be juxtagingival. That’s how you place your margins as harmless to the gingival tissues as possible.
4- Place your 2nd impression cord as you would do normally. It’s important to know that this will achieve a horizontal retraction of the tissues.
5- Wait for a few minutes and you can use Gingival Retraction Pastes for more retraction of the gingiva.
6- Remove the 2nd impression cord, and inject your light body impression material and take your final impression as you would normally do.
Reference: Style Italiano – Dan Lazar