Previously in Part I and Part II of this series, I discussed the concept of biologic width and the concerns about placing restorative margins too deep, violating the attachment and subsequently producing gingival inflammation or bone loss. In this article, I’ll describe the two different types of gingival presentations we encounter when approaching subgingival margin placement, as well as the risks of each. Whenever I contemplate placing a margin subgingival, I always start by probing the facial sulcus of the teeth I will be placing the restorations.
Biologic Width: Possible Gingival Presentations
It is important to realize that when we probe the sulcus, the probe routinely enters the epithelial attachment .5 mm, meaning the actual sulcus is typically .5 mm less than the probed depth. In patients with inflamed tissue, the probe penetrates even deeper into the attachment. In patients with normal or shallow facial sulcus depths, typically 1 mm to 1.5 mm, the risk in subgingival margin placement is going too deep and violating the attachment, as the histologic sulcus depth is probably less than 1 mm. The good news is these patients do not typically present a high risk of recession following placement of the restoration since the gingival dimension above bone is commonly 3 mm on the facial, similar to the Gargiulo diagram in my previous articles. This means there would have to be bone loss for the tissue to recede apically. So going below tissue more than .5 mm to .7 mm is unnecessary, and it is unlikely the margin will violate the attachment or be exposed from future recession. (Figures 1 and 2) The second presentation is a patient with much deeper facial sulcus depths, 2 mm to 4 mm – or even more. This patient presents a much higher risk of recession following restoration unless the margin is placed farther below tissue. The reason for the risk of recession is due to the fact that there are several millimeters of unattached gingiva above the biologic width. The thickness of the unattached tissue has an influence on the risk of recession; the thinner the tissue and deeper the sulcus, the greater the risk of recession. The good news is it is very difficult to violate the biologic width on these patients as you would need to prep 2 mm to 4mm below gingiva to reach the attachment. (Figures 3 and 4) In subsequent articles, I’ll describe the options and steps to manage these different presentations.