In the previous article in this series, I described how osseous surgery to remove bone was a viable option for correcting a biologic width violation on the facial of a single anterior tooth, but was rarely a good option if the violation was on the interproximal. In this article I will talk about how we can manage an interproximal biologic width violation on a single anterior tooth. The reason osseous surgery is rarely indicated for correcting an interproximal biologic width violation on a single anterior tooth, is that it requires removal of interproximal bone, which is followed by a loss of papilla height, and an open embrasure. Instead the ideal treatment to expose adequate tooth structure for restoration and to allow for ideal esthetics with no loss of interproximal papilla height, is orthodontic extrusion (see image above and image below).
It is important to remember the desired outcome for the correction of the biologic width violation, the margin 2.5 mm from bone, and if it is a tooth with endo and a post and core, an additional 1.5 mm of tooth structure exposed for adequate ferrule. So for teeth with endo and post and cores 4mm of tooth structure must be exposed coronal to the bone (see image below)
There are two ways to accomplish the extrusion:
- Slow extrusion of .5 mm to 1 mm per month, which allows the bone and gingiva to follow the tooth, this is then followed by osseous surgery to reposition the bone and gingiva ideally, which exposes the tooth as well. This approach is highly predictable, and is generally chosen, especially when there are other orthodontic concerns as well.
- The second approach, which is normally chosen only when a single tooth needs treatment, ie. no other orthodontic needs, or other teeth with biologic width violations adjacent to the tooth you desire to treat, is to use rapid extrusion, generally all of the movement within 4 weeks. The key to this approach is to perform supracrestal fiberotomies weekly, to discourage the bone and gingiva from following. But it is necessary to retain the tooth in position for at least 12 more weeks to prevent re-intrusion, and to evaluate if osseous surgery is necessary due to the bone and gingiva creeping in a coronal direction (see four images below).
Finally, in all cases where forced extrusion is being used to resolve a biologic width violation, the amount of root in bone is being reduced by the amount the tooth is being extruded. While often clinicians worry about keeping a 1/1 crown to root ratio at a minimum, my experience has been that leaving 8 mm to 9 mm of root in bone has provided a successful long-term solution. In my next article, we will address the most difficult biologic width problem, both interproximal and facial violations on all the anterior teeth.