My knowledge about orthodontic root resorption has gone up today thanks to Dr. Vince Kokich. I spent the last 2 hours or so writing my next synopsis for the Seattle Study Club Journal. This article is taken from a presentation Dr. Kokich and Dr. Henry Nichols gave at the 2013 Seattle Study Club Symposium on the “Restorative Orthodontic Interface”. During the presentation Dr. Kokich addressed some critical elements about orthodontic root resorption that have been questions I have as a restorative dentist for many years.
The first question is whether resorption can occur during an additional round of ortho if it occurred the first time? The answer is “no”, it can not happen again. Before teeth are moved initially the roots are covered by acellular cementum which contributes to the occurrence of resorption. After an initial episode of resorption, once the orthodontic forces are discontinued the roots heal by forming cellular cementum. This cellular cementum protects the roots from any additional rounds of root resorption. This helps me make sense of hearing previously that one way to manage resorption is to start tooth movement and then stop it, while leaving the brackets and wires in place and then resume tooth movement again.
The next question is what contributes to resorption? I addressed some of these factors in a previous post about resorption and occlusal forces. The amount of force is not a contributing factor to root resorption. With that said, the amount of tooth movement and the direction of tooth movement are contributing factors to resorption. For instance intrusion creates ischemia at eh apex of the roots and needs to be monitored closely for resorption. I also quoted some incidence rates for resorption in my previous post, and Dr. Kokich confirms about a 4% overall risk during orthodontic treatment.
With the answers to these two big questions answered I feel more confident in recommending additional ortho to adult patients with radiographic evidence of previous resorption, as well as explaining this phenomenon to my patients.