In 1-2% of patients, however, obvious root shortening occurs during routine orthodontic treatment. These patients are just more genetically susceptible to root resorption. I have even noticed that root shortening runs in families (after noticing resorption in two children from the same family I looked at the mom’s records and found the same thing). This genetic predisposition is important and should be communicated to your orthodontist if you are aware that it has been noticed in your family.
Are there things an orthodontist can do to cause or prevent root resorption? Some have theorized that root resorption happens if the teeth are moved too quickly or too slowly. Teeth that are moved too quickly may be subject to too much force they say. However, in my cases where I’ve seen resorption I’ve used exactly the same amount of force for exactly the same amount of time as everyone else. Braces that are on longer logically have more time to cause a problem. Having said that, I’ve seen transfer cases that have had braces on for more than 5 years with no signs of root change. There really is neither documented cause of nor protocol to follow to prevent this shortening.

So what can be done about root shortening during treatment? About the only thing we can do as orthodontists is monitor our patients during treatment using routine x-rays. These should be taken at least annually as long as the braces are on. If root shortening is noticed, it should be pointed out and discussed with the patient and their family. Depending upon the amount of shortening, treatment may be continued as normal, the treatment time shortened (stopping after spaces close for example), or the braces immediately removed. It is generally believed however that a tooth can lose up to half of its root length and never have a problem. In my 21 years of private practice, not a single tooth has been lost to root resorption.

Unfortunately there is nothing you can do to “re-grow” the length of the roots. All we can do in cases like this is to educate the patients, stabilize the teeth (passive bonded lingual retainers), and encourage mouth guard wear for any activities that may threaten the teeth. As I’m sure you’ve read in my article, some patients are just predisposed to root shortening and some aren’t. The only thing the orthodontist could have done differently is recognize the shortening earlier (i.e. 6 to 12 months in) and change the treatment goals (like leaving some uncorrected overjet). Luckily the shortening usually stops once the orthodontic movement stops, so it shouldn’t get any worse.
http://www.gregjorgensen.com/blog/2013/03/do-braces-make-the-roots-of-your-teeth-shorter/