Root resorption caused by orthodontic treatment: an evidence-based review of literature.

Literature on apical root shortening published in the 1990s is reviewed. Three categories were assigned: sample-based clinical studies, clinical case reports, and animal model studies. Great variability for root shortening was reported, including resorption experienced by individuals who had never undergone orthodontic treatment. Some studies attempted to predict severe resorption whereas others compared different types of treatment. Included are several histological studies of teeth that were moved in humans. Very few of the sample-based clinical studies were prospective, randomized clinical trials. Data from a study that the author was involved in was used to estimate the percentage of patients who would experience different amounts of apical root shortening. It was estimated that 5% of the patients treated would experience more than 5 mm of root shortening.