I want to comment on the article “Approximation and contact of the maxillary central incisor roots with the incisive canal after maximum retraction with temporary anchorage devices: report of 2 patients” in the September issue (Chung CJ, Choi YJ, Kim KH. Am J Orthod Dentofacial Orthop 2015;148:493-502). The authors reported that the root resorption of the maxillary central incisors was due to the dense cortical bone that surrounds the incisive canal after maximum retraction that is possible because of the use of temporary anchorage devices in severe bidental protrusion cases.
This may well be so, but the most obvious cause is the overretraction beyond the palatal cortex seen on the cephalometric superimpositions and x-rays (Figs 3, 5, and 8). In addition, and of greater consequence, retraction into and beyond the palatal cortical plate and the lingual aspect of the mandibular synthesis often leads to crestal bone loss of the incisors. This loss is obvious in the periapical x-rays in Figures 3 and 8. I suspect that this loss may also be present for the mandibular incisors of patient 2, but the panoramic x-rays as published are difficult to read. Periapical x-rays should be mandatory for treated adults.
Crestal bone loss has greater consequences than root resorption because there is much greater retention of the tooth in this region and because of future periodontal concerns.
In treating a severe bidental protrusion, the orthodontist must accept a more limited reduction in the protrusion so as not to violate the limits of the posterior cortical plates of the alveolus, which are stable and do not follow the tooth retraction. If a visual treatment objective indicates that tooth movement in the confines of the alveolar housing will not be sufficient to correct the protrusive dentition and profile, then an anterior subapical osteotomy is required.