Root shape before and after orthodontic treatment with radiographic evidence was first given by:
The risk of severe localized resorption is much greater for maxillary incisors (3% affected versus <1% for all other teeth. Kaley and Phillips reported a 20-fold increase in the risk of severe resorption for maxillary incisors if the roots were forced against the lingual cortical plate during treatment. This is likely to occur during camouflage treatment for skeletal problems, when the maxillary incisors are torqued (as in Class II patients) or tipped (as in Class III treatment) so that the root apices are thrust against the lingual cortical plate. Contact with the cortical plates also can explain other patterns of localized root resorption, such as resorption of lower molar roots when buccal root torque is used in an effort to augment anchorage.
Kaley and Phillip
Newman and Proffit
Ketchman AH
Malmgren and Levander