Mohammed H Elnagar1,2, Chester S Handelman1, John S Lippincott3, Myung-Rip Kim1,4,5, Ellen BeGole1. 1. Department of Orthodontics, College of Dentistry, University of Illinois at Chicago, Chicago, IL, USA. 2. Department of Orthodontics, Tanta University, Tanta, Egypt. 3. Private Practice, Aurora, IL, USA. 4. Private Practice, Seoul, South Korea. 5. Catholic University of Korea, Seoul, South Korea.
Abstract
OBJECTIVE: The extent to which the modelling behaviour of the anterior alveolus limits tooth movement remains unclear. Will the labial and lingual cortical plates model as incisors retract, or will they remain unchanged, therefore limiting the extent of possible tooth movement? SETTING AND SAMPLE POPULATION: Pre- and post-treatment lateral cephalometric radiographs of 29 bimaxillary protrusive patients of South Korean descent were examined. Treatment consisted of two premolar extractions in one or both arches with en masse retraction of the incisors using miniscrew anchorage. MATERIALS AND METHODS: Pre- and post-treatment measurements of both tooth and cortical plate position were made at various increments along the length of the root and then compared using paired t tests. RESULTS: Despite the use of miniscrew anchorage, the incisors were retracted by controlled tipping. The labial cortical plates in both arches modelled to follow tooth movement. Following retraction of the incisors in the maxilla, the incisor root approached the lingual cortical plate, which remained unchanged. In the mandible, the lingual cortical plate position was unchanged except at the level closest to the cementoenamel junction. CONCLUSIONS: The maxillary and mandibular lingual cortical plates did not model to follow the incisor movement while the labial cortical plates did. These findings suggest that lingual cortical plates may act as limitations to planned orthodontic tooth movement.
OBJECTIVE: The extent to which the modelling behaviour of the anterior alveolus limits tooth movement remains unclear. Will the labial and lingual cortical plates model as incisors retract, or will they remain unchanged, therefore limiting the extent of possible tooth movement? SETTING AND SAMPLE POPULATION: Pre- and post-treatment lateral cephalometric radiographs of 29 bimaxillary protrusive patients of South Korean descent were examined. Treatment consisted of two premolar extractions in one or both arches with en masse retraction of the incisors using miniscrew anchorage. MATERIALS AND METHODS: Pre- and post-treatment measurements of both tooth and cortical plate position were made at various increments along the length of the root and then compared using paired t tests. RESULTS: Despite the use of miniscrew anchorage, the incisors were retracted by controlled tipping. The labial cortical plates in both arches modelled to follow tooth movement. Following retraction of the incisors in the maxilla, the incisor root approached the lingual cortical plate, which remained unchanged. In the mandible, the lingual cortical plate position was unchanged except at the level closest to the cementoenamel junction. CONCLUSIONS: The maxillary and mandibular lingual cortical plates did not model to follow the incisor movement while the labial cortical plates did. These findings suggest that lingual cortical plates may act as limitations to planned orthodontic tooth movement.