Centers of resistance of the maxillary complex: Theoretical models and practical applications in orthodontics.

The center of resistance of the maxilla and its constituent structures is a fundamental biological and biomechanical parameter that must be seriously considered during orthodontic treatment. This is due to its importance for the prognosis and the control of the various orthodontic and orthopedic procedures. This paper attempts a critical literature review in order to discuss the current concepts concerning the location of the center of resistance of teeth, segments of the upper dental arch and the maxilla / upper dental arch complex. This review showed that there is an ongoing discussion about the location of the center of resistance of the maxilla / upper dental arch complex. There are two points of view concerning the maxillary complex. According to several authors, whose views are mainly based on clinical observations, the maxillary center of resistance is located at the most superior and posterior part of the zygomatomaxillary suture. On the other hand, laboratory research supports that the center of resistance is located within the pterygomaxillary fissure. Concerning the center of resistance of individual teeth, it is situated at a point located 1/3 to 1/2 of the distance from the alveolar crest to the root apex, whereas the same point of a group of teeth varies depending on the size of the dental group. Despite the fact that several in vitro studies have located the center of resistance with relative accuracy, it is very difficult to apply these findings to human beings. Several authors suggest specific clinical applications based on the theoretical approaches mentioned above, but so far well-documented clinical research has not been able to establish the exact location of the center of resistance.