Periodontal Ligament Stress Level and Tooth Movement

Orthodontic treatment requires application of force systems to individual teeth or groups of teeth, which results in a cellular response with periodontal ligament (PDL) and alveolar bone remodeling. The forces applied must be of sufficient magnitude and duration to exceed the normal physiologic threshold associated with daily oral function. Excessive force levels will result in areas of tissue necrosis with delayed tooth movement and increased risk of root resorption. Although orthodontic tooth movement is achieved in a large segment of the population, the optimum force level has not been defined. The optimum force for tooth movement depends on individual root geometry as well as biologic characteristics of surrounding tissue including bone density, periodontal thickness, and fluid dynamics. Because experimental and clinical techniques are generally limited to known complex force systems, biomechanical modeling has become a necessity. Such models must be validated with well-controlled clinical studies that evaluate orthodontic tooth movement over an extended distance. The ultimate goal would be development of a computer simulation model to predict tooth movement in the clinical setting. The primary objective of this study is to test controlled clinical data with a biomechanical model of the tooth and supporting tissues for distal movement of the human maxillary canine tooth (of known root geometry) in response to various 3D force systems that produce different levels of stress in the supporting tissues. Secondary objectives include evaluation of rate of bodily tooth canine movement with two known compressive stress levels (13 and 22 kPa), evaluation of three different reference systems to measure rate of tooth movement, and evaluation of an implant placed in the roof of the mouth (palatal implant) for orthodontic anchorage in adolescent patients. The rate of translation (bodily) tooth movement of the maxillary canine tooth will be significantly greater with 22kPa