Clinical Trial: Periodontal Ligament Stress Level and Tooth Movement

Study Status: Completed
Recruit Status: Completed
Study Type: Interventional

Official Title: Clinical/Numerical Study of the Effects of Periodontal Ligament Stress Level on the Rate Bodily Tooth Movement

Brief Summary:

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

Detailed Summary:

The patients will be drawn from those recruited for the Graduate Orthodontic Graduate Program. Clinical academic staff will examine approximately 500 patients seeking orthodontic care. Patients are categorized by malocclusion type and placed into a patient pool from which some cases are selected for treatment based on the program teaching and research needs. Each year approximately 50% of patients seeking care are ultimately accepted. Treatment is provided at fees that are approximately 60% of those charged in private practice.

Patients who meet the selection criteria for this study will be randomly selected from the University of Alberta Graduate Orthodontic Graduate Clinic patient pool. Upper 1st premolar teeth will be extracted and full fixed orthodontic appliances (Ormco Orthos prescription) will be placed. After the initial alignment and leveling phase is completed the retraction phase will begin. Non-steroidal anti-inflammatory agents will be avoided; only extra strength Tylenol will be prescribed as necessary for any momentary pain or discomfort. Maximum posterior anchorage will be attained through a palatal implant (Straumann) according to the protocol described by Papadakis. The implants will be also used as three-dimensional movement reference points. Other reference systems to be used include the palatal ruggae and occlusal templates. The cuspid retraction force delivery mechanisms will consist of customized activated stainless steel T-loops designed to generate the required forces on the bracket. Approximate compressive stress (based on approximate root surface area) of 13 kPa and 22 kPa will be applied on the distal aspect of the cuspids. The design will be a split-mouth study in which both levels of stress will be applied in each patient. The side to which the higher and lower stress levels are applied will be randomized. This design will allow for inter and
Sponsor: University of Alberta, Graduate Orthodontic Program

Current Primary Outcome: Rate of space closure

Original Primary Outcome: Same as current

Current Secondary Outcome:

Original Secondary Outcome:

Information By: University of Alberta, Graduate Orthodontic Program

Dates:
Date Received: December 21, 2004
Date Started: March 2004
Date Completion:
Last Updated: June 28, 2010
Last Verified: June 2010