SURGICALLY ENHANCING THE SPEED OF TOOTH MOVEMENT : CAN WE ALTER THE BIOLOGY ?

Surgical treatment indeed can enhance the outcomes of orthodontic treatment. Another potential benefit of surgical intervention is the possibility of expediting orthodontic treatment. This chapter provides an overview of corticotomyassisted orthodontics and its application to molar protraction using temporary anchorage devices. The regional acceleratory phenomenon is considered to be a potential biological mechanism for achieving increased tooth movement velocity during corticotomy-assisted orthodontics. This phenomenon also might enhance the speed of the post-surgical orthodontic phase in patients undergoing orthognathic surgery. The possibility of eliminating the pre-surgical phase in combination with increased tooth movement in the post-surgical phase may result in shorter treatment times for these patients. Two case reports will illustrate the concepts of corticotomy-assisted molar protraction with miniscrews and the “surgery first” concept using miniplates. The variety of materials, concepts and techniques of modern orthodontics has evolved incrementally since the time of Edward Angle. Some may argue that the fundamentals of tooth movement remain the same. However, although the principles of physics may be immutable, definite progress has occurred in the area of material sciences. Indeed, development of new wires, brackets and springs has populated the orthodontic literature for the last 40 years. Even now, new brackets are being designed with the ambition of improving efficiency and esthetics. Clearly, treatment efficiency is one of the goals of every practitioner. Improved efficiency is accomplished by managing those aspects of orthodontics that are amenable to modification such as biology and mechanics. For example, many current appliances claim to reduce friction or “eliminate it” all together. These “frictionless” appliances purport no loss of the applied force and, therefore, greater predictability of the biomechanics. How this reduction in friction is accomplished, however, Surgically Enhancing Tooth Movement 324 has not been well substantiated. Moreover, based on the evidence, improved efficiency using these new appliances is controversial at the very least. Juxtaposed against the uncertainty of these new appliances’ benefits is a comprehensive understanding of bone biology in response to orthodontic tooth movement. Substantial research has been published in the area of biology of orthodontic tooth movement in animal models. It has become clear that bone biology can be modified in order to increase treatment efficiency. In the studies that have been performed primarily in animal models, the physiologic and biologic players have been well delineated. These models revealed that the presence of cytokines, such as RANKL, enhances the speed of orthodontic tooth movement. For many reasons, the clinical application of these biological substances in humans is unlikely to be adopted in the near future. Although injecting cytokines into humans may not be feasible, a more gross manipulation of the biological bone cascade – by means of segmental alveolar decortications – currently is becoming an attractive technique used to increase the efficiency of orthodontic tooth movement. The underlying theory with this method is that corticotomy surgery alters the bone biology through mechanical perturbation of the dentoalveolar complex. Further, this biologic agitation appears to enhance tooth movement resulting from the subsequent application of mechanical stimulus of an orthodontic force.