The clinical evaluation of a novel cyclical force generating device in orthodontics

The purpose of this study was to determine the clinical effects of a cyclical force generating device on tooth movement and overall orthodontic treatment time. In addition, the levels of patient compliance and patient satisfaction were evaluated. Patients who were undergoing active orthodontic treatment with fixed appliances, with no previous history of orthodontic treatment, were invited to participate in this study. The subjects were instructed to use the device for 20 minutes daily for a period of 6 consecutive months. Rates of tooth movement, patient compliance, and patient perception data were evaluated. Fourteen patients completed the study. The total rate of movement for the mandibular arch was 0.526 mm per week or 2.1 mm per 28-day month; the total rate of movement for the maxillary arch was 0.759 mm per week or 3.0 mm per 28-day month. There was a statistically significant difference between the rates of movement in the maxillary arch compared with the mandibular arch (p > 0.05). The patient compliance rate as measured by data recorded from the devices by the study engineer indicated a 67% compliance rate. Overall patient satisfaction with the device increased over the course of treatment time for most variables as indicated by the mean scores. Paired t-test value indicated that there was a statistically significant change in overall satisfaction for all variables measured with the exception of drooling and noise. It was concluded that the rates of movement of teeth during orthodontic treatment were increased with the use of the device; patient compliance with use of device was 67%; and patient acceptance of and compliance with the device was clinically significant. The most common treatment approach to correcting dental malocclusion is through the use of static mechanical forces, which traditionally involves an appliance system of metal arch wires and brackets. Static mechanical forces in orthodontic treatments move teeth within the jaw bone and rely on force-induced remodeling to elicit tooth movement. The traditional fixed-force system is augmented with elastics, metal bands, head gear, expansion appliances, and other ancillary devices as determined by the clinician. These forces are static in that they are, for the most part, applied only at specific treatment intervals by the clinician, but then subsequently stay constant and are not altered between visits. Bone is a flexible tissue, and application of steady pressure to the teeth (static force) through the use of orthodontic arch wires permits teeth to be systemically moved into the new positions through this compliant medium. When a force is exerted on a tooth in a specific direction, the altered state of the periodontal ligaments (PDLs) behind the tooth results in bone resorption via osteoclastic activity. New bone forms in the area of increased PDL tension due to stimulation of osteoblastic activity. The direction of movement of the tooth is influenced by polarity created by the point of application of the mechanical forces. Mechanical pressure to the tooth induces an electropositive state, whereas the resultant tension to the PDLs induces an electronegative state. When the tooth is under tension and increased in convexity, the area is in an electronegative state. This is associated with osteoblastic activity of bone deposition. Cells respond to mechanical stress to the tooth and its periodontal tissue, or PDL. The periodontal tissue is a connective tissue attaching the tooth to the alveolar bone. This tissue withstands the compressive forces during mastication while stabilizing the tooth. In addition, tooth movement invokes an inflammatory process, and cytokines, such as interleukin-1 (IL-1), IL-6, and receptor activator for nuclear factor κ B ligand (RANKL) are inflammatory mediators or pro-inflammatory remodelers of the PDL. RANKL is reportedly essential to the osteoclast formation, function, and survival. Until recently, all studies relating to the use of vibratory or cyclical forces during orthodontic treatment have been tested on rats. However, many investigators question the validity of extrapolating animal experimental findings to the human condition. For example, the alveolar bone of rats has been shown to be significantly denser than the alveolar bone in humans. In addition, the osteoid tissue along the alveolar bone is less abundant in rats than in humans, demonstrating reduced formation of osteoblasts. Small amounts of acid mucopolysaccharides are found on the extracellular matrix of rat bone, and calcium balance is controlled by intestinal absorption rather than bone tissue. Moreover, studies have also identified structural dissimilarities in the periodontal tissue. Finally, rats develop tissue during root formation during the application of orthodontic forces much faster than humans, although the mechanisms of formation are the same. This clinical study represents the first attempt to use a cyclical force generating device on human subjects to determine its impact on the rate of tooth movement during traditional orthodontic treatment. The purpose of this study was to measure clinically the effect of the device on orthodontic treatment time, and in addition, to evaluate patient compliance and acceptance of this adjunctive treatment.