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Tooth Movement Of The Dental Arch

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The positioning of teeth in the dental arch is dependent upon an equilibrium that exists between soft tissues exteriorly and interiorly (dog article). It is the imbalance of the forces within this equilibrium that results in the movement of a tooth. Although extensively researched, there is still significant controversy as to the ‘ideal’ pressure that should be applied to a tooth to result in maximum efficiency in movement. A number of theories of the mechanics of tooth movement exist, revolving around the effect on the periodontal ligament and corresponding effect of alveolar bone remodeling. There are two main theories relating to orthodontic tooth movement, which are crucial to understand the assessment of the ‘ideal’ force for tooth movement. The bone-bending theory, otherwise referred to as the biological electric theory, proposes that forces applied to teeth stimulate electron release, which are then involved in remodeling alveolar bone. Possibly more accepted, however, is the pressure-tension theory. This theory suggests that forces applied to a tooth result in compression of the periodontal ligament on one side of the root, and a tension force applied to the other. Compression for an extended time, exceeding approximately four hours, results in a release of chemical mediators, including prostaglandins and cytokines, in addition to decreased oxygen associated with reduced blood flow. These mediators act to directly, and indirectly through secondary messengers

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