PubMed · 1783730
Posts retain cores when tooth structure is lost. Many posts are on the market, but root structure is the best guide to post selection.
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F H Kahn. 1991. Selecting a post system.. https://doi.org/10.14219/jada.archive.1991.0203
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The effect of off-center positioning on the force system produced by segmented 0.017 x 0.025-inch TMA T-loops was measured. A T-loop was designed to produce equal and opposite moments in the centered position. The spring was tested in seven positions, centered, 1, 2, and 3 mm toward the anterior attachment, and 1, 2, and 3 mm toward the posterior attachments. The horizontal force, vertical force, and alpha and beta moments were measured over 6 mm of spring activation. The results showed that the alpha/beta moment ratio was dependent only on the spring position, and independent of spring activation. Eccentric positioning of T-loop springs effectively produces a consistent moment differential through the range of spring activation.
The authors outline four principles that should be considered when planning orthodontic tooth movement. They suggest that dentists have clear treatment objectives, know the force requirements to achieve those objectives, choose the best equipment to provide the needed forces and prevent unwanted tooth movement during treatment. To illustrate use of these principles, the authors refer to a sample treatment scenario. They also provide a mnemonic device to help dentists recall these principles.
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