Self-corrective T-loop design for differential space closure.
ABSTRACT The current approach to measuring T-loop force systems in patients requiring differential anchorage does not consider active unit angulations and steps during space closure. The angulations and steps during movement introduced by rotation can considerably modify the force system acting on the teeth.
In this study, geometric modifications were determined during controlled tipping of the 6 anterior teeth, where there was no movement of the posterior teeth, thus configuring a type A anchorage situation.
An optimal beta-titanium alloy 0.017 x 0.025-in T-loop spring was designed by using a simulation performed with LOOP software (dHAL Orthodontic Software, Athens, Greece) to allow compensation for anterior unit-position effect on the final force system. The force systems produced by this T-loop spring with and without geometric correction of the brackets have significant differences that should be considered in the segmented arch approach to space closure.
The effects of steps, angles, and vertical forces were combined to produce an ideal T-loop design that would provide a more determinate force system. The effects and force systems are estimates based on simplified locations of the centers of resistance, assuming relatively constant behavior of the centers of rotation. These simplifications might differ slightly from what happens in vivo. The finite element method or an accurate spring tester capable of reproducing the geometric corrections should be used to ensure a precise force system.
Article: Rationale of the segmented arch.American Journal of Orthodontics 12/1962; 48:805-22.
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ABSTRACT: An incremental technique for predicting the nonlinear load-displacement characteristics of orthodontic appliances is developed. The analysis is based upon a three-dimensional finite-difference formulation which permits the treatment of appliances that have arbitrary configurations and non-uniform material and cross-sectional properties. The effects of intermediate loading and attached springs may also be studied.The results show the activated configurations and the associated force-couple systems for three appliances that are activated to the yield point. The incremental analysis results are compared to those of the linear solution for each case.Journal of Biomechanics 02/1976; 9(12):793-801. · 2.72 Impact Factor
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ABSTRACT: The location of the centers of resistance for various symmetric units of the anterior maxillary dentition for a lingually directed force was studied in two dry human skulls. The units investigated were composed of two incisors, four incisors, and six anterior teeth. In addition, the effect of change in force magnitude on the location of the centers of resistance of these units was investigated. The laser reflection technique was used to study both the direction and magnitude of the initial displacement of the consolidated teeth under loading. The results indicated that the center of resistance shifted apically with the incorporation of a greater number of teeth into an anterior segment. With a unit of six anterior teeth, the apical shift of the center of resistance was the greatest. Increasing force levels had little effect on the location of the center of resistance of a given unit. This phenomenon was observed in both the skulls tested, suggesting that general trends may exist in the displacement characteristics of the dentition when subject to controlled force systems.American Journal of Orthodontics and Dentofacial Orthopedics 06/1987; 91(5):375-84. · 1.46 Impact Factor