The Angle orthodontist · 2026
Biomechanics of molar rotation with the transpalatal arch: applicability of Burstone's six geometries.
СтатьяНазвание и аннотация: Перевод в очереди
Обработка статьи · этапы, ошибки и управление
Загрузка состояния…
Ошибки и ограничения
История · было → стало
Состояние обновляется каждые 5 секунд, пока блок открыт. Процент показывается только там, где известен объём работы. Пауза останавливает продолжение этапа; текущий запрос к источнику может завершиться.
Fiorelli Giorgio
Аннотация
OBJECTIVES: To reevaluate transpalatal arch (TPA) biomechanics for molar rotation by transitioning from the traditional linear beam model to a statically indeterminate elastic portal frame analysis.
MATERIALS AND METHODS: A mathematical model based on Castigliano's second theorem simulated the TPA as a curved portal frame. Different modes of rotational activation were applied to standard and omega-loop designs across variable palatal heights (10 mm to 18 mm) using stainless steel and beta-titanium, incorporating a 2° mechanical clearance to simulate clinical insertion conditions.
RESULTS: Palatal height was the primary determinant of TPA stiffness, acting as a lever arm that converts sagittal forces into torsion. In unilateral activation, average to high palatal vaults (palatal height ≥ 14 mm) generated spontaneous neutrality through the interaction between structural compliance and mechanical clearance, where the moment on the nonactivated side dissipates entirely. Regarding stiffness, contrary to clinical assumptions, the omega loop provided modest additional flexibility (less than 5% for unilateral activation, up to 15% for symmetric activation).
CONCLUSIONS: The TPA functions as a flexible elastic frame, not a rigid linear beam. Vertical legs significantly dampen the force system, rendering the omega loop mechanically redundant. Notably, compensatory bends, generally used for unilateral rotation activation, are often biomechanically unnecessary in high-vaulted patients, as the system naturally reduces the contralateral moment to zero within the mechanical tolerance of the attachment.
MATERIALS AND METHODS: A mathematical model based on Castigliano's second theorem simulated the TPA as a curved portal frame. Different modes of rotational activation were applied to standard and omega-loop designs across variable palatal heights (10 mm to 18 mm) using stainless steel and beta-titanium, incorporating a 2° mechanical clearance to simulate clinical insertion conditions.
RESULTS: Palatal height was the primary determinant of TPA stiffness, acting as a lever arm that converts sagittal forces into torsion. In unilateral activation, average to high palatal vaults (palatal height ≥ 14 mm) generated spontaneous neutrality through the interaction between structural compliance and mechanical clearance, where the moment on the nonactivated side dissipates entirely. Regarding stiffness, contrary to clinical assumptions, the omega loop provided modest additional flexibility (less than 5% for unilateral activation, up to 15% for symmetric activation).
CONCLUSIONS: The TPA functions as a flexible elastic frame, not a rigid linear beam. Vertical legs significantly dampen the force system, rendering the omega loop mechanically redundant. Notably, compensatory bends, generally used for unilateral rotation activation, are often biomechanically unnecessary in high-vaulted patients, as the system naturally reduces the contralateral moment to zero within the mechanical tolerance of the attachment.