CATEGORY 58 AUSTRALASIAN DENTIST LINICAL An important aspect of controlling tooth movement with aligners is staging. Staging is the sequence in which and the speed at which teeth are moved with aligners. Biomechanics for an ideal aligner staging Biomechanically, aligners produce a pushing force from the plastic to the tooth surfaces or attachments. Tooth movement mechanism with clear aligners can be explained from two different perspectives: the displacement driven system and the force driven system. u Displacement driven system (also called Shape driven system), where the shape of the plastic aligner is changed incrementally into each upcoming stage of tooth alignment to move each tooth into the designated position. Each tooth is moved based on the plastic aligner’s shape. This system can only control simple movements, such as tipping or slight rotation. Therefore, the system is known to be less effective in controlling tooth movement and is insufficient in producing root movements. u Force driven system requires biomechanical principles to facilitate tooth movement. Here the aligner’s plastic is shaped using digital treatment plan software in which the clinician can set the parameters of tooth movement by the aligner combined with other attachments to apply force to the tooth. This system allows for more complicated movement such as root movement. The shape of aligners to produce such forces is not necessarily the same as the shape of the tooth. Often, that final shape of orthodontic appliance based on forcedriven concept would not be identical to the ideal finishmodel.Therefore, the virtual models partly do not accurately reflect the Dr Geoff Hall By Dr Geoffrey Hall Part 6 How to stage treatment with Aligner Therapy to provide maximum orthodontic outcomes Displacement Driven System – Tooth displacement as changing of aligners shape Force Driven System – Movement from force application Force Driven System vs Displacement Driven System patient’s final occlusion, at the end of active treatment. Parameters that influence the biomechanical characteristics of aligners include the properties of the material, the thickness of the material and the fitting accuracy of the aligner to the teeth and any attachments. Clear aligners are made in a series which relies on the progressive alteration of biomechanics using one aligner material. The engineered designed materials in controlling tooth movement with various approaches; such as altering the shape of the aligner, applying attachments to modify the shape of the tooth, and the movement of the tooth is programmed sequentially (movement staging). Staging Staging is available to the clinician in the virtual set-up after the tooth movements are programmed by the 3D proprietary software. The numbers across the top represent the aligner number, and the vertical axis represents tooth number. The difference is that the staging diagram is available to the clinician as horizontal bars that indicate the timing and rate of tooth movement. Each aligner number then represents one stage.
RkJQdWJsaXNoZXIy MTc3NDk3Mw==