CATEGORY 44 AUSTRALASIAN DENTIST LINICAL teeth. Clinicians can request or make modifications to the amount and direction of desired tooth movement in all three planes of space. But once the aligners are made, they cannot alter the appliance during the treatment. With the help of 3D software, the virtual set-up is used to evaluate the need for IPR, extraction, expansion, distalization, proclination and other tooth movements in sequence. It also shows treatment limits to patient as it evaluates the anchorage with superimposition (White – initial tooth position, Blue – final tooth position) or surgical simulation tools. is worn for approximately 20/22 hours per day and is changed approximately every two weeks (depending on the severity of the case). Each aligner will move the teeth around 0.25 to 0.3 mm Some products are available to the clinician to manufacture in-house via 3D printing, while others are made and shipped from a central laboratory which then manufactures the appliance via the use of 3D scanning technology. The more accurate the model on which the clear aligners are to be made, the more precise are the subsequent tooth movements. Factors clinicians should use to assess aligner system u Aligners can be made using a stone model, an impression or an intraoral scan. Intraoral scans are the most accurate for aligner manufacture and fit. u The aligner can be made manipulated by hand in a laboratory or via CAD- CAM software. Hand manipulation clearly offers much less precision, especially for small incremental movements necessary with current aligner materials. u Aligners can be manufactured using vacuum- or pressure- forming. Higher pressures tend to equate with improved force generation and higher precision, improved ability to grip and generate forces toa toothor attachment surface is dependent upon air pressure. Pressureforming is generally associated with superior aligner fit. u The clinician should have access to a three-dimensional model of the treated case for confirmation of the accuracy of the data and the proposed treatment plan, modification of the proposed treatment plan, and final approval of data and plan prior to manufacture. u The more sophisticated the range of the available aligner auxiliaries, the more complex the movement that can be treated with confidence. Therefore, the aligner product using integrated bonded attachments, specific aligner geometry alterations (pressure points, power ridges, bite ramps, elastic cutouts etc) are better. u Gingival coverage is important to improve aligner retention in the absence of tooth-borne attachments, but is potentially less hygienic and requires greater impression/scan detail. Variable material stiffness or thickness also play a role in tooth movement. u The bigger the amount of teeth and extension of movement to be performed are, the bigger the quantity of successive aligners and the estimated total treatment time will be. u The movement threshold reflects Grid helps in measuring the amount of tooth movement set-up virtually. Tooth movement table also helps in analysing the movements generated by the software. The crown and root movement can be analysed for each tooth. The complex movements can be identified via the table and can be staged accordingly within the limits of per aligner movement. Virtual set-up also aids in planning for over-correction aligners or movements which require refinements later. Occlusal contacts play an important role for treatment stability and overall outcome of the occlusion. Green contacts denote normal occlusal contacts between upper and lower teeth. Red denotes heavy occlusal contacts which in case of deep bite correction requires posterior extrusion and overcorrection. In case of open bite in the anterior region, heavy occlusal contacts can be simulated in the incisors. A series of clear aligners suitable for the treatment period is designed. At this stage, it is recommended that the tooth rotation is within 2.5 degrees and the movement distance confined to each teeth in increments of about 0.15 – 0.30 mm at each stage. Next, a 3D printer is used to make a model for step-by-step changes and then make a series of progressive clear aligners to move the misaligned teeth. Aligner fabrication and delivery This information can then be used to produce a series of clear plastic aligners that gradually correct the malocclusion towards the clinician’s goal. Such aligner
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