CATEGORY 56 AUSTRALASIAN DENTIST LINICAL Dr Geoff Hall By Dr Geoffrey Hall Part 5 The A-Z of aligner attachments – what to use, when and why Orthodontic principles of force application, engagement, anchorage and biomechanics need to be applied. However, aligners move teeth differently than fixed appliances do. Aligners move teeth by exerting a push force. Aligners engage teeth by enclosing the tooth in aligner material. The more material wrapped around a tooth, the better the engagement. Limitations exist for aligner system, such as corrections involving complex force systems. Composite attachments on the tooth surface are intended to enable active control of tooth movements. Gentle, constant forces improve control of tooth movements throughout treatment, properly eliciting a more predictable biological response from the periodontal tissues and supporting structures. Several studies have investigated the effect of the shape and positioning these attachments to have on tooth movement. Evolution of attachments The goal is to provide a ledge for the aligner to grip that is perpendicular to the direction of displacement and of sufficient size to provide enough surface area to offset the force delivered. Classification They can be classified as u Optimized Attachments u Conventional Attachments responsible for moving each individual tooth to the desired position using the software. u The toothmovements prescribed by the orthodontist are measured in all three planes of space; when a default in any one direction is exceeded, the software will place the optimized attachment on the tooth automatically at the correct location to create the required force system to cause the tooth to move as desired. Rule of thumb is toplace the attachment far enough away from the gingival margin that the aligner will not spread or stretch and slip off the attachment. This concept is important because the aligners tend to relax over time; that is, they exert less force. The clinically observed side effect is that the gingival third tends to become less retentive. Further these attachments having varying shape, size and aligner geometries based on the desired tooth movement. Shape of attachment can affect the intensity and direction of force. Optimized attachments Optimized attachments provide an active, flat surface that thealignermaypushagainst to provide effective tooth movements. These are features designed to direct and deliver the appropriate biomechanical forces needed for enhanced predictability of orthodontic tooth movement. u Each optimized attachment is custom designed for a specific movement on a specific tooth for an individual patient. u They are automatically generated by the software. The orthodontist is Conventional Attachments Conventional attachments are the second type of attachments. Conventional attachments can be ovoid, rectangular, beveled or non-beveled, and oriented horizontally or vertically. They are used for the following: aligner retention and anchorage, to support intrusion, extrusion or root control. Conventional attachments can be requested or the clinician can place by themselves using 3D controls. The first of the manually placed attachments was the ellipsoid attachment. This attachment is widely considered the
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