Clear aligners can be described as one of the most aesthetic orthodontic appliances to achieve both aesthetics and function in individuals with malaligned or maloccluded teeth. To obtain the best clinical outcomes with clear aligners, the clinician should have optimum experience and a considerable understanding of the biomechanics of tooth movement with clear aligners.
One of the primary concepts to be understood in clear aligners is that they do not work by pulling the teeth to the final positions as they are removable. On being placed, they apply a pushing force on the surfaces of teeth directly or through attachments placed. Tooth movement brought about by aligners also depends on the size and the shape of the teeth as they fail to produce the desired result on a tooth with a small crown or small surface area to push against.
There are different types of tooth movements in orthodontics like crown tipping, root movement, and translation. The bodily movement of the tooth in which both the crown and root of the tooth move in the same direction, it is referred to as translation. Torquing of the tooth is when the tooth rotates along the center of the tooth when force is applied to the root in one direction and the clinical crown in the opposite direction. Attachments and power ridges may help in various tooth movements using clear aligners.
Attachments can be passive or active. Passive attachments aim at delivering retention to the aligners whereas active attachments bring about the actual tooth movement. Active attachments are customized to bring about the closure of extraction space, extrusion, and de-rotation. Bevelling of attachments can be done to promote ease of insertion of the aligners and aid in the biomechanical delivery. The shape of the attachment and their position varies from case to case and clinicians should have excellent knowledge and understanding regarding the situations in which each type of attachment can and should be used. For instance, a horizontal attachment is placed on the tooth to be extruded whereas, in case of intrusion, horizontal attachments are placed on the teeth neighboring to the tooth to be intruded, to augment anchorage and retention of the appliance
Power ridges are meant for lingual root torque in the upper and the lower incisors. These corrugations are positioned at the gingival third of the tooth and are aimed at increasing the undercut on the teeth. Power ridges help in stiffening the gingival third region of the aligners and also help in applying pressure on the roots of the teeth.
To conclude, deeper knowledge and genuine practical experience can deliver the best results. The wise use of attachments and power ridges can help patients achieve the desired smile.
The correct plan requires extensive knowledge of aligner biomechanics, the correct staging of movements, the type, position and size of the attachment for various movements, the overcorrections required for different objectives and a realistic understanding of movements that can be achieved. This requires excellent knowledge as a result of loads of training and learning.