Abstract
This systematic review aims to highlight the differences between different clear aligner therapies that differ in the presence of attachments or in attachment configuration. Eight electronic databases were searched up to March 2020. Two authors independently proceeded to study selection, data extraction, and risk of bias assessment. The analysis of the results was carried out examining six groups of movements (mesio-distal tipping/bodily movement; anterior bucco-lingual tipping/root torque; posterior bucco-lingual tipping/expansion; intrusion; extrusion; rotation). Five clinical trials were selected and all of them showed a medium risk of bias. Literature showed that attachments mostly increase the effectiveness of orthodontic treatment with clear aligners, improving anterior root torque, rotation, and mesio-distal (M-D) movement; they are also important to increase posterior anchorage. However, some articles showed contradictory or not statistically significant results. Attachments also seem to improve intrusion, but the evidence about this movement, as well as extrusion, is lacking. No studies evaluated posterior bucco-lingual tipping/expansion. Further clinical trials are strongly suggested to clarify the influence of attachments and their number, size, shape, and position on each orthodontic movement.
Highlights
In the past decades, the demand of an aesthetic alternative to conventional fixed devices, especially by adult patients, has oriented the research toward the development of more comfortable and aesthetic appliances, leading to the development of clear aligner therapy [1,2,3,4]
Literature showed that the combination between disposition, shape, size, and number of attachments can greatly influence the efficacy of orthodontic treatment [4,16]
A better understanding of forces and moments generated by different attachments and the knowledge of biomechanics principles are essential in order to select proper attachments and, to improve efficacy and efficiency of orthodontic treatment
Summary
The demand of an aesthetic alternative to conventional fixed devices, especially by adult patients, has oriented the research toward the development of more comfortable and aesthetic appliances, leading to the development of clear aligner therapy [1,2,3,4]. Attachments are a protrusion of composite material polymerized onto tooth surface, applied in order to improve aligner retention and to obtain orthodontic movements previously considered critical to achieve They are able to reach these goals through an enhancement of the mismatch in specific points, an improvement of the contact area, and a better force system application. Literature showed that the combination between disposition, shape, size, and number of attachments can greatly influence the efficacy of orthodontic treatment [4,16] In this context, a better understanding of forces and moments generated by different attachments and the knowledge of biomechanics principles are essential in order to select proper attachments and, to improve efficacy and efficiency of orthodontic treatment. The aim of this systematic review is to highlight the differences between orthodontic cases treated with and without attachments and to clarify what is the best shape, size, number, and position of attachments for each specific orthodontic movement
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