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Distinguishing Between Optimized and Traditional Attachments for Clear Aligners

Updated: Mar 4

Attachments are not always a requisite element in the process of moving teeth using clear aligners, but they are most often employed to augment their efficiency and predictability.


Specifically, Invisalign's optimized attachments are touted for their ability to offer precise biomechanical forces, thereby facilitating desired tooth adjustments. However, the application of optimized attachments hinges on individualized treatment plans and the specific needs of each patient. Just like the conventional attachments. Notably, some studies have failed to establish statistically significant disparities in tooth movements when comparing Invisalign's optimized attachments with conventional ones.


Invisalign Clincheck  visualisation of the placement of attachments, cutouts, IPR and power ridges

In a recent retrospective study conducted by Karras et al. as part of a master thesis at the Marquette University, the focus was on examining the variances between optimized attachments and their conventional counterparts concerning two types of tooth movements: canine and premolar rotation, as well as incisor and canine extrusion. These movements were selected because they are commonly regarded as the most challenging to achieve accurately with aligners.


The study was conducted on 3D printet models retrieved from Invisalign STL files from 100 patients treated in two different orthodontic practices.


Optimized and Traditional Attachments for Clear Aligners - what works best?

Upon close scrutiny of the study, it becomes apparent that there was no statistically significant distinctions identified.

Many of the conventional rotation attachments used were rectangular and measured 3 mm in length, typically larger than their optimized counterparts. A larger attachment area allows for greater contact with the aligner, potentially enhancing effectiveness. Consequently, some orthodontists may still prefer optimized attachments due to their potentially high precision and smaller size. As the smaller size speaks more to the desires of the aesthetically conscious patients.


It's worth noting, though, that despite the larger dimensions of conventional attachments, the study did not ascertain a statistically significant accuracy gap compared to the smaller optimized attachments. Hence, attachment size, while potentially influential, does not appear to be the sole determinant of attachment efficacy.


The study also underscores various factors that can impact the predictability of tooth movements with aligners. These encompass aspects like the location, size, orientation, and beveling of conventional attachments, as well as the potential influence of minor simultaneous movements in different spatial planes.


Additionally, anatomical tooth characteristics and sizes, variables like periodontal support, attachment features, concurrent tooth movements, and patient compliance, along with considerations regarding tooth mobility, altered periodontal support, and overall periodontal health, all exhibit variations from one patient to another.


Furthermore, most clear aligner systems, including Invisalign, do not incorporate a tooth's root length, angulation, or center of resistance when devising movement strategies.


Increase your clinical confidence with complimentary case selection and expert treatment planning support. This way the ideal placement and types of attachments becomes easy. Within 24 hours an expert dentist will send you an indexation of whether your case i easy, moderate, complex or should be referred to an orthodontist. Try it out today - click the button and follow the instructions.




In addition it is worth noting, that the teeth selected for this study preferably had no other planned movements than the once used in the study. In most patients there will be more planned movements during a treatment than just rotation or extrusion. This in turn will affect the choice of attachment as optimized attachments typically will only be useful for one type of movement. Regarding this choosing a convetional attachment will often simplify both the treatment planning and the clinical handling.


In summary, when devising clear aligner treatments, it is imperative to take these multifaceted factors into account to enhance treatment outcome predictability. A deeper understanding of these variables empowers practitioners to effectively manage individual cases and address challenges that may arise during the treatment process.


Reference: "Efficacy of Invisalign attachments: A retrospective study" by Karras T et al., published in the American Journal of Orthodontics and Dentofacial Orthopedics in 2021 (Volume 160, pages 250-8).


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dentist and clear aligner expert Jesper Hatt

Kind regards

Jesper Hatt DDS



Phone: +41 78 268 0078



AlignerService helps dentists create realistic, safe and predictable treatment plans with clear aligners.

Currently, we help approximately 1500 dental practices in 16 different countries.

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