Why do we need attachments?
Aligners work through pushing mechanics, therefore, bonded resin attachments on teeth are introduced. Some even described attachment as brackets in fixed appliance therapy while the plastic resembles arch-wires.
Types of attachments
· Conventional attachments which can be customised in their bevel, height and depth. There are available in different shape and form such as: ellipsoid (mainly for retention), vertical rectangular attachments (for root control) or horizontal rectangular attachments.
· Optimised attachments (Invislaign) in which the sizes and shapes are specific to each tooth and to each case.
Factors that might affect performance of attachments
· Type, design, size and orientation of the attachments (optimized or conventional, beveled or unbeveled, wide or narrow, occlusal or gingival, etc)
· Numbers of attachments: Momtaz et al. in 2017 found that multiple attachments for rotational correction impede rotational correction.
· Position of attachments taking in consideration the aesthetic impact: Thai et al in 2020, using eye tracking technique, compared photos of patients without attachments, with anterior and/ or posterior attachments. They found that lay people noticed attachments and had a preference for ceramic brackets)
· Materials used to make the attachments
Ideal properties for attachment materials
· High wear resistance
· Low shrinkage properties and volumetric change
· Short operation or char side time
· High shear bond strength
· High colour stability
· Ease of removal and handing
Several options are available:
1. Some use conventional flowable or bulk composite
2. Tetric EvoCeram Bulk
3. Tetric EvoFlow
4. Brace-paste (I personally use it as it is easy to clean the access under blue light, see the video)
5. Filtek Z350XT Fill
6. Filtek Z350XT Flowable
7. Amelogen Plus TW
Mantovani et al. in 2019 concluded that materials No. 2 is better than No. 3. Another study by Barreda et al. in 2017 concluded that materials No.5 and 6 is better than No.7. However, we do not know what is the effectiveness of SonicFill.
Orthodontic and Craniofacial Research Journal in their January 2021 issue published an in vitro study to answer the raised uncertainty.
The paper is titled “Comparative Study of three composite Materials in bonding Attachments for clear aligners”.
The study was undertaken by a team from China led by Dr Chen. The study compared three different attachments materials (Filtek Z350XT Fill, Filtek Z350XT Flowable and SonicFill).
· Filtek Z350XT Flowable have shorter operation time but high volumetric change and deviation and high wear volume loss.
· On the other hand, SonicFill has shorter operation time, low volumetric change and deviation and low wear volume loss.
· The properties of Z350XT Fill is superior to that of Z350XT flow but inferior to SonicFill
What do you think?
Link to the paper:
PS: I have no financial interest and I use aligners for mild cases only.