There are two categories of attachments: metal ones and ceramic ones.

Metal brackets move teeth faster and more effectively; they are also capable of withstand greater forces without being harmed.

Ceramic brackets may look more aesthetically pleasing but they tend to determine increased friction (thus slowing down the speed of movements) and can in rare cases cause damage to the teeth: the American Association of Orthodontists recommended maximum attention in the use of ceramic brackets because numerous cases of tooth fractures are described during
their removal.

As a personal opinion, since the attacks are still visible, it is preferable use metal ones. For patients requiring aesthetic therapy, the technique lingual represents the solution to consider.