I'm wondering what is a coffin spring expander in orthodontics. how long does it take for treatment?

Removable: A removable appliance with an expansion spring designed to widen upper posterior teeth. It works by tipping teeth outward, which in turn can create problems in the way back teeth meet. It is not very effective at widening the upper jaw itself. Talk to your orthodontic specialist about pros and cons.

Increases arch width: A removable device to widen the arch with a continuous force spring developed by walter coffin in the late 1880's. The problem with all expanders is they do nothing permanent to the bottom teeth as they have been shown to produce unstable results. Also, the most space that can be created by maxillary expansion is only 4mm. Stability, bone loss, and facial balance all suffer with expansion.

Coffin spring expand: Separation of the mid palatal suture done with the coffin expander for the expansion of the maxillary arch. It is used to treat posterior cross bites. It is an outdated technique.