• It is the one in which the palatal aspect of an upper premolar or molar contacts the buccal aspect of the lower
antagonist.
• It generally affects only one tooth and can be caused by an eruption problem (a lingual deviation of the eruption
trajectory of the lower teeth or buccal of the upper teeth).
• It can also be caused by iatrogenic causes, like the excessive activation of an expansion appliance.
• When all the teeth are in scissor bite, it is generally caused by a retrognatic mandible and it is called Brodie
syndrome. This generates serious mandibular locking that causes traumatic micrognatia, because it impedes the
growth of the mandible.
Treatment: the correction of this type of cross bite can only be done if it is dentoalveolar in nature. Expanders with
inverse activation are used; buccal arches and sometimes crossed intermaxillary elastics are worn.