i asked in another way before but because i'm not sure, i try another approach.(http://drupal.org/node/1285114)

is it possible to change the format of an entity?
basicly i want to achive that a node is rendered with different formats in full and teaser mode. eg full_html in full mode and filtered_html in teaser mode.

i found a hook to change the settings of the formatter but this doesnt help to change the format.

could you please push me into the right direction
peter