Each scene in the graphics window provides access to the mesh representations that currently exist. To change the current representation, right-click on any portion of the display that isn't occupied by the model and select Apply Representation in the pull-down menu that appears. The currently available mesh representations will be listed.
Select the appropriate mesh representation from the list and the scene will be updated with the new mesh. You should note that any other scene displayer nodes belonging to the scene (e.g. Outline) will have the same representation selected for them automatically using this method.