[TYPO3-mvc] 1:n childs unconected but not deleted from database

[christian oettinger]

Hi list,

we have a big object with 1:n related childs. We divide the 
creation/editing of the object in multiple forms (multi-step, we thus 
use partial Validation) containing fields of the parent(s) and childs.

Example of one Form:
Patient (parent) Fields: Name, Age, Sex
Medcation1 (child): Name, Dose
Medication2 (child): Name, Dose
Maedication3 (child): Name, Dose

When sending the Form we manipulate the request - if all fields of a 
child are empty we delete the child form the request, so it will not be 
validated nore persisted.

Everything works fine so far. Now to the question:

When deleting all fields of a child that has already been persisted 
previously, the child will be removed from the object as intended - but 
the now useless child data will remain in the database, unconnected.
It will not be deleted when there is no deleted-field.
If there is a deleted-field, it will not be set.

Is there a way to change this?
Or am I missing something?
We are using extbase 1.2.1

Thanks for any hint!
christian (oe)