Oracle Database Discussions

Hello.

I have several tables in my data base however 3 are important. One of them is Employee(Employee_ID, Name, Last_Name and other irrelevant columns), Dentist(Employee_ID, Qualifications) and Assistant(Employee_ID, Qualifications).
I'm making an application in Oracle Application Express and upon attempting to update a row in the Employee table I get a ORA-20505: Error in DML: p_rowid=96, p_alt_rowid=Employee_ID, p_rowid2=, p_alt_rowid2=. ORA-02292: integrity constraint (DB.Dentist_CON) violated - child record found

Now, to begin with I had the same problems with deleting rows but I solved that by adding an on cascade delete to my foreign keys.
I have foreign key constraints both in my Dentist and Assistant tables in the Employee_ID columns and these are referencing Employee_ID in the Employee table.

When I'm updating anything within my form in Application Express, I haven't allowed the users to do anything to the primary key (Employee_ID) from my Employee table. So any changes that might happen are to columns irrelevant to the primary key. For instance, if I change the Name column of a particular row I can't update because I get the above-mentioned error.

I don't understand why this is happening.
If I could have any insight into why this is happening or help of any form I'd greatly appreciate it.

Thanks in advance.