How to clear items / cache in Apex 4.2

Question

Can someone explain how clearing cache or session state processes are supposed to work in Apex 4.2?
I have an application that allows the user to look up records by last name or by social security number
A look up by SSN is one to one and takes the user to a detail page
A look up by NAME displays a list of names where the user can select a user and display the same detail page
The problem is that the application retains the social security number from one look up to the next. So it keeps displaying the same record
even if you enter or select a different SSN.
I've tried creating session state processes to either clear specific items or clear the cache on a page, but nothing seems to work.
Maybe the problem is that I'm not understanding the options for creating these; it says things like  on load before headers, on load after headers, on submit before calculations, after calculations, etc
The application is read only.  Logically to me, if you are linking from one page to another you need to save the value in the item  but if you are doing a  new search you need to clear it
So I thought that on the detail page I should clear the items, or clear the cache on the page after submitting
But can't get this to work

Answer 1

heres an example
Page 1 has items P1_SSN and P1_NAME  as well as hidden items P1_TEXT and P1_TEXT2
The button affiliated with p1_NAME takes the user to page 2 that displaces a list of match names. it has a link which goes to page 3 where P3_SSN matches #SSN#
The button affiliated with p1_SSN takes the user directly to page 3 where p3_SSN matches #SSN#
If I log in and search by SSN first, when I get to page 3 I have the correct record
If I look up by name , I get the list and select a record by SSN I still have the correct record
then I go back to Page 1 and search by SSN, entering a new SSN. I always get what ever record I previously pulled up when searching by name and selecting from the list
On Page 1 , I have a process that says on load before regions clear items and I list all the items
Similarly  on page 3 I have a process after submit and calculations that clears the items
When creating these processes it asks to list the items, separated by comma. The only place to enter PL/SQL is under conditions, this is not conditional on anything, it should always clear the cache.
I use this same logic on different pages in the same application - different tables but same flow. It works there. I don't see why it doesn't work here