Joining 90 DEgree partical board kitchen tops

I have to take part of my kitchen apart to put a new single sink in, so I could fit a dishwasher next to it. In doing so I have had to take off the counter top which was originally connected using 2 screw bars. I think it might have been glued too. Do I need to glue it as well as use the compression bars? If so, what glue would be best and at what point would I glue it? - Thanks :)