Why are there plastic blocks behind my two front teeth whilst i have braces and what do i do?

ive had top braces for nine month, and have just had bottom ones put on and have been given elastic bands as i am near the end of my treatment. but whilst having the bottom braces put on the orthodontist put two blocks behind my front teeth without telling me why. these blocks make sure only two of my teeth come together meaning i cannot chew my food up no matter how hard i try! what to i do? do i ask them to take them off as i cant eat? im near the end of my treatment so i want my teeth to be perfect and dont want to stop now but i have no idea what the blocks are for! please help me out!