Hello i have a question about my cat?

When he gives me head bumps i offer him a fist to bump into (in a nice way ^_^) and some times he choses to place one of my nuckles on the side of his mouth (near his gums i think)... and then he begins to make a munching motion and sounds to match. Like nom nom nom nom... sounds like my wife with her night time retainer on trying to say she sells sea shells by the sea shore. Im thinking he reallly likes me or he's using me to clean his teeth and or his gums are itchy? He seems to only do it on one side once in a while not even the same side all the time haha. please only reply if you have some first hand experience or some real knowledge. thanks in advance :]