It sounds as though you have put your finger on the situation: your son is very oral. Chances are, he will always be more oral than other people. (I am a very oral person, so I know how to recognize the signs even over the internet. The instant I stop typing and have to think about what I am writing, one hand goes to my mouth and rests against my lips. For the most part, I am ordinarily unaware that I do that, but I suddenly noticed it and laughed as I was writing to you.)
Some people would say you did not give him an opportunity to take care of the strong sucking drive all children have. But that doesn’t really matter now, does it? I think you need to try to gratify it in every way possible—every way that you consider acceptable, that is. Can he handle chewing gum? (With some 5-year-olds, there is still a danger of having it lodge in the windpipe.) Check with your pediatrician. If he can handle gum, I’d buy a supply of sugarless and let him chew it as much as possible. (They may not allow it in school.) Certainly, I would give him a piece when he sits down to watch television. And try to find and interest him in as many “oral” toys as you can—some simple musical toy like an ocarina, balloon sculpture, and others. And be patient; it won’t go away overnight.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.