You might try a side exhaust regulator like the Oceanic Omega. I have jaw problems also stemming from an auto accident when a child.
Of course there is a solution and it is one of the reasons I dive the regulators I do--DOUBLE HOSE--regulators. Yep, the mouthpiece is virtually weightless and you do not clamp on it the way you have to with a hubcab in the face single hose. Then of course they are also so much quieter, smoother, no bubbles beating your ears or obscuring your vision and reliability is much higher and they are far more durable, alas, they pretty much quit making them 40 years ago with exception of Nemrod (1998) and the recent half **** attempt by AL called the new Mistral.
Side note, the small lightweight side breathers like the Tekna T2100 series (defunct) and the still produced Oceanic Omega are less stressful on the jaw and teeth than the hubcap in the face types--if you must use a single hose.
N