Another big aspect I rely on and love to utilize is the gums. Gums are great for giving a very real, tangible, finite look to the teeth, rather than have ...
I just feel like drawing a lotta teefies tonight but I haven't done digital in a few days so I'm RUSTY
And finally, wrinkles! Use the surrounding skin and flesh I to your advantage! Pull it for age and expression, compress it to show youth, (typically).
... of the time and it's a perfect chance to go in and fix the length of the upper/lower jaw before you start adding in deets like the tongue and teeth! <: