Now I am thinking of a very clear case of the cheek/jaw movement mentioned by the OP, and I am really curious why I don't see this with people who snort C-Jam or use it to make a cigarette or joint into a Primo or Flamethrower, or smoke White Tornado, the original method of freebasing Bolivian Marching Powder . . .
I didn't really have information or experience with the crack smokers in question to follow an analysis to the conclusion that they were lying about anything . . . in fact they were not saying much of anything and the jaw movement seemed like a baroque version of how people and animals lick their lips when drinking something tasty . . . cats do it all the time, a story about etonitazene mentions lab animals doing it, I hear it a lot when we experiment with stirring Bolivian Marching Powder into Coca-Cola to bring back the original glory . . . just last night I saw a raccoon doing it after draining a bottle of rum and licking all around the opening to get every last drip-drop . . . of course the comment "Mmm, that was some great crack" was unlikely to be a lie . . .
There is the thread above about thirst caused by stimulants and it looks like the two things are for totally different reasons, though if one has a dry mouth and drinks lots of sugary beverages because they are thirsty, it can make cavities and other similar trouble more likely . . .
Sooo, what stimulants can do to one's teeth appears to be as follows:
In general, if one is grinding their teeth for these reasons, there is the possibility that they are getting in more hours of tooth grinding as they sleep, and lots of folks actually grind their teeth in their sleep and have no idea that they do it . . .
It sounds like bruxism does happen with C-Jam in its various forms but it seems to be a speed thing in particular, including E and other amphetamine variants . . . MPDV is related to both the pharmaceutical Thymergix and Cat, green and otherwise, and those seem to cause it to the same extent as E .. . there is the contribution bruxism can make to Meth Mouth, which arises from a number of things -- it can be unreacted precursors, there is the dryness combined with thirst and wanting sugary drinks, some people apparently like to chew on the pipe and other objects even when not in use . . . The people I know who use pseudoephedrine and ephedrine with caffeine and antacids as stimulants have had trouble with bruxism and I know a couple of MDA fanciers who wear mouth guards to prevent tooth damage . . .. the same folks are of the opinion that, at least bruxism-wise, 2C-B is another kettle of fish entirely . . . Benzamphetamine, methylphenidate, phenmetrazine and phendimetrazine are typical stimulants of this type but I took most of those at one point or another and don't recall a lot of tooth grinding . . . it has actually been MDMA and some things like MMDA, MDEA, STP and so forth that seem to have a lot of folks using pacifiers and mouth guards; there is a dentist I know of who is hip to all of this kind of thing who does work with harm reduction folks to get this news out because over not that long of a time it can do all manner of damage to teeth .. .
Nicotine's central neuroendocrine actions will actually counter any anticholinergic effects which cause dry mouth, there are jaw, tooth, mouth, gum, and other problems with chewing tobacco and other forms like smoking have effects on the teeth and gums which are often discussed . . . reportedly nicotine gum can apparently damage the teeth if it is used heavily over years and one does not closely monitor the situation, though I have never heard an actual reason suggested for this aside from one theory about the abrasiveness of the gum, which was hard to determine if it was or wasn't . . . I have not heard this said about tablets of nicotine.
Other drugs which impact the same systems may or may not cause the same effects . . . I have not heard of it with tramadol or tapentadol, nor lefetamine (Santenol) for that matter . . . the first-generation anti-depressants do not list it as an adverse effect, nor do the second-generation ones, although I do know a doctor who says her patients who take Cymbalta as a narcotic potentiator should keep up with their dentist and make sure there is no evidence of bruxism, especially whilst sleeping. Imipramine was being taken by one person who said she grinds her teeth a lot and there was an increase, but she said it was probably impossible to name one factor or another as there were several medications she took and some possibility she unconsciously grinds her teeth anyways . . .
Dry mouth from any number of drugs can cause problems with teeth, of course . . . I do know of someone who was very vigilant about it but still lost some teeth from years of being on Vicoprofen, Norflex, Ornade, No-Doz, and Naproxen, which was also one of my early protocols for pain too and it was a great 360° medication combination which made me feel like Jesus' interpreter and accountant and made me into a bit of a horndog so that was my lunch at 14.30 every day for a number of years, and then at night I would add cyclobenzaprine and hydroxyzine to it and carisoprodol if needed . . . back in the day Ornade had phenylpropanolamine in it, which counts as the sympathomimetic stimulant in this case . . . I knew what may be coming so I carried a little of every product Biotène makes . . . I am not a gum chewer at all, but the gum did help in some cases and of course it was medicine . . .