Cannoneer,
Next time you talk to your dentists, ask them for some source information. I literally can't locate a single reference dealing with thymol-resistant bacteria and I'd really like to read what they're reading.
As for the mechanism of resistance, once again I'm out of my league, but it's my layman's understanding that the mechanisms of action are completely different. There aren't that many antibiotics that actively poison bacteria --it's normally a case of interrupting some function of the bacteria's reproductive or metabolic process.
Thymol, alcohol, and other antibacterials, on the other hand, actively physically attack the bacteria, such as oxidizing it, rupture the cell wall, or introducing compounds that the bacteria otherwise finds toxic.
As I understand it, while bacteria can certainly become immune to an antibacterial, it's more difficult, and more uncommon, for that to happen.
I know that antibacterial soap has been under attack because it allegedly doesn't do much in the way of killing bacteria, and some are claiming that it's doing nothing but promoting the rise of triclosan-resistant bacteria, but as of yet I don't think that's been 100% proven.
Ah, interesting...
Something from researcher Dr. Stuard Levy, which I snagged from Wikipedia...
"However, Dr. Levy's most recent research (Aeillo, et al. (2005) Antibacterial cleaning products and bacterial resistance; Emerging Infectious Diseases) concludes that "The results from our study do not implicate the use of antibacterial cleaning and hygiene products as an influential factor in carriage of antimicrobial drug-resistant bacteria on the hands of household members." The paper's authors call for continued research in this area."
That was talking about antibacterial soaps, though...