I think the invention of the SonicCare style toothbrush is what really put the dentists under pressure. Cavities dropped and they lost one of their main money makers. It's after that when I really started noticing car salesman like tactics for extra services.
Indeed. There's also bioglass compounds like Novamin, etc that will literally remineralize your teeth, and in many cases, reverse caries. Xylitol gums and mouthwashes are a game-changer, as well.
The entire dental industry is only in business because of sugar and ignorance. Fortunately for them, the overall vanity level of society is increasing, so they'll likely make up for it with whitening sessions and veneers.
