Caries detection dye was a b-i-g advance in detecting decay. We use this too.

The very latest in detecting decay is a LASER instrument - DIAGNOdent - which beams inside the tooth and fluoresces when it contacts decay, even at it's absolute earliest stage.

Now we have the pinpoint accuracy of lasers, and .... early treatment is conservative treatment, often using Air Abrasion - the No Needles, No Drill technique.