Here is a link to a news story about the amazing Canary caries detection system.
…he’d always relied on a visual examination with his eyes, and a probe to test for softness. Now, he’s also using the Canary cavity detector. It uses low-power pulsating laser light to search for decay where x-rays can’t. The light penetrates 5 millimeters beneath the tooth surface. “We’re able to see under fillings, under composite restorations – those are the white fillings – under crowns, under sealants, which we could never do before,” says Dr. Tau.