Regarding new instruments and techniques that are available nowadays, there's a wide range available in the United States to practitioners. There are instruments that are based on fluorescence, so you have instruments, for example that use light at the blue end of the spectrum. Many of those use the acronym of QLF, that's quantitative light fluorescence. You will find a wide range of instruments out there that are on the market. Some provide quantification numbers attached to the measurements. Some just provide an image on the screen for you to tag the area that might be different. Then you have instruments that are based on the red end of the spectrum. For example, the DIAGNOdent is a very popular instrument that got into the U.S. market many years ago, that uses this infrared light to detect carious lesions. You have instruments that are based on light reflection. For example, the Midwest Caries I.D. system by DENTSPLY is available. It doesn't supply numbers but is based on differences in reflection of tooth surfaces, sound, or caries. And then you have instruments based on electrical conductivity. The newest one in the U.S. market is called CarieScan. It's really a measurement of impedance or resistance to electricity on a tooth surface, based on whether it's sound or has carious lesions. And you have, of course, transillumination that has been around for awhile. There's a wider range of technologies out there to be able to transilluminate the tooth with very focused light. And you can go outside the digital images to radiographic images, etc., so the scope is very ample in practice, not only to detect lesions but hopefully to monitor the lesions over time.
It should be noted that because of the high level of technical skill needed to use some of these methods, or the expense of the necessary equipment, the only technique that is currently widely used in dental practice is digital radiography.2 The DIAGNOdent tends to be used in some practices as a second opinion during the diagnostic process on occlusal surfaces. The other methods tend to be used mostly in a research setting.