Today we need all the tools technology can help us with for better diagnostic. When decay strikes the tooth we use a tool called explorer and radiograph, an X-ray to verify our diagnosis. Both of them are deficient when it comes to a small cavity. The DIAGNOdent is a tool that can help us to recognize one. It uses laser fluorescence to aid in the detection of caries within the tooth structure. Healthy tooth structure shows little or no fluorescence but decayed fluoresce exposed to a 655 nm diode laser. An audio signal allows the operator to hear changes in the scale values.