Objective: The objective of this study was to evaluate a new optical method - photon undulatory non-linear conversion (PNC) - for use in different stages of caries detection. Background Data: Caries should be considered an infectious disease managed by risk assessment, early detection, and preventive therapies, rather than simply "drilling and filling." Material and Methods: Fluorescence emission spectroscopy was performed in vitro on 90 extracted teeth, with intact occlusal surfaces. This system differs from the basic Diagnodent unit in its ability to distinguish between different tissue components with respect to their spectrums. Histological analysis served as the gold standard for verification. The teeth sections correspond to the specific point with the highest reading of the detector. The system was compared to visual inspection, probing, and x-ray methods. The system tested (helium-neon [He-Ne], λ = 633 nm) has a fiber optic device that delivers radiation to the tooth and a spectrophotometer device that detects bacterial porphyrins fluorescence, allowing detection of caries, fillings, and calculus by simultaneous measurement of backscattering and fluorescence intensity. Results: The system tested provides quantitatively reproducible measurements and detection even through sound enamel of more than 1 mm in thickness. Conclusion: The PNC method detects different stages of caries lesions in real time, and it exceeds x-rays in sensitivity, without any ionizing radiation. Preliminary results showed a high potential of using the PNC method in clinical practice (98 % accuracy) in comparison to the other methods.