Assessing the comparative efficacy of forensic torch excitation wavelengths for dental restoration differentiation: a pilot study

Abstract

Background: The increasing sophistication of restorative materials in replicating natural tooth fluorescence poses a challenge for both antemortem and postmortem dental charting. This study evaluated the efficacy of various discrete excitation wavelengths, including those from common forensic torches, in differentiating modern restorative materials from tooth. Methods: Conducted within the Institute for Photonics and Advanced Sensing (IPAS) laboratory framework, six extracted human molars and five contemporary A3-shade restorative materials were examined via spectrophotometry across five excitation wavelengths: 266, 300, 365, 395 and 426nm. Canonical Discriminant Analysis (CDA) was applied to Peak Intensity and Peak Emission Wavelength data to quantify the multivariate statistical separation between groups. Results: UV-A wavelengths of 365nm and 395nm produced the most robust group separation. While 365nm excitation produced the highest absolute emission intensities for visual detection, 395nm excitation elicited unique spectral red-shifts in composite resins, providing the highest mathematical discrimination. Visible violet excitation at 426nm was the least reliable differentiator. Conclusion: For forensic practitioners, UV-A torches (365–395 nm) remain effective for detecting the tooth-coloured restorations tested here. While 365nm is optimal for rapid visual screening 395nm provides a more distinctive spectral fingerprints for formal characterisation. Despite improved fluorescence matching under visible light, the modern restorative materials tested here retain unique spectral signatures under UV-A illumination, though variable fluorescence intensity influenced detectability and may limit generalisation to other restorations or teeth.

KEYWORD:

Forensic Odontology, Dental Fluorescence, Restorative materials, Canonical Discriminant Analysis, Post-mortem identification