Near-Infrared Reflectance Image-Guided Removal of Occlusal Caries Lesions Using a CO₂ Laser

Objectives: Detection and diagnosis of early dental caries lesions can be difficult due to variable tooth coloration, staining of the teeth and poor contrast between sound and demineralized enamel. These problems can be overcome by using near-infrared (NIR) imaging. Previous studies have demonstrated that lasers can be integrated with NIR imaging devices, allowing image-guided ablation. The aim of this study was to demonstrate that NIR reflectance images taken at a wavelength range of 1500 – 1700 nm can be used to guide a 9.3-µm CO₂ laser for the selective removal of demineralization on tooth occlusal surfaces.
Methods: Windows on the occlusal surfaces of sound extracted teeth were subjected to 72-hr demineralization to generate demineralization of varying severity. Sequential NIR reflectance images were used to guide a CO₂ laser for the selective removal of demineralized areas. Polarization-sensitive optical coherence tomography (PS-OCT) was used to assess ablation selectivity. Samples were also sectioned and analyzed using polarized light microscopy.
Results: High contrast NIR reflectance images of occlusal demineralization were acquired without the interference of stain. PS-OCT scans were capable of determining the initial lesion volume and the volume of enamel removed by the CO₂ laser.
Conclusions: NIR reflectance image-guided removal of dental caries is promising for the selective removal of demineralized enamel.