Selective Ablation of Carious Lesions using an Integrated Near-IR Imaging System and a Novel 9.3-µm CO₂ Laser

Previous studies have shown that reflectance imaging at wavelengths greater than 1200-nm can be used to image demineralization on tooth occlusal surfaces with high contrast and without the interference of stains. In addition, these near-IR imaging systems can be integrated with laser ablation systems for the selective removal of carious lesions. Higher wavelengths, such as 1950-nm, yield higher lesion contrast due to higher water absorption and lower scattering. In this study, a point-to-point scanning system employing diode and fiber lasers operating at 1450, 1860, 1880, and 1950-nm was used to acquire reflected light images of the tooth surface. Artificial lesions were imaged at these wavelengths to determine the highest lesion contrast. Near-IR images at 1880-nm were used to demarcate lesion areas for subsequent selective carious lesion removal using a new compact air-cooled CO₂ laser prototype operating at 9.3-µm. The highest lesion contrast was at 1950-nm and the dual NIR/CO₂ laser system selectively removed the simulated lesions with a mean loss of only 12-µm of sound enamel.