Alternative and simple method to determine the refractive index of human dentin

Determining a substance's refractive index (RI) is of great importance in a wide variety of disciplines, such as chemistry, biomedicine, engineering, and optics, to name just a few. This work utilizes critical-angle reflectometry to measure the refractive index of dentin, a biological tissue characterized by its high RI and complex structure. We fabricated a hollow semicircular prism and filled it with bromonaphthalene (1-B), allowing us to measure RIs up to 1.65. We used 5 tooth samples with exposed dentin and a laser diode beam (λ = 650 nm) incident on interface 1-B/Dentine; the reflectance curve was measured from 60° to 75°. The critical angle is determined, and dentin RI is calculated. The real part of the calculated dentine's RI coincided well with those determined by other more expensive and specialized techniques with high technical support.