Imaging dental fluorosis at SWIR wavelengths from 1300 to 2000-nm

Abstract

Dental fluorosis is an increasing problem in the U.S. due to excessive exposure to fluoride from the environment. Fluorosis causes hypomineralization of the enamel during tooth development and mild fluorosis is visible as faint white lines on the tooth surface while the most severe fluorosis can result in pitted surfaces. It is difficult to quantify the severity of fluorosis and assessments are limited to subjective visual assessments. Dental fluorosis appears with very high contrast at short wavelength infrared (SWIR) wavelengths beyond 1400-nm and we hypothesize that these wavelengths may be better suited for detecting mild fluorosis and for estimating the severity. In this study the contrast of fluorosis of varying severity on extracted human permanent teeth was measured at SWIR wavelengths ranging from 1300-2000-nm using an extended range InGaAs camera and broadband light sources. Cross polarization optical coherence tomography was used to measure the depth of hypomineralization.

Keywords: SWIR imaging; dental fluorosis; optical coherence tomography.

Fig. 1.

Schematic of the experimental setup showing (A) tungsten-halogen light source with bandpass filters, collimating lens and polarizer, (B) polarized 1950-nm fiber optic light source, (C) Xenics extended range InGaAs camera with lens and polarizer, (D) air nozzle and (E) tooth samples mounted on XYZ stage. Light sources A & B were positioned on the same side for these measurements.

Fig. 2.

(A) CP-OCT b-scan acquired at the position of the dashed line in the (B) color image of one of the teeth with fluorosis. (C) QLF and cross-polarization SWIR images at (D) 1950, (E) 1300 (F) 1460, (G) 1535 and (H) 1675 nm.

Fig. 3.

Plot of contrast of hypomineralization mean±S.D. for five teeth with fluorosis versus wavelength.