Imaging Enamel Remineralization with Polarization Sensitive Optical Coherence Tomography

Polarization Sensitive Optical Coherence Tomography (PS-OCT) is a non-destructive imaging system that can utilize near-infrared light to produce depth resolved images of dental enamel.

Objective: To investigate the ability of PS-OCT to image enamel remineralization.

Methods:  This study used an all fiber-based PS-OCT system operating at 1310-nm to image demineralized and fluoride-enhanced remineralized artificial lesions.  Artificial lesions were created on smooth surfaces of sound teeth (n=20) by exposing the teeth for 9 days to an acetate buffer solution (pH 4.9).  The artificial lesions (n=10) were then exposed for 20 days to a 2 ppm fluoride containing remineralization solution (pH 7.0).   The PS-OCT system collected serial b-scan images at day-0 and subsequent to the demineralization and remineralization treatments.  Lesion severity was measured with PS-OCT by integrating the perpendicular axis image, which quantifies the scattering and depolarization of the tissue.  After sectioning the samples, polarized light microscopy (PLM) and high resolution digital microradiography (DM) were used for histological evaluation of 200 μm transverse sections. 

Results:  PS-OCT images revealed the presence of a low scattering 35 ± 7 μm surface zone after the artificial lesions were remineralized.  These samples displayed intact non-depolarizing surface zones of 33 ± 5 μm when analyzed with PLM.  No statistical difference in lesion depth before and after remineralization was found with both PS-OCT and PLM.  The remineralized lesions showed a significant decrease in the overall integrated reflectivity compared with the demineralized lesions (Repeated Measures Analysis of Variance, p<0.05).  DM confirmed the increase in mineral volume of the remineralized surface zone.

Conclusion: This study determined that PS-OCT can image the restoration of the surface zone enamel after fluoride-enhanced remineralization of artificial in vitro dental caries.

Supported by NIH/NIDCR Grant 1-R01 DE14698 and T32 DE07306.