Imaging of Secondary Caries With Polarization Sensitive Optical Coherence Tomography

Background: Secondary caries is a primary reason that dental restorations are replaced. Current methods to diagnose and validate the presence of these lesions are considered insufficient due to their low sensitivity. Polarization-sensitive optical coherence tomography (PS-OCT) is a non-invasive and non-ionizing technique for creating cross-sectional images of internal biological structures that employs linearly polarized light to detect subsurface demineralization by an increase in backscattering and depolarization. Although PS-OCT imaging studies have confirmed its effectiveness for imaging carious subsurface lesions in enamel and dentin the effect of imaging through an existing resin restoration has been minimally investigated. Objective: To demonstrate that polarization-sensitive optical coherence tomography is capable of detecting artificial caries lesions in vitro in enamel underneath resin composite restorations. Methods: Extracted posterior human teeth (n=11) were mounted in acrylic blocks. A preparation of 1x2x1 mm was made on the facial surface and the preparations were demineralized for 48 hrs. A negative control preparation of equal dimensions to the demineralized preparation was placed on the lingual of each tooth. Both preparations were restored with Filtek Z-250™ (3M Espe) composite. Optical changes in demineralized versus control preparations beneath restorations was measured as a function of depth using a single mode fiber autocorrelator-based optical coherence domain reflectometer operating at 1310 nm. The presence of demineralization in the artificial lesion preparations was confirmed by polarized light microscopy on histological thin sections. Results: PS-OCT imaging indicated that a significant increase in reflectivity depth occurred in the artificial lesions compared with the control preparations (p<0.05). Polarized light microscopy demonstrated that the zone of demineralization in the artificial lesions was significant compared with the control preparations (p<0.0001). Conclusion: This study suggests that PS-0CT is well-suited to non-destructively detect early caries lesions in enamel beneath composite restorations. Support: NIH/NIDCR Grants RO1-DE17869 and RO1-DE14698