Near-IR Transillumination and Reflectance Imaging: As an scientific researcher, I have carried out fundamental measurements of sound and demineralized dental hard tissues at NIR wavelengths, investigated the optical properties of developmental defects, looked at differences in the NIR optical properties of deciduous enamel, discovered that optical attenuation in dental enamel increases markedly with loss of mobile water, explored the image contrast of dental caries at other NIR wavelengths besides 1300-nm and developed and calibrated a ultra-high resolution digital X-ray microradiography system that is able to quantify lesion severity of enamel and dentin by measurement of the relative mineral loss. In addition to those studies I have constructed a fully automated Mueller-matrix imaging system that can be used to completely describe the interaction of polarized light with dental hard tissues which will be used to study how different types of polarized light is depolarized by dental hard tissues and dental materials.

Polarization-Sensitive Optical Coherence Tomography (PS-OCT): Our ongoing research in vitro and in vivo studies seek to validate PS-OCT as a clinical tool for the accurate and early clinical assessment of tooth demineralization and remineralization. PS-OCT is ideally suited for acquiring cross sectional images of lesion structure. Changes in lesion structure occur upon remineralization and we have published the first papers showing that PS-OCT can be used to monitor such changes both in vitro and in vivo. Therefore it can potentially be used for monitoring lesion severity and for assessing the activity of early carious lesions without the use of ionizing radiation. These in vitro and in vivo studies have demonstrated the great potential of PS-OCT as a valuable tool for both clinical diagnosis of lesions and for clinical studies. We have carried out the first clinical studies showing that PS-OCT and cross-polarization optical coherence tomography (CP-OCT) can be used to monitor the development of early demineralization, the effect of fluoride (glass ionomer cements and fluoride varnish) and lesion activity, and have developed automated methods for assessing the severity of demineralization that can be used both in vitro and in vivo.

Real-Time Imaging of Laser Ablation and Composite Removal: The highlights of this proposed research is the development of laser-based methods for the selective removal of caries lesions and composite restorative materials using image guidance and spectral feedback to control the laser scanning system. Our group has carried out the development of near-IR, fluorescence and OCT image analysis methods for programming the laser system for selective removal of caries lesions and to develop OCT imaging as a diagnostic of laser ablation. We have also looked at NIR imaging to monitor laser ablation through dental enamel in real-time to directly visualize peripheral thermal and mechanical damage.