Skip to main content
eScholarship
Open Access Publications from the University of California

Scholarly Works (16 results)

  • Thesis
  • Peer Reviewed
UC San Francisco Electronic Theses and Dissertations (2016)

New, more sophisticated diagnostic tools are needed for the detection and characterization of caries lesions in the early stages of development. It is not sufficient to simply detect caries lesions, methods are needed to assess the activity of the lesion and determine if chemical or surgical intervention is needed. Previous studies have demonstrated that polarization sensitive optical coherence tomography (PS-OCT) can be used to nondestructively image the subsurface lesion structure and measure the thickness of the highly mineralized surface zone. Other studies have demonstrated that the rate of dehydration can be correlated with the lesion activity and that the rate can be measured using optical methods. The main objective of this work was to test the hypothesis that optical methods can be used to assess lesion activity on tooth coronal and root surfaces.

Simulated caries models were used to develop and validate an algorithm for detecting and measuring the highly mineralized surface layer using PS-OCT. This work confirmed that the algorithm was capable of estimating the thickness of the highly mineralized surface layer with high accuracy. Near-infrared (NIR) reflectance and thermal imaging methods were used to assess activity of caries lesions by measuring the state of lesion hydration. NIR reflectance imaging performed the best for artificial enamel and natural coronal caries lesion samples, particularly at wavelengths coincident with the water absorption band at 1460-nm. However, thermal imaging performed the best for artificial dentin and natural root caries lesion samples. These novel optical methods outperformed the conventional methods (ICDAS II) in accurately assessing lesion activity of natural coronal and root caries lesions.

Infrared-based imaging methods have shown potential for in-vivo applications to objectively assess caries lesion activity in a single examination. It is likely that if future clinical trials are a success, this novel imaging technology will be employed for the detection and monitoring of early carious lesions without the use of ionizing radiation, thereby enabling conservative non-surgical intervention and the preservation of healthy tissue structure.

    Cover page: Optical Assessment of Caries Lesion Structure and Activity
    • Article
    • Peer Reviewed
    UC San Francisco Previously Published Works (2014)
    Accurate measurement of the highly mineralized transparent surface layer that forms on caries lesions is important for diagnosis of the lesion activity because chemical intervention can slow or reverse the caries process via remineralization. Previous in-vitro and in-vivo studies have demonstrated that polarization-sensitive optical coherence tomography (PS-OCT) can nondestructively image the subsurface lesion structure and the highly mineralized transparent surface zone of caries lesions. The purpose of this study was to develop an approach to automatically process 3-dimensional PS-OCT images and to accurately assess the remineralization process in simulated enamel lesions. Artificial enamel lesions were prepared on twenty bovine enamel blocks using two models to produce varying degree of demineralization and remineralization. The thickness of the transparent surface layer and the integrated reflectivity of the subsurface lesion were measured using PS-OCT. The automated transparent surface layer detection algorithm was able to successfully detect the transparent surface layers with high sensitivity ( = 0.92) and high specificity ( = 0.97). The estimated thickness of the transparent surface layer showed a strong correlation with polarized light microscopy (PLM) measurements of all regions (R(2) = 0.90). The integrated reflectivity, ΔR, and the integrated mineral loss, ΔZ, showed a moderate correlation (R(2) = 0.32). This study demonstrates that PS-OCT can automatically measure the changes in artificial enamel lesion structure and severity upon exposure to remineralization solutions.
      Cover page: Automated assessment of the remineralization of artificial enamel lesions with polarization-sensitive optical coherence tomography
      • Article
      • Peer Reviewed
      UC San Francisco Previously Published Works (2016)
      New diagnostic methods are needed for the accurate assessment of caries lesion activity to establish the need for surgical treatment. Detection of the highly mineralized surface layer that forms near the surface of the lesions as a result of remineralization is important for diagnosis of the lesion activity. Previous studies have demonstrated that novel imaging methods can be used to detect remineralization of artificial enamel caries lesions. In this paper, the activity of natural enamel caries lesions was assessed in-vitro via detection of the surface layer with PS-OCT and dehydration rate measurements with NIR reflectance and thermal imaging modalities. An automated approach for detecting the surface layer with PS-OCT yielded high sensitivity (= 0.79) and high specificity (= 0.93) with moderate correlation (R2 = 0.5920) with histology. Significant differences in dehydration rate measurements were found between the active and the arrested lesions using both the NIR reflectance and thermal imaging modalities. These results demonstrate that these novel imaging methods are ideally suited for nondestructive, noninvasive and quantitative measurement of lesion activity during a single clinical examination in real-time.
        Cover page: Infrared Methods for Assessment of the Activity of Natural Enamel Caries Lesions
        • Article
        • Peer Reviewed
        UC San Francisco Previously Published Works (2015)

        Objectives

        Previous studies have demonstrated that the optical changes due to the loss of water from porous lesions can be exploited to assess lesion severity with QLF, thermal and near-IR imaging. Since arrested lesions are less permeable to water due to the highly mineralized surface layer, changes in the rate of water loss can be related to changes in lesion structure. The purpose of this study was to investigate whether the rate of water loss correlates with the degree of remineralization and whether that rate can be measured using thermal and near-IR reflectance imaging.

        Methods

        Artificial bovine enamel lesions (n=30) were prepared by immersion in a demineralization solution for either 8 and 24 h and they were subsequently placed in an acidic remineralization solution for different periods. The samples were dehydrated using an air spray for 30s and surfaces were imaged using a thermal camera and an InGaAs camera at 1300-1700 nm wavelengths.

        Results

        The area enclosed by the time-temperature curve, ΔQ, from thermal imaging showed significant differences (P<0.05) between the lesion window and other windows. Near-IR reflectance intensity differences, ΔI, before and after dehydration decreased with longer periods of remineralization. Only near-IR reflectance imaging was capable of detecting significant differences (P<0.05) between the different periods of remineralization.

        Conclusions

        This study demonstrated that both thermal and near-IR reflectance imaging were suitable for the detection of remineralization in simulated caries lesions and near-IR wavelengths longer than 1400 nm are well suited for the assessment of remineralization.
          Cover page: Assessment of remineralization via measurement of dehydration rates with thermal and near-IR reflectance imaging
          • Article
          • Peer Reviewed
          UC San Francisco Previously Published Works (2017)
          Previous studies have demonstrated that the permeability changes due to the surface modification of dentin can be quantified via thermal imaging during dehydration. The CO2 laser has been shown to remove the smear layer and disinfect root canals. Moreover, thermal modification via CO2 laser irradiation can be used to convert dentin into a highly mineralized enamel-like mineral. The purpose of this study is to evaluate the radicular dentin surface modification after CO2 laser irradiation by measuring the permeability with thermal imaging. Human molar specimens (n=12) were sectioned into 4 axial walls of the pulp chamber and treated with either 10% NaClO for 1 minute, 5% EDTA for 1 minute, CO2 laser or none. The CO2 laser was operated at 9.4 μm with a pulse duration of 26 μs, pulse repetition rate of 300 Hz and a fluence of 13 J/cm2. The samples were dehydrated using an air spray for 60 seconds and imaged using a thermal camera. The resulting surface morphological changes were assessed using 3D digital microscopy. The images from digital microscopy confirmed melting of the mineral phase of dentin. The area enclosed by the time-temperature curve during dehydration, ΔQ, measured with thermal imaging increased significantly with treatments with EDTA and the CO2 laser (P<0.05). These results indicate that the surface modification due to CO2 laser treatment increases permeability of radicular dentin.
            Cover page: Assessment of radicular dentin permeability after irradiation with CO2 laser and endodontic irrigation treatments with thermal imaging
            • Article
            • Peer Reviewed
            UC San Francisco Previously Published Works (2017)
            The increasing prevalence of mild hypomineralization due to developmental defects on tooth surfaces poses a challenge for caries detection and caries risk assessment and reliable methods need to be developed to discriminate such lesions from active caries lesions that need intervention. Previous studies have demonstrated that areas of hypomineralization are typically covered with a relatively thick surface layer of highly mineralized and transparent enamel similar to arrested lesions. Seventy-six extracted human teeth with mild to moderate degrees of suspicious fluorosis were imaged using near-infrared reflectance and transillumination. Enamel hypomineralization was clearly visible in both modalities. However, it was difficult to distinguish hypomineralization due to developmental defects from caries lesions with contrast measurements alone. The location of the lesion on tooth coronal surface (i.e. generalized vs. localized) seems to be the most important indicator for the presence of enamel hypomineralization due to developmental defects.
              Cover page: Near-infrared imaging of enamel hypomineralization due to developmental defects
              • Article
              • Peer Reviewed
              UC San Francisco Previously Published Works (2016)
              Accurate detection and measurement of the highly mineralized surface layer that forms on caries lesions is important for the diagnosis of lesion activity. Previous studies have demonstrated that optical imaging methods can be used to measure the degree of remineralization on enamel lesions. The purpose of this study was to determine if thermal and near-IR reflectance imaging could be used to assess the remineralization process in simulated dentin lesions. Artificial bovine (n=15) dentin lesions were prepared by immersion in a demineralization solution for 24 hours and they were subsequently placed in an acidic remineralization solution for up to 12 days. The samples were dehydrated using an air spray for 30 seconds and imaged using thermal and InGaAs cameras. The area enclosed by the time-temperature curve, ΔQ, from thermal imaging decreased significantly with longer periods of remineralization. However, near-IR reflectance intensity differences, ΔI, before and after dehydration failed to show any significant relationship with the degree of remineralization. This study shows that thermal imaging can be used for the assessment of the remineralization of dentin lesions.
                Cover page: Assessment of remineralized dentin lesions with thermal and near-infrared reflectance imaging
                • Article
                • Peer Reviewed
                UC San Francisco Previously Published Works (2017)
                The purpose of this study was to evaluate thermal and near-infrared (NIR) reflectance imaging methods for the assessment of the activity of root caries lesions. In addition, changes in the lesion structure were monitored with polarization sensitive optical coherence tomography (PS-OCT). Artificial bovine and natural root caries lesions were imaged with PS-OCT, and their dehydration rate was measured with thermal and NIR cameras. The lesion activity of the natural root caries samples was also assessed by two clinicians by conventional means according to ICDAS II guidelines. The thickness of the highly mineralized transparent surface layer measured using PS-OCT increased and the area enclosed by the time-temperature curve, ΔQ, measured with thermal imaging decreased significantly with longer periods of remineralization in simulated dentin lesions, but the NIR reflectance intensity differences, ΔI, failed to show any significant relationship with the degree of remineralization. The PS-OCT algorithm for the automated assessment of remineralization successfully detected the highly mineralized surface layer on both natural and simulated lesions. Thermal imaging provided the most accurate diagnosis of root caries lesion activity. These results demonstrate that thermal imaging and PS-OCT may be ideally suited for the nondestructive root caries lesion activity during a clinical examination.
                  Cover page: Activity assessment of root caries lesions with thermal and near‐IR imaging methods
                  • Article
                  • Peer Reviewed
                  UC San Francisco Previously Published Works (2016)
                  Previous studies have demonstrated that the structural changes on enamel due to demineralization and remineralization can be exploited through optical imaging methods such as QLF, thermal and NIR imaging. The purpose of this study is to investigate whether PS-OCT and NIR reflectance imaging can be utilized to assess lesion structure in artificial enamel lesions on the smooth surfaces of primary teeth exposed to fluoride. The smooth coronal surfaces of primary teeth (n=25) were divided into 4 windows: sound, demineralization, demineralization with remineralization and APF with demineralization. Windows were treated with either acidulated phosphate fluoride (APF) for 1 minute, a demineralization solution for 4 days, and/or an acidic remineralization solution for 12 days. The samples were imaged using PS-OCT, QLF and NIR reflectance at 1400-1700 nm wavelengths. This study demonstrated that both PS-OCT and NIR reflectance imaging were suitable for assessing lesion structure in the smooth surfaces of primary dentition.
                    Cover page: Assessment of simulated lesions on primary teeth with near-infrared imaging
                    • Article
                    • Peer Reviewed
                    UC San Francisco Previously Published Works (2016)

                    Background and objectives

                    Current clinical methods for diagnosing secondary caries are unreliable for identifying the early stages of decay around restorative materials. The objective of this study was to access the integrity of restoration margins in natural teeth using near-infrared (NIR) reflectance and transillumination images at wavelengths between 1300 and 1700-nm and to determine the optimal NIR wavelengths for discriminating composite materials from dental hard tissues.

                    Materials and methods

                    Twelve composite margins (n=12) consisting of class I, II and V restorations were chosen from ten extracted teeth. The samples were imaged in vitro using NIR transillumination and reflectance, polarization sensitive optical coherence tomography (PS-OCT) and a high-magnification digital microscope. Samples were serially sectioned into 200-μm slices for histological analysis using polarized light microscopy (PLM) and transverse microradiography (TMR). Two independent examiners evaluated the presence of demineralization at the sample margin using visible detection with 10× magnification and NIR images presented digitally. Composite restorations were placed in sixteen sound teeth (n=16) and imaged at multiple NIR wavelengths ranging from λ=1300 to 1700-nm using NIR transillumination. The image contrast was calculated between the composite and sound tooth structure.

                    Results

                    Intensity changes in NIR images at wavelengths ranging from 1300 to 1700-nm correlate with increased mineral loss measured using TMR. NIR reflectance and transillumination at wavelengths coincident with increased water absorption yielded significantly higher (P<0.001) contrast between sound enamel and adjacent demineralized enamel. In addition, NIR reflectance exhibited significantly higher (P<0.01) contrast between sound enamel and adjacent composite restorations than visible reflectance.

                    Significance

                    This study shows that NIR imaging is well suited for the rapid screening of secondary caries lesions.
                      Cover page: Near-infrared imaging of secondary caries lesions around composite restorations at wavelengths from 1300–1700-nm
                      Top