OBJECTIVES: To optimize a microtomographic (micro-CT) technique to quantitatively evaluate the effectiveness of contemporary caries-excavation techniques. METHODS: A beam-hardening curve was obtained from an initial reconstruction of a wedge-shaped hydroxyapatite (HAp) block and fitted with a 5th order polynomial function, after which each micro-CT tooth slice was corrected accordingly. Calibration of the 8-bit gray values into mineral-density values was obtained by scanning, reconstructing and processing volume of interests (VOIs) of HAp phantoms with different mineral densities (0.25, 0.75, 3.14g/cm(3)). One carious tooth was scanned before and after caries removal with an experimental enzyme-based gel. After reconstruction, a 3D-median filter was applied to each micro-CT slice, and a connected threshold grower algorithm was used to blank-out undesired structures in each slice. Volume rendering with a look-up-table (LUT), based on mineral densities, was accomplished for the tooth before and after caries removal. Finally, the actual volume of excavated tissue was quantified. RESULTS: Correction for beam hardening produced tooth slices with relatively homogeneous gray values along the whole area of enamel and dentin. Accurate mineral-density values were obtained for enamel, dentin and carious regions (2.89, 1.74 and 0.27g/cm(3), respectively). After pre-processing (3D-median filtering and connected threshold grower algorithm), acceptable segmentation of carious dentin based on gray values was accomplished (Otsu method, gray value=75 or mineral density=1.12g/cm(3)), from which quantitative volumetric parameters were calculated. SIGNIFICANCE: Accurate calibration, standardization of scanning and reconstruction steps and adequate pre-processing of micro-CT slices allowed detailed volumetric calculation of caries-excavation techniques. Copyright (c) 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
OBJECTIVES: To optimize a microtomographic (micro-CT) technique to quantitatively evaluate the effectiveness of contemporary caries-excavation techniques. METHODS: A beam-hardening curve was obtained from an initial reconstruction of a wedge-shaped hydroxyapatite (HAp) block and fitted with a 5th order polynomial function, after which each micro-CT tooth slice was corrected accordingly. Calibration of the 8-bit gray values into mineral-density values was obtained by scanning, reconstructing and processing volume of interests (VOIs) of HAp phantoms with different mineral densities (0.25, 0.75, 3.14g/cm(3)). One carious tooth was scanned before and after caries removal with an experimental enzyme-based gel. After reconstruction, a 3D-median filter was applied to each micro-CT slice, and a connected threshold grower algorithm was used to blank-out undesired structures in each slice. Volume rendering with a look-up-table (LUT), based on mineral densities, was accomplished for the tooth before and after caries removal. Finally, the actual volume of excavated tissue was quantified. RESULTS: Correction for beam hardening produced tooth slices with relatively homogeneous gray values along the whole area of enamel and dentin. Accurate mineral-density values were obtained for enamel, dentin and carious regions (2.89, 1.74 and 0.27g/cm(3), respectively). After pre-processing (3D-median filtering and connected threshold grower algorithm), acceptable segmentation of carious dentin based on gray values was accomplished (Otsu method, gray value=75 or mineral density=1.12g/cm(3)), from which quantitative volumetric parameters were calculated. SIGNIFICANCE: Accurate calibration, standardization of scanning and reconstruction steps and adequate pre-processing of micro-CT slices allowed detailed volumetric calculation of caries-excavation techniques. Copyright (c) 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
Authors: Yan Liu; Nan Li; Yipin Qi; Li-na Niu; Sally Elshafiy; Jing Mao; Lorenzo Breschi; David H Pashley; Franklin R Tay Journal: Dent Mater Date: 2011-02-26 Impact factor: 5.304
Authors: Yi-pin Qi; Nan Li; Li-na Niu; Carolyn M Primus; Jun-Qi Ling; David H Pashley; Franklin R Tay Journal: Acta Biomater Date: 2011-10-31 Impact factor: 8.947
Authors: Yan Liu; Sui Mai; Nan Li; Cynthia K Y Yiu; Jing Mao; David H Pashley; Franklin R Tay Journal: Acta Biomater Date: 2010-11-24 Impact factor: 8.947
Authors: Sabra I Djomehri; Susan Candell; Thomas Case; Alyssa Browning; Grayson W Marshall; Wenbing Yun; S H Lau; Samuel Webb; Sunita P Ho Journal: PLoS One Date: 2015-04-09 Impact factor: 3.240