Stephen B Dove

Mechanical Loading Stimulates Differentiation of Periodontal Osteoblasts in a Mouse Osteoinduction Model: Effect on Type I Collagen and Alkaline Phosphatase Genes

Abstract The effects of mechanical loading on the osteoblast phenotype remain unclear because of many variables inherent to the current experimental models. This study reports on utilization of a mouse tooth movement model and a semiquantitative video image analysis of in situ hybridization to determine the effect of mechanical loading on cell-specific expression of type I collagen (collagen I) and alkaline phosphatase (ALP) genes in periodontal osteoblasts, using nonosseous cells as an internal standard. The histomorphometric analysis showed intense osteoid deposition after 3 days of treatment, confirming the osteoinductive nature of the mechanical signal. The results of in situ hybridization showed that in control periodontal sites both collagen I and ALP mRNAs were expressed uniformly across the periodontium. Treatment for 24 hours enhanced the ALP mRNA level about twofold over controls and maintained that level of stimulation after 6 days. In contrast, collagen I mRNA level was not affected after 24 hours of treatment, but it was stimulated 2.8-fold at day 6. This increase reflected enhanced gene expression in individual osteoblasts, since the increase in osteoblast number was small. These results indicate that (1) the mouse model and a semiquantitative video image analysis are suitable for detecting osteoblast-specific gene regulation by mechanical loading; (2) osteogenic mechanical stress induces deposition of bone matrix primarily by stimulating differentiation of osteoblasts, and, to a lesser extent, by an increase in number of these cells; (3) ALP is an early marker of mechanically-induced differentiation of osteoblasts. (4) osteogenic mechanical stimulation in vivo produces a cell-specific 2.8-fold increase in collagen gene expression in mature, matrix-depositing osteoblasts located on the bone surface and within the osteoid layer.

6-Bit and 8-bit digital radiography for detecting simulated periodontal lesions

The purpose of this study was to compare the diagnostic performance of a digital radiography system that uses 6- and 8-bit displays with conventional D-speed film for the detection of simulated periodontal bone lesions. Eleven human hemimandibles were used as specimens. Simulated lesions were created at the buccal cortical plate in the marginal bone area with the use of a round bur 1.4 mm in diameter. Lesions were created in a defined sequence to preclude visual cues as to the depth of the lesions. Lesion size progressed in 0.5 mm increments. At each stage the mandibles were imaged with a Sens-A-Ray system (REGAM Medical Systems AB, Sundsvall, Sweden) and D-speed film. Exposure parameters for each specimen/receptor combination were standardized by either the mean optical density or mean gray value at the approximal crestal bone area. Film images and digital images displayed with 64 and 256 gray levels were presented to six observers for evaluation. Observers were ask to rate their confidence as to the presence or absence of a lesion using a 5-point confidence scale. A total of 96 lesion sites and 96 control sites were presented to the observers. Receiver operating characteristic curves were generated for each system. The area under the curve was used as the index of diagnostic accuracy. The mean receiver operating characteristic areas for 6-bit and 8-bit displays and D-speed film were 0.746 +/- 0.043, 0.717 +/- 0.056 and 0.742 +/- 0.059, respectively. Analysis of variance was used to compare the means. No statistical difference was found between any of the three image displays (p > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Morphometric analysis of the dental pulp chamber as a method of age determination in humans

Eighty bite-wing radiographs from 40 female and 40 male patients were selected from the patient record system at the University of Texas Dental School at San Antonio, Texas. All samples were equally divided into four age groups, with a range from 15 to 55 years of age. The lower right first permanent molar tooth was chosen as the representative tooth for measuring the maximum height and width of the pulp chamber. The reproducibility of the method was checked by repeating all measurements on two different occasions. Regression analysis indicates that the height and width of the pulp chamber were negatively correlated with age (height r = −0.376 and width r = −0.125). The coefficient of determination (r2) for pulp chamber height and width were 0.123 and 0.058, respectively. This indicates that although there appears to be a definite relationship between the age of an individual and the height and width of the dental pulp chamber, these measures cannot be used as a reliable method of age determination.

Modification and benchmarking of MCNP for low-energy tungsten spectra

The MCNP Monte Carlo radiation transport code was modified for diagnostic medical physics applications. In particular, the modified code was thoroughly benchmarked for the production of polychromatic tungsten x-ray spectra in the 30-150 kV range. Validating the modified code for coupled electron-photon transport with benchmark spectra was supplemented with independent electron-only and photon-only transport benchmarks. Major revisions to the code included the proper treatment of characteristic K x-ray production and scoring, new impact ionization cross sections, and new bremsstrahlung cross sections. Minor revisions included updated photon cross sections, electron-electron bremsstrahlung production, and K x-ray yield. The modified MCNP code is benchmarked to electron backscatter factors, x-ray spectra production, and primary and scatter photon transport.

Computer‐aided Dental Identification: An Objective Method for Assessment of Radiographic Image Similarity*

Abstract:  A pilot study evaluated a computer‐based method for comparing digital dental images, utilizing a registration algorithm to correct for variations in projection geometry between images prior to a subtraction analysis. A numerical assessment of similarity was generated for pairs of images. Using well‐controlled laboratory settings, the method was evaluated as to its ability to identify the correct specimen with positive results. A subsequent clinical study examined longitudinal radiographic examinations of selected anatomical areas on 47 patients, analyzing the computer‐based method in making the correct identification based upon a threshold level of similarity. The results showed that at a threshold of 0.855, there were two false negative and two false positive identifications out of 957 analyses. Based on these initial findings, 25 dental records having two sets of full mouth series of radiographs were selected. The radiographs were digitized and grouped into six anatomical regions. The more recent set of films served as postmortem images. Each postmortem image was analyzed against all other images within the region. Images were registered to correct for differences in projection geometry prior to analysis. An area of interest was selected to assess image similarity. Analysis of variance was used to determine that there was a significant difference between images from the same individual and those from different individuals. Results showed that the threshold level of concordance will vary with the anatomical region of the mouth examined. This method may provide the most objective and reliable method for postmortem dental identification using intra‐oral images.

Root morphology and anatomical patterns in forensic dental identification: a comparison of computer-aided identification with traditional forensic dental identification.

Abstract:  An online forensic dental identification exercise was conducted involving 24 antemortem–postmortem (AM–PM) dental radiograph pairs from actual forensic identification cases. Images had been digitally cropped to remove coronal tooth structure and dental restorations. Volunteer forensic odontologists were passively recruited to compare the AM–PM dental radiographs online and conclude identification status using the guidelines for identification from the American Board of Forensic Odontology. The mean accuracy rate for identification was 86.0% (standard deviation 9.2%). The same radiograph pairs were compared using a digital imaging software algorithm, which generated a normalized coefficient of similarity for each pair. Twenty of the radiograph pairs generated a mean accuracy of 85.0%. Four of the pairs could not be used to generate a coefficient of similarity. Receiver operator curve and area under the curve statistical analysis confirmed good discrimination abilities of both methods (online exercise = 0.978; UT‐ID index = 0.923) and Spearman’s rank correlation coefficient analysis (0.683) indicated good correlation between the results of both methods. Computer‐aided dental identification allows for an objective comparison of AM–PM radiographs and can be a useful tool to support a forensic dental identification conclusion.

Comparison between intraoral indirect and conventional film-based imaging for the detection of dental root fractures: an ex vivo study.

Digital intraoral radiographic systems have been rapidly replacing conventional dental X-ray films for diagnosis of dental diseases. Current scientific literature supports the use of these digital systems for the detection of dental caries, periodontal bone loss, and periapical pathologies. However, relatively few studies have been published addressing the detection of dental root fractures. The purpose of this study was to compare the intraoral F-speed film (Insight) with two photostimulable phosphor (PSP) indirect digital systems (ScanX and Digora Optime) for the detection of simulated dental root fractures. Ten raters evaluated images acquired from 10 dry human cadaver mandibles under optimal viewing conditions. These data were analyzed by a 5-point receiver operating characteristic curve analysis for statistical differences. Sensitivity and specificity of these systems were also assessed. Since statistically significant difference between the systems was not observed, the results of this study agreeably support indirect digital PSP plates as an alternative to the evaluated conventional film for the detection of dental root fractures.

Magnetic resonance spectroscopy of inflammation associated with the temporomandibular joint

Noninvasive early recognition and treatment of temporomandibular joint dysfunction remains a diagnostic challenge. This pilot study evaluated the use of phosphorus 31 magnetic resonance spectroscopy with magnetic resonance imaging to measure alterations in pH and high-energy phosphate metabolite ratios of muscle that is adjacent to an inflamed temporomandibular joint. Ten New Zealand white rabbits were used in this study. Two animals were used to develop signal acquisition protocols and to ensure that stable baseline data could be measured. In each of the eight animals used in the experiment, one temporomandibular joint was injected with a suspension of silica particles and the contralateral joint served as a control. Data were collected from control and experimental joints on days 0, 7, 14, 21, and 28, after the injection. At the end of the study, temporomandibular joints were block resected and histologically examined to confirm the presence of an inflammatory response. Results indicated that pH and metabolite ratios could be obtained by 31P-magnetic resonance spectroscopy. Changes in pH and some metabolite ratios in experimental joints showed statistical significance (p < 0.001). Differences were seen on day 2 and day 7 (p = 0.040 and p = 0.008, respectively) in the phosphocreatine/alpha-adenosine triphosphate ratios. This contrasts with phosphocreatine/beta adenosine triphosphate ratios that showed significance that began at day 7 (p = 0.022) and continued to day 14 (p = 0.025). Histologic examination indicated that the tissue response within the joint capsule was less than the granulomatous reaction expected.(ABSTRACT TRUNCATED AT 250 WORDS)

Medical data standards

Existing clinical nomenclatures do not provide comprehensive, detailed coverage for multispecialty biomedical imaging. To address clinical needs in this area, the College of American Pathologists (CAP), secretariat of the Systematized Nomenclature of Human and Veterinary Medicine (SNOMED), has entered into partnership with the DICOM (Digital Imaging and Communications in Medicine) Standards Committee, the American College of Radiology, the American Dental Association, the American Academy of Ophthalmology, the American Society for Gastrointestinal Endoscopy, the American Academy of Neurology, the American Veterinary Medical Association, and other professional specialty organizations to develop the controlled terminology that is needed for diagnostic imaging applications. Terminology development is coordinated with ongoing development and maintenance of the DICOM Standard. SNOMED content is being enhanced in two general areas: 1) imaging procedure descriptions and 2) diagnostic observations. The SNOMED DICOM Microglossary (SDM) has been developed to provide context-dependent value sets (SDM Context Groups) for DICOM codedentry data elements and semantic content specifications (SDM Templates) for reports and other structures composed of multiple data elements. The capability of storing explicitlylabeled coded descriptors from the SDM in DICOM images and reports improves the potential for selective retrieval of images and related information. A pilot test of distributed multispecialty terminology development using a World Wide Web (WWW) application was performed in 1997, demonstrating the feasibility of large-scale distributed development of SDM

Measurement and Validation of Benchmark-Quality Thick-Target Tungsten X-Ray Spectra below 150 kVp

Abstract Mercier, J. R., Kopp, D. T., McDavid, W. D., Dove, S. B., Lancaster, J. L. and Tucker, D. M. Measurement and Validation of Benchmark-Quality Thick-Target Tungsten X-Ray Spectra below 150 kVp. Pulse-height distributions of two constant potential X-ray tubes with fixed anode tungsten targets were measured and unfolded. The measurements employed quantitative alignment of the beam, the use of two different semiconductor detectors (high-purity germanium and cadmium-zinc-telluride), two different ion chamber systems with beam-specific calibration factors, and various filter and tube potential combinations. Monte Carlo response matrices were generated for each detector for unfolding the pulse-height distributions into spectra incident on the detectors. These response matrices were validated for the low error bars assigned to the data. A significant aspect of the validation of spectra, and a detailed characterization of the X-ray tubes, involved measuring filtered and unfiltered beams at multiple tube potentials (30–150 kVp). Full corrections to ion chamber readings were employed to convert normalized fluence spectra into absolute fluence spectra. The characterization of fixed anode pitting and its dominance over exit window plating and/or detector dead layer was determined. An Appendix of tabulated benchmark spectra with assigned error ranges was developed for future reference.