Change in mandibular trabecular pattern and hip fracture rate in elderly women.

OBJECTIVES: To determine if alterations of trabecular pattern, or the rate of change of jaw trabeculae, are associated with rate of hip fracture. METHODS: Participants in a population-based study of residents of a California retirement community (Leisure World Cohort Study) were asked for permission to obtain their dental radiographs. Periapical radiographs were retrieved on 598 women (average age at time of first radiograph=77 years). Several measurements of trabecular pattern (strut analysis), textural properties (run-length analysis) and Fourier analysis were made in several anatomical regions of the jaw. These trabecular features and clinical information self-reported by subjects in the early 1980s were examined for association with hip fracture rate using Cox proportional-hazard regression. RESULTS: Rate of hip fracture increased with decreasing average length of node-to-terminus struts in the mandibular incisor region. Each 0.01 mm per year decrease in the average length of node-to-terminus struts increased hip fracture rate by a factor of 2.9 (P=0.02, accuracy=73%). Inclusion of clinical parameters improved the predictive model compared with use of the radiographic parameter alone (accuracy=79%). Similar results were seen for percent change per year in this parameter. CONCLUSIONS: Changes in radiographic trabecular structure, augmented with clinical information, are predictive of hip fracture in elderly women. Further refinement of both the radiographic and clinical parameters may lead to a screening process accessible to a large number of women and to early diagnosis and treatment of osteoporosis.

Ultrasound crack detection in a simulated human tooth.

OBJECTIVE: Currently, diagnosis of cracked teeth generally depends upon the overall clinical assessment, or on exclusion of other clinical possibilities, not primarily on the direct identification of cracks themselves. Owing to its short wavelength in hard tissues and associated high resolution, ultrasound has the potential to allow detection of cracks within tooth structure. However, ultrasound detection of dental cracks has not previously been achieved. The purpose was to determine if an ultrasound imaging system was capable of imaging cracks in simulated tooth structure. METHODS: A complete ultrasound system including a novel transducer made of PLZT-98, a novel gallium-indium alloy coupling agent, and customized electronic and digital signal processing (DSP) algorithms was developed for the specific application of optimizing crack detection within teeth. A simulated tooth with a known and uniform internal structure and acoustic properties similar to those of natural enamel and dentin was designed to model a human tooth with a crack located in dentin deep to the dentino-enamel junction (DEJ). The distance between the DEJ and a crack of the simulated tooth were calculated. RESULTS: The system unequivocally distinguished between areas with and without a simulated crack. CONCLUSION: A unique ultrasound dental crack detection system using a novel transducer; a novel coupling agent; and customized electronic and digital signal processing (DSP) algorithms has been validated in a simulated tooth.

Imaging of human tooth enamel using ultrasound.

This paper reports the results of a complete circumferential scan of a human tooth and its underlying dentino-enamel junction using ultrasound at frequencies in the 10-MHz range. The imagery shows clearly a two-dimensional contour of the dentinoenamel junction with a depth and lateral resolution of approximately 100 microm and 750 microm, respectively. The resulting sonograph is compared with an optical micrograph of the same tooth to verify the accuracy of the ultrasonic technique. The results are a significant step toward the biolocation of submillimeter size features within the tooth volume.

Fourier analysis reveals increased trabecular spacing in sickle cell anemia.

Sickle cell anemia may expand marrow spaces in the jaws. Fourier analysis is well-suited to the analysis of trabecular spacing in radiographs. We hypothesize that individuals with sickle cell anemia demonstrate increased intertrabecular spacing. Periapical radiographs of 18 African Americans with sickle cell disease and 18 controls were examined by one-dimensional discrete Fourier analyses in both jaws for measurement of the spatial frequency distribution of repeating trabecular structures. A strut analysis of trabeculae was also performed and the results compared. Trabecular structures in individuals with sickle cell anemia revealed increased intertrabecular distance compared with controls. Strut analysis revealed significant reductions in trabecular complexity. Fourier analysis allows for the classification of subjects with 94% sensitivity and specificity. Fourier analysis of dental radiographs is a more effective method of identifying individuals with sickle cell anemia than strut analysis.

A new method for the automated alignment of dental radiographs for digital subtraction radiography.

OBJECTIVES: To provide a robust and convenient method by which radiographic images can be spatially aligned for digital radiographic subtraction without the use of manually selected reference points. METHODS: An automated method for image alignment is described which begins with the extraction of a large number of edge features (1500 or more pixels) from each of two radiographic images taken of the same anatomical region of a given patient. The features in the first radiograph are paired, pixel by pixel, with those in the second radiograph using a nearest neighbor criterion. The edge features in the first radiograph are aligned with those in the second radiograph by performing an affine transformation that is consistent with the projection geometry for a plantar parallel X-ray beam. Transformation parameters are determined which provide the smallest spatial alignment error between the two sets of equivalent features. These parameters are found by a closed-form analytic solution, thus enabling a computationally efficient implementation. The final transformation is then applied to the entire first image resulting in a close spatial match to the second image. The performance of three dentists using the automatic method was compared with their performance using a manual method of alignment for eight pairs of images. RESULTS: The root mean squared error in image alignment for the automatic method was 14% lower than that with manual alignment. The variability for the automatic method was half that of the maximal method as measured by the residual error. The automatic method was also three times faster than the manual method. CONCLUSIONS: This method could make digital subtraction more accessible to researchers and practising dentists. Batch mode implementation could enable the processing of large volumes of data. Restriction to a region of interest and improved feature extraction could further improve performance.

Comparison of sensitometric and diagnostic performance of two films.

The sensitometric properties of Kodak Ektaspeed Plus and Flow E-speed film as well as their diagnostic efficacy for detecting proximal surface caries were compared. Flow and Kodak E-speed films were exposed and processed according to American National Standards Institute and American Dental Association (ADA) specifications, and film speed, contrast, and density of base plus fog were measured. Additionally, 80 premolar and molar teeth were imaged and their proximal surfaces scored by 12 dentists for the presence of caries. The actual depth of the caries was determined by microscopic examination of the teeth after sectioning. Kodak Ektaspeed Plus and Flow E-speed films, although labeled E-speed by the manufacturers, are both slow F-speed films. They have comparable base plus fog densities and comparable contrast curves. Dentists detected carious lesions equally well using both film types. The sensitivity, specificity, accuracy, and receiver operating characteristic area for detecting enamel and dentinal caries were not significantly different between the two films. Kodak Ektaspeed Plus and Flow E-speed films both meet or exceed the ADA performance specifications in terms of sensitometric properties. Both offer equal diagnostic utility for detecting caries.

Digital radiography in dentistry: what it should do for you.

Digital radiology will become an important part of dental practice. Manufacturers should develop more sophisticated tools, including software for digital subtraction; image processing routines for the diagnosis of caries, periodontitis and periapical disease; tools for three-dimensional viewing of the teeth and supporting structures; and analysis of bone trabecular pattern for early detection of systemic disease. Hardware improvements should include increased dynamic range and sensitivity to radiation, and improved resolution. Sensors should be made the size of film, and components should be interchangeable across manufacturers. The true opportunity offered by digital imaging, computer-aided diagnosis, should continue to develop with particular attention to development of tools that add value for solving diagnostic problems and ease of use for the dentist and patient.

Comparative performance of digital and conventional images for detecting proximal surface caries.

OBJECTIVE: To evaluate the performance of a digital CCD system for detecting proximal surface caries compared with film. METHOD: Three hundred and twenty extracted human teeth were imaged by making direct digital (Schick Technologies, Inc) and conventional film images (E-speed) of each. A total of 16 experienced dentists scored the proximal surfaces of these teeth for the extent of enamel and dentin lesions. The teeth were subsequently sectioned to determine the actual caries depth. RESULTS: The sensitivity of the CCD system was consistently lower than film while the specificity of the CCD system was consistently higher. The accuracy of CCD and film images was not significantly different, neither when sensitivity and specificity were averaged nor when accuracy was weighted to reflect caries prevalence of 2, 5 or 10%. The predictive values of both positive/negative outcomes were virtually identical for the CCD and film images. The interrater variability in lesion confidence scores with digital images was comparative with film. CONCLUSIONS: Dentists using a direct digital CCD system performed as well in interpreting proximal surface caries as with E-speed film. This work suggests that for this task these two competing systems are diagnostically comparable.