Philip D. Allen

Tooth loss and osteoporosis: the OSTEODENT Study

AIM To determine the cross-sectional association of the osteoporotic status of patients with the number of their teeth, with and without taking into account age and/or smoking. MATERIAL & METHODS At four centres, the study recruited 665 females aged 45-70 years and the number of teeth was counted for 651 subjects. Bone density was measured at the total hip, femoral neck and lumbar spine. RESULTS The mean number of teeth in the osteoporotic subjects was 3.3 fewer than normal subjects and 2.1 fewer if those with no teeth were excluded. The association between osteoporosis and having <6 or having <28 teeth remained significant after adjusting for age, smoking and centre with p-values of 0.016 and 0.011, respectively. A single regression model for tooth count with normal errors would not fit all the data. By fitting mixture regression models to subjects with tooth count >0, three clusters were identified corresponding to different degrees of tooth loss. The overall effect of osteoporosis was as follows: -1.8 teeth before and after adjusting for smoking, -1.2 teeth after adjusting for age, and -1.1 teeth after adjusting for both age and smoking. CONCLUSIONS We have established a significant association between osteoporosis and tooth loss after adjusting the effect for age and smoking.

Detecting Reduced Bone Mineral Density From Dental Radiographs Using Statistical Shape Models

We describe a novel method of estimating reduced bone mineral density (BMD) from dental panoramic tomograms (DPTs), which show the entire mandible. Careful expert width measurement of the inferior mandibular cortex has been shown to be predictive of BMD in hip and spine osteopenia and osteoporosis. We have implemented a method of automatic measurement of the width by active shape model search, using as training data 132 DPTs of female subjects whose BMD has been established by dual-energy X-ray absorptiometry. We demonstrate that widths measured after fully automatic search are significantly correlated with BMD, and exhibit less variability than manual measurements made by different experts. The correlation is highest towards the lateral region of the mandible, in a position different from that previously employed for manual width measurement. An receiver-operator characteristic (ROC) analysis for identifying osteopenia (T < - 1: BMD more than one standard deviation below that of young healthy females) gives an area under curve (AUC) value of 0.64. Using a minimal interaction to initiate active shape model (ASM) search, the measurement can be made at the optimum region of the mandible, resulting in an AUC value of 0.71. Using an independent test set, AUC for detection of osteoporosis (T < -2.5) is 0.81.

The role of the dental surgeon in detecting osteoporosis: the OSTEODENT study

Objective To determine if thinning (<3 mm width) of the lower cortical border of the mandible on dental panoramic radiographs, as well as other clinical risk factors, may provide a useful diagnostic test for osteoporosis in young postmenopausal women.Design Six hundred and fifty-two subjects (age range 45-70 years) were involved in this multi-centre, cross-sectional study.Setting Patients were recruited from centres in Leuven (Belgium), Athens (Greece), Manchester (UK), and Malmo (Sweden).Subjects and methods The subjects age, body weight, whether the patient took hormone replacement therapy or had a history of low trauma fracture were used to form a clinical osteoporosis risk assessment (the OSteoporosis Index of RISk or OSIRIS index). Each patient also received a dental panoramic radiographic examination.Results One hundred and forty subjects had osteoporosis involving at least one of the measurement sites (lumbar spine, femoral neck or total hip). Those with osteoporosis tended to have a low OSIRIS score and a thinned cortical mandibular border. The area under the ROC curve for using both cortical width and OSIRIS to predict osteoporosis was 0.90 (95% CI = 0.87 to 0.92). There was a significant improvement in the diagnostic ability of the combined OSIRIS and cortical width test over both tests applied separately (p <0.001). The cost effectiveness of the cortical width and OSIRIS model was improved by using a high specificity threshold rather than high sensitivity. However, this analysis ignores the costs associated with missed cases of osteoporosis.Conclusion Dentists have a role to play in the detection and referral of patients at high risk of osteoporosis.

Image Analysis of Nailfold Capillary Patterns from Video Sequences

Video capillaroscopy is a widely used technique to assess the condition of the blood capillaries in the nailfold of patients suffering from reduced peripheral circulation (Raynaud’s phenomenon). This approach is complicated by the fact that gaps in the flow of blood can render capillaries incomplete in any single video frame. This paper describes a computer based system in which sequences of video frames are registered and combined to provide a composite image for analysis. We show that the images can be registered to an accuracy of approximately 2 μm, and that temporally variable features can be enhanced significantly by subtracting one standard deviation from the mean value for each pixel position in the video sequence.

Differential segmentation of the prostate in MR images using combined 3D shape modelling and voxel classification

Benign prostatic hyperplasia (BPH) is a non-cancerous expansion of the prostate, the progress of which can be quantified by measuring the relative volumes of the prostates peripheral zone and central gland. Here we describe a method of automatic segmentation of both regions of the prostate from MR images using a combination of grey-level voxel classification and 3D statistical shape modelling

Enhancement of Temporally Variable Features in Nailfold Capillary Patterns

Analysis of the condition of blood capillaries in the nailfold is complicated by the fact that gaps in the flow of blood cells results in temporal variability in their appearance. At a single instant the capillaries may be incomplete, but integration of the information from several successive video frames renders the whole capillary visible. This paper shows that combining the information from the video frame sequence by subtracting a multiple of the standard deviation from the mean value for each pixel, improves the signal to noise ratio of variable features when compared with the mean image or using minimum projection.

A cue generator for crack detection

Abstract This paper describes a computationally efficient method for identifying weakly visible cracks in images of man-made surfaces. The method relies on a multistage nonlinear filtering process designed to yield maximum response to symmetrical fine structure. The result is a set of candidate sites which can then be verified on the basis of features obtained from the source image and candidate shape. Results are presented which demonstrate the application of the method to a difficult problem in industrial inspection.

Microvascular Dynamics in the Nailfolds of Scleroderma Patients Studied Using Na-fluorescein Dye

Dynamic microscopy of the nailfold capillaries using Nafluorescein dye can be used to assess the condition of the peripheral circulation of Scleroderma patients, yielding more information than simple morphological studies. In this paper we describe a computer based system for this kind of study and present preliminary results on Scleroderma patients. We show how the dye concentrations vary both in time and as a function of distance from the capillary wall in unprecedented resolution, suggesting that a simple permeability model may be applicable to the data.