Radiology curriculum for medical students: clinicians' perspectives

This study was conducted to establish clinicians' perspectives of a set of radiology curriculum topics for medical student teaching, which were held to be important by radiologists. A questionnaire was sent to clinicians in all specialties. Forty-six clinicians (51.1%) out of 90 returned the questionnaires. All curriculum topics were scored above an average of 4 (agree). The five highest ranking curriculum topics in order of importance were: developing a system for viewing chest radiographs (5.59), developing a system for viewing abdominal radiographs (5.56), developing a system for viewing bone and joint radiographs (5.33), distinguishing normal structures from abnormal in chest and abdominal radiographs (5.33) and identifying gross bone or joint abnormalities in skeletal radiographs (5.22). Correlative analysis between speciality groups showed surgical and medical specialities were significantly different in their responses of two learning outcomes: basic knowledge about the contrast media benefits and risks (P= 0.01) and ability to select the most appropriate and the most cost-effective methods of radiological investigations for clinical situations (P= 0.03). Acute specialities were not significantly different from the other two groups for these two learning outcomes. There was no statistically significant difference for other learning outcomes between the three speciality groups.     

Flexural strength of glass fibre‐reinforced posts bonded to dual‐cure composite resin cements

Davis P, Melo LSD, Foxton RM, Sherriff M, Pilecki P, Mannocci F, Watson TF. Flexural strength of glass fibre‐reinforced posts bonded to dual‐cure composite resin cements. Eur J Oral Sci 2010; 118: 197–201. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci The aims of this study were to evaluate the flexural strength of two different types of glass fibre‐reinforced posts bonded to dual‐cure composite resin cements. Forty glass methacrylate‐based fibre posts (GC Fiber Post) and 20 glass fibre inter‐polymerizing network posts (everStick POST) were divided into three groups. Group 1 contained 20 GC posts that were bonded to a dual‐cure composite cement (UnifilCore). Group 2 contained 20 Stick Tech posts that had adhesive applied (Scotchbond Multipurpose resin) and were bonded to a dual‐cure composite resin cement (RelyX Unicem). Group 3 contained 20 GC posts that were pretreated with a silane‐coupling agent before being treated with resin and composite, as in group 1. A 4‐point bend test was carried out to failure on all of the groups. Failure modes were determined using scanning electron microscopy. Pretreatment of the post surface with the silane‐coupling agent did not increase the flexural strength. The flexural strength of the Stick Tech post was significantly lower than the flexural strength of the GC post. The mode of failure for the GC Posts was adhesive, whereas the Stick Tech posts failed cohesively. Different flexural strengths and failure modes were observed among the two fibre post–resin systems.     

Properties of crimpable archwire hooks: a laboratory investigation

The aim of the present study was to utilize a strain gauge, which enabled the force applied to produce firmly attached crimpable hooks to rectangular stainless steel arch wires, to be measured. In vitro testing of two hooks, American Orthodontic (AO) and TP Orthodontic (TP), and two dimensions of stainless steel archwire, 0.019 x 0.025 and 0.018 x 0.025-inch, was carried out using an Instron Universal Testing machine. The results demonstrate that there was a significant difference in the behaviour of the two types of crimpable hooks, with almost twice the force needed to dislodge the TP hooks compared with the AO hooks (11.7 and 6.22 N, respectively). When using TP hooks attached to either 0.019 x 0.025 or 0.018 x 0.025-inch stainless steel wires, the archwire size makes little difference to the force required to produce movement. The clinical significance of these findings is discussed.     

Flexural Properties and Surface Finishing of Acetal Resin Denture Clasps

PURPOSE: This study examined flexural properties of acetal resin to determine the appropriate design for an acetal resin removable partial denture clasp. The effectiveness of various acetal resin polishing procedures was also evaluated using scanning electron microscopy. MATERIALS AND METHODS: Loads of up to 1,500 g were applied to cylindrical acetal resin specimen lengths of 5, 10, and 15 mm, and the degree of deflection of the specimen tip was measured. Specimens were 2 mm and 1.5 mm in diameter with a round cross-section (R2 and R1.5, respectively), as well as 2 mm in diameter and half-round in cross-section. Half-round specimens were loaded with their flat surface vertical and then horizontal (HRV and HRH, respectively). Contour plots showing load and deflection for varying lengths of resin were developed for each cross-sectional type based on specimen length, and the stiffness was calculated. Additional acetal resin specimens underwent polishing techniques including tungsten carbide burs, aluminium oxide stones, abrasive impregnated rubber points, and "Polish-D." Polished specimens were examined with scanning electron microscopy to compare surface roughness. RESULTS: For the 5-mm-length specimens, the median stiffness values decreased in the following order: R2 > HRV > HRH > R1.5. The median stiffness values for the 10-mm and 15-mm lengths followed a similar trend. At each length, the R2 specimen was generally at least twice as stiff as other designs. Regarding polishing, the smoothest surface was seen on the specimen that was polished with the rubber point followed by "Polish-D." CONCLUSIONS: To have stiffness similar to a cast cobalt-chromium clasp 15 mm long and 1 mm in diameter, a suitable acetal resin clasp must be shorter (approximately 5 mm) with greater cross-sectional diameter (approximately 1.4 mm). To obtain a smooth surface, the acetal resin clasp should be polished with a rubber point followed by a material such as "Polish-D."     

Artificial neural networks as statistical tools in epidemiological studies: analysis of risk factors for early infant wheeze

Artificial neural networks (ANNs) are being used increasingly for the prediction of clinical outcomes and classification of disease phenotypes. A lack of understanding of the statistical principles underlying ANNs has led to widespread misuse of these tools in the biomedical arena. In this paper, the authors compare the performance of ANNs with that of conventional linear logistic regression models in an epidemiological study of infant wheeze. Data on the putative risk factors for infant wheeze have been obtained from a sample of 7318 infants taking part in the Avon Longitudinal Study of Parents and Children (ALSPAC). The data were analysed using logistic regression models and ANNs, and performance based on misclassification rates of a validation data set were compared. Misclassification rates in the training data set decreased as the complexity of the ANN increased: h = 0: 17.9%; h = 2: 16.2%; h = 5: 14.9%, and h = 10: 9.2%. However, the more complex models did not generalise well to new data sets drawn from the same population: validation data set misclassification rates: h = 0: 17.9%; h = 2: 19.6%; h = 5: 20.2% and h = 10: 22.9%. There is no evidence from this study that ANNs outperform conventional methods of analysing epidemiological data. Increasing the complexity of the models serves only to overfit the model to the data. It is important that a validation or test data set is used to assess the performance of highly complex ANNs to avoid overfitting.     

An in vivo and ex vivo study to evaluate the use of a glass polyphosphonate cement in orthodontic banding

The purpose of this study was to examine the effectiveness of a new glass polyphosphonate cement (Diamond) for orthodontic banding. Thirty-one subjects underwent in vivo testing to compare the failure rate of bands cemented using the test cement and bands cemented using a conventional glass polyalkenoate cement (Ketac-Cem) over a 6-month period at the beginning of active appliance therapy. In an ex vivo experiment 60 extracted teeth were banded using either the test cement or a glass polyalkenoate cement, and subjected to a debanding force using a Lloyd universal testing machine until failure. In the in vivo study the overall proportion of failure of the bands cemented with each cement was identical at 0.048. However, in the ex vivo study the probability of failure for the glass polyphosphonate cement was significantly higher than for the glass polyalkenoate cement, and the force to deband the glass polyalkenoate cement was greater than that of the glass polyphosphonate cement. In the clinical setting the new glass polyphosphonate cement performed as well as a conventional glass polyalkenoate cement, and these results suggest that it could be used as an alternative cement for orthodontic banding. The results of the ex vivo test bring into question the usefulness of this laboratory test as an indicator of clinical performance.     

Early detection of axonal injury after human head trauma using immunocytochemistry for β-amyloid precursor protein

Severe non-missile head injury commonly results in a form of brain damage known as diffuse axonal injury (DAI). The histological diagnosis of DAI is made by silver staining for the presence of axonal retraction balls. This feature takes about 24 h to develop and does not allow for the early histological diagnosis of DAI. We have used immunocytochemistry for the -amyloid precursor protein (APP) as a marker for axonal injury in formalin-fixed, paraffin-embedded sections of human brain. Axonal APP immunoreativity was present in all cases which had survived for 3 h or more. This was true even where the degree of head injury did not appear to be severe, supporting the theory that DAI is a severe form of a more common phenomenon of axonal injury which occurs after cerebral trauma. APP immunoreactivity was also found in some non-head injured cases and so cannot be considered to be a specific marker for trauma. The results show that APP immunocytochemistry may be useful in the detection of traumatic axonal injury in its early stages, before the formation of axonal retraction balls, provided care is taken to exclude other causes of such immunoreactivity.Supported by the Home Office Policy Advisory Board for Forensic Pathology (UK)