Shape-driven solid-solid transitions in colloids.

Solid-solid phase transitions are the most ubiquitous in nature, and many technologies rely on them. However, studying them in detail is difficult because of the extreme conditions (high pressure/temperature) under which many such transitions occur and the high-resolution equipment needed to capture the intermediate states of the transformations. These difficulties mean that basic questions remain unanswered, such as whether so-called diffusionless solid-solid transitions, which have only local particle rearrangement, require thermal activation. Here, we introduce a family of minimal model systems that exhibits solid-solid phase transitions that are driven by changes in the shape of colloidal particles. By using particle shape as the control variable, we entropically reshape the coordination polyhedra of the particles in the system, a change that occurs indirectly in atomic solid-solid phase transitions via changes in temperature, pressure, or density. We carry out a detailed investigation of the thermodynamics of a series of isochoric, diffusionless solid-solid phase transitions within a single shape family and find both transitions that require thermal activation or are "discontinuous" and transitions that occur without thermal activation or are "continuous." In the discontinuous case, we find that sufficiently large shape changes can drive reconfiguration on timescales comparable with those for self-assembly and without an intermediate fluid phase, and in the continuous case, solid-solid reconfiguration happens on shorter timescales than self-assembly, providing guidance for developing means of generating reconfigurable colloidal materials.

Study protocol: families and childhood transitions study (FACTS) - a longitudinal investigation of the role of the family environment in brain development and risk for mental health disorders in community based children.

BACKGROUND: Extant research has demonstrated that parenting behaviour can be a significant contributor to the development of brain structure and mental health during adolescence. Nonetheless, there is limited research examining these relationships during late childhood, and particularly in the critical period of brain development occurring between 8 and 10 years of age. The effects of the family environment on the brain during late childhood may have significant implications for later functioning, and particularly mental health. The Families and Childhood Transitions Study (FACTS) is a multidisciplinary longitudinal cohort study of brain development and mental health, with two waves of data collection currently funded, occurring 18-months apart, when child participants are aged approximately 8- and 10-years old. METHODS/DESIGN: Participants are 163 children (M age [SD] = 8.44 [0.34] years, 76 males) and their mothers (M age [SD] = 40.34 [5.43] years). Of the 163 families who consented to participate, 156 completed a video-recorded and observer-coded dyadic interaction task and 153 completed a child magnetic resonance imaging brain scan at baseline. Families were recruited from lower socioeconomic status (SES) areas to maximise rates of social disadvantage and variation in parenting behaviours. All experimental measures and tasks completed at baseline are repeated at an 18-month follow-up, excluding the observer coded family interaction tasks. The baseline assessment was completed in October 2015, and the 18-month follow up will be completed May 2017. DISCUSSION: This study, by examining the neurobiological and mental health consequences of variations in parenting, has the potential to significantly advance our understanding of child development and risk processes. Recruitment of lower SES families will also allow assessment of resilience factors given the poorer outcomes often associated with this population.

Role of isostaticity and load-bearing microstructure in the elasticity of yielded colloidal gels.

We report a simple correlation between microstructure and strain-dependent elasticity in colloidal gels by visualizing the evolution of cluster structure in high strain-rate flows. We control the initial gel microstructure by inducing different levels of isotropic depletion attraction between particles suspended in refractive index matched solvents. Contrary to previous ideas from mode coupling and micromechanical treatments, our studies show that bond breakage occurs mainly due to the erosion of rigid clusters that persist far beyond the yield strain. This rigidity contributes to gel elasticity even when the sample is fully fluidized; the origin of the elasticity is the slow Brownian relaxation of rigid, hydrodynamically interacting clusters. We find a power-law scaling of the elastic modulus with the stress-bearing volume fraction that is valid over a range of volume fractions and gelation conditions. These results provide a conceptual framework to quantitatively connect the flow-induced microstructure of soft materials to their nonlinear rheology.

Comparison between landmark and surface-based three-dimensional analyses of facial asymmetry in adults.

BACKGROUND/OBJECTIVES: To collect the reference values for facial asymmetry in adults using landmark and surface-based three-dimensional analyses and to compare their diagnostic abilities. MATERIALS AND METHODS: Laser scans were taken from 85 British Caucasians, 29 males (23.9±5.7 years, range 19-44) and 56 females (28.1±9.5 years, range 19-54), students and staff of the Cardiff Dental Hospital, and three orthodontic patients with marked facial asymmetry. An asymmetry index (AI) was measured for 14 landmarks. The surface-to-surface average distance between the best-fit registered original and mirror scans (ADom) was measured for the whole face and six regions. Non-parametric descriptive statistics was used to obtain the reference values, and Mann-Whitney U-test was used for gender comparison. P values less than 0.05 were considered significant. Patients' values were compared to the reference values by calculating the corresponding percentiles. RESULTS: The lowest AI was found for 'pronasale' in males [median 0.1 (interquartile range 0.0-0.3) mm] and the highest for 'cheilion' [3.5 (2.4-5.0) mm] in females. The ADom for the whole face was 0.7 (0.5-0.9) mm in males and 0.6 (0.5-0.7) mm in females and regionally between 0.4 (0.3-0.6) mm and 0.8 (0.4-1.2) mm. In orthodontic patients, AI did not always reveal asymmetry in a particular coordinate plane, and surface-based analysis was favourable in regions underrepresented by landmarks. CONCLUSIONS: Facial asymmetry can be accurately quantified using landmark- and surface-based approaches. The latter offers a more comprehensive analysis of the face.

A pitfall in the reconstruction of fibre ODFs using spherical deconvolution of diffusion MRI data.

Diffusion weighted (DW) MRI facilitates non-invasive quantification of tissue microstructure and, in combination with appropriate signal processing, three-dimensional estimates of fibrous orientation. In recent years, attention has shifted from the diffusion tensor model, which assumes a unimodal Gaussian diffusion displacement profile to recover fibre orientation (with various well-documented limitations), towards more complex high angular resolution diffusion imaging (HARDI) analysis techniques. Spherical deconvolution (SD) approaches assume that the fibre orientation density function (fODF) within a voxel can be obtained by deconvolving a 'common' single fibre response function from the observed set of DW signals. In practice, this common response function is not known a priori and thus an estimated fibre response must be used. Here the establishment of this single-fibre response function is referred to as 'calibration'. This work examines the vulnerability of two different SD approaches to inappropriate response function calibration: (1) constrained spherical harmonic deconvolution (CSHD)--a technique that exploits spherical harmonic basis sets and (2) damped Richardson-Lucy (dRL) deconvolution--a technique based on the standard Richardson-Lucy deconvolution. Through simulations, the impact of a discrepancy between the calibrated diffusion profiles and the observed ('Target') DW-signals in both single and crossing-fibre configurations was investigated. The results show that CSHD produces spurious fODF peaks (consistent with well known ringing artefacts) as the discrepancy between calibration and target response increases, while dRL demonstrates a lower over-all sensitivity to miscalibration (with a calibration response function for a highly anisotropic fibre being optimal). However, dRL demonstrates a reduced ability to resolve low anisotropy crossing-fibres compared to CSHD. It is concluded that the range and spatial-distribution of expected single-fibre anisotropies within an image must be carefully considered to ensure selection of the appropriate algorithm, parameters and calibration. Failure to choose the calibration response function carefully may severely impact the quality of any resultant tractography.

Three-dimensional analysis of facial shape and symmetry in twins using laser surface scanning.

OBJECTIVES: Three-dimensional analysis of facial shape and symmetry in twins. SETTING AND SAMPLE POPULATION: Faces of 37 twin pairs [19 monozygotic (MZ) and 18 dizygotic (DZ)] were laser scanned at the age of 15 during a follow-up of the Avon Longitudinal Study of Parents and Children (ALSPAC), South West of England. MATERIAL AND METHODS: Facial shape was analysed using two methods: 1) Procrustes analysis of landmark configurations (63 x, y and z coordinates of 21 facial landmarks) and 2) three-dimensional comparisons of facial surfaces within each twin pair. Monozygotic and DZ twins were compared using ellipsoids representing 95% of the variation in landmark configurations and surface-based average faces. Facial symmetry was analysed by superimposing the original and mirror facial images. RESULTS: Both analyses showed greater similarity of facial shape in MZ twins, with lower third being the least similar. Procrustes analysis did not reveal any significant difference in facial landmark configurations of MZ and DZ twins. The average faces of MZ and DZ males were coincident in the forehead, supraorbital and infraorbital ridges, the bridge of the nose and lower lip. In MZ and DZ females, the eyes, supraorbital and infraorbital ridges, philtrum and lower part of the cheeks were coincident. Zygosity did not seem to influence the amount of facial symmetry. Lower facial third was the most asymmetrical. CONCLUSION: Three-dimensional analyses revealed differences in facial shapes of MZ and DZ twins. The relative contribution of genetic and environmental factors is different for the upper, middle and lower facial thirds.

Determining normal and abnormal lip shapes at border positions for use as a longitudinal surgical outcome measure.

Objective measures of facial movement are important for interventions where surgical repositioning of facial structures can influence soft tissue mobility and include the management of patients with cleft lip, facial nerve palsy and orthognathic surgery. As such, the aim of this study is to present a method for determining the outcome of surgical procedures on lip shape during speech. A control group (CG) of 115 average subjects and 30 patients with a Class 3 malocclusion requiring bimaxillary surgery performed four reproducible verbal utterances during image capture using a non-invasive, three-dimensional (3D) motion scanner (3dMDFace™ Dynamic System). Landmark coordinates around the lips of the 3D facial shells were extracted and subjected to discriminant analysis and principal component analysis to statistically differentiate lip shapes between the CG and the patient group (PG) pre- and post-surgery. Pre-surgically, the PG showed statistically significant differences in lip shape during speech in the lateral and vertical dimensions, preferring a wider, shorter lip shape when compared with the CG for all the utterances. The shape differences normalised towards the CG post-surgery. The method presented utilises pre-existing statistical shape analyses and can be reproduced in the clinical setting to provide a diagnostic and functional outcome tool. In this example, correction of the Class 3 skeletal disproportions appeared to normalise lip shape during speech.

Building Flavor and Confidence in the Kitchen: A Pilot Virtual Cooking Class on Healthy Snacking.

Cooking meals at home is associated with more healthful eating and even other healthy behaviors, such as increased physical activity, but for many there are numerous barriers to making this a reality. Healthy teaching kitchen interventions aim to help patients overcome these barriers. Our pilot program worked to address this issue by demonstrating the feasibility and acceptability of a virtual culinary medicine session designed for outpatient clinic patients. Participants were recruited from a single community primary care clinic for a virtual culinary medicine session. Of the 29 subjects who attended the class, 13 (45%) filled out the pre-course survey, and 8 (26%) filled out the post-course survey. Average participant confidence in preparing snacks at home from fresh ingredients increased from 3.62 to 4.38 out of 5 after attending this session, though the results were not statistically (OR .47; P = .172; 95% CI .16 to 1.3). Post-participation comments were overwhelmingly positive. This study showed that a virtual cooking class is feasible in a community clinic setting and is positively received. In addition, a culinary class teaching healthy cooking techniques paired with nutrition training may improve patient's confidence in the kitchen.

Assessment of facial asymmetry in growing subjects with a three-dimensional laser scanning system.

OBJECTIVES: To evaluate facial asymmetry in growing subjects with no malocclusion on three-dimensional laser facial scans. SETTING AND SAMPLE POPULATION: Twenty-seven healthy Caucasian children (15 boys and 12 girls, aged 5.4 ± 0.3 years) in the primary dentition without malocclusion were randomly selected from a local kindergarten in Slovenia. MATERIAL AND METHODS: Surface facial images were obtained using a three-dimensional laser scanning system at baseline and at 18, 30, 42 and 54 months of follow-up. Facial asymmetry was assessed quantitatively by measuring the average distance between facial image and mirrored image. Further, the percentage of asymmetry was calculated as the percentage of image to mirrored image not coinciding within 0.5 mm. Qualitative assessment was performed on colour deviation maps by recording the predominant side of the face for the upper, middle and lower parts of the face separately. Nonparametric tests were used for data analysis. RESULTS: No face was perfectly symmetric. The average distance between the mirrored images for the whole face ranged 0.22-0.85 mm and the percentage of asymmetry 7.8-66.9. There were no significant gender differences (p > 0.05), and no significant change was found over the observed period. The upper part of the face was the least asymmetric, while the lower and middle parts showed similar degrees of asymmetry. CONCLUSION: Facial asymmetry is already present at an early developmental stage and does not show any tendency to increase or decrease with growth in the pre-pubertal period.

Statistical modelling of lip movement in the clinical context.

OBJECTIVE: To establish three-dimensional (3D) reference data on average lip movement in normal healthy subjects using statistical shape analysis techniques. SETTING AND SAMPLE POPULATION: School of Dentistry and Cardiff School of Computer Science, Cardiff University, United Kingdom. One hundred and fifteen white subjects. MATERIAL AND METHODS: Subjects performed four reproducible verbal gestures (puppy, rope, baby and bob) in a normal relaxed manner, which were captured using a non-invasive, 3D motion scanner (3dMDFace™ Dynamic System). Six landmarks were manually placed around the lips of the 3D facial shells showing maximum lip displacement. Generalized procrustes analysis followed by principal component analysis was applied to the landmark coordinates to characterize lip movement for each word. RESULTS: The first four principal components (PCs) describe the majority of variation in lip movement for the four words involving a complex interaction of lip movements in three dimensions. Bilateral landmarks were paired within PCs showing that movement was largely symmetrical. Female resting lip shape was narrower and shorter in height than males. During motion, females preferred a more protrusive articulation than males. CONCLUSION: Statistical shape analysis techniques can be used to characterize lip movement during articulation. Data from this study can act as a reference for average lip movement to compare similar population groups.

Parametric study of a Hill-type hyperelastic skeletal muscle model.

Hill's one-dimensional three-element model has often been used for formulating a three-dimensional skeletal muscle constitutive model, which generally involves several material parameters. However, only few of these parameters have physical meanings and can be experimentally determined. In this paper, a parametric study of a Hill-type hyperelastic skeletal muscle model is performed. First, the Hill-type hyperelastic skeletal muscle model is formulated, containing 13 material parameters. The values or value ranges of these parameters are discussed. The muscle model is then used to predict the behaviour of New Zealand white rabbit hind leg muscle tibialis anterior and a sensitivity study of several parameters is performed. Results show that some parameters in the muscle model can be experimentally determined, some parameters have their own value ranges and the muscle model can predict the experimental data by tuning the parameters within their value ranges. The results from the sensitivity study can help understand how some parameters influence the total muscle stress.

Effects of dual-tasking on time-to-boundary during stance in people with PD: A preliminary study.

BACKGROUND: Quiet stance is impacted by Parkinson's disease and dual-tasking. Recently developed outcomes such as the time-to-boundary provide unique insight into balance by integrating center of pressure position with base of support. However, little is known about the effects of Parkinson's disease on time-to-boundary. In particular, the effects of distracting cognitive tasks, and how people with Parkinson's disease prioritize balance and cognitive tasks are poorly understood. METHODS: 14 people with Parkinson's disease and 13 controls completed quiet standing and cognitive Stroop tasks separately (single-task) and together (dual-task). 2-dimentional, medio-lateral, and anterior-posterior time-to-boundary were calculated via force-plate data. Traditional sway outcomes, including sway area and path length, were also calculated. Cognitive performance was measured as the verbal reaction time after auditory stimulus delivery. Prioritization was assessed by taking the difference between cognitive and postural dual-task interference. FINDINGS: Time-to-boundary was worse in Parkinson's disease compared to controls (2-dimentional: p = .019; anterior-posterior: p = .062; medio-lateral: p = .012). Medio-lateral time-to-boundary, but not anterior-posterior, was significantly worse during dual-tasking than single-tasking (p = .024). Neurotypical adults tended to prioritize cognition over medio-lateral postural outcomes. INTERPRETATION: People with Parkinson's disease exhibit worse time-to-boundary than their neurotypical peers, and medio-lateral outcomes were sensitive to single to dual-task performance changes. Further, participants generally showed cognitive prioritization, such that cognitive performance was less impacted than medio-lateral postural outcomes by dual-tasking.

The Lunch Conference Diet: Fostering Resident Engagement in Culinary Medicine Through a Curriculum Centered on Changes to Provided Conference Food.

BACKGROUND: Despite the burden of chronic disease attributable to lifestyle, most internal medicine residents do not receive adequate training in nutrition and nutrition counseling. METHODS: We held a culinary medicine workshop in September 2018, followed by didactic sessions throughout the academic year. Changes were made to lunch conference food to more closely follow the Mediterranean diet and to encourage healthy eating. With a modified NUTCOMP (Nutrition Competence Questionnaire) instrument, we assesses residents' perceived competence with nutrition counseling before and after the curriculum. RESULTS: Twenty-six of 30 residents completed the pre-curriculum and post-curriculum surveys (not the same 26). The mean NUTCOMP score increased from 3.5 to 4.0 (P < .0001), indicating an increased perceived competence with nutritional counseling. Residents felt that nutritional counseling was important before and after the curriculum (4.2 to 4.3, P = .48). Conference food was more nutritious at the end of the intervention (Mediterranean diet score range 1-4 to 4-7) and residents enjoyed the food more. CONCLUSIONS: An innovative, multimodal nutrition curriculum centered on changes to catered lunch conference food improved resident's confidence with nutritional counseling. This could feasibly be integrated into other residency programs with supportive leadership and adequate training.

An exploration of adolescent facial shape changes with age via multilevel partial least squares regression.

BACKGROUND AND OBJECTIVES: Multilevel statistical models represent the existence of hierarchies or clustering within populations of subjects (or shapes in this work). This is a distinct advantage over single-level methods that do not. Multilevel partial-least squares regression (mPLSR) is used here to study facial shape changes with age during adolescence in Welsh and Finnish samples comprising males and females. METHODS: 3D facial images were obtained for Welsh and Finnish male and female subjects at multiple ages from 12 to 17 years old. 1000 3D points were defined regularly for each shape by using "meshmonk" software. A three-level model was used here, including level 1 (sex/ethnicity); level 2, all "subject" variations excluding sex, ethnicity, and age; and level 3, age. The mathematical formalism of mPLSR is given in an Appendix. RESULTS: Differences in facial shape between the ages of 12 and 17 predicted by mPLSR agree well with previous results of multilevel principal components analysis (mPCA); buccal fat is reduced with increasing age and features such as the nose, brow, and chin become larger and more distinct. Differences due to ethnicity and sex are also observed. Plausible simulated faces are predicted from the model for different ages, sexes and ethnicities. Our models provide good representations of the shape data by consideration of appropriate measures of model fit (RMSE and R2). CONCLUSIONS: Repeat measures in our dataset for the same subject at different ages can only be modelled indirectly at the lowest level of the model at discrete ages via mPCA. By contrast, mPLSR models age explicitly as a continuous covariate, which is a strong advantage of mPLSR over mPCA. These investigations demonstrate that multivariate multilevel methods such as mPLSR can be used to describe such age-related changes for dense 3D point data. mPLSR might be of much use in future for the prediction of facial shapes for missing persons at specific ages or for simulating shapes for syndromes that affect facial shape in new subject populations.

Multilevel principal components analysis of three-dimensional facial growth in adolescents.

BACKGROUND AND OBJECTIVES: The study of age-related facial shape changes across different populations and sexes requires new multivariate tools to disentangle different sources of variations present in 3D facial images. Here we wish to use a multivariate technique called multilevel principal components analysis (mPCA) to study three-dimensional facial growth in adolescents. METHODS: These facial shapes were captured for Welsh and Finnish subjects (both male and female) at multiple ages from 12 to 17 years old (i.e., repeated-measures data). 1000 "dense" 3D points were defined regularly for each shape by using a deformable template via "meshmonk" software. A three-level model was used here, namely: level 1 (sex/ethnicity); level 2, all "subject" variations excluding sex, ethnicity, and age; and level 3, age. The technicalities underpinning the mPCA method are presented in Appendices. RESULTS: Eigenvalues via mPCA predicted that: level 1 (ethnicity/sex) contained 7.9% of variation; level 2 contained 71.5%; and level 3 (age) contained 20.6%. The results for the eigenvalues via mPCA followed a similar pattern to those results of single-level PCA. Results for modes of variation made sense, where effects due to ethnicity, sex, and age were reflected in modes at appropriate levels of the model. Standardised scores at level 1 via mPCA showed much stronger differentiation between sex and ethnicity groups than results of single-level PCA. Results for standardised scores from both single-level PCA and mPCA at level 3 indicated that females had different average "trajectories" with respect to these scores than males, which suggests that facial shape matures in different ways for males and females. No strong evidence of differences in growth patterns between Finnish and Welsh subjects was observed. CONCLUSIONS: mPCA results agree with existing research relating to the general process of facial changes in adolescents with respect to age quoted in the literature. They support previous evidence that suggests that males demonstrate larger changes and for a longer period of time compared to females, especially in the lower third of the face. These calculations are therefore an excellent initial test that multivariate multilevel methods such as mPCA can be used to describe such age-related changes for "dense" 3D point data.

Phase stabilization by electronic entropy in plutonium.

Plutonium metal undergoes an anomalously large 25% collapse in volume from its largest volume δ phase (δ-Pu) to its low temperature α phase, yet the underlying thermodynamic mechanism has largely remained a mystery. Here we use magnetostriction measurements to isolate a previously hidden yet substantial electronic contribution to the entropy of δ-Pu, which we show to be crucial for the stabilization of this phase. The entropy originates from two competing instabilities of the 5f-electron shell, which we show to drive the volume of Pu in opposing directions, depending on the temperature and volume. Using calorimetry measurements, we establish a robust thermodynamic connection between the two excitation energies, the atomic volume, and the previously reported excess entropy of δ-Pu at elevated temperatures.

The Cardiff Dental Survey: oral hygiene, gingival and periodontal health in relation to smoking in young adults.

OBJECTIVE: To examine the relationship between tobacco smoking, oral hygiene, gingival and periodontal health in young adults. STUDY DESIGN: Cross-sectional (conducted in the course of a cohort study). SETTING: Cardiff, UK, 1989 and 2000. METHODS: Plaque was recorded, as was presence or absence of bleeding on probing and loss of attachment (LA). Information concerning tobacco smoking was obtained from questionnaire data. RESULTS: At age 19-20 years, smokers had statistically significantly (P < 0.01) higher whole mouth mean plaque scores than non-smokers. Whole mouth mean bleeding scores, however, were similar in smokers and non-smokers. The relationship of plaque to smoking was very similar at age 30-31, yet bleeding scores were approximately 25% lower in smokers than in non-smokers (P < 0.01). Whole mouth LA scores showed small, statistically non-significant differences between smokers and non-smokers. At the age of 30-31 years, gender and social class had a negligible confounding effect on oral hygiene, gingival and periodontal health in smokers and non-smokers. CONCLUSIONS: Smokers consistently demonstrated poorer oral hygiene than non-smokers. The effect of smoking in reducing gingival bleeding was already apparent at age 19-20 years despite the fact that, at this time, subjects might be assumed to have been exposed to a relatively small dose of tobacco over a short period of time. In the follow-up study conducted at the age of 30-31 years, the impact of smoking on the periodontal tissues was, as expected, more pronounced.

Shape-dependent ordering of gold nanocrystals into large-scale superlattices.

Self-assembly of individual building blocks into highly ordered structures, analogous to spontaneous growth of crystals from atoms, is a promising approach to realize the collective properties of nanocrystals. Yet the ability to reliably produce macroscopic assemblies is unavailable and key factors determining assembly quality/yield are not understood. Here we report the formation of highly ordered superlattice films, with single crystalline domains of up to half a millimetre in two dimensions and thickness of up to several microns from nanocrystals with tens of nanometres in diameter. Combining experimental and computational results for gold nanocrystals in the shapes of spheres, cubes, octahedra and rhombic dodecahedra, we investigate the entire self-assembly process from disordered suspensions to large-scale ordered superlattices induced by nanocrystal sedimentation and eventual solvent evaporation. Our findings reveal that the ultimate coherence length of superlattices strongly depends on nanocrystal shape. Factors inhibiting the formation of high-quality large-scale superlattices are explored in detail.

A randomised controlled trial of clinical outreach education to rationalise antibiotic prescribing for acute dental pain in the primary care setting.

OBJECTIVE: To assess the effect of educational outreach visits on antibiotic prescribing for acute dental pain in primary care. STUDY DESIGN: RCT. SETTING: General dental practices in four health authority areas in Wales. SUBJECTS AND METHODS: General dental practitioners were recruited to the study and randomly allocated to one of the three study groups (control group, guideline group or intervention group). Following the intervention, practitioners completed a standardised questionnaire for each patient that presented with acute dental pain. INTERVENTIONS: The control group received no intervention. The guideline group received educational material by post. The intervention group received educational material by post and an academic detailing visit by a trained pharmacist. The educational material included evidence-based guidelines on prescribing for acute dental pain and patient information leaflets. MAIN OUTCOME MEASURES: The number of antibiotic prescriptions issued to patients presenting with dental pain and the number of 'inappropriate' antibiotic prescriptions. Antibiotics were considered to be inappropriate if the patient did not have symptoms indicative of spreading infection. RESULTS: A total of 1,497 completed questionnaires were received from 23, 20 and 27 general dental practitioners in the control, guideline and intervention group respectively. Patients in the intervention group received significantly fewer antibiotic prescriptions than patients in the control group (OR (95% CI) 0.63 (0.41, 0.95)) and significantly fewer inappropriate antibiotic prescriptions (OR (95% CI) 0.33 (0.21, 0.54)). However, antibiotic and inappropriate antibiotic prescribing were not significantly different in the guideline group compared to the control group (OR (95% CI) 0.83 (0.55, 1.21) and OR (95% CI) 0.82 (0.53, 1.29) respectively). CONCLUSIONS: Strategies based upon educational outreach visits may be successfully employed to rationalise antibiotic prescribing by dental practitioners.

Multilevel principal component analysis (mPCA) in shape analysis: A feasibility study in medical and dental imaging.

BACKGROUND AND OBJECTIVE: Methods used in image processing should reflect any multilevel structures inherent in the image dataset or they run the risk of functioning inadequately. We wish to test the feasibility of multilevel principal components analysis (PCA) to build active shape models (ASMs) for cases relevant to medical and dental imaging. METHODS: Multilevel PCA was used to carry out model fitting to sets of landmark points and it was compared to the results of "standard" (single-level) PCA. Proof of principle was tested by applying mPCA to model basic peri-oral expressions (happy, neutral, sad) approximated to the junction between the mouth/lips. Monte Carlo simulations were used to create this data which allowed exploration of practical implementation issues such as the number of landmark points, number of images, and number of groups (i.e., "expressions" for this example). To further test the robustness of the method, mPCA was subsequently applied to a dental imaging dataset utilising landmark points (placed by different clinicians) along the boundary of mandibular cortical bone in panoramic radiographs of the face. RESULTS: Changes of expression that varied between groups were modelled correctly at one level of the model and changes in lip width that varied within groups at another for the Monte Carlo dataset. Extreme cases in the test dataset were modelled adequately by mPCA but not by standard PCA. Similarly, variations in the shape of the cortical bone were modelled by one level of mPCA and variations between the experts at another for the panoramic radiographs dataset. Results for mPCA were found to be comparable to those of standard PCA for point-to-point errors via miss-one-out testing for this dataset. These errors reduce with increasing number of eigenvectors/values retained, as expected. CONCLUSIONS: We have shown that mPCA can be used in shape models for dental and medical image processing. mPCA was found to provide more control and flexibility when compared to standard "single-level" PCA. Specifically, mPCA is preferable to "standard" PCA when multiple levels occur naturally in the dataset.