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.

Plutonium has strong electronic correlations, which makes it difficult to establish microscopic understanding of the complicated structural phase diagram. Here the authors identify an electronic contribution to the entropy that stabilises the δ-Pu phase.

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.

Electronic supplementary material

The online version of this article (doi:10.1186/s12887-017-0905-x) contains supplementary material, which is available to authorized users.

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.

Extractions as a form of interception in the developing dentition: a randomized controlled trial

OBJECTIVE

To determine if the extractions of lower primary canines are an effective procedure to relieve crowding of the labial segment.

STUDY DESIGN

randomized controlled trial. Subject sample: 83 cases were collected in clinics in Italy, Germany and Wales. The groups were followed over a 2-year period.

METHODS

Subjects were randomly allocated to a primary canine non-extraction or extraction group. Dental casts of the patients were collected at the start and at the recall period of the trial. The outcome measures recorded were lower incisor crowding, arch length, intermolar width, overbite, overjet, lower clinical crown heights and lower incisor inclinations.

STATISTICS

The Mann-Whitney test was used to compare the differences between the extraction and non-extraction groups.

RESULTS

In both groups, crowding reduced 1.27 mm in the non-extraction group and 6.03 mm in the extraction group. The difference between the 2 groups was 4.76 mm (P<0.05). The arch perimeter decreased more in the extraction group by 2.73 mm (P<0.05). As the incisor inclination stayed essentially the same, the loss in arch length was attributed to the molars moving forward. The net gain from extracting deciduous canines was 2.03 mm.

CONCLUSIONS

There was a reduction in lower incisor crowding as a result of lower primary canine extraction. However, arch perimeter decreased more in the extraction group leaving less space for the eruption of the lower secondary canines.

Current Products and Practice

There has been an escalating interest in three-dimensional imaging devices over the last decade. Orthodontists are beginning to appreciate the advantages that the third dimension gives to clinical diagnosis, treatment planning and patient education. This article focuses on the cutting edge technology of cone beam CT, which utilizes conventional X-ray technology and computerized volumetric reconstruction to reproduce a three-dimensional image. A variety of applications and range of issues associated with this technology will be discussed.

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.

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.

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.

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.

Local- versus landscape-scale effects on the demography of three forest-breeding songbirds in Ontario, Canada

Reproductive success of songbirds breeding in forest fragments can be influenced by local habitat characteristics and by anthropogenic land uses in the surrounding matrix such as exurban development and agriculture. Effectively managing these songbirds requires an understanding of which spatial scales most strongly influence their demography. We conducted a multiscale study to investigate the relative influence of local vegetation characteristics and landscape composition at two spatial scales (100 and 2000 m) in a predominantly agricultural landscape on songbird demography. Density, pairing success, nest success, and productivity were assessed for Ovenbirds ( Seiurus aurocapilla (L., 1766)), Wood Thrush ( Hylocichla mustelina (J.F. Gmelin, 1789)), and American Robins ( Turdus migratorius L., 1766) in 16 deciduous forest fragments in southeastern Ontario. Demography of Ovenbirds was most strongly associated with local vegetation characteristics, while demography of Wood Thrush and American Robins was most strongly related to landscape composition within a 2000 m buffer. For all three species, cross-scale correlations influenced nest success, although other demographic parameters were less affected. We conclude that relationships between local- and landscape-scale metrics and songbird demography are complex, species-specific, and differ among reproductive parameters, necessitating a multiscale approach to management.

Observation of 239Pu nuclear magnetic resonance

In principle, the spin-½ plutonium-239 ((239)Pu) nucleus should be active in nuclear magnetic resonance spectroscopy. However, its signal has eluded detection for the past 50 years. Here, we report observation of a (239)Pu resonance from a solid sample of plutonium dioxide (PuO(2)) subjected to a wide scan of external magnetic field values (3 to 8 tesla) at a temperature of 4 kelvin. By mapping the external field dependence of the measured resonance frequency, we determined the nuclear gyromagnetic ratio (239)γ(n)(PuO(2))/2π to be 2.856 ± 0.001 megahertz per tesla (MHz/T). Assuming a free-ion value for the Pu(4+) hyperfine coupling constant, we estimated a bare (239)γ(n)/2π value of ~2.29 MHz/T, corresponding to a nuclear magnetic moment of μ(n) ≈ 0.15μ(N) (where μ(N) is the nuclear magneton).

Numerical modelling of the fibre-matrix interaction in biaxial loading for hyperelastic soft tissue models

This paper assumes that a neo-Hookean matrix with neo-Hookean fibres is representative of soft tissue. Under this assumption, a unit cell model is proposed to investigate the fibre-matrix interfacial stress field for biological soft tissue under biaxial loadings. In this unit cell model, the soft tissue is treated as a composite where the matrix is unidirectionally reinforced with a single family of aligned fibres. The results are compared with the model of Guo et al., which accounts for the fibre-matrix interfacial stress field, and Qiu and Pence's model, which does not proceed from the assumption that the fibres are themselves neo-Hookean. It is found that the stress representative of the fibre-matrix interface plays an important role in the deformation of the composite, and the model of Guo et al. underestimates this stress under large biaxial deformation.

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.

Modelling skeletal muscle fibre orientation arrangement

Skeletal muscle tissues have complex geometries. In addition, the complex fibre orientation arrangement makes it quite difficult to create an accurate finite element muscle model. There are many possible ways to specify the complex fibre orientations in a finite element model, for example defining a local element coordinate system. In this paper, an alternative method using ABAQUS, which is combination of the finite element method and the non-uniform rational B-spline solid representation, is proposed to calculate the initial fibre orientations. The initial direction of each muscle fibre is specified as the tangent direction of the NURBS curve which the fibre lies on, and the directions of the deformed fibres are calculated from the initial fibre directions, the deformation gradients and the fibre stretch ratios. Several examples are presented to demonstrate the ability of the proposed method. Results show that the proposed method is able to characterise both the muscle complex fibre orientation arrangement and its complex mechanical response.

Avian nest success, mammalian nest predator abundance, and invertebrate prey availability in a fragmented landscape

Avian nest success is largely determined by predation, but factors affecting the abundance of potential nest predators are rarely studied. We used an information–theoretic approach to assess relative support for models including invertebrate biomass, mammalian nest predator abundance, and percent cover at nests as explanatory variables for nest success of Ovenbirds ( Seiurus aurocapilla (L., 1766)) and Wood Thrush ( Hylocichla mustelina (J.F. Gmelin, 1789)). We ranked models including local vegetation characteristics and landscape composition at two spatial scales (100 and 2000 m) as explanatory variables for the abundance of mammalian nest predator groups and for prey biomass. The nest success of Ovenbirds was best explained by a positive association with percent cover by forbs and seedlings, whereas a positive relationship with prey biomass best explained the nest success of Wood Thrush. Most mammal genera were associated with landscape composition within 100 m of the study sites, and most were positively associated with housing density. Prey biomass was best explained by a positive association with less intensive agriculture within 2000 m. Implementing silvicultural techniques that preserve important habitat features within fragmented forests, limiting housing density within 100 m, and increasing the amount of less intensive agriculture within 2000 m of forest fragments may improve nest success for forest songbirds.

A visco-hyperelastic model for skeletal muscle tissue under high strain rates

In this paper, a visco-hyperelastic skeletal muscle model is developed. The constitutive relation is based on the definition of a Helmholtz free energy function. It is assumed that the Helmholtz energy can be decomposed into volumetric and isochoric parts; furthermore, the isochoric energy can be decoupled into hyperelastic and viscous parts. The model developed involves 14 material parameters and its performance is evaluated by comparing the finite element simulation results with the published experimental studies on the New Zealand white rabbit tibialis anterior muscle. Results show that this model is able to describe the visco-hyperelastic behaviour of both passive and active skeletal muscle tissues under high strain rates (10/s and 25/s).

The PREM score: a graphical tool for predicting survival in very preterm births

OBJECTIVE

To develop a tool for predicting survival to term in babies born more than 8 weeks early using only information available at or before birth.

DESIGN

1456 non-malformed very preterm babies of 22-31 weeks' gestation born in 2000-3 in the north of England and 3382 births of 23-31 weeks born in 2000-4 in Trent.

OUTCOME

Survival to term, predicted from information available at birth, and at the onset of labour or delivery.

METHOD

Development of a logistic regression model (the prematurity risk evaluation measure or PREM score) based on gestation, birth weight for gestation and base deficit from umbilical cord blood.

RESULTS

Gestation was by far the most powerful predictor of survival to term, and as few as 5 extra days can double the chance of survival. Weight for gestation also had a powerful but non-linear effect on survival, with weight between the median and 85th centile predicting the highest survival. Using this information survival can be predicted almost as accurately before birth as after, although base deficit further improves the prediction. A simple graph is described that shows how the two main variables gestation and weight for gestation interact to predict the chance of survival.

CONCLUSION

The PREM score can be used to predict the chance of survival at or before birth almost as accurately as existing measures influenced by post-delivery condition, to balance risk at entry into a controlled trial and to adjust for differences in "case mix" when assessing the quality of perinatal care.

Study of the scan uniformity from an i-CAT cone beam computed tomography dental imaging system

OBJECTIVES

As part of an ongoing programme to improve diagnosis and treatment planning relevant to implant placement, orthodontic treatment and dentomaxillofacial surgery, a study has been made of the spatial accuracy and density response of an i-CAT, a cone beam CT (CBCT) dental imaging system supplied by Imaging Sciences International Inc.

METHODS

Custom-made phantoms using acrylic sheet and water were used for measurements on spatial accuracy, density response and noise. The measurements were made over a period of several months on a clinical machine rather than on a machine dedicated to research.

RESULTS

Measurements on a precision grid showed the spatial accuracy to be universally within the tolerance of +/-1 pixel. The density response and the noise in the data were found to depend strongly on the mass in the slice being scanned.

CONCLUSIONS

The density response was subject to two effects. The first effect changes the whole slice uniformly and linearly depends on the total mass in the slice. The second effect exists when there is mass outside the field of view, dubbed the "exo-mass" effect. This effect lowers the measured CT number rapidly at the scan edge furthest from the exo-mass and raises it on the adjacent edge. The noise also depended quasi-linearly on the mass in the slice. Some general performance rules were drafted to describe these effects and a preliminary correction algorithm was constructed.

A three-dimensional look for facial differences between males and females in a British-Caucasian sample aged 151/2 years old

BACKGROUND

Optical surface scanning accurately records the three-dimension (3D) shape of the face non-invasively. Many software programs have been developed to process and analyze the 3D data, enabling the clinicians to create average templates for groups of subjects to provide a comparison of facial shape.

OBJECTIVE

Differences in facial morphology of males and females were identified using a laser scan imaging technology.

SUBJECTS AND METHODS

This study was undertaken on 380 British-Caucasian children aged 15 and a half year old, recruited from the Avon Longitudinal Study of Parents and Children (ALSPAC). 3D facial images were obtained for each individual using two high resolution Konica/Minolta laser scanners. The scan quality was assessed and any unsuitable scans were excluded from the study. Average facial templates were created for males and females, and a registration technique was used to superimpose the facial shells of males and females so that facial differences can be quantified.

RESULTS

Thirty unsuitable scans were excluded from the study. The final sample consisted of 350 subjects (166 females, 184 males). Females tend to have more prominent eyes and cheeks in relation to males with a maximum difference of 2.4 mm. Males tend to have more prominent noses and mouths with a maximum difference of 2.7 mm. About 31% of the facial shells match exactly (no difference), mainly in the forehead and chin regions of the face.

CONCLUSIONS

Differences in facial morphology can be accurately quantified and visualized using 3D imaging technology. This method of facial assessment can be recommended and applied for future research studies to assess facial soft tissue changes because of growth or healthcare intervention.

Weight change in the term baby in the first 2 weeks of life

BACKGROUND

Midwives once used serial weighing to highlight lactation problems, but this is now discouraged for the fear of undermining maternal confidence.

AIM

To explore weight changes in healthy newborn term babies, to gain information to aid interpretation of such measurements and to construct a centile chart for those exclusively breastfed during the first 2 weeks.

METHOD

Two hundred ninety-nine mothers weighed their baby daily using the same electronic scales. In 46 cases, three or more consecutive measurements were omitted leaving 253 series to evaluate, of which 111 were exclusively breastfed.

RESULTS

Breastfed babies lost a mean 6.4% of birthweight (95% CI: 5.5-7.3%) before starting to gain, and 54% took more than 8 days to regain birthweight. Artificially fed babies lost less (3.7%, 95% CI: 2.7-4.7%), but 39% had not regained their birthweight by 8 days. Once birthweight was regained, average gain was about 1% of birthweight per day in both breast- and artificially-fed babies. Measurements less than 5 days apart predicted average weight gain poorly.

CONCLUSIONS

Feeding problems should be considered if weight is not increasing by 6 days, but some healthy babies take 17 days to regain their birthweight.

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.

[Not Available]

The ICON (Index of Complexity, Outcome and Need) is a new index based on the consensus opinion of 97 European and American orthodontists. It records orthodontics treatment need on the basis of 5 components i.e. crossbite, upper arch crowding/spacing, buccal segment antero-posterior relationship and anterior vertical relationship. This index can be used in epidemiological studies and by public services and third party co-payment for the determination of those patients who may be eligible for public funding or reimbursement of fees.

Facial templates: a new perspective in three dimensions

PURPOSE

This paper describes the use of adult facial template in gender-specific facial analysis.

SUBJECTS AND METHODS

Eighty adults, mean age 24.5, were selected for the study. Laser-scanned images of the subjects were obtained under a reproducible and controlled environment with two Minolta Vivid 900 (Osaka, Japan) optical laser-scanning devices assembled as a stereo-pair. A set of left and right scanned images was taken for each subject and each scan took an average of 2.5 s. These scanned images were processed and merged to form a composite three-dimensional soft tissue reproduction of the subjects using commercially available reverse modelling software. The differences in facial morphology were measured using shell deviation colour maps. The facial template was used to compare differences between males vs. females groups and two subjects with facial disproportions.

RESULTS

The difference between the male and female facial templates was 1.28 +/- 1.02 mm. The areas of greatest deviation were at the nasal, zygomatic area and lower jaw line. The results of the surface deviation maps between the templates and subjects with facial disproportion showed that the results could be applied for orthodontic diagnosis.

CONCLUSIONS

The construction of the adult facial templates provides an interesting perspective into measuring changes in groups of patients and also acts as a useful template for the comparison of skeletal disproportion.