Craniofacial Shape Research Articles

Computational anatomy and geometric shape analysis enables analysis of complex craniofacial phenotypes in zebrafish.

ABSTRACTDue to the complexity of fish skulls, previous attempts to classify craniofacial phenotypes have relied on qualitative features or sparce 2D landmarks. In this work we aim to identify previously unknown 3D craniofacial phenotypes with a semiautomated pipeline in adult zebrafish mutants. We first estimate a synthetic ‘normative’ zebrafish template using MicroCT scans from a sample pool of wild-type animals using the Advanced Normalization Tools (ANTs). We apply a computational anatomy (CA) approach to quantify the phenotype of zebrafish with disruptions in bmp1a, a gene implicated in later skeletal development and whose human ortholog when disrupted is associated with Osteogenesis Imperfecta. Compared to controls, the bmp1a fish have larger otoliths, larger normalized centroid sizes, and exhibit shape differences concentrated around the operculum, anterior frontal, and posterior parietal bones. Moreover, bmp1a fish differ in the degree of asymmetry. Our CA approach offers a potential pipeline for high-throughput screening of complex fish craniofacial shape to discover novel phenotypes for which traditional landmarks are too sparce to detect. The current pipeline successfully identifies areas of variation in zebrafish mutants, which are an important model system for testing genome to phenome relationships in the study of development, evolution, and human diseases. This article has an associated First Person interview with the first author of the paper.

Cohort profile: early school years follow-up of the Asking Questions about Alcohol in Pregnancy Longitudinal Study in Melbourne, Australia (AQUA at 6)

PurposeThe Asking Questions about Alcohol in Pregnancy (AQUA) study, established in 2011, is a prebirth cohort of 1570 mother and child pairs designed to assess the effects of low to...

A geometric morphometric evaluation of facial hard tissue patterns

OBJECTIVE:The purpose of this study was to investigate the size and shape variations of hard tissue patterns in different skeletal relations in Malaysian Malay subjects using the two-dimensional geometric morphometrics method.MATERIALS AND METHODS:A total of 188 lateral cephalograms of adult Malay subjects (aged between 18 and 40 years) with Class I, II, and III skeletal relations were collected. Ten two-dimensional hard tissue landmarks were applied on lateral cephalograms which underwent landmark application and shape analyses as Procrustes ANOVA analysis, principal component analysis, canonical variate analysis, and discriminant function analysis. Statistical analyses were performed to find the mean and variance of each landmark using one-way ANOVA. The raw data from shape analysis were used to calculate the link between landmarks.RESULTS:Skeletal relations showed 16 Principal Components which indicated that variances existed in 16 different dimensions. In Procrustes ANOVA, the Centroid size was significantly different in genders and skeletal relations (P < 0.01). Canonical variate analysis showed the highest Mahalanobis distances and Procrustes distances between Class II and III among skeletal relations and between gender groups (P < 0.0001). Discriminant function analysis showed the classification was mostly accurate, especially for Class II and Class III with success rates of 90.6% and 83.3%, respectively, after cross-validation. The statistical analysis showed significant differences (P < 0.05) in hard tissue landmarks.CONCLUSION:There were different ANB angles in different skeletal relations. The GMM could be used as an alternative tool for diagnosis and treatment planning for craniofacial shape evaluations for future orthodontists and maxillofacial surgeons.

Loeys-Dietz and Shprintzen-Goldberg syndromes: analysis of TGF-β-opathies with craniofacial manifestations using an innovative multimodality method

BackgroundElevated transforming growth factor-beta (TGF-β) signalling has been implicated in the pathogenesis of Loeys-Dietz syndrome (LDS) and Shprintzen-Goldberg syndrome (SGS). In this study, we provide a qualitative and quantitative analysis...

Relating multivariate shapes to genescapes using phenotype-biological process associations for craniofacial shape.

Realistic mappings of genes to morphology are inherently multivariate on both sides of the equation. The importance of coordinated gene effects on morphological phenotypes is clear from the intertwining of gene actions in signaling pathways, gene regulatory networks, and developmental processes underlying the development of shape and size. Yet, current approaches tend to focus on identifying and localizing the effects of individual genes and rarely leverage the information content of high-dimensional phenotypes. Here, we explicitly model the joint effects of biologically coherent collections of genes on a multivariate trait - craniofacial shape - in a sample of n = 1145 mice from the Diversity Outbred (DO) experimental line. We use biological process Gene Ontology (GO) annotations to select skeletal and facial development gene sets and solve for the axis of shape variation that maximally covaries with gene set marker variation. We use our process-centered, multivariate genotype-phenotype (process MGP) approach to determine the overall contributions to craniofacial variation of genes involved in relevant processes and how variation in different processes corresponds to multivariate axes of shape variation. Further, we compare the directions of effect in phenotype space of mutations to the primary axis of shape variation associated with broader pathways within which they are thought to function. Finally, we leverage the relationship between mutational and pathway-level effects to predict phenotypic effects beyond craniofacial shape in specific mutants. We also introduce an online application that provides users the means to customize their own process-centered craniofacial shape analyses in the DO. The process-centered approach is generally applicable to any continuously varying phenotype and thus has wide-reaching implications for complex trait genetics.

Complex genetic architecture of three-dimensional craniofacial shape variation in domestic pigeons.

Deciphering the genetic basis of vertebrate craniofacial variation is a longstanding biological problem with broad implications in evolution, development, and human pathology. One of the most stunning examples of craniofacial diversification is the adaptive radiation of birds, in which the beak serves essential roles in virtually every aspect of their life histories. The domestic pigeon (Columba livia) provides an exceptional opportunity to study the genetic underpinnings of craniofacial variation because of its unique balance of experimental accessibility and extraordinary phenotypic diversity within a single species. We used traditional and geometric morphometrics to quantify craniofacial variation in an F2 laboratory cross derived from the straight‐beaked Pomeranian Pouter and curved‐beak Scandaroon pigeon breeds. Using a combination of genome‐wide quantitative trait locus scans and multi‐locus modeling, we identified a set of genetic loci associated with complex shape variation in the craniofacial skeleton, including beak shape, braincase shape, and mandible shape. Some of these loci control coordinated changes between different structures, while others explain variation in the size and shape of specific skull and jaw regions. We find that in domestic pigeons, a complex blend of both independent and coupled genetic effects underlie three‐dimensional craniofacial morphology.

Overall Shape of Cranial Base may Dictate and Predict Skeletal Malocclusion

Skeletal malocclusion can present early in childhood and, in some cases, progress into adulthood. If the malocclusion or dentofacial deformity is severe enough, surgical correction through orthognathic surgery is inevitable. The ability to accurately predict the direction and magnitude of craniofacial growth is very limited and based on empirical knowledge. Growth is a key consideration when clinically managing skeletal malocclusion, as it has a direct impact on the timing and method of treatment. Without tools to predict or assess the risk of developing a severe malocclusion, the current practice is to “wait and watch” until growth is complete, and the malocclusion has completely manifested itself. This is frustrating to the patient, orthodontist, and oral surgeon. However, the growth of the cranial base is completed first, followed by the face and mandible, and there are indications that there are morphological and developmental correlations between these structures. This is based on 2-dimensional data with conflicting literature. Moreover, the role of genetics in many malocclusion types has been validated1 and the prevalence of inherited dentofacial deformities in families is well-known. Thus, it may be possible to predict craniofacial growth based on overall 3-dimensional craniofacial shape, particularly in families with skeletal malocclusions. The aims of this study are to establish the distinct 3D geometric morphometric variations between the 3 types of skeletal malocclusion (Angle's classification), demonstrate that this variation is largely attributed to the shape of the cranial base, and confirm feasibility in identifying at-risk craniofacial shape variation in a family trio.In total, 300 CBCTs from a curated dataset of Class I, II, and III healthy (non-syndromic) controls were used for 3D geometric morphometric analysis (Procrustes Superimposition, Principal Components and Partial-Least Square [PLS] regression analyses) to compare the shape of cranial base, face, and mandible between the 3 Classes; mean age 24.8 (14-58) years, 56% females. Validated 3D landmarks2 were applied to the CBCTs, P < .05 statistically significant. The CBCTs were obtained on Planmeca Promax with consistent parameters. Pre- and postoperative CBCTs from a 17-year-old female with skeletal Class III and those of her unaffected parents (53 and 56 years old) were analyzed against the controls. All participants were consented onto and CBCTs gathered through IRB-approved protocols.The 3 skeletal Classes segregated distinctly with the first 3 PCs, explaining 38.7% of variation. In the PLS analysis, integration and correlation were present between cranial base shape, face, and mandible with differences between Angle's classification (P = .001). In the family trio, the pre- and postoperative craniofacial shape of the proband remained within the Class III cluster, despite the normal postoperative jaw relationships. Moreover, the father appeared on the same plot as a Class III outlier, despite his normal clinical phenotype. The mother clustered within the Class II group consistent with her clinical phenotype (Image 1).The authors demonstrate that overall craniofacial shape segregates based on the 3 skeletal malocclusion types and that the cranial base shape correlates with the position of the face and mandible. Thus, the cranial base may be a significant driver in the development of a skeletal malocclusion. In addition, the position of the postoperative proband shape within the Class III cluster confirms that the cranial base contributes to the Class III phenotype even after surgical correction of jaw relationship. Finally, the shape association between the proband and her father is promising and indicates that craniofacial shape of parents will contribute to the development of more accurate growth prediction models.

Craniofacial shape from pre- to post-adolescence.

Craniofacial growth demonstrates significant variation and is difficult to predict. The aim of the present investigation was twofold: (1) to assess the association (covariation) between craniofacial shape at pre- and post-adolescence and (2) to evaluate if pre-adolescent craniofacial shape is related (covaries) with growth magnitude and direction. One hundred fifty subjects (86 males and 64 females) untreated orthodontically were selected from AAOF Craniofacial Growth Legacy Collection. Each subject had cephalograms taken before 9 (pre-adolescent stage) and after 15 years of age (post-adolescent). Fourteen curves comprising 123 points (10 fixed and 113 sliding semilandmarks) comprehensively covering the craniofacial skeleton were digitally traced on each cephalogram. Procrustes alignment, principal component analysis, 2-block partial least squares (2B-PLS) analysis, and regression analysis were done after sliding the semilandmarks to minimize bending energy. The first 16 principal components (PCs) were non-trivial and explained 85.2% of total shape variability in the sample. PC1 depicted mainly variability in the vertical direction, PC2 represented mostly variability in the saddle angle and in the antero-posterior position of the mandible, and PC3 depicted primarily variability of the mandibular shape (steep versus flat mandibular plane). The covariation between pre- and post-adolescent facial shape was statistically significant, both in the pooled sample (RV coefficient = 0.604) and in boys (RV = 0.639) and girls (RV = 0.629). The pre-adolescent shape was weakly associated with the magnitude of facial change-2-block PLS analysis demonstrated that blocks 1 and 2 were independent (P = 0.118, RV = 0.035). The pre-adolescent shape of the craniofacial complex explained approximately 60% of the post-adolescent shape of the craniofacial complex; however, the relationship between pre-adolescent shape of the craniofacial complex and magnitude of its change was weak.

Developmental integration between the lateral line sensory system and the craniofacial complex in a natural population

Non-traditional model systems can provide insight to the developmental and genetic basis of fundamental biological processes. One such process is the origin and patterning of the facial skeleton. Here, we present evidence that the intramembranous bones comprising the circumorbital complex in a teleost model are marked by the positions of large mechanosensory structures, canal neuromasts. Neuromasts comprise the lateral line system, and provide pressure and proprioceptive information to enable a number of key behaviors, such as predator avoidance, foraging, schooling and shoaling. Canal neuromasts appear to set the stage for facial patterning, since they colocalize to ossification sites destined to give rise to the six constituent bones of the circumorbital complex. Here, we demonstrate that closely related surface-dwelling morphs demonstrate an invariant pattern of development that gives rise to a symmetric and stereotypical circumorbital complex. In cavefish, however, this pattern is frequently altered - giving rise to ossification centers that are set closer, or more distant, from one another. Moreover, these alterations in position can vary across the left-right axis. Interestingly, in situations where two ossification centers are more closely set towards one another, they result in an inter-bone fusion (synostotic) event. Cavefish demonstrate at least three forms of cranial asymmetry, and we discuss how facial bone fusions may impact global craniofacial shape. These three-dimensional changes may prefigure, or facilitate, the lateral swimming preferences observed in cavefish. Moreover, the ‘predictive’ nature of circumorbital bone fusion will enable deeper insight to the connection between the earliest developmental events, and adult bone patterning and morphology. Collectively, the Mexican tetra is poised to provide new insight to the developmental basis for craniofacial aberrations shared deeply among the vertebrate subphylum.

A model of developmental canalization, applied to human cranial form.

Developmental mechanisms that canalize or compensate perturbations of organismal development (targeted or compensatory growth) are widely considered a prerequisite of individual health and the evolution of complex life, but little is known about the nature of these mechanisms. It is even unclear if and how a “target trajectory” of individual development is encoded in the organism’s genetic-developmental system or, instead, emerges as an epiphenomenon. Here we develop a statistical model of developmental canalization based on an extended autoregressive model. We show that under certain assumptions the strength of canalization and the amount of canalized variance in a population can be estimated, or at least approximated, from longitudinal phenotypic measurements, even if the target trajectories are unobserved. We extend this model to multivariate measures and discuss reifications of the ensuing parameter matrix. We apply these approaches to longitudinal geometric morphometric data on human postnatal craniofacial size and shape as well as to the size of the frontal sinuses. Craniofacial size showed strong developmental canalization during the first 5 years of life, leading to a 50% reduction of cross-sectional size variance, followed by a continual increase in variance during puberty. Frontal sinus size, by contrast, did not show any signs of canalization. Total variance of craniofacial shape decreased slightly until about 5 years of age and increased thereafter. However, different features of craniofacial shape showed very different developmental dynamics. Whereas the relative dimensions of the nasopharynx showed strong canalization and a reduction of variance throughout postnatal development, facial orientation continually increased in variance. Some of the signals of canalization may owe to independent variation in developmental timing of cranial components, but our results indicate evolved, partly mechanically induced mechanisms of canalization that ensure properly sized upper airways and facial dimensions.

Geometric morphometric investigation of craniofacial morphological change in domesticated silver foxes

To test the effects of domestication on craniofacial skeletal morphology, we used three-dimensional geometric morphometrics (GM) along with linear and endocranial measurements to compare selected (domesticated) and unselected foxes from the Russian Farm-Fox Experiment to wild foxes from the progenitor population from which the farmed foxes are derived. Contrary to previous findings, we find that domesticated and unselected foxes show minimal differences in craniofacial shape and size compared to the more substantial differences between the wild foxes and both populations of farmed foxes. GM analyses and linear measurements demonstrate that wild foxes differ from farmed foxes largely in terms of less cranial base flexion, relatively expanded cranial vaults, and increased endocranial volumes. These results challenge the assumption that the unselected population of foxes kept as part of the Russian Farm-Fox experiment are an appropriate proxy for ‘wild’ foxes in terms of craniofacial morphology and highlight the need to include wild populations in further studies of domestication syndrome to disentangle the phenotypic effects of multiple selection pressures. These findings also suggest that marked increases in docility cannot be reliably diagnosed from shape differences in craniofacial skeletal morphology.

Prenatal Alcohol Exposure and the Facial Phenotype in Adolescents: A Study Based on Meconium Ethyl Glucuronide.

Here, we explore the effects of prenatal alcohol exposure (PAE) in adolescence. We investigated associations between meconium ethyl glucoronide (EtG) and facial malformation. For 129 children (66/63 male/female; M = 13.3, SD = 0.32, 12–14 years), PAE was implemented by newborn meconium EtG and maternal self-reports during the third trimester. Cognitive development was operationalized by standardized scores (WISC V). The EtG cut-off values were set at ≥10 ng/g (n = 32, 24.8% EtG10+) and ≥112 ng/g (n = 20, 15.5% EtG112+). The craniofacial shape was measured using FAS Facial Photographic Analysis Software. EtG10+− and EtG112+-affected children exhibited a shorter palpebral fissure length (p = 0.031/p = 0.055). Lip circularity was smaller in EtG112+-affected children (p = 0.026). Maternal self-reports were not associated (p > 0.164). Lip circularity correlated with fluid reasoning (EtG10+ p = 0.031; EtG112+ p = 0.298) and working memory (EtG10+ p = 0.084; EtG112+ p = 0.144). The present study demonstrates visible effects of the facial phenotype in exposed adolescents. Facial malformation was associated with a child’s cognitive performance in the alcohol-exposed group. The EtG biomarker was a better predictor than maternal self-reports.

Craniofacial shape in patients with beta thalassaemia: a geometric morphometric analysis

The shape of the craniofacial complex of patients with beta thalassaemia was evaluated using geometric morphometrics on lateral cephalometric radiographs and was compared with matched controls. The beta thalassaemia group consisted of 40 patients (16 females, 24 males, mean age 33.4). Each patient was matched by age and gender to two controls (32 females, 48 males, mean age 33.1). The 120 lateral cephalometric radiographs were digitized and traced with 15 curves, 10 landmarks and 117 sliding semi-landmarks. These landmarks were subjected to Procrustes superimposition and principal component analysis in order to describe shape variability of the cranial base, maxilla and mandible, as well as of the entire craniofacial complex for each sex. The first 4 principal components accounted for 50% of the total sample’s variability. The beta thalassaemia group was significantly different in overall shape to the control group for both sexes. Similar findings were noted for the maxilla, the mandible and the cranial base. The main differences were related to smaller mandibular body for the thalassaemia group, midface protrusion and decrease in posterior face height. The shape of the craniofacial complex in these patients is prone to be more convex and hyperdivergent.

Differences among families in craniofacial shape at early life-stages of Arctic charr (Salvelinus alpinus)

BackgroundOrganismal fitness can be determined at early life-stages, but phenotypic variation at early life-stages is rarely considered in studies on evolutionary diversification. The trophic apparatus has been shown to contribute to sympatric resource-mediated divergence in several taxa. However, processes underlying diversification in trophic traits are poorly understood. Using phenotypically variable Icelandic Arctic charr (Salvelinus alpinus), we reared offspring from multiple families under standardized laboratory conditions and tested to what extent family (i.e. direct genetic and maternal effects) contributes to offspring morphology at hatching (H) and first feeding (FF). To understand the underlying mechanisms behind early life-stage variation in morphology, we examined how craniofacial shape varied according to family, offspring size, egg size and candidate gene expression.ResultsCraniofacial shape (i.e. the Meckel’s cartilage and hyoid arch) was more variable between families than within families both across and within developmental stages. Differences in craniofacial morphology between developmental stages correlated with offspring size, whilst within developmental stages only shape at FF correlated with offspring size, as well as female mean egg size. Larger offspring and offspring from females with larger eggs consistently had a wider hyoid arch and contracted Meckel’s cartilage in comparison to smaller offspring.ConclusionsThis study provides evidence for family-level variation in early life-stage trophic morphology, indicating the potential for parental effects to facilitate resource polymorphism.

Ontogenetic changes in magnitudes of integration in the macaque skull.

Magnitudes of morphological integration may constrain or facilitate craniofacial shape variation. The aim of this study was to analyze how the magnitude of integration in the skull of Macaca fascicularis changes throughout ontogeny in relation to developmental and/or functional modules. Geometric morphometric methods were used to analyze the magnitude of integration in the macaque cranium and mandible in 80 juvenile and 40 adult M. fascicularis specimens. Integration scores in skull modules were calculated using integration coefficient of variation (ICV) of eigenvalues based on a resampling procedure. Resultant ICV scores between the skull as a whole, and developmental and/or functional modules were compared using Mann-Whitney U tests. Results showed that most skull modules were more tightly integrated than the skull as a whole, with the exception of the chondrocranium in juveniles without canines, the chondrocranium/face complex and the mandibular corpus in adults, and the mandibular ramus in all juveniles. The chondrocranium/face and face/mandibular corpus complexes were more tightly integrated in juveniles than adults, possibly reflecting the influences of early brain growth/development, and the changing functional demands of infant suckling and later masticatory loading. This is also supported by the much higher integration of the mandibular ramus in adults compared with juveniles. Magnitudes of integration in skull modules reflect developmental/functional mechanisms in M. fascicularis. However, the relationship between "evolutionary flexibility" and developmental/functional mechanisms was not direct or simple, likely because of the complex morphology, multifunctionality, and various ossification origins of the skull.

Hedgehog signaling is necessary and sufficient to mediate craniofacial plasticity in teleosts

Phenotypic plasticity, the ability of a single genotype to produce multiple phenotypes under different environmental conditions, is critical for the origins and maintenance of biodiversity; however, the genetic mechanisms underlying plasticity as well as how variation in those mechanisms can drive evolutionary change remain poorly understood. Here, we examine the cichlid feeding apparatus, an icon of both prodigious evolutionary divergence and adaptive phenotypic plasticity. We first provide a tissue-level mechanism for plasticity in craniofacial shape by measuring rates of bone deposition within functionally salient elements of the feeding apparatus in fishes forced to employ alternate foraging modes. We show that levels and patterns of phenotypic plasticity are distinct among closely related cichlid species, underscoring the evolutionary potential of this trait. Next, we demonstrate that hedgehog (Hh) signaling, which has been implicated in the evolutionary divergence of cichlid feeding architecture, is associated with environmentally induced rates of bone deposition. Finally, to demonstrate that Hh levels are the cause of the plastic response and not simply the consequence of producing more bone, we use transgenic zebrafish in which Hh levels could be experimentally manipulated under different foraging conditions. Notably, we find that the ability to modulate bone deposition rates in different environments is dampened when Hh levels are reduced, whereas the sensitivity of bone deposition to different mechanical demands increases with elevated Hh levels. These data advance a mechanistic understanding of phenotypic plasticity in the teleost feeding apparatus and in doing so contribute key insights into the origins of adaptive morphological radiations.

Effects of Multi-Generational Soft Diet Consumption on Mouse Craniofacial Morphology.

Variations in craniofacial morphology may arise as a result of adaptation to different environmental factors such as soft diet (SD), which lessens functional masticatory load. Prior studies have shown that changes in the masticatory muscle function associated with a switch to short-term SD led to changes in craniofacial morphology and alveolar bone architecture. However, the long-term effects of SD and the associated adaptive changes in craniofacial shape are unclear. Our novel study set out to profile prospective skull changes in mice fed with SDs over multiple generations using three-dimensional (3D) geometric morphometric analysis (GMA). Our results revealed that short-term SD consumption led to a significant decrease in craniofacial size, along with numerous shape changes. Long-term SD consumption over 15 continuous generations was not associated with changes in craniofacial size; however, shape analysis revealed mice with shortened crania and mandibles in the anteroposterior dimension, as well as relative widening in the transverse dimension compared to the average shape of all mice analyzed in our study. Moreover, changes in shape and size associated with different functional loads appeared to be independent – shape changes persisted after diets were switched for one generation, whereas size decreased after one generation and then returned to baseline size. Our study is the first to study the role of prolonged, multi-generational SD consumption in the determination of craniofacial size and shape.

Viral delivery of tissue nonspecific alkaline phosphatase diminishes craniosynostosis in one of two FGFR2C342Y/+ mouse models of Crouzon syndrome.

Craniosynostosis is the premature fusion of cranial bones. The goal of this study was to determine if delivery of recombinant tissue nonspecific alkaline phosphatase (TNAP) could prevent or diminish the severity of craniosynostosis in a C57BL/6 FGFR2C342Y/+ model of neonatal onset craniosynostosis or a BALB/c FGFR2C342Y/+ model of postnatal onset craniosynostosis. Mice were injected with a lentivirus encoding a mineral targeted form of TNAP immediately after birth. Cranial bone fusion as well as cranial bone volume, mineral content and density were assessed by micro CT. Craniofacial shape was measured with calipers. Alkaline phosphatase, alanine amino transferase (ALT) and aspartate amino transferase (AST) activity levels were measured in serum. Neonatal delivery of TNAP diminished craniosynostosis severity from 94% suture obliteration in vehicle treated mice to 67% suture obliteration in treated mice, p<0.02) and the incidence of malocclusion from 82.4% to 34.7% (p<0.03), with no effect on cranial bone in C57BL/6 FGFR2C342Y/+ mice. In contrast, treatment with TNAP increased cranial bone volume (p< 0.01), density (p< 0.01) and mineral content (p< 0.01) as compared to vehicle treated controls, but had no effect on craniosynostosis or malocclusion in BALB/c FGFR2C342Y/+ mice. These results indicate that postnatal recombinant TNAP enzyme therapy diminishes craniosynostosis severity in the C57BL/6 FGFR2C342Y/+ neonatal onset mouse model of Crouzon syndrome, and that effects of exogenous TNAP are genetic background dependent.

Evaluation of the morphometric covariation between palatal and craniofacial skeletal morphology in class III malocclusion growing subjects

BackgroundTo study the covariation between palatal and craniofacial skeletal morphology in Class III growing patients through geometric morphometric analysis (GMM).MethodsIn this retrospective study, 54 Class III subjects (24F,30M;7.6 ± 0.8yy) were enrolled following these inclusion criteria: European ancestry, Class III skeletal and dental relationship, early mixed dentition, prepubertal skeletal maturation, familiarity for Class III malocclusion, no pseudo Class III malocclusion. Each patient provided upper digital cast and cephalogram before starting the therapy. Landmarks and semilandmarks were digitized (239 on the casts;121 on the lateral radiographs) and GMM was used. Procrustes analysis and principal component analysis (PCA) were applied to show the principal components of palatal and craniofacial skeletal shape variation. Two-block partial least squares analysis (PLS) was used to assess pattern of covariation between palatal and craniofacial morphology.ResultsRegarding palatal shape variation, PC with largest variance (PC1) described morphological changes in the three space dimensions, while, concerning the craniofacial complex components, PC1 revealed morphological differences along the vertical plane. A significant covariation was found between palatal and craniofacial shape. PLS1 accounted for more than 61,7% of the whole covariation, correlating the craniofacial divergence to palatal height and width.ConclusionsIn Class III subjects increments of angle divergence are related to a narrow and high palate.

Towards a Complete 3D Morphable Model of the Human Head

Three-dimensional morphable models (3DMMs) are powerful statistical tools for representing the 3D shapes and textures of an object class. Here we present the most complete 3DMM of the human head to date that includes face, cranium, ears, eyes, teeth and tongue. To achieve this, we propose two methods for combining existing 3DMMs of different overlapping head parts: (i). use a regressor to complete missing parts of one model using the other, and (ii). use the Gaussian Process framework to blend covariance matrices from multiple models. Thus, we build a new combined face-and-head shape model that blends the variability and facial detail of an existing face model (the LSFM) with the full head modelling capability of an existing head model (the LYHM). Then we construct and fuse a highly-detailed ear model to extend the variation of the ear shape. Eye and eye region models are incorporated into the head model, along with basic models of the teeth, tongue and inner mouth cavity. The new model achieves state-of-the-art performance. We use our model to reconstruct full head representations from single, unconstrained images allowing us to parameterize craniofacial shape and texture, along with the ear shape, eye gaze and eye color.