Craniofacial morphology in Chinese female twins: a semi-longitudinal cephalometric study

Genetic and environmental impact on mandibular growth in mono- and dizygotic twins during adolescence: A retrospective cohort study

INTRODUCTION

This study aimed to discover the genetic and environmental factors that contribute to the mandibular development of untreated monozygotic and dizygotic twins.

MATERIAL AND METHODS

The sample, taken from the Forsyth Moorrees Twin Study, included 52 untreated monozygotic twins (36 male, 16 female) and 46 untreated dizygotic twins (23 male, 23 female). At the ages of 12 and 17, lateral cephalograms were collected and traced to assess total mandibular length, mandibular ramus length, mandibular corpus length, gonial angle, SNB, and bony chin prominence. The genetic and environmental components of variation were assessed using multilevel mixed-effects structural equation modelling.

RESULTS

At 12 years of age, high additive genetic influences were observed for total mandibular length (74%), gonial angle (76%), SNB (41%), and bony chin prominence (64%), whereas strong dominant genetic components were observed for corpus length (72%), and mandibular ramus length was under unique environment influence (54%). At 17 years of age, only total mandibular length (45%), ramus length (53%), gonial angle (76%), and bony chin prominence (68%) were under strong additive genetic control, while the remainder were under strong dominant genetic control.

CONCLUSIONS

Although monozygotic and dizygotic twins share at least a portion of their DNA, additive, dominant, or environmental components were discovered during adolescence. Nonetheless, by the age of 17, the majority of the mandibular traits are under either additive or dominant genetic impact.

Heritability of facial soft tissue growth in mono- and dizygotic twins at 12 and 17 years of age: A retrospective cohort study

OBJECTIVE

The purpose of this investigation of untreated monozygotic and dizygotic twins was to identify the genetic and environmental components to the facial soft tissue growth.

SETTINGS AND SAMPLE POPULATION

The sample consisted of 52 untreated monozygotic twins (36 male and 16 female) and 46 untreated dizygotic twins (23 male and 23 female) from the Forsyth Moorrees Twin Study (1959-1975).

MATERIALS AND METHODS

Lateral cephalograms were taken at 12 and 17 years of age and traced to analyse facial convexity, nasolabial angle, upper and lower lip thickness, upper and lower lip profile and nose prominence. The genetic and environmental components of variance were analysed with structural equation modelling for multilevel mixed-effects model.

RESULTS

At 12 years of age, strong additive genetic influence was seen for facial convexity (70%), upper lip profile (66%) and nose prominence (65%), whereas strong dominant genetic components were found for upper lip thickness (56%). Nevertheless, under unique environment influence were nasolabial angle (58%), lower lip profile (51%) and lower lip thickness (64%). At 17 years of age, only upper lip thickness (55%) and nose prominence (84%) were under strong additive genetic control, while the rest of the variables were under strong dominant genetic control. The only exception was lower lip thickness (61%), which is still influenced by the unique environment.

CONCLUSION

Although monozygotic/dizygotic twins share at least part of their genome, at both times either additive, dominant or environmental components were found. Nevertheless, at 17 years of age most of the variables are either under additive or dominant genetic influence.

Differences in the heritability of craniofacial skeletal and dental characteristics between twin pairs with skeletal Class I and II malocclusions

Objective

To investigate differences in the heritability of skeletodental characteristics between twin pairs with skeletal Class I and Class II malocclusions.

Methods

Forty Korean adult twin pairs were divided into Class I (C-I) group (0° ≤ angle between point A, nasion, and point B [ANB]) ≤ 4°; mean age, 40.7 years) and Class II (C-II) group (ANB > 4°; mean age, 43.0 years). Each group comprised 14 monozygotic and 6 dizygotic twin pairs. Thirty-three cephalometric variables were measured using lateral cephalograms and were categorized as the anteroposterior, vertical, dental, mandible, and cranial base characteristics. The ACE model was used to calculate heritability (A > 0.7, high heritability). Thereafter, principal component analysis (PCA) was performed.

Results

Twin pairs in C-I group exhibited high heritability values in the facial anteroposterior characteristics, inclination of the maxillary and mandibular incisors, mandibular body length, and cranial base angles. Twin pairs in C-II group showed high heritability values in vertical facial height, ramus height, effective mandibular length, and cranial base length. PCA extracted eight components with 88.3% in the C-I group and seven components with 91.0% cumulative explanation in the C-II group.

Conclusions

Differences in the heritability of skeletodental characteristics between twin pairs with skeletal Class I and II malocclusions might provide valuable information for growth prediction and treatment planning.

Genetic and environmental components of vertical growth in mono- and dizygotic twins up to 15-18 years of age

OBJECTIVES

To determine the additive genetic and environmental contributions to the vertical growth of craniofacial structures.

MATERIALS AND METHODS

The sample consisted of 64 untreated monozygotic (44 male, 20 female) and 61 untreated dizygotic twins (32 male, 29 female). Lateral cephalograms taken at 15 and 18 years of age were traced to analyze the sella-nasion-nasal line angle (SN-NL), nasal line-mandibular line angle (ML-NL), sella-nasion-mandibular line angle (SN-ML), sella-nasion-sella-gnathion angle (Y-axis), posterior face height/anterior face height (PFH/AFH), and lower anterior face height/anterior face height (LAFH/AFH). The genetic and environmental components of variance were analyzed with structural equation modeling for multilevel mixed effects.

RESULTS

At 15 years of age, strong dominant genetic control was seen for NL-ML (81%), LAFH/AFH (73%), and Y-axis (57%), whereas strong additive genetic components were found for PFH/AFH (78%), SN-NL (58%), and SN-ML (57%). Unique environmental factors accounted for 18-42% of observed variance, with SN-NL being affected the most (42%). At 18 years of age, only LAFH/AFH (86%) was under strong dominant genetic control, whereas the remainder were under additive genetic influence. The sole exception was SN-NL, which changed from additive to unique environmental influence.

CONCLUSIONS

Either additive or dominant genetic components were found at 15 or 18 years of age for most vertical variables. Environmental factors accounted for about 10-40%, with SN-NL being mostly affected.

Heritability of Craniofacial Characteristics in Twins - Cephalometric Study

Introduction:

The growth and development of the craniofacial complex are under the influence of genetic and environmental factors, which determine its morphological and functional characteristics. Twin studies provide significant insight into how many genetic and environmental factors determine dental and craniofacial characteristics.

Aim:

The aim of the study was to determine the genetic influence on craniofacial complex using a twin study model.

Methods:

The study sample comprised 52 pairs of twins who were referred to the Orthodontic Department, School of Dental medicine, University of Sarajevo. Informed consent was obtained by the parents of the children included in the study. Twenty pairs of twins were diagnosed as monozygotic while 32 pairs were diagnosed as dizygotic. Zygosity was diagnosed by physical characteristics similarity. Nineteen variables were measured: 10 dental variables, 9 cephalometric.

Results:

Based on the findings of this study, t-test showed significant genetic effect on the length of cranial base (p = 0.03), corpus of maxilla (p = 0.02) and mandibular length (p = 0.03), and also for B-angle (p = 0.04). Environmental factors are more involved in determining dental traits (e.g., the inclination of the incisors).

Conclusion:

There is a significant genetic effect on the linear cephalometric variables: the length of the cranial base, maxillary length and mandibular length.

Vertical growth in mono-and dizygotic twins: A longitudinal cephalometric cohort study

OBJECTIVE

The aims of this longitudinal analysis of untreated monozygotic and dizygotic twins were to investigate vertical changes of the craniofacial structures during growth, to determine the concordance between genetically twins and to assess the genetic component for the various aspects of vertical growth.

SETTINGS AND SAMPLE POPULATION

The sample consisted of 34 pairs of untreated monozygotic twins (23 male, 11 female) and 30 untreated dizygotic siblings of multiple birth (8 male, 8 female and 14 mixed) from the Forsyth Moorrees Twin Study (1959-1975); lateral cephalograms taken from 6 to 18 years of age were analysed at 3-year intervals.

MATERIALS AND METHODS

Cephalograms were traced, and longitudinal changes between twins in six angular and proportional vertical cephalometric variables (SN-NL, ML-NL, SN-ML, y-axis, PFH/AFH and LAFH/AFH) were analysed with intraclass correlation coefficients and linear regression modelling.

RESULTS

The concordance between monozygotic/dizygotic twins at 18 years of age was moderate to high with intraclass correlation coefficient values between 0.51 and 0.66. Additionally, sex differences in concordance at 18 years of age were found for three variables. High heritability (66%-79%) was observed for 5 of the 6 variables (LAFH/AFH, ML-NL, y-axis, SN-ML, PFH/AFH), while SN-NL showed limited heritability (34%).

CONCLUSIONS

Although monozygotic/dizygotic twins share at least part of their genetic material, differences in the vertical dimension were found. This supports the complex developmental mechanism of the human face and the varying influence of genetic and environmental factors.

Differences in heritability of craniofacial skeletal and dental characteristics between hypo- and hyper-divergent patterns using Falconer's method and principal component analysis

OBJECTIVES

To investigate the difference in heritability of craniofacial skeletal and dental characteristics between hypodivergent and hyperdivergent patterns.

MATERIALS AND METHODS

53 Korean adult monozygotic (MZ) and dizygotic (DZ) twins and their siblings were divided into a hypodivergent group (Group 1, SN-MP < 35°, 17 MZ pairs; 11 DZ and sibling [DS] pairs of the same gender) and hyper-divergent group (Group 2, SN-MP > 35°, 16 MZ pairs; 9 DS pairs of the same gender). A total of 56 cephalometric variables were measured using lateral cephalographs. Craniofacial structures were divided into anteroposterior, vertical, dental, mandible, and cranial base characteristics. Falconer's method was used to calculate heritability (h² > 0.8, high). After principal component analysis (PCA), the mean h ² value of each component was calculated.

RESULTS

Group 1 exhibited high heritability values in shape and position of the mandible, vertical angular/ratio variables, cranial base shape, and maxillary incisor inclination. Group 2 showed high heritability values in anteroposterior position of the maxilla, intermaxillary relationship, vertical angular variables, cranial base length, and mandibular incisor inclination. Occlusal plane inclination showed high heritability in both groups. Although vertical structure presented a high overall mean h ² value in Group 1, there were no structures that exhibited a high overall mean h ² value in Group 2. PCA derived 10 components with 91.2% and 92.7% of cumulative explanation in Groups 1 and 2, respectively.

CONCLUSIONS

It is necessary to estimate or predict growth according to vertical pattern for providing differential diagnosis and orthodontic/orthopedic treatment planning.

Facial soft tissue growth in identical twins

INTRODUCTION

The aims of this longitudinal analysis of untreated monozygotic twins were to investigate the change of the facial soft tissues during growth, to determine the concordance of soft tissue growth patterns between genetically identical twins, and to assess the genetic component of soft tissue development.

METHODS

The sample consisted of 33 pairs of untreated monozygotic twins (23 male, 10 female) from the Forsyth Moorrees Twin Study (1959-1975); lateral cephalograms taken from 6 to 18 years of age were analyzed at 3-year intervals. Cephalograms were traced, and longitudinal changes in the soft tissue profile between twins were analyzed with intraclass correlation coefficients and linear regression modelling.

RESULTS

The concordance between monozygotic twins at 18 years of age was moderate to high with intraclass correlation coefficients values between 0.37 and 0.87. Additionally, female twins showed higher concordance at 18 years of age than did male twins for all included variables. However, about 10% to 46% of the twin pairs had large differences in their soft tissue parameters, even after the growth period.

CONCLUSIONS

Although monozygotic twins possess the same genetic material, differences in the soft tissues were found. This supports the complex developmental mechanism of the human face and the varying influence of genetic and environmental factors.

A genetic heritage; the same yet different: A comparative study in twins

Since the 19th century, and in every field of medicine, monozygotic twins have been studied to assess the involvement of genetic and environmental factors in phenotypic expression. The phenotype/genotype relationship remains the leading problem in contemporary biology. In dentofacial orthopedics, this relationship is of relevance in the three-dimensional approach to the face, in both diagnosis and treatment. The present study of two monozygotic twins presenting skeletal class III malocclusions which were genetic yet different is a clear illustration of the interaction of genotype and epigenetic factors with environmental influences. We will demonstrate that treatment can reduce phenotypic differences.

Photogrammetric Correlation of Face with Frontal Radiographs and Direct Measurements

INTRODUCTION

Photogrammetry is a science of making measurements from photographs. As cephalometric analysis till date has focused mainly on skeletal relationships, photogrammetry may provide a means to reliably assess and compare soft tissue and hard tissue measurements.

AIM

To compare and correlate linear measurements taken directly from subject's faces and from standardized frontal cephalometric radiographs and to correlate them with standardized frontal facial photographs of Indian population and to obtain mean values.

MATERIALS AND METHODS

A cross-sectional study was conducted on 30 subjects of Indian origin. Frontal cephalograms and standardized frontal photographs were obtained from subjects in the age group of 18- 25 years. Vernier calipers were used to obtain facial measurements directly. Photographs and radiographs were uploaded and measured using Nemoceph software. Analogous cephalometric, photographic and direct measurements were compared by one-way ANOVA to assess Pearson correlation coefficients for 12 linear measurements (6 vertical, 6 horizontal). Bonferroni post-hoc test was done for pair wise comparison.

RESULTS

Among all measurements used, O_R-O_L (orbitale right-orbitale left) showed a high correlation r = 0.76, 0.70, 0.71. There was moderate correlation with En_R-En_L (endocanthion rt - endocanthion lt) r² = 0.62, 0.68, 0.68. Highly significant correlation was evident with N-Sn, En_R-En_L and Ag_R-Ag_L with p<0.001.

CONCLUSION

A statistically significant correlation was found between photographic, radiographic and direct measurements. Therefore, photogrammetry has proven to be an alternative diagnostic tool that can be used in epidemiologic studies when there is a need for a simple, basic, non-invasive and cost-effective method.

Craniofacial characteristics in the sagittal dimension: A cephalometric study in Lebanese young adults

OBJECTIVES

The purpose of this study was to assess the sagittal cephalometric characteristics of young adult Lebanese individuals and assess gender-related differences.

MATERIALS AND METHODS

Conventional lateral cephalograms were obtained from 117 subjects. Eight linear/angular measurements combining sagittal parameters selected form McNamara and Steiner analyses were recorded. Paired t-test was applied to evaluate differences between genders and skeletal classes.

RESULTS

Males showed significantly greater maxillary and mandibular length than females. ANB was larger in females with no significant differences in SNA values indicating that Lebanese females tend to have a more convex profile than their male counterparts. Subjects with skeletal Class III tended to have a retrognathic maxilla rather than a prognathic mandible.

CONCLUSIONS

Sexual dimorphism is evident in young Lebanese adults relative to linear skeletal dimensions regardless of the skeletal class. Skeletal determinants of Class III malocclusions may be different from those of other population groups.

Genetic and Environmental Contributions to Facial Morphological Variation: A 3D Population-Based Twin Study

INTRODUCTION

Facial phenotype is influenced by genes and environment; however, little is known about their relative contributions to normal facial morphology. The aim of this study was to assess the relative genetic and environmental contributions to facial morphological variation using a three-dimensional (3D) population-based approach and the classical twin study design.

MATERIALS AND METHODS

3D facial images of 1380 female twins from the TwinsUK Registry database were used. All faces were landmarked, by manually placing 37 landmark points, and Procrustes registered. Three groups of traits were extracted and analysed: 19 principal components (uPC) and 23 principal components (sPC), derived from the unscaled and scaled landmark configurations respectively, and 1275 linear distances measured between 51 landmarks (37 manually identified and 14 automatically calculated). The intraclass correlation coefficients, rMZ and rDZ, broad-sense heritability (h2), common (c2) and unique (e2) environment contributions were calculated for all traits for the monozygotic (MZ) and dizygotic (DZ) twins.

RESULTS

Heritability of 13 uPC and 17 sPC reached statistical significance, with h2 ranging from 38.8% to 78.5% in the former and 30.5% to 84.8% in the latter group. Also, 1222 distances showed evidence of genetic control. Common environment contributed to one PC in both groups and 53 linear distances (4.3%). Unique environment contributed to 17 uPC and 20 sPC and 1245 distances.

CONCLUSIONS

Genetic factors can explain more than 70% of the phenotypic facial variation in facial size, nose (width, prominence and height), lips prominence and inter-ocular distance. A few traits have shown potential dominant genetic influence: the prominence and height of the nose, the lower lip prominence in relation to the chin and upper lip philtrum length. Environmental contribution to facial variation seems to be the greatest for the mandibular ramus height and horizontal facial asymmetry.

Heritability of mandibular cephalometric variables in twins with completed craniofacial growth

OBJECTIVES

To determine genetic and environmental impact on mandibular morphology using lateral cephalometric analysis of twins with completed mandibular growth and deoxyribonucleic acid (DNA) based zygosity determination.

MATERIALS AND METHODS

The 39 cephalometric variables of 141 same gender adult pair of twins were analysed. Zygosity was determined using 15 specific DNA markers and cervical vertebral maturation method was used to assess completion of the mandibular growth. A genetic analysis was performed using maximum likelihood genetic structural equation modelling (GSEM).

RESULTS

The genetic heritability estimates of angular variables describing horizontal mandibular position in relationship to cranial base and maxilla were considerably higher than in those describing vertical position. The mandibular skeletal cephalometric variables also showed high heritability estimates with angular measurements being considerably higher than linear ones. Results of this study indicate that the angular measurements representing mandibular skeletal morphology (mandibular form) have greater genetic determination than the linear measurements (mandibular size).

CONCLUSIONS

The shape and sagittal position of the mandible is under stronger genetic control, than is its size and vertical relationship to cranial base.

Heritability of thirty cephalometric parameters on monozygotic and dizygotic twins: twin study method

Genetic mechanisms are already predominant during embryonic craniofacial morphogenesis, but environment is also thought to influence dentofacial morphology postnatally, particularly during facial growth. A better understanding of the relative effects of genes and environment on dentofacial and occlusal parameters should improve our knowledge on the etiology of orthodontic disorders and therefore also on the possibilities and limitations of the orthodontic treatment and treatment planning. The aim of the present study is to explore the genetic and environmental influence on craniofacial dimensions in a group of 19 pairs of twins using the twin study method. The twin study carried out here clearly indicates that craniofacial matrix is under substantial genetic control and the redirection of a basic growth pattern may be modified only within biological limits which are harmonious for the patient.

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.

The influence of asthma on face shape: a three-dimensional study

Respiratory activity may have an influence on craniofacial development and interact with genetic and environmental factors. It has been suggested that certain medical conditions such as asthma have an influence on face shape. The aim of the study is to investigate whether facial shape is different in individuals diagnosed as having asthma compared with controls. Study design included observational longitudinal cohort study. Asthma was defined as reported wheezing diagnosed at age 7 years and 6 months. The cohort was followed to 15 years of age as part of the Avon Longitudinal Study of Parents and Children. A total of 418 asthmatics and 3010 controls were identified. Three-dimensional laser surface facial scans were obtained. Twenty-one reproducible facial landmarks (x, y, z co-ordinates) were identified. Average facial shells were created for asthmatic and non-asthmatic males and females to explore surface differences. The inter-ala distance was 0.4mm wider (95% CI) and mid-face height was 0.4mm (95% CI) shorter in asthmatic females when compared with non-asthmatic females. No facial differences were detected in male subjects. Small but statistically significant differences were detected in mid-face height and inter-ala width between asthmatic and non-asthmatic females. No differences were detected in males. The lack of detection of any facial differences in males may be explained by significant facial variation as a result of achieving different stages of facial growth due to pubertal changes, which may mask any underlying condition effect.

Le facteur ethnique est-il un indicateur thérapeutique?

Face au diktat de la beauté imposée par la société à travers des stéréotypes, il est devenu légitime de s’interroger sur le concept universel du “ beau ”. Est-ce que les normes esthétiques en orthodontie, établies à partir d’échantillons de Nord-Américains, peuvent être applicables à d’autres populations? Les différentes analyses céphalométriques menées chez des sujets afro-américains, africains et asiatiques en occlusion normale non traitée mettent en évidence des critères esthétiques éloignés des critères nord-américains. Leurs conclusions relatent comme principal caractère ethnique la biprotrusion alvéolo-dentaire en relation avec un angle naso-labial réduit. Pour le sujet africain, on note très fréquemment une antéro-position du maxillaire avec une position mandibulaire inchangée ou rétruse. Pour le sujet asiatique, une similitude des profils cutanés est rapportée avec une divergence quant aux profils squelettiques : les Japonais présentent une rétrognathie maxillaire plus prononcée; les Chinois montrent souvent une promaxilie et une rétromandibulie. Les Coréens se rapprocheraient des Japonais. Il semble donc nécessaire de constituer des données spécifiques à l’origine ethnique afin d’optimiser le diagnostic esthétique et les objectifs du traitement orthodontique.

Midfacial trauma and facial growth: a longitudinal case study of monozygotic twins

The purpose of this article is to present a long-term follow-up of the growth of the face and the nasomaxillary complex in a pair of identical twins, one of whom had suffered severe midfacial trauma at age 2 years. Growth of the face and the nasomaxillary complex was longitudinally assessed and compared by means of facial photographs and cephalometric x-rays. Twin A suffered Le Fort II and III fractures with an associated frontal bone injury in early childhood and subsequently developed significant midface hypoplasia; twin B had no trauma and normal facial growth and development. Facial profile difference between the twins gradually became more pronounced until age 19. Twin A had obvious retrusion of the midfacial region, including the nasal bones on visual examination and radiographic study. At age 20, she underwent orthognathic surgical correction of the traumatic deformity. Her unaffected sibling, twin B, provided the genetic facial phenotype for the surgical orthognathic reconstruction.

Cervical column morphology and craniofacial profiles in monozygotic twins

Previous studies have described the relationships between cervical column morphology and craniofacial morphology. The aims of the present study were to describe cervical column morphology in 38 pairs of adult monozygotic (MZ) twins, and compare craniofacial morphology in twins with fusions with craniofacial morphology in twins without fusion. Visual assessment of cervical column morphology and cephalometric measurements of craniofacial morphology were performed on profile radiographs. In the cervical column, fusion between corpora of the second and third vertebrae was registered as fusion. In the twin group, 8 twin pairs had fusion of the cervical column in both individuals within the pair (sub-group A), 25 pairs had no fusions (subgroup B), and in 5 pairs, cervical column morphology was different within the pair (subgroup C), as one twin had fusion and the other did not. Comparison of craniofacial profiles showed a tendency to increased jaw retrognathia, larger cranial base angle, and larger mandibular inclination in subgroup A than in subgroup B. The same tendency was observed within subgroup C between the individual twins with fusion compared with those without fusion. These results confirm that cervical fusions and craniofacial morphology may be interrelated in twins when analysed on profile radiographs. The study also documents that differences in cervical column morphology can occur in individuals within a pair of MZ twins. It illustrates that differences in craniofacial morphology between individuals within a pair of MZ twins can be associated with cervical fusion.

Impact of geometry and viewing angle on classification accuracy of 2D based analysis of dysmorphic faces

Digital image analysis of faces has been demonstrated to be effective in a small number of syndromes. In this paper we investigate several aspects that help bringing these methods closer to clinical application. First, we investigate the impact of increasing the number of syndromes from 10 to 14 as compared to an earlier study. Second, we include a side-view pose into the analysis and third, we scrutinize the effect of geometry information. Picture analysis uses a Gabor wavelet transform, standardization of landmark coordinates and subsequent statistical analysis. We can demonstrate that classification accuracy drops from 76% for 10 syndromes to 70% for 14 syndromes for frontal images. Including side-views achieves an accuracy of 76% again. Geometry performs excellently with 85% for combined poses. Combination of wavelets and geometry for both poses increases accuracy to 93%. In conclusion, a larger number of syndromes can be handled effectively by means of image analysis.

[Twins and the heritability of dentofacial phenotype]

In orthodontics and dentofacial orthopaedics, where genetic and environmental factors interpenetrate from the early stages of development, the clinician tries to determine how mechanics could influence patient's growth pattern. Comparing monozygotic and dizygotic twins, in their similarities and their differences, gives some answers... but raises some questions too. In this article, we gather some clinical studies and case reports, on diagnosis and treatment aspects of malocclusions.

Correlations between cephalometric and facial photographic measurements of craniofacial form

INTRODUCTION

The purpose of this study was to compare craniofacial measurements from cephalometric radiographs with analogous measurements from standardized facial photographs.

METHODS

The sample consisted of 326 subjects (168 white, 158 black) enrolled in a genetic epidemiological family study of sleep behavior. Traditional lateral cephalograms and standardized facial photographs were taken of each subject. Three angular, 3 linear, total face height, and lower face height cephalometric measurements were compared with 4 angular and 4 linear measurements from standardized photographs. Descriptive statistics for all measurements in the entire sample and for the racial subgroups were computed. Pearson product moment correlation coefficients were computed between analogous measurements, and intraclass correlation coefficients were calculated from repeated measurements on the photographs.

RESULTS

The reliability of the photographic technique was excellent, with all measurements having intraclass correlation coefficients above 0.90. However, the correlations between analogous photographic and cephalometric measurements were lower and varied between 0.356 and 0.643. The highest correlations were observed for lower facial height and mandibular length, 0.643 and 0.562, respectively. In the black group, the correlations between cephalometric and photographic measurements of mandibular length and lower facial height were 0.676 and 0.690, respectively. Both were higher than those for white subjects, 0.399 and 0.577, respectively.

CONCLUSIONS

Both linear and angular measurements useful for characterizing facial morphology can be reliably measured from facial photographs. However, only moderate correlations with analogous cephalometric measures were found. Therefore, standardized photographs and cephalograms most likely measure different aspects of facial morphology and cannot be used interchangeably. Cephalometrics remains the method of choice for clinical patient care, whereas photographs might be better for large-scale epidemiological studies, especially if there is a need for a low-cost, noninvasive method that be used in diverse clinical and field settings.

Secular change of craniofacial measures in Croatian younger adults

A secular change of body height and neurocranial variables was registered in the Croatian population during the last century. We investigated the continuity of this process, and introduced facial measurements into the study. The results cover a 13-year period, from the birth of the subjects in 1974-1986, with a gap in the period from 1977-1981. The subjects were first-year students of the University of Rijeka School of Medicine, aged 19-21 years. Secular changes were evaluated by analysis of variance and multivariate regression analysis. A statistically significant decrease was found in head breadth, and an increase in morphological face height values, in both sexes. A significant increase of head circumference was observed in female students. The height and length of the head in both sexes displayed a slight but insignificant increase, while face breadth revealed no notable change during the investigated period. The results allow an assumption of a trend of cranial vault and face shape remodeling in our younger adult population toward a narrower vault and more elongated face, consistent with ongoing dolichocephalization. The correlation analysis revealed a low to moderate relationship of vertical and longitudinal craniofacial measures and body height, while partial correlation analysis showed facial height changes in our sample to be independent of cranial breadth changes.