Need for orthognathic surgery in cleft patients from Northern Finland.

OBJECTIVE: Northern Finland has a unique distribution of clefts compared to the rest of Europe and Finland. This may reflect the need for orthognathic surgery among Northern Finland's patient pool. The aim of this study was to compare previously operated patients aged 18 years or older with cleft lip, cleft lip and alveolus, cleft lip and palate, cleft palate and to evaluate the need for orthognathic surgery in order to achieve a stable and functional occlusion.  Materials and methods: The study group consisted of all 18-years-old cleft patients treated in the Oulu Cleft Center. The total amount of patients was 110. The patients were compared retrospectively using patients' hospital records. The majority of patients did not have any cleft-associated syndrome. The need for maxillary or bimaxillary orthognathic or corrective-jaw surgery was evaluated by the Oulu Cleft Team. A descriptive and statistical analysis was used to determine the need for orthognathic surgery according to sex and cleft type. RESULTS: There were nineteen patients of the total of 110 patients who met the criteria requiring corrective-jaw surgery (17,3%). In total 12 males (25,0%) and 7 females (11,3%) were evaluated for the need of orthognathic surgery. Sixteen of the 19 patients had palatal involvement of the cleft. CONCLUSIONS: The need for orthognathic surgery was greater in the cleft lip palate and cleft palate patient groups compared to cleft lip alveolus or cleft lip groups. This study also found that males from Northern Finland need surgery more often than females.

A longitudinal study of facial asymmetry in a normal birth cohort up to 6 years of age and the predisposing factors.

OBJECTIVES: This prospective, population-based cohort study aimed to investigate the development of facial asymmetry up to 6 years of age using a three-dimensional (3D) soft tissue imaging method in a normal population. In addition, the study sought to identify potential predisposing factors to facial asymmetry. METHODS: A total of 102 newborns were enrolled in the study at birth. 3D stereophotogrammetric images of the head and face were analysed at the ages of 12 months (T1), 3 years (T2), and 6 years (T3). The surface-based analysis involved the calculation of the average distance (mm) and the symmetry percentage (%) between the original and mirrored surfaces. For landmark-based analysis, the distance of facial landmarks to the facial midline was examined. RESULTS: The final analysis included 70 (68.6%) subjects. Surface-based analysis showed a significant improvement of facial symmetry from T1 to T3 in all facial areas. Landmark-based analysis showed that upper facial landmarks were located, on average, slightly on the left and lower facial landmarks slightly on the right in relation to the facial midline (P < 0.001). LIMITATIONS: The size of the study population was limited. Facial posture may affect the reliability of the results, especially in younger children. CONCLUSION: Facial asymmetry is detectable in early childhood and tends to reduce with age in young children. The lower face deviates slightly to the right, and the upper face to the left in relation to the facial midline. Possible predisposing factors for facial asymmetry at the age of 6 years include deformational plagiocephaly, sleeping position, and previous facial asymmetry.

Facial asymmetry and chewing sides in twins.

OBJECTIVE: To resolve how the preferred chewing side (PCS) affects facial asymmetry in twins, whether there are differences between monozygotic (MZ) and dizygotic (DZ) twins, and whether the twins with PCS have more asymmetric faces compared to symmetrically chewing twins. MATERIAL AND METHODS: The study included 106 Lithuanian twin pairs of the same sex, 59 MZ and 47 DZ pairs. The data were analysed from facial 3D images and manually added landmarks. 3D images were analysed by Rapidform2006 software and statistical analyses were done by using the R software environment version 4.1.0. RESULTS: The contralateral effect of PCS and larger chin side was dominant among right and non-right side chewing twins. Being female increased the whole face symmetry. CONCLUSION: The volume of the chin becomes larger on the side opposite to the twins' habitual chewing side. As the results are quite similar in both twin types, functional factors are more prominent than heredity.

Maxillary Arch Dimensions in 6-Year-Old Cleft Children in Northern Finland: A Cross-Sectional Study.

The aim was to cross-sectionally examine the maxillary arch dimensions in 6-year-old children with cleft lip and/or palate and to compare them with the initial cleft sizes among patients with cleft palate. The study included 89 patients with clefts treated at the Oulu University Hospital. The subjects were divided into three groups: cleft palate, cleft lip, and cleft lip and palate. Study casts were scanned, and the maxillary arch dimensions were examined using a 3D program (3Shape Orthoanalyzer, Copenhagen, Denmark). The statistical methods Student's t-test and one-way ANOVA were used to compare the means (SD) between the groups. Spearman's correlation coefficient was used to determine the correlation between cleft severity and maxillary dimensions. A significant difference was found between different initial cleft sizes in terms of distance between the second deciduous molar and the first incisor on the right side. The intermolar width showed a negative correlation with the initial cleft size. The dimensions were shorter for clefts affecting the palate and largest for clefts affecting only the lip. Larger clefts resulted in a shorter maxilla on the right side. Many dimensions became shorter when the initial cleft was larger. Clefts of the palate resulted in smaller maxillas.

Dental fear among adolescents with cleft.

BACKGROUND: Dental fear is a prevalent phenomenon among children and adolescents globally. AIM: To investigate dental fear among 18-year-olds with cleft lip and/or palate (CLP) at their final follow-up cleft clinic visit, and to evaluate the association between dental fear and OHRQoL. DESIGN: This cross-sectional study included the cohort of children with CLP treated at the Oulu University Hospital Cleft Lip and Palate Center, in northern Finland since 1995. A total of 62 of 64 individuals participated in this study. The validated Finnish version of the Oral Health Impact Profile (OHIP-14) was used to assess OHRQoL. Dental fear was studied using the validated Modified Dental Anxiety Scale (MDAS) and cognitive vulnerability model (CVM). RESULTS: Almost two fifths of the participants reported moderate dental fear. Participants with cleft including lip and participants reporting impact on OHRQoL reported higher mean MDAS scores. In an unadjusted model, adolescents with cleft including lip had risk for higher dental MDAS scores compared with the ones with cleft including only palate. CONCLUSIONS: Dental fear is common among adolescents with CLP, specifically among those with clefts involving the lip. OHRQoL and dental fear seem to be associated.

Oral health-related quality of life among young adults with cleft in northern Finland.

OBJECTIVES: This study aimed to examine Oral Health-related Quality of Life (OHRQoL) among patients with cleft lip with or without palate (CLP) at their final scheduled follow-up visit at the age of 18 years. Another aim was to investigate the motivation to attend multiple follow-up appointments and the satisfaction with care given by the cleft team using inductive qualitative analysis. METHODS: This cross-sectional study was conducted among the cohort of children born with CLP who had undergone treatment at the Oulu University Hospital Cleft Lip and Palate Centre, in northern Finland since 1995. OHRQoL was assessed using the validated Finnish version of the short form of the Oral Health Impact Profile (OHIP-14). In addition to the OHIP-14, two open-ended questions were also included. These questions investigated the experience of each participant concerning their motivation to attend the Oulu University Hospital Cleft Lip and Palate Centre to receive complex treatments, and their satisfaction with care provided by the cleft team. Results were presented as proportions, means, and SD. Inductive content analysis method was performed for analysis of the open-ended questions. RESULTS: A total of 63 patients with CLP participated in this study. More than half of the participants had cleft palate. More than half of the participants reported an impact on OHRQoL (OHIP-14 score ≥ 3). All the participants with bilateral cleft lip and palate, three fourths of the participants with unilateral cleft lip and palate, and half of the participants with cleft palate reported impact on OHRQoL. Inductive content analysis showed that one fourth of the participants reported a good outcome as a motivation to attend cleft center despite of complex procedures. All the participants reported their appreciation of the cleft team. CONCLUSIONS: Despite the comprehensive treatment received by the patients born with a CLP, they still experienced lower OHRQoL, especially physical pain and psychological discomfort were more pronounced. However, good outcome, support, and oral health care being a normal routine were the motivating factors to attend a long and demanding oral health care regimen.

Exploring the midline soft tissue surface changes from 12 to 15 years of age in three distinct country population cohorts.

INTRODUCTION: Several studies have highlighted differences in the facial features in a White European population. Genetics appear to have a major influence on normal facial variation, and environmental factors are likely to have minor influences on face shape directly or through epigenetic mechanisms. AIM: The aim of this longitudinal cohort study is to determine the rate of change in midline facial landmarks in three distinct homogenous population groups (Finnish, Latvian, and Welsh) from 12.8 to 15.3 years of age. This age range covers the pubertal growth period for the majority of boys and girls. METHODS: A cohort of children aged 12 were monitored for facial growth in three countries [Finland (n = 60), Latvia (n = 107), and Wales (n = 96)]. Three-dimensional facial surface images were acquired (using either laser or photogrammetric methods) at regular intervals (6-12 months) for 4 years. Ethical approval was granted in each country. Nine midline landmarks were identified and the relative spatial positions of these surface landmarks were measured relative to the mid-endocanthion (men) over a 4-year period. RESULTS: This study reports the children who attended 95 per cent of all scanning sessions (Finland 48 out of 60; Latvia 104 out of 107; Wales 50 out of 96). Considerable facial variation is seen for all countries and sexes. There are clear patterns of growth that show different magnitudes at different age groups for the different country groups, sexes, and facial parameters. The greatest single yearly growth rate (5.4 mm) was seen for Welsh males for men-pogonion distance at 13.6 years of age. Males exhibit greater rates of growth compared to females. These variations in magnitude and timings are likely to be influenced by genetic ancestry as a result of population migration. CONCLUSION: The midline points are a simple and valid method to assess the relative spatial positions of facial surface landmarks. This study confirms previous reports on the subtle differences in facial shapes and sizes of male and female children in different populations and also highlights the magnitudes and timings of growth for various midline landmark distances to the men point.

Plagiocephaly after Neonatal Developmental Dysplasia of the Hip at School Age.

Developmental dysplasia of the hip (DDH) may require early abduction treatment with infants sleeping on their back for the first few months of life. As sleeping on back is known to cause deformational plagiocephaly, we assessed school age children treated for dislocation or subluxation of the hip-joint in infancy. Plagiocephaly was analyzed by using cephalic index (CI) and oblique cranial length ratio (OCLR) as anthropometric measurements from 2D digital vertex view photographs. Six of the 58 (10.3%) DDH children and only one of the 62 (1.6%) control children had plagiocephaly (p = 0.041). Furthermore, cross bite was found in 14 (24.1%) of the DDH children and in 7 (10.3%) of the control children. Developmental dysplasia of the hip in infancy was associated with cranial asymmetries and malocclusions at school age. Preventive measures should be implemented.

A 3D Follow-Up Study of Cranial Asymmetry from Early Infancy to Toddler Age after Preterm versus Term Birth.

Preterm infants are at higher risk for both symmetrical and asymmetrical head molding. This study involved 3D stereophotogrammetry to assess the cranial growth, molding, and incidence of deformational plagiocephaly (DP) in preterm children compared to term born children. Thirty-four preterm infants and 34 term born controls were enrolled in this study from Oulu University Hospital, Finland. Three-dimensional head images were obtained at the age of 2-4 months (T1), 5-7 months (T2), 11-13 months (T3), and 2.5-3 years (T4) from the term equivalent age (TEA). There was no statistically significant difference in oblique cranial length ratio (OCLR), cephalic index (CI), or weighted asymmetry score (wAS) between the two groups. Occipital flattening, defined by flatness score (FS) was statistically significantly greater in the preterm group than in the term group at T1-T4 (p < 0.05). In both groups, OCLR improved gradually over time. There were no instances, in either group, of severe DP and no moderate DP after T2. Results indicate that DP affects preterm and full-term children almost equally during the first three years of life, and cranial asymmetry resolves at a similar rate in both preterm and term groups after three months of corrected age. Preterm infants present with more occipital flattening than full-term children.

Relations of laterality and chewing sidedness in twins.

OBJECTIVES: To study, whether there are associations between chewing side preference and other lateralities, whether there is a genetic origin for preferred chewing side (PCS), relations to sex, birth order and orthodontic treatment. MATERIALS AND METHODS: The study included 113 twin pairs, 57 pairs monozygotic, 47 pairs same sex dizygotic and 9 pairs of opposite sex. The lateralities of preferred chewing side, footedness and eyedness were assessed by functional tests and handedness was checked by asking. RESULTS: Right-handed, -footed and -eyed as separated groups, and true-right sided (combined), were evenly distributed by preferred chewing side. By contrast, left-handed, -footed, -eyed and non-right sided used more left or both sides when chewing. Birth order affected preferred chewing side among monozygotic: the first-born twin was more likely to have the preferred chewing side on the non-right, whereas second-born twins used right side. Gender, zygosity and orthodontic treatment were not statistically significant factors. LIMITATIONS: Examination of chewing sidedness could have been done in several different ways to provide a definite result. Sample size of opposite sex twins was very small. CONCLUSIONS: Preferred chewing side generally seemed to follow the side where other lateralities occur; however, monozygotic twins seemed to be more receptive to it. True-right sided were more evenly distributed than non-right sided by the preferred chewing side.

Craniofacial Asymmetry from One to Three Years of Age: A Prospective Cohort Study with 3D Imaging.

Deformational plagiocephaly (DP) is considered a risk factor for facial asymmetry. This cohort-based, prospective, follow-up study used three-dimensional (3D) stereophotogrammetry to assess the development of facial asymmetry in a normal birth cohort and to investigate the impact of DP on facial asymmetry for the age range of one to three years. The study sample consisted of 75 children: 35 girls (47%) and 40 (53%) boys recruited from Oulu University Hospital. A total of 23 (31%) subjects had a history of DP in infancy. 3D facial images were obtained at the mean (SD) age of 1.01 (0.04) year old at T1 and 3.02 (0.14) years old at T2. To determine facial asymmetry, both landmark-based and surface-based facial symmetry methods were used. As measured with the surface-based methods, upper facial symmetry improved from T1 to T2 (p < 0.05). As measured with the landmark-based methods, facial symmetry improved on the upper and lower jaw from T1 to T2 (p < 0.05). The asymmetric effect of DP on the upper parts of the face tends to correct spontaneously during growth. Results indicate that previous DP does not seem to transfer to facial or occlusal asymmetry at the age of three years old.

Childhood intelligence and early tooth wear patterns.

OBJECTIVE: The aim of this study is to explore the relationships between early dental wear patterns and preschool IQ (Intelligence Quotient, by Stanford-Binet) of the child to illuminate the historic relationship of mental queries and bruxism. METHODS: The dental study participants were 864 Euro-American preschool and school children whose IQs were tested for school maturity purposes at the age of 4 years, followed by dental data in a cross-sectional manner at the mean age of 7.8 years. Worn dentitions were classified as "symmetric" or "right-" and "left-sided," based on the faceting of the teeth. RESULTS: In general, the relationships of tooth wear and intelligence were scarce, reflecting social background factors. Statistically significant results between asymmetric wear and gender groups suggest that direction of jaw function has a role in the regulation of processes responsible for individual mental performance in childhood. DISCUSSION: Increased left-side tooth wear and early advantage in the intelligence test in girls is intriguing due to the fact that they reach maturity earlier than boys in verbal articulation, controlled in most cases by the limited area on the left side of the brain.

Accuracy of measurements used to quantify cranial asymmetry in deformational plagiocephaly.

OBJECTIVE: Various measurements are used to quantify cranial asymmetry in deformational plagiocephaly (DP), but studies validating cut-off values and comparing the accuracy of such measurements are lacking. In this study, we compared the accuracy of four different measurements in classifying children with and without DP diagnosed by visual assessment, and sought to determine their optimal cut-off values. STUDY DESIGN: Two experts rated 407 3D craniofacial images of children aged between 3 and 36 months old using the Argenta classification. We then measured the following asymmetry-related variables from the images: Oblique Cranial Length Ratio (OCLR), Diagonal Difference (DD), Posterior Cranial Asymmetry Index (PCAI), and weighted Asymmetry Score (wAS). We created receiver operating characteristic curves to evaluate the accuracy of these variables. RESULTS: All variables performed well, but OCLR consistently provided the best discrimination in terms of area under the curve values. Subject's age had no clear effect on the cut-off values for OCLR, PCAI, and wAS; however, the cut-off for DD increased monotonically with age. When subjects with discrepant expert ratings were excluded, the optimal cut-off values for DP (Argenta class ≥ 1) across all age-groups were 104.0% for OCLR (83% sensitivity, 97% specificity), 10.5% for PCAI (90% sensitivity, 90% specificity), and 24.5 for wAS (88% sensitivity, 90% specificity). CONCLUSION: We recommend using OCLR as the primary measurement, although PCAI and wAS may also be useful in monitoring cranial asymmetry. The threshold of relative asymmetry required for a deformation to appear clinically significant is not affected by the child's age, and DD has no additional utility in monitoring DP compared to using only OCLR.

The course of positional cranial deformation from 3 to 12 months of age and associated risk factors: a follow-up with 3D imaging.

Deformational plagiocephaly is reported in up to 46.6 % of healthy infants, with the highest point prevalence at around 3 months of age. Few prospective studies on the natural course of skull deformation have been conducted, and we know of no studies using 3D imaging starting from the highest point prevalence period. In this prospective, population-based cohort study, we describe the course of cranial asymmetry and shape in an unselected population using 3D stereophotogrammetry and investigate factors associated with late cranial deformation and failure to recover from previous deformation. We evaluated 99 infants at 3, 6, and 12 months of age. We acquired 3D craniofacial images and performed structured clinical examinations and parental interviews at each visit. Eight outcome variables, representing different aspects of cranial shape, were calculated from a total of 288 3D images. Scores of asymmetry-related variables improved throughout the observation period. However, the rate of correction for cranial asymmetry decreased as the infants grew older, also in relation to the rate of head growth, and a significant amount of asymmetry was still present at 12 months. Positional preference at 3 months predicted an unfavorable course of cranial asymmetry after 3 months, increasing the risk for DP persisting. What is known: • The prevalence of deformational plagiocephaly spontaneously decreases after the first months of life. • Limited neck range of motion and infant positional preference increase the risk of deformational plagiocephaly during the first months of life. What is new: • Positional preference at 3 months predicts an unfavorable spontaneous course of deformation also from three to 12 months of age, presenting a potential target for screening and treatment. • The spontaneous rate of correction for cranial asymmetry decreases after 6 months of age, also in relation to the rate of head growth.

Analyzing infant head flatness and asymmetry using kernel density estimation of directional surface data from a craniofacial 3D model.

Infant skull deformation is analyzed using the distribution of head normal vector directions computed from a 3D image. Severity of flatness and asymmetry are quantified by functionals of the kernel estimate of the normal vector direction density. Using image data from 99 infants and clinical deformation ratings made by experts, our approach is compared with some recently suggested methods. The results show that the proposed method performs competitively. Copyright © 2016 John Wiley & Sons, Ltd.

Middle ear findings and need for ventilation tubes among pediatric cleft lip and palate patients in northern Finland.

PURPOSE: Middle ear problems are common in cleft patients. This study aimed to determine the need for ventilation tubes (VTs) and complications such as tympanic perforation and cholesteatoma. MATERIAL AND METHODS: Data of 156 children with clefts managed in northern Finland spanning 15 years from 1997 to 2011 were collected from 6 hospitals. The following were recorded: birth date, gender, cleft type, surgery timing, surgery type, number of tube insertions, tube material, middle ear findings, and tube placement timing. Clefts were divided into 4 groups: cleft palate (CP), cleft lip and palate (CLP), cleft lip (CL), and submucous cleft palate. The prevalence of middle ear findings was reported. RESULTS: Mucous secretion was noted in 96.8% of CLP patients, 69.2% of CP patients, and 13.0% of CL patients. In all, 82.7% of study group had 1 or more VTs placed during follow-up. All CLP patients required more than 1 VT placement. A total of 94.5% of CP patients required VTs compared to 13.0% of CL patients. In the presence of residual oral nasal fistula, the mean number of tube insertions was 5.3. The prevalence of tympanic perforations in clefts was 35.9% and cholesteatoma in 2.6% of patients. CONCLUSIONS: CLP and isolated CP patients have frequent middle ear infections requiring multiple VT placements.

The association of cleft severity and cleft palate repair technique on hearing outcomes in children in northern Finland.

BACKGROUND: The consequences of cleft lip and palate include scaring, dental malformations, tooth misalignment, speech problems, and hearing loss. Otitis media with effusion causing hearing loss is a problem for many cleft palate patients. METHODS: This study examines the association among cleft severity, palate repair technique, and hearing outcomes in children from northern Finland with clefts, aged 3-9 years. The study included 90 cleft patients who were treated at the Oulu University Hospital Cleft Lip and Palate Center between 1998 and 2011. The severity of the cleft, the surgical technique used to repair the palate, audiogram configuration data, and the need for ventilation tube placement were determined retrospectively from patient records. RESULTS: Only 3.3% of cleft patients had an abnormal pure tone average hearing threshold representing abnormal hearing. Neither the surgical technique used to repair the cleft palate nor the severity of the cleft was a significant factor related to hearing loss or to the number of ventilation tubes required. Hearing improved significantly with increasing age over a span of 6 years. CONCLUSIONS: Continuous follow-up with proactive placement of ventilation tubes before or at the time of palatoplasty results in hearing outcomes in cleft children that are similar to those reported in non-cleft children.

Dental treatment need and dental general anesthetics among preschool-age children with cleft lip and palate in northern Finland.

Cleft lip and palate incidence is high in northern Finland. This study aimed to investigate the proportion of children in need of restorative dental treatment among cleft lip and palate patients in northern Finland, as well as their need for dental treatment under general anesthesia. The records of 183 cleft lip and palate patients, treated in Oulu University Hospital from 1997 to 2013, were reviewed. Data on dental caries were analyzed in association with cleft type, considering also the presence of syndromes. The frequency of dental general anesthetic (DGA) use, and of treatments, were also analyzed. Dental treatment need was most frequently observed, in this rather limited study population, in patients with the most severe deformities, namely bilateral cleft lip and palate, of whom 60% had caries. Among the study population, 11.5% (n = 21) had a syndrome. Of those, 57.1% had dental caries at the age of 3 or 6 yr, and only four could be treated without a DGA. Dental treatment under general anesthesia was performed in 14.8% of cleft patients without a syndrome, but in 38.1% of those with a syndrome. General anaesthesia is required for the provision of dental care more often in cleft (17.5%) than in non-cleft (0.2%) patients, and especially for those with a syndrome.

Preventing deformational plagiocephaly through parent guidance: a randomized, controlled trial.

Deformational plagiocephaly (DP) occurs frequently in otherwise healthy infants. Many infants with DP undergo physiotherapy or helmet therapy, and ample treatment-related research is available. However, the possibility of preventing DP has been left with little attention. We sought to evaluate the effectiveness of intervention in the newborn's environment, positioning, and handling on the prevalence of DP at 3 months and to investigate the causal relationship between DP and cervical imbalance. We carried out a randomized controlled trial, with healthy newborns randomized into two groups at birth. All families received standard positioning instructions to prevent SIDS. Additionally, the intervention group received detailed instructions regarding the infant's environment, positioning, and handling, with the goal of creating a nonrestrictive environment that promotes spontaneous physical movement and symmetrical motor development. Two- and three-dimensional photogrammetry served to assess cranial shape and goniometry to measure cervical motion. At 3 months, the prevalence of DP was lower in the intervention group in both 2D (11 vs 31 %) and 3D analyses (15 vs 33 %), and the asymmetry was milder in the intervention group. Infants with DP at follow-up had also developed more torticollis. CONCLUSION: An early educational intervention reduces the prevalence and severity of DP at 3 months. WHAT IS KNOWN: •Deformational plagiocephaly, often with associated torticollis, is common in healthy infants. •Parental education is frequently recommended for preventing deformational plagiocephaly, although information regarding the effectiveness of preventive strategies is scarce. WHAT IS NEW: •Early parent guidance effectively reduces the prevalence and severity of DP and improves the cervical range of motion at three months. •Educating both parents and professionals about proper infant positioning on a national scale could help minimize public healthcare costs.

Comparing Facial 3D Analysis With DNA Testing to Determine Zygosities of Twins.

The aim of this study was to compare facial 3D analysis to DNA testing in twin zygosity determinations. Facial 3D images of 106 pairs of young adult Lithuanian twins were taken with a stereophotogrammetric device (3dMD, Atlanta, Georgia) and zygosity was determined according to similarity of facial form. Statistical pattern recognition methodology was used for classification. The results showed that in 75% to 90% of the cases, zygosity determinations were similar to DNA-based results. There were 81 different classification scenarios, including 3 groups, 3 features, 3 different scaling methods, and 3 threshold levels. It appeared that coincidence with 0.5 mm tolerance is the most suitable feature for classification. Also, leaving out scaling improves results in most cases. Scaling was expected to equalize the magnitude of differences and therefore lead to better recognition performance. Still, better classification features and a more effective scaling method or classification in different facial areas could further improve the results. In most of the cases, male pair zygosity recognition was at a higher level compared with females. Erroneously classified twin pairs appear to be obvious outliers in the sample. In particular, faces of young dizygotic (DZ) twins may be so similar that it is very hard to define a feature that would help classify the pair as DZ. Correspondingly, monozygotic (MZ) twins may have faces with quite different shapes. Such anomalous twin pairs are interesting exceptions, but they form a considerable portion in both zygosity groups.