Gender and age differences in facial expressions

The aim of this research was to determine a reliable method for quantitatively evaluating the facial expressions of children and adults in order to assess their dependence on age and gender. This study evaluated 80 healthy subjects divided into four groups: 20 girls (mean age 10.6 years), 20 boys (mean age 10.8 years), 20 females (average age 25.6 years), and 20 males (average age 27.0 years). A video was used to record each individual executing three facial expressions: a rest pose, a lip pucker, and a posed smile. Representative video frames were chosen for each individual's expressions; they were digitized and then analysed with software that extracted a set of horizontal and vertical distances of the face. All distances measured in the posed smile and lip pucker were expressed as a percentage change from the rest pose. Statistical analysis with a two-way multivariate analysis of variance (MANOVA) was performed, with gender and age as the independent variables. It was evident that the ability to produce certain facial expressions differs between groups of individuals due to gender and age. Males had a greater upward vertical movement capacity in the studied facial expressions than females. Females had a more pronounced horizontal component in the posed smile. There was a trend from childhood to adulthood showing an increase in the percentage change in most vertical movements. This trend was present in both genders, though more pronounced in males. Using a robust quantitative method for collecting and analysing facial expressions, gender differences in adults were detected as well as differences between adults and children. The trend toward increasing vertical movements in adults compared with children suggests the possibility that the mimic musculature is developmentally regulate

Evaluation of tooth position, occlusion, and interproximal contacts after transplantation of immature third molars

The aim of the present investigation was to examine position, occlusion, and interproximal contacts of 139 transplanted third molars in 136 patients (94 females, 42 males) with a mean age of 17.6 years at the time of transplantation. Ninety-two teeth were placed directly into favourable positions and left to erupt spontaneously. Forty-seven teeth were transplanted into atrophied jaw sections and underwent post-operative orthodontic adjustment. According to the post-operative treatment performed, the sample was divided into two groups: transplants with or without subsequent orthodontic treatment. The mean post-operative observation time was 4.4 years. Study models were obtained from all patients and the American Board of Orthodontics Objective Grading System was adapted for evaluation of position, occlusion, and interproximal contacts of the transplanted teeth. A Mann-Whitney U-test was used to determine significant intergroup differences with respect to the final scores and the various evaluated criteria. Absence of occlusal contacts was found in more than 30 per cent, absence of both interproximal contacts in more than 15 per cent, and inadequate position in more than 40 per cent of the transplants without subsequent orthodontic treatment. The poorest results were observed for maxillary teeth transplanted into the mandible. The results of the present study show that incorrect positioning with absence of occlusal and interproximal contacts are frequent findings in transplanted teeth. Short-term orthodontic adjustment, especially of maxillary transplants into the mandible, seems to be advisable in order to obtain correct positioning and function of these teet

Three-dimensional changes in the position of unopposed molars in adults

The aim of this study was to longitudinally examine, in adults, changes of position in the three dimensions of maxillary molars unopposed for more than 10 years. Twelve healthy mature adults (six males, six females; mean age 45 years 11 months) with unopposed molars were followed-up for a mean period of 10 years 7 months. Plaster casts were made at the first and last examination. The patients presented 22 unopposed maxillary molars at both recordings and 14 posterior teeth with antagonists, at least one in each subject, without significant modifications during the study period. On three-dimensional scanned plaster casts, changes in the centroid of the occlusal surface were measured in the three dimensions. The changes observed on both occasions were compared with a t-test. Vertical displacement of unopposed molars [0.8 mm, standard deviation (SD) 0.65 mm] and controls (0.4 mm, SD 0.2 mm) was noted. The unopposed teeth overerupted more than the controls (P ≤ 0.06); periodontally affected molars erupted more than periodontally healthy molars (P ≤ 0.01). There was significant mesial displacement of unopposed molars without mesially adjacent teeth when compared with their respective controls (P ≤ 0.04). Palatal movement was observed in the unopposed teeth (0.9 mm, SD 0.6 mm) and was significantly greater than that in the controls (0.5 mm, SD 0.3 mm; P ≤ 0.02). There is displacement of unopposed teeth in the three dimensions in the long term, although this is clinically insignificant in periodontally healthy adults. The observed changes are either the result of late growth remodelling or a consequence of altered dental equilibrium following antagonist tooth los

Masseter muscle thickness and maxillary dental arch width

The purpose of the present investigation was to study the relationship between the ultrasonographic thickness of the masseter muscle and the width of the maxillary dental arch. The sample comprised 60 consecutive orthodontic patients (37 females, 23 males), 7-18 years of age with a Class I relationship and minor malocclusion. The thickness of the masseter muscle was measured ultrasonographically. Recordings were performed bilaterally with the muscles both in relaxation and under contraction. Maxillary intermolar width was measured with an electronic calliper as the distance between the palatal surfaces of the first permanent molars. Intermolar width showed no association with age and gender. However, masseter muscle thickness showed a direct, significant (P < 0.0001) association with these two factors together, i.e. the masseter muscle was thicker in older individuals and in males. In the female group, maxillary intermolar width showed a direct, significant association with masseter thickness both during contraction (P < 0.006) and relaxation (P < 0.013), i.e. females with thicker masseter muscles had a wider maxillary dental arch. In the male group, however, no significant relationship was found between maxillary intermolar width and masseter thickness. The findings of this study indicate that the functional capacity of the masticatory muscles may be considered as one of the factors influencing the width of the maxillary dental arc

Facial palsy in individuals with thalidomide embryopathy: frequency and characteristics

Abstract Background: Earlier studies have shown that individuals with thalidomide embryopathy can have skeletal deformities, ear and eye aberrations, and facial palsy. This study aimed to survey the frequency and characteristics of facial palsy in this group of individuals. Participants: Thirty-one individuals with thalidomide embryopathy (age range, 45-47 years) and 25 healthy adults (age range, 41-56 years; mean age±standard deviation, 49±4.2 years). Main outcome measures: Voluntary facial movements, lip force and three-dimensional lip motion analysis. Results and conclusion: Four of the thalidomide embryopathy individuals (13 per cent) had congenital facial palsy. All four had eye aberrations, three had ear anomalies and one had a limb anomaly. Individuals with thalidomide embryopathy without a clinical diagnosis of facial impairment had significantly weaker lips and more restricted lip mobility than healthy controls. This study contributes to the overall knowledge of thalidomide embryopathy by adding a description of how facial expression can be affected in this conditio

Predictive value of masseter muscle thickness and bite force on Class II functional appliance treatment: a prospective controlled study

SummaryAim: To prospectively evaluate the functional capacity of the masticatory musculature as a predictive variable in determining functional appliance treatment outcomes in Class II/1 malocclusion children. Methods: Twenty Class II/1 malocclusion children (11.4±1.7 years) were treated with functional appliances during 1 year. Masseter muscle thickness and maximal molar bite force measurements, lateral cephalograms, and study casts were taken before and after treatment. Twenty age- and gender-matched untreated children were included as a control group. Regression analyses were used to identify correlations between pre-treatment muscle characteristics and treatment outcomes. Results: All treated patients showed dentoalveolar sagittal improvement. Maximal molar bite force and masseter muscle thickness decreased during the treatment period in the experimental group but increased in the control group. Children with lower pre-treatment maximal molar bite force showed more mesial movement of mandibular first molars, distal movement of maxillary first molars, and larger change in molar class during treatment. Children with thinner pre-treatment masseter muscles demonstrated more mandibular first molar mesialisation, mandibular incisor proclination, and opening of the gonial angle during treatment. Conclusions: The initial condition of the masticatory muscles may partly determine treatment outcomes. Children with thinner pre‐treatment masseter muscles or weaker bite force show greater dentoalveolar change

Dentofacial characteristics of growing patients with Duchenne muscular dystrophy: a morphological study

Occlusal traits and craniofacial morphology were studied in growing patients with Duchenne muscular dystrophy (DMD). Sixteen patients from 6 to 20 years of age were examined and compared with 16 healthy male individuals matched according to age. The dental arches and occlusal traits of both groups were analysed on dental casts and compared with the norms of healthy individuals from the literature. Lateral cephalograms of the patients were compared with normal individuals by using scored values based on standard deviations in order to compensate for heterogeneity in the age of the subjects. Statistical analysis was undertaken for continuous variables with a paired Student's t-test and non-continuous variables with a chi-square test. Linear regressions were used to evaluate the influence of age. A high prevalence of malocclusions was found, including posterior crossbites, anterior and lateral open bites, a tendency towards mesio-occlusion due to a skeletal Class III malocclusion, and dental compensations of the Class III relationship by retrusion of the lower incisors. Both upper and lower arches were widened posteriorly. The lower arches were even wider than the upper arches, resulting in frequent posterior crossbites. No significant skeletal vertical deviations were observed in this group of DMD patients, except for the maxillary plane angle (NL/NSL) that was larger than normal, while the anterior upper face height (NSp) was smaller. However, no difference was found in lower face height. The posterior enlargement of the dental arches and the dentoalveolar development towards an Angle Class III relationship were significantly related to age and found more frequently among the older subject

Craniofacial Cephalometric Characteristics and Open Bite Deformity in Individuals with Amelogenesis Imperfecta-A Systematic Review and Meta-Analysis.

BACKGROUND Individuals with amelogenesis imperfecta (AI) often present with malocclusions, especially a dental or skeletal anterior open bite (AOB). OBJECTIVES To evaluate the craniofacial characteristics in individuals with AI. MATERIAL AND METHODS A systematic literature search was conducted with the PubMed, Web of Science, Embase and Google Scholar databases to identify studies relating to the cephalometric characteristics of individuals with AI, without any language or publication date restrictions. The grey literature was searched using Google Scholar, Opengrey and Worldcat. Only studies with a suitable control group for comparison were included. Data extraction and a risk of bias assessment were carried out. A meta-analysis was performed using the random effects model for cephalometric variables that were evaluated in at least three studies. RESULTS The initial literature search yielded 1857 articles. Following the removal of duplicates and a screening of the records, seven articles were included in the qualitative synthesis, representing a total of 242 individuals with AI. Four studies were included in the quantitative synthesis. The meta-analysis results showed that individuals with AI present a smaller SNB angle and larger ANB angle than those of control groups in the sagittal plane. In the vertical plane, those with AI present a smaller overbite and larger intermaxillary angle than those without AI. No statistically significant differences were found for the SNA angle when comparing the two groups. CONCLUSIONS Individuals with AI seem to present with more vertical craniofacial growth, leading to an increased intermaxillary angle and decreased overbite. This possibly leads to a more retrognathic mandible with a larger ANB angle due to an anticipated posterior mandibular rotation

Predictive value of molar bite force on Class II functional appliance treatment outcomes

Sagittal intermaxillary changes brought about by functional appliances show large inter-individual variation. One factor that may in part explain these differences is the masticatory musculature and its functional capacity. The aims of this study were to investigate changes in maximal molar bite force during functional appliance treatment and to assess the influence of pre-treatment maximal molar bite force on treatment outcomes with functional appliances used in Class II malocclusion children. Twenty-five children (17 males and 8 females), aged 9-13 years, with a Class II malocclusion and increased overjet were treated with functional appliances for 1-2 years. Dental casts, lateral cephalograms, maximal molar bite force, and finger force measurements were performed before (T1) and after (T2) treatment. These same measurements were also performed 1-2 years before treatment (T0); the intermediate period before starting treatment served as the control. Multiple regression analyses were used to determine possible correlations between initial maximal molar bite force and dental or cephalometric changes during treatment. Maximal molar bite force, which increased pre-treatment (T0-T1), decreased during functional appliance treatment (T1-T2). Children with a weaker T1 maximal molar bite force showed a larger overjet reduction, greater improvement in molar relationship, greater reduction in ANB angle, and greater augmentation in SNB angle from T1 to T2. Treatment of children with Class II malocclusions with functional appliances seems to lead to more favourable treatment outcomes in those with a weaker maximal molar bite force. This was observed both as regards improvements in dental sagittal relationships, namely overjet and molar Class, as well as skeletal changes due to a decrease in ANB and an increase in SNB angle

Orthodontists' and laypersons' aesthetic assessment of Class III subjects referred for orthognathic surgery

This study was undertaken to compare laypersons' and professionals' perception of soft tissue profiles of Class III adults, and to evaluate which cephalometric variables are likely to influence the profile assessment score (PAS). Lateral headfilms and coloured profile photographs of 18 skeletal Class III Caucasian adult patients (10 males, 8 females with a mean age of 24.5 years) prior to surgery, and nine adult Caucasian patients (four males, five females with a mean age of 27.4 years) with a dental Class I occlusion and no major skeletal discrepancy were included in the study. The headfilms were hand traced and digitized. Various cephalometric variables were calculated by computer software. Each printed profile photograph was evaluated aesthetically by 18 laypersons and 18 orthodontists using a 10-graded visual analogue scale (VAS) and a standard profile for calibration. Intra-observer reliability was tested and no significant error was found. Paired and unpaired t-tests were used to compare the scores. The association between various cephalometric variables and the PAS was tested. In general, compared with orthodontists, laypersons were less critical in their evaluation of the Class III profiles (+0.3 grade on the VAS) as well as the reference profiles (+0.7). The reference profiles were found to be more attractive than the Class III profiles by both laypersons and orthodontists (+2.3 grades). The degree of facial concavity had a negatively predictive value for the orthodontists' and laypersons' evaluations. The degree of facial concavity together with the steepness of the mandibular plane were negatively predictive factors for the PAS given by the orthodontist