What is a trait? Lessons from the human chin.

The chin, a distinguishing feature of Homo sapiens, has sparked ongoing debates regarding its evolutionary origins and adaptive significance. We contend that these controversies stem from a fundamental disagreement about what constitutes a well-defined biological trait, a problem that has received insufficient attention despite its recognized importance in biology. In this paper, we leverage paleoanthropological research on the human chin to investigate the general issue of character or trait identification. First, we examine four accounts of the human chin from the existing literature: the mandibular differential growth byproduct, the bony prominence, the inverted T-relief, and the symphyseal angle. We then generalize from these accounts and propose a three-stage framework for the process of character identification: description, detection, and justification. We use this framework to reinterpret the four accounts, elucidating key points of contention surrounding the chin as well as other morphological characters. We show that debates over the chin carry broad and important biological implications that extend beyond this trait and that are not mere semantic issues of definition.

Facial morphology differences in monozygotic twins: a retrospective stereophotogrammetric study.

OBJECTIVE: To assess soft tissue differences between monozygotic twins (MZ) for the total face and between facial regions using three-dimensional (3D) stereophotogrammetry and quantitative surface-based 3D deviation analyses. MATERIALS AND METHODS: The study sample consisted of 14 untreated MZ twins (6 males, 8 females, mean age: 14.75 years) from the archive of Marmara University, Department of Orthodontics. The images were taken by the 3dMDface system, and 3dMDvultus software was used for removal of undesired areas and approximation of the images. Then, stereolithography (.stl) format images were superimposed using the best-fit algorithm using 3-matic software. The face was divided into facial thirds, and upper lip and lower lip + chin regions were created. For the comparison, 3D deviation analyses were performed, and a color map and histogram were created. The data were presented as mean deviation, root mean square (RMS), median, and interquartile range. RESULTS: Between the facial thirds, there was no significant difference in soft tissue differences for mean deviation. A statistically significant difference was found between the upper and lower face for the RMS value. For the comparison of upper lip and lower lip + chin region, the only significant difference was for the RMS. When the data were presented as median and interquartile range, there were no statistically significant differences between any facial regions. CONCLUSIONS: Lower facial third and lower lip + chin regions had the greatest differences within MZ twin pairs. The genetic and environmental influences might not be the same for different parts of the face.

Accuracy in predicting soft tissue changes of orthodontic class III cases using Dolphin® software.

OBJECTIVES: The prediction of posttreatment outcomes is conducive to the final determination of ideal therapeutic options. However, the prediction accuracy in orthodontic class III cases is unclear. Therefore, this study conducted exploration on prediction accuracy in orthodontic class III patients using the Dolphin® software. MATERIALS AND METHODS: In this retrospective study, lateral cephalometric radiographs of pre- and posttreatment were collected from 28 angle class III adults who received completed non-orthognathic orthodontic therapy (8 males, 20 females; mean age = 20.89 ± 4.26 years). The values of 7 posttreatment parameters were recorded and inserted into the Dolphin® Imaging software to generate a predicted outcome, and then the prediction radiograph and actual posttreatment radiograph were superimposed and compared in terms of soft tissue parameters and landmarks. RESULTS: The prediction showed significant differences with the actual outcomes in nasal prominence (the difference between the prediction and the actual value was - 0.78 ± 1.82 mm), the distance from the lower lip to the H line (0.55 ± 1.11 mm), and the distance from the lower lip to the E line (0.77 ± 1.62 mm) (p < 0.05). Point subnasale (Sn) (an accuracy of 92.86% in the horizontal direction and 100% in the vertical direction in 2 mm) and point soft tissue A (ST A) (an accuracy of 92.86% in the horizontal direction and 85.71% in the vertical direction in 2 mm) were proven to be the most accurate landmarks, while the predictions in the chin region were relatively inaccurate. Furthermore, the predictions in the vertical direction were of higher accuracy compared to the horizontal direction except for the points around the chin. CONCLUSIONS: The Dolphin® software demonstrated acceptable prediction accuracy in midfacial changes in class III patients. However, there were still limitations for changes in the chin and lower lip prominence. CLINICAL RELEVANCE: Clarifying the accuracy of Dolphin® software in predicting soft tissue changes of orthodontic class III cases will facilitate physician-patient communication and clinical treatment.

Facial Analysis for Gender Affirmation/Gender-Related Facial Analysis.

There are anthropometric differences between the bony and integumentary facial features of male and female individuals. When compared to males, female faces in general are more heart-shaped, with a shorter and smoother forehead, a smaller more defined nose, and a tapered chin.

Clinical Anatomy of the Chin Evaluated by 3-Dimensional Tomography and Cadaveric Dissection: Implications for Safety and Optimal Injection Techniques in Chinese.

BACKGROUND: Soft tissue fillers have been widely used for the correction of chin volume loss because of congenital conditions and aging. OBJECTIVE: This study aimed to discuss anatomical concerns for chin filler injections, which may help to reduce the incidence of severe intravascular embolization complications and improve patient satisfaction. METHODS AND MATERIALS: We scanned 40 cadaveric heads with a contrast agent using a 64-row spiral computed tomography scanner. The scan was visualized by a Philips IntelliSpace workstation and analyzed by Materialise's interactive m image control system software to measure and quantify the arterial data. Twenty of 40 cadavers were dissected to define the layers of tissue. RESULTS: In total, 221 arteries passed through the sagittal plane of 40 specimens. The number of superficial arteries (163 of 221) was much greater than the number of deep arteries (58 of 221). The number of arteries gradually decreased with distance from the lower lip vermilion border plane, which formed the lower third of the face. CONCLUSION: This study introduces a safe and effective technique for administering chin filler injections that minimizes risks and improves patient satisfaction.

Genioplasty in Contemporary Orthognathic Surgery.

In contemporary orthognathic surgery planning, the genium/chin constitutes an important part that contributes to the maxillofacial profile. The aesthetics of the lower face is affected by the position of the genium which makes reestablishment of genial morphology an essential component. It is hence necessary to evaluate the genium objectively on its individual merit, and any discrepancy is addressed accordingly. This review presents an overview of contemporary genioplasty techniques, their applications, and considerations on stability, osteosynthesis, complications, and the future developments.

Assessment of soft-tissue vs hard-tissue changes after isolated functional genioplasty / Évaluation des modifications des tissus mous par rapport aux tissus durs après une génioplastie fonctionnelle isolée

Introduction: This study aimed to determine the vertical and horizontal soft-tissue vs hard-tissue changes after isolated functional genioplasty and to revisit hard-tissue remodeling at the symphysis. Methods: Seventy-five patients who underwent genioplasty as an isolated procedure at the end of their orthodontic treatment were divided into three groups on the basis of their age at surgery: < 15 years (group 1), 15-18 years (group 2) and ≥ 19 years (group 3). Patients were evaluated at three time points: immediately before surgery (T1), immediately after surgery (T2) and two years after surgery (T3). In addition, 25 patients who did not accept genioplasty, were age-matched with group 1, and had a follow-up radiograph two years after the end of their orthodontic treatment were used as a control group. Results: From T2 to T3, group 1 showed less forward horizontal hard-tissue and soft-tissue changes at pogonion (Pg) than the control group; however, no difference was noted for vertical changes at Me & Me'. From T1 to T3, the horizontal hard-tissue and soft-tissue changes at Pg were 6.39 mm and 6.72 mm, respectively, for surgical groups. Vertical hard-tissue change at menton (Me) showed a reduction of 1.63 mm (95% confidence interval [CI], -3.37 to 0.11) and 3.89 mm (95% CI, -5.83 to -1.95) in nongrowing female and male patients, respectively. The vertical soft-tissue change reduction was similar for nongrowing male and female patients (1.7 mm [95% CI, -2.96 to -0.45]). Soft-tissue thickness change at Pg (0.33 mm) was not significant. In contrast, a small but significant increase in soft-tissue thickness was noted at Me (0.54 mm). Linear regressions were calculated for all groups and allowed for predicting long-term soft-tissue changes (T3-T1) using the amount of surgical displacement (T2-T1). Conclusions: The horizontal hard-tissue change was stable for nongrowing patients, and the horizontal soft-tissue change was 92% of hard-tissue. Vertical soft-tissue change is less predictable. Variation of soft-tissue thickness after genioplasty can be explained by skeletal changes and the achievement of an unforced labial occlusion. These results support the functional and esthetic benefits of this surgery. Comparison with the control group showed that genioplasty does not change the growth pattern, and bone remodeling is likely to explain the difference noted at Pg.

Introduction: Cette étude avait pour but de déterminer les modifications verticales et horizontales des tissus cutanés par rapport aux tissus osseux après une génioplastie fonctionnelle isolée et d'évaluer le remodelage des tissus osseux au niveau de la symphyse. Méthodes: Soixante-quinze patients qui ont subi une génioplastie comme procédure isolée à la fin de leur traitement orthodontique ont été divisés en trois groupes sur la base de leur âge au moment de la chirurgie : moins de 15 ans (groupe 1), de 15 à 18 ans (groupe 2) et de 19 ans et plus (groupe 3). Les patients ont été évalués à trois moments : immédiatement avant la chirurgie (T1), immédiatement après la chirurgie (T2) et deux ans après la chirurgie (T3). En outre, 25 patients qui n'ont pas accepté la génioplastie, dont l'âge correspondait à celui du groupe 1 et qui ont subi une téléradiographie de profil de contrôle deux ans après la fin de leur traitement orthodontique ont été utilisés comme groupe témoin. Résultats: De T2 à T3, le groupe 1 a montré moins de changements horizontaux des tissus durs et mous vers l'avant au niveau du pogonion (Pg) que le groupe témoin ; cependant, aucune différence n'a été notée pour les changements verticaux au niveau de Me & Me'. De T1 à T3, les changements horizontaux des tissus osseux et cutanés à Pg étaient respectivement de 6,39 mm et 6,72 mm pour les groupes chirurgicaux. La modification verticale des tissus osseux au niveau du menton (Me) a montré une réduction de 1,63 mm (IC 95 %, -3,37 à 0,11) et de 3,89 mm (IC95 %, -5,83 à -1,95) chez les patients féminins et masculins sans croissance, respectivement. La réduction verticale de la modification des tissus mous était similaire chez les patients homme et femme qui ne sont pas en croissance (1,7 mm [IC 95 %, -2,96 à -0,45]). La modification de l'épaisseur des tissus mous à Pg (0,33 mm) n'était pas significative. En revanche, une augmentation faible mais significative de l'épaisseur des tissus cutanés a été observée à Me (0,54 mm). Des régressions linéaires ont été calculées pour tous les groupes et permettent de prédire les changements à long terme des tissus cutanés (T3-T1) en utilisant la quantité de déplacement chirurgical (T2-T1). Conclusions: Le changement horizontal des tissus osseux est stable pour les patients qui ne grandissent pas et le changement horizontal des tissus mous représente 92 % des tissus durs. Le changement vertical des tissus cutanés est moins prévisible. La variation de l'épaisseur des tissus cutanés après une génioplastie peut s'expliquer par les changements squelettiques et l'obtention d'une occlusion labiale non forcée. Ces résultats confirment les avantages fonctionnels et esthétiques de cette chirurgie. La comparaison avec le groupe témoin a montré que la génioplastie ne modifie pas le schéma de croissance et le remodelage osseux est susceptible d'expliquer la différence constatée à Pg.

Correlation between vertical dimension of occlusion and different facial measurements among a sample of sudanese adults / Correlación entre la dimensión vertical de la oclusión y diferentes medidas faciales en una muestra de adultos sudaneses

Aim: This study aimed to evaluate the correlation between vertical dimension of occlusion (VDO) and various facial measurements in a sample of Sudanese adults. Material and Methods: A total of 113 dental students (33 males and 80 females) with a mean age of 21.7±1.26 years were enrolled in this study. Different facial measurements including (Eye-Mouth, Eye-Eye, Eye-Ear, and Ear Height) were compared with two different measurements of VDO: N-Gn (from the tip of the nose to the tip of the chin), and Sn-Me (from the base of the nose to the bottom of the chin). Pearson's correlation coefficient test was utilized for the correlation between the measured parameters. A p-value of less than 0.05 was considered significant for all analyses. Results: A significant positive correlation was shown between all measured facial distances and both measured VDO distances. Though, the strongest correlation was seen for the eye-mouth distance (r= 0.725, p<0.001), while the weakest was for ear height (r= 0.254, p= 0.007). A paired t-test revealed a significant longer N-Gn distance than Sn-Me distance. Also, it has been shown that there were no significant differences between right and left sides of the face. Conclusion: The distance measured from the outer canthus of the eye to the angle of the mouth can be used to predict Subnasale-Menton (Sn-Me) distance.

Objetivo: Este estudio tuvo como objetivo evaluar la correlación entre dimensión vertical oclusal (DVO) y varias medidas faciales en una muestra de adultos sudaneses. Material y Métodos: Un total de 113 estudiantes de odontología (33 hombres y 80 mujeres) con una edad media de 21,7 ± 1,26 años se inscribieron en este estudio. Se compararon diferentes medidas faciales que incluyen (ojo- boca, ojo-ojo, ojo-oído y altura de la oreja) con dos medidas diferentes de DVO: N-Gn (desde la punta de la nariz hasta la punta del mentón) y Sn -Yo (desde la base de la nariz hasta la parte inferior del mentón). Se utilizó la prueba del coeficiente de correlación de Pearson para la correlación entre los parámetros medidos. Un valor de p inferior a 0,05 se consideró significativo para todos los análisis. Resultados: Se mostró una correlación positiva significativa entre todas las distancias faciales medidas y ambas distancias DVO medidas. Sin embargo, la correlación más fuerte se observó para la distancia ojo-boca (r=0,725, p<0,001), mientras que la más débil fue para la altura de las orejas (r=0,254, p=0,007). Una prueba de t pareada reveló una distancia N-Gn significativamente más larga que la distancia subnasal-mentón. Además, se ha demostrado que no hubo diferencias significativas entre los lados derecho e izquierdo de la cara. Conclusión: La distancia medida desde el canto externo del ojo hasta el ángulo de la boca puede utilizarse para predecir la distancia subnasal-mentón.

Symphysis morphology and mandibular alveolar bone thickness in patients with ß-thalassemia major and different growth patterns.

OBJECTIVE: The present study aimed to assess the morphology of symphysis and alveolar bone thickness (ABT) surrounding mandibular incisors in thalassemic patients, as compared to unaffected individuals. METHODS: This case-control study was conducted on lateral cephalograms of 60 thalassemic and 60 unaffected patients with Class II malocclusion seeking orthodontic treatment at Dental School, Shiraz University of Medical Sciences. The sample was divided into three subgroups including hyperdivergent, normodivergent, and hypodivergent, according to the Jarabak index. Symphysis dimensions and alveolar bone thickness surrounding mandibular incisors were measured using AutoCad software. Finally, the correlation between alveolar bone thickness and symphysis morphology was assessed. RESULTS: In general, chin dimensions and bone thickness at different levels of mandibular incisor roots (cervical, middle, apical) were smaller in thalassemic adolescents than controls. Concerning the total sample as well as the normodivergent subgroup, significantly lower values were observed in thalassemic patients for symphysis width, total ABT at the cervical, and lingual ABT at the apical root area compared to controls (p < 0.05). The hypodivergent growth pattern was not associated with any statistical differences between the groups (p> 0.05). In both thalassemic and control subjects, symphysis width showed a weak to moderate positive correlation with ABT of lower incisors (p< 0.05), whereas symphysis height showed a moderate positive correlation with cervical ABT in only ß-thalassemia patients (p< 0.05). CONCLUSIONS: Compared to controls, ß-thalassemia patients showed thinner alveolar bone at different levels of lower incisor roots and smaller symphysis dimensions. There were significant correlations between symphysis dimensions and alveolar bone thickness of mandibular incisors in the sample.

Assessment of soft-tissue vs hard-tissue changes after isolated functional genioplasty.

INTRODUCTION: This study aimed to determine the vertical and horizontal soft-tissue vs hard-tissue changes after isolated functional genioplasty and to revisit hard-tissue remodeling at the symphysis. METHODS: Seventy-five patients who underwent genioplasty as an isolated procedure at the end of their orthodontic treatment were divided into 3 groups on the basis of their age at surgery: <15 years (group 1), 15-18 years (group 2), and ≥19 years (group 3). Patients were evaluated at 3 time points: immediately before surgery (T1), immediately after surgery (T2), and 2 years after surgery (T3). In addition, 25 patients who did not accept genioplasty, were age-matched with group 1, and had a follow-up radiograph 2 years after the end of their orthodontic treatment were used as a control group. RESULTS: From T2 to T3, group 1 showed less forward horizontal hard-tissue and soft-tissue changes at pogonion (Pg) than the control group; however, no difference was noted for vertical changes at Me & Me'. From T1 to T3, the horizontal hard-tissue and soft-tissue changes at Pg were 6.39 mm and 6.72 mm, respectively, for surgical groups. Vertical hard-tissue change at menton (Me) showed a reduction of 1.63 mm (95% confidence interval [CI], -3.37 to 0.11) and 3.89 mm (95% CI, -5.83 to -1.95) in nongrowing female and male patients, respectively. The vertical soft-tissue change reduction was similar for nongrowing male and female patients (1.7 mm [95% CI, -2.96 to -0.45]). Soft-tissue thickness change at Pg (0.33 mm) was not significant. In contrast, a small but significant increase in soft-tissue thickness was noted at Me (0.54 mm). Linear regressions were calculated for all groups and allowed for predicting long-term soft-tissue changes (T3-T1) using the amount of surgical displacement (T2-T1). CONCLUSIONS: The horizontal hard-tissue change was stable for nongrowing patients, and the horizontal soft-tissue change was 92% of hard-tissue. Vertical soft-tissue change is less predictable. Variation of soft-tissue thickness after genioplasty can be explained by skeletal changes and the achievement of an unforced labial occlusion. These results support the functional and esthetic benefits of this surgery. Comparison with the control group showed that genioplasty does not change the growth pattern, and bone remodeling is likely to explain the difference noted at Pg.

Changes in the neck tissue layers during pinch manipulation: Implications for lipolytic deoxycholate injections for double chin.

BACKGROUND: The skin of the neck is often pinched during minimally invasive esthetic procedures for the double chin using a lipolytic agent in order to facilitate injecting into the subcutaneous fat layer rather than under the platysma muscle. However, how the neck tissue layers move during the pinch manipulation is not well understood. AIMS: To determine which layer of the neck is lifted during pinching and to evaluate the usefulness of the pinch manipulation during injection therapy. METHODS: The pinched submentum of a living person was scanned using MRI, and ultrasonography was also performed in the same area in both resting and pressed states. At four sites on a fresh cadaver, the skin of the neck was pinched and the elevated neck skin was excised. The exposed areas were grossly examined. RESULTS: MRI scanning revealed that the pinch manipulation extended the subcutaneous fat layer and moved the platysma muscle to a deeper location. Ultrasonography revealed that the thickness of each layer of the neck was reduced when pressing the neck. In the cadaver examination, pinching resulted in part of the subcutaneous fat lifting, and this was removed when the lifted skin was cut, leaving the platysma muscle intact. CONCLUSIONS: When performing an esthetic procedure that involves injecting a lipolytic agent into the submental area, the pinch manipulation is a very useful technique for ensuring a safe procedure that avoids injecting into the deep layer under the platysma muscle.

Prediction accuracy of Dolphin software for soft-tissue profile in Class I patients undergoing fixed orthodontic treatment.

BACKGROUND: Simulation and prediction can facilitate the decision between an extraction versus nonextraction treatment plan. This study aimed to assess the accuracy of Dolphin Imaging software in predicting profile changes in class I borderline cases. METHODS: In this retrospective study, class I borderline patients (i.e., both extraction and nonextraction treatment plans were possible for them) aged 15-35 years were enrolled. All of the cephalometric analyses were done by Dolphin Imaging software, version 11.8 Premium. The initial cephalograms were superimposed on initial photographs. The final values for the 7 angular and linear landmarks of the upper and lower incisors were extracted from post-treatment cephalograms and inserted in the "Goals" tab of the Dolphin Imaging software. Post-treatment images of patients were simulated. Final post-treatment photographs were superimposed on the simulated pictures. The differences between the real and simulated pictures were calculated in relation to the reference lines. The P value was set at 0.05. RESULTS: A total of 70 patients (36 with tooth extraction, and 34 without tooth extraction) were included. In the extraction group, the horizontal position of both lips was predicted to be significantly more protruded than it actually was, whereas in the nonextraction group, the only difference between the simulated and actual results was that the vertical position of the lower lip, which was simulated as being more inferior than it actually was. CONCLUSIONS: Despite the statistically significant differences between the real and simulated pictures, the differences were small and clinically insignificant. Prediction via Dolphin Imaging software can be an appropriate guide in extraction-nonextraction borderline cases.

Long-term hard and soft tissue response following isolated genioplasty: a systematic review.

PURPOSE: Genioplasty facilitates alteration of the chin position and contour which contributes to aesthetics and function. The response of the hard and soft tissues following genioplasty has not been assessed after a year or more of the surgery being performed. Hence, the aim of this systematic review was to assess the response of the hard and soft tissues occurring at least 1 year after the procedure. MATERIAL AND METHODS: A literature search was conducted in the following electronic databases: PubMed, Ovid, LILACS, and Cochrane Library. Potential articles were identified wherein only studies with genioplasty performed as an isolated procedure and with data at least 12 months after the procedure were included. RESULTS: Five studies were included in this systematic review. Two of the articles included were considered to be of good quality while three were considered to be of moderate quality using a modified Downs and Black tool. The ROBINS-I tool showed a moderate risk of bias for most domains. The study characteristics revealed varying degrees of relapse for the hard and soft tissues. CONCLUSIONS: In the anteroposterior plane, the soft tissue relapsed more than the hard tissues 3 years post genioplasty. However, relapse in the vertical plane showed a wide variation for both the hard and soft tissues. In the anteroposterior plane, the hard tissue to soft tissue response 2 years or more following genioplasty ranged from 1:0.77 to 1:0.91 while in the vertical plane the hard tissue to soft tissue response ranged from 1:0.67 to 1:1.16.

Changes in the airway after mentoplasty (genioplasty): systematic review / Cambios en la vía aérea después de una mentoplastia (genioplastia): una revisión sistemática

SUMMARY: The aim of this research was to evaluate the changes obtained with the mentoplasty technique in the increase of the airway imaging. A systemic review was performed using the parameters of the prism matrix, in the PubMed, Science Direct, Redalyc database, covering the years 1984 to 2019 with the use of defined inclusion criteria. The authors independently applied the selected parameter of data extraction, study selection and risk-to-bias assessment. A total of 1,251 articles were obtained among the 3 databases, of which 10 met the inclusion criteria. The variables studied were: type of research, sample size, sex, age, dento-skeletal diagnosis, airway classification, diagnosis of obstructive sleep apnea syndrome (OSAS), type of imaging evaluation, variables evaluated in the image, pre and post-operative values, surgical technique and type of fixation used, other surgical procedures applied, and complications. In the cases of linear evaluation with cephalometric analysis (9 articles) they used PAS (posterior airspace), MP-H (mandibular plane to the hyoid) and SNB (saddle-nasion-point B), and SCSA (section area as the most relevant points, smallest cross section) and VT (total volume) in the volumetric evaluations (2 articles). The average change in posterior airspace achieved by the cited authors is 4.2 mm with standard deviation of 1.4 mm with the use of advancement mentoplasty. The most widely used technique was mentoplasty with a horizontal osteotomy by 5 authors. Based on the research there is a positive relationship between the increase in the airway and the advancement mentoplasty procedure, however, more standardized studies associated with the way of measuring and evaluating the relationship between advancement and the airway are necessary.

RESUMEN: El objetivo de esta investigación fue evaluar los cambios obtenidos con la técnica de mentoplastia en el incremento de la via aérea. Una revisión sistemática fue realizada utilizando parámetros de la matriz prisma, en PubMed, Science Direct, Redalyc database, cubriendo los años 1984 a 2019 con criterios de inclusión definidos. Los autores aplicaron de forma independiente los parámetros de selección y extracción de datos, selección de estudios y riesgos de sesgo. Un total de 1251 artículos fueron obtenidos de las 3 bases de dato, donde 10 artículos cumplieron los criterios de inclusión. Las variables estudiadas fueron: tipo de investigación, tamaño de la muestra, genero, edad, diagnóstico dento esqueletal, clasificación de la vía aérea, diagnostico de síndrome de apnea del sueño (SAOS), tipo de evaluación de la imagen, variables evaluadas en la imagen en pre y postoperatorio, técnica quirúrgica y tipo de fijación utilizada, otros procedimientos quirúrgicos y complicaciones. En el caso de la evaluación linear con cefalometria (9 artículos), usaron PAS (posterior airspace), MP-H (plano mandibular hacia el hueso hioide) y SNB (silla turca-nasion- punto B) y SCSA (sección de puntos mas relevantes, menores transfversales) y el VT (volumen total) en las evaluaciones volumétricas (2 artículos). El promedio de cambio posterior de la vía aérea citado por autores fue de 4,2 mm con una desviación estándar de 1,4 mm con el uso de la mentoplastia de avance. La técnica mas habitual fue la mentoplastia con osteotomía horizontal (5 autores). Basados en esta investigación existe una relación positiva entre el incremento de la vía aérea y el avance con genioplastia; sin embargo, mas estudios estandarizados junto con medidas definidas y la evaluación correcta del avance y la vía área son necesarios.

The Influence of the Mandibular Chin Angle on the Occurrence of Mandibular Condylar Fracture: A Retrospective Study.

BACKGROUND: Condylar fractures are commonly associated with symphysis/parasymphysis fractures. Condylar fractures have been attributed to direct and indirect traumatic forces, the direction and magnitude of the forces, and the condylar anatomy. The chief aim of this study was to determine the association between the newly defined mandibular chin angle and the occurrence of condylar fractures. MATERIALS AND METHODS: A retrospective study was conducted to analyze two-dimensional computed tomography (2D CT) scans of patients with a history of chin trauma. The outcome was a symphysis/parasymphysis fracture with or without fracture of the mandibular condyle. The Mediff InstaRISPACS web-based platform was used to measure the chin angle. The cerebral aqueduct of Sylvius in the corresponding 2D CT midsagittal image was the standard reference plane to measure the chin angle. The SPSS Version 20 (IBM Corp, Armonk, NY) was used for data analysis. RESULTS: The sample size included 120 2D CT scans of patients with symphysis/parasymphysis fractures (60 associated with condylar fractures and 60 without condylar fractures). The mean chin angle in the group without condylar fracture was 133.35 ± 3.87°, which was approximately 15° lesser than in the condylar fracture group (mean, 148.56 ± 5.49°), and these findings were statistically significant (P < 0.05). CONCLUSION: Individuals with a high chin angle are potentially at a higher risk of sustaining associated condylar fractures.

Factors associated with the morphology of the mandibular symphysis and soft tissue chin.

OBJECTIVES: This study aimed to (I) assess the morphology of the symphysis and soft tissue chin associated with sex, age and sagittal/vertical skeletal patterns, and (II) identify the individual and combined contributions of these variables to different portions of the symphysis. METHODS: This cross-sectional study included 195 lateral cephalometric radiographs from untreated adults. Alveolar, basal, and soft tissue of the symphysis were measured by an X/Y cranial base coordinate system, and divided in accordance to four predictor variables: sex, age, and sagittal/vertical skeletal patterns. Parametric tests were conducted for comparison and correlation purposes, while multiple regression analysis was performed to explore combined interactions. RESULTS: Alveolar inclination is related to sagittal and vertical patterns, and both explained 71.4% of the variations. Alveolar thickness is weakly predicted and poorly influenced by age. Symphysis height was 10% higher in males, and associated with a vertical skeletal pattern and sex, and both explained 43.6% of variations. Basal symphyseal shows an individual thickness, is larger in males, and vertically short-positioned with age. Soft tissue chin is not necessarily related to the size of the underling skeletal pattern, and enlarges with age, even in adulthood. CONCLUSIONS: The symphysis and surrounding tissues are influenced by sex, age, and sagittal and vertical patterns, acting differently on the alveolar, basal and soft tissue portions. Sagittal and vertical skeletal patterns are the strongest association on alveolar symphysis inclination, whereas sex and age acts on the vertical symphysis position and soft tissues thickness.

Osseous Genioplasty: Prevention of Witch's Chin Deformity with No-Degloving Technique.

BACKGROUND: Osseous genioplasty is a powerful procedure that can correct chin dysmorphology; however, traditional techniques may result in chin ptosis or a "witch's chin" deformity. Iatrogenic chin ptosis is thought to be caused by excessive degloving of soft tissue with a failure to reattach the mentalis muscle. In the authors' study, they compared the "no-degloving" technique (using a 90-degree plate with lag-screw fixation) to the "traditional" technique, for minimization of chin ptosis. METHODS: The authors compared genioplasty techniques for consecutive patients: group 1 (traditional) underwent degloving for fixation of a stair-step plate, whereas group 2 (no-degloving) underwent lag-screw fixation (n = 50; 25 patients per group). The authors compared operating room time, advancement, complications, preoperative-to-postoperative vertical height change of the pogonion and menton (obtained through cone beam computed tomographic scans), surgeons' assessment of witch's chin, and FACE-Q surveys. RESULTS: No-degloving versus traditional groups had similar age and sex distributions, horizontal/vertical change (5 mm/2 mm versus 6 mm/2 mm), length of surgery, and complication rate (5 percent). The traditional group had more deviation from expected position for both the pogonion (3.4 mm versus 1.2 mm; p ≤ 0.05) and menton (2.9 mm versus 0.8 mm; p ≤ 0.05), and more occurrences of witch's chin (six versus zero). No-degloving was superior for several FACE-Q scales, including Chin Appearance, Quality of Life, Satisfaction with Decision to Undergo Procedure, and Satisfaction with Outcome. CONCLUSION: No-degloving osseous genioplasty is a safe, reproducible technique that results in decreased soft-tissue ptosis and increased patient satisfaction. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.

Morfología cefalométrica de la sínfisis del mentón en individuos jóvenes de la ciudad de Quito-Ecuador / Cephalometric morphology of chin symphysis in young individuals from the city of Quito-Ecuador

Resumen Introducción: La sínfisis del mentón aporta equilibrio, simetría y armonía al rostro. Por ser una estructura anatómica mandibular muy importante y altamente modificable en cirugía estética, se considera indispensable conocer su morfología y así obtener una correcta interacción en el diagnóstico, pronóstico y terapéutica médico-odontológica. Objetivo: Determinar la morfología sínfisis del mentón en jóvenes adultos de la ciudad de Quito- Ecuador, año 2019, mediante la identificación de las longitudes sagitales y coronales. Metodología: Este estudio tuvo un enfoque cuantitativo, tipo descriptivo-observacional, con temporalidad retrospectiva. Se calibraron, analizaron y trazaron 384 radiografías digitales laterales de adultos jóvenes de la ciudad de Quito-Ecuador, año 2019 en el software AutoCAD-2019. Resultados: Existió una elevada frecuencia de la forma geométrica cuadrada (60%) con respecto a la rectangular (40%), adicionalmente se identificó que la figura cuadrada es más frecuente en individuos de sexo femenino y sujetos clase I (56%) y II (70%), además de todos los patrones de crecimiento vertical hipodivergentes (58%), normodivergentes (64%) e hiperdivergentes (57%). Conclusiones: La forma cuadrada de la sínfisis del mentón es mayor que la forma rectangular. Por la originalidad de los resultados, se sugiere realizar nuevos estudios que correlacionen la morfología mentoniana con las diferentes estructuras cráneo-maxilofaciales.

Abstract Introduction: The chin symphysis contributes to the balance, symmetry and harmony of the face. Since it is an important anatomical jaw structure and highly modifiable in aesthetic surgery, it is considered crucial to know its morphology and, thus, obtain a correct interaction in the diagnosis, prognosis and medical-dental therapy. Objective: To determine the symphysis morphology of the chin in young adults in the city of Quito, Ecuador, in the year 2019, through the identification of sagittal and coronal lengths. Methodology: This study had a quantitative approach, descriptive-observational type, with retrospective temporality. We calibrated, analyzed and plotted 384 lateral digital radiographs of young adults from the city of Quito-Ecuador, year 2019 in the software AutoCAD-2019. Results: There was a high frequency of the square geometric shape (60%) in comparison to the rectangular one (40%). Additionally, it was identified that the square figure is more frequent in female individuals and class I (56%) and II (70%) subjects, in addition to all the hypodivergent (58%), normodivergent (64%) and hyperdivergent (57%) vertical growth patterns. Conclusions: The square shape of the chin symphysis is larger than the rectangular shape. Due to the originality of the results, it is suggested to carry out new studies that correlate chin morphology with the different cranio-maxillofacial structures.

Attractiveness assessment by orthodontists and laypeople judging female profile modifications of Class II Division 1 malocclusion.

INTRODUCTION: The objective of this study was to evaluate the differences in preference between orthodontists and laypeople, judging soft tissue digital alterations of a Class II Division 1 profile of a female patient with mandibular retrognathia, produced by simulated camouflage and mandibular advancement therapy. METHODS: The profile image of a White woman with a Class II Division 1 mandibular retrognathic profile was digitally modified to produce 7 pictures: 1 baseline, 3 stepwise increase in the nasolabial angle of 113°, 121°, and 129°, and 3 stepwise increase in chin-neck length of 51 mm, 54 mm, and 57 mm. Forty-four orthodontists and 162 laypeople assessed these 7 images. RESULTS: The untreated baseline profile was found to be least attractive for both orthodontists and laypeople, with orthodontists scoring significantly lower than laypeople. The profiles representing mandibular advancement therapy were judged significantly better by both groups than camouflage therapy. Orthodontists preferred straighter profiles than laypeople, giving the highest-ranking to a chin-neck length of 57 mm, whereas laypeople gave the highest rank to a chin-neck length of 54 mm. CONCLUSIONS: Orthodontists prefer straighter profiles and gave a lower ranking to the untreated Class II Division 1 female profile compared with laypeople. Orthodontists and laypeople favor mandibular advancement therapy over camouflage therapy. However, both groups seem to prefer the effect of both treatment modalities over the untreated baseline Class II Division 1 profile.