Injury Risk Estimation in Mandible-Related Surgical Procedures: A CBCT Study Based on Vital Interforaminal Anatomical Structures.

The mandibular interforaminal region has been considered safe for surgical procedures; nevertheless, the risk of injury to neurovascular structures, such as the mental foramen (MF) and its related structures (anterior loop [AL] and lingual foramina [LF]) should not be overlooked. The study aimed to evaluate the relative risk of injury to these structures during surgical procedures in the anterior region of the mandible based on cone-beam computed tomography (CBCT) scans. A retrospective cross-sectional and observational study was performed on 250 CBCTs from adults (18-69 years) with dentate jaws. Linear measurements of the MF, AL, and LF were evaluated to estimate the risk of injury to these structures during chin-related surgical procedures. The most frequent distance between the base of the mandible (BM) and MF was 8 mm (30.2%). In addition, 20.4% of the CTs had 6 mm from the vestibular cortical bone to the LF. The commonly found measurement from LF to the apex of the nearest tooth was 7 mm (24.0%); 64.2% of the CTs showed a 2-mm distance between the most distal point of the dental implant site to the most anterior point of the AL. Safety distances for genioplasty techniques (MF to mandible base > 6 mm, 96.6% [CI 95%, 95.0%-98.2%]) were observed. Considering the 5-mm cut-off point between the lower limit of a hypothetical bone graft and the chin, 65.4% (CI 95%, 58.9%-71.9%) of CTs were within this distance. Regarding the safety margin of 8 mm, 85.6% (CI 95%, 80.8%-90.4%) were up to this value. This study found safety margins for genioplasty and chin bone grafting surgical techniques that adopt a 5-mm cut-off point. Further similar studies assessing other surgical methods and employing larger samples from different geographical origins may contribute to this field of investigation.

Does Aesthetic Osseous Genioplasty Impact Upper Airway Volume?

BACKGROUND: Although maxillomandibular advancement is the treatment of choice for obstructive sleep apnea syndrome (OSAS) in the presence of underlying maxillomandibular complex hypoplasia, there is still a gap in the literature regarding the impact of genioplasty upon upper airway volume (UAV). OBJECTIVES: The aim of this study was to evaluate the impact of isolated osseous genioplasty upon UAV. METHODS: A retrospective analysis of all patients subjected to isolated osseous genioplasty between July 2015 and July 2022 was conducted. Cone-beam computed tomography was performed preoperatively and postoperatively to assess the chin and hyoid 3-dimensional (3D) spatial position and UAV changes after surgery. RESULTS: A total of 44 patients were included in the study. Regarding surgical movements of the chin, almost all patients received a sagittal movement (n = 42; 39 forward and 3 backward), while in 8 patients a vertical movement (5 upward and 3 downward) was applied, and in 6 patients the chin was centered. Statistically significant increases in total UAV (P = .014) and at the level of the oropharynx (P = .004) were observed. Specifically, chin centering, upward and forward movements enlarged the oropharynx volume (P = .006, .043 and .065, respectively). Chin advancement enlarged the hypopharynx volume (P = .032), as did upward movement of the hyoid bone (P < .001). CONCLUSIONS: Results of the study suggest that aesthetic osseous genioplasty impacts the UAV: each 3D spatial chin movement differently impacts the upper airway by enlarging or narrowing it. However, further studies addressing the apnea-hypopnea index are required to assess its effectiveness in treating OSAS.

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.

3-dimensional analysis of hard- and soft-tissue symmetry in a Chinese population.

BACKGROUND: Facial symmetry severely affects appearance and function. Large numbers of patients seek orthodontic treatment to improve facial symmetry. However, the correlation between hard- and soft-tissue symmetry is still unclear. Our aim was to investigate the hard- and soft-tissue symmetry in subjects with different levels of menton deviation and sagittal skeletal classes with 3D digital analysis and to investigate the relationship between the entire and individual hard- and soft-tissues. METHODS: A total of 270 adults (135 males and 135 females) consisting of 45 subjects of each sex in each sagittal skeletal classification group. All subjects were further classified into relative symmetry (RS), moderate asymmetry (MA) and severe asymmetry (SA) groups based on the degree of menton deviation from the mid-sagittal plane (MSP). The 3D images were segmented into anatomical structures and mirrored across the MSP after establishing a coordinate system. Original and mirrored images were registered by a best-fit algorithm, and the corresponding root mean square (RMS) values and colormap were obtained. The Mann‒Whitney U test and Spearman correlation were conducted for statistical analysis. RESULTS: The RMS increased with greater deviations with regard to the deviation of the menton in most of anatomical structures. Asymmetry was represented in the same way regardless of sagittal skeletal pattern. The soft-tissue asymmetry had a significant correlation with dentition in the RS group (0.409), while in the SA group, it was related to the ramus (0.526) and corpus (0.417) in males and was related to the ramus in the MA (0.332) and SA (0.359) groups in females. CONCLUSIONS: The mirroring method combining CBCT and 3dMD provides a new approach for symmetry analysis. Asymmetry might not be influenced by sagittal skeletal patterns. Soft-tissue asymmetry might be reduced by improving the dentition in individuals with RS group, while among those with MA or SA, whose menton deviation was larger than 2 mm, orthognathic treatment should be considered.

The association between dental and facial symmetry in adolescents.

INTRODUCTION: Facial aesthetics have become one of the most important objectives of orthodontic treatment. The correction of dental arches should be performed in accordance with the face. This study explored the association between occlusal and facial asymmetries in adolescents, particularly emphasizing a Class II subdivision. METHODS: Eighty-one adolescents (43 males, 38 females) with a median age of 15.9 (interquartile range, 15.17-16.33) years were enrolled. Of these patients, 30 had a Class II subdivision (right side, n = 12; left side, n = 18). Three-dimensional facial scans were analyzed using surface- and landmark-based methods. Chin asymmetry was determined using the chin volume asymmetry score. Three-dimensional intraoral scans were analyzed to assess occlusal asymmetry. RESULTS: The surface matching scores were 59.0% ± 11.3% for the whole face and 39.0% ± 19.2% for the chin. Chin volume was larger on the right side than on the left side in most patients (n = 51, 63%), and it was associated with a dental midline shift to the corresponding subdivision side. A correlation between dental and facial asymmetries was noted. In addition, the dental midline shifted to the left in patients with a Class II subdivision, regardless of the side, and to the right in those with a symmetrical Class II subdivision. However, several patients did not possess asymmetrical occlusal traits sufficient for statistical analysis. CONCLUSIONS: Dental asymmetry was weak but significantly correlated with facial asymmetry.

The influence of mandibular divergence on facial soft tissue thickness in class I patients: a cephalometric study.

BACKGROUND: The aims of this study were to evaluate the association between mandibular divergence and facial soft tissue thickness (FSTT) measured at different profile levels, and the gender difference in FSTT. MATERIALS AND METHODS: Lateral cephalograms were used to examine nine linear distances: the glabella area (G-G1), nasal (N-N1) and subnasal area (A-Sn), upper (Sd-Ls) and lower lip thickness (Id-Li), mentolabial sulcus (B-Sm), chin area (Pg-Pg1), gnathion area (Gn-Gn1) and menton area (Me-Me1) in 155 adult Caucasian subjects (79 males, 76 females) from the central Balkan area. Subjects were divided into three groups according to the ANB angle, Wit's appraisal and SN/GoGn angle into normodivergent (28 male, 27 female subjects), hypodivergent (26 males, 25 females) and hyperdivergent (25 males, 24 females). RESULTS: Progressive decreasing in the soft tissue thickness from hypo- towards hyperdivergent group was established in N-N1, A-Sn, Gn-Gn1, Me-Me1. There are significant differences in Gn-Gn1 and Me-Me1 (p < 0.02). Progressive increasing of FSTT happens only at the level of mentolabial sulcus and these differences are significant. Significant gender differences were established for the following distances: N-N1 in hyperdivergent, A-Sn in all three examined groups, the upper lip thickness in normo- and hyperdivergent, the lower lip thickness in hypodivergent, the thickness of mentolabial sulcus in hypo- and normodivergent, Pg-Pg1 in hyperdivergent and Me-Me1 in normodivergent subjects (p < 0.05). CONCLUSIONS: Facial soft tissue thickness showed a various degree of dependence on vertical developmental pattern at different levels of measurement. The areas whose thickness is significantly conditioned by this pattern were established: the chin area at level Gn-Gn1, Me-Me1 and the region of the mentolabial sulcus (B-Sm). At most levels, male subjects have thicker soft tissues and these differences are significant for all three groups in the subnasal area.

Tomographic evaluation of the mandibular nerve in the mental region and its surgical implications: a cross-sectional study.

The aim of this study was to evaluate the prevalence and length of the anterior loop (AL) of the inferior alveolar nerve, nerve emergence from the mental foramen, and prevalence of sensory disorders after implant placement in the interforaminal region. Four hundred and fifty hemimandibles (225 patients) were evaluated using cone beam computed tomography and panoramic radiographs. Information on the presence of sensory disorders was obtained from the medical records. AL prevalence was 13.6% and mean AL length was 1.25 mm. The false-negative rate for the identification of the AL using panoramic radiography was 58.6%. Straight nerve emergence from the mental foramen was the most prevalent (62.7%), followed by anterior (21.8%) and posterior (15.6%) emergence. The incidence of sensory disorders was 4.4%, and 1.1% were related to the presence of the AL. When implants were placed within the planned distance of the mental foramen or further, 1.2% had sensory problems associated with the presence of the mandibular incisive canal. In cases of distances smaller than planned, 12.9% had sensory alterations. Only five (1.1%) had the AL, with a length between 0 and 4.5 mm. However, in four cases, the planned distance was respected and, even so, there was a sensory disorder. Posterior nerve emergence from the mental foramen was associated with a higher prevalence of AL.

The Effect of Weight-Loss Interventions on Cervical and Chin Subcutaneous Fat Depots; the CENTRAL Randomized Controlled Trial.

Accumulation of cervical and chin subcutaneous adipose tissues (SAT) represent known phenotypes of obesity. We aimed to evaluate the sensitivity of these fat storages to long-term weight-loss directed lifestyle-intervention and to assess their relations to bodily-adiposity, insulin-resistance, and cardiometabolic risk; We randomly assigned 278 participants with abdominal-obesity/dyslipidemia to low-fat or Mediterranean/low-carbohydrate diets +/- physical-activity. All participants underwent an 18 month whole-body magnetic resonance imaging follow-up, from which we assessed cervical and chin SAT-areas; Participants (age = 48 years; 90% men; body-mass-index = 30.9 kg/m2) had an 18-month adherence-rate of 86%. Cervical-SAT and chin-SAT decreased after 6-months (-13.1% and -5.3%, respectively, p < 0.001). After 18-months only cervical-SAT remained decreased compared to baseline (-5%, p < 0.001). Cervical and chin-SAT 18-month changes were associated with changes in weight (r = 0.70, r = 0.66 respectively; <0.001 for both) and visceral-adipose-tissue (VAT; r = 0.35, r = 0.42 respectively; <0.001 for both). After adjustment to VAT, waist-circumference, or weight-changes, chin-SAT 18-month reduction was associated with favorable changes in fasting-glucose (ß = 0.10; p = 0.05), HbA1c (ß = 0.12; p = 0.03), and homeostasis-model-assessment-of-insulin-resistance (ß = 0.12; p = 0.03). Cervical-SAT 18-month reduction was associated with decreased triglycerides (ß = 0.16; p = 0.02) and leptin (ß = 0.19; p = 0.01) independent of VAT; Cervical and chin-SATs are dynamic fat depots that correspond with weight-loss and are associated with changes in cardiometabolic profile. In long-term, chin-SAT displays a larger rebound compared with cervical-SAT. Chin-SAT accumulation is associated with in insulin-resistance, independent of central obesity. (ClinicalTrials identifier NCT01530724).

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.

Three-dimensional analysis of mandibular characteristics in patients with skeletal Class II malocclusion and chin deviation.

INTRODUCTION: This study aimed to analyze adults with mandibular characteristics of skeletal Class II malocclusion with chin deviation. METHODS: Seventy-five adult patients aged from 18 to 35 years were included and divided into 3 groups on the basis of sagittal skeletal pattern and chin deviation: skeletal Class I symmetry group, skeletal Class II symmetry group, and skeletal Class II asymmetry group (25 patients per group). Mandibular measurements on cone-beam computed tomography images were performed, and the differences between 2 sides in each group and the differences among the 3 groups were investigated. RESULTS: Compared with the contralateral side, the deviated side of patients in the Class II asymmetry group showed significantly smaller condyle angle to midsagittal plane, condylar height, ramal length, and length of the mandibular body, whereas it showed a significantly larger distance from condylion to the midsagittal plane, ramus angle to the horizontal plane, and distance from gonion to the midsagittal plane. Most linear measurements in the Class II symmetry group were significantly smaller than those in the Class I symmetry group. These linear measurements on the contralateral side of the Class II asymmetry group showed no significant difference with the Class I symmetry group, and these measurements on the deviated side of the Class II asymmetry group showed no significant difference with the Class II symmetry group. CONCLUSIONS: Length of the mandible, rotation of condyle, the inclination of the ramus, and position of gonion should be considered in subjects with skeletal Class II asymmetry when making diagnosis and treatment planning.

Submental Ultrasound Is Effective in Predicting Difficult Mask Ventilation but Not in Difficult Laryngoscopy.

The goal of this study was to determine the utility of submental ultrasound parameters in distinguishing difficult airway management from easy airway management. Forty-one adult patients who underwent elective surgery under general anesthesia with endotracheal intubation from March to December 2018 were included. We used submental ultrasound to measure tongue base thickness (TBT) in the midsagittal plane and the distance between lingual arteries (DLA) in the transverse dimension. The primary outcome was difficult laryngoscopy, and the secondary outcome was difficult mask ventilation. Receiver operating characteristic curve analysis and logistic regression revealed no correlation between difficult laryngoscopy and SMUS measurements. Nevertheless, patients with difficult mask ventilation had significantly higher TBT (p = 0.009) and longer DLA (p = 0.010). After adjustment of confounding factors, increased TBT (>69.6 mm) was the sole independent predictor of difficult mask ventilation. The results indicated that SMUS is effective in predicting difficult mask ventilation but not difficult laryngoscopy.

Three-dimensional virtual planning in mandibular advancement surgery: Soft tissue prediction based on deep learning.

The study aimed at developing a deep-learning (DL)-based algorithm to predict the virtual soft tissue profile after mandibular advancement surgery, and to compare its accuracy with the mass tensor model (MTM). Subjects who underwent mandibular advancement surgery were enrolled and divided into a training group and a test group. The DL model was trained using 3D photographs and CBCT data based on surgically achieved mandibular displacements (training group). Soft tissue simulations generated by DL and MTM based on the actual surgical jaw movements (test group) were compared with soft-tissue profiles on postoperative 3D photographs using distance mapping in terms of mean absolute error in the lower face, lower lip, and chin regions. 133 subjects were included - 119 in the training group and 14 in the test group. The mean absolute error for DL-based simulations of the lower face region was 1.0 ± 0.6 mm and was significantly lower (p = 0.02) compared with MTM-based simulations (1.5 ± 0.5 mm). CONCLUSION: The DL-based algorithm can predict 3D soft tissue profiles following mandibular advancement surgery. With a clinically acceptable mean absolute error. Therefore, it seems to be a relevant option for soft tissue prediction in orthognathic surgery. Therefore, it seems to be a relevant options.

A Reliable Method for Chin Augmentation by Mechanical Micronization of Lipoaspirates.

BACKGROUND: Desire for improved aesthetic contour of the lower third of the face has resulted in an increase in chin augmentation. Although many fillers, including hyaluronic acid (HA), autologous fat and stromal vascular fraction gel (SVF-gel), have been used to improve facial morphology, chin augmentation requires fillers that provide greater support. METHODS: The elastic and viscous moduli of SVF-gel and Coleman fat were assessed in vitro by rheological testing, whereas their elasticity were evaluated in vivo by ultrasonic elastography. Results in vitro were compared with those of highly elastic HA (HE-HA) and highly viscous HA (HV-HA), whereas results in vivo were compared with HE-HA. Changes in chin volume, SVF-gel retention rate and absorptivity for at least 12 months were measured by 3D white light scanning. Questionnaires were administered to assess patient satisfaction. RESULTS: The elastic and viscous modulus of SVF-gel was, respectively, slightly lower than HE-HA and HV-HA but higher than the other two in vitro, with the elasticity of the three layers of SVF-gel lower than HE-HA but slightly higher than normal control in vivo. The average retention rate was 62.34±3.34% at 12 months. The absorptivity of 90% of the samples was <3% from 6 to 12 months, which was considered stable. Patients expressed satisfaction with their results. CONCLUSION: SVF-gel has ideal rheologic characteristics in vitro, which has slightly higher elasticity than normal fat tissue of chin in vivo, and could keep well retention rate for chin augmentation in clinic. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Comparative Evaluation of Soft Tissue Chin Thickness in Adult Patients with Skeletal Class II Malocclusion with Various Vertical Growth Patterns: a Cephalometric Study.

INTRODUCTION: Facial soft tissue thickness is important not only for plastic surgeons but also for orthodontists to plan the treatment procedure. Genioplasty, an orthognathic surgery in combination with orthodontic treatment is indicated to restore adequate shape and projection of the chin in the face. It has been performed to enhance soft tissue contours related to disproportion between soft and hard tissue. These treatments require the critical information regarding the relation between soft and hard tissues for proper treatment plan-ning. However, there is very minimal documentation on comparison of soft tissue characteristics particularly in Class II malocclusion. AIM: To evaluate and compare soft tissue chin thickness in class II subjects with various growth patterns. To evaluate soft tissue chin thickness difference in males and females and compare the results with previous studies. MATERIALS AND METHODS: The study comprised 150 adults aged between 18 and 26 years (mean age 21 years). Based on FH/MP angle the study sample was allocated into three groups: group I - low (hypodivergent), group II - average, and group III - high (hyper-divergent). Radiographs were traced manually. Angular measurements were computed to determine the vertical position of the maxilla and mandible in relation to anterior cranial base, to true horizontal and to each other. Soft tissue chin thickness was measured at three different levels. RESULTS: Hyperdivergent group showed greater soft tissue chin thickness at Pog-Pog' than the hypodivergent and average angle groups. Hypodivergent group showed greater soft tissue chin thickness at Me-Me' and Gn-Gn' as compared to average and hyperdivergent groups. Males showed greater soft tissue chin thickness at hypodivergent, average and hyperdivergent group than females. CONCLUSIONS: Soft tissue thickness measurements were smaller in adult patients of hyperdivergent group compared to adult patients in clinically average and hypodivergent groups. All STC measurements were greater in men than in women. The findings suggested that STC thickness in hyperdivergent pattern should be considered differently at its most anterior point (Pog) relative to its inferior landmarks (Gn and Me).

One-Half Wedge Osteotomy Genioplasty for Correction of Chin Deviation Based on Three-Dimensional Computed Tomography Measurements and Simulation.

ABSTRACT: Conventional operations correcting chin deviations mainly rely on the observation and experience of the surgeons during the operation. We have created a new surgical method, one-half wedge osteotomy genioplasty (1/2WOG), that combines three-dimensional computed tomography measurements and simulation. This study evaluated the clinical effect of chin deviation correction with the 1/2WOG method. A total of 38 patients (15 men and 23 women) who underwent 1/2WOG between October 2019 and October 2014 were evaluated. The chin deviation angle and distance, and partial chin deformity were measured preoperatively using three-dimensional computed tomography data. Precise calculations and osteotomy lines were achieved by preoperative simulation. All patients underwent the same surgery by the same surgical team. The clinical effect of 1/2WOG was evaluated according to the preoperative and postoperative data and patient satisfaction. All 38 patients achieved satisfactory aesthetic results without major complications such as chin nerve injury or bone nonunion. Eight patients occured numbness of the lower lip after surgery; at 6-month follow-up, the numbness was reduced in 2 patients and disappeared in 6 patients. Compared with preoperative data, the chin deviation angle, chin deviation distance, and gonion-menton difference were significantly reduced postoperatively. During the 12-month follow-up, the patient satisfaction rate reached 90%. We conclude that chin deviation can be improved by 1/2WOG. The combination of digital technology measurements and simulation can increase the accuracy of the osteotomy line design, thus reducing surgical trauma and increasing patient satisfaction, which is worthy of clinical promotion.

Effectiveness of Chin Tuck on Laryngeal Penetration: Quantitative Assessment.

The effectiveness of the chin tuck maneuver is still controversial, despite being widely used in clinical practice. The chin tuck maneuver has been shown to be able to reduce or eliminate aspiration in a group of patients with a number of favorable conditions, but its effectiveness in preventing or managing penetration remains unclear. This study was designed to investigate whether the chin tuck maneuver is effective in reducing penetration. Images from a videofluoroscopic swallowing study (VFSS) taken from 76 patients with penetration were collected and reviewed retrospectively. The severity of penetration was assessed by the penetration ratio (ratio of the penetration depth to the length of the epiglottis) measured and calculated from the images in which the deepest penetration was observed. The penetration ratio was significantly decreased in the chin tuck posture compared with the ratio in the neutral position (p = 0.001). Significant reducing effect was observed in 26 (34.2%) out of 76 patients. When comparing other parameters of VFSS, residues in the vallecular and pyriformis sinuses were less severe in the effective group. Chin tuck significantly decreased residues in both effective and ineffective group. The results demonstrate that the chin tuck maneuver can reduce penetration, but its effectiveness is limited.

The goniomaxillar length/goniomandibular length ratio in normal newborn infants: A clinical tool for defining chin position abnormalities.

Retrognathia (recessed chin) and prognathism (prominent chin) often present as signs of an underlying condition. Accurate clinical definitions are important. Yet their definitions were according to "clinical impression", or to seldom used X-ray criteria. We propose a statistical and anthropometric definition of retrognathia and prognathism based upon the ratio between the goniomaxillar length (distance between the gonion at the mandible angle and the subnasale and the goniomandibular length (distance between the mandible angle and the most anterior point of the bony chin). We assumed that an increase in the ratio indicates retrognathia and a decrease reflects prognathism. We conducted a prospective, observational, anthropometric study in 204 consecutive healthy term infants. Measurements took place on the second day of life, using sliding calipers. Mean ± SD of goniomandibular length (5.1 ± 0.3 cm), goniomaxillar length (5.4 ± 0.3 cm), were calculated. All measurements correlated significantly with gestational age, and with infant birthweight. The mean ± SD goniomaxillar length/goniomandibular length ratio was 1.06 ± 0.05. We defined a normal ratio as being within 2 SD of the mean, that is, between 0.96 and and 1.16. This ratio correlated with neither gestational age nor with birthweight. We conclude that the goniomaxillar length/goniomandibular length ratio can be calculated whenever retro - or prognathism is suspected. A ratio outside of the 95% confidence interval should help in making this diagnosis. An increase in this ratio beyond 2 SD above the mean (1.16) could be interpreted as retrognathia and a decrease beyond 2 SD below the mean (0.96) as prognathism.

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

ABSTRACT 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.

RESUMO Introdução: O presente estudo objetivou: 1) avaliar a morfologia da sínfise mandibular e dos tecidos tegumentares do mento, associada ao sexo, idade, padrões sagital e vertical; e 2) identificar as contribuições dessas variáveis, individualmente ou combinadas, às diferentes regiões da sínfise. Métodos: Este estudo transversal incluiu 195 radiografias cefalométricas laterais de adultos não tratados ortodonticamente. Os tecidos alveolar, basal e mole da sínfise foram medidos por um sistema de coordenadas x, y e z da base do crânio e divididos de acordo com quatro variáveis preditoras: sexo, idade e padrões esqueléticos sagitais e verticais. Testes paramétricos foram conduzidos para fins de comparação e correlação, enquanto a análise de regressão múltipla foi realizada para explorar as interações combinadas. Resultados: A inclinação alveolar está relacionada aos padrões sagitais e verticais, e ambos explicaram 71,4% das variações. A espessura alveolar é fracamente prevista e pouco influenciada pela idade. A altura da sínfise foi 10% maior no sexo masculino e esteve associada ao padrão esquelético vertical e ao sexo, sendo que ambos explicaram 43,6% das variações. A sínfise basal mostra espessura individual, é maior no sexo masculino e verticalmente curta com a idade. O tecido mole do mento não está necessariamente relacionado ao tamanho do padrão esquelético subjacente e aumenta com a idade, mesmo na idade adulta. Conclusões: A sínfise e os tecidos circundantes são influenciados pelo sexo, idade e padrões sagitais e verticais, que atuam de forma diferenciada nas porções alveolar, basal e de tecidos tegumentares. Os padrões esqueléticos sagitais e verticais são a associação mais forte na inclinação da sínfise alveolar, enquanto o sexo e a idade atuam na posição vertical da sínfise e na espessura dos tecidos tegumentares.

Cone beam computed tomography imaging of sagittal positions of the mandibular prominence and maxillary central incisors in adult Chinese Han men as an aesthetic profile determinant.

BACKGROUND: To analyze the sagittal positions of the mandibular prominence and maxillary central incisors in adult Chinese Han men to establish their aesthetic profile characteristics. METHODS: Seventy-four Chinese Han men aged 18 to 40 years underwent cone beam computed tomography for detecting the distances between Glabella and Subnasale, Subnasale and Menthon of soft tissue, Condyle and Gonion, Pogonion and Pogonion's Anterior Limit Line, Facial Axis point of maxillary central incisor and the Goal Anterior Limit Line as well as the angle of the Occlusal Plane. Dolphin Imaging and Photoshop software packages were used to generate silhouette profiles. Thirteen orthodontists assessed the silhouette profiles and assigned visual analog scale scores. Scores >70 were assigned to the aesthetic (group 1), scores of 60to 70 to the general (group 2), scores of 50 to 60 to the acceptable (group 3), and scores of <50 to the unaesthetic profile (group 4). RESULTS: A total of 15 men were assigned to group 1, 35 to group 2, 14 to group 3, and 10 to group 4. There were no significant differences in the variables examined between groups 1, 2, and 3, but comparing group 1 with group 4, Pogonion and Pogonion's Anterior Limit Line (1.16 ±â€Š2.61 mm vs -1.44 ±â€Š2.92 mm, P = .046) and Facial Axis-Goal Anterior Limit Line (-0.61 ±â€Š2.54 mm vs 1.70 ±â€Š2.62 mm, P = .038) there were significant differences. CONCLUSION: Compared with the unaesthetic profile group, the sagittal positions of the maxillary central incisors were slightly posterior, and the chin was slightly anterior in adult Chinese Han men with an aesthetic profile.