Validity of the Maturation Stage Method in the Individual Assessment of Midpalatal Suture Ossification Before Maxillary Expansion: A Systematic Review / Validez del Método de la Etapa de Maduración en la Evaluación Individual de la Osificación de la Sutura Palatina Mediana Previo a la Expansión Maxilar: Una Revisión Sistemática

In 2013, midpalatal suture maturation stage assessment was proposed for the evaluation of patients before performing maxillary expansion. In this study, we aimed to analyze the association between the midpalatal suture maturation stages assessed by CBCT, according to the method described by Angelieri et al., and other objective methods used to assess skeletal maturation or bone fusion. A computerized database search was conducted using PubMed, Cochrane Library, SciELO, LILACS, Web of Science, and Scopus, without language restriction. Unpublished literature was searched on ClinicalTrials.gov, the National Research Register, and Pro-Quest Dissertation Abstracts and Thesis database. Authors were contacted when necessary, and reference lists of the included studies were screened. Search terms included midpalatal suture, maturation, correlation, diagnostic performance, classification, evaluation, assessment, and relationship. Quality assessment was performed using the Observational Cohort and Cross-Sectional Studies tool developed by the National Heart, Lung, and Blood Institute. Eleven studies met the inclusion criteria. Of all the studies included, 81.9% had fair qualit y and 18.1% good quality, respectively. Eight out of eleven studies assessed the correlation between the midpalatal suture maturation method and the skeletal maturity evaluated by CVM method (Spearman's correlation coefficient: 0.244-0.908). Two out of eleven studies evaluated the correlation between midpalatal suture maturation method and the skeletal maturity assessed by HWM method (Spearman's correlation coefficient: 0.904-0.905) Even though midpalatal suture maturation stage assessment needs an exhaustive training and calibration process, it is a valid method to evaluate skeletal maturation or bone fusion. From a clinical perspective, for patients at CS4, CS5 and CS6, an assessment of the midpalatal suture on CBCT is indicated. A similar assessment should be done in patients at SMI 7-9.

En 2013, se propuso un nuevo método para la evaluación del estadio de maduración de la sutura palatina mediana para la evaluación de los pacientes antes de realizar la expansión maxilar. En este estudio, nuestro objetivo fue analizar la asociación entre las etapas de maduración de la sutura palatina mediana evaluada en CBCT, según el método descrito por Angelieri et al., y otros métodos objetivos utilizados para evaluar la maduración esquelética o la fusión ósea. Se realizó una búsqueda en las bases de datos PubMed, Cochrane Library, SciELO, LILACS, Web of Science y Scopus, sin restricción de idioma. Se buscó literatura no publicada en ClinicalTrials.gov, el Registro Nacional de Investigación y la base de datos Pro-Quest Dissertation Abstracts and Thesis. Se estableció contacto con los autores cuando fue necesario y se revisaron las listas de referencias de los estudios incluidos. Los términos de búsqueda incluyeron sutura palatina mediana, maduración, correlación, rendimiento diagnóstico, clasificación, evaluación, valoración y relación. La evaluación de la calidad se realizó mediante la herramienta de Estudios transversales y de cohortes observacionales desarrollada por el Instituto Nacional del Corazón, los Pulmones y la Sangre. Once estudios cumplieron con los criterios de inclusión. Del total de estudios incluidos, el 81.9% tuvo calidad regular y el 18.1% calidad buena, respectivamente. Ocho de once estudios evaluaron la correlación entre el método de maduración de la sutura palatina mediana y la madurez esquelética evaluada por el método CVM (coeficiente de correlación de Spearman: 0.244-0.908). Dos de once estudios evaluaron la correlación entre el método de maduración de la sutura palatina mediana y la madurez esquelética evaluada por el método HWM (coeficiente de correlación de Spearman: 0.904-0.905). Aunque la evaluación del estado de maduración de la sutura palatina mediana necesita un proceso exhaustivo de entrenamiento y calibración, es un método válido para evaluar la maduración esquelética o la fusión ósea. Desde una perspectiva clínica, para pacientes en CS4, CS5 y CS6, está indicada una evaluación de la sutura palatina mediana en CBCT. Se debe realizar una evaluación similar en pacientes con SMI 7-9.

Morfometría de la rama mandibular para la estimación del sexo y edad en una población adulta peruana 2014-2019 / Morphometry of the mandibular ramus for the estimation of sex and age in a peruvian adult population 2014-2019

Objetivo: Evaluar la precisión de la estimación del sexo y edad utilizando la morfometría de la rama mandibular mediante un modelo de regresión lineal múltiple incluyendo el ancho intercondilear, el ancho bigonial, la longitud coronoides, la longitud de la rama mandibular, la longitud del cóndilo, el ancho máximo de la rama mandibular y el ángulo goniaco en una población adulta peruana 2014-2019. Material y métodos: Se utilizaron 174 tomografías computarizadas de 18 a 60 años de edad y se analizaron las variables ancho intercondileo (AI), ancho bigonial (AB), longitud coronoides (LCr), longitud del cóndilo (LC), longitud de la rama mandibular (LRm), ancho máximo de la rama mandibular (AMRm) y ángulo goniaco (AG) del lado derecho de la mandíbula. Resultados: La prueba t de muestras independientes determinó que la mayor diferencia entre el sexo fue en la variable LC con 6.9225 mm, la función discriminante obtuvo una tasa de clasificación correcta del sexo con 82.7% y con el modelo de regresión logística múltiple se obtuvo una sensibilidad en el sexo femenino de 81.2%, una especificidad de 85.7%, el sexo masculino una sensibilidad de 85.7%, una especificidad de 81.2%, en la edad la correlación más alta fue en AG con -0.252. Conclusión: Los coeficientes más potentes fueron en LRm, AI y AB con 0.608, 0.606 y 0.604 respectivamente. La mayor diferencia se encontró en el ancho intercondilar con 9.3 mm entre los sexos, en general el porcentaje de precisión predictiva fue de 83.9% en una población egipcia muy parecido a este estudio. (AU)

Objective: To evaluate the precision of the estimation of sex and age using the morphometry of the mandibular ramus through a multiple linear regression model including the intercondylar width, the bigonial width, the coronoid length, the length of the mandibular ramus, the length of the condyle, the maximum width of the mandibular ramus and the gonial angle in a Peruvian adult population 2014-2019. Material and methods: 174 computed tomography scans from 18 to 60 years of age were used and the variables intercondylar width (AI), bigonial width (AB), coronoid length (CLr), condyle length (LC), ramus length mandibular ramus (MRm), maximum width of the mandibular ramus (MRAm) and gonial angle (AG) of the right side of the mandible. Results: The independent samples t-test determined that the greatest difference between the sexes was in the LC variable with 6.9225 mm, the discriminant function obtained a correct classification rate of the sex with 82.7% and with the multiple logistic regression model a sensitivity in the female sex of 81.2%, a specificity of 85.7%, the male sex a sensitivity of 85.7%, a specificity of 81.2%, in age the highest correlation was in AG with -0.252. Discussion: The most powerful coefficients were in LRm, AI and AB with 0.608, 0.606 and 0.604 respectively. The greatest difference was found in the intercondylar width with 9.3 mm between the sexes, in general the percentage of predictive accuracy was 83.9% in an Egyptian population very similar to this study. (AU)

Longitudinal Skeletal Growth Analysis of Mandibular Asymmetry in Unoperated Patients With Unilateral Craniofacial Microsomia (UCFM).

PURPOSE: To examine the growth rate discrepancy of the affected and unaffected ramus heights in Pruzansky Type I and Type II mandibles. METHODS: This is a serial retrospective longitudinal growth study of 30 untreated patients (21 males and 9 females) with UCMF (age range from 5 years to 14 years). The mean age of patients was 8.5 years, and the mean follow-up records were 3.7 years. There were 13 patients in group I with a Pruzansky Type I mandible and 17 patients in group II with a Pruzansky Type II. The unaffected side of the mandible served as a control. Eighteen cephalometric parameters were examined at each of the two-time intervals. RESULTS: In patients with Pruzansky Type I mandible, the affected ramus grew on average 1.41 mm per year; the unaffected ramus grew 1.66 mm per year during the same period. In patients with Pruzansky Type II mandible, the affected ramus grew on average 0.84 mm per year; during the same period, unaffected ramus grew 1.79 per year. When the growth rate of the ramus height on the affected side was compared to the unaffected side, there was no statistically significant difference in Pruzansky Type I mandibles (p > .05); however, there was a statistically significant difference in the Pruzansky Type II mandibles (p < .05). CONCLUSION: The growth rate discrepancy of the affected and unaffected ramus heights was more severe in Pruzansky Type II mandibles than Pruzansky Type I mandibles explaining the progressive nature of facial asymmetry in Pruzansky II mandibles.

Genes and Pathways Associated with Skeletal Sagittal Malocclusions: A Systematic Review.

Skeletal class II and III malocclusions are craniofacial disorders that negatively impact people's quality of life worldwide. Unfortunately, the growth patterns of skeletal malocclusions and their clinical correction prognoses are difficult to predict largely due to lack of knowledge of their precise etiology. Inspired by the strong inheritance pattern of a specific type of skeletal malocclusion, previous genome-wide association studies (GWAS) were reanalyzed, resulting in the identification of 19 skeletal class II malocclusion-associated and 53 skeletal class III malocclusion-associated genes. Functional enrichment of these genes created a signal pathway atlas in which most of the genes were associated with bone and cartilage growth and development, as expected, while some were characterized by functions related to skeletal muscle maturation and construction. Interestingly, several genes and enriched pathways are involved in both skeletal class II and III malocclusions, indicating the key regulatory effects of these genes and pathways in craniofacial development. There is no doubt that further investigation is necessary to validate these recognized genes' and pathways' specific function(s) related to maxillary and mandibular development. In summary, this systematic review provides initial insight on developing novel gene-based treatment strategies for skeletal malocclusions and paves the path for precision medicine where dental care providers can make an accurate prediction of the craniofacial growth of an individual patient based on his/her genetic profile.

Insights into the palaeobiology of an early Homo infant: multidisciplinary investigation of the GAR IVE hemi-mandible, Melka Kunture, Ethiopia.

Childhood is an ontogenetic stage unique to the modern human life history pattern. It enables the still dependent infants to achieve an extended rapid brain growth, slow somatic maturation, while benefitting from provisioning, transitional feeding, and protection from other group members. This tipping point in the evolution of human ontogeny likely emerged from early Homo. The GAR IVE hemi-mandible (1.8 Ma, Melka Kunture, Ethiopia) represents one of the rarely preserved early Homo infants (~ 3 years at death), recovered in a richly documented Oldowan archaeological context. Yet, based on the sole external inspection of its teeth, GAR IVE was diagnosed with a rare genetic disease-amelogenesis imperfecta (AI)-altering enamel. Since it may have impacted the child's survival, this diagnosis deserves deeper examination. Here, we reassess and refute this diagnosis and all associated interpretations, using an unprecedented multidisciplinary approach combining an in-depth analysis of GAR IVE (synchrotron imaging) and associated fauna. Some of the traits previously considered as diagnostic of AI can be better explained by normal growth or taphonomy, which calls for caution when diagnosing pathologies on fossils. We compare GAR IVE's dental development to other fossil hominins, and discuss the implications for the emergence of childhood in early Homo.

A three-dimensional statistical shape model of the growing mandible.

Mandibular growth and morphology are important topics in the field of oral and maxillofacial surgery. For diagnostic and planning purposes, a normative database or statistical shape model of the growing mandible can be of great benefit. A collection of 874 cadaveric children's mandibles with dental age between 1 and 12 years old were digitized using computed tomography scanning and reconstructed to three-dimensional models. Point correspondence was achieved using iterative closest point and coherent point drift algorithms. Principal component analysis (PCA) was applied to find the main modes of variation in the data set. The average mandible was presented, along with the first ten PCA modes. The first mode explained 78% of the total variance; combining the first ten modes accumulated to 95% of the total variance. The first mode was strongly correlated with age and hence, with natural growth. This is the largest study on three-dimensional mandibular shape and development conducted thus far. The main limitation is that the samples lack information such as gender and cause of death. Clinical application of the model first requires validation with contemporary samples.

Age estimation of immature human skeletal remains from mandibular and cranial bone dimensions in the postnatal period.

Age estimation is one of the crucial first steps in the identification of human skeletal remains in both forensic and archeological contexts. In the postnatal period, age is traditionally estimated from dental development or skeletal growth, typically long bone diaphyseal length. However, in many occasions other methods are required. This study provides alternative means of estimating age of juvenile remains from the size of several cranial bones and the mandible. A sample of 185 identified juvenile skeletons between birth and 13 years of age from two European collections were used (Lisbon and Spitalfields). Measurements of the frontal, occipital-lateralis, occipital-basilaris, occipital-squamous, zygomatic, maxilla, and mandible were used to calculate classical calibration regression formulae for the sexes combined. The sample was divided into three age groups birth-2 years, 2-6 years, and 2-12.9 years, depending on bone and its growth trajectory. For all the bones, measurements of the youngest age groups yielded the most precise age estimates. The vault bones on average yielded the best performing models, with the frontal bone having the most precise of all. The mandible performed on par with the best performing cranial bones, particularly in individuals under the age of 2 years. This study provides one of the most comprehensive approaches to juvenile age estimation based on bones of the skull, providing a resource that potentially can help estimate age of juvenile skeletons from a variety of circumstances.

Relación morfológica entre el hueso hioides y la mandíbula en una muestra de esqueletos estudiados / Morphological relationship between the hyoid bone and the mandible in a sample of skeletons studied

Introducción: El crecimiento de los tejidos esqueléticos constituye una respuesta secundaria, compensatoria y mecánicamente obligada a cambiar las matrices funcionales. Cuando por alguna razón las matrices funcionales se ven afectadas en su crecimiento, los tejidos esqueléticos responden también con un grado de afectación dependiendo del momento en que esta se produzca. Entonces la mandíbula como parte del viscerocráneo debe presentar esa relación con el hueso hioides de forma directa. Objetivos: Asociar el comportamiento morfológico del hueso hioides con variables morfológicas de la mandíbula y verificar sí la morfología de los huesos pertenecientes a los esqueletos estudiados está determinada por el conjunto de tejidos blandos que los rodea y marcan el ritmo del proceso de remodelación de crecimiento. Material y Métodos: Se realizó la continuación del estudio osteológico en una muestra ósea de 82 esqueletos con mediciones morfométricas del hueso hioides y la mandíbula. Para evaluar la relación de la morfología del hueso hioides con respecto a la mandíbula, se utilizaron matrices de coeficiente de correlación lineal de Pearson en SPSS versión 22 de Window. Resultados: Se corrobora la relación de la morfología del hueso hioides con el crecimiento del viscerocráneo, debido a la correlación positiva y significativa entre varias variables morfológicas del hioides que se obtuvo, -tanto a nivel de su cuerpo como sus astas o cuernos mayores-, con la mandíbula. Conclusiones: Existe una asociación de la morfología del hueso hioides con respecto a la morfología de la mandíbula(AU)

Introduction: The growth of skeletal tissues constitutes a secondary, compensatory and mechanically obliged response to change the functional matrixes. When the growth of functional matrixes is affected for any reason, the skeletal tissues also respond with a degree of affectation depending on the moment in which it occurs. Then the mandible, as part of the viscerocranium, must present that relationship with the hyoid bone directly. Objective: To associate the morphological behavior of the hyoid bone with the morphological variables of the mandible and verify if the morphology of the bones belonging to the skeletons studied is determined by the set of soft tissues that surround them and set the pace of the growth remodeling process. Material and Methods: The continuation of the osteological study was carried out in a bone sample of 82 skulls by performing morphometric measurements of the hyoid bone and the mandible. Pearson's linear correlation coefficient matrices in SPSS Version 22 were used to evaluate the relationship between the morphology of the hyoid bone and the bones of the mandible. Results: The relationship between the morphology of the hyoid bone and the growth of the viscerocranium is corroborated by the positive and significant correlation between several morphological variables of the hyoid bone obtained - both at the level of its body and its greater horns -, and the mandible. Conclusions: These findings corroborate the association between the morphology of the hyoid bone and the growth of the mandible(AU)

Comparison of the third molar maturity index (I3M) between left and right lower third molars to assess the age of majority: a multi-ethnic study sample.

The diagnostic accuracy of the I3M to assess the legal age of 18 years has already been tested in several specific-population samples. The left lower third molar has been extensively used for discriminating between minors and adults. This research aimed to compare the usefulness of lower third molar maturity indexes, from both left and right side (I3ML and I3MR), in samples originating from four distinct continents in order to examine possible differences in their accuracy values. For this purpose, a sample of 10,181 orthopantomograms (OPGs), from Europe, Africa, Asia and America, was analysed and previously scored in other studies. The samples included healthy subjects with no systemic disorders with both third molars and clear depicted root apices. Wilcoxon Signed Rank test for left and right asymmetry did not show any significant differences. Data about sensitivity, specificity, predictive values, likelihood ratio and accuracy were pooled together and showed similar results for I3ML and I3MR, respectively. In addition, all these quantities were high when only the I3MR was considered to discriminate between adults and minors. The present referable database was the first to pool third molar measurements using panoramic radiographs of subjects coming from different continents. The results highlighted that both I3ML and I3MR are reliable indicators for assessing the legal age of 18 years old in those jurisdictions where this legal threshold has been set as the age of majority.

Objectifying growth of vascularized bone transfers after mandibular reconstruction in the pediatric population.

BACKGROUND: Autologous vascularized bone transfer is the preferred strategy for the reconstruction of mandibular defects in a pediatric population. The principal argument is the theoretical postoperative growth potential of the neomandible, which uses vascularized donor tissues. OBJECTIVES: The purpose of this study was to objectify the veritable growth potential of vascularized bone transfers in children. METHODS: A literature search was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, revealing 57 patients younger than or equal to 18 years who had undergone a mandibular reconstruction with a vascularized free flap. Only studies using postoperative imaging were included. Outcomes regarding growth and postoperative corrections and complications were analyzed. RESULTS: Neomandibular growth was observed in 63.2% of all included patients. The proportion of growth was higher in patients with condylar preservation (95.7%) than that of patients with condylar involvement (41.2%). Reconstruction of the condyle by a free flap, which includes an epiphyseal growth plate or cartilage increased postoperative growth potential (77.8%) but did not reduce the need for later orthognathic surgery. CONCLUSION: After mandibular reconstruction with a vascularized bone transfer, the majority of pediatric patients shows neomandibular growth. Condylar preservation, the inclusion of epiphyseal growth plates or cartilage, and the patients age at the time of reconstruction are essential defining parameters.

The Effect of Polybutylcyanoacrylate Nanoparticles as a Protos Delivery Vehicle on Dental Bone Formation.

BACKGROUND: Dental implants are commonly used for missing teeth, for which success depends heavily on the quality of the alveolar bone. The creation of an ideal implant site is a key component in shortening the treatment time, which remains clinically challenging. Strontium ranelate (Protos) is an anti-osteoporotic agent which has previously been used to promote bone formation, however the systemic use of Protos has been linked to serious cardiovascular and venous thromboembolic events, thus local delivery strategies may be better suited for this purpose. In this study, a biodegradable, and biocompatible nanocarrier "polybutylcyanoacrylate" (PBCA) loaded with strontium was constructed and its ability to promote bone formation was assessed. METHODOLOGY: PBCA nanoparticles loaded with strontium (PBCA-Sr NPs) were synthesized using the emulsion polymerization method, and their physical properties (zeta potential, size and shape) and entrapment efficiency were characterized. Committed MSCs (osteoblasts) were derived from the differentiation of cultured rat mesenchymal stem cells (MSC), which were tested with the PBCA-Sr NPs for cytotoxicity, inflammatory response, bone formation and mineralization. Scanning electron microscopy was performed following a 7-day treatment of PBCA-Sr NPs on decellularized procaine mandibular bone blocks grafted with osteoblasts. RESULTS: Spherical PBCA-Sr NPs of 166.7 ± 2.3 nm, zeta potential of -1.15 ± 0.28 mV with a strontium loading efficiency of 90.04 ± 3.27% were constructed. The presence of strontium was confirmed by energy-dispersive X-ray spectroscopy. Rat committed MSCs incubated in PBCA-Sr NPs for 24 hrs showed viabilities in excess of 90% for concentrations of up to 250 ug/mL, the cellular expression of osteocalcin and alkaline phosphatase were 1.4 and 1.3 times higher than the untreated control, and significantly higher than those treated with strontium alone. Bone formation was evident following osteoblast engraftment on the decellularized procaine mandibular bone block with PBCA-Sr NPs, which appeared superior to those treated with strontium alone. CONCLUSION: Treatment of committed MSCs with PBCA-Sr NPs showed higher expression of markers of bone formation when compared with strontium alone and which corresponded to greater degree of bone formation observed on the 3-dimensinal decellularized procaine mandibular bone block. Further quantitative analysis on the extent of new bone formation is warranted.

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).

A 3D analysis of growth trajectory and integration during early human prenatal facial growth.

Significant shape changes in the human facial skeleton occur in the early prenatal period, and understanding this process is critical for studying a myriad of congenital facial anomalies. However, quantifying and visualizing human fetal facial growth has been challenging. Here, we applied quantitative geometric morphometrics (GM) to high-resolution magnetic resonance images of human embryo and fetuses, to comprehensively analyze facial growth. We utilized non-linear growth estimation and GM methods to assess integrated epigenetic growth between masticatory muscles and associated bones. Our results show that the growth trajectory of the human face in the early prenatal period follows a curved line with three flexion points. Significant antero-posterior development occurs early, resulting in a shift from a mandibular prognathic to relatively orthognathic appearance, followed by expansion in the lateral direction. Furthermore, during this time, the development of the zygoma and the mandibular ramus is closely integrated with the masseter muscle.

Bmi1 regulate tooth and mandible development by inhibiting p16 signal pathway.

To determine whether the deletion of p16 can correct tooth and mandible growth retardation caused by Bmi1 deficiency, we compared the tooth and mandible phenotypes of homozygous p16-deficient (p16-/- ) mice, homozygous Bmi1-deficient (Bmi1-/- ) mice, double homozygous Bmi1 and p16-deficient (Bmi1-/- p16-/- ) mice to those of their wild-type littermates at 4 weeks of age by radiograph, histochemistry and immunohistochemistry. Results showed that compared to Bmi1-/- mice, the dental mineral density, dental volume and dentin sialoprotein immunopositive areas were increased, whereas the ratio of the predentin area to total dentin area and that of biglycan immunopositive area to dentin area were decreased in Bmi1-/- p16-/- mice. These results indicate that the deletion of p16 can improve tooth development in Bmi1 knockout mice. Compared to Bmi1-/- mice, the mandible mineral density, cortical thickness, alveolar bone volume, osteoblast number and activity, alkaline phosphatase positive area were all increased significantly in Bmi1-/- p16-/- mice. These results indicate that the deletion of p16 can improve mandible growth in Bmi1 knockout mice. Furthermore, the protein expression levels of cyclin D, CDK4 and p53 were increased significantly in p16-/- mice compared with those from wild-type mice; the protein expression levels of cyclin D and CDK4 were decreased significantly, whereas those of p27 and p53 were increased significantly in Bmi1-/- mice; these parameters were partly rescued in Bmi1-/- p16-/- mice compared with those from Bmi1-/- mice. Therefore, our results indicate that Bmi1 plays roles in regulating tooth and mandible development by inhibiting p16 signal pathway which initiated entry into cell cycle.

The Dual Effects of Reactive Oxygen Species on the Mandibular Alveolar Bone Formation in SOD1 Knockout Mice: Promotion or Inhibition.

The status of reactive oxygen species (ROS) correlates closely with the normal development of the oral and maxillofacial tissues. Oxidative stress caused by ROS accumulation not only affects the development of enamel and dentin but also causes pathological changes in periodontal tissues (periodontal ligament and alveolar bone) that surround the root of the tooth. Although previous studies have shown that ROS accumulation plays a pathologic role in some oral and maxillofacial tissues, the effects of ROS on alveolar bone development remain unclear. In this study, we focused on mandibular alveolar bone development of mice deficient in superoxide dismutase1 (SOD1). Analyses were performed using microcomputerized tomography (micro-CT), TRAP staining, immunohistochemical (IHC) staining, and enzyme-linked immunosorbent assay (ELISA). We found for the first time that slightly higher ROS in mandibular alveolar bone of SOD1(-/-) mice at early ages (2-4 months) caused a distinct enlargement in bone size and increased bone volume fraction (BV/TV), trabecular thickness (Tb.Th), and expression of alkaline phosphatase (ALP), Runt-related transcription factor 2 (Runx2), and osteopontin (OPN). With ROS accumulation to oxidative stress level, increased trabecular bone separation (Tb.Sp) and decreased expression of ALP, Runx2, and OPN were found in SOD1(-/-) mice at 6 months. Additionally, dosing with N-acetylcysteine (NAC) effectively mitigated bone loss and normalized expression of ALP, Runx2, and OPN. These results indicate that redox imbalance caused by SOD1 deficiency has dual effects (promotion or inhibition) on mandibular alveolar bone development, which is closely related to the concentration of ROS and the stage of growth. We present a valuable model here for investigating the effects of ROS on mandibular alveolar bone formation and highlight important roles of ROS in regulating tissue development and pathological states, illustrating the complexity of the redox signal.

Size changes in miR­21 knockout mice: Geometric morphometrics on teeth, alveolar bone and mandible.

MicroRNA­21 (miR­21) is a small non­coding RNA that is differentially expressed during tooth development, particularly during amelogenesis. Although orthodontic tooth movement and the innate immune response are impaired, miR­21 knockout mice demonstrate no obvious skeletal phenotype. However, the consequence of miR­21 knockout on tooth phenotype and corresponding alveolar bone is unknown. The current study utilized landmark­based geometric morphometrics to identify anatomical dissimilarities of the three lower and upper molars, and the corresponding alveolar bone, in miR­21 knockout and wild­type control mice. The anatomical structures were visualized by microcomputer tomography. A total of 36 and 38 landmarks were placed on mandibular and maxillary molars, respectively. For the alveolar bone, 16 landmarks were selected on both anatomical sites. General Procrustes analysis revealed significantly smaller molars and dimensions of the alveolar bone in the mandible of the miR­21 knockout mice when compared with wild­type controls (P=0.03 and P=0.04, respectively). The overall dimension of the mandible was reduced by the lack of miR­21 (P=0.02). In the maxilla, the dimension of the alveolar bone was significant (P=0.02); however, this was not observed in the molars (P=0.36). Based on principal component analysis, no changes in shape for any of the anatomical sites were observed. Dental and skeletal jaw length were calculated and no prognathism was identified. However, the fluctuating asymmetry of the molars in the mandible and the maxilla was reduced in the miR­21 knockout mice by 38 and 27%, respectively. Taken together, the results of the present study revealed that the molars in the mandible and the dimension of the respective alveolar bone were smaller in miR­21 mice compared with wild­type littermates, suggesting that miR­21 influences tooth development.

Expression of tartrate-resistant acid phosphatase and cathepsin K during osteoclast differentiation in developing mouse mandibles.

The present study was designed to test the hypothesis that osteoclasts appear after or at the same time as the initiation of bone mineralization in developing intramembranous bones. We examined mineral deposition via Von Kossa staining to determine when bone mineralization begins, tartrate-resistant acid phosphatase (TRAP) activity and cathepsin K immunoreactivity to identify the presence of osteoclasts, and their mRNA expression levels to assess osteoclastic differentiation in the embryonic mouse mandible. Cathepsin K-immunopositive cells were detected around the same time as the onset of bone mineralization, whereas TRAP-positive cells appeared prior to bone mineralization. Cathepsin K protein was expressed only in multinucleated osteoclasts, whereas TRAP activity was identified in both mono- and multinucleated cells. During bone development, TRAP-positive cells altered their morphology, which was related to the number of their nuclei. The elevated mRNA levels of TRAP and cathepsin K were consistent with the increased percentage of multinucleated osteoclasts and the progression of bone development. Our study revealed that TRAP-positive cells appear prior to bone mineralization, and TRAP- and cathepsin K-positive multinucleated osteoclasts appear at the same time as the initiation of bone mineralization in embryonic mouse mandibles, suggesting that osteoclasts contribute to bone matrix maturation during intramembranous ossification.

Comparison of different machine learning approaches to predict dental age using Demirjian's staging approach.

CONTEXT: Dental age, one of the indicators of biological age, is inferred by radiological methods. Two of the most commonly used methods are using Demirjian's radiographic stages of permanent teeth excluding the third molar (Demirjian's and Willems' method). The major drawbacks of these methods are that they are based on population-specific conversion tables and may tend to over- or underestimate dental age in other populations. Machine learning (ML) methods make it possible to create complex data schemas more simply while keeping the same annotation system. The objectives of this study are to compare (1) the capacity of ten machine learning algorithms to predict dental age in children using the seven left permanent mandibular teeth compared to reference methods and (2) the capacity of ten machine learning algorithms to predict dental age from childhood to young adulthood using the seven left permanent mandibular teeth and the four third molars. METHODS: Using a large radiological database of 3605 orthopantomograms (1734 females and 1871 males) of healthy French patients aged between 2 and 24 years, seven left permanent mandibular teeth and the 4 third molars were assessed using Demirjian's stages. Dental age estimation was then performed using Demirjian's reference method and various ML regression methods. Two analyses were performed: with the 7 left mandibular teeth without third molars for the under 16 age group and with the third molars for the entire study population. The different methods were compared using mean error, mean absolute error, root mean square error as metrics, and the Bland-Altman graph. RESULTS: All ML methods had a mean absolute error (MAE) under 0.811 years. With Demirjian's and Willems' methods, the MAE was 1.107 and 0.927 years, respectively. Except for the Bayesian ridge regression that gives poorer accuracy, there was no statistical difference between all ML tested. CONCLUSION: Compared to the two reference methods, all the ML methods based on the maturation stages defined by Demirjian were more accurate in estimating dental age. These results support the use of ML algorithms instead of using standard population tables.

Intermittent hypoxia inhibits mandibular cartilage growth with reduced TGF-ß and SOX9 expressions in neonatal rats.

Intermittent hypoxia (IH) has been associated with skeletal growth. However, the influence of IH on cartilage growth and metabolism is unknown. We compared the effects of IH on chondrocyte proliferation and maturation in the mandibular condyle fibrocartilage and tibial hyaline cartilage of 1-week-old male Sprague-Dawley rats. The rats were exposed to normoxic air (n = 9) or IH at 20 cycles/h (nadir, 4% O2; peak, 21% O2; 0% CO2) (n = 9) for 8 h each day. IH impeded body weight gain, but not tibial elongation. IH also increased cancellous bone mineral and volumetric bone mineral densities in the mandibular condylar head. The mandibular condylar became thinner, but the tibial cartilage did not. IH reduced maturative and increased hypertrophic chondrocytic layers of the middle and posterior mandibular cartilage. PCR showed that IH shifted proliferation and maturation in mandibular condyle fibrocartilage toward hypertrophic differentiation and ossification by downregulating TGF-ß and SOX9, and upregulating collagen X. These effects were absent in the tibial growth plate hyaline cartilage. Our results showed that neonatal rats exposed to IH displayed underdeveloped mandibular ramus/condyles, while suppression of chondrogenesis marker expression was detected in the growth-restricted condylar cartilage.

MicroRNAs regulate distal region of mandibular development through Hh signaling.

Mandibular anomalies are often seen in various congenital diseases, indicating that mandibular development is under strict molecular control. Therefore, it is crucial to understand the molecular mechanisms involved in mandibular development. MicroRNAs (miRNAs) are noncoding small single-stranded RNAs that play a critical role in regulating the level of gene expression. We found that the mesenchymal conditional deletion of miRNAs arising from a lack of Dicer (an essential molecule for miRNA processing, Dicerfl/fl ;Wnt1Cre), led to an abnormal groove formation at the distal end of developing mandibles. At E10.5, when the region forms, inhibitors of Hh signaling, Ptch1 and Hhip1 showed increased expression at the region in Dicer mutant mandibles, while Gli1 (a major mediator of Hh signaling) was significantly downregulated in mutant mandibles. These suggest that Hh signaling was downregulated at the distal end of Dicer mutant mandibles by increased inhibitors. To understand whether the abnormal groove formation inDicer mutant mandibles was caused by the downregulation of Hh signaling, mice with a mesenchymal deletion of Hh signaling activity arising from a lack of Smo (an essential molecule for Hh signaling activation, Smofl/fl ;Wnt1Cre) were examined. Smofl/fl ;Wnt1Cre mice showed a similar phenotype in the distal region of their mandibles to those in Dicerfl/fl ;Wnt1Cre mice. We also found that approximately 400 miRNAs were expressed in wild-type mandibular mesenchymes at E10.5, and six microRNAs were identified as miRNAs with binding potential against both Ptch1 and Hhip1. Their expressions at the distal end of the mandible were confirmed by in situ hybridization. This indicates that microRNAs regulate the distal part of mandibular formation at an early stage of development by involving Hh signaling activity through controlling its inhibitor expression level.