Objectives: Age estimation is widely applied in the field of orthodontics, pediatric dentistry, and forensic science. Dental age estimation by the radiological method is frequently used because of its convenience and noninvasiveness. However, there are not enough suitable methods for eastern Chinese children. This study aimed to establish a modified formula for eastern Chinese children according to the Demirjian method and then compared the accuracy of the modified method with the Demirjian method and Willems method. Materials and methods: A total of 2367 dental panoramic radiographs from individuals aged 5–16 years of eastern China were collected as samples. Age estimation was conducted using the Demirjian and Willems methods. The polynomial curve fitting method was used to modify the Demirjian method to improve its application to the eastern Chinese children. The paired t test and accuracy ratio were used to compare the applicability of the modified methods with two commonly used methods. Results: The mean chronological age (CA) of the subjects was 11.20 ± 3.29 years for boys and 10.99 ± 3.12 years for girls. The mean difference values between the CA and dental age (DA) (CA–DA) using the Demirjian and Willems methods were 0.73 and 0.7 for boys, respectively, and both 0.79 for girls. The modified method using the polynomial curve fitting presented a smaller underestimation compared with CA for both boys (0.04 years) and girls (0.09 years), which showed a high suitability to Chinese children to some extent. Conclusions: The Willems method was more accurate in estimating DA compared with the Demirjian method. However, the modified method was more accurate than the two methods; therefore, it can be used in eastern Chinese children. Clinical relevance: It was thought to be a non-invasive, convenient, and efficient method to connect DA and CA. By estimating dental age, pediatrist, and orthodontists can better understand the development of permanent teeth and provide a more accurate orthodontic treatment time and treatment plan to children patients.

Background: The aim of this study was to investigate the association between chronological age and the PTR (pulp/tooth volume ratio) of specific teeth using CBCT enhanced with Materialise-Mimics Research software 21.0 in children and young adult population from Eastern China. Materials and methods: CBCT scans of 230 patients (119 males, 111 females), aged 8.18- 19.92 years were analyzed by two well-trained examiners in this retrospective study. The intraclass correlation coefficient (ICC) value was calculated to test the intra- and inter-examiner agreement. The volumetric analysis of the pulp and calcified tissues was performed on the maxillary left central incisors and canines. The correlation and regression analyses were then performed. Results: The Pearson correlation analysis showed a strong coefficient of correlation (r) for maxillary left canines (-0.81 for girls and -0.87 for boys) as compared to central incisors (-0.63 for girls and -0.70 for boys). Regarding performance, the canine model was more powerful than the central incisor model. The derived regression equation from maxillary left canines had high coefficients of determination (Age=21.979-105.42*ptr, R²=0.69). Conclusions: Our study proved that the PTR value of canines had a negative correlation relationship with a subadult’s chronological age and volumetric analysis of CBCT scans using the software may become an efficient method to estimate the chronological age of children and young adults. Background: The aim of this study was to investigate the association between chronological age and the PTR (pulp/tooth volume ratio) of specific teeth using CBCT enhanced with Materialise-Mimics Research software 21.0 in children and young adult population from Eastern China. Materials and methods: CBCT scans of 230 patients (119 males, 111 females), aged 8.18- 19.92 years were analyzed by two well-trained examiners in this retrospective study. The intraclass correlation coefficient (ICC) value was calculated to test the intra- and inter-examiner agreement. The volumetric analysis of the pulp and calcified tissues was performed on the maxillary left central incisors and canines. The correlation and regression analyses were then performed. Results: The Pearson correlation analysis showed a strong coefficient of correlation (r) for maxillary left canines (-0.81 for girls and -0.87 for boys) as compared to central incisors (-0.63 for girls and -0.70 for boys). Regarding performance, the canine model was more powerful than the central incisor model. The derived regression equation from maxillary left canines had high coefficients of determination (Age=21.979-105.42*ptr, R²=0.69). Conclusions: Our study proved that the PTR value of canines had a negative correlation relationship with a subadult’s chronological age and volumetric analysis of CBCT scans using the software may become an efficient method to estimate the chronological age of children and young adults.

Despite extensive research on maxillary impacted canines, studies specifically investigating maxillary impacted incisors remain limited. This retrospective study aimed to determine the prevalence of impacted teeth among adolescent orthodontic patients, analyze the imaging characteristics of maxillary impacted incisors, and evaluate factors influencing root development. From a cohort of 2163 underage patients who attended the children malocclusion special clinic between August 2022 and July 2024, individuals with impacted teeth were identified and their clinical data were collected. Subsequently, detailed analyses were conducted on impacted maxillary incisors using high-quality Cone-beam computed tomography (CBCT). There were 157 patients with 205 impacted teeth observed, presenting a prevalence rate of 7.26%. Maxillary canines were the most popular impacted teeth (39.51%), followed by maxillary incisors (30.24%). The tooth dilaceration demonstrated a significant relationship with the three-dimensional (3D) locations of tooth. Impacted teeth situated in low impacted depth (P < 0.05) and those with buccal-lingual (P < 0.05) or vertical (P < 0.01) orientations showed reduced susceptibility to root dilaceration. A positive correlation was observed between the Upper Incisor to Palatal Plane Angle (UI-PP) and both the probability (P < 0.05) and earlier occurrence (P < 0.01) of root dilaceration. The root length of impacted tooth was positively correlated with age (P < 0.05). Besides, the average root length of the impacted central incisors was 1.84 mm shorter than the contralateral. The prevalence of impacted teeth in our orthodontic specialist clinics was 7.26%, and 69.76% of impacted teeth were maxillary anteriors. The development of tooth roots was mainly influenced by age and 3D location. These findings enhance clinicians’ understanding of impacted maxillary incisor characteristics and factors affecting the root development. The UI-PP proves to be an effective 3D location evaluation indicator. Early intervention is recommended for impacted teeth lacking sufficient space for root development, which could facilitate root development and minimize the risk of root dilaceration.

Introduction: Melatonin, an endogenous neurohormone, modulates the biological circadian rhythms of vertebrates. It functions have been reported in previous stomatological studies as anti-inflammation, antioxidant, osseointegration of dental implants and stimulation to dental pulp stem cells differentiation, but its role in ameloblastic differentiation and mineralization has been rarely studied.Objective: To reveal the effects of melatonin on the mineralization of ameloblast lineage cells (ALCs), and to identify the change in gene expression and the potential mechanism based on ribonucleic acid sequencing (RNA-seq) analysis.Method: ALCs were induced in melatonin-conditioned medium. After 7-days culture, Western blot, real-time PCR, alkaline phosphatase (ALP) activity test, RNA-seq were accordingly used to detect the change in molecular level. After 1-month odontogenic induction in melatonin medium, Alizarin Red-S (ARS) staining showed the changes of mineral nodules. Differentially expressed genes (DEGs), enrichment of functions and signaling pathways analysis based on Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) database were performed. The JNK3 antagonist (JNK3 inhibitor IX, SR3576) and β-arrestin1 (Arrb1) overexpression were applied to confirm the fluctuation of melatonin-medicated JNK3 and Arrb1 expression.Results: In this study, we found out melatonin contributed to the ameloblastic mineralization, from which we can observed the elevated expression of enamel matrix protein, and increased ALP activity and mineralized nodules formation. RNA-seq analysis showed the up-regulation of neural JNK3 and down-regulation of Arrb1 in ALCs. Meanwhile, phosphorylated JNK3 deficiency (phosphorylated JNK3 inhibitor---SR3576 added to culture medium) led to mineralization delay, and Arrb1 overexpression proved Arrb1 takes bridge between melatonin receptors (MTNR) and JNK3 in MAPK signaling pathway.

The aim of this study is to assess the accuracy of Demirjian and Willems dental age estimation methods on a population of 8- to 15-year-old Taiwanese children. A total of 799 digital panoramic radiographs (404 boys, 395 girls) of children aged from 8.00 to 15.99 years are evaluated. All panoramic films are assessed by 2 examiners using Demirjian and Willems methods. We randomly select 48 panoramic films to evaluate the reproducibility of dental age measurements. The intraobserver and interobserver Cohen's kappa values are 0.733 and 0.762, respectively.The difference between chronological age and dental age is calculated for each individual using both methods. The result shows that Demirjian method slightly overestimates the chronological age of children. The mean age difference is 0.12 years for boys (standard deviation [SD], 0.80) and 0.21 years for girls (SD, 0.95). Willems method slightly underestimates the chronological age of children. The mean age difference is −0.22 years for boys (SD, 0.80) and −0.12 years for girls (SD, 0.92).In conclusion, Demirjian and Willems methods are both accurate for assessing dental age in the Taiwan region of China. The mean age differences of both methods are within ±1 year, which is acceptable at forensic odontology level. However, although the discrepancy between chronological age and dental age is frequently observed between −0.5 and 0.5 years in both methods, there is no guarantee it will be accurate for any particular individual, further modifications to both methods are suggested.

Background: The aim of this study is to assess the validity of whether the difference in dental age between 2009 to 2011 and 2021 is affected by environmental factors such as environmental pollution, floating population, and dietary habits. Demirjian and Willems dental age estimation methods were conducted for a Han population of children aged 8 to 14 in Shanghai, China. A total of 1,259 digital panorama radiographs of children aged 8.00-14.99 was estimated. All digital panorama radiographs were estimated using the Demirjian and Willems methods. Materials and methods: Both 2009 to 2011 and 2021 were statistically analyzed by paired t-tests. The results show that the Demirjian method overestimates 2009 to 2011 and underestimates 2021 than children's chronological age. According to the Willms method, males are overestimated and females are underestimated from 2009 to 2011, and both genders were underestimated in 2021. Conclusions: In conclusion, the difference in dental age between 2009 to 2011 and 2021 was statistically significant. Factors such as environment and dietary habits have been found to be affected by dental development. However, there are disputes among some researchers about the exact factors, so it is suggested to further study the effects of environmental factors on tooth development. Background: The aim of this study is to assess the validity of whether the difference in dental age between 2009 to 2011 and 2021 is affected by environmental factors such as environmental pollution, floating population, and dietary habits. Demirjian and Willems dental age estimation methods were conducted for a Han population of children aged 8 to 14 in Shanghai, China. A total of 1,259 digital panorama radiographs of children aged 8.00-14.99 was estimated. All digital panorama radiographs were estimated using the Demirjian and Willems methods. Materials and methods: Both 2009 to 2011 and 2021 were statistically analyzed by paired t-tests. The results show that the Demirjian method overestimates 2009 to 2011 and underestimates 2021 than children's chronological age. According to the Willms method, males are overestimated and females are underestimated from 2009 to 2011, and both genders were underestimated in 2021. Conclusions: In conclusion, the difference in dental age between 2009 to 2011 and 2021 was statistically significant. Factors such as environment and dietary habits have been found to be affected by dental development. However, there are disputes among some researchers about the exact factors, so it is suggested to further study the effects of environmental factors on tooth development.