Objective:To explore the method of obtaining the key parameters of the average value articulator in healthy people based on mandibular movement trajectory data, with a view to providing a reference for the clinical application of the average value articulator.Methods:One hundred healthy volunteers (42 males and 58 females) with individual normal occlusion, aged 18-55 years old, who met the inclusion criteria were recruited from Beijing, and their mandibular movement trajectory data were collected. The left and right sagittal condylar inclination(SCI) and transversal condylar inclination(TCI) were obtained from the values of the articulator parameters which were generated in the mandibular movement analysis system.The SCI and TCI were grouped by gender and calculated separately for the two groups and the overall sample; the gender differences in the two parameters and the differences between the mean values of the two parameters and the average value articulator empirical values (35° for SCI and 15° for TCI) for the overall sample were compared.Results:The differences between SCI (35.8°±7.4°) and TCI [11.2° (11.3°)] in males and the corresponding parameters [35.6°±8.3° and 10.8° (9.5°), respectively] in females were not statistically significant ( t=0.10, P=0.922; Z=-0.60, P=0.552); the overall sample SCI (35.7°±7.9°) did not differ statistically from the average value articulator empirical value ( t=1.23, P=0.221), and the overall sample TCI [10.9° (10.3°)] was significantly smaller than the average value articulator empirical value ( W=5 825.00, P<0.001). Conclusions:The mandibular movement trajectory data of 100 adults with individual normal occlusion in this study shows that the gender factor does not affect the setting of the key parameters of the average value articulator, the SCI of the average value articulator empirical values is appropriate, and the TCI has the possibility of being on the large side. In the clinical use of the articulator to assist in the design of restorations, the parameter values should be rationally adjusted according to the actual situation of the patient′s dentition and mandibular movement.

Objective To study the irradiation dose of organs at risk (OAR) in involved field radiation and extended field radiation in patients with thoracic esophageal cancer who received intensity modulated radiotherapy (IMRT). Methods A total of 40 patients with thoracic esophageal cancer were treated with IMRT. The involved field, extended field, and OAR were outlined to generate IMRT plans. The conformity index (CI) and homogeneity index (HI) of planning target volume (PTV) and the irradiation parameters of OAR were evaluated for the two plans. Paired t-test was used for comparison of irradiation parameters. Results The PTV of both plans received the prescribed dose. There were no significant differences in CI and HI of PTV between the two groups (P = 0.317, 0.130). There were significant differences in average lung dose, lung V₅, lung V₂₀, lung V₃₀, spinal cord D_mean, heart D_mean, heart D_max, heart V₃₀, heart V₄₀, and heart V₆₀ between the two groups (P < 0.01). Conclusion Compared with the extended field, the involved field can reduce the irradiation dose of ORA in patients with thoracic esophageal cancer, thus reducing the risk of radiation.

Objective:To develop an efficient and robust method based on three dimensional facial landmarks for evaluating chin region asymmetry at the soft tissue level and to compare it with the tradi-tional mirror-overlap analysis method in order to test its availability.Methods:Standard symmetrical face was used for mental tubercle coordinate transformation so as to filter soft tissue three dimensional spatial angle and construct corresponding three dimensional spatial angle wireframe template.Ten patients aged 12-32 years with clinical chin region asymmetry diagnosis at the Department of Orthodontics of Peking University Hospital of Stomatology from November 2020 to November 2021 were randomly selected.Three dimensional soft tissue face scan data of the patients were collected by three dimensional face scanner and the landmark points were automatically determined by the Meshmonk non-rigid registration algorithm pro-gram,and in this way,the asymmetric three dimensional spatial angle wireframe template and corre-sponding spatial angle parameters were generated.Mirror-overlap analysis of face scan data was also per-formed in Geomagic Studio 2015 software and deviation color maps were generated.This study took mirror-overlap analysis as the gold standard method,the response rate of chin region asymmetry was eva-luated by the outcomes of the mirror-overlap analysis and three dimensional spatial angle wireframe tem-plate analysis.Results:Nine three dimensional spatial angle indicators were selected through coordinate transformation,and the response rate was calculated using mirror-overlap analysis as the gold standard method.Among these ten selected patients,the response rate of the total chin region asymmetry was 90％(9/10).Using the deviation value of mirror-overlap analysis as a reference,the response rate of chin region asymmetry in the X dimension was 86％,the response rate of chin region asymmetry in the Y dimension was 89％,and the response rate of chin region asymmetry in the Z dimension was 100％.Conclusion:The three dimensional soft tissue spatial angle wireframe template proposed in this study has some feasibility in evaluating chin region asymmetry at the soft tissue level,and its ability to recognize asymmetry separately in the three dimensional direction is better than the mirror-overlap analysis method,and the indicators recognition rate still needs to be further improved.

Objective This study proposes a chairside digital design and manufacturing method for band and loop space maintainers and preliminarily validates its clinical feasibility.Methods Clinical cases of 10 children requiring space maintenance caused by premature loss of primary teeth were collected.Intraoral scan data of the affected children were also collected to establish digital models of the missing teeth.Using a pediatric band and loop space maintainer de-sign software developed by our research team,a rapid personalized design of band and loop structures was achieved,and a digital model of an integrated band and loop space maintainer was ultimately generated.A chairside space maintainer was manufactured through metal computer numerical control machining for the experimental group,whereas metal 3D printing in the dental laboratory was used for the control group.A model fitting assessment was conducted for the space maintainers of both groups,and senior pediatric dental experts were invited to evaluate the clinical feasibility of the space maintainers with regard to fit and stability using the visual analogue scale scoring system.Statistical analysis was also performed.Results The time spent in designing and manufacturing the 10 space maintainers of the experimental group was all less than 1 h.Statistical analysis of expert ratings showed that the experimental group outperformed the control group with regard to fit and stability.Both types of space maintainers met clinical requirements.Conclusion The chairside digital design and manufacturing method for pediatric band and loop space maintainers proposed in this study can achieve same-day fitting of space maintainers at the first appointment,demonstrating good clinical feasibility and significant potential for clinical application.

Objective:To establish an intelligent registration algorithm under the framework of original-mirror alignment algorithm to construct three-dimensional (3D) facial midsagittal plane automatically. Dynamic Graph Registration Network (DGRNet) was established to realize the intelligent registration, in order to provide a reference for clinical digital design and analysis.Methods:Two hundred clinical patients without significant facial deformities were collected from October 2020 to October 2022 at Peking University School and Hospital of Stomatology. The DGRNet consists of constructing the feature vectors of key points in point original and mirror point clouds (X, Y), obtaining the correspondence of key points, and calculating the rotation and translation by singular value decomposition. Original and mirror point clouds were registrated and united. The principal component analysis (PCA) algorithm was used to obtain the DGRNet alignment midsagittal plane. The model was evaluated based on the coefficient of determination (R 2) index for the translation and rotation matrix of test set. The angle error was evaluated on the 3D facial midsagittal plane constructed by the DGRNet alignment midsagittal plane and the iterative closet point (ICP) alignment midsagittal plane for 50 cases of clinical facial data. Results:The average angle error of the DGRNet alignment midsagittal plane and ICP alignment midsagittal plane was 1.05°±0.56°, and the minimum angle error was only 0.13°. The successful detection rate was 78% (39/50) within 1.50° and 90% (45/50) within 2.00°.Conclusions:This study proposes a new solution for the construction of 3D facial midsagittal plane based on the DGRNet alignment method with intelligent registration, which can improve the efficiency and effectiveness of treatment to some extent.