Evaluating the Effectiveness of a Virtual Simulation Platform for Apexification Learning.

The traditional teaching methods for apexification face difficulties in meeting dental students' practical training needs. Herein, we aimed to find optimal techniques of learning apexification and to evaluate whether a virtual simulation platform for apexification learning was effective. A virtual simulation learning platform for apexification was developed. Ninety-nine 4th-year dentistry students were classified randomly into the control group (Con, receiving conventional teaching) and the experimental group (Exp, receiving virtual simulation teaching). Theoretical tests before (test 1) and after the virtual simulation training (test 2) assessed the effect of learning. In the Exp group, a questionnaire was used to assess student understanding of the virtual simulation platform. In the Exp group, the test-2 scores were significantly better compared those in the Con group (p < 0.001). Furthermore, in the Exp group, the test-2 scores exceeded those of test 1 (p < 0.001). Feedback using the questionnaire covered the evaluation of the Exp group for the virtual reality platform and offered useful suggestions. Applying the virtual simulation learning platform had positive effects on improving learning quality related to apexification.

Heterogeneity of T cells in periapical lesions and in vitro validation of the proangiogenic effect of GZMA on HUVECs.

AIM: T cells are key immunomodulatory cells in periapical lesions. This study aimed to explore the roles of T cells in chronic apical periodontitis (CAP) using single-cell RNA sequencing and to further investigate Granzyme A (GZMA) in angiogenesis regulation. METHODOLOGY: A total of five CAP samples were collected for single-cell RNA sequencing. We performed subcluster and lineage-tracing analyses for T cells. According to differential gene expression, distinct biological functions enriched in T cells of CAP were presented by gene set enrichment analysis (GSEA) and compared with healthy gingiva (data obtained from the GEO database). CellChat was used to explore potential ligand-receptor interactions between T cells and endothelial cells in CAP. The coculture of primary human umbilical vein endothelial cells (HUVECs) and Jurkat T cells, as well as the addition of GZMA recombinant protein, was used to validate the predicted pair of GZMA and coagulation factor II thrombin receptor (F2R) by RT-PCR, angiogenesis and migration assays. RESULTS: A transcriptomic atlas of 44 746 individual cells was constructed from the periapical lesions of five patients with CAP by single-cell RNA-seq, and eight cell types were identified. We identified nine subsets of T cells and deciphered the cellular heterogeneity of T cells in CAP at the functional level by subclustering and GSEA. Lineage tracing revealed a distinct lineage of T cells in CAP and predicted the transition of the T cellular state upon CAP. GSEA revealed multiple biological processes and relevant angiogenesis genes upregulated in CAP T cells. GZMA-F2R pairs were predicted by cell-cell interactions in CAP. High expression of GZMA and F2R was observed in the coculture of HUVECs and Jurkat T cells, and the proangiogenic capacity of the GZMA recombinant protein was emphasized by in vitro experiments. CONCLUSIONS: Our study provides novel insights into the heterogeneity of T cells in periapical lesions and reveals the potential role of GZMA in T cells in regulating angiogenesis in HUVECs.

Extracellular Vesicles for Dental Pulp and Periodontal Regeneration.

Extracellular vesicles (EVs) are lipid bound particles derived from their original cells, which play critical roles in intercellular communication through their cargoes, including protein, lipids, and nucleic acids. According to their biogenesis and release pathway, EVs can be divided into three categories: apoptotic vesicles (ApoVs), microvesicles (MVs), and small EVs (sEVs). Recently, the role of EVs in oral disease has received close attention. In this review, the main characteristics of EVs are described, including their classification, biogenesis, biomarkers, and components. Moreover, the therapeutic mechanism of EVs in tissue regeneration is discussed. We further summarize the current status of EVs in pulp/periodontal tissue regeneration and discuss the potential mechanisms. The therapeutic potential of EVs in pulp and periodontal regeneration might involve the promotion of tissue regeneration and immunomodulatory capabilities. Furthermore, we highlight the current challenges in the translational use of EVs. This review would provide valuable insights into the potential therapeutic strategies of EVs in dental pulp and periodontal regeneration.

The synergetic effect of pulp chamber extension depth and occlusal thickness on stress distribution of molar endocrowns: a 3-dimensional finite element analysis.

The aim of this study was to evaluate the effects of butt margin, occlusal thickness and pulp chamber extension depth on stress distributions on mandibular molar endodontically treated teeth (ETT) with EMAX endocrown restoration using 3-dimensional finite element analysis (FEA). The FEA models of endocrown with flat surface or curve surface of butt margin were firstly evaluated stress distributions, and then 9 FEA models of endocrown with 1-, 2- or 3-mm pulp chamber extension depth and 1-, 2- or 3-mm occlusal thickness were generated using curve surface of butt margin. In all of FEA models, a 200 N of vertical load or horizontal load was applied, and the von Mises stress (VMS) were evaluated. The results showed that curve surface of butt margin offered more adhesive area of enamel, though VMS on the prepared teeth was similar in flat surface and curve surface models. In 9 endocrown models, 2-mm occlusal thickness showed the lowest VMS on restorations, teeth tissue and root furcations, and 2-mm extension depth displayed the lowest VMS on root furcations under vertical load. Also, 2-mm extension depth exhibited the lowest VMS on restorations and teeth tissue under horizontal load. Within the limitations of this FEA study, the results of this study could be used as an aid for dentists to better devise endocrown restorations. Graphical abstract.

Effect of different endodontic access preparations on the biomechanical behavior of lithium disilicate and resin nanoceramic onlay restorations: An in vitro and 3D finite element analysis study.

STATEMENT OF PROBLEM: The effect of different sizes of endodontic access preparations on the performance of lithium disilicate glass-ceramic and resin nanoceramic onlay restorations is unclear. PURPOSE: The purpose of this in vitro and 3D finite element analysis study was to assess the effect of a conservative endodontic access cavity and a traditional endodontic access cavity on the fracture resistance and stress distribution of lithium disilicate glass-ceramic and resin nanoceramic onlays. MATERIAL AND METHODS: Sixty caries-free human mandibular molars were anatomically prepared for onlays and divided into 6 groups. After restoration with a lithium disilicate glass-ceramic (N=30) or resin nanoceramic (N=30), each material was further divided into traditional or conservative endodontic access cavity or intact tooth groups. After endodontic therapy and thermocycling, all specimens were submitted to a cycle fatigue test and then loaded until fracture. Failure type and location after debonding or fracture were classified and recorded. Furthermore, stress distribution in the 6 models was analyzed by using a finite element analysis software program. The data were compared by using a 2-way ANOVA test and the Tukey post hoc test (α=.05). The Weibull modulus and Weibull failure probabilities were also estimated for each group. RESULTS: The lithium disilicate glass-ceramic onlays had lower fracture resistance values than the resin nanoceramic onlays in both the traditional and conservative endodontic access cavity groups (P<.05). The fracture resistance of the 2 materials for onlays with endodontic access was significantly lower than that for the intact restorations (P<.05). No significant difference was found between the fracture resistance of Lava Ultimate restorations with traditional endodontic access and conservative endodontic access, while the fracture resistance of EMAX restorations with traditional endodontic access was significantly lower than that of restorations with conservative endodontic access (P<.05). A higher percentage of irreparable fractures was found in the 3 resin nanoceramic restoration groups. The von Mises stresses were higher in the lithium disilicate glass-ceramic restorations than in the resin nanoceramic restorations with the same access cavities. The von Mises stresses in the tooth structure were higher with the resin nanoceramic restorations than with the lithium disilicate glass-ceramic restorations with the same access cavities. CONCLUSIONS: An endodontic access cavity had more influence on the lithium disilicate glass-ceramic onlays than on the resin nanoceramic onlays, and a traditional endodontic access cavity significantly decreased the fracture resistance of lithium disilicate glass-ceramic onlays.