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.

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.

Resistance fracture of minimally prepared endocrowns made by three types of restorative materials: a 3D finite element analysis.

A thin endocrown restoration was often applied in endodontically treated teeth with vertical bite height loss or inadequate clinical crown length. A model of mandibular molars made by endocrown restoration with 1 mm thickness and 2 mm depth of pulp chamber was constructed and imported into FEA ANSYS v18.0 software. The three CAD/CAM materials, feldspathic (Mark2), lithium disilicate (EMAX), and lava ultimate (LU), were assigned, and the five load indenters were loaded on the full occlusal (FO), occlusal center (OC), central fossa (CF), buccal groove (BG), and mesiobuccal cusp (MC) of restoration in the model. The MinPS and MaxPS of the thin endocrown were significantly higher than those of tooth tissue in five types of loads except for the LU endocrown loaded in the FO group. The smaller the contact surface of the load was, the higher MaxPS and MinPS were. MaxPS and MinPS of the MC were the highest, followed by the BG and CF in the restoration. In the stress distribution of tooth tissue, MaxPS in the LU endocrown accumulated at the external edge of enamel and was significantly higher than MaxPS in Mark2 and EMAX endocrown concentrated on the chamber wall of dentin under OC, CF and BG loads. Within the limitations of this FEA study, the LU endocrown transferred more stress to tooth tissue than Mark2 and EMAX, and the maximum principal stress on endocrown restoration and tooth tissue at the mesiobuccal cusp load was higher than that at the central fossa and buccal groove load.

The practicability of different preparation of mandibular molar restored by modified endocrown with intracanal extension: Computational analysis using finite element models.

BACKGROUND AND OBJECTIVE: Post-core-crown (PCC) and endocrown are two common restorative methods for severely damaged molars, but exhibit disadvantages. This study aimed to explore the practicability of modified endocrown with a 2 mm intracanal extension (MED) to restore defective teeth using finite element analysis (FEA). METHODS: Five groups of numerical models of mandibular molars restored by three MEDs, a PCC, and a routine endocrown after root canal treatment were devised by FEA software. We constructed 4 mm, 3 mm, and 2 mm thickness of MED restorations to restore mandibular molars that were prepared to 1 mm, 2 mm, and 3 mm from the cemento-enamel junction (CEJ). Furthermore, PCC and routine endocrown were used to compare the stress distribution with MED. Lithium disilicate glass-ceramics (EMAX) and resin nanoceramics (LU) were considered restorative materials, and a vertical load of 600 N and an oblique load of 200 N were applied to the restorations. RESULTS: In three MEDs by LU, 2 mm thickness of restoration generated the highest stress on prepared teeth, while the thickness of EMAX did not significantly influence the stress value. MED by LU generated higher stress around the CEJ, and reduced the stress on the middle and lower root compared to MEDs by EMAX, PCC by EMAX, and PCC by LU. MED by EMAX caused lower stress around the CEJ, and generated higher stress in the chamber walls after extended root canals compared with MED by LU, endocrowns by LU, and endocrowns by EMAX. There was an evident stress concentration at the last but one layer, which was a thin area of the tooth root in all restorative models. CONCLUSIONS: The use of modified endocrown may be considered an effective restorative method to restore defective mandibular molar, but suitable restorative material must be selected based on the tooth preparation method and deficiencies in the tooth structure.