Chinese Journal of Dental Research, 01/2021

To describe the current scientific knowledge concerning stem cells obtained from the pulp of discarded primary teeth and to discuss their contribution to dental tissue engineering, a narrative review of the relevant literature published in the past decade (2010–2019) in the PubMed database was conducted. The promise that stem cells from human exfoliated deciduous teeth (SHED) hold as a viable biological option to heal diseased dental organs has been the focus of research over the past decade. New ways of inducing higher levels of differentiation through various bioactive agents and scaffolds have been pursued. Attention has also been paid to the regeneration potential of the discarded pulp tissue that originates from high caries risk or inflamed teeth. In conclusion, the field of stem cell engineering is constantly evolving, and although there is still much to learn about the behaviour of SHED, there are endless opportunities for their exploitation in dental regeneration. Keywords: deciduous tooth, dental pulp, stem cells, tissue engineering

Objective: To explore the potential therapies for infantile haemangiomas by targeting survivin, a member of the inhibitor of apoptosis protein family, using its specific small molecule inhibitor YM155. Methods: The expression of survivin in human haemangioma tissue was explored using immunohistochemistry and immunohistofluorescence. Cell cycle analysis and EdU assays were used to measure cell proliferation. Heochst33342 and Annexin V/PI double staining were performed to measure cell apoptosis. The capacity for self-renewal and multilineage differentiation potential of haemangioma stem cells (HemSCs) were measured by clone formation assays and multiple differentiation assays. Murine haemangioma models were established to explore the therapeutic efficacy of YM155 in vivo. Results: Strong staining of survivin in stromal cells was observed in the proliferative haemangioma tissue. In vitro studies demonstrated that YM155 induced cell cycle arrest and proliferation suppression of HemSCs, and also caused cell apoptosis at a higher concentration. YM155 impaired the self-renewal capacities and damaged multiple differentiation potentials of HemSCs. Importantly, YM155 suppressed blood vessel formation and cell proliferation, and induced cell apoptosis in murine haemangioma models. Conclusion: The present study demonstrated that targeting survivin using its specific suppressant, YM155, prevented the progression of infantile haemangioma by suppressing cell proliferation, inducing cell apoptosis and disrupting the differentiation potential of HemSCs. These results indicate a novel and promising therapeutic approach for the treatment of infantile haemangioma. Keywords: haemangioma stem cells, infantile haemangioma, survivin, YM155

Objective: To determine the crosstalk of osteogenesis and osteoclastogenesis of alveolar bone in lipopolysaccharide (LPS)-induced periodontitis in mice. Methods: A representative periodontitis model was established by treating mice with LPS, and osteoblasts and osteoclasts were cultured. Osteoblasts and osteoclasts were cocultured to determine the effects of LPS on the crosstalk of osteogenesis and osteoclastogenesis. Quantitative polymerase chain reaction (qPCR) was performed to determine the expression of osteoclastogenesis makers underlying the potential mechanisms. Results: The morphological and pathological changes in alveolar bone were observed in LPSinduced mice and LPS dose-dependently suppressed osteogenesis. The mRNA expression of cathepsin K, as a marker of osteoclasts, was accordingly downregulated in the coculture. The mRNA expression of osteoprotegerin was increased, while that of receptor activator of nuclear factor-κB ligand (RANKL) was decreased with an increased concentration of LPS. Moreover, the mRNA expression of toll-like receptor 4 (TLR4) was upregulated by LPS, whereas TLR4 knockout partially recovered osteoclast differentiation in the upper layer of the coculture. Conclusion: LPS dose-dependently suppressed osteogenesis but had a bidirectional effect on osteoclastogenesis. The combined effects of LPS on osteogenesis, osteoclastogenesis and their crosstalk via TLR4 account for alveolar bone loss in periodontitis. Keywords: coculture, lipopolysaccharide, osteoclastogenesis, osteogenesis, periodontitis

Objective: To develop a novel chondrocyte condensation culture strategy recapitulating developmental condensation and construct self-organised cartilaginous tissue for cartilage regeneration. Methods: Cell-condensation aggregate (CCA) was generated using the condensation culture method by sequential cell seeding. The chondrification capacities and biocompatibilities of CCA were assessed by comparison with the cell–scaffold complex (CSC), which was constructed by cell–scaffold coculture. Preclinical studies including implantation into nude mice subcutaneously and cartilage defect repair in rabbits were performed. Results: CCA constructed by condensation culture exhibited a morphology of self-organised cartilaginous tissue. Meanwhile, the condensation culture inhibited or abolished expression of HOX genes including HOXC4 and HOXD8, which was partially consistent with developmental HOX gene expression patterns and associated with enhanced regeneration capacities. Compared with CSC, CCA showed a higher capacity for chondrification and regeneration of rabbit cartilage defects. Conclusion: The therapeutic assessments indicate that CCA is an efficient therapeutic tool for cartilage regeneration, providing a new strategy for tissue engineering by mimicking developmental events. Keywords: cartilage defects, cartilage regeneration, cell condensation, HOX genes

Objective: To compare the accuracy of electronic apex locators in the presence of blood and CBCT images obtained with two different voxel sizes (0.125 mm and 0.25 mm) in determining root canal length up to the perforation area. Methods: Forty extracted, single-rooted human teeth were selected and an artificial root perforation (0.4 ± 0.1 or 1.0 ± 0.2 mm diameter) was created in the middle third of the root. The actual root canal length up to the perforation area was determined under a stereomicroscope. CBCT images were obtained with a voxel size of 0.125 mm and 0.25 mm. The root canal length up to the perforation area was measured on CBCT images and recorded as the radiographic length. The teeth were embedded in alginate and root canal length up to the perforation area was measured using two different EALs (DentaPort ZX [Morita, Tokyo, Japan] and Gold Reciproc motor [VDW, Munich, Germany]) and recorded as the electronic length. Results: In teeth with an artificial root perforation 0.4 mm in diameter, the measurements obtained with DentaPort ZX were more accurate than with the Gold Reciproc motor (P ˂ 0.05), and on CBCT images, more accurate measurements were obtained with a voxel size of 0.125 mm compared to 0.25 mm (P ˂ 0.05). In teeth with an artificial root perforation 1.0 mm in diameter, the radiographic length was closer to actual length than the electronic length (P ˂ 0.05). Conclusion: In artificial root perforations with a diameter of 0.4 mm, CBCT gives more reliable results than EALs. Both EAL and CBCT measurements were closer to actual length in artificial perforations that were 1.0 mm in diameter. Keywords: apex locator, CBCT, root perforation, voxel size

Objective: To evaluate the outcome of systematic video training on tooth preparation in veneer restoration and the practicability of the application of the digital evaluation system of scan design and assessment software. Methods: Ten residents were selected from a group enrolled on the first-year programme for the National Standard Training of Dentistry in the Department of Prosthodontics, College of Stomatology, Ninth People’s Hospital Affliated with Shanghai Jiao Tong University, School of Medicine. First, each student prepared five teeth based on their knowledge and clinical experience, and then received systematic video training on veneer preparation. Before and after the training, the evaluation of the effects of training was conducted on the prepared teeth by measuring the continuity of the finishing line and tooth reduction amount automatically using the prepCheck 2.0 (Dentsply Sirona, Charlotte, NC, USA) CAD/CAM system. Results: The results showed a significant difference in the quality of finishing line continuity pre- and post-training. Furthermore, the data for tooth reduction after training, which met standard values, improved remarkably, increasing from 32.40 ± 7.82% to 60.50 ± 5.48%. Conclusions: Video training could significantly enhance the quality of tooth preparation for veneers. Moreover, the digital evaluation system could serve as an ideal alternative for tooth preparation evaluation for preclinical students, offering new insights for clinical education. Keywords: aesthetic rehabilitation, CAD/CAM, digital evaluation system, tooth preparation

Objective: To verify horizontal jaw relations using anatomical marks on a cast and evaluate the efficiency and accuracy of the test on checking the horizontal relation. Methods: A total of 200 patients with a loss of posterior occlusion were recruited. After casts were made and the horizontal jaw relation was recorded, the pterygomaxillary notch and retromolar pad were identified bilaterally on the maxillary and mandibular casts. On each cast, a vertical line was drawn to bisect the anatomical landmarks and the distance between the two vertical lines was measured. Using the result of the wax try-in appointment and the corresponding measurements, a diagnostic test was conducted. A receiver operating curve was created and the maximum horizontal distance between bisecting points that still obtained correct jaw relations was determined to be a criterion. The accuracy of the test to verify horizontal jaw relations was evaluated. Results: The area under the curve of the receiver operating curve was 0.833 (P < 0.05). With a maximum Youden index, the d value threshold was 1.0 mm. Using 1.0 mm as a criterion to check the horizontal relation, the sensitivity of the test was 0.76 and the specificity was 0.93. The kappa value for different researchers was calculated to be 0.79 (P < 0.05). The intraexaminer 1 reliability gave a kappa value of 0.76 (P < 0.05), and intraexaminer 2 gave a value of 0.81 (P < 0.05). Conclusion: The test for verifying the accuracy of horizontal jaw relations is reliable. If horizontal distance is measured as greater than 1.0 mm at the jaw relation record appointment, the recorded horizontal jaw relationship may be wrong and need to be reexamined. Keywords: cast, diagnostic test, horizontal relationship, pterygomaxillary notch, retromolar pad