Search

Objective To analyze the initial displacement of the upper central incisor and stress distribution of periodontal ligament under different torque values of upper incisors under the action of a four⁃curved auxiliary arch to provide a reliable basis for the safety of clinical application of four⁃curved auxiliary arches. Methods A three⁃dimen⁃ sional finite element model for torque control of upper anterior teeth with a homemade quadrilateral auxiliary arch was established. Four different states were analyzed: molar ligation without extraction space (group A), microimplant ligation without extraction space (group B), molar recovery with extraction space closure (group C) (the adductive traction force was set at 115 g) and microimplant recovery with extraction space closure (group D) (the adductive traction force was set at 115 g). When four types of torque (0.5 N, 1.0 N, 1.5 N, and 2.0 N) were applied. The initial displacement of upper central incisors and the stress distribution of periodontal ligament in 16 groups (A1⁃A4, B1⁃B4, C1⁃C4, D1⁃D4) were ob⁃ served. Results Under different conditions, as the strength of the four⁃curve auxiliary arch increases, the maxillary an⁃ terior teeth has crown labial inclination and a root lingual inclination. The displacement of the incisor tip increases with the increase in the loading force of the torque auxiliary arch, and the displacement of the incisor root apex increases as the force increases. The difference in incisor⁃apex displacement distance in A1⁃A4, B1⁃B4, C1⁃C4, D2 and D4 groups increased as the torque force increases, while the difference between the D3 group and D1 and D2 groups decreased slightly. The stress of the cervical periodontal ligament of the upper central incisor did not exceed the stress of the peri⁃ odontal ligament in the following groups: A1, A2, B1, B2, B3, C1, C2, D1, and D2. The stress of the lip side of the up⁃ per central incisor did exceed the stress of the periodontal ligament in the following groups: A3, A4, B4, C3, C4, D3, and D4. In other words, when using the four⁃curved auxiliary arch as an implant anchorage, the force applied in the ab⁃ sence of extraction space should not exceed 1.5 N, and the force applied in the adduction of extraction space should not exceed 1.0 N. When using the nonimplant anchorage, the force applied in the absence of extraction space and the ad⁃ duction of extraction space should not exceed 1.0 N. In addition, the range of force should not exceed the maximum stress of the periodontal ligament in the cervical region such that the effective and safe torque movement can be achieved. Under other stress conditions, the stress of the labial and cervical periodontal ligament of the upper central in⁃ cisor exceeded the stress value (2.6 × 10 ⁃ 2 MPa). The stress value of periodontal ligament was 2.6 × 10 ⁃ 2 MPa in all groups. Conclusion A four⁃curved auxiliary arch has a significant effect on the upper anterior teeth, and the use of mi⁃ croimplants can better control root movement such that the crown of upper central incisors cannot be excessively lip in⁃ clined.

The normal torque angle of the maxillary anterior teeth is an important factor in the aesthetics and func⁃ tion of the anterior teeth, and torque control of the front teeth is an extremely important aspect of the correction process. At present, the normal torque angle of the front teeth is among the phase Ⅲ clinical test items recognized by the Ameri⁃ can orthodontic professional committee; consequently, good control of front teeth torque is of great significance to the aesthetics of the upper anterior teeth. In this paper, the influence of a lip appliance on the bad torque of upper anterior teeth and the associated methods of control are reviewed in detail. The advantages and disadvantages of various control methods for the anterior teeth and the significance of correct anterior teeth torque angle are summarized. The existing re⁃ search results indicate that the torsion of a straight arch wire applied directly to individual teeth is too great, making it difficult to enter the groove. Although the bending of the arch wire overcomes these shortcomings, the procedure is cum⁃ bersome; it stimulates the soft tissue of the vestibular groove and increases the patient􀆳s discomfort. The bending mecha⁃ nism of the rocking chair is more complicated; it is greatly affected by the friction between the arch wire and the brack⁃ et and is not conducive to closing the tooth extraction gap using the sliding method. The portal auxiliary arch and the single bending torque are suitable for correcting the torque angle of a single tooth. Auxiliary arch torque can be used to correct the upright upper anterior teeth during the process of closing the extraction space and after adduction; therefore, this procedure is worth popularizing. However, the accuracy of orthodontic control of anterior teeth torque requires fur⁃ ther study.

Objectives: The aim of this study was to investigate the role of p75 neurotrophin receptor (p75NTR) in regulating the mouse alveolar bone development and the mineralization potential of murine ectomesenchymal stem cells (EMSCs). Moreover, we tried to explore the underlying mechanisms associated with the PI3K/Akt/β‐catenin pathway. Materials and methods: p75NTR knockout (p75NTR−/−) mice and wild‐type (WT) littermates were used. E12.5d p75NTR−/− and WT EMSCs were isolated in the same pregnant p75NTR‐/+ mice from embryonic maxillofacial processes separately. Mouse alveolar bone mass was evaluated using micro‐CT. Differential osteogenic differentiation pathways between p75NTR−/− and WT EMSCs were analysed by RNA‐sequencing. The PI3K inhibitor LY294002 and PI3K agonist 740Y‐P were used to regulate the PI3K/Akt pathway in EMSCs. p75NTR overexpression lentiviruses, p75NTR knock‐down lentiviruses and recombined mouse NGF were used to transfect cells. Results: The alveolar bone mass was found reduced in the p75NTR knockout mouse comparing to the WT mouse. During mineralization induction, p75NTR−/− EMSCs displayed decreased osteogenic capacity and downregulated PI3K/Akt/β‐catenin signalling. The PI3K/Akt/β‐catenin pathway positively regulates the potential of differential mineralization in EMSCs. The promotive effect of p75NTR overexpression can be attenuated by LY294002, while the inhibitory effect of p75NTR knock‐down on Runx2 and Col1 expression can be reversed by 740Y‐P. Conclusion: Deletion of p75NTR reduced alveolar bone mass in mice. P75NTR positively regulated the osteogenic differentiation of EMSCs via enhancing the PI3K/Akt/β‐catenin pathway. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: The aim of this study was to investigate whether sclerostin (SOST) regulates the osteogenic differentiation of rat ectomesenchymal stem cells (EMSCs) and whether SOST and low‐affinity nerve growth factor receptor (LNGFR) regulate the osteogenic differentiation of EMSCs. Materials and methods: EMSCs were isolated from embryonic facial processes from an embryonic 12.5‐day (E12.5d) pregnant Sprague‐Dawley rat. LNGFR+ EMSCs and LNGFR− EMSCs were obtained by fluorescence‐activated cell sorting and were subsequently induced to undergo osteogenic differentiation in vitro. SOST/LNGFR small‐interfering RNAs and SOST/LNGFR overexpression plasmids were used to transfect EMSCs. Results: LNGFR+ EMSCs displayed a higher osteogenic capacity and lower SOST levels compared with LNGFR− EMSCs. SOST silencing enhanced the osteogenic differentiation of LNGFR− EMSCs, while SOST overexpression attenuated the osteogenic differentiation of LNGFR+ EMSCs. Moreover, LNGFR was present upstream of SOST and strengthened the osteogenic differentiation of EMSCs by decreasing SOST. Conclusions: SOST alleviated the osteogenic differentiation of EMSCs, and LNGFR enhanced the osteogenic differentiation of EMSCs by decreasing SOST, suggesting that the LNGFR/SOST pathway may be a novel target for promoting dental tissue regeneration and engineering. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to investigate differences of odonto-differentiation between P75-neurotrophin receptor (P75-NTR)-positive ectomesenchymal stem cells (P75+EMSCs) and P75- NTR-negative ectomesenchymal stem cells (P75+EMSCs), and their underlying mechanisms. Materials and methods: Primary cranial neural crest-derived cells (CNC) were isolated from the first branchial arches, and P75+EMSCs and P75+EMSCs were sorted by fluorescence-activated cell sorting. Differentiation of P75+EMSCs or P75+EMSCs into odontoblast-like cells was induced by dental epithelial cells in vitro or in vivo. Differential gene expression profiles between P75+EMSCs and P75+EMSCs were analysed by microarray assay. Smad4-specific small interfering RNA and activator kartogenin were used to treat the cells, to evaluate effects of Smad4 in odonto-differentiation of P75+EMSCs or P75+EMSCs. Results: Under induction of dental epithelium conditioned medium, P75+EMSCs had more mineralized node formation and higher expression of Dmp1 and Dspp compared to P75+EMSCs. In our in vivo study, graft of P75+EMSCs recombination with dental epithelium showed higher expression of DMP1 and DSP. Knock-down of Smad4 in P75+EMSCs significantly downregulated expression of DMP1 and DSP, while activation of Smad4 in P75+EMSCs by the activator kartogenin, significantly increased DSP and DMP1 expression. Conclusions: P75+EMSCs showed more odonto-differentiation potential than P75+EMSCs both in vivo and in vitro. Smad4 played a critical role in determination of odonto-differentiation potential of CNC-derived EMSCs. [ABSTRACT FROM AUTHOR]

Abstract: Several populations of stem cells, including those from the dental pulp and periodontal ligament, have been isolated from different parts of the tooth and periodontium. The characteristics of such stem cells have been reported as well. However, as a common progenitor of these cells, ectomesenchymal stem cells (EMSCs), derived from the cranial neural crest have yet to be fully characterized. The aim of this study was to better understand the characteristics of EMSCs isolated from rat embryonic facial processes. Immunohistochemical staining showed that EMSCs had migrated to rat facial processes at E11.5, while the absence of epithelial invagination or tooth-like epithelium suggested that any epithelial–mesenchymal interactions were limited at this stage. The p75 neurotrophin receptor (p75NTR), a typical neural crest marker, was used to select p75NTR-positive EMSCs (p75+ EMSCs), which were found to show a homogeneous fibroblast-like morphology and little change in the growth curve, proliferation capacity, and cell phenotype during cell passage. They also displayed the capacity to differentiate into diverse cell types under chemically defined conditions in vitro. p75+ EMSCs proved to be homogeneous, stable in vitro and potentially capable of multiple lineages, suggesting their potential for application in dental or orofacial tissue engineering. [Copyright &y& Elsevier]

Objective: The aim of this study was to investigate the spatiotemporal expression and potential role of p75NTR in tooth morphogenesis and tissue mineralization. Materials and methods: The dynamic morphology of the four stages (from the beginning of E12.5 d, then E13.5 d and E15.5 d, to the end of E18.5 d) was observed, and the expressions of p75NTR and Runx2 were traced. The ectomesenchymal stem cells (EMSCs) were harvested in vitro, and the biological characteristics were observed. Moreover, the mineralization capability of EMSCs was evaluated. The relations between p75NTR and ALP, Col‐1 and Runx2 were investigated. Results: The morphologic results showed that the dental lamina appeared at E12.5 d, the bud stage at E13.5 d, the cap stage at E15.5 d and the bell stage at E18.5 d. p75NTR and Runx2 showed the similar expression pattern. EMSCs from the four stages showed no significant difference in proliferation. But the positive rate of p75NTR in the E12.5 d cells was significantly lower than that in the other three stages (P < 0.05). Moreover, the higher positive rate of p75NTR the cells were, the stronger mineralization capability they showed. p75NTR was well positively correlated with the mineralization‐related markers ALP, Col‐1 and Runx2, which increased gradually with the mature of dental germs. Conclusion: p75NTR might play an important role in the regulation of tooth morphogenesis, especially dental hard tissue formation. [ABSTRACT FROM AUTHOR]

Content-sharing is one of the major applications of vehicular networks. To fully utilize the spectrum and the connection time, rate-compatible codes are required when sharing content. In this paper, we present a simple and flexible method to construct low-complexity rate-compatible codes for content sharing. We first present a novel construction framework for rate-compatible codes via recursive block Markov superposition transmission (rBMST). In the proposed construction, the shared content is partitioned into equal-length data chunks and transmitted directly, while their replicas are taken as the inputs of a given number of parallel systematic encoders to generate parity-check chunks. These parity-check chunks are then transmitted in parallel in a recursive block Markov superposition transmission manner. The proposed construction is flexible in the sense that codes with arbitrary rates can be obtained by adjusting the number of parallel rBMST encoders and the number of randomly punctured bits. We show that the simplest construction, using repetition to generate the parity-check chunks, leads to high-performance and low-complexity rate-compatible rBMST (RC-rBMST) codes. Specifically, the extrinsic information transfer (EXIT) chart analysis shows that asymptotic thresholds of the repetition-based RC-rBMST (RB-RC-rBMST) codes are within 0.25 dB of the channel capacities for a wide range of coding rates. Numerical results are presented to confirm the advantages of the RB-RC-rBMST codes in performance and complexity. Particularly, the RB-RC-rBMST codes perform as well as BMST-R codes but with much lower computational complexities. [ABSTRACT FROM AUTHOR]

Objective To observe the microscopic characteristic of the bonding interface between resin cement and dentin before and after using Nd: YAG laser, and evaluate the effects of the Nd: YAG laser on the shear bond strength of 3 resin cements to dentin. Methods 30 human premolars were cut into nearly equal halves, prepared to expose the dentin and randomly divided into two groups: Laser group and control group. The teeth in the laser group were processed with pulse Nd: YAG laser(0.8 W, 10Hz) for 25 s, and then the teeth were bonded using 3 resin cements (RelyX ARC, Panavia F and RelyX Unicem) to dentin. All teeth in the control group were directly filled with 3 cements. The shear bond strength of specimens was measured. Each fractured specimen was examined under dental microscope. And 6 new human premolars were prepared into standard bonding specimens. After 3 teeth processed with pulse Nd YAG laser, all teeth were bonded using 3 resin cements. To observe the microscopic characteristics of the bonding interface between resin cements and dentin. Results Nd: YAG laser on dentin surface could increase bond strength of Panavia F and RelyX Unicem (P<0.05). And the laser could decrease bond strength of RelyX ARC (P<0.05). Most of the fractured adhesive dentin surfaces were adhesive failure modes. Scanning electron microscope (SEM) observation demonstrated that Nd: YAG laser irradiation on dentin surface could decrease the hybrid layer and resin tags between the resin cements (RelyX ARC and Panavia F) and dentin. The interface between RelyX Unicem and dentin showed no obvious change, and resin tags were not observed. Conclusion Nd: YAG laser on dentin surface can increase bond strength of Panavia F and RelyX Unicem. Therefore, they can be used together in clinic. [ABSTRACT FROM AUTHOR]