Biomechanical Comparison of Six Different Root-Analog Implants and the Conventional Morse Taper Implant by Finite Element Analysis.

Taper implants differ greatly from anatomical teeth in shape. In this study, seven three-dimensional finite element models were established, including a conventional taper implant and six root-analog implants with different root numbers and shapes. Vertical, horizontal, and oblique instantaneous loads of 100 N were applied to the models to obtain stress distribution in the implant, mucosa, cortical bone, and cancellous bone. ANSYS was used to perform the analysis under hypothetical experimental conditions. We find the stresses in all the implants and surrounding tissues varied by loading direction, the sequence of stress magnitude is vertical load, oblique load, and then horizontal load. The maximum stress values in root-analog implants were significantly less than in the taper implant. Moreover, stress distribution in the former was equalized contrary to the concentrated stress in the latter. Root-analog implants with different root geometry also revealed a pattern: stresses in multiple-root implant models were lower than those in single-root implants under the same load. The implant with a long and rounded root distributed the stress more uniformly, and it was mainly concentrated on the implant itself and cancellous bone. However, the opposite effect was observed in the short implant on mucosa and cortical bone. The root geometry of anatomical teeth can modify their functions. A uniform-shaped implant can hardly meet their functional requirements. Thus, the root-analog implant could be a possible solution.

Melatonin exerts neuroprotective effects by inhibiting neuronal pyroptosis and autophagy in STZ-induced diabetic mice.

Diabetes mellitus (DM) patients are at a higher risk of developing brain injury characterized by neuronal death. Melatonin, a hormone produced by the pineal gland, exerts neuroprotective effects against brain damage. However, the effect of melatonin on diabetes-induced brain injury has not been elucidated. This study was to evaluate the role of melatonin against neuronal death in DM and to elucidate the underlying mechanisms. Herein, we found that melatonin administration significantly alleviated the neuronal death in both streptozotocin (STZ)-induced diabetic mice and high glucose (HG)-treated neuronal cells. Melatonin inhibited neuronal pyroptosis and excessive autophagy, as evidenced by decreased levels of NLRP3, cleaved caspase-1, GSDMD-N, IL-1ß, LC3, Beclin1, and ATG12 both in vivo and in vitro. MicroRNA-214-3p (miR-214-3p) was decreased in DM mice and HG-treated cells, and such a downregulation was corrected by melatonin, which was accompanied by repression of caspase-1 and ATG12. Furthermore, downregulation of miR-214-3p abrogated the anti-pyroptotic and anti-autophagic actions of melatonin in vitro. Our results indicate that melatonin exhibits a neuroprotective effect by inhibiting neuronal pyroptosis and excessive autophagy through modulating the miR-214-3p/caspase-1 and miR-214-3p/ATG12 axes, respectively, and it might be a potential agent for the treatment of brain damage in the setting of DM.

IGF-1 and BMP-7 synergistically stimulate articular cartilage repairing in the rabbit knees by improving chondrogenic differentiation of bone-marrow mesenchymal stem cells.

Knee injury is known as a frequently occurred damage related to sports, which may affect the function of cartilage. This study aims to explore whether Insulin-like growth factor 1 (IGF-1) and bone morphogenetic protein-7 (BMP-7)-modified bone-marrow mesenchymal stem cells (BMSCs) affect the repair of cartilage damage found in the knee. Primarily, BMSCs were treated with a series of pEGFP-C1, IGF-1, and BMP-7, followed by determination of IGF-1 and BMP-7 expression. A rabbit cartilage defect model was also established. Afterfward, cell morphology, viability, cartilage damage repair effect, and expression of collagen I and collagen II at the 6th and the 12th week were measured. BMSCs treated with pEGFP-C1/IGF-1, pEGFP-C1/BMP-7, and pEGFP-C1/BMP-7-IGF-1 exhibited elevated expression of BMP-7 and IGF-1. Besides, BMSCs in the P10 generation displayed decreased cell proliferation. Moreover, BMSCs treated with IGF-1, BMP-7, and IGF-1-BMP-7 showed reduced histological score and collagen I expression while elevated collagen II expression, as well as better repair effect, especially in those treated with IGF-1-BMP-7. Collectively, these results demonstrated a synergistic effect of IGF-1 and BMP-7 on the BMSC chondrogenic differentiation on the articular cartilage damage repair in the rabbit knees, highlighting its therapeutic potential for the treatment of articular cartilage damage.

[Construction and biological assessment of tissue engineering intervertebral disc].

OBJECTIVE: To investigate the value of bone marrow-mesenchymal stem cells (BM-MSCs) transformed by nucleus pulposus (NPs) for construction of tissue engineering disc. METHODS: BM-MSCs and fetal NPs were cultured in vitro, planted on polylactic acid-polyglycolic acid copolymer (PLGA), and observed with inverted microscope and scanning electronic microscope. PLGA scaffolds with adherent BM-MSCs and NPs, as well as BM-MSCs and NPs suspension were implanted into intervertebral discs of New Zealand white rabbits, respectively. Intervertebral signal intensity was evaluated by Thompson grading 12 weeks later. Proteoglycan and type IIcollagen were determined by spectrophotometric method and immunohistochemistry, respectively. RESULTS: Spindle or multi-angular BM-MSCs turned into fibro-like phenotype coculture of BM-MSCs and NPs, which grew well with normal morphology when they attached on PLGA scaffolds. There was statistical difference in intervertebral signal intensity, and the expression of proteoglycan and type IIcollagen between PLGA scaffolds group and control group (P < 0.05), the content of proteoglycan was (3.93 ± 0.31) mg/100 mg in the PLGA scaffolds group whereas (3.52 ± 0.26) mg/100 mg in the control group. CONCLUSIONS: BM-MSCs can be induced into NPs by cocultivation, and PLGA scaffolds can provide good growing conditions, and maintain high mechanical properties and spacial structure which meet the requirement of tissue engineering disc to prevent degeneration.

[Effect of biopure MTAD on removing smear layer in vitro].

OBJECTIVE: To evaluate the ability of Biopure MTAD in removing smear layer in vitro. METHODS: Forty extracted single-rooted human teeth were randomly divided into five groups: Distilled water in group A, 5.25% NaClO and 17% EDTA in group B, 1.3% NaClO in group C, 1.3% NaClO and Biopure MTAD in group D, 1.3% NaClO and 3% EDTA in group E. The canals were prepared and irrigated with one of the five different irrigating agent respectively. The amount of smear layer and erosion on the surface of the root canal walls were examined with scanning electron microscope. RESULTS: The whole surfaces of root canals in group A and C were covered by smear layer. The surfaces of root canals in the coronal and middle thirds of samples in group B, D, E were free of smear layer (P>0.05) and the apical third of canals in the group D were significantly cleaner (P<0.05) than that in group B and E. The coronal and middle sections were significantly eroded in group B compared with group D and E (P<0.05). The degree of erosion in the apical section was not statistically different among group B, D and E (P>0.05). CONCLUSION: Biopure MTAD and 1.3% NaClO are effective irrigating agents for removal of the smear layer on the surface of root canal. There is no significant change in the structure of the surface of root canal.

[Comparison of two means for evaluation of apical microleakage].

PURPOSE: To compare the consistency of two means of evaluating the apical microleakage. METHODS: Forty-nine extracted single-rooted human teeth were divided into 3 experimental groups of 15 teeth each, in addition to a positive and negative control group of 2 teeth each. The teeth were instrumented, then obturated using lateral condensation and one of three endodontic sealers: AH Plus(group A), Cortisomol(group B) and zinc oxide eugenol(group C). The apical microleakage was measured by transparent tooth technique or dye dissolution each. SPSS 12.0 software package was used for One-way ANOVA and Kruslal-Wallis test. RESULTS: The two methods both showed that the microleakage in group A was significantly less (P<0.05) than that in group B and C. There was no significant difference between group B and C(P>0.05). CONCLUSION: Based on the dye penetration method, there is some consistency between the transparent tooth technique and dye dissolution method for evaluating apical microleakage.

[Evaluation of BioPure MTAD as an endodontic irrigant on the apical sealing ability of AH Plus sealer in vitro].

PURPOSE: To evaluate whether BioPure MTAD could affect the apical sealing ability of AH Plus sealer in vitro. METHODS: Forty-four extracted single-rooted human teeth were randomly divided into six groups. The canals were treated with distilled water,1.3%NaClO,5.25 %NaClO+17%EDTA,1.3%NaClO+BioPure MTAD and 1.3%NaClO+3%EDTA endodontic irrigants, respectively. After obturated, the teeth were made transparent and permitted dye penetration,then measured by using a stereoscopic microscope. SPSS 12.0 software package was used for One-way ANOVA. RESULTS: The microleakages lengths of obturated root canals in group C,D,E,F were (1.81+/-0.73)mm, (0.53+/-0.49)mm, (0.40+/-0.44)mm and (0.39+/-0.55)mm, respectively.Group C had significantly more leakage than group D,E,F(P<0.05), but there were no significant differences among group D,E,F(P>0.05). CONCLUSION: Compared with other endodontic irrigants which usually used in clinic, BioPure MTAD doesn't adversely affect the apical sealing ability of AH plus sealer.

Cloning, expression, and pharmacological activity of BmK AS, an active peptide from scorpion Buthus martensii Karsch.

BmK AS is a beta long-chain scorpion peptide from the venom of Buthus martensii Karsch (BmK). It was efficiently expressed as a soluble and functional peptide in Escherichia coli, and purified by metal chelating chromatography. About 4.2 mg/l purified recombinant BmK AS could be obtained. The recombinant BmK AS maintained a similar analgesic activity to the natural one in both the mouse-twisting test and hot-plate procedure. It also exhibited antimicrobial activity against both Gram-positive and Gram-negative bacteria. BmK AS is the first long-chain scorpion peptide reported to have antimicrobial activity, and is a valuable molecular scaffold for pharmacological research.