To investigate whether masticatory fatigue affects the fracture resistance and pattern of lower premolars restored with quartz-fiber post-core and full crown, 44 single rooted lower premolars recently extracted from orthodontic patients were divided into two groups of 22 each. The crowns of all teeth were removed and endodontically treated and then restored with quartz-fiber post-core and full crown. Twenty-two teeth in one group were selected randomly and circularly loaded at 45° to the long axis of the teeth of 127.4 N at a 6 Hz frequency, and the other group was not delivered to cyclic loading and considered as control. Subsequently, all teeth in two groups were continually loaded to fail at 45° to the long axis of the teeth at a crosshead speed of 1 mm⋅min(-1). The mean destructive force values were (733.88±254.99) and (869.14±280.26) N for the experimental and the control group, respectively, and no statistically significant differences were found between two groups (P>0.05). Bevel fracture and horizontal fracture in the neck of root were the major fracture mode of the specimens. Under the circumstances of this study, it seems that cyclic loading does not affect the fracture strength and pattern of the quartz-fiber post-core-crown complex.
Acid Etching, Dental ; methods ; Adult ; Bicuspid ; Bite Force ; Chromium Alloys ; chemistry ; Crowns ; Dental Prosthesis Design ; Dental Restoration Failure ; Dental Stress Analysis ; instrumentation ; Humans ; Materials Testing ; Methacrylates ; chemistry ; Phosphoric Acids ; chemistry ; Post and Core Technique ; instrumentation ; Quartz ; chemistry ; Resin Cements ; chemistry ; Stress, Mechanical ; Tooth Fractures ; physiopathology ; Tooth Root ; injuries ; Tooth, Nonvital ; rehabilitation

BACKGROUND: The stress distribution is different between implants and natural teeth, and the biomechanical characters of implant-natural tooth supported fixed partial dentures need to be explored.OBJECTIVE: To analyze the distributions of stress and strain on the implant interface and natural tooth ligaments by loading a vertical force to a single implant crown, natural tooth crown and a implant-natural tooth supported fixed partial denture.METHODS: Two male healthy Beagle dogs were selected, and their right mandibular first molars were exacted under general anesthesia. Three months later, a 3.3 mm×10 mm RN ITI implant was implanted into the defect region of each dog. The dogs were killed under anesthesia after another 3 months to remove the mandible. One dog was restored by a single implant and natural tooth crown, and the other was restored by the implant-natural tooth supported fixed partial dentures. The specimens were fixed to the load device after embedded with self caring acrylic resin, and the strain gauges were pasted to the cortical bone around the implant and natural tooth neck. The vertical force was loaded to the implant, natural tooth and fixed denture with 40, 60, 80,120, and 160 N.RESULTS AND CONCLUSION: When the force was loaded to the implant of combined denture, the implant stress of combined denture was less than that of the single implant repair, and partial force was loaded on natural teeth; when the force was loaded to the natural tooth of combined denture, the stress to the natural tooth of combined denture was less than that of the single natural tooth repair. When the force was loaded to the natural tooth of combined denture, the stress was assumed by the whole prostheses. However, the stress was almost assumed by the implant when the force was loaded to the implant of combined denture. That is to say, it is feasible to use the implant-natural tooth supported fixed partial dentures.

OBJECTIVE: To investigate the expression level of miR-181b in CD19+ B lymphocytes of patients with chronic lymphocytic leukemia (CLL), to analyze the relationship between its expression and the prognosis of CLL patients, and to predict the potential target gene of miR-181b in CLL by using bioinformatics. METHODS: Eight-four patients with CLL treated in People's Hospital of Xinjiang Uygur Autonomous Region from June 2013 to June 2018 were selected. and 20 healthy people were selected as control group. RNA was extracted from CD19+B lymphocytes of peripheral blood by magnetic bead sorting, the expression level of miR-181b was detected, and it's expression differences in different IPI groups were analyzed. The correlation between the expression level of miR-181b and PFS of CLL patients also was analyzed. miR-181b target genes were predicted by online database and literatures, and gene annotation analysis and relevant signal pathway analysis were performed for candidate target genes. RESULTS: The expression level of miR-181b in CLL patients was significantly lower than that in control group (P＜0.01); The expression level of miR-181b in the low-risk group was higher than that in high-risk group and extremely high-risk group (P＜0.05), but there was no statistical difference between low-risk group and medium-risk group (P=1.00). The expression level of miR-181b in medium-risk group was higher than that in high-risk group and extremely high-risk group (P＜0.05), but there was no difference between high-risk group and extremely high-risk group (P=1.00). ROC curve results showed that the area under the curve (AUC) was 0.792 (P＜0.01).When the expression level of miR-181b was at the threshold value of 0.279, it showed a better sensitivity (62.9%) and specificity (91.8%). Survival analysis results suggested that compared with the high expression group, the miR-181b low expression group had poor PFS (log rank: P=0.047). Prediction of miR-181b by using the starBase, targetscan and picTar database and its combination with literature reports indicated that CARD11, ZFP36L1, RUNX1, NR4A3, ATP1B1, PUM1 and PLAG1 related with blood diseases, and up-regulated CARD11 and ZFP36L1 participated in lymphoid tumor formation by promoting cell proliferation and inhibiting cell aging. CONCLUSION The expression level of miR-181b in CLL group are significantly lower than that in the controls group, and the low expression of miR-181b relates with poor prognosis of CLL patients. Through bioinformatics prediction and combined with literature reports, it is speculated that CARD11 and ZFP36L1 as target genes of miR-181b may be participated in the occurrence and development of CLL. Further experiments are needed to verify this result.
Apoptosis Regulatory Proteins ; Cell Proliferation ; Humans ; Leukemia, Lymphocytic, Chronic, B-Cell ; genetics ; MicroRNAs ; Prognosis