Diagnostic accuracy of cone beam computed tomography with different resolution settings for external root resorption / 北京大学学报(医学版)

OBJECTIVE@#To evaluate the diagnostic accuracy of cone beam computed tomography (CBCT) with different resolution settings in detecting the simulated external root resorption defects.@*METHODS@#External root resorption defects were simulated in 51 human single rooted premolar teeth. Cavities simulating root resorption defects of 1 mm in diameter and 0.1 mm, 0.2 mm, and 0.3 mm in depth were drilled in the cervical, middle and apical thirds of lingual surfaces of the teeth. In addition to the 51 locations as controls, a total of 102 cavities were obtained in the present study. Specimens were placed in a human dry mandible and scanned by ProMax 3D and DCT PRO CBCT with different resolution settings, respectively. The three-dimensional CBCT images were evaluated by two experienced observers. The data were analyzed with receiver operating characteristics (ROC) analysis. ROC curves were generated and the area under ROC curve (Az) was employed to express the diagnostic accuracy.@*RESULTS@#The diagnostic accuracy (Az value) of ProMax 3D CBCT with high, normal and low resolution settings were 0.867, 0.703 and 0.665 (P < 0.05), respectively. Defects with depths of 0.2 mm and 0.3 mm were easier to be detected than those with depths of 0.1 mm (P < 0.05). The images obtained by high resolution mode scanning had obvious advantages in detecting smaller defects (depth 0.1 mm and 0.2 mm). The DCT PRO CBCT provided 4 resolution settings including normal quality + normal resolution, normal quality + high resolution, high quality + normal resolution and high quality + high resolution. The Az values for those 4 resolution settings were 0.527, 0.725, 0.743, and 0.794 (P < 0.05), respectively. Similar to ProMax 3D CBCT, the scanning mode with high resolution played a better role in detecting the defects with depth of 0.1 mm. Except for the scanning setting mode with normal quality + normal resolution, the other three modes could well be evaluated for the defects with depth of 0.2 mm and 0.3 mm.@*CONCLUSION@#It is concluded that the diagnostic ability for external root resorption of CBCT could be affected by resolution settings. Computer-aid imaging method can improve the CBCT diagnostic accuracy for external root resorption without increasing the radiation dose level during CBCT scanning.

Effects of bond strength evaluation on different durations of adult permanent teeth and youth permanent teeth by using universal adhesives to dentin / 华西口腔医学杂志

OBJECTIVE@#To compare the dentin bonding strength evaluation between adult permanent teeth and youth permanent teeth after treatment for different durations by universal adhesives.@*METHODS@#Ten adult permanent teeth and ten youth permanent teeth were selected for this study. The occlusal enamel layer was removed, and each tooth was cut into three pieces along the long axis. In total, 30 pieces of adult and youth teeth were prepared. The adult and youth teeth pieces were randomly divided into three groups and treated by universal adhesives for 10, 20, and 30 s. In this study, Scotchbond Universal (SBU) was selected as the universal adhesive. Slabs were treated by dual-cure resin cements. The specimens were tested by microshear strength test through a universal testing machine. Fracture modes were observed by a stereomicroscope. Other adult teeth and youth teeth were selected, two for each type, and treated and grouped in the same manner. Fluorescein (0.1% Rhodamine B) was dissolved in SBU adhesive, and the specimens were treated by the adhesives for 10, 20, and 30 s. Micromorphology of the resin protrusions on the adhesive surface was observed by laser confocal microscopy (CLSM).@*RESULTS@#For the adult teeth, the highest micro-shear bonding strength was observed in the 20 and 30 s groups, and the values were higher than that of the 10 s group (P0.05). The main break patterns in different groups comprised adhesive failure fractures and several mixed failure fractures. No resin fracture mode was observed. CLSM revealed very few short resin protrusions in 10 s adult teeth group, whereas the number and length of resin protrusions significantly increased in the 20 s adult teeth group. The resin protrusions of the 30 s group were shorter than those of the 20 s adult teeth group. In different durations, the bonding interface in different youth teeth groups presented the same trend of change as the adult teeth. However, the number and length of resin protrusions in the 10 s group of youth teeth were all higher than those of the 10 s adult teeth group.@*CONCLUSIONS@#In clinical practice, the bonding agent treatment duration shall be shortened appropriately for youth permanent teeth, and that for adult permanent teeth shall not be shortened to less than 20 s. On the whole, the bond strength of youth permanent teeth can achieve no significant difference with the adult permanent teeth.

Influence of autoclave sterilization on dimensional stability and detail reproduction of 5 additional silicone impression materials / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the dimensional stability and detail reproduction of five additional silicone impression materials after autoclave sterilization.</p><p><b>METHODS</b>Impressions were made on the ISO 4823 standard mold containing several marking lines, in five kinds of additional silicone. All the impressions were sterilized by high temperature and pressure (135 °C, 212.8 kPa) for 25 min. Linear measurements of pre-sterilization and post-sterilization were made with a measuring microscope. Statistical analysis utilized single-factor analysis with pair-wise comparison of mean values when appropriate. Hypothesis testing was conducted at alpha = 0.05.</p><p><b>RESULTS</b>No significant difference was found between the pre-sterilization and post-sterilization conditions for all locations, and all the absolute valuse of linear rate of change less than 8%. All the sterilization by the autoclave did not affect the surfuce detail reproduction of the 5 impression materials.</p><p><b>CONCLUSIONS</b>The dimensional stability and detail reproduction of the five additional silicone impression materials in the study was unaffected by autoclave sterilization.</p>

Construction of recombinant adenovirus vector of calcitonin gene-related peptide gene and transfection to neonatal rat cardiomyocytes / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To construct a recombinant adenovirus vector of calcitonin gene-related peptide (CGRP) by AdEasy system and to validate its expression in myocardial cells.</p><p><b>METHODS</b>The full-length of CGRP gene cDNA was acquired by RT-PCR and cloned into pShuttle-CMV. After linearization with Pme I, the recombinant plasmid (pShuttle-CMV-CGRP) was transformed into E.coli BJ5183 by electroporation to construct the recombinant adenovirus plasmid AdEasy-pShuttle-CGRP. The recombinant adenovirus plasmids were transformed into E.coli XL10-Gold cells to be amplified. Then the recombinant plasmid was digested with Pac I and transfected to 293 cells to package recombinant adenovirus particles. PCR technique was used to detect target gene. The recombinant adenovirus particles were purified by CsC1 density gradient. The purified recombinant adenovirus was transfected to neonatal rat cardiomyocytes,and the recombinant adenovirus production was observed by fluorescent microscope. Expression of CGRP in hearts 7 days after intravenous delivery of adenoviral vectors AV-CGRP was determined by radioimmunoassay.</p><p><b>RESULT</b>The RT-PCR products confirmed a full-length cDNA of CGRP gene in PUC(57) by sequencing. The corresponding double endonuclease and PCR analysis certified the successful cloning of the gene into the pShuttle-CMV. The recombinant adenovirus plasmid AdEasy-pShuttle-CGRP was digested by Pac I endonuclease to form the typical DNA segments, whose length was about 3 kb and 30 kb. PCR analysis and fluorescent microscope observation confirmed that the CGRP gene was inserted into the adenovirus vector with very strong power of transfection. The recombinant adenovirus particles infected neonatal rat cardiomyocytes successfully. Radioimmunoassay showed that delivery of AV-CGRP significantly increased the expression of CGRP in mice hearts.</p><p><b>CONCLUSION</b>The recombinant adenovirus vector of CGRP gene has been constructed,and it can infect neonatal rat cardiomyocytes successfully. Somatic delivery of CGRP gene can significantly increase the expression of CGRP in mice hearts. The results may provide a sound foundation for further study on the value of CGRP as the target for gene therapy in both laboratory and clinical trials.</p>

Effect of different mixing and curing methods on the mechanical properties of denture base resin / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the differences between the mechanical properties of denture base processed by traditional mixing and malaxation method, and by traditional hot water polymerization and electrical heat-polymerization.</p><p><b>METHODS</b>Samples used in this investigation were commercial acrylic denture base resin made by using two different mixing methods, and by using two different curing methods. The samples were assigned to 4 test groups. Group 1: traditional mixing + hot water polymerization. Group 2: malaxation + hot water polymerization. Group 3: traditional mixing + electrical heat-polymerization. Group 4: malaxation + electrical heat-polymerization. Surface hardness, flexural strength, flexural modulus, and impact strength were tested of each sample.</p><p><b>RESULTS</b>The mean of the four groups' surface hardness was 19.4, 21.2, 22.3, 23.2 N/mm2, and of flexural strength was 58.58, 63.32, 66.73, 63.76 MPa, and of impact strength was 1.42, 1.53, 1.77, 1.78 KJ/m2, and of flexural modulus was 2311.38, 2417.82, 2566.36, 2400.37 MPa.</p><p><b>CONCLUSIONS</b>Surface hardness and impact strength of malaxation method + electrical heat-polymerization group are higher than those of traditional mixing + hot water polymerization group.</p>