Effect of different dynamic mechanical strain on the proliferation and synthetic function of human periodontal ligament fibroblasts in vitro / 南方医科大学学报

<p><b>OBJECTIVE</b>To study the changes in the proliferation and synthetic function of human periodontal ligament fibroblasts (HPDLF) in response to dynamic mechanical strains of different modes, magnitudes and durations.</p><p><b>METHODS</b>Using a 4-point bending system, the effect of dynamic mechanical strains of different modes, magnitudes and durations on the proliferation of HPDLF was investigated by analyzing the cell cycle changes with flow cytometry (FCM), and the total protein level and the activity of alkaline phosphatase (ALP) in HPDLF were assayed by quantitative analysis.</p><p><b>RESULTS</b>The percentage of G(0)/G(1) cell decreased, S phase cells increased, and the proliferation index (PI), total protein level and activity of ALP were augmented significantly in response to dynamic mechanical micro-strains. These changes showed close correlations to the magnitude and duration of the strain. The mode of strain caused significant changes in G(0)/G(1), S, and G(2)/M phase cell percentages as well as the PI, total protein level and ALP activity of the cells. In the gradient strain group, the cell proliferation activity, total protein level and ALP activity were obviously higher than those in 1000 and 4000 microstrain groups.</p><p><b>CONCLUSION</b>The changes in the proliferation and synthetic function of HPDLF are closely correlated to the mode, magnitude and duration of the strains.</p>

Osteoblastic early attachment onto the surface of bioadhesive peptide modified pure titanium / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the long-term integrity and the biological function of interface between the bioadhesive peptide modified implant surface and peri-implant tissue.</p><p><b>METHODS</b>A short bioadhesive peptide containing Glycine-Tyrosine-Arginine-Glycine-Asparticacid-Serine (GYRGDS) sequence was immobilized onto the titanium implant surface by means of sol-gel coating technique and self-assembled monolayers (SAM). The chemical composition and organic functional groups on the titanium surfaces were characterized using XPS (X-ray photoelectron spectroscopy) and FTIR (Fourier transform infrared spectrometer). The adhesive strength and stability of osteoblasts on various implant surfaces were compared under flow condition.</p><p><b>RESULTS</b>The results showed that alkali/hot water aging treatment could apparently improve the content of -OH functional groups of titanium surface. The chemical reactive Ti-O-Ti bonding at the surface of titanium played a vital role in inducing the formation of organosilane SAM. GYRGDS peptide can be covalently grafted onto the surface of titanium by SAM technique. The resistance of freshly adherent osteoblasts to detachment by flow was shear time dependent. When the four groups were compared under the same flow stress condition (2.05 Pa) at three specific time spans (30 min, 1 h, 2 h), the cells retention rates in GYRGDS-grafted groups were 93.0%, 54.4%, 34.4% respectively and were much higher than those in non-coated groups.</p><p><b>CONCLUSIONS</b>It was suggested that GYRGDS might have positive effects on maintaining stability and adherence of cells onto the substrates under flow condition.</p>

Experimental study on the reconstruction of mandibular defects with sinboneHT bone replacement in rabbits / 华西口腔医学杂志

<p><b>OBJECTIVE</b>After sinboneHT bone replacement (SBR) was implanted in animals, to evaluate the biocompatibility of SBR and compounded in autogenetic bone in the proportion of one to one in order to prepare for the clinical applications in the future.</p><p><b>METHODS</b>Bone defects of 10 mm x l0 mm x 2 mm was made at the mandibular of rabbits, then SBR with different granule diameter and autogenetic bone was compounded in the proportion of being applied in the left defects, while autogenetic bone was implanted in the right defects and nothing was used in the right reformed defects. Animals were sacrificed at 2, 4 and 8 weeks respectively. The biologic capacity was evaluated with anatomy, X-rays studies and histology.</p><p><b>RESULTS</b>SBR has better biocompatibility, which can effectively accelerate the reconstruction of bone defects and help the new bone by being compounded with autogenetic bone. It provides the appropriate scaffold or template which would allow cellular infiltration, attachment and multiplication.</p><p><b>CONCLUSION</b>SBR is a kind of bone substitute material with good biocompatibility. SBR compounded with self-bone has a better regeneration function.</p>

Influence of multiple sintering on wear behavior of Cercon veneering ceramic / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the influence of multiple sintering on wear behavior of Cercon veneering ceramic.</p><p><b>METHODS</b>Samples were fabricated according to the manufacture's requirement for different sintering times (1, 3, 5, 7 times). The wear test was operated with a modified MM-200 friction and wear machine in vitro. The wear scars were characterized by scanning electron microscope (SEM) and atomic force microscopy (AFM).</p><p><b>RESULTS</b>With the sintering times increasing, the wear scar width became larger. The correlation was significant at the 0.01 level. Significant difference was observed in wear scar width among different samples (P < 0.05). SEM and AFM results showed that veneering ceramic wear facets demonstrated grooves characteristic of abrasive wear.</p><p><b>CONCLUSION</b>Multiple sintering can decrease the wear ability of Cercon veneer, and the wear pattern has the tendency to severe wear.</p>

Regulation of collagen type I and fibronectin mRNA expression by mechanical stress in cultured human periodontal ligament fibroblasts / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effect of different dynamic tensional and compressive stress on the mRNA expression of collagen type I and fibronectin in cultured human periodontal ligament fibroblasts (hPDLF), and explore the regularity of functional change in hPDLF.</p><p><b>METHODS</b>A new cyclic strain loading apparatus was used for mechanically loading. Cells cultured in vitro were loaded with three levels (1000 microstrain, 2000 microstrain, 4000 microstrain) of tensional and compressive forces and collected at different time (0 h, 0.5 h, 1 h, 4 h, 8 h,12 h) course after strain loading. The quantity of collagen type I and fibronectin mRNA was analyzed by means of quantitative real-time PCR with special primers of up- and down-regulated genes. Data were analyzed using SPSS version 10.0 software.</p><p><b>RESULTS</b>Different magnitude and different kinds of mechanical forces as well as the force application time significantly changed the expression of collagen type I and fibronectin mRNA in hPDLF.</p><p><b>CONCLUSIONS</b>Dynamic mechanical forces could regulate the expression of collagen type I and fibronectin mRNA in hPDLF. Collagen type I and fibronectin participated in the mechanical signal transduction in human periodontal ligament fibroblasts.</p>

Regulation of integrin beta1 mRNA expression by mechanical stress in human periodontal ligament fibroblasts / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effect of different kinds of mechanical stress on the mRNA expression of integrin beta1 subunit in cultured human periodontal ligament fibroblasts (hPDLF).</p><p><b>METHODS</b>To scalp and remove the periodontal ligament attached to the mid-third part of the fresh root of young premolars extracted for the cause of orthodontics. Cultured hPDLF by the method of digesting by I-type collagenase combining with tissue adhering. Then hPDLF was isolated and purified by cells passage. The sixth passage's cells were selected to be loaded. A new cyclic strain loading apparatus. Forcel four point bending device was used for mechanically loading. Cells were loaded by three levels (1000, 2000, 4000 microstrain) of tensional and compressive forces and collected at different times (0, 0.5, 1, 4, 8, 12 h) course after strain loading. The quantity of integrin beta1 mRNA in every group was analyzed by means of quantitative real-time PCR with the special primers of up- and down-regulated genes.</p><p><b>RESULTS</b>Dynamic mechanical forces down-regulated the expression of integrin beta1 subunit mRNA in hPDLF and the difference in groups by different magnitude, different kinds, and different time of mechanical forces loading were statistically significant. The stronger stimulated forces, the more down-regulated expression. Compression down-regulated the expression of integrin beta1 subunit mRNA more than tension did.</p><p><b>CONCLUSION</b>Dynamic mechanical forces could regulate the expression of integrin beta1 subunit mRNA. The difference among all the groups by different magnitudes, different kinds, and different time of mechanical forces loading were statistically significant.</p>

Effect of simulating static magnetic field of magnetic attachment on osteoblastic morphology and surface ultrastructure / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate effects of the static magnetic field (SMF) generated by dental magnetic attachment on osteoblastic morphology and surface ultrastructure.</p><p><b>METHODS</b>The in vitro cultured rat osteoblasts were exposed continuously to 12.5 mT, 125 mT, and 250 mT static magnetic fields for 1, 3, 5, and 7 days. After exposed in SMF, osteoblasts were observed under a phase contrast microscope, and then HE stained and observed under a light microscope. In addition, the cells were observed under a scanning electron microscope (SEM).</p><p><b>RESULTS</b>By continuous exposure, the different intensities of SMF exposure did not change the vital osteoblast growth pattern or distribution. The SEM photos showed that there were certain changes in cellular microstructures for osteoblasts after exposed to 12.5 mT for 5 to 7 days, as well as 125 mT and 250 mT for 3 to 7 days. The more exposure time increased, the more microvesicles on the surfaces of cells were observed.</p><p><b>CONCLUSIONS</b>Continuous SMF-stimulation could not affect the shape, distribution, and growth pattern of osteoblasts. The SMF of magnetic attachments could lead to certain changes in surface ultrastructures of osteoblasts in this study.</p>

Influence of manufacture technique on translucency and color of dental porcelain / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To study the influence of manufacture technique on the translucency and color of dental porcelain.</p><p><b>METHODS</b>Specimens were made of VITA VMK 95 dentin porcelain and enamel porcelain and divided into 3 groups: Sintering times group (1, 2, 4, 6, 8 and 10 times), sintering temperature group (910, 920, 930, 940 and 950 degrees C), sintering vacuum group (95, 65, 35 and 0 kPa). Transmittance, Y, dominant wavelength and saturation were measured by PR-650 spectra scan spectrocolorimeter.</p><p><b>RESULTS</b>Transmittance of dentin porcelain increased after 6 times repeated sintering. Transmittance of enamel porcelain increased first after the second sintering, and then became decreasing when sintering more than 2 times. Transmittance of enamel porcelain deceased when sintering temperature was lower than standard. Decrease of sintering vacuum caused the transmittance of dentin and enamel porcelain decreased. The changing of value was coordinated with transmittance. Dominant wavelength and saturation had negative correlation with sintering times and temperature, and positive correlation with vacuum.</p><p><b>CONCLUSION</b>Sintering times, temperature and vacuum all had prominent effects on the translucency and color of dental porcelain. Comparing with dentin porcelain, enamel porcelain was more sensitive with the modification of manufacture technique.</p>

Study of biologic effects of simulating static magnetic field of magnetic attachment on human periodontal ligament fibroblasts / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the biologic effects of simulating static magnetic field of magnetic attachment on human periodontal ligament fibroblasts (HPDLF).</p><p><b>METHODS</b>HPDLF were cultured in vitro and exposed to simulating static magnetic fields of magnetic attachments for 4 days with magnetic flux density of 12.5, 125 and 250 mT respectively, while the control group free of additional static magnetic field was also set up. The activities of cellular alkaline phosphatase (ALP) and superoxide dismutase (SOD) were measured with a spectrophotometer, and cell cycle was analyzed by flow cytometry.</p><p><b>RESULTS</b>An increase were detected, induced by 250 mT static magnetic field exposure for 4 days in terms of activity of ALP in HPDLF, as compared with the control group (P < 0.05). However, no corresponding effects were found in activity measurements of SOD (P > 0.05). Also there were no statistical differences observed on cell cycle distribution (P > 0.05) or cell proliferation index (P > 0.05) under such static magnetic fields.</p><p><b>CONCLUSION</b>The static magnetic fields of magnetic attachment used in this study have improved the activity of ALP, and do little inference to the activity of SOD and the cell cycle distribution.</p>

Wear behavior of enamel and veneering ceramics / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To compare the wear between the enamel and two types of dental decoration porcelains for all-ceramic restorations (Vita-alpha, Vintage AL).</p><p><b>METHODS</b>Friction coefficients, wear scar width, element concentrations and wear surface evolution were considered relatively to the tribology of that in vivo situation. The wear scars of the samples were characterized by means of dynamic atomic force microscopy (DFM). The different element concentrations of the surface before/after the wear test were determined with energy dispersion spectrometry (EDS).</p><p><b>RESULTS</b>The friction coefficient varied from time in each kind of material. The statistical differences between materials were observed in wear scar width and properties of materials (P<0.05). DFM results showed wear surface of natural tooth full of abrasive particles and denaturation of dental texture. Wear surface of veneering ceramics consisted mainly of abrasive particles, plough and microcracking. EDS results showed that the element concentration of Fe was obviously found on the samples after wear.</p><p><b>CONCLUSION</b>The main underlying mechanisms of natural teeth wear are abrasive, and denaturation of dental texture. Abrasive wear, adhesion and fatigue of veneering ceramics characterize the wear patterns which plays different role in Vita-alpha and Vintage AL. The wear patterns of veneering ceramics can be described as mild wear.</p>

Effects of simulating static magnetic fields of magnetic attachments on osteoblasts proliferation, cell cycle distribution and apoptosis ratio / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effects of the static magnetic field (SMF) generated by dental magnetic attachments on osteoblastic proliferations, cell cycle distribution, and apoptosis ratio.</p><p><b>METHODS</b>By simulating those of the closed-field, the closure process and the open-field Magnedisc 800 magnetic attachments respectively, the in vitro cultured rat osteoblasts were exposed continuously to 12.5, 125, 250 mT SMF. The effects of the SMF on the proliferation of the cells were examined. MTT colorimetry test was performed to detect the effect of the SMF on the vitalities of cells. Flow cytometry was utilized to analyze the cell cycles and cell apoptosis rates.</p><p><b>RESULTS</b>The SMF exposure didn't change the vital osteoblasts number, the cell cycle distribution and proliferation activities of osteoblasts. The cell apoptosis situation were not observed statistical differences.</p><p><b>CONCLUSION</b>No matter the closed-field, the closure process and the open-field magnetic attachments respectively, continuous simulating SMF-stimulation of magnetic attachments couldn't change osteoblasts proliferation activity, cell cycle distribution, and apoptosis ratio.</p>

Study on color matching of equal volume in dental ceramic prothesis materials / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To study the color changes on brightness and hue in dental ceramic prothesis materials.</p><p><b>METHODS</b>The different color mark of VINTAGE series was sintered on 15 pieces Ni-Cr alloy denture materials. The sample group and control group was given the sintering of color blending with equivalent volume. The order of color mark was of A1 and A2, A2 and A3, A3 and A4, B1 and B2, B2 and B3, B3 and B4 in sample group, and A1, A2, A3, A3.5, A4, B1, B2, B3 and B4 orderly in control group. The chromatic analysis on samples of VITA had been taken through applying PR 650 spectrum detector and adopted the statistic software of Photo Research and SPSS 12.0 for analysis.</p><p><b>RESULTS</b>The statistical difference (P<0.05) of L*a*b* value was found in the different color mark of the same color serials. A non-linearity relation had been found in the chromatic parameters a*b*. It means the change of color was visible.</p><p><b>CONCLUSION</b>Set A has a bigger grading change of brightness than Set B. The change of red-green is obviously in Set A, as well as yellow-blue in Set B.</p>

Effect of vacuum deposition technology on the metal-porcelain bond strength of a new type of CO-CR ceramic and framework dental alloy / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effect of a new engineering technique of vacuum deposition-plasma magnetron reactive sputter deposition technique on the metal-porcelain bond strength of a new type of Co-Cr ceramic and framework dental alloy.</p><p><b>METHODS</b>Before porcelain painted on the specimens, the standardized metal strips made from DA9-4 dental alloy were coated with a thin Al2O3 ceramic film by plasma magnetron reactive sputter deposition technique. The conformation, structure and thickness of the ceramic film were analyzed. The specimens for three-point bending test made from DA9-4 alloy and VMK95 porcelain were used for metal-porcelain bond strength measurement, in the same time the interface of metal-porcelain and element distribution were also observed.</p><p><b>RESULTS</b>The flexural bonding strength of metal-porcelain of sputtering group and control group were (180.55+/-16.45) MPa and (143.80+/-24.49) MPa. The flexural bonding strength of metal-porcelain of sputtering group was higher than control group significantly through statistical analysis (P<0.01).</p><p><b>CONCLUSION</b>The plasma magnetron reactive sputter deposition technique has a positive effect in improving the bonding strength of DA9-4 dental alloy and ceramic.</p>

Clinical application of implant-supported restoration with all-ceramic crown fused to small-size titanium abutment / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To get aesthetic implant-supported restorations by means of the all-ceramic crown fused to small-size titanium abutment and evaluate the quality of the restorations.</p><p><b>METHODS</b>A small-size titanium abutment that had extremely thin circumferential collar and axial wall was fabricated, while a Cercon all-ceramic crown made with computer aided manufacture (CAM). The crown was fused to the abutment by firing the opaque porcelain. A total of 6 restorations in 5 patients were installed and assessed according to the California Dental Association (CDA) quality evaluation system.</p><p><b>RESULTS</b>All the restorations were fabricated well and ranked in clinic evaluation excellent for surface, anatomical form, marginal quality, and color at baseline and one year after insertion, respectively.</p><p><b>CONCLUSIONS</b>The restoration of all-ceramic crown fused to titanium small-size abutment is a new aesthetic alternative for the implant-supported restoration.</p>

Biomechanical study of restorations of medial-occlusal cavities of endodontically treated premolars / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To compare the different restorations of endodontically treated premolars, and to choose the best method.</p><p><b>METHODS</b>10 pairs of symmetry maxillary first premolars were collected from 10 patients, and randomly divided into 2 groups. Every pair received different treatment accordingly. The test group was set up the medial-occlusal cavities model under the same standard. The 10 pairs teeth were test by instron 4302 universal test machine in speed of 1.00 mm/min until broken up and the top load was recorded. The load angle was 45 degree to the long axis of the teeth, as the load was pointed to the middle of the lingual surface on the buccal cusp. The records were analyzed by paired samples t test.</p><p><b>RESULTS</b>Based on the medial-occlusal cavities, the fracture strength of the full crowned teeth was lower than the full natural teeth, and the fracture strength of the post-crowned teeth was higher than the full natural teeth.</p><p><b>CONCLUSION</b>From the point of biomechanics, the different trauma of the endodontically treated teeth fits to different restorations. The medial-occlusion cavities fit the post-crown restoration mostly.</p>

Cyclic fatigue of Vita mark II machinable ceramics under Hertzian's contact / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the cyclic fatigue modes of Vita mark II machinable ceramics under Hertzian's contact.</p><p><b>METHODS</b>Hertzian's contact technique (WC spheres r = 3.18 mm) was used to investigate the cyclic fatigue of Vita mark II machinable ceramic. All specimens were fatigued by cyclic loading in moist environment, furthermore, surviving strength was examined by three point test and morphology damage observation.</p><p><b>RESULTS</b>In homogeneous Vita mark II machinable ceramics, two fatigue damage modes existed after cyclic loading with spheres under moist environment, including conventional tensile-driven cone cracking (brittle mode) and shear-driven microdamage accumulation (quasi-plastic mode). The latter generated radial cracks and deeply penetrating secondary cone crack. Initial strength degradation were caused by the cone cracks, subsequent and much more deleterious loss was caused by radial cracks.</p><p><b>CONCLUSION</b>Cyclic fatigue modes of Vita mark II machinable ceramics includes brittle and quasi-plastic mode.</p>

Comparison of color character of VITA shade guide and the custom shade guide / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To compare the color character of VITA shade guide and the custom shade guide with metal substrate.</p><p><b>METHODS</b>Color of 9 sites of 5 series of VITA shade guides and custom shade guides with metal substrate were measured by means of PR-650 spectrophotometer.</p><p><b>RESULTS</b>The color range of VITA shade guide were that L* was 56.86-73.86, a* was-1.29-3.69, b* was 7.09-21.94, and the transparence was 3.20-7.59. The color range of the custom shade guide was that L* was 60.59-78.54, a* was -1.09-4.99, b* was 7.60-22.35, and the transparence was 0.23-10.98. L*, a* and b* of the custom shade guide with metal substrate were higher than VITA shade guide, and the transparence was differet. The color difference of homonymy shade tab between custom shade guide and VITA shade guide was larger than 1.5 NBS.</p><p><b>CONCLUSION</b>There is color difference between VITA shade guide and custom shade guide. Metal substrate has effects on the color of cero-metal prosthesis, and color selection in clinic should be carefully considered.</p>

Study on different thickness and chromatics of various opaques / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To study the effect existed in the course of adopting different thickness and chromatics of various opaques so that a good methods can be provided for clinical care in prosthodontics.</p><p><b>METHODS</b>A model of using the thin plastic paper to control the ceramic thickness was applied in this test. The data of chromaticity was measured by TC-PIIG auto color difference meter and its results was processed by computer.</p><p><b>RESULTS</b>The value of brightness had an uptrend increase with augment of opaques thickness. Metal base color was opaqued and the basic hue was set. A lower and unstable value, besides a relative stable Y, was measured with the uncompleted opaquing. A stability of hue had been gradually concentrated within a certain range accompanying with the increase of opaquing ceramic thickness. A concentrated hue in the second thickness was found in CARAT ceramic which had high ability of opaque and had a stable hue of ceramic in comparison with other opaques. Among those changes, CARAT's brightness showed a minimal change; a gradual stability of chromatics was presented and was limited with-in a certain range though the augment of opaques.</p><p><b>CONCLUSION</b>The metal color in base could be completely opaqued while opaques thickness reaches a certain range. CARAT is the materials of minimal thickness and has relatively strong capacity for opaques.</p>

Effect of thickness and shade of porcelain of ceramometal restorations on color of gingival porcelain / 华西口腔医学杂志

<p><b>OBJECTIVE</b>The purpose of this study was to evaluate the color changes of gingival porcelain through varying thickness and shade of porcelain of ceramometal restorations.</p><p><b>METHODS</b>In this study a spectrophotometer (PR-650) was used for color analysis. The color changes of dentin porcelain and gingival porcelain with three varied thickness (0.3 mm, 0.6 mm and 0.9 mm) were investigated. In addition, the color variances of Shofu vintage porcelain shade A2, A3 and B2 were tested.</p><p><b>RESULTS</b>The results showed that decreased L * value of ceramometal restorations and increased a * value were due to the increase of the gingival porcelain thickness, color measurements showed the same trend as the increased dentin porcelain thickness and the opaque and dentin porcelain with different color affected the appearance of gingival porcelain.</p><p><b>CONCLUSION</b>The color of gingival porcelain would be changed with the differences of thickness and shade of porcelain of ceramometal restorations.</p>

Analysis of chromatic value of gingival porcelain / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To study the distribution of the chromatic value of gingival porcelains.</p><p><b>METHODS</b>The color change of Shofu VINTAGE and Vita VMK95 gingival porcelains on the black and white backings was determined with a spectrophotometer (PR-650).</p><p><b>RESULTS</b>The results showed that the chromatic value of gingival porcelains was different on varying backings. The color space of gingival porcelain was L*: 41.85 - 50.64, a*: 12.46 - 19.46, b*: 1.33 - 4.62.</p><p><b>CONCLUSION</b>The chromatic value distribution cannot cover the color region of natural gingiva.</p>