Effects of adhesive and primer on the bonding strength of zirconia to resin cement / 华西口腔医学杂志

OBJECTIVE@#This study aimed to compare the effects of water storage treatment and thermal cycling on the shear bond strength (SBS) of three self-adhesive dual-cure resin cements.@*METHODS@#Six cubic zirconia specimens with side length of 2 cm were obtained by cutting and sintering. Three self-adhering dual-cure resin cements (i.e., Clearfil SAC, RelyX U200, and Multilink Speed) were selected. According to their bonding modes, they were divided into three groups: direct bonding group (direct coating with resin cement), adhesive group (applying universal adhesives and then coating with resin cement), and primer group (applying Z-Prime Plus and then coating with resin cement). According to experimental conditions, each group was divided into two subgroups: subgroup a (water storage at 37 ℃ for 24 h) and subgroup b (thermalcycling for 5 000 times). SBS data were analyzed by one-way ANOVA by using SPSS 19.0 software (P0.05). After thermalcycling, the SBS of the three types of resin cements decreased (P<0.05); the SBS of the adhesive group was higher than that of the direct adhesive group and the primer group (P<0.05). Fracture mode analysis revealed that the type Ⅲ fracture mode evidently increased after the thermalcycling treatment compared with the water storage treatment.@*CONCLUSIONS@#The universal adhesives and the primer can improve the SBS of self-adhesive dual-cure resin cement in water storage at 37 ℃ for 24 h. The universal adhesives had a better bonding durability than the zirconia primer.

Effects of copper content on the antibacterial performance and corrosion resistance of CoCrMoCu alloy / 华西口腔医学杂志

<p><b>OBJECTIVE</b>This study aimed to determine the effects of copper content on the corrosion resistance of CoCrMoCu alloy and its in vitro antibacterial performance.</p><p><b>METHODS</b>CoCrMoCu specimens with different Cu contents (2%, 3%, 5%, and 7%) were prepared by vacuum melting method. CoCrMo without Cu served as control. The corrosion resistance of the specimens was measured by electrochemistry. The antibacterial effects of the specimens on Staphylococcus aureus and Escherichia coli were analyzed by coating-film method.</p><p><b>RESULTS</b>Compared with CoCrMo without Cu, the addition of 2%-5% Cu to CoCrMo improved the pitting and uniform corrosion of CoCrMo alloy and decreased the corrosion current density. The antibacterial performance of CoCrMoCu alloy increased with increased Cu content. The antibacterial rate of alloy was 99% when Cu content exceeded 5%.</p><p><b>CONCLUSIONS</b>Cu addition had a statistically significant influence on the corrosion resistance and antibacterial performance of CoCrMoCu. CoCrMoCu has better corrosion resistance and antibacterial performance when Cu content is 5%.</p>

Metal-ceramic bond strength of Co-Cr alloy processed by selective laser melting / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the metal-ceramic bond strength of a selective laser melting Co-Cr alloy.</p><p><b>METHODS</b>Twelve Co-Cr metal bars were prepared according to the ISO 9693 standard with Vita porcelain fused onto the centre of each bar. Then the sample bars were divided into two groups of six each. The control group was made by traditional cast process (cast group), and the experimental group was processed by selective laser melting (SLM) technology (SLM group). Metal-ceramic bonding strength and fracture mode were assessed using three-point bending test. Fracture mode analysis was determined by scanning electronic microscope/energy dispersive spectroscopy. Student's t-test was used to analyze the data in SPSS 13.0.</p><p><b>RESULTS</b>The metal-ceramic bond strength value of the cast group was (33.45 ± 2.34) MPa, and that of the SLM group was (31.62 ± 2.34) MPa (t = 0.79, P > 0.05). A mixed fracture mode on the debonding interface of all specimens was observed, while little porcelain was reserved.</p><p><b>CONCLUSIONS</b>The metal-ceramic system processed by SLM exhibited a bonding strength that satisfies the requirement of clinical application.</p>

Clinical research on curative effect of complete denture with two kinds of occlusion for temporomandibular joint disorders of aged edentulous patients / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To compare curative effect between complete denture with lingualized occlusion and anatomic occlusion on temporomandibular joint disorders (TMD) of aged edentulous patients with severe residual alveolar ridge resorption.</p><p><b>METHODS</b>Seventy aged edentulous patients with severe residual alveolar ridge resorption were recruited in this study and randomly assigned into two groups, thirty-five each. In Group A, patients received complete denture with lingualized occlusion, and in Group B, patients received complete denture with anatomic occlusion. The condition of TMD was examined and recorded by the same TMD specialist at baseline, 3 months and 6 months following denture delivery. The recovery effect of TMD was evaluated according to Fricton Index. Related data were analyzed statistically with t-test and rank sum test.</p><p><b>RESULTS</b>Three months following denture delivery, the craniomandibular index (CMI) decrease value was (0.064 ± 0.022) in group A, and was significantly higher than that in group B (0.043 ± 0.018) (P < 0.01). Six months following denture delivery, the CMI decrease value was (0.084 ± 0.020) in group A, and was significantly higher than that in group B (0.070 ± 0.021) (P = 0.011<0.05).</p><p><b>CONCLUSIONS</b>Complete denture with lingualized occlusion may be more conducive to the remission of TMD for aged edentulous patients with severe residual alveolar ridge resorption.</p>

Comparison of color reappearance between metal-ceram restoration and foundry-ceram restoration using crystaleye spectrophotometer / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To study the color reappearance effect of metal-ceram restoration and foundry-ceram restoration using Crystaleye spectrophotometer.</p><p><b>METHODS</b>58 metal-ceram restorations and 58 foundry-ceram restorations according to the result of the Crystaleye spectrophotometer were made respectively. The deltaE between restorations and natural teeth as referenced were analyzed. And satisfaction of dentists and patients were evaluated.</p><p><b>RESULTS</b>The deltaE between metal-ceram restorations and natural teeth was 7.13 +/- 0.74. The deltaE between foundry-ceram restorations and teeth was 1.47 +/- 0.84. There were statistical differences between the deltaE (P < 0.01). The satisnatural faction of dentists and patients to the foundry-ceram restorations were higher than to the metal-ceram restorations (P < 0.05).</p><p><b>CONCLUSION</b>Crystaleye spectrophotometer can provide accurate reference for foundry-ceram restoration, but for metal-ceram restoration it is not accurate.</p>

Effects of different dental alloys on cytotoxic and apoptosis related genes expression of mouse fibroblast cells L929 / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate effects of the leaching liquids of 5 different kinds of dental alloys on L929 cells at cell level and molecular level.</p><p><b>METHODS</b>The fibroblast L929 cells of mouse were cultivated in vitro in leaching liquids of 5 different kinds of dental alloys, Au alloy (n = 8), Ag-Pt alloy (n = 8), Co-Cr alloy (n = 8), Ni-Cr alloy (n = 8), and Cu alloy (n = 8). The RPMI 1640 cell medium containing 10% fetal beef serum was used as control. The cytotoxicities of the 5 dental alloys were evaluated by means of methyl thiazolyl tetrazolium (MTT), and the effects of these alloys on the expression of caspase-3, caspase-8, and caspase-9 mRNA of L929 cells were examined using reverse transcription polymerase chain reaction (RT-PCR) method.</p><p><b>RESULTS</b>After 48 hours culture the cytotoxicity of Cu alloy group was in Grade 4 and those of the other groups were all in Grade 0. The mRNA levels of caspase-8 had no change in all groups (P > 0.05). The mRNA levels of caspase-3 were as follows: Cu alloy (0.474 +/- 0.001), the negative control (0.527 +/- 0.003), Au alloy (0.528 +/- 0.013), Co-Cr alloy (0.615 +/- 0.007), Ag-Pd alloy (0.673 +/- 0.009), and Ni-Cr alloy (0.803 +/- 0.037). The mRNA levels of caspase-9 were as follows: Cu alloy (0.532 +/- 0.041), Au alloy (0.574 +/- 0.013), the negative control (0.578 +/- 0.010), Co-Cr alloy (0.617 +/- 0.009), Ag-Pd alloy (0.703 +/- 0.018), and Ni-Cr alloy (0.811 +/- 0.037). There were significant differences between the groups except the negative control group and Au alloy group.</p><p><b>CONCLUSIONS</b>The Cu alloy shows the highest cytotoxicity, and the leaching liquids of 5 different kinds of dental alloys may induce cell apoptosis through mitochondrion pathway.</p>

Laser surface modification of medical titanium / 华西口腔医学杂志

<p><b>OBJECTIVE</b>Titanium, by far one of the oldest materials in medical implants used for hard tissue replacement and rehabilitation, was used widely as implant material. The objective of the present study was to fabricate the TiN modified layer on the surface of medical pure titanium and improve its surface properties. Thus the wear resistance, biocompatibility and antisepsis were improved.</p><p><b>METHODS</b>A continuous-wave 2 kW Nd: YAG laser was used to irradiate the sample in the environment of N2 with concentration of 99.995%. Titanium nitride surface coatings had been extensively used as corrosion resistant and biocompatible layers on titanium and its alloys. The microstructure and composition of the laser nitrided coating were studied by scanning electron microscopy and X-ray diffraction. Microhardness of the modified sample was also analyzed by micro-hardmeter.</p><p><b>RESULTS</b>TiN modified layer with the thickness of about 400 microm was obtained. TiN distributed gradually from surface to the substrate. There was a good metallurgical bonding between the nitrided layer and the substrate. The hardness of the modified layer was reduced from the surface to the inside.</p><p><b>CONCLUSION</b>With optimum process parameters, a compact laser modified gradient coating reinforced with fine TiN was achieved on the surface of medical titanium.</p>

Differential study of the bonding characterization of dental porcelain to Ni-Cr alloys / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To study the bonding capability when Ni-Cr porcelain alloy was added with Ti, compound rare earth metals and removed the element of Be.</p><p><b>METHODS</b>Ni-Cr-Ti porcelain alloys manufactured by Institute of Metal Research of Chinese Academy of Sciences were tested. The test alloys were divided into three groups according to whether containing Be and compound rare earth metals or not. And HI BOND Ni-Cr base-metal alloy was chosen as control. The metal-ceramic specimens were prepared for shear test, scanning electron microscope (SEM) and energy spectrum analysis.</p><p><b>RESULTS</b>The shear bond strength of the four groups were analyzed. No significant difference were observed among them (P > 0.05). No crackle was found and they were contacted tightly between the porcelain and metal. The composition and contents of the four groups' interfaces were closed.</p><p><b>CONCLUSION</b>The shear bond strength of the self-made Ni-Cr-Ti porcelain alloys all can satisfy the clinical requirements. Experimental groups containing Ti, compound rare earth metals and removing the element of Be can be used as better recommendation for clinical practice.</p>

Application of the laser welding to preventing the break of the base plate caused by the increase of magnetic attachments / 华西口腔医学杂志

<p><b>OBJECTIVE</b>This study was intended to design a kind of resisting part dint of device in order to preventing the base plate break while being subjected to the dint when partial base plate dint concentrates because of the increase of the magnetic attachment to the original movable artificial teeth.</p><p><b>METHODS</b>Ten patients who should increase magnetic attachment was adopted in the study, and we increased a kind of new designed partial cast base plate on the original base plate using laser welding technique, then designed magnetic attachment and artificial teeth.</p><p><b>RESULTS</b>None of ten sufferers appeared the phenomenon of the break of the base plate.</p><p><b>CONCLUSION</b>The application of the laser welding technique can prevent the break of the base plate when partial dint increase because of the increase of the magnetic attachments.</p>