Biodegradation and abrasive wear of nano restorative materials

The purpose of this study was to evaluate the biomechanical degradation of two nanofilled restorative materials (a resin-modified glass ionomer, Ketac N100 and a composite, Filtek Z350), compared with conventional materials (Vitremer and TPH Spectrum). Twenty specimens obtained from each material were divided into two storage groups (n=10): relative humidity (control) and Streptococcus mutans biofilm (biodegradation). After 7 days of storage, roughness values (Ra) and micrographs by scanning electron microscopy (SEM) were obtained. In a second experimental phase, the specimens previously subjected to biodegradation were fixed to the tooth-brushing device and abraded via toothbrushes, using dentifrice slurry (mechanical degradation). Next, these specimens were washed, dried, and reassessed by roughness and SEM. The data were submitted to repeated measures three-way analysis of variance (ANOVA) and Tukey tests (p<0.05). There was statistically significant interaction among factors: material, storage (humidity/biofilm), and abrasion (before/after). After biodegradation (S mutans biofilm storage), Ketac N100 presented the highest Ra values. Concerning bio plus mechanical challenge, TPH Spectrum, Ketac N100, and Vitremer presented the undesirable roughening of their surfaces, while the nano composite Filtek Z350 exhibited the best resistance to cumulative challenges proposed. The degraded aspect after biodegradation and the exposure of fillers after mechanical degradation were visualized in micrographs. This study demonstrated that the nanotechnology incorporated in restorative materials, as in composite resin and resin-modified glass ionomer, was important for the superior resistance to biomechanical degradation.     

Effect of food-simulating liquids on the mechanical properties of provisional restorative materials

OBJECTIVES: The purpose of this study was to investigate the effects of food-simulating liquids (FSL) on the mechanical properties of provisional restorative materials. METHODS: Four provisional restorative materials were selected: (1) Dentalon Plus (DP), (2) Protemp II (PII), (3) Systemp C&B (SCB) and (4) Integrity (INTG). The specimens were fabricated in customized molds and each type was randomly divided into five groups (n = 10). The test groups were conditioned for 7 days at 37 degrees C as follows: water, 0.02 N citric acid, heptane and 75% ethanol in aqueous solution. Specimens in the control group were stored at room temperature in air. After conditioning, the flexural strength (FS) values were assessed using a universal testing machine (5 mm/min crosshead speed) and the fractured specimens were used for the determination of the Knoop hardness number (KHN) using a digital micro-hardness tester (100 gf/15 s). Kruskal-Wallis and Mann-Whitney U-tests were used for statistical analysis. RESULTS: In ethanol and heptane solutions, DP specimens were totally degraded, thus, FS/KHN for DP could not be measured. For all materials, the FS/KHN values were significantly lower than their control groups after conditioning in ethanol. After heptane conditioning, the decrease in FS for SCB and KHN for PII were statistically significant. After citric acid conditioning, KHN for PII and INTG were significantly higher than the controls and the decrease in FS for SCB and INTG were statistically significant. SIGNIFICANCE: The mechanical properties of provisional restorative materials are strongly influenced by food-simulating liquids.     

Interaction between GIC and S. sanguis biofilms: antibacterial properties and changes of surface hardness

Objective

The aim of this study was to investigate the interaction of Streptococcus sanguis with two glass-ionomer formulations (GIC:A containing fluoride and GIC:B without fluoride) with particular reference to bacterial growth and changes in hardness of the cement with respect to time.

Materials and methods

Discs of two water activated glass-ionomer cements were prepared according to the manufacturer's instruction. Hydroxyapatite discs (HA) were used as controls. 3D laser scanning technique was used to characterize surface roughness and area of the substrate prior to growing biofilms. Surface hardness was evaluated before and after biofilm growth. A constant depth film fermenter system (CDFF) was used to grow S. sanguis biofilms on the specimens in a similar manner to that described previously by Wilson et al. in 1995. For susceptibility measurement, specimens were removed from CDFF aseptically over periods up to 14 d after the first colonization with bacteria. Counts of viable bacterial in the accumulating biofilm layer on each surface were measured and converted to colony forming units per unit surface area. To determine the effect of storage media, hardness discs were exposed to distilled water, lactic acid pH 4, lactic acid pH 5, citric acid pH 5, artificial saliva and S. sanguis biofilms. Twenty-four hours after preparing and subsequent autoclaving, specimens were transferred to a vessel containing 40 ml storage medium. The specimens were investigated for periods up to 7 d.

Results

The viable counts of S. sanguis per mm² on GIC:A were significantly less than those on HA and GIC:B during the first 5 d (p < 0.05). The viable counts of bacteria on the surface of GIC:B were lower during the initial 5 d when compared to HA. Exposure of GIC:A and GIC:B to different medium produced softening to the surface of cement. It is apparent that the effects of the biofilms are significantly greater than storage in water but similar to storage in lactic acid pH 5.

Conclusions

This investigation showed that the growth of S. sanguis biofilms were significantly affected by both glass-ionomer formulations, the greater reduction being noted on the surface of the fluoride containing GIC. S. sanguis biofilms produced reduction on the surface hardness of the cement equivalent to that seen after immersion in lactic acid at pH 5. This indicates that while S. sanguis biofilm is affected by the GIC, there is also a decrease in hardness of the cement indicating some cement degradation.     

Surface roughness of orthodontic band cements with different compositions

Objectives

The present study evaluated comparatively the surface roughness of four orthodontic band cements after storage in various solutions.

Material and Methods

eight standardized cylinders were made from 4 materials: zinc phosphate cement (ZP), compomer (C), resin-modified glass ionomer cement (RMGIC) and resin cement (RC). Specimens were stored for 24 h in deionized water and immersed in saline (pH 7.0) or 0.1 M lactic acid solution (pH 4.0) for 15 days. Surface roughness readings were taken with a profilometer (Surfcorder SE1200) before and after the storage period. Data were analyzed by two-way ANOVA and Tukey''s test (comparison among cements and storage solutions) or paired t-test (comparison before and after the storage period) at 5% significance level.

Results

The values for average surface roughness were statistically different (p<0.001) among cements at both baseline and after storage. The roughness values of cements in a decreasing order were ZP>RMGIC>C>R (p<0.001). After 15 days, immersion in lactic acid solution resulted in the highest surface roughness for all cements (p<0.05), except for the RC group (p>0.05). Compared to the current threshold (0.2 µm) related to biofilm accumulation, both RC and C remained below the threshold, even after acidic challenge by immersion in lactic acid solution.

Conclusions

Storage time and immersion in lactic acid solution increased the surface roughness of the majority of the tested cements. RC presented the smoothest surface and it was not influenced by storage conditions.     

Effects of root dentin surface coating with all-in-one adhesive materials on biofilm adherence

OBJECTIVES: Sealing of exposed root dentinal surfaces with adhesive materials is expected to be a promising approach for preventing root dentin caries. The aim of this study was to evaluate the effects of surface coating with all-in-one adhesives on inhibiting Streptococcus mutans biofilm attachment. MATERIALS AND METHODS: Bovine root dentin was cut and ground with #600-grit SiC paper. Each of the three all-in-one adhesives, Hybrid Bond (HB), Reactmer Bond (RB) or Shake One (SO) was single-coated on the dentin surfaces according to the manufacturers' instructions. The dentin surface without coating served as the control. The surface roughness of the coated and non-coated dentin surfaces was recorded by means of laser microscope measurements. S. mutans artificial biofilms were then grown on the surface of each specimen in a microcosm for 20h. The amounts of bacteria and water insoluble glucan in the retained biofilm on the surface of the specimens were measured. All numerical data were statistically analyzed using one-way ANOVA & Tukey's HSD (p<0.05). RESULTS: All of the coated groups showed significantly lower susceptibility to biofilm attachment compared with the non-coated root dentin (p<0.05). Among the coated groups, SO showed the lowest susceptibility for biofilm formation. CONCLUSIONS: Three all-in-one adhesive materials could be effective for root surface coating. A fluoride-releasing adhesive, SO demonstrated the strongest potentiality in resisting biofilm formation.     

Effect of Denture Cleansers on the Surface Roughness and Hardness of a Microwave-Cured Acrylic Resin and Dental Alloys

PURPOSE: This study evaluated the effect of denture cleansers on the surface hardness of a denture base resin, and on the surface roughness of the resin and Co-Cr and Ti-6Al-4V alloys. MATERIALS AND METHODS: Forty-eight disc-shaped specimens were fabricated of a microwave-cured acrylic resin, each having one of the alloys attached to its surface. The specimens were randomly divided into 6 groups, each consisting of 8 samples. Specimens were exposed to one of the three cleansing treatments (polident, manipulation pharmacy cleanser, and water) as follows. Group I: Co-Cr + polident; Group II: Co-Cr + manipulation; Group III: Co-Cr + water; Group IV: Ti-6Al-4V + polident; Group V: Ti-6Al-4V + manipulation; and Group VI: Ti-6Al-4V + water. Three exposures lasting 5 minutes each were conducted daily, and repeated after storage periods of 1, 14, and 29 days in artificial saliva at 37 degrees C. Hardness and roughness measurements were undertaken immediately after specimen preparation (T0) and on the 1st (T1), 15th (T15), and 30th (T30) day following the beginning of storage. Three roughness and hardness evaluations were carried out for each sample and testing time, and mean values were calculated. Results were analyzed using ANOVA and linear regression. RESULTS: The Knoop hardness test demonstrated differences (p < 0.05) between Groups I and IV at T1 and T30 (14.30 +/- 2.78; 14.06 +/- 1.76) and between Groups II and V at T15 (16.99 +/- 2.24). Significant differences (p < 0.05) in resin roughness (in microm) were observed between Groups I and IV at T15 and T30 (0.14 +/- 0.06; 0.21 +/- 0.38). With regard to Co-Cr, roughness data showed differences (p < 0.05) for all groups at T30 (Group I: 0.15 +/- 0.07; Group II: 2.43 +/- 0.66; Group III: 4.05 +/- 1.03), for Group II at T1 (0.10 +/- 0.03), and for Group I at T15 (0.15 +/- 0.02). There were significant differences (p < 0.05) in titanium roughness for Group IV at T15 (0.12 +/- 0.01) and T30 (0.11 +/- 0.04). CONCLUSIONS: Manipulated cleanser containing sodium perborate increased surface roughness and hardness, probably due to its incapacity to remove the pellicle formed on the acrylic resin and dental alloys.     

Anti-biofilm activity of silver nanoparticle-containing glass ionomer cements

ObjectiveTo develop a silver nanoparticle (AgNP) formulation for incorporation into glass ionomer cements (GICs) which minimises biofilm growth on restoration surfaces.MethodsGICs, Fuji IX, Ketac Molar, and Riva Selfcure were modified with 6, 10 and 24 μg per GIC capsule of α-lipoic acid-capped AgNPs. Monoculture biofilms of Streptococcus mutans were cultured (72 h) on GIC specimens (n = 3) and biofilm accumulation was quantified using a viability stain with confocal laser scanning microscopy. Compression strength and flexural strength (CS & FS) were measured according to ISO 9917-1:2007 (n = 8, n = 25). GIC colour was measured at 0, 1, and 14 days following AgNP incorporation using a digital spectrophotometer. Silver release from AgNP-modified GIC specimens was monitored at 1, 3, 7 and 14 days using inductively coupled plasma-mass spectrometry.ResultsAgNP-modified Fuji IX demonstrated the greatest reduction in biofilm accumulation, with 10 μg Ag/capsule inhibiting biofilm formation by 99%. Ketac Molar and Riva Selfcure required 24 μg Ag/capsule to achieve 78% biofilm reduction. AgNP-modified GICs demonstrated significantly higher CS and FS than sintered silver-containing GICs, and possessed equivalent or higher strength values when compared to unmodified GICs. The colour shades of AgNP-modified GICs were more comparable to VITA shades of non-modified GICs than were sintered silver-containing GICs. The silver (≥99.6%) remained within the GIC for at least two weeks following incorporation.SignificanceAgNP-modified GICs exhibited significant antibiofilm activity and retained mechanical properties equivalent or superior to non-modified GICs. AgNP-modified GICs could reduce bacterial colonisation on and around restorations thereby reducing restoration failure caused by secondary caries.     

Biological responses of anodized titanium implants under different current voltages

The oxide layer of a titanium surface is very stable, and seems to result in excellent biocompatibility and successful osseointegration. The purpose of this study was to investigate the effects of high anodic oxidation voltages on the surface characteristics of titanium implants and the biologic response of rabbit tibiae. Bone tissue responses were evaluated by removal torque tests and histomorphometric analysis. Screw-shaped implants with microthreads were made of commercially pure titanium (Grade II). We prepared anodized implants under 300 V (group I), 400 V (group II), 500 V (group III) and 550 V (group IV). The surface characteristics of specimens were inspected according to three categories: surface morphology, surface roughness and oxide layer thickness. The screw-shaped implants were installed in rabbit tibiae. The removal torque values were measured and histomorphometric analysis was done after 1- and 3-month healing periods. Data indicate that as anodic oxidation voltage increased above 300 V, oxide layer thickness increased rapidly and pore size also increased. The roughness values of the implants increased with voltage up to 500 V, but decreased at 550 V. In the removal torque test, group III showed higher values than groups I and II at a statistically significant level (P < 0.05) after a 1-month healing period. In histomorphometric analysis, groups III and IV, after a 3-month healing period, showed greater bone to implant contact ratios for the total implant surface than did group I (P < 0.05).     

Effect of a multi-layer infection control barrier on the micro-hardness of a composite resin

Objective

The aim of this study was to evaluate the effect of multiple layers of an infection control barrier on the micro-hardness of a composite resin.

Material and Methods

One, two, four, and eight layers of an infection control barrier were used to cover the light guides of a high-power light emitting diode (LED) light curing unit (LCU) and a low-power halogen LCU. The composite specimens were photopolymerized with the LCUs and the barriers, and the micro-hardness of the upper and lower surfaces was measured (n=10). The hardness ratio was calculated by dividing the bottom surface hardness of the experimental groups by the irradiated surface hardness of the control groups. The data was analyzed by two-way ANOVA and Tukey''s HSD test.

Results

The micro-hardness of the composite specimens photopolymerized with the LED LCU decreased significantly in the four- and eight-layer groups of the upper surface and in the two-, four-, and eight-layer groups of the lower surface. The hardness ratio of the composite specimens was <80% in the eight-layer group. The micro-hardness of the composite specimens photopolymerized with the halogen LCU decreased significantly in the eight-layer group of the upper surface and in the two-, four-, and eight-layer groups of the lower surface. However, the hardness ratios of all the composite specimens photopolymerized with barriers were <80%.

Conclusions

The two-layer infection control barrier could be used on high-power LCUs without decreasing the surface hardness of the composite resin. However, when using an infection control barrier on the low-power LCUs, attention should be paid so as not to sacrifice the polymerization efficiency.     

牙科陶瓷表面粗糙度与细菌粘附的实验研究

目的　比较陶瓷抛光和陶瓷上釉后表面粗糙度的差异及变形链球菌在其表面的粘附能力。方法　制作陶瓷样本 30个。A组陶瓷用金刚石抛光膏打磨抛光 ,B组陶瓷上釉 ,C组陶瓷用2 4 0 #Al2 O3 磨头磨平。用轮廓仪测量各组陶瓷样本的表面粗糙度。将各组样本置于变形链球菌悬浮液中 ,37℃培养 1h。图像分析仪计算变形链球菌在各样本表面的粘附面积比。结果　A、B、C组陶瓷的表面粗糙度分别为 (0 1987± 0 0 5 7) μm、(0 1990± 0 0 91) μm及 (0 4 2 6 0± 0 174 ) μm。变形链球菌在A、B、C 3组陶瓷表面的粘附面积比分别为 (15 92± 4 37) %、(16 39± 6 31) %、(41 4 8± 12 1) %。经统计学分析 ,A、B组陶瓷组间表面粗糙度及细菌粘附面积比差异无显著性 (P >0 0 5 ) ,C组陶瓷与其他各组样本表面粗糙度及细菌粘附面积比差异有高度显著性 (P <0 0 1)。结论　陶瓷上釉和抛光表面能达到同样光滑 ,细菌在其表面的粘附量亦基本相同。粗糙陶瓷表面比光滑陶瓷表面更容易粘附口腔细菌     

A castor oil-containing dental luting agent: effects of cyclic loading and storage time on flexural strength

Favorable results in the use of castor oil polyurethane (COP) as pulp capping, membrane material, sealer, mouthwash and in bone repair, associated with the fact that Ricinus communis is not derived from petroleum and it is abundant in Brazil, encourage researches in the development of luting agents.

Objectives

This study compared the flexural strength (FS) of a castor oil-containing dental luting agent with a weight percentage of 10% (wt%) of calcium carbonate (COP10) with RelyX ARC (RX) after mechanical cycling (MC) and distilled water storage.

Material and Methods

Sixty-four specimens (25x2x2 mm) were fabricated and divided into two groups, COP10 and RX (control). Each group was divided into 4 subgroups (n=8) according to the storage time, 24 hours (24 h) or 60 days (60 d), and the performance (MC+FS) or not (only FS) of the mechanical cycling test. The FS (10 kN; 0.5 mm/min) and MC tests (10,000 cycles, 5 Hz, 0.5 mm/min) were carried out using an MTS-810 machine. The data were analyzed using ANOVA (α=0.05).

Results

The obtained FS (MPa) values were: COP10 24h- 19.04±2.41; COP10 60d- 17.92±3.54; RX 24h- 75.19±3.43; RX 60d- 88.77±6.89. All the RX specimens submitted to MC fractured, while the values for COP10 after MC were as follows: COP10 24h- 17.90±1.87 and COP10 60d- 18.60±1.60.

Conclusions

A castor oil-containing dental luting agent with a weight percentage of 10% (wt%) of calcium carbonate is resistant to mechanical cycling without decreases in flexural strength. However, mean COP10 showed only about 25% of the RelyX ARC mean flexural strength.     

义齿基托修复材料表面粗糙度对变形链球菌粘附的影响

目的：观察义齿基托修复材料的表面粗糙度对变形链球菌粘附的影响,为正确处理义齿基托的表面提供参考。方法：常规制备钴铬合金标准试件8mm×8mm×1mm共40件,分为5组,每组8件,分别按照五种不同的打磨方法处理试件表面,使用手持式表面粗糙度仪测量每组试件的表面粗糙度,通过体外粘附实验观察变形链球菌在不同表面粗糙度试件上的粘附情况,进行Pearson相关性检验和单因素方差分析。结果：各组试件的表面粗糙度与变形链球菌粘附量之间有显著相关性（P〈O．01）,各组试件细菌粘附量之间的差异具有显著的统计学意义（P〈0．01）。结论：义齿基托修复材料表面粗糙度与细菌的粘附量呈正相关,提示制作义齿时应通过正确的方法减小义齿的表面粗糙度。     

Vickers hardness of cast commercially pure titanium and Ti-6Al-4V alloy submitted to heat treatments

The purpose of this study was to evaluate the effect of heat treatments on the Vickers hardness of commercially pure titanium and Ti-6Al-4V cast alloys. Six-millimeter-diameter cylindrical specimens were cast in a Rematitan System. Commercially pure titanium and Ti-6Al-4V alloy specimens were randomly assigned to 3 groups (n=10) that received the following heat treatments: control (no heat treatment); treatment 1 (T1): heating at 750 degrees C for 2 h; and treatment 2 (T2): annealing at 955 degrees C for 1 h and aging at 620 degrees C for 2 h. After heat treatments, the specimens were embedded in acrylic resin and their surface was ground and polished and hardness was measured. Vickers hardness means (VHN) and standard deviations were analyzed statistically by Kruskal-Wallis test at 5% significance level. For commercially pure titanium, Vickers hardness means of group T2 (259.90 VHN) was significantly higher than those of the other groups (control--200.26 VHN and T1--202.23 VHN), which presented similar hardness means to each other (p>0.05). For Ti-6Al-4V alloy, statistically significant differences were observed among the three groups: T2 (369.08 VHN), T1 (351.94 VHN) and control (340.51 VHN) (p<0.05). The results demonstrated different hardness of CP Ti and Ti-6Al-4V when different heat treatments were used. For CP Ti, VHN means of T2 group was remarkably higher than those of control and T1 group, which showed similar VHN means to each other. For Ti-6Al-4V alloy, however, VHN means recorded for each group may be presented as follows: T2>T1>control.     

钛表面粗糙度对成骨细胞核心结合因子α1亚基基因表达的影响

目的 通过研究种植体表面粗糙度对成骨细胞黏附、增殖、碱性磷酸酶(alkaline phosphatase,ALP)含量以及核心结合因子α1亚基(core bindingfactor alpha 1 subunit,Cbfα1)基因表达的影响,探讨种植体表面形态影响界面生物学反应的可能途径.方法 直径15 mm、厚2 mm的纯钛圆盘试件48个,均分为4组,每组12个.分别采用粒度为88～125μm(微度粗糙组)、125～150μm(中度粗糙组)、250～500μm(重度粗糙组)的金刚砂颗粒喷砂,后两组试件再用10%的盐酸、硫酸混合液处理5 min;剩余1组未处理作为对照组.测试4组试件表面粗糙度.将成骨细胞接种于4组试件表面,采用扫描电镜、吖啶橙荧光染色及考马斯亮蓝染色检测试件粗糙度对成骨细胞黏附、增殖的影响.采用酶联免疫吸附实验(enzyme linked immunosorbent assay,ELISA)测定成骨细胞ALP含量的变化.采用荧光实时定量聚合酶链反应测定成骨细胞Cbfα1基因表达的变化.结果 处理后微、中、重度粗糙组和对照组的粗糙度分别为(1.00±0.20)、(1.67±0.08)、(2.40±0.20)和(0.12±0.03)μm.3个粗糙组成骨细胞的数量及ALP含量均高于对照组(P＜0.05).与对照组相比,粗糙表面上Cbfα1的mRNA水平明显增加(P＜0.05);中度粗糙组为(0.93±0.03);微度粗糙组次之,为(0.50±0.03);重度粗糙组最低,为(0.37±0.07);对照组仅为(0.10±0.06).结论 种植体表面粗糙度的差异可造成成骨细胞骨源性基因Cbfα1表达及ALP含量不同.粗糙度在1～2μm范围内成骨细胞的生长、ALP含量及Cbfα1基因的表达较强.     

纳米无机载银磷酸锆树脂基托对6种口腔细菌的体外抗菌研究

目的:通过体外粘附实验,研究纳米无机载银磷酸锆加入到树脂基托中后是否具有抗菌性。方法:将纳米无机载银磷酸锆(Conval PAg-40型)按1%、3%、5%、7%比例添加到树脂基托中制成树脂片,未添加者为对照组,打磨抛光,金相显微镜观察试件表面无划痕、粗糙度测定仪测得表面粗糙度值无统计学差异后,采用薄膜密贴法检测该抗菌树脂片对变形链球菌、黏性放线菌、内氏放线菌、血链球菌、牙龈卟啉单胞菌、白色念珠菌的抗菌性,比较分析树脂基托抗菌性能与添加抗菌剂比例的相关性。结果:3%、5%、7%组培养的牙龈卟啉单胞菌以及1%、3%、5%、7%组培养的变形链球菌、黏性放线菌、内氏放线菌、血链球菌、白色念珠菌菌落数均低于对照组,差异有统计学意义(P<0.05),抗菌率随添加比例的增加逐渐升高;1%组培养的牙龈卟啉单胞菌菌落数与对照组相比差异无统计学意义(P>0.05)。结论:纳米无机载银磷酸锆树脂基托有良好的抗菌效能,其抗菌率随抗菌剂比例的添加而呈线性上升趋势。     

多种抛光磨头对烤瓷表面粗糙度的影响

目的：比较釉瓷上釉和不同打磨抛光磨头处理后,烤瓷表面粗糙度的不同,为临床选择抛光方法提供实验依据。方法：制作圆盘状瓷片70片,随机分为7组（n ＝10）。以釉瓷上釉作对照为第1组,第2组至第7组均用松风氧化铝白砂石打磨,第2组打磨后不做处理;第3组打磨后使用松风 Ceramiste 烤瓷抛光套装磨头抛光;第4组在第3组的基础上加用松风Ceramaster 精细烤瓷抛光磨头抛光;第5组打磨后使用德国固美（Komer）烤瓷抛光套装磨头抛光;第6组打磨后使用固美氧化锆抛光磨头抛光;第7组打磨后使用德国 EVE 氧化锆抛光磨头抛光。对瓷片进行轮廓算术平均偏差（Ra）、轮廓的微观不平度十点高度（Rz）、最大轮廓峰高（Rp）的测量,使用 SPSS 16．0统计软件对测量值进行单因素方差分析,并采用扫描电镜对表面形态进行观察。结果：第2、3组的 Ra、Rp 值均大于第1组（P ＜0．05）;第4、5、6、7组的 Ra、Rp 值与第1组差异无显著性（P ＞0．05）;第2、3、4、5组的 Rz 值均大于第1组（P ＜0．05）;第6、7组的 Rz 值与第1组无显著性差异（P ＞0．05）。电镜下观察第6、7组与第1组瓷面平整度相似;第4、5组瓷面较平整,凹坑较少;第2、3组瓷面棱脊、凹坑较多。结论：使用打磨颗粒为微米级超细天然金刚砂的抛光磨头能达到类似上釉的效果。     

氧化锆陶瓷表面粗糙度对微生物附着的影响

目的 分析牙科氧化锆陶瓷表面粗糙度对微生物附着的影响. 方法 使用碳化硅砂纸将氧化锆陶瓷表面逐级打磨为粗糙、中等粗糙和平滑表面,使用原子力显微镜和光学接触角测量仪测定表面粗糙度、形态及接触角,通过使用变异链球菌UA159处理的探针检测其与不同粗糙度氧化锆陶瓷表面的粘附力;并将氧化锆陶瓷与变异链球菌共培养,通过扫描电镜和激光共聚焦显微镜观察生物膜形成情况. 结果 不同粗糙度表面的氧化锆陶瓷,由粗糙到平滑,接触角逐渐减小,表面能逐渐增大,表面生物膜厚度逐渐减小,变异链球菌与氧化锆陶瓷表面的粘附力减小,但生物膜细菌量差异无统计学意义(P>0. 05). 结论 随着氧化锆表面粗糙度增加,变异链球菌的粘附力增加;随着粗糙度减小,生物膜厚度与微生物数量相应减小,但表面粗糙度减小至一定数值后,生物膜厚度与微生物数量无显著变化.     

The biaxial flexural strength and fatigue property of Lava Y-TZP dental ceramic.

OBJECTIVES: The development of yttrium oxide partially stabilized zirconia (Y-TZP) has allowed the use of ceramic in load-bearing sites. The aim of this study was to evaluate and compare the biaxial flexural strength, hardness and fatigue life of colored and uncolored zirconia in the LAVAtrade mark system. MATERIALS AND METHODS: Eight groups (n=30) of standardized disc specimens (15mmx1.3mm) were used to examine the biaxial flexural strength (ISO 6872 standard) using a Dartec HC10 Fatigue Tester (Zwick Ltd., UK) and Vickers hardness was also measured. The uncolored, FS4, FS7 groups were also submitted to dynamic fatigue testing to produce stress-number curves. The strength reliability was analyzed using Weibull distribution. RESULTS: All groups had a mean biaxial flexural strength, hardness and Weibull modulus (m) of approximately 1100MPa, 1300HV and 9.8-12.9, respectively. One-way analysis of variance (ANOVA) showed no significant difference in biaxial flexural strength among the eight groups (p>0.05). Two-way ANOVA showed no significant differences in hardness values among groups except FS1 and FS5 which had significantly higher hardness values than FS4 and FS7 (p<0.001) and FS5 also had a higher hardness value than FS3 (p<0.05). Additionally, uncolored, FS4 and FS7 survived at 5x10(5) cycles at a stress level in the range of 60-65% of the mean biaxial flexural strength. CONCLUSION: There was no difference in flexural strength of uncolored and colored Y-TZP ceramic. The fatigue limit of uncolored, FS4 and FS7 zirconia may be defined as lying between 60 and 65% of the stress to failure.     

不同种植体表面改性对细菌生物膜的影响

目的:研究临床常用的3种钛种植体不同表面处理对口腔内常见菌群牙龈卟啉单胞菌(Porphyromanusgingivalis,P.gingivalis)、具核梭杆菌(Fusobacterium nucleatum,F.nucleatum)及血链球菌(Streptococcus sanguis,S.sanguis)生物膜黏附的影响。方法:将钛片分成3组进行表面改性处理,分别为:电解沉积羟基磷灰石(HA)组、微弧氧化(MAO)组和大颗粒喷砂酸蚀(SLA)组,进行表面性能检测;在3组钛片上分别培养Pg、Fn及Ss 4 d,通过菌落形成单位(CFU)法、噻唑蓝(MTT)法和扫描电子显微镜(SEM)探究细菌的黏附情况。结果:(1)SEM观察表面形貌可见HA组表面大量不规则的棒状结构;MAO表面“火山口”样结构,孔径在0.1~1μm之间;SLA表面为不规则凹陷,大小不一且边缘锋利。3组表面粗糙度Ra值:SLA组0.05);Pg生物膜在MAO组钛片上活性最高,与另外2组有统计学差异(P<0.01)。(3)利用SEM观察显示,细菌活性与种植体表面形态结构有关。结论:细菌在种植体表面黏附受到表面形貌影响,与粗糙度及物理构型有关。对于Pg、Ss和Fn 3种细菌,SLA在3种表面处理中细菌粘附量最少。     

Effect of an acrylic resin combined with an antimicrobial polymer on biofilm formation

Objectives

The purpose of this study was to evaluate the antimicrobial activity of an acrylic resin combined with an antimicrobial polymer poly (2-tert-butylaminoethyl) methacrylate (PTBAEMA) to inhibit Staphylococcus aureus, Streptococcus mutans and Candida albicans biofilm formation.

Material and Methods

Discs of a heat-polymerized acrylic resin were produced and divided according to PTBAEMA concentration: 0 (control), 10 and 25%. The specimens were inoculated (10⁷ CFU/mL) and incubated at 37ºC for 48 h. After incubation, the wells were washed and each specimen was sonicated for 20 min. Replicate aliquots of resultant suspensions were plated at dilutions at 37ºC for 48 h. The number of colony-forming units (CFU) was counted and expressed as log (CFU+1)/mL and analyzed statistically with α=.05.

Results

The results showed that 25% PTBAEMA completely inhibited S. aureus and S. mutans biofilm formation. A significant reduction of log (CFU+1)/mL in count of S. aureus (control: 7.9±0.8A; 10%: 3.8±3.3B) and S. mutans (control: 7.5±0.7A; 10%: 5.1±2.7B) was observed for the group containing 10% PTBAEMA (Mann-Whitney, p<0.05). For C. albicans, differences were not significant among the groups (control: 6.6±0.2A; 10%: 6.6±0.4A; 25%: 6.4±0.1A), (Kruskal-Wallis, p>0.05, P=0.079).

Conclusions

Acrylic resin combined with 10 and 25% of PTBAEMA showed significant antimicrobial activity against S. aureus and S. mutans biofilm, but it was inactive against the C. albicans biofilm.