Liquid Crystalline Network Composites Reinforced by Silica Nanoparticles

Liquid crystalline networks (LCNs) are a class of polymers, which are able to produce mechanical actuation in response to external stimuli. Recent creation of LCNs with exchangeable links (xLCNs) makes LCNs easy moldable. As the xLCNs need to be shaped at a high temperature, it is important to enhance their thermal and mechanical properties. In this paper, a series of xLCNs/SiO₂ composites containing 1%–7% SiO₂ nanoparitcles (SNP) were prepared and their thermal and mechanical properties were examined. The results show that xLCNs/SNP composites have lower liquid crystalline-isotropic phase transition temperature and higher decomposition temperature than pure LCN. The tensile strength and the elongation at break of xLCNs at high temperatures were also enhanced due to the addition of SNPs.     

Viscoelastic stability of pre-cured resin-composite CAD/CAM structures

ObjectivesTo study the effect of water storage (3 months) on the creep deformation and recovery of CAD/CAM composite materials to determine their viscoelastic stability.Materials and methodsFive CAD/CAM composite blocks, with increasing filler loading, and one polymer-infiltrated ceramic network (PICN) were studied. Six specimens of each material were separated into two groups (n=3) according to their storage conditions (24 h dry storage at 23°C versus 3 months storage in 37°C distilled water). A constant static compressive stress of 20 MPa was applied on each specimen via a loading pin for 2 h followed by unloading and monitoring strain recovery for a further period of 2 h. The maximum creep-strain (%) and permanent set (%) were recorded. Data were analysed via two-way ANOVA followed by one-way ANOVA and Bonferroni post hoc tests (<0.05) for comparisons between the materials. Homogeneity of variance was calculated via Levene’s statistics.ResultsThe maximum creep strain after 24 h dry ranged from 0.45% to 1.09% and increased after 3-month storage in distilled water to between 0.71% and 1.85%. The permanent set after 24 h dry storage ranged from 0.033% to 0.15% and increased after 3-month water storage to between 0.087% and 0.18%. The maximum creep strain also reduced with increasing filler loading.SignificanceThe PICN material exhibited superior dimensional stability to all of the pre-cured resin composite blocks in both storage conditions with deformation being predominantly elastic rather than viscoelastic. Notwithstanding, two of the resin-matrix composite blocks approached the PICN performance, when dry, but less so after water storage.     

Do bulk‐fill resins decrease the restorative time in posterior teeth? A systematic review and meta‐analysis of in vitro studies

The aim of the present study was to compare the restorative time for filling cavities in posterior teeth using bulk‐fill and conventional resin composites through a systematic review and meta‐analysis. A search for clinical trials and laboratory studies was performed in PubMed/MEDLINE, Scopus, the Latin American and Caribbean Health Sciences Literature database, the Brazilian Library in Dentistry, Cochrane Library, Clinical Trials, and ReBEC (Registro Brasileiro de Ensaios Clínicos) databases without publication year or language restriction. Two reviewers identified eligible studies according to the inclusion criteria: bulk‐fill compared to conventional resin in class I or II, and the restorative time as an outcome. A meta‐analysis of the restorative time mean difference between composites was performed (inverse variance method, random effects model; Z‐test, P ≤ .05). From the 662 eligible studies, 133 were selected for full‐text analysis; three were included in the systematic review and in the meta‐analysis. Overall, the restorative time was lower when bulk‐fill was used (P = .0007, Z = 3.37), as the subgroup full‐body bulk‐fill (P < .00001, Z = 21.00). There was no difference in restorative time between flowable bulk‐fill and conventional resins (P = .08, Z = 1.76). Moderate‐to‐substantial heterogeneity was detected. Full‐body bulk‐fill composites decrease the restorative time in posterior teeth compared to conventional resins. Full‐body bulk‐fill resins require a shorter restorative time to perform restorations in posterior teeth than conventional resins, but the same is not valid for flowable bulk‐fill resin composites.     

葫芦素B-聚乳酸-羟基乙酸共聚物载药纳米粒的构建与药效学评价

目的 以聚乳酸-羟基乙酸共聚物（PLGA）作为纳米制剂载体材料将葫芦素B制备成纳米粒,并考察其对HepG2肝癌细胞的抑制效果。方法 使用乳化溶剂蒸发法制备葫芦素B-PLGA载药纳米粒,以PLGA浓度（X₁）、PVA浓度（X₂）和药物浓度（X₃）作为考察因素,以载药纳米粒的粒径大小（Y₁）和包封率（Y₂）作为评价指标,应用中心复合设计-效应面法优化葫芦素B-PLGA载药纳米粒处方;测定了纳米粒的粒径分布和Zeta电位值,通过透射电镜观察其微观形态,并考察了葫芦素B-PLGA载药纳米粒的体外药物释放特性;比较了葫芦素B与葫芦素B-PLGA载药纳米粒对HepG2肝癌细胞的抑制效果。结果 葫芦素B-PLGA载药纳米粒的最优处方组成为：PLGA浓度为9.0%,PVA浓度为2.0%,药物浓度为4.5%,制备的纳米粒粒径为（145.4±15.8） nm,Zeta电位值为（-7.6±0.8） mV;透射电镜下可观察到纳米粒表面光滑,分布均匀;葫芦素B-PLGA载药纳米粒释药前期出现突释,后期平缓,48 h药物释放达到86%;葫芦素B-PLGA载药纳米粒对HepG2肝癌细胞的抑制作用显著高于葫芦素B。结论 葫芦素B-PLGA载药纳米粒可延缓药物释放,提高对HepG2肝癌细胞的抑制活性,为进一步临床研究奠定实验基础。     

直接法纤维增强复合桥在牙周炎病例中的应用

目的:评价前牙区直接法纤维增强复合桥(FRC bridge)修复单颗切牙缺失伴邻牙松动的牙周炎病例临床应用效果。方法:采用直接法FRC bridge连接所有同颌前牙修复单颗切牙缺失伴邻牙松动的牙周炎病例12例,以弹性义齿修复14例同类病例作为对照,修复后1、6及18个月随访,对临床修复效果以及牙周状况进行评价。结果:修复后1、6或18个月,直接法FRC bridge修复组和对照组解剖外形和边缘适应性均优于弹性义齿修复组(P<0.05);牙周袋探诊深度(PD)及探诊出血指数(BOP)随着观察时间延长而逐渐减小;修复前后PD、BOP、牙齿松动度(TM)差异均存在显著性(P<0.05)。结论:直接法FRC bridge修复单颗切牙缺失伴邻牙松动的牙周炎病例,能达到良好的临床美学修复效果,并可改善邻牙牙周状况。     

纳米羟磷灰石-脂肪族聚酯酰胺复合材料对成骨细胞的生物学作用

目的研究纳米羟磷灰石-脂肪族聚酯酰胺（nHA—PEA）对成骨细胞的生物学作用。方法以含有nHA—PEA的达尔贝科极限必需培养（DMEM）浸提液作用于试验组细胞,DMEM作用于对照组细胞,以甲噻唑四唑氮检测nHA—PEA对成骨细胞生长的影响,流式细胞计数细胞周期的变化,酶联免疫吸附测定细胞碱性磷酸酶（AKP）活性的变化。将细胞和材料联合培养,观察细胞在复合材料上的黏附和生长情况。结果试验组细胞的相对增殖率为92％．107％且无量效关系,试验组与对照组间差异无统计学意义（P〉0．05）;试验组和对照组细胞的细胞周期及AKP活性表达相似,组间差异无统计学意义（P〉0．05）。成骨细胞直接培养于复合材料上,显现出良好的黏附、铺展和生长行为。结论nHA—PEA对成骨细胞的生长和功能无不良影响,具有骨细胞相容性。     

Fatigue resistance and microleakage of CAD/CAM ceramic and composite molar crowns

Purpose: The aim of this study was to determine effect of compressive cyclic loading on fatigue resistance and microleakage of monolithic CAD/CAM molar ceramic and composite crowns. Materials and Methods: Thirty‐two extracted molars were prepared to receive CEREC crowns according to manufacturer's guidelines using a special paralleling device (Parallel‐A‐Prep). Sixteen feldspathic ceramic crowns (VITABLOCS Mark II) (VMII) and 16 resin‐composite crowns (Paradigm‐MZ100 blocks) (PMZ) were milled using a CEREC‐3D machine. Eight crowns of each group were cemented to their respective teeth using self‐etching resin cement (Panavia‐F‐2.0) (PAN), and eight were cemented using self‐adhesive resin cement (RelyX‐Unicem‐Clicker) (RXU). Following storage for 1 week in water, specimens were subjected to uniaxial compressive cyclic loading in an Instron testing machine at 12 Hz for 1,000,000 cycles. Load was applied at the central fossa, and the cycle range was 60–600 N. Specimens were then subjected to microleakage testing. Data were statistically analyzed using factorial ANOVA and Post Hoc (Tukey HSD) tests. Results: All composite crowns survived compressive cyclic loading without fracture, while three ceramic crowns from the subgroup cemented with RXU developed surface cracks at the center of occlusal surfaces, extending laterally. Microleakage scores of ceramic crowns cemented with PAN were significantly lower than those of the other three subgroups (p < 0.05). Conclusions: After 1,000,000 cycles of compressive cyclic loading, PMZ composite molar crowns were more fatigue‐resistant than VMII ceramic crowns. Cement type had a significant effect on fatigue resistance of the ceramic crowns but not the composite ones. Microleakage scores of ceramic crowns cemented with PAN were significantly lower than those of the other subgroups (p < 0.05).     

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目的    检测rhBMP-2/hTGF-β1 /胶原复合材料与rhBMP-2/hTGF-β1生物学活性的差别。方法        本研究于2010年5—12月在福建医科大学附属口腔医院实验室进行。分离培养的Beagle犬骨髓基质细胞中加入质量浓度相同的rhBMP-2/hTGF-β1或rhBMP-2/hTGF-β1 /胶原复合材料后继续培养4 d,通过细胞计数（MTT法）、碱性磷酸酶（ALP）活性检测,分别对rhBMP-2/hTGF-β1 /胶原复合材料和rhBMP-2/hTGF-β1的生物学活性进行检测,并比较其活性差别。结果    rhBMP-2/hTGF-β1/胶原复合材料和rhBMP-2/hTGF-β1均具有生物学活性,并且其生物学活性差异无统计学意义（P > 0.05）。结论    这种合成rhBMP-2/hTGF-β1 /胶原复合材料的方法不会改变生长因子的生物学活性。