Objective To assess the microleakage of Class V restorations made with two resin-modified glass ionomer cements （RMGICs） and two polyacid-modified composite resins （PMCRs）. Methods Restorations of the four materia...Objective To assess the microleakage of Class V restorations made with two resin-modified glass ionomer cements （RMGICs） and two polyacid-modified composite resins （PMCRs）. Methods Restorations of the four materials （ GC Fuji Ⅱ LC, Vitremer^TM, Dyract AP and F2000^TM ） were placed in facial Class V cavity preparations in forty noncarious human molar teeth. Teeth were randomly assigned to 4 experimental groups of 10 teeth each. After thermal cycling（ ×20, 5 -55℃ ） , the interface between dentin and restorations was spattercoated with gold and observed under scanning electron microscopy （SEM）. Then the square and average width of margin gaps of central 1/3 interface were recorded with image analysis software. Results The data indicated no significant differences between all the restorative materials for both occlusal and gingival margins. Further analysis revealed there were statistically significant differences between occlusal margins and gingival margins for VitremerTM and Dyract AP, respectively. Conclusion None of the tested materials guaranteed margins free of microleakage. Resin-modified glass ionomer cements showed similar margin gaps to the polyacid-modified composite resins tested.展开更多
The interface and surface properties of nano-hydroxyapatite(n-HA) and poly( 1, 4-phenylene sulfide)-poly (2,4-phenylene sulfide acid)(PPS-PPSA) copolymer composite were investigated. The results show that there are so...The interface and surface properties of nano-hydroxyapatite(n-HA) and poly( 1, 4-phenylene sulfide)-poly (2,4-phenylene sulfide acid)(PPS-PPSA) copolymer composite were investigated. The results show that there are some strong interface combinations of calcium ion (Ca2+ ), car-boxyl (-COO- ) and phosphate radicle ion (PO_4~3- ) between copolymer and n-HA in the composite. The presence of the 2,4-phenylene sulfide acid in copolymer can increase the affinity to n-HA, which causes the formation of chemical bindings between the PPS-PPSA copolymer and n-HA. XRD analysis and IR surface analysis indicate that n-HA is not encapsulated by copolymer but exposed on the surface of the composite, and has same structure and properties with the origi-nal n-HA. The presence of the interface chemical bindings between the PPS-PPSA copolymer and n-HA can increase the content of n-HA in composite but does not cause the decrease of the composite mechanical strength.展开更多
The search of biomass-based substitutes for fossil-based plastics has become a pressing task due to the severe long-term threats of plastic wastes to the ecosystem.However,the development in this area is strongly impe...The search of biomass-based substitutes for fossil-based plastics has become a pressing task due to the severe long-term threats of plastic wastes to the ecosystem.However,the development in this area is strongly impeded by the high cost of biomass separation and the poor processability of unseparated biomass.Herein,we demonstrate,for the first time,an efficient and scalable method to generate greener plastics by directly integrating unseparated biomass waste(i.e.,wood powder)with crosslinked covalent adaptable networks.Through a simple compression molding process,the wood biomass and polymer particles can be fused together to form a continuous material,which is endowed with repairability,reprocessibility,and closed-loop full recyclability.The method demonstrated in this work paves the way for largescale industrial production of environmentally friendly biomass-based plastics.展开更多
Chirality is a unique phenomenon in nature. Chiral interactions play an important role in biological and physiological process- es, which provides much inspiration for scientists to develop cbiral materials. As a brea...Chirality is a unique phenomenon in nature. Chiral interactions play an important role in biological and physiological process- es, which provides much inspiration for scientists to develop cbiral materials. As a breakthrough from traditional materials, bi- ointerface materials based on chiral polymers have attracted increasing interest over the past few years. Such materials ele- gantly combine the advantages of chiral surfaces and traditional polymers, and provide a novel solution not only for the inves- tigation of chiral interaction mechanisms but also for the design of biomaterials with diverse applications, such as in tissue en- gineering and biocompatible materials, bioregulation, chiral separation and chiral sensors. Herein, we summarize recent ad- vances in the study of chiral effects and applications of chiral polymer-based biointerface materials, and also present some challenges and perspectives.展开更多
文摘Objective To assess the microleakage of Class V restorations made with two resin-modified glass ionomer cements （RMGICs） and two polyacid-modified composite resins （PMCRs）. Methods Restorations of the four materials （ GC Fuji Ⅱ LC, Vitremer^TM, Dyract AP and F2000^TM ） were placed in facial Class V cavity preparations in forty noncarious human molar teeth. Teeth were randomly assigned to 4 experimental groups of 10 teeth each. After thermal cycling（ ×20, 5 -55℃ ） , the interface between dentin and restorations was spattercoated with gold and observed under scanning electron microscopy （SEM）. Then the square and average width of margin gaps of central 1/3 interface were recorded with image analysis software. Results The data indicated no significant differences between all the restorative materials for both occlusal and gingival margins. Further analysis revealed there were statistically significant differences between occlusal margins and gingival margins for VitremerTM and Dyract AP, respectively. Conclusion None of the tested materials guaranteed margins free of microleakage. Resin-modified glass ionomer cements showed similar margin gaps to the polyacid-modified composite resins tested.
文摘The interface and surface properties of nano-hydroxyapatite(n-HA) and poly( 1, 4-phenylene sulfide)-poly (2,4-phenylene sulfide acid)(PPS-PPSA) copolymer composite were investigated. The results show that there are some strong interface combinations of calcium ion (Ca2+ ), car-boxyl (-COO- ) and phosphate radicle ion (PO_4~3- ) between copolymer and n-HA in the composite. The presence of the 2,4-phenylene sulfide acid in copolymer can increase the affinity to n-HA, which causes the formation of chemical bindings between the PPS-PPSA copolymer and n-HA. XRD analysis and IR surface analysis indicate that n-HA is not encapsulated by copolymer but exposed on the surface of the composite, and has same structure and properties with the origi-nal n-HA. The presence of the interface chemical bindings between the PPS-PPSA copolymer and n-HA can increase the content of n-HA in composite but does not cause the decrease of the composite mechanical strength.
基金The authors would like to acknowledge Prof.Yifu Ding of the University of Colorado Boulder for the instrumentation support with DMA.This work was supported by the University of Colorado Boulder,Wong KC Education Foundation,and the National Natural Science Foundation of China(51673072).Su Z would like to thank China Scholarship Council(CSC)for financial support.
文摘The search of biomass-based substitutes for fossil-based plastics has become a pressing task due to the severe long-term threats of plastic wastes to the ecosystem.However,the development in this area is strongly impeded by the high cost of biomass separation and the poor processability of unseparated biomass.Herein,we demonstrate,for the first time,an efficient and scalable method to generate greener plastics by directly integrating unseparated biomass waste(i.e.,wood powder)with crosslinked covalent adaptable networks.Through a simple compression molding process,the wood biomass and polymer particles can be fused together to form a continuous material,which is endowed with repairability,reprocessibility,and closed-loop full recyclability.The method demonstrated in this work paves the way for largescale industrial production of environmentally friendly biomass-based plastics.
基金the financial support of the National Natural Science Foundation of China(21104061,21275114,91127027,51173142)the National Basic Research Program of China(2013CB933002)the Fundamental Research Funds for the Central Universities(2013-YB-026)
文摘Chirality is a unique phenomenon in nature. Chiral interactions play an important role in biological and physiological process- es, which provides much inspiration for scientists to develop cbiral materials. As a breakthrough from traditional materials, bi- ointerface materials based on chiral polymers have attracted increasing interest over the past few years. Such materials ele- gantly combine the advantages of chiral surfaces and traditional polymers, and provide a novel solution not only for the inves- tigation of chiral interaction mechanisms but also for the design of biomaterials with diverse applications, such as in tissue en- gineering and biocompatible materials, bioregulation, chiral separation and chiral sensors. Herein, we summarize recent ad- vances in the study of chiral effects and applications of chiral polymer-based biointerface materials, and also present some challenges and perspectives.
