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Evaluation of three-dimensional biofilms on antibacterial bonding agents containing novel quaternary ammonium methacrylates

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International Journal of Oral Science 2014年第2期6卷 77-86页

作者： han Zhou Michael d weir Joseph M Antonucci Gary E Schumacher Xue-dong Zhou hockin h K Xu department of Endodontics Prosthodontics and Operative Dentistry University of Maryland Dental School Baltimore USA State Key Laboratory of Oral diseases West China Hospital of Stomatology Sichuan University Biomaterials Group Biosystems and Biomaterials Division National Institute of Standards and TechnologyGaithersburg USA dr. Anthony Volpe Research Center American Dental Association Foundation Gaithersburg USA Center for Stem Cell Biology & Regenerative Medicine University of Maryland School of Medicine Baltimore USA department of Mechanical Engineering University of Maryland Baltimore County USA

Antibacterial adhesives are promising to inhibit biofilms and secondary caries. The objectives of this study were to synthesize and incorporate quaternary ammonium methacrylates into adhesives, and investigate the alkyl chain length effects on three-dimensional biofilms adherent on adhesives for the first time. Six quaternary ammonium methacrylates with chain lengths of 3, 6, 9, 12, 16 and 18 were synthesized and incorporated into Scotchbond Multi-Purpose. Streptococcus mutans bacteria were cultured on resin to form biofilms. Confocal laser scanning microscopy was used to measure biofilm thickness, live/dead volumes and live-bacteria percentage vs. distance from resin surface. Biofilm thickness was the greatest for Scotchbond control; it decreased with increasing chain length, reaching a minimum at chain length 16. Live-biofilm volume had a similar trend. dead-biofilm volume increased with increasing chain length. The adhesive with chain length 9 had 37% live bacteria near resin surface, but close to 100% live bacteria in the biofilm top section. For chain length 16, there were nearly 0% live bacteria throughout the three-dimensional biofilm. In conclusion, strong antibacterial activity was achieved by adding quaternary ammonium into adhesive, with biofilm thickness and live-biofilm volume decreasing as chain length was increased from 3 to 16. Antibacterial adhesives typically only inhibited bacteria close to its surface; however, adhesive with chain length 16 had mostly dead bacteria in the entire three-dimensional biofilm. Antibacterial adhesive with chain length 16 is promising to inhibit biofilms at the margins and combat secondary caries.

关键词： alkyl chain length antibacterial bondingagent dental caries quaternaryammonium methacrylate Streptococcusmutans three-dimensional biofilm

Effects of quaternary ammonium chain length on the antibacterial and remineralizing effects of a calcium phosphate nanocomposite

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International Journal of Oral Science 2016年第1期8卷 45-53页

作者： Ke Zhang Lei Cheng Michael d weir Yu-Xing Bai hockin hK Xu department of Orthodontics School of Stomatology Capital Medical University Biomaterials & Tissue Engineering division Department of EndodonticsPeriodontics and Prosthodontics School of Dentistry University of Maryland State Key Laboratory of Oral diseases West China Hospital of StomatologySichuan University Center for Stem Cell Biology & Regenerative Medicine School of Medicine University of Maryland department of Mechanical Engineering University of Maryland

Composites containing nanoparticles of amorphous calcium phosphate （NACP） remineralize tooth lesions and inhibit caries. A recent study synthesized quaternary ammonium methacrylates （QAMs） with chain lengths （CLs） of 3-18 and determined their effects on a bonding agent. This study aimed to incorporate these QAMs into NACP nanocomposites for the first time to simultaneously endow the material with antibacterial and remineralizing capabilities and to investigate the effects of the CL on the mechanical and biofilm properties. Five QAMs were synthesized： dMAPM （CL3）, dMAhM （CL6）, dMAddM （CL12）, dMAhdM （CL16）, and dMAOdM （CL18）. Each QAM was incorporated into a composite containing 20% NACP and 50% glass fillers. A dental plaque microcosm biofilm model was used to evaluate the antibacterial activity. The flexural strength and elastic modulus of nanocomposites with QAMs matched those of a commercial control composite （n = 6; P 〉 0.1）. Increasing the CL from 3 to 16 greatly enhanced the antibacterial activity of the NACP nanocomposite （P 〈 0.05）; further increasing the CL to 18 decreased the antibacterial potency. The NACP nanocomposite with a CL of 16 exhibited biofilm metabolic activity and acid production that were 10-fold lesser than those of the control composite. The NACP nanocomposite with a CL of 16 produced 2-log decreases in the colony-forming units （CFU） of total microorganisms, total streptococci, and mutans streptococci. In conclusion, QAMs with CLs of 3-18 were synthesized and incorporated into an NACP nanocomposite for the first time to simultaneously endow the material with antibacterial and remineralization capabilities. Increasing the C/reduced the metabolic activity and acid production of biofilms and caused a 2-log decrease in CFU without compromising the mechanical properties. Nanocomposites exhibiting strong anti-biofilm activity, remineralization effects, and mechanical properties are promising materials for tooth restorations that inhibit caries.

关键词： antibacterial nanocomposite calcium phosphate nanoparticles caries inhibition human saliva microcosm biofilm quaternary ammonium chain length

One-year water-ageing of calcium phosphate composite containing nano-silver and quaternary ammonium to inhibit biofilms

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International Journal of Oral Science 2016年第3期8卷 172-181页

作者： Lei Cheng Ke Zhang Chen-Chen Zhou Michael d weir Xue-dong Zhou hockin hK Xu State Key Laboratory of Oral diseases West China School of Stomatology Sichuan University Chengdu China Biomaterials and Tissue Engineering division Department of Endodontics Periodontics and Prosthodontics University of Maryland School of Dentistry Baltimore USA department of Orthodontics School of Stomatology Capital Medical University Beijing China Center for Stem Cell Biology and Regenerative Medicine University of Maryland School of Medicine Baltimore USA department of Mechanical Engineering University of Maryland Baltimore County USA

dental composites are commonly used restorative materials; however, secondary caries due to biofilm acids remains a major problem. The objectives of this study were （1） to develop a composite containing quaternary ammonium dimethacrylate （QAdM）, nanoparticles of silver （NAg）, and nanoparticles of amorphous calcium phosphate （NACP）, and （2） to conduct the first investigation of the mechanical properties, biofilm response and acid production vs water-ageing time from 1 day to 12 months. A 4 x 5 design was utilized, with four composites （NACP-QAdM composite, NACP-NAg composite, NACP-QAdM-NAg composite, and a commercial control composite）, and five water-ageing time periods （1 day, and 3, 6, 9, and 12 months）. After each water- ageing period, the mechanical properties of the resins were measured in a three-point flexure, and antibacterial properties were tested via a dental plaque biofilm model using human saliva as an inoculum. After 12 months of water-ageing, NACP-QAdM- NAg had a flexural strength and elastic modulus matching those of the commercial control （P〉 0.1）. Incorporation of QAdM or NAg into the NACP composite greatly reduced biofilm viability, metabolic activity and acid production. A composite containing both QAdM and NAg possessed a stronger antibacterial capability than one with QAdM or NAg alone （P〈0.05）. The anti-biofilm activity was maintained after 12 months of water-ageing and showed no significant decrease with increasing time （P〉0.1）. In conclusion, the NACP-QAdM-NAg composite decreased biofilm viability and lactic acid production, while matching the load- bearing capability of a commercial composite. There was no decrease in its antibacterial properties after 1 year of water-ageing. The durable antibacterial and mechanical properties indicate that NACP-QAdM-NAg composites may be useful in dental restorations to combat caries.

关键词： antibacterial composite calcium phosphate nanoparticles human saliva microcosm biofilm long-term durability quaternaryammonium silver nanoparticles

Novel rechargeable calcium phosphate nanoparticle-containing orthodontic cement

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International Journal of Oral Science 2017年第1期9卷 24-32页

作者： Xian-Ju Xie dan Xing Lin Wang han Zhou Michael d weir Yu-Xing Bai hockin hK Xu department of Orthodontics School of StomatologyCapital Medical UniversityBeijingChina Biomaterials and Tissue Engineering division Department of EndodonticsPeriodontics and ProsthodonticsUniversity of Maryland Dental SchoolBaltimoreUSA department of dentistry China Rehabilitation Research CenterBeijingChina VIP Integrated department Stomatoiogical Hospital of Jilin UniversityChangchunChina Center for Stem Cell Biology and Regenerative Medicine University of Maryland School of MedicineBaltimoreUSA and department of Mechanical Engineering University of MarylandBaltimore CountyUSA

White spot lesions （WSLs）, due to enamel demineralization, occur frequently in orthodontic treatment. We recently developed a novel rechargeable dental composite containing nanoparticles of amorphous calcium phosphate （NACP） with long-term calcium （Ca） and phosphate （P） ion release and caries-inhibiting capability. The objectives of this study were to develop the first NACP- rechargeable orthodontic cement and investigate the effects of recharge duration and frequency on the efficacy of ion re-release. The rechargeable cement consisted of pyromellitic glycerol dimethacrylate （PMGdM） and ethoxylated bisphenol A dimethacrylate （EBPAdMA）. NACP was mixed into the resin at 40% by mass. Specimens were tested for orthodontic bracket shear bond strength （SBS） to enamel, Ca and P ion initial release, recharge and re-release. The new orthodontic cement exhibited an SBS similar to commercial orthodontic cement without CaP release （P〉 0.1）. Specimens after one recharge treatment （e.g., 1 min immersion in recharge solution repeating three times in one day, referred to as ＂1 min 3 times＂） exhibited a substantial and continuous re-release of Ca and P ions for 14 days without further recharge. The ion re-release did not decrease with increasing the number of recharge/re-release cycles （P〉 0.1）. The ion re-release concentrations at 14 days versus various recharge treatments were as follows： 1 min 3 times〉3 min 2 times〉 1 min 2 times〉6 min 1 time〉3 min 1 time〉 1 min 1 time. In conclusion, although previous studies have shown that NACP nanocomposite remineralized tooth lesions and inhibited caries, the present study developed the first orthodontic cement with Ca and P ion recharge and long-term release capability. This NACP-rechargeable orthodontic cement is a promising therapy to inhibit enamel demineralization and WSLs around orthodontic brackets.

关键词： bond strength calcium phosphate nanoparticles calcium phosphate ion rechargeability long-term ion release orthodonticcement white spot lesions

Primer containing dimethylaminododecyl methacrylate kills bacteria impregnated in human dentin blocks

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International Journal of Oral Science 2016年第4期8卷 239-245页

作者： Chen Chen Lei Cheng Michael d weir Nancy J Lin Sheng Lin-Gibson Xue-dong Zhou hockin hK Xu State Key Laboratory of Oral diseases West China School of Stomatology Sichuan University Biomaterials & Tissue Engineering division Department of Endodontics Periodontics and Prosthodontics University of Maryland Dental School Biomaterials Group Biosystems and Biomaterials Division National Institute of Standards & Technology Center for Stem Cell Biology & Regenerative Medicine University of Maryland School of Medicine department of Mechanical Engineering University of Maryland

Antibacterial dimethylaminododecyl methacrylate （dMAddM） was recently synthesized. The objectives of this study were to：（1） investigate antibacterial activity of dMAddM-containing primer on Streptococcus mutans impregnated into dentin blocks for the first time, and （2） compare the antibacterial efficacy of dMAddM with a previous quaternary ammonium dimethacrylate （QAdM）. Scotchbond Multi-Purpose （SBMP） bonding agent was used. dMAddM and QAdM were mixed into SBMP primer. Six primers were tested： SBMP control primer P, P＋2.5% dMAddM, P＋5% dMAddM, P＋7.5% dMAddM, P＋10% dMAddM, and P＋10% QAdM. S. mutans were impregnated into human dentin blocks, and each primer was applied to dentin to test its ability to kill bacteria in dentinal tubules. Bacteria in dentin were collected via a sonication method, and the colony-forming units （CFU） and inhibition zones were measured. The bacterial inhibition zone of P＋10% dMAddM was 10 times that of control primer （P〈0.05）. CFU in dentin with P＋10% dMAddM was reduced by three orders of magnitude, compared with control. dMAddM had a much stronger antibacterial effect than QAdM, and antibacterial efficacy increased with increasing dMAddM concentration. dentin shear bond strengths were similar among all groups （P〉0.1）. In conclusion, antibacterial dMAddM-containing primer was validated to kill bacteria inside dentin blocks, possessing a much stronger antibacterial potency than the previous QAdM. dMAddM-containing bonding agent was effective in eradicating bacteria in dentin, and its efficacy was directly proportional to dMAddM mass fraction. Therefore, dMAddM may be promisine for use in bonding agents as well as in other restorative and oreventive materials to inhibit bacteria.

关键词： antibacterial bonding agent dental restoration dentin bond strength dimethylaminododecyl methacrylate kil]ing bacteriain dentin Streptococcus mutans

Thomas' CALCULUS.上册.影印版 10th ed.

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An investigation of roof runoff during rain events at the Royal Military College of Canada and potential discharge to Lake Ontario

丛书名：海外优秀数学类教材系列丛

2004年

作者： (美)Ross L.Finney Maurice d.weir Frank R.Giordano[]

来源：畅想之星图书光盘版（南... 评论

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畅想之星图书光盘版（南通市图书馆镜像）

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Journal of Environmental Sciences 2011年第7期23卷 1072-1078页

作者： david G. Kelly Ron d. weir Steven d. White Analytical Sciences Group & SLOWPOKE-2 Facility at RMC Department of Chemistry and Chemical Engineering Royal Military College of Canada 11 General Crerar Crescent

The Royal Military College of Canada, located on the north eastern shore of Lake Ontario, possesses an abundance of copper roofs and lacks surface water treatment prior to discharge into Lake Ontario. Rainwater, roof runoff and soil samples were collected and analyzed for copper and other parameters. Copper was consistently detected in runoff samples with average concentrations of 3200 ± 2100 μg/L. Multivariable linear regression analysis for a dependant copper runoff concentration yielded an adjusted R 2 value of 0.611, based on an independent variable model using minimum temperature, maximum temperature, total precipitation, and wind speed. Lake water samples taken in the vicinity of storm water outfalls draining areas with copper roofs ranged from 2.0 to 40 μg/L copper. Such data exceed the 2.0 μg/L Canadian Water Quality Guidelines for the Protection of Aquatic Life as outlined by the Canadian Council of Ministers of the Environment （CCME）. Analysis of raw, filtered and digested forms suggested that the majority of copper present in runoff and lake water samples was in a dissolved form. The majority of soils taken in this study displayed copper concentrations below the 63 μg/g CCME residential/parkland land use limits. These findings suggested that ion exchange processes between runoff water and soil do not occur to a sufficient extent to elevate copper levels in soil. It may therefore be concluded that the eventual fate of copper, which is not discharged via storm water outfalls, is lost to the water table and Lake Ontario through the sub-soil.

关键词： copper roof runoff Lake Ontario Canadian water quality guidelines for the protection of aquatic life

Bone tissue engineering via nanostructured calcium phosphate biomaterials and stem cells

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Bone Research 2014年第3期2卷 139-151页

作者： Ping Wang Liang Zhao Jason Liu Michael d weir Xuedong Zhou hockin h K Xu Biomaterials & Tissue Engineering division Department of Endodontics Prosthodontics and Operative Dentistry University of Maryland Dental School Baltimore MD 21201 USA State Key Laboratory of Oral diseases West China Hospital of Stomatology Sichuan University department of Orthopaedic Surgery Nanfang Hospital Southern Medical University Mechanical Engineering department University of Maryland Baltimore County Baltimore MD 21250 USA Center for Stem Cell Biology and Regenerative Medicine University of Maryland School of Medicine Baltimore MD 21201 USA

Tissue engineering is promising to meet the increasing need for bone regeneration. Nanostructured calcium phosphate （CAP） biomaterials/scaffolds are of special interest as they share chemical/crystallographic similarities to inorganic components of bone. Three applications of nano-CaP are discussed in this review： nanostructured calcium phosphate cement （CPC）; nano-CaP composites; and nano-CaP coatings. The interactions between stem cells and nano-CaP are highlighted, including cell attachment, orientation/ morphology, differentiation and in vivo bone regeneration. Several trends can be seen：（i） nano-CaP biomaterials support stem cell attachment/proliferation and induce osteogenic differentiation, in some cases even without osteogenic supplements; （ii） the influence of nano-CaP surface patterns on cell alignment is not prominent due to non-uniform distribution of nano-crystals; （iii） nano-CaP can achieve better bone regeneration than conventional CaP biomaterials; （iv） combining stem cells with nano-CaP accelerates bone regeneration, the effect of which can be further enhanced by growth factors; and （v） cell microencapsulation in nano-CaP scaffolds is promising for bone tissue engineering. These understandings would help researchers to further uncover the underlying mechanisms and interactions in nano-CaP stem cell constructs in vitro and in vivo, tailor nano-CaP composite construct design and stem cell type selection to enhance cell function and bone regeneration, and translate laboratory findings to clinical treatments.

关键词： CPC Bone tissue engineering via nanostructured calcium phosphate biomaterials and stem cells stem

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加压湿法冶金的新进展

矿产综合利用 1987年第3期 75-83页

作者： d.R.weir 丁其光

加压湿法冶金是指工艺过程中在100kPa以上的压力下进行的那一部分。因此,一般地说,使用加压湿法冶金的原因是,要

关键词：压煮器底流浓密机异重流增稠器选矿机械湿法冶金黄铁矿精矿加压氧化难浸金矿氰化浸出