Effects of postcuring and water sorption on the mechanical properties of composite dental restorative materials

Four commercial dental restorative composites with different filler contents, were tested for the effects of postcuring and water sorption on elastic modulus, compressive strength and ultimate strain. Large variations in mechanical properties were seen; water sorption plasticizes the matrix, causing loss of low molecular weight substances.     

纤维树脂桩核修复体力学性能与不同牙体剩余量的关系

背景：牙体组织剩余量与纤维树脂桩核修复体的抗折强度密切相关。 目的：采用体外应力分析方法比较不同牙体残余量对纤维树脂桩核修复体抗疲劳强度的影响。 方法：将36颗离体人下颌单根管前磨牙随机均分为4组,进行牙根管预备与填充后,A组平齐基准平面横断磨除冠部牙体;B组,牙冠近远中斜形损耗,远端牙本质领圈高度2 mm,逐渐减少到近中端时牙本质领圈高度为0 mm;C组,牙冠横行缺失,留2 mm健康牙本质;D组,保留完整冠部牙体组织。各组常规桩道预备后进行黏结处理,将Para post fiber lux 玻璃纤维桩置入桩道内,采用动态力学加载设备对试件进行加载。 结果与结论：4组荷载力值大小为D组> C组> B组> A组,组间两两比较差异有显著性意义(P < 0.05)。实验样本折裂形式大致可分为牙冠斜行折裂、牙颈部横行折裂、牙颈部斜行折裂及牙根折裂等4种。A组发生牙颈部横行折裂7颗、牙颈部斜行折裂2颗;B组发生牙冠斜行折裂4颗、牙颈部斜行折裂5颗;C组发生牙颈部斜行折裂6颗、牙根中部折裂3颗;D组发生牙颈部斜行折裂7颗、牙根中部折裂2颗。表明当牙体残余量较多时,牙齿受到的咬合应力也会从颈缘转移到根部,整体水平也随着减低,纤维树脂桩核修复体的强度也会随着增强,因此在临床实践中应尽可能多保存牙体组织。中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程     

Preparation and antibacterial properties of O-carboxymethyl chitosan/lincomycin hydrogels

In this study, O-carboxymethyl chitosan (O-CMCS) was synthesized from chitosan and monochloroacetic acid. Then O-CMCS hydrogel was prepared by 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) in which the lincomycin was packaged. The Fourier transform infrared spectrum and scanning electron microscopy were adopted to characterize the structure and morphology of the product. The influences of dosage of EDC/NHS and concentration of O-CMCS on the swelling properties of the hydrogels were investigated. The hydrogels performed good swelling capacities and obvious pH-sensitive properties. The antibacterial activities of the hydrogels were tested against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus). Compared with pure O-CMCS hydrogels, the antibacterial activities of O-CMCS/lincomycin hydrogels were significantly improved with the increase in the concentration of lincomycin against E. coli and S. aureus. With the increase in dosage of crosslinking agent or concentration of O-CMCS, the antibacterial activities both decreased gradually against the two bacteria. O-CMCS/lincomycin hydrogel was expected to be used for antibacterial material in view of its significant antibacterial activities.     

Structure and properties of methacrylate based dental restorative materials

The chemistry and structure of the dimethacrylate resins and the nature of the filler systems in dental composite resins are reviewed in relation to their influence on the setting behaviour, dimensional stability, aesthetics, fracture behaviour and adhesive potential. It is clear that a deeper understanding of the structure of the polymeric matrix and the mechanism of clinical wear is required. As a result of ongoing research in this area and with the development of dentine adhesives, the future prospects of composite resins are encouraging.     

Investigation of double bond conversion,mechanical properties,and antibacterial activity of dental resins with different alkyl chain length quaternary ammonium methacrylate monomers (QAM)

In order to endow dental resin with antibacterial activity, a series of antibacterial quaternary ammonium methacrylate monomers (QAM) with different substituted alkyl chain length (from 10 to 18) were incorporated into commonly used 2,2-bis[4-(2′-hydroxy-3′-methacryloyloxy-propoxy)-phenyl]propane (Bis-GMA)/triethyleneglycol dimethacrylate (TEGDMA) (50?wt/50?wt) dental resin as immobilized antibacterial agents. Double bond conversion (DC), flexural strength (FS) and modulus (FM), and young and mature biofilms inhibition effectiveness of prepared dental resins were studied and Bis-GMA/TEGDMA without QAM was used as reference. Results showed that there was no significant difference on DC, FS, and FM between copolymer with and without 5?wt% QAM. Substituted alkyl chain length of QAM had no influence on DC, FS, and FM of copolymer, but had influence on antibacterial activity of copolymer. Antibacterial activity of copolymer increased with increasing of substituted alkyl chain length of QAM, and the sequence followed as 5%C10?<?5%C11≈5%C12?<?5%C16≈5%C18. Copolymers containing C18 and C16 had the best inhibition effectiveness on both young biofilm and mature biofilm, copolymers containing C12 and C11 only had inhibition effectiveness on young biofilm and copolymer containing C10 had none inhibition effectiveness on neither young biofilm nor mature biofilm.     

Characterization and inhibitory effect of antibacterial dental resin composites incorporating silver-supported materials.

Resin composites with antibacterial activity may be useful for preventing the secondary caries frequently seen around restorations. The purposes of this study were to investigate antibacterial light-activated dental resin composites incorporating each of two silver-supported antibacterial materials and evaluate their long-lasting inhibitory effect against Streptococcus mutans. Two types of silver-supported antibacterial materials, Novaron (N) and Amenitop (AM) were used. These antibacterial materials were incorporated into TEGDMA-UDMA-based light-activated resin composites, and the antibacterial activities and mechanical properties of these composites, and also the release of silver ions, were examined. Two silver-supported antibacterial materials inhibited the growth of the major oral pathogen S. mutans. The minimum inhibitory concentration in suspensions of N and AM against S. mutans was 40 microg/mL and 30 microg/mL, respectively. Composites incorporating 5 wt % (N-5) or more of Novaron and 7 wt % (AM-7) or more of Amenitop inhibited the growth of S. mutans after immersion in water for 6 months. There was no or extremely little release of silver ions from the N-5 and AM-7 composites after 1 day or after 6 months of immersion in water. No significant difference in either compressive or flexural strength was observed between the control and the N-5 composites after 1 day or after 6 months of storage in water. However, for the AM-5 composite, there was a significant difference in both strength parameters between the two immersion periods. These results indicate that a light-activated dental resin composite incorporating silver-supported antibacterial material such as Novaron may be useful clinically because of its long-lasting inhibitory effect against S. mutans and its favorable mechanical properties.     

Static and dynamic moduli of posterior dental resin composites under compressive loading

Dental resin composites are commonly used as restorative materials for dental treatment. To comprehend the static and dynamic moduli of dental resin composites, we investigated the mechanical behaviors of resin composites under static and dynamic loading conditions. Four commercially available resin composites for posterior restorations were evaluated. The percentages, by weight, of inorganic fillers of resin composites were examined by the ashing technique. The static compressive tests were undertaken with a constant loading speed of 1.0 mm/min using a computer-controlled INSTRON testing machine. The dynamic properties of composites were determined using the split Hopkinson pressure bar (SHPB) technique. When inorganic filler content was increased, a remarkable increase in the static modulus and dynamic modulus were observed. Furthermore, there was a strong relationship between the static modulus and dynamic modulus (r²=0.947). The SHPB technique clearly demonstrated the dynamic properties of composites, and was a useful technique for determining the mechanical behavior of composites under dynamic compressive loading.     

口腔纳米载银无机抗菌材料的抗菌性能

背景：纳米载银无机抗菌剂具有抗菌谱广、抗菌能力强等特点,是目前口腔无机抗菌材料研究的热点之一。 目的：研究纳米载银无机抗菌材料的抗菌性能及抗菌机制,为基础实验研究和临床应用提供参考信息。 方法：研究多种口腔纳米载银无机抗菌材料对常见病原菌如变形链球菌、白色念珠菌以及粘性放线菌等的抗菌性能,其中包括最低杀菌浓度以及抗菌率等,同时进行对比分析。并且研究纳米载银无机抗菌材料的抗菌机制,明确其优点与不足。 结果与结论：口腔纳米载银无机抗菌材料具有较广的抗菌谱,对变形链球菌、乳酸杆菌、粘性放线菌、白色念珠菌、牙龈卟啉单胞菌、金黄色葡萄球菌以及大肠埃希菌等均具有较强的抗菌性能,最低杀菌浓度较低,而抗菌率较高。但是同一纳米载银无机抗菌材料对不同的病原菌,其最低杀菌浓度不同,抗菌率也不同,而不同的纳米载银无机抗菌材料对同一病原菌的最低杀菌浓度也不相同,抗菌率也不同。     

Preparation of low shrinkage stress Bis-GMA free dental resin composites with a synthesized urethane dimethacrylate monomer

A new urethane dimethacrylate TMA was synthesized through a typical urethane reaction. TMA was used to replace 1,6-bis(methacryloxy-2-ethoxycarbonyl- amino)-2,4,4- trimethylhexane (UDMA) in UDMA based composite partially or totally to prepare TMA containing composites. Critical properties of TMA containing composites were investigated. 2,2-bis[4(2-hydroxy-3-methacryloy- propyloy)phenyl]propane (Bis-GMA) based and UDMA based composites were used as references. FT-IR and ¹H-NMR confirmed the structure of TMA. All of experimental dental resin composites had the similar double bond conversion (p?>?0.05). With a certain amount of TMA, TMA containing composites could have lower volumetric shrinkage (p?<?0.05) and shrinkage stress (p?<?0.05) than control groups. Water sorption, solubility, flexural strength and modulus of TMA containing composites were not worse than those of control groups. All of TMA containing composites and UDMA based composite had the same fracture toughness (p?>?0.05), which was higher than that of Bis-GMA based composite (p?<?0.05). TMA has potential as Bis-GMA substitute to prepare Bis-GMA free dental resin composites with low shrinkage stress.     

壳聚糖抑菌性能的研究进展

壳聚糖是一种天然碱性多糖,因其良好的生物相容性、抗微生物性、可降解性而被广泛应用于食品工程、医药行业、工业降解等领域。而对壳聚糖抑菌性的相关研究一直以来是其特性研究中的热点。本文回顾了从2000年至2018年国内外对壳聚糖抑菌性的研究情况,对其抑菌性影响因素及抑菌机制做了总结,提出了在抑菌性研究方面的问题和观点。以期为壳聚糖抑菌性进一步研究及应用提供理论基础和科学依据。     

Development of remineralizing, antibacterial dental materials

Light curable methacrylate dental monomers containing reactive calcium phosphate filler (monocalcium phosphate monohydrate (MCPM) with particle diameter of 29 or 90 μm) and β-tricalcium phosphate (β-TCP) at 1:1 weight ratio in a powder:liquid ratio (PLR) of 1:1 or 3:1 and chlorhexidine diacetate (0 or 5 wt.%), were investigated. Upon light exposure, approximately 90% monomer conversion was gained irrespective of the formulation. Increasing the PLR promoted water sorption by the set material, induced expansion and enhanced calcium, phosphate and chlorhexidine release. Concomitantly, a decline in compressive and biaxial flexural strengths occurred. With a reduction in MCPM particle diameter, however, calcium and phosphate release was reduced and less deterioration in strength observed. After 24 h, the remaining MCPM had reacted with water and β-TCP, forming, within the set materials, brushite of lower solubility. This provided a novel means to control water sorption, component release and strength properties. Measurable chlorhexidine release was observed for 6 weeks. Both diffusion rate and total percentage of chlorhexidine release decreased with lowering PLR or by adding buffer to the storage solutions. Higher chlorhexidine release was associated with reduced bacterial growth on agar plates and in a biofilm fermenter. In cell growth media, brushite and hydroxyapatite crystals precipitated on the composite material surfaces. Cells spread on both these crystals and the exposed polymer composite surfaces, indicating their cell compatibility. These formulations could be suitable antibacterial, biocompatible and remineralizing dental adhesives/liners.     

Tear and rupture of elastomeric dental impression materials

The curing time dependence of the tear energy, tensile strength and ultimate extension ratio of a range of characterized elastomeric impression materials was investigated. This variation of tensile strength and ultimate extension ratio was correlated with the development of the network structure. The tear energy showed only minor changes as the curing proceeded.     

牙科陶瓷树脂粘接研究进展

目前,牙科陶瓷材料因为具有极佳的光学性能而能为患者制作美学要求较高的修复体。陶瓷材料脆性较大,在许多临床条件下必须要依靠树脂粘接才能使全瓷修复体与基牙支持组织牢固地结合,从而使得修复体长期耐用。对牙科陶瓷树脂粘接系统的研究进展进行了概述。     

医用外固定型低温热塑性聚合物树脂材料的力学性能研究

利用动态力学分析仪和微型材料实验机分别对3种医用外固定型低温热塑性聚合物树脂材料A、B和C进行温度扫描和室温、不同应变率下的单轴拉伸实验,对比分析了3种材料力学性能的差异。研究表明:3种材料的玻璃化转变温度均在65℃左右,但材料C具有更宽的成型温度范围;3种材料的拉伸性能均体现出不同程度的率相关性,材料C具有更好的塑性。     

靶向光热抗菌纳米材料及其在伤口愈合中的应用研究进展EI北大核心CSCD

随着光热纳米材料的开发,基于近红外光激发的光热疗法在细菌感染的伤口治疗中显示出巨大的潜力。同时,为提高伤口感染部位的光热抗菌效果,降低光热对健康组织的高温损伤,靶向细菌策略也逐渐被应用于伤口的光热治疗中。本文分类介绍了常用的光热纳米材料及其靶向细菌策略,阐述了它们在光热抗菌治疗,尤其是在细菌感染伤口中的应用,分析了靶向光热抗菌疗法在伤口愈合应用中面临的难题与挑战,最后对靶向光热抗菌材料的发展提出展望,以期为伤口光热治疗提供一条新的思路。     

Loss into water of residual monomer from autopolymerizing dental acrylic resin

A study has been made of the loss of residual monomer from samples of autopolymerizing acrylic resin immersed in water. Diffusion of monomer out of the resin into the water could account for only part of the loss. It was shown that free radicals continue to be present in the acrylic after completion of cure, and it is postulated that the residual monomer in an autopolymerized acrylic resin may be removed by further polymerization at these sites, as well as by diffusion out of the resin. The implications of this hypothesis are discussed.     

医用复合树脂的新进展

随着医用复合树脂在口腔临床的广泛使用,对此类材料的研究也有了进一步的发展。作者介绍了近年来医用牙科复合树脂的组成、聚合方式的改进以及由此引起的物理、机械性能的改善。分析了树脂基质、无机填料的种类、含量、大小、形状、排列以及催化剂等因素对医用复合树脂性能的影响。提出了此类材料亟待解决的问题和研究的难点,为临床使用和研制更为理想的复合树脂材料提供一定的理论依据。     

SonicFill超声树脂对大鼠成牙本质细胞和牙髓微血管的影响

BACKGROUND: The mechanical properties of SonicFill ultrasonic resin are better than those of the traditional light-cured composite resin, but its effect on odontoblasts and dental pulp vessels is unclear.     

TiO2-xNx抗菌托槽的抑菌性能

 背景：有研究表明TiO_2-xN_x薄膜对变形链球菌、黏性放线菌及白色念珠菌具有良好的抗菌效果。目的：进一步评价TiO_2-xN_x薄膜托槽的抗菌性能。 方法：纳入10例正畸患者,将口内牙齿以上下中线分为左右两侧,分别粘接普通金属托槽和TiO_2-xN_x薄膜托槽,在矫治前、矫治后1,2,3,4周检测正畸菌斑指数、牙龈指数、龈沟出血指数及釉质脱矿指数。结果与结论：普通金属托槽组矫治后1,2,3,4周的正畸菌斑指数、牙龈指数、龈沟出血指数及釉质脱矿指数均高于矫治前(P < 0.05);TiO_2-xN_x薄膜托槽组矫治后3周的牙龈指数高于矫治前(P < 0.05),矫治后1,2,3周的龈沟出血指数高于矫治前(P < 0.05),矫治后2,3,4周的釉质脱矿指数高于矫治前(P < 0.05);TiO_2-xN_x薄膜托槽组矫治后1-4周的正畸菌斑指数、龈沟出血指数均低于普通金属托槽组(P < 0.05),矫治后2-4周的牙龈指数、釉质脱矿指数均低于普通金属托槽组(P < 0.05)。表明TiO_2-xN_x薄膜托槽具有较好的抗菌效果,可更好地控制和清除菌斑。中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

不同复合树脂材料硬度及黏结强度的比较

背景：与传统复合树脂材料相比,大块充填复合树脂材料具有增加光固化深度、降低聚合收缩率、简化临床操作程序等特点,但不同类型大块充填复合树脂材料的性能各异。 目的：分析4种复合树脂材料的硬度及黏结强度。 方法：取大块填充复合树脂Tetric EvoCeram BulkFill、SDR,以及传统复合树脂P60、Z350,检测4种复合树脂材料分别在2,3,4,5 mm光固化深度下的维氏显微硬度,以及4种复合树脂材料与牙本质间的剪切黏结强度。 结果与结论：不同光固化深度下的硬度顺序为：P60复合树脂>Z350复合树脂>Tetric EvoCeram BulkFill复合树脂> SDR复合树脂,4组间比较差异有显著性意义(P < 0.05);Tetric EvoCeram BulkFilll和SDR复合树脂光固化后的硬度未随着固化深度的增加而明显减小。Tetric EvoCream BulkFil和SDR复合树脂的剪切黏结强度显著高于P60和Z350复合树脂(P < 0.05)。表明大块充填树脂材料Tetric EvoCeram BulkFill和SDR的综合机械性能较高,并且具有较高的剪切黏结强度。 中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程