Setting kinetics and mechanical properties of flax fibre reinforced glass ionomer restorative materials

Regardless of the excellent properties of glass ionomer cements,their poor mechanical properties limit their applications to non-load bearing areas.This study aimed to investigate the effect of incorporated short,chopped and randomly distributed flax fibers（0,0.5,1,2.5,5 and 25 wt%） on setting reaction kinetics,and mechanical and morphological properties of glass ionomer cements.Addition of flax fibers did not significantly affect the setting reaction extent.According to their content,flax fibers increased the compressive（from 148 to 250 MPa） and flexure strength（from 20 to 42 MPa）.They also changed the brittle behavior of glass ionomer cements to a plastic one.They significantly reduced the compressive（from 3 to 1.3 GPa） and flexure modulus（from 19 to 14 GPa）.Accordingly,flax fiber-modified glass ionomer cements could be potentially used in high-stress bearing areas.

Effect of anti-biofilm glass–ionomer cement on Streptococcus mutans biofilms

Dental restorative materials with antimicrobial properties can inhibit bacterial colonization, which may result in a reduction of caries at tooth-filling interaction zones. This study aimed to develop antibacterial glass-ionomer cements （GIC） containing a quaternary ammonium monomer （dimethylaminododecyl methacrylate, DMADDM）, and to investigate their effect on material performance and antibacterial properties. Different mass fractions （0, 1.1% and 2.2%） of DMADDM were incorporated into the GIC. The flexure strength, surface charge density, surface roughness and fluoride release were tested. A Streptococcus mutans biofilm model was used. Exopolysaccharides （EPS） staining was used to analyze the inhibitory effect of DMADDM on the biofilm matrix. In addition, biofilm metabolic activity, lactic acid metabolism and the expression of glucosyltransferase genes g/fB, gtfC and gtfD were measured. GIC containing 1.1% and 2.2% DMADDM had flexural strengths matching those of the commercial control （P〉0.1）. DMADDM was able to increase the surface charge density but reduced surface roughness （P〈0.05）. The incorporation of 1.1% and 2.2% DMADDM elevated the release of fluoride by the GIC in the first 2 days （P〈0.05）. The novel DMADDM-modified GIC significantly reduced biofilm metabolic activity （P〈 0.05） and decreased lactic acid production （P〈 0.05）. The quantitative polymerase chain reaction （qPCR） results showed that the expression of gtfB, g/fC and gtfD decreased when mass fractions of DMADDM increased （P〈0.05）. EPS staining showed that both the bacteria and EPS in biofilm decreased in the DMADDM groups. The incorporation of DMADDM could modify the properties of GIC to influence the development of S. mutans biofilms. In this study, we investigated the interface properties of antibacterial materials for the first time. GIC containing DMADDM can improve material performance and antibacterial properties and may contribute to the better management of secondary caries.

Anti-biofilm Effect of Glass Ionomer Cements Incorporated with Chlorhexidine and Bioactive Glass

The effect of glass ionomer cement and resin-modified glass ionomer cement incorporated with chlorhexidine and bioactive glass on antimicrobial activity and physicochemical properties were investigated. The experimental results showed that groups incorporated with 1% chlorhexidine exhibited a significant reduction of optical density values of the bacterial suspension and increased the degradation of Streptococcus mutans biofilm. However, groups incorporated with 10% bioactive glass did not affect the optical density values and the biofilm formation. The mechanical properties of the materials and the polymerization were not influenced by the addition of chlorhexidine. Nevertheless, the compressive strength was lower when the materials were incorporated with bioactive glass. It can be concluded that glass ionomer cements incorporated with chlorhexidine can maintain its mechanical properties as well as reduce early S mutans biofilm formation. Controlled release/sustained release technology may be required to optimize the antibacterial activity of glass ionomer cements incorporated with bioactive glass.

The Setting Chemistry of Glass Ionomer Cement

The setting chemistry of glass ionomer cement was imestigated by using mechanical determination of compressive strength at predetermined intervals,and measurement of structure changes of correspondling fracture sample by means of IR spectra and differential scanning calorimetry（DSC）.Zinc polycarboxylate cement was used as a comparison sample.The compressive strength of glass ionomer cement（GIC） increases with aging.IR spectra and DSC of corresponding fracture sample show the structure changes of the matrix and interface layer comprising of silica gel during the predetermined intervals studied.however,no significant changes occur in the zinc polycarxyolate cement.Hence the structure changes of the matrix and/or interface layer are responsible for compressive strength increasing with aging.The structure changes include the crosslink density,the ratio of complex form to ionic form,the content ratio of Al-PAA to Ca-PAA,the forming and maturing process of the interface layer comprising of silica gel.

Short-term Mechanical Properties of Glass Ionomer Cement

The setting reaction of glass ionomer cement was studied by analyzing and comparing the short-tem mechanical properties of set cement stored in silicone oil, air and distilled water respectively at different temperatures. For the set cement stored at 37 ℃, the strength of the sample in the air reached the maximum value after 24 h, then decreased to about 210 MPa and kept steady. The strength of the sample in water increased continuously and slowly, however, the increasing rate of sample stored in silicone oil was higher than that in the water. At 20 ℃, the increasing rate of compressive strength for sample in air was higher than those in silicone oil and water. The diffusion speed and maintenance of water has significant effects on the mechanical properties of glass ionomer cements.

Studies on electrical and thermal properties of dental glass ionomer cement

A commercially available dental Glass Ionomer Cement (GIC) was studied after setting at room temperature (300 K) to understand its DC electrical conductivity, dielectric and thermal properties. The dental GIC’s are supposed to have free mobile charge carriers like F- ions. Interestingly this material loses its conductivity above 80°C and behaves like a non-polar substance. The frequency dependent dielectric studies also indicate the loss of mobile charge carriers in the samples annealed at 80°C. The DSC and TGA studies indicate that the material loses H2O exothermically at 100°C. This is attributed to the onset of a secondary setting reaction.

Computational Study of the Formation Reaction of Polyacid Precursors of Glass-Ionomer Materials

The formation of polyacids in a glass-ionomer cement was computationally modeled. The polyacid modelled is an oligomer made up of three molecules: acrylic acid, itaconic acid and an additional molecule that acts as a spacer group between the previous two. Acryloyl and meta-acryloyl derivatives of some amino acids and related molecules such as N-vinyl pyrrolidone and N-vinyl caprolactam were used as spacer groups. Some of these molecules have been previously used experimentally as spacer groups. In this work the spacer behaviour of 15 different molecules was investigated. To our knowledge, this is the first computational attempt to model some promising molecules to be incorporated into glass-ionomer dental cements. The results revealed the best structural arrangement for the investigated molecules.

A PQAS-containing glass-ionomer cement for improved antibacterial function

The novel non-leachable poly (quaternary ammonium salt) (PQAS)-containing antibacterial glass- ionomer cement has been developed. Compressive strength (CS) and S. mutans viability were used as tools for strength and antibacterial activity evaluations, respectively. All the specimens were conditioned in distilled water at 37?C prior to testing. Commercial glass-ionomer cement Fuji II LC was used as control. With PQAS addition, the studied cements showed a reduction in CS with 25-95% for Fuji II LC and 13-78% for the experimental cement and a reduction in S. mutans viability with 40-79% for Fuji II LC and 40-91% for the experimental cement. The experimental cement showed less CS reduction and higher antibacterial activity as compared to Fuji II LC. The long-term aging study indicates that the cements are permanently antibacterial with no PQAS leaching. It appears that the experimental cement is a clinically attractive dental restorative that can be potentially used for long- lasting restorations due to its high mechanical strength and permanent antibacterial function.

Preparation and evaluation of a novel antibacterial glass-ionomer cement

A novel antibacterial glass-ionomer cement has been developed. Compressive strength (CS) and S. mutans viability were used to evaluate the mechanical strength and antibacterial activity of the formed cement. Compressive yield strength (YS), modulus (M), diametral tensile strength (DTS) and flexural strength (FS) were also determined. All the formulated antibacterial cements showed a significant antibacterial activity, accompanying with an initial CS reduction. The effect of the synthesized antibacterial polymer loading was significant. Increasing loading from 1% to 20% significantly decreased the S. mutans viability from 3% to 50% and also reduced the initial CS (325 MPa) of the formed cements from 19% to 75%. The cement with 5% antibacterial polymer loading showed 142 MPa, 6.9 GPa, 224 MPa, 52 MPa, and 62 MPa in YS, M, CS, DTS and FS, respectively, as compared to 170, 7.1, 325, 60 and 87 for the experimental cement without antibacterial polymer addition and 141, 6.9, 236, 42 and 53 for Fuji II LC. It was also found that the chlorine-containing antibacterial cement showed better CS values than the bromine-containing cement, with no significant difference in antibacterial activity. The antibacterial cement also showed a similar antibacterial activity to Streptococcus mutans, lactobacillus, Staphylococcus aureus and Staphylococcus epidermidis. The human saliva did not affect the antibacterial activity of the cement. The thirty-day aging study indicates that the cements may have a long-lasting antibacterial function.

The Mechanism of Formation of Glass-Ionomer Cement: A Theoretical Study

A resin-modified glass-ionomer cement (RMGIC) was studied from a computational point of view. We suggest terpolymer formation by reaction of fixation through a combination of acrylic acid (AA), itaconic acid (IA) and an aminoacid derivative (AAD) in different positions. We found that AAD-AA-IA is thermodynamically more stable, but AA-IA-AAD is the combination which can react with glycidyl methacrylate (GM) to form a grafted polymer with two pendant methacrylate groups which can be used later in the process of light-curing. A RMGIC contains a glass powder of calcium-fluoroaluminosilicate acting as the source of cross linking, and for this reason, we have optimized two intramolecular Al3+ tricarboxylate complexes (salt-bridges) formed from the most stable grafted polymers. A possible reaction mechanism for the addition of (GM) to copolymer is proposed.

MICROLEAKAGE OF CLASS V RESIN-MODIFIED GLASS IONOMER CEMENT AND COMPOMER RESTORATIONS IN VITRO

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.

The Evaluation of a Resin-modified Glass Ionome Cement for Bonding Orthodontic Brackets

To evaluate the shear bond strength（SBS） and bond failure interface after the debonding of orthodontic brackets with a resin-modified glass ionomer cement（RMGIC） under six bonding conditions, 140 premolar teeth were randomly divided into seven groups. The brackets of all groups, except for control group, were bonded using a RMGIC. The teeth were debonded using a universal testing machine. The shear bond strength, adhesive remnant index （ARI） and enamel fracture were examined for each debonding. A significant difference existed in SBS under wet and dry conditions in two groups of Fuji Ortho LC. Different degree of enamel fracture was seen in groups of Fuji Ortho LC（dry/37% phosphoric acid treated） after debonding. Bond failed predominantly at the enamel-adhesive interface, except for phosphoric acid treated groups. The RMGIC achieve a clinically effective adhesion in orthodontics under different bonding conditions.

燃料电池热压过程中催化层的结构演变机制

聚合物电解质燃料电池膜电极组件的制备过程,特别是热压过程会对其发电性能产生较大的影响,但目前现有研究对热压过程中催化层内部结构演变机制的认识还不充分。为此,通过正交实验、表征和电学性能测试,探究热压温度和热压时间对催化层结构变化和电池性能的影响。基于扫描电子显微镜数据可知热压处理会压缩催化层内部孔结构且热压温度和热压时间的增加会加剧这种压缩效应,这与孔径分布分析结论保持一致;另外还发现主要是次级孔被压缩。上述现象证实了催化层内离聚物在越过玻璃化转变温度后的软化行为。此外,电学性能测试表明热压处理导致传质阻抗显著增加,其中经过热压温度为160℃,且热压时间为9 min处理的催化层具备最大传质阻抗增加量,其传质阻抗为直接喷涂法制备催化层传质阻抗的2.77倍,这主要是催化层内孔结构被压缩的结果。研究结果揭示了催化层内离聚物热响应行为对催化层结构演变的影响,并为优化热压过程的关键参数提供了理论支撑。

铒激光预处理对牙本质、牙釉质粘结强度及CAD/CAM玻璃陶瓷嵌体修复牙体缺损边缘微渗漏的影响

目的:探讨铒激光预处理对牙本质、牙釉质粘结强度及CAD/CAM玻璃陶瓷嵌体修复牙体缺损边缘微渗漏的影响。方法:收集2020年1月—2023年1月口腔外科门诊拔除的新鲜、无龋坏变色、无隐裂智齿62颗,根据预处理方式不同,随机分为铒激光组和磷酸组,每组31颗,每组再随机分为2份,分别用于粘结强度测试(16颗)和微渗漏测试(15颗)。比较2组牙釉质、牙本质抗剪切粘结强度和微渗漏程度及微渗漏评分分布情况。采用SPSS 17.0软件包对数据进行统计学分析。结果:铒激光组牙釉质、牙本质抗剪切粘结强度显著高于磷酸组(P<0.05);铒激光组侧壁、龈壁微渗漏程度显著低于磷酸组(P<0.05),铒激光组侧壁微渗漏评分主要为1分和2分,磷酸组侧壁微渗漏评分主要为2分,2组侧壁微渗漏评分分布相比,差异有统计学意义(P<0.05);铒激光组龈壁微渗漏评分主要为1分和2分,磷酸组龈壁微渗漏评分主要为2分和3分,2组龈壁微渗漏评分分布相比,差异有统计学意义(P<0.05)。结论:铒激光预处理可提高瓷嵌体与牙本质、牙釉质粘结强度,同时还可减少CAD/CAM玻璃陶瓷嵌体微渗漏,增强嵌体边缘密合性。

光敏树脂、加强型玻璃离子、银汞合金填充治疗乳牙龋齿病的效果比较

目的:比较光敏树脂、加强型玻璃离子、银汞合金填充治疗乳牙龋齿病的效果。方法:选择乳牙龋齿病病人125例作为研究对象,依据填充治疗方法的不同分成A、B、C 3组。A组43例(106颗龋齿)采用光敏树脂进行填充治疗,B组42例(102颗龋齿)采用加强型玻璃离子进行填充治疗,C组40例(98颗龋齿)采用银汞合金进行填充治疗。比较各组每颗患牙填充时间、牙本质过敏反应发生率、填充材料存留情况及龋齿复发情况。结果:A组每颗患牙填充时间短于B组和C组(P<0.05),B组每颗患牙填充时间短于C组(P<0.05)。A组填充治疗后1周牙本质过敏反应发生率低于B组和C组(P<0.05),C组填充治疗后1周牙本质过敏反应发生率低于B组(P<0.05)。A组随访1年填充材料完整存留率高于B组和C组(P<0.05),B组与C组随访1年填充材料完整存留率差异无统计学意义(P>0.05)。A组与C组随访6个月、随访1年龋齿复发率均低于B组(P<0.05),A组与C组随访6个月、随访1年龋齿复发率差异无统计学意义(P>0.05)。结论:与加强型玻璃离子、银汞合金填充治疗相较,光敏树脂填充治疗乳牙龋齿病,具有较短的填充用时、更低的牙本质过敏反应发生率、更高的充填材料存留率、较低的龋齿复发率。

Improvement of enamel bond strengths for conventional and resin-modified glass ionomers: acid-etching vs. conditioning

Objective:This study deals with the effect of phosphoric acid etching and conditioning on enamel micro-tensile bond strengths(μTBSs)of conventional and resin-modified glass ionomer cements(GICs/RMGICs).Methods:Forty-eight bovine incisors were prepared into rectangular blocks.Highly-polished labial enamel surfaces were either acid-etched,conditioned with liquids of cements,or not further treated(control).Subsequently,two matching pre-treated enamel surfaces were cemented together with one of four cements[two GICs:Fuji I(GC),Ketac Cem Easymix(3M ESPE);two RMGICs:Fuji Plus(GC),RelyX Luting(3M ESPE)]in preparation forμTBS tests.Pre-treated enamel surfaces and cement-enamel interfaces were analyzed by scanning electron microscopy(SEM).Results:Phosphoric acid etching significantly increased the enamelμTBS of GICs/RMGICs.Conditioning with the liquids of the cements produced significantly weaker or equivalent enamelμTBS compared to the control.Regardless of etching,RMGICs yielded stronger enamelμTBS than GICs.A visible hybrid layer was found at certain enamelcement interfaces of the etched enamels.Conclusions:Phosphoric acid etching significantly increased the enamelμTBSs of GICs/RMGICs.Phosphoric acid etching should be recommended to etch the enamel margins before the cementation of the prostheses such as inlays and onlays,using GICs/RMGICs to improve the bond strengths.RMGICs provided stronger enamel bond strength than GICs and conditioning did not increase enamel bond strength.

玻璃离子水门汀在后牙邻面龋齿治疗中的应用价值及对患者咀嚼功能的影响

目的探讨玻璃离子水门汀在后牙邻面龋齿治疗中的应用价值。方法选取2022年1月至2023年9月赣州市妇幼保健院收治的76例后牙邻面龋齿患者作为研究对象,按照密闭信封法将其分为对照组(n=38)与研究组(n=38)。对照组使用银汞合金填充龋洞,研究组使用玻璃离子水门汀填充龋洞。比较两组的修复效果,比较两组治疗前后的牙龈指数(GI)、龈沟出血指数(SBI)、菌斑指数(PLI)附着丧失水平(CAL)及改良曼恩咀嚼协调评估量表(MASA)评分,并比较两组的不良反应发生率。结果研究组的修复有效率高于对照组,差异有统计学意义(P<0.05)。治疗前,两组的各项牙周状况评分的比较,差异无统计学意义(P>0.05)。治疗后,两组患者的SBI、PLI及CAL评分均高于本组治疗前,但研究组的SBI、PLI及CAL评分均低于对照组,差异有统计学意义(P<0.05);两组患者治疗前后的GI评分比较,差异无统计学意义(P>0.05)。治疗前,两组患者的MASA评分比较,差异无统计学意义(P>0.05)。治疗后,两组患者的MASA评分均低于本组治疗前,且研究组评分低于对照组,差异有统计学意义(P<0.05)。两组患者的不良反应总发生率比较,差异无统计学意义(P>0.05)。结论在后牙邻面龋齿治疗中,玻璃离子水门汀应用价值显著,能够提高修复有效率,改善牙周指标,并提高咀嚼功能,且不会增加不良反应风险。

Influence of Aging and 2-hydroxyethyl-methacrylate Content on the Color Stability of Experimental 2-hydroxyethyl-methacrylate-added Dental Glass Ionomers

Color stability of dental resin modified glass ionomer （RMGI） has been a challenge to dentistry; therefore, systematic changes in 2-hydroxyethyl methacrylate （HEMA） content were performed experimentally to find an idea to enhance the color stability. Changes in color （△E＊ab） and color coordinates （△L＊, △a＊ and △b＊） of experimental 10-50 wt pct HEMA-added dental glass ionomers （HAGIs） and corresponding RMGIs were determined after 5000 cycles of thermocycling. Color changes of HAGIs were not influenced by the HEMA content while △L＊, △a＊ and △b＊ values were influenced by the HEMA content. Color stability of 30% or 40% HEMA-added HAGIs was not different from those of the commercial RMGIs. Since the influence of HEMA itself on the color stability of HAGIs was limited, compositional modification to increase the color stability of these materials should be developed.

Filtek Z350XT流体树脂联合玻璃离子水门汀修复龈下深形牙体楔状缺损的疗效分析

目的探讨Filtek Z350XT流体树脂联合玻璃离子水门汀修复龈下深形牙体楔状缺损(WSD)的疗效。方法选择2021年1月至2022年6月南昌市第三医院口腔科接诊的120例龈下深形牙体WSD患者,按随机数字表法分为实验组(n=60)和对照组(n=60)。实验组采用玻璃离子水门汀垫底Filtek^(TM)Z350XT流体树脂充填,对照组采用光固化氢氧化钙垫底Filtek^(TM)Z350XT流体树脂充填。比较两组牙龈炎性反应、充填成功率、牙齿敏感状态、牙齿功能状态、并发症。结果两组充填成功率对比,无统计学差异(P>0.05);填充后两组牙颜色及咀嚼功能满意度评分、肿瘤坏死因子-α(TNF-α)、白细胞介素-1β(IL-1β)、天门冬氨酸氨基转移酶(AST)检测值均高于填充前(P<0.05),两组充填前与充填后牙颜色及咀嚼功能满意度、IL-1β、TNF-α、AST比较,无统计学差异(P>0.05);充填后两组牙敏感率均低于充填前(P<0.05),而两组充填后牙敏感率与并发症发生率对比,无统计学差异(P>0.05)。结论Filtek Z350XT流体树脂联合玻璃离子水门汀修复龈下深形牙体WSD的效果及安全性与光固化氢氧化钙相当。

高强度玻璃离子无创伤修复技术治疗小儿乳牙龋的临床效果

目的:探究应用高强度玻璃离子无创伤修复技术治疗小儿乳牙龋的临床效果。方法:选取2021年4月—2023年8月临沂市兰山区人民医院收治的小儿乳牙龋患儿108例为研究对象,根据随机数字表法分为对照组(n=54,低速轮涡转修复技术治疗)与试验组(n=54,高强度玻璃离子无创伤修复技术治疗)。比较两组治疗时间与治疗依从性、治疗效果与牙齿恢复时间、牙齿功能评分。结果:试验组治疗时间短于对照组,治疗依从性高于对照组,差异有统计学意义(P<0.05);试验组总有效率高于对照组,牙齿恢复时间短于对照组,差异有统计学意义(P<0.05);治疗后,两组牙齿咀嚼功能、发声能力、美观度评分均高于治疗前,试验组高于对照组,差异有统计学意义(P<0.05)。结论:应用高强度玻璃离子无创伤修复技术治疗小儿乳牙龋可取得良好效果,能提高患儿治疗依从性,缩短治疗时间,加速牙齿恢复,改善牙齿咀嚼、发声、美观等功能。