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.

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.

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.

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.

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.

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.

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。

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。

对比分析玻璃离子水门汀与复合树脂填充法治疗后牙牙体缺损的效果

目的 :对比分析玻璃离子水门汀(glass ionomer cement, GIC)与复合树脂(composite resin, CR)填充法治疗后牙牙体缺损的效果。方法 :回顾性分析80例后牙牙体缺损患者病例资料,根据不同填充方案分为对照组(n=40)和观察组(n=40),对照组接受GIC填充法,观察组接受CR填充法。随访2年后比较两组填充效果、美观度、咀嚼功能和不良事件发生情况。结果 :观察组填充成功率高于对照组(62.5%vs 40.0%),不良事件发生率低于对照组(5.0%vs 25.0%);修复后,两组咀嚼功能显著升高,且观察组咀嚼功能、美观度评分均高于对照组(均P <0.05)。结论 :与GIC比较,RC填充法治疗后牙牙体缺损可提高填充成功率,改善患者咀嚼功能,提高美观度。

球磨改性的氟化石墨烯/玻璃离子水门汀的力学性能、抗菌效果和生物相容性研究

目的:评价向玻璃离子水门汀(GICs)加入氟化石墨烯(FG)后的力学性能、抗菌效果和生物相容性。方法:将FG按照质量分数为1%、2%、4%添加至普通GICs中,对照组不含FG。按试验要求制备试样。利用万能试验机和维氏硬度计测试试样的压缩强度、径向拉伸强度和显微硬度。用薄膜密贴法评价试样对金黄色葡萄球菌和大肠杆菌的抗菌效果。将复合材料与L929细胞共培养,1、3、5 d时CKK-8实验评价细胞毒性。结果:与GICs相比,FG/GICs复合材料表现出较高的压缩强度、径向拉伸强度和显微硬度(P<0.05),更强的抗菌效果。CCK8实验显示,FG/GICs复合材料对L929细胞无明显的毒性。结论:在不影响生物相容性的情况下,FG能增强GICs的力学性能和抗菌效果。

A High-Strength Cement System for Improved Dental Restoratives

We have developed and studied a novel high-strength glass-ionomer cement system composed of poly(acrylic acid) with different molecular architectures. These poly(acrylic acid) polymers were synthesized via ATRP technique. The effects of arm number and branching on reaction kinetics, viscosity, and mechanical strengths of the formed polymers and cements were evaluated. The results showed that unlike the star-shaped polymer synthesis both hyperbranched and star-hyperbranched polymers syntheses proceed slowly at the early stage but accelerate at the later stage. The higher the arm number and initiator concentration are, the faster the ATRP reaction was. It was also found that the higher the arm number and branching that the polymer had, the lower the viscosity of the polymer aqueous solution is and the lower the mechanical strengths of the formed cement are. The mechanical strengths of three synthesized polymers-composed experimental cements were very similar to each other but much higher than those of Fuji II LC. The experimental cements were 31% - 53% in CS, 37% - 55% in compressive modulus, 80% - 126% in DTS, 76% - 94% in FS, 4% - 21% in FT and 53% - 96% in KHN higher than Fuji II LC. For wear test, the experimental cements were only 5.4% - 13% of abrasive and 6.4% - 12% of attritional wear depths of Fuji II LC in each wear cycle. The one-month aging study also showed that all the experimental cements increased their CS continuously during 30 days, unlike Fuji II LC.

The Effect of ZnO on the Physicochemical and Mechanical Properties of Aluminosilicate Dental Cements

In this study,the effect of the addition of various amounts of ZnO(0,1,2,and 3 wt.%)to aluminosilicate bioactive glass(BGs)network(SiO_(2)-Al_(2)O_(3)-P_(2)O_(5)-CaF_(2)-CaO-K_(2)O-Na_(2)O)on the mechanical properties of the fabricated glass ionomer cement(GIC)samples was studied.The GIC samples were fabricated by mixing the synthesized aluminosilicate BGs with Riva-self cure liquid.The synthesized aluminosilicate glass was characterized using differential thermal analysis(DTA),X-Ray diffraction(XRD),Fourier-transform infrared spectroscopy(FTIR),and scanning electron microscopy(SEM).Besides,the mechanical properties of GICs were evaluated using Vickers microhardness and Diametral tensile strength(DTS)test.According to DTA analysis,the glass transition temperature(Tg)of aluminosilicate BGs was decreased from 575 to 525°C.According to the results,the aluminosilicate BGs with an amorphous state(~90%)and the grain size of 36μm were synthesized.Doping of the ZnO to glass network up to 3 wt.%could increase the amorphous phase up to 95%and decrease the grain size of the particles up to 28μm.The microhardness and DTS of the GIC samples containing the aluminosilicate BGs were about 677 Hv and 8.5 MPa,respectively.Doping of ZnO to the glass network increased the mentioned values up to 816 Hv and 12.1 MPa,respectively.

调拌纸板厚度对玻璃离子水门汀抗压强度的影响

目的:探讨调拌纸板厚度变化对玻璃离子水门汀抗压强度的影响。方法:在相同的实验条件下,分别采用60、40、20、1张纸的纸板(P60、P40、P20、P1)对3种不同的玻璃离子水门汀进行调拌,在其凝固后进行抗压强度检测,并用扫描电镜观察不同组别材料断面气泡形成情况。结果:(1)抗压强度:(1)ChemFil Superior玻璃离子材料(CF):P1组平均抗压强度最高,与P40、P60组相比差异有统计学意义(P=0.041、0.032);(2)而至富士IX GP玻璃离子材料(IX):P1组平均抗压强度最高,与P40、P60组相比差异有统计学意义(P=0.042、0.038);(3)Glaslonomer FX-Ⅱ玻璃离子材料(FX):P1组平均抗压强度最高,与P20、P40、P60组相比差异有统计学意义(P=0.031、0.040、0.041),其余各组间差异无统计学意义,三种材料均显示出随着调拌纸板厚度的下降,玻璃离子抗压强度逐渐升高,纸板厚度与玻璃离子抗压强度成高度线性负相关,CF、IX、FX相关系数分别为-0.927、-0.989、-0.892。(2)扫描电镜下观察:三种材料均显示P1组气泡最少。结论:采用1张纸的纸板调拌玻璃离子水门汀的气泡最少,并可以获得更高的抗压强度。