Cyclic Fatigue Resistance and Surface Roughness of Rotary NiTi Instruments after Simulated Clinical Use in Curved Root Canals - An Atomic Force Microscopy Study

Abstract Objective: To examine the cyclic fatigue resistance and surface topography of TruNatomy and ProTaper Gold nickel-titanium rotary files and evaluate the presence of alterations to surface topography following instrumentation in simulated curved canals. Material and Methods: Twenty-four nickel-titanium instruments, twelve each of TN and PTG file systems, were evaluated for cyclic fatigue resistance. The rotary files were rotated in a simulated root canal with standardized diameter, angle of curvature, and radius of curvature in a custom-made cyclic fatigue testing device until the instrument fracture occurred. The time to fracture for each instrument was recorded with a stopwatch; in seconds in each group. Fractured instruments were subjected to atomic force microscopy analysis measuring the average roughness and the root mean square values to investigate surface features of endodontic files. Mean values and standard deviation were calculated. Data were analyzed using the Mann-Whitney U test. Results: Time to fracture was marginally higher in PTG instruments than in the TN file systems. PTG files exhibited higher surface roughness when compared with TN files (p<0.05). Conclusion: TN file system had a higher cyclic fatigue resistance than PTG. Cyclic fatigue causing file breakage did affect the surface topography of the files. PTG files showed a higher surface porosity value than the TN files (AU).

The effect of ionizing radiation on properties of fluoride-releasing restorative materials

Abstract The purpose of this study was to evaluate the effect of ionizing radiation from high energy X-ray on fluoride release, surface roughness, flexural strength, and surface chemical composition of the materials. The study groups comprised five different restorative materials: Beautifil II, GCP Glass Fill, Amalgomer CR, Zirconomer, and Fuji IX GP. Twenty disk-shaped specimens (8x2 mm) for fluoride release and 20 bar-shaped specimens (25 x 2x 2 mm) for flexural strength were prepared from each material. Each material group was divided into two subgroups: irradiated (IR) and non-irradiated (Non-IR). The specimens from IR groups were irradiated with 1.8 Gy/day for 39 days (total IR = 70.2 Gy). The amount of fluoride released into deionized water was measured using a fluoride ion-selective electrode and ion analyzer after 24 hours and on days 2, 3, 7, 15, 21, 28, 35, and 39 (n = 10). The flexural strength was evaluated using the three-point bending test (n = 10). After the period of measurement of fluoride release, seven specimens (n = 7) from each group were randomly selected to evaluate surface roughness using AFM and one specimen was randomly selected for the SEM and EDS analyses. Data were analyzed with two-way ANOVA and Tukey tests (p = 0.05). The irradiation significantly increased fluoride release and surface roughness for Amalgomer CR and Zirconomer groups (p < 0.05). No significant change in flexural strength of the materials was observed after irradiation (p > 0.05). The ionizing radiation altered the amount of fluoride release and surface roughness of only Amalgomer CR and Zirconomer. The effect could be related to the chemical compositions of materials.

Effects of tubacin on membrane surface structure of BMSCs and mechanical property / 重庆医学

Objective To study the effect different concentrations of HDAC6 inhibitor tubacin on the proliferation,morphology and membrane surface ultrastructure of bone marrow mesenchymal stem cells(BMSCs).Methods Primary BMSCs were cultured.The P4 generation cells were taken for conducting the experiment.The different concentrations of tubacin were used to treat the cells fro 24 h.The cells survival rate was detected by MTT assay.The atomic force microscopy(AFM) was applied to observe the cellular morphology and surface ultramicrostructure and detect the mechanical property in different groups.Results The MTT results showed that low concentration of tubacin had the effect for promoting BMSC proliferation;the AFM results showed that compared with the control group,the height and width of BMSCs after treating by low concentration of tubacin,the membrane surface roughness was decreased and cellular hardness was increased.Conclusion Low concentration of tubacin can promote the BMSC proliferation,causes the changes of morphology and membrane surface ultramicrostructure,enhances the mechanical property and increases the cell implantation treatment efficiency.

Study on changes of elastic modulus of injured astrocytes detected by atomic force microscope / 天津医药

Objective To investigate changes of the elastic modulus of astrocytes induced by injury. Methods The astrocytes were isolated and extracted from the 2-day old SD rats, and identified by immunofluorescence staining with glial fiber acidic protein (GFAP) antibody. Cells were divided into control group and injured group. The injured group was astrocytes 6 h after being injured by the cell damage instrument. The control group was astrocytes without any injury. The elastic modulus in liquid phase was tested by atomic force microscope in two groups. Results were compared and analyzed between two groups. Results The purification rate of rat astrocytes was more than 95%. Six hours after the injury, the astrocytes were in disorder, and some of cell bodies were swelling. The mechanical topographic maps and force indentation curves were obtained. The elastic modulus of astrocytes was significantly increased in injured group compared with that of control group[(1 689±693) Pa vs. (724±283) Pa, P<0.01]. Conclusion The injury stimulus increases the elastic modulus of astrocytes, which provides theoretical basis for understanding intracranial physical microenvironment after traumatic brain injury in animal experiments.

Protective effect of calcium nanophosphate and CPP-ACP agents on enamel erosion

The aim of this study was to assess the effect of different remineralizing agents on enamel microhardness (KHN) and surface topography after an erosive challenge. Forty-eight human enamel specimens (4 × 4 mm) were randomly assigned to 4 groups: control (no treatment), fluoride varnish, calcium nanophosphate paste and casein phosphopeptide-amorphous calcium phosphate paste (CPP-ACP). Both pastes were applied for 5 minutes, and fluoride varnish, for 24 h. Four daily erosive cycles of 5 minutes of immersion in a cola drink and 2 h in artificial saliva were conducted for 5 days. KHN readings were performed at baseline and after 5 days. The percentage of enamel hardness change (%KHN) was obtained after erosion. The surface topography was evaluated by atomic force microscopy (AFM). The data were tested using ANOVA, Tukey's and paired-T tests (p < 0.05). After an erosive challenge, there was no statistically significant difference between the control (96.8 ± 11.4 KHN / 72.4 ± 3.0 %KHN) and the varnish (91.7 ± 14.1 KHN / 73.4 ± 5.5 %KHN) groups. The nanophosphate group showed lower enamel hardness loss (187.2 ± 27.9 / 49.0 ± 7.9 %KHN), compared with the CPP-ACP group (141.8 ± 16.5 / 60.6 ± 4.0 %KHN), and both were statistically different from the varnish and the control groups. AFM images showed a rough surface for the control and the varnish groups, a non-homogeneous layer with globular irregularities for CPP-ACP, and a thick homogeneous layer for the nanophosphate group. None of the agents provided protection against the development of erosion; however, nanophosphate paste was able to reduce enamel surface softening after the erosive challenge.

Resistência de união entre cimentos resinosos autoadesivos e cerâmicas de zircônia policristalina / Bond strengthof self-adhesive resin cements to polycrystalline zirconia ceramics

O objetivo deste estudo foi avaliar a resistência de união a microtração de cimentos resinosos autoadesivos a cerâmicas de zircônia policristalina. Dezoito blocos cerâmicos de zircônia 3Y-TZP (9 LAVA™ e 9 LAVA™ Plus) foram jateados com partículas de 50 µm de Al2O3por 20 s com pressão de 28 psi a uma distância de 10 mm. Os blocos cerâmicos foram duplicados em resina composta (Point 4, Kerr) por moldagem com silicone. Os blocos de resina composta foram cimentados à superfície jateada da zircônia usando três diferentes cimentos resinosos autoadesivos: (1) RelyX Unicem 2 (3M ESPE); (2) SmartCem 2 (Dentsply); (3) Speedcem (Ivoclar Vivadent). Após 24 h imersos em água destilada a 37oC, os blocos cimentados foram cortados em palitos para testes de microtração,com área da interface adesiva de 1 mm2 ± 0,2 mm, e tensionados até a fratura. Os resultados foram analisados pelo teste de análise de variância de dois fatores e pelo teste de comparações múltiplas LSD (α=0.05). As amostras fraturadas foram analisadas com microscopia eletrônica de varredura (MEV) e o modo de falha foi registrado. A topografia das superfícies cerâmicas antes e após o jateamento foi comparada por microscopia de força atômica (AFM). A resistência de união do cimento Speedcem à zircônia foi estatisticamente superior àquela reportada pelos cimentos RelyX Unicem 2 e SmartCem 2, independentemente da cerâmica usada (p<0,05). O fator cerâmica não teve influência estatística na resistência de união. A interação entre os dois fatores se mostrou significativa (p<0,05). O modo de fratura associado ao SmartCem 2 foi quase exclusivamente adesiva, enquanto oRelyX Unicem 2e o Speedcem exibiram um maior percentual de falhas mistas. Não foram observadas falhas coesivas. O AFM não revelou diferença no padrão de topografia de superfície entre as duas cerâmicas antes ou após o jateamento. Concluiu-se que o cimento Speedcem foi superior na adesão a cerâmicas de zircônia policristalina...

The aim of this study was to evaluate the microtensile bond strength of self-adhesive resin cements to polycrystalline zirconia. Eighteen 3Y-TZP ceramic blocks (9 LAVA™ and 9 LAVA™ Plus) were sandblasted with 50 µm Al2O3 powder for 20 s with a pressure of 28 psi at a working distance of 10 mm. The ceramic blocks were duplicated in composite resin (Point 4, Kerr) using a silicon mold. Composite blocks were bonded to sandblasted zirconia using different self-adhesive resin cements: (1) RelyX Unicem 2 (3M ESPE); (2) SmartCem 2 (Dentsply); (3) Speedcem (Ivoclar Vivadent). After 24 h immersed in distilled water at 37oC the bonded specimens were cut into microtensile bond sticks of 1 mm2 ± 0,2 mminterface areaand loaded in tension until failure. Data were analyzed by two-way ANOVA and LSDtest for multiple comparisons (α=0.05). The fractured surfaces were observed using a scanning electron microscope (SEM) and the failure mode was recorded. Surface topography of the sandblasted and the as sintered zirconia materials were analyzed under an atomic force microscope (AFM).Bond strength of Speedcem cement to zirconia was significantly higher than that of RelyX Unicem 2 and SmartCem 2, irrespective of the ceramic used (p<0,05). Bond strength was not significantly influenced by the ceramic factor. Interactions were significant (p<0,05). The mode of failure of SmartCem 2 was almost exclusively adhesive, while RelyX Unicem 2 and Speedcem exhibited a good percentage of mixed fractures. No cohesive fractures were observed. AFM did not reveal differences in the topography pattern of the two ceramics before or after sandblasting. It was concluded that Speedcem presented superior adhesion to polycrystalline zirconia ceramics...

Resistência de união entre cimentos resinosos autoadesivos e cerâmicas de zircônia policristalina / Bond strengthof self-adhesive resin cements to polycrystalline zirconia ceramics

O objetivo deste estudo foi avaliar a resistência de união a microtração de cimentos resinosos autoadesivos a cerâmicas de zircônia policristalina. Dezoito blocos cerâmicos de zircônia 3Y-TZP (9 LAVA™ e 9 LAVA™ Plus) foram jateados com partículas de 50 µm de Al2O3por 20 s com pressão de 28 psi a uma distância de 10 mm. Os blocos cerâmicos foram duplicados em resina composta (Point 4, Kerr) por moldagem com silicone. Os blocos de resina composta foram cimentados à superfície jateada da zircônia usando três diferentes cimentos resinosos autoadesivos: (1) RelyX Unicem 2 (3M ESPE); (2) SmartCem 2 (Dentsply); (3) Speedcem (Ivoclar Vivadent). Após 24 h imersos em água destilada a 37oC, os blocos cimentados foram cortados em palitos para testes de microtração,com área da interface adesiva de 1 mm2 ± 0,2 mm, e tensionados até a fratura. Os resultados foram analisados pelo teste de análise de variância de dois fatores e pelo teste de comparações múltiplas LSD (α=0.05). As amostras fraturadas foram analisadas com microscopia eletrônica de varredura (MEV) e o modo de falha foi registrado. A topografia das superfícies cerâmicas antes e após o jateamento foi comparada por microscopia de força atômica (AFM). A resistência de união do cimento Speedcem à zircônia foi estatisticamente superior àquela reportada pelos cimentos RelyX Unicem 2 e SmartCem 2, independentemente da cerâmica usada (p<0,05). O fator cerâmica não teve influência estatística na resistência de união. A interação entre os dois fatores se mostrou significativa (p<0,05). O modo de fratura associado ao SmartCem 2 foi quase exclusivamente adesiva, enquanto oRelyX Unicem 2e o Speedcem exibiram um maior percentual de falhas mistas. Não foram observadas falhas coesivas. O AFM não revelou diferença no padrão de topografia de superfície entre as duas cerâmicas antes ou após o jateamento. Concluiu-se que o cimento Speedcem foi superior na adesão a cerâmicas de zircônia policristalina.

The aim of this study was to evaluate the microtensile bond strength of self-adhesive resin cements to polycrystalline zirconia. Eighteen 3Y-TZP ceramic blocks (9 LAVA™ and 9 LAVA™ Plus) were sandblasted with 50 µm Al2O3 powder for 20 s with a pressure of 28 psi at a working distance of 10 mm. The ceramic blocks were duplicated in composite resin (Point 4, Kerr) using a silicon mold. Composite blocks were bonded to sandblasted zirconia using different self-adhesive resin cements: (1) RelyX Unicem 2 (3M ESPE); (2) SmartCem 2 (Dentsply); (3) Speedcem (Ivoclar Vivadent). After 24 h immersed in distilled water at 37oC the bonded specimens were cut into microtensile bond sticks of 1 mm2 ± 0,2 mminterface areaand loaded in tension until failure. Data were analyzed by two-way ANOVA and LSDtest for multiple comparisons (α=0.05). The fractured surfaces were observed using a scanning electron microscope (SEM) and the failure mode was recorded. Surface topography of the sandblasted and the as sintered zirconia materials were analyzed under an atomic force microscope (AFM).Bond strength of Speedcem cement to zirconia was significantly higher than that of RelyX Unicem 2 and SmartCem 2, irrespective of the ceramic used (p<0,05). Bond strength was not significantly influenced by the ceramic factor. Interactions were significant (p<0,05). The mode of failure of SmartCem 2 was almost exclusively adhesive, while RelyX Unicem 2 and Speedcem exhibited a good percentage of mixed fractures. No cohesive fractures were observed. AFM did not reveal differences in the topography pattern of the two ceramics before or after sandblasting. It was concluded that Speedcem presented superior adhesion to polycrystalline zirconia ceramics.

Efeitos de diferentes sistemas de clareamento dental sobre a rugosidade e morfologia superficial do esmalte e de uma resina composta restauradora / Effects of different tooth bleaching systems on the roughness and superficial morphology of enamel and a restorative composite resin

Objetivo: Avaliar as alterações de rugosidade e morfologia superficial do esmalte e da resina composta após diferentes técnicas de clareamento dental. Material e método: incisivos bovinos íntegros foram selecionados, sendo que cavidades padronizadas foram confeccionadas na face vestibular, as quais foram restauradas com resina composta. Os dentes foram distribuídos em grupos, de acordo com o tratamento proposto: G1- clareamento com peróxido de carbamida (PC) 10%; G2 - clareamento com peróxido de hidrogênio (PH) a 38%; G3- clareamento com PH a 38% associado à foto-ativação com LED. Para G1, o agente clareador foi aplicado por 8 horas diárias durante 21 dias. Para G2 e G3, foram realizadas 3 sessões de clareamento, caracterizadas por 3 aplicações do gel clareador por 15 minutos, com intervalos de 7 dias entre as sessões, sendo que em G3 o gel clareador foi ativado com LED (470nm) por 6 minutos. As superfícies do esmalte e da resina composta foram avaliadas antes e após o procedimento clareador através de um rugosímetro e de um microscópio de força atômica. Resultados: Os resultados demonstraram diferença significante da rugosidade do esmalte antes e após o clareamento apenas para G1, em relação ao controle (Wilcoxon, p<0,05). Para a resina composta, nenhum dos grupos apresentou diferença estatística em relação ao controle (Mann-Whitney, p>0,05). Conclusão: O aumento da rugosidade do esmalte aconteceu apenas quando o clareamento foi realizado através da aplicação de um gel com 10% de PC. Nenhum dos procedimentos clareadores avaliados nesta pesquisa interferiram na rugosidade e morfologia da resina composta.

Objective: the aim of this study was to evaluate and compare the roughness and superficial morphology of enamel and a composite restorative resin after different bleaching techniques application. Material and Methods: Bovine incisors were selected and standardized cavities were prepared on the buccal surface, which were restored with composite resin. The teeth were distributed according to the following treatments: G1- bleaching with 10% carbamide peroxide (CP); G2 - bleaching with 38% hydrogen peroxide (HP); and G3 - bleaching with 38% of HP associated to light irradiation. For G1, the bleaching gel was applied for 8 hours daily during 21 days. For G2 and G3, 3 sessions were performed, consisting of 3 applications of 15 minutes each, with 7 days of intervals between the sessions. For G3, the LED (470nm) light was used to activate the bleaching agent for 6 minutes. The surface of enamel and composite resin were evaluated before and after the bleaching procedures using a roughness tester and an atomic force microscope. Results: The results showed significant differences in surface roughness of enamel after bleaching only for G1 (Wilcoxon, p<0.05). For composite resin, neither group showed a statistical difference compared to control (Mann-Whitney, p>0.05). Conclusion: It was concluded that the increase in the roughness of enamel occurred only after bleaching therapy using a gel with 10% of CP. The bleaching procedures evaluated in this investigation did not increase the roughness or cause changes in the superficial morphology of the composite resin.

Molecular imaging of membrane proteins and microfilaments using atomic force microscopy

Atomic force microscopy (AFM) is an emerging technique for a variety of uses involving the analysis of cells. AFM is widely applied to obtain information about both cellular structural and subcellular events. In particular, a variety of investigations into membrane proteins and microfilaments were performed with AFM. Here, we introduce applications of AFM to molecular imaging of membrane proteins, and various approaches for observation and identification of intracellular microfilaments at the molecular level. These approaches can contribute to many applications of AFM in cell imaging.

Reparação tecidual pulpar sob ação bioestimuladora do laser de baixa intensidade (LILT), e do diodo emissor de luz (LED): estudo em macacos prego / Pulp tissue repair under the biostimulation action of low-level laser therapy (LLLT) and of light-emitting diode (LED): study in capuchin monkeys

O estudo investigou os efeitos da radiação eletromagnética não ionizante emitidos pelos diodos LASER com comprimento de onda no espectro 688 ηm e 785 ηm, e diodo LED 635 ± 10 ηm, associados ao capeamento direto com hidróxido de cálcio em exposições pulpares mecânicas. Avaliou-se assim em dentes de macacos-prego a resposta pulpar baseado na morfologia das células pulpares, no processo inflamatório local, na formação da barreira mineralizada, e na organização do tecido pulpar nos diferentes grupos estudados. Discutiu-se também as diferentes fontes de emissão de radiação eletromagnética comparando os resultados obtidos de estimulação pulpar com os diodos LASER e LED, os quais apresentam energia coerente e não-coerente, respectivamente. Os resultado mostraram uma estimulação em todos os grupos irradiados com melhores resultados para o estímulo com LASER, quando comparado ao grupo tratado isoladamente com hidróxido de cálcio. Concluímos assim que a estimulação de energia eletromagnética LASER e LED associado ao capeamento pulpar direto com hidróxido de cálcio apresentou aceleração no processo de reparação tecidual. Porém, há necessidade de novos estudos com diferentes parâmetros de irradiação a fim de se obter protocolos cada vez mais eficientes para o estudo dos efeitos da luz sobre o processo de reparação pulpar.

The aim of this study was to compare the effects of non-ionizing electromagnetic radiation emitted by LASER diodes 688 ηm and 785 ηm, and LED diode 635 ± 10 ηm associated to direct pulp capping with calcium hydroxide in traumatic pulp exposures were investigated. Based on pulp cells morphology, on the local inflammatory process, on mineralized barrier formation and on pulp tissue organization, the pulp response in capuchin monkey teeth was evaluated in different groups. It was also discussed the different electromagnetic radiation emission sources effects comparing the obtained results of pulp stimulation with diodes LASER and LED, which present coherent and non-coherent energy respectively. Stimulation was observed in all irradiated groups, being the best results achieved with LASER stimulation, when compared to the group treated only with calcium hydroxide. Thus, it is concluded that the electromagnetic LASER and LED energy stimulation associated with calcium hydroxide direct pulp capping accelerated the tissue repair process. However, further studies with different stimulation parameters in order to obtain increasingly efficient protocols to study light effects on pulp repair are necessary.

Three-dimensional nano-level morphological changes of hippocampal neurons either being damaged or protected / 中华创伤杂志

Objective To investigate the effect and mechanism of p38 MAPK inhibition in reducing the damage to rat's hippocampal neurons caused by kainic acid (KA) and observe the three-dimensional morphological changes on the cell surface. Methods The rat's hippocampal neurons cultured primarily for 10 days were pretreated with SB203580 (0.2 ?mol/L, a p38 MAPK inhibitor). Thirty minutes later, the hippocampal neurons were administered with KA at concentrations of 0, 25 and 250 ?mol/L for action for 10 and 100 minutes respectively. The cellular membrane structure was scanned and examined at nano-level by using atomic force microscope. Results Normal neurons displayed smooth membrane surface with homogeneous and regular undulation. In contrast, the neurons treated with KA showed coarse membrane surface with holes. Furthermore, the degree changes increased with the action time and the KA concentrations in a dose-effect dependent fashion. The above-mentioned changes were obviously mitigated by means of pretreatment with SB203580 (200 nmol/L). Conclusions Inhibition of p38 MAPK may, in certain degrees, protect the neurons against the impairments on cytomembrane resulted from the toxic effect of KA.

Analysis of chromosome aberration due to ethidium bromide using AFM / 中国病理生理杂志

AIM:To study chromosome aberration due to ethidium bromide (EB), a heterocyclic organic compound and an organic fluorescence dye commonly used in biochemical experiment, and to help further understanding the molecular mechanism of tumor or cancer induced by EB and other heterocyclic organic compounds. METHODS: The toxicity action of EB was evaluated from three aspects including DNA, chromosome and embryo stem cells (ESCs) using atomic force microscopy (AFM), and thereinto, the morphology structural difference of ESCs treated with two EB doses was also valuated. RESULTS: The morphological structures of DNA, chromosome and ESCs were dramatically damaged. The average height of DNA decreased 0.5 nm; chromosomal arms were ruptured from centromere location; molecules of cellular membrane congregated and loop-like structure formed, and ES cell masses were collapsed and became dead after large EB doses treatment and mesh-like morphological structure was discernable. CONCLUSION: The toxicity action of EB is strong and destroys the surface structure of DNA and chromosome. EB induces structural aberration of ES cellular membrane and cell death. The results indicate that the action of EB is externalized at gene level and cell level, which is important to study the carcinogenicity of EB.

Preliminary Observation of Mycoplasma Genitalium under Electron Microscopy and Atomic Force Microscopy / 中华皮肤科杂志

Objective To further identify the isolated Mycoplasma genitalium (Mg) from the high risk population of STD in China. Mothods The morphology of Mg standard strains and clinical isolates were observed under electron microscopy (EM) and atomic force microscopy (AFM). Mg sample preparation for AFM was fixed on mica and AFM images of scanning observation were captured by contacting and tapping modes and operated under normal atmospheric pressure and temperature. Results and Conclusion Mg had a diversity of shapes, including flask, pear, spindle or round shape with projecting neck portion and slightly broadened terminal structure under EM. The morphologic features under AFM were similar to those observed by EM. The typical Mg showed shapes of flask and pear with noticeable narrow ring or mark in the neck portion. The size of Mg measured under EM and AFM was similar as well. Mycoplasma

Ultrastructure and function of human bone marrow mesenchymal stem cells / 中国病理生理杂志

AIM: To study the cytoskeleton of mesench ymal stem cells (MSCs), the ultrastructure and function relationship by using atomic force microscope (AFM). METHODS: The ultrastructures and morphological feature of MSCs c ultured for 1 d and 5 d were studied by AFM. RESULTS: The special structures that possess peculiar morphologi cal characteristic of MSCs such as cytoskeleton, pseudopod, microfilament etc we re identified by AFM, and these special structures are difficult to observe unde r electronic microscopy or other conventional optical microscopy. CONCLUSIONS: AFM is a powerful tool to study ultrastructures, mo rphological features, and cytoskeleton of stem cells in near physiological condi t ions. Its application prospect in cellular biology is extensive. The special cyt oskeleton and other structures of MSCs observed above may represent the structur al base of multi-differentiation potential of MSCs.