microhardness
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OBJECTIVE: To measure the Knoop microhardness at the bottom of four posterior resin-based composites (RBCs): Tetric EvoCeram Bulk Fill (Ivoclar Vivadent), SureFil SDR flow (DENTSPLY), SonicFill (Kerr), and x-tra fil (Voco). METHODS: The RBCs were expressed into metal rings that were 2, 4, or 6-mm thick with a 4-mm internal diameter at 30°C. The uncured specimens were covered by a Mylar strip and a Bluephase 20i (Ivoclar Vivadent) polywave(®) LED light-curing unit was used in high power setting for 20s. The specimens were then removed and placed immediately on a Knoop microhardness-testing device and the microhardness was measured at 9 points across top and bottom surfaces of each specimen. Five specimens were made for each condition. RESULTS: As expected, for each RBC there was no significant difference in the microhardness values at the top of the 2, 4 and 6-mm thick specimens. SureFil SDR Flow was the softest resin, but was the only resin that had no significant difference between the KHN values at the bottom of the 2 and 4-mm (Mixed Model ANOVA p<0.05). Although the KHN of SureFil SDR Flow was only marginally significantly different between the 2 and 6-mm thickness, the bottom at 6-mm was only 59% of the hardness measured at the top. CLINICAL SIGNIFICANCE: This study highlights that clinicians need to consider how the depth of cure was evaluated when determining the depth of cure. SureFil SDR Flow was the softest material and, in accordance with manufacturer's instructions, this RBC should be overlaid with a conventional resin.
- MeSH
- akrylové pryskyřice chemie účinky záření MeSH
- analýza zatížení zubů MeSH
- bisfenol A-glycidyl methakrylát chemie účinky záření MeSH
- dentální adheziva tuhnoucí světlem přístrojové vybavení metody MeSH
- methakryláty chemie účinky záření MeSH
- polymerizace účinky záření MeSH
- polyurethany chemie účinky záření MeSH
- povrchové vlastnosti účinky záření MeSH
- složené pryskyřice chemie účinky záření MeSH
- stomatologické polymerizační lampy * MeSH
- testování materiálů MeSH
- zubní materiály chemie účinky záření MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Introduction: The purpose of this study was to examine the microhardness and modulus of elasticity (MOE) of White ProRoot MTA (Dentsply Tulsa Dental, Tulsa, OK) after setting in moist or dry intracanal conditions. Methods and Materials: To simulate root canal system, 14 polyethylen molds with internal diameter of 1 mm and height of 12 mm were used. These molds were filled with 9-mm thick layers of White ProRoot Mineral Trioxide Aggregate (MTA; Dentsply Tulsa Dental, Tulsa, OK). The experimental group (n=7) had a damp cotton pellet with 1.5 mm height and a 1.5 mm layer of resin composite placed on it. In control group (n=7) the whole 3 mm above MTA were filled with resin composite. The specimens were kept in 37°C and relative humidity of 80% for 4 days in order to simulate physiological conditions. Specimens were longitudinally sectioned and nanoindentation tests were carried out using Berkovich indenter at loading rate of 2 mN/s at 4×5 matrices of indents which were located in the coronal, middle and apical thirds of the specimen's cross section, to evaluate the microhardness and modulus of elasticity of the specimen to appraise the progression of the setting process. Differences were assessed using nonparametric generalized Friedman rank sum and Wilcoxon Rank-Sum tests. Results: Statistical analysis showed that there was a significant difference in microhardness and MOE between control and experimental groups at coronal (P<0.001), middle (P<0.001) and apical (P<0.001) thirds of the simulated rod from simulated apical foramen. Kruskal-Wallis test showed no significant effect of depth on microhardness of material in experimental or control groups. Conclusion: Within limitations of this in vitro study, it seems that moist intracanal environment improves setting of MTA in various depths.
- Publikační typ
- časopisecké články MeSH
OBJECTIVES: The hierarchical structure of enamel gives insight on the properties of enamel and can influence its strength and ultimately caries experience. Currently, past caries experience is quantified using the decayed, missing, filled teeth/decayed, missing, filled surface (DMFT/DMFS for permanent teeth; dmft/dmfs for primary teeth), or international caries detection and assessment system (ICDAS) scores. By analyzing the structure of enamel, a new measurement can be utilized clinically to predict susceptibility to future caries experience based on a patient's individual's biomarkers. The purpose of this study was to test the hypothesis that number of prisms by square millimeter in enamel and average gap distance between prisms and interprismatic areas, influence caries experience through genetic variation of the genes involved in enamel formation. MATERIALS AND METHODS: Scanning electron microscopy (SEM) images of enamel from primary teeth were used to measure (i) number of prisms by square millimeter and interprismatic spaces, (ii) prism density, and (iii) gap distances between prisms in the enamel samples. The measurements were tested to explore a genetic association with variants of selected genes and correlations with caries experience based on the individual's DMFT+ dmft score and enamel microhardness at baseline, after an artificial lesion was created and after the artificial lesion was treated with fluoride. RESULTS: Associations were found between variants of genes including ameloblastin, amelogenin, enamelin, tuftelin, tuftelin interactive protein 11, beta defensin 1, matrix metallopeptidase 20 and enamel structure variables measured (number of prisms by square millimeter in enamel and average gap distance between prisms and interprismatic areas). Significant correlations were found between caries experience and microhardness and enamel structure. Negative correlations were found between number of prisms by square millimeter and high caries experience (r value= -0.71), gap distance between prisms and the enamel microhardness after an artificial lesion was created (r value= -0.70), and gap distance between prisms and the enamel microhardness after an artificial lesion was created and then treated with fluoride (r value= -0.81). There was a positive correlation between number of prisms by square millimeter and prism density of the enamel (r value = 0.82). CONCLUSIONS: Our data support that genetic variation may impact enamel formation, and therefore influence susceptibility to dental caries and future caries experience. CLINICAL RELEVANCE: The evaluation of enamel structure that may impact caries experience allows for hypothesizing that the identification of individuals at higher risk for dental caries and implementation of personalized preventative treatments may one day become a reality.
- Publikační typ
- časopisecké články MeSH
PURPOSE OF THE STUDY In clinical practice UHMWPE is the most commonly used material for manufacturing articular components of joint replacements. The purpose of this study is to find out whether repeated ethylene oxide sterilization results in oxidative degradation of UHMWPE or not and also whether the oxidative degradation of various types of ethylene oxide-sterilized UHMWPE depends on storage time or not. MATERIAL AND METHODS The set included 12 samples of UHMWPE (three samples with different modifications (virgin PE, with E vitamin and cross-linked with thermal treatment) and different number of sterilizations (0×-3×)). The set also included 8 samples of commercial components of hip or knee replacements sterilized with ethylene oxide and stored for different storage periods. The oxidative degradation was assessed by infrared microspectroscopy, based on which the oxidation index (OI), transvinylene index (VI), crystallinity index (CI) and E vitamin index (EI) were calculated. Mechanical properties of UHMWPE were obtained through microhardness measurements. Statistical processing of the results was performed. RESULTS In all the samples, very low oxidative degradation values were reported (most OI values < 0.1). All radiation crosslinked UHMWPE samples showed an increased VI index and a slightly lower crystallinity index. All unmodified samples (irrespective of whether or not and how many times or how long ago the samples were sterilized with EtO) had almost zero value of VI. Changes in crystallinity were negligible (in the rage of 0.56-0.63), which required very accurate measurements of micromechanical properties. Yet, linear correlation was established between microhardness and crystallinity. DISCUSSION All the mentioned indices changed as anticipated: OIs were very low and slightly increased with time of storage, VIs of radiation crosslinked samples grew in proportion to the total gama radiation dose, CIs decreased in samples thermally treated by remelting, and EIs were very low due to negligible concentration of stabiliser (0.1%) in the samples of medical grade UHMWPE. CONCLUSIONS All samples showed zero or minimum oxidative degradation. This confirmed that neither ethylene oxide sterilization, nor multiple EtO sterilization or longer storage of polymer after ethylene oxide sterilization result in major oxidative degradation. Key words: UHMWPE, ethylene oxide, sterilization, oxidation, infrared spectroscopy, microhardness.
- MeSH
- artroplastiky kloubů * MeSH
- ethylenoxid * MeSH
- lidé MeSH
- polyethyleny MeSH
- sterilizace metody MeSH
- vitaminy MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Úvod: V posledních dvaceti letech můžeme v moderní společnosti pozorovat podstatný nárůst konzumace ovocných džusů a perlivých nealkoholických nápojů, tzv. soft drinků. Většina z nich obsahuje vedle vody a různých přísad kyselinu citronovou, fosforečnou a uhličitou. Hodnota pH těchto nápojů je obvykle nižší než 4,0. Pokud jsou tvrdé zubní tkáně často vystaveny působení těchto vnějších kyselin, dochází ke změkčení povrchu zubu a vzniku nevratného erozivního poškození skloviny. Cíl: Cílem naší in vitro studie bylo zjistit změny základních mechanických vlastností skloviny lidských extrahovaných molárů (mikrotvrdosti a modulu elasticity) vystavených účinkům vybraných nápojů typu soft drink (Kofola, Coca-Cola), pomerančového džusu a bílého jogurtu. Materiál a metody: Ze zdravých vestibulárních a orálních plošek čerstvě extrahovaných lidských molárů jsme připravili 40 sklovinných vzorků velikosti asi 5x3x1,5 mm. Na začátku experimentu jsme změřili pomocí nanoindentace (NanoTest NT 600, Micromaterials, Velká Británie) mikrotvrdost a modul elasticity skloviny. Zároveň byla mikroskopem atomárních sil (AFM) zachycena povrchová topografie sklovinných vzorků. Získané údaje sloužily jako kontrola. Poté byly sklovinné vzorky náhodně rozděleny do čtyř skupin. Vzorky první skupiny byly ponořeny do nápoje Kofola (Kofola, a. s., Krnov, Česká republika), vzorky druhé skupiny do nápoje Coca-Cola (Coca-Cola HBC, Česká republika), vzorky třetí skupiny do pomerančového džusu Hello (Nivnice, Česká republika) a vzorky čtvrté skupiny do bílého jogurtu Klasik (OLMA, Česká republika), a to na dobu pěti minut při pokojové teplotě. U každého testovaného nápoje a jogurtu bylo zjištěno jejich pH a titrovatelná acidita. Následně byly vzorky opláchnuty destilovanou vodou a osušeny. S pomocí nanoindentoru byla opět u všech vzorků změřena mikrotvrdost a modul elasticity. Mikroskopem atomárních sil byl zachycen aktuální obraz povrchu vzorků. Získané výsledky se statisticky zpracovaly (párový Studentův t-test) a porovnaly se s výsledky měření před expozicí kyselým nápojům a jogurtu. Výsledky: Největší redukce mikrotvrdosti skloviny byla pozorována u vzorků vystavených působení Coca-Coly (43,6 ± 14,4 %) a pomerančového džusu (41,7 ± 3,4 %). Největší pokles modulu elasticity skloviny byl pozorován u skupiny vzorků ponořených do pomerančového džusu (15,7 ± 4,7 %) a Kofoly (14,9 ± 9,0 %). Vliv jogurtu na mechanické vlastnosti zubní skloviny nebyl statisticky signifikantní (p > 0,05). Závěr: Výsledky našeho experimentu prokázaly podstatné snížení hodnot mechanických vlastností zubní skloviny vzorků vystavených působení vybraných kyselých nápojů. Jogurt, přestože má kyselé pH, nevyvolal díky obsahu minerálních látek výrazné změny mechanických vlastností skloviny.
Introduction: In the last twenty years we can observe in modern society significant increase of fruit juices and carbonated soft drinks consumption. The most of them besides water and different additives contain citric, phosphoric and carbonic acids. The pH of these beverages is usually lower than 4.0. Frequent exposure of hard dental tissues to dietary acids leads to surface softening and irreversible erosive wear. Aim: The aim of our in vitro study was to determine the changes of enamel microhardness and elastic modulus of human extracted molars immersed into selected soft drinks (Kofola, Coca-Cola), orange juice and white yoghurt. Materials and Methods: 40 enamel samples (5x3x1.5 mm) were prepared from intact vestibular and oral surfaces of freshly extracted human molars. At the beginning of the experiment microhardness and elastic modulus were measured by nanoindentation (NanoTest NT 600, Micromaterials, Great Britain). Surface topography of enamel samples was studied by atomic force microscopy. Received data were used as control. After that the enamel samples were randomly divided into 4 groups. The samples of the 1st group were immersed to soft drink Kofola (Kofola JSC, Krnov, Czech Republic), the samples of the 2nd group to Coca-Cola (Coca-Cola HBC, Czech Republic), the samples of the 3rd group were exposed to orange juice Hello (Nivnice, Czech Republic), the samples of the 4th group to white yoghurt Klasik (OLMA, Czech Republic). The time of exposure was 5 minutes. Yoghurt and drinks had room temperature. The pH and titratable acidity of every beverage and yoghurt were determined. After immersion the samples were rinsed with distilled water and dried up. After that microhardness and elastic modulus were measured. Surface topography of the samples was studied again. Received data were statistically worked up (paired Student’s t-test) and compared with initial data before exposure to acidic drinks and yoghurt. Results: The most distinguished reduction of enamel microhardness was observed among samples exposed to Coca-Cola (43.6 ± 14.4%) and orange juice (41.7 ± 3.4%). The most distinguished decrease of elastic modulus was observed among samples immersed to orange juice (15.7 ± 4.7%) and Kofola (14.9 ± 9.0%). The influence of yoghurt on enamel mechanical properties was insignificant (p > 0.05). Conclusions: The results of our experiment prooved significant reduction of enamel mechanical properties after their exposure to acidic beverages. Despite of acidic pH, yoghurt did not cause significant changes of enamel mechanical properties due to its mineral components.
- Klíčová slova
- nanoindentace, mikrotvrdost, modul elasticity, zubní eroze, dietární kyseliny,
- MeSH
- interpretace statistických dat MeSH
- kyseliny škodlivé účinky MeSH
- lidé MeSH
- mikroabraze zubní skloviny statistika a číselné údaje MeSH
- mikroskopie atomárních sil MeSH
- mikroskopie využití MeSH
- moláry chemie MeSH
- potraviny a nápoje škodlivé účinky MeSH
- rozpustnost zubní skloviny MeSH
- testy tvrdosti metody přístrojové vybavení MeSH
- Check Tag
- lidé MeSH
Hydroxyapatite layers with silver doping from 0.06 at.% to 14 at.% were prepared by laser deposition. The films' physical properties such as morphology, composition, crystallinity, Young's modulus and microhardness were measured. Films were amorphous or polycrystalline in dependence on deposition temperature (from RT to 600 °C). Antibacterial properties were tested using Escherichia coli and Bacillus subtilis cells. The antibacterial efficacy changed with silver doping from 4% to 100%. Cytotoxicity was studied by a direct contact test. Depending on doping and crystallinity the films were either non-toxic or mildly toxic.
- MeSH
- antibakteriální látky farmakologie MeSH
- buněčná smrt účinky léků MeSH
- buňky NIH 3T3 MeSH
- difrakce rentgenového záření MeSH
- Escherichia coli účinky léků MeSH
- fibroblasty cytologie účinky léků MeSH
- hydroxyapatit farmakologie MeSH
- křemík farmakologie MeSH
- krystalizace MeSH
- lasery * MeSH
- mikrobiální testy citlivosti MeSH
- mikroskopie elektronová rastrovací MeSH
- modul pružnosti účinky léků MeSH
- myši MeSH
- Staphylococcus aureus účinky léků MeSH
- titan farmakologie MeSH
- tvrdost účinky léků MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Structure and properties of several ultrahigh-molecular-weight polyethylenes (UHMWPEs), which were crosslinked either by standard, single-step irradiation or by newer, several-step irradiation (sequential irradiation), were compared. To verify the results, the same characterization was carried out for commercially available UHMWPE liners made of sequentially irradiated polymer (X3™, Stryker, Mahwah, NJ) and one-step irradiated polymer (denoted as PE-IMC, produced by Beznoska, Kladno, Czech Republic). The structure was studied by a number of spectroscopic, diffraction, thermal, and microscopic methods. Mechanical properties were assessed by small-punch, microhardness and, wear testing. Our results suggested that sequential irradiation followed by annealing did not lead to unusual structure at the molecular or supermolecular level. Consequently, all measured mechanical properties, including wear resistance, were comparable with one-step irradiated UHMWPEs.
We present the structural modification of a commercially available glass ionomer cement by inserting the imidazolium salt 1-n-hexadecyl-3-methylimidazolium chloride (C16MImCl), composing a new biomaterial with antifungal biofilm activity. Test specimens were prepared using a commercial glass ionomer cement to which 10 ppm of cetylpyridinium chloride (reference ionic antifungal agent) or C16MImCl were added. The feasibility and hypoallergenicity of the new biomaterial were assessed by microhardness plastic deformation and chorioallantoic membrane assays. Colony counting and scanning electron microscopy were used to evaluate the modified specimens' antibiofilm activity against three multidrug-resistant Candida species. The modified glass ionomer cement presented a strong antibiofilm activity against Candida spp., without losing its original micromechanical and hypoallergenic properties, rendering it a promising candidate for further application in dentistry.
