共查询到20条相似文献，搜索用时 15 毫秒
1.
Objectives
Camphorquinone (CQ) is the most important photoinitiator used in dental composite resins. Sparse data indicate a mutagenic potential of CQ. Therefore, it was aim of this study to evaluate the cytotoxicity, genotoxicity, and mutagenicity of CQ in L5178Y TK+/? mouse lymphoma cells.Methods
L5178Y/TK+/? cells were exposed to different concentrations of non-irradiated CQ (0.25–2.5 mM). Cytotoxicity was evaluated by propidium iodide assay, determination of suspension growth rate, relative total growth and the mitotic index. Intracellular levels of reactive oxygen/nitrogen species (ROS/RNS) were quantified by 2′,7′-dichlorofluoresceine diacetate (DCFH-DA). Early induction of DNA strand breaks and oxidative DNA base lesions was assessed using the 8-hydroxyguanine DNA-glycosylase 1 (hOGG1)-modified alkaline comet assay, whereas mutagenicity of CQ was determined in the mouse lymphoma TK assay (MLA), according to OECD Guideline No. 490.Results
CQ (0.5–2.5 mM) induced concentration- and time-dependent inhibition of cell growth associated with increased ROS/RNS production, amounting to 2342% ± 1108% of controls after 90 min at 2.5 mM. Additionally, CQ concentration-dependently caused direct DNA-damage, i.e. formation of DNA strand breaks and 8-hydroxy-2′-deoxyguanosine. Whereas the MLA indicated lack of mutagenicity of CQ after a 4 h of treatment, CQ concentration-dependently increased total mutant frequency (MF) after 24 h (about 2-fold at 2.5 mM). But, based on the global evaluation factor concept, increase in MF did not reach biologically relevance.Significance
CQ induced concentration-dependent, cytotoxic and genotoxic effects in L5178Y/TK+/? cells, most likely due to oxidative stress, but without mediating obvious biological relevant mutagenicity. 相似文献2.
Tritala K. Vaidyanathan Jayalakshmi Vaidyanathan Pambadikandathil Philipose Lizymol Saraswathy Ariya Kalliyana Venketeswaran Krishnan 《Dental materials》2017,33(1):1-11
Objective
The goal of the study was to characterize the efficiency of polymerization of Type 1 and Type 2 initiators for visible light cure of a BisGMA-TEGDMA monomer mixture.Methods
Raman spectroscopy was used to follow conversion during polymerization of a BisGMA-TEGDMA mixture using a Type I photoinitiator diphenyl(2,4,6 dimethylbenzoyl)phosphine oxide (TPO) and a Type II photoinitiator camphorquinone (CQ) and an amine, both initiators at 0.5 wt.%. Different light exposure times and storage times after light curing were used as variables.Results
There was a significant difference between the relative exposure times of TPO and CQ/amine (5 s for TPO vs. 20 s for CQ/Amine) for attaining maximum % conversion (78% in TPO vs. 65% in CQ/Amine). There was also a significant difference in the effect of storage time (no effect in TPO vs. increased % conversion with CQ/Amine). These effects are attributed to differences in the rate controlling steps of free radical generation in Type 1/Type 2 initiators, and the potential for radiative and non-radiative energy losses in CQ/Amine in its excited state.Conclusions
The results confirm that photo-polymerization of BisGMA is much more efficient with TPO than with CQ/amine. Both exposure and storage times were important variables in CQ/amine, but not in TPO.Significance
TPO photolysis generates significantly more free radicals with potentially very little radiative and non-radiative energy loss in comparison with CQ/amine. The resulting improved monomer conversion is of major importance in resisting chemical and mechanical degradation and preventing toxicological adverse effects. 相似文献3.
Pong Pongprueksa Jan De Munck Masanao Inokoshi Bart Van Meerbeek 《Dental materials》2018,34(4):684-692
Objective
To evaluate the effect of the kind and concentration of photo-initiator on the degree of conversion (DC) of adhesives on dentin/glass substrates and their mini-interfacial fracture toughness (mini-iFT) to dentin.Methods
We tested the adhesive Clearfil S3 Bond Plus and 4 derived experimental ‘LUB’ (‘Leuven Univesity Bond’) adhesives (all from Kuraray Noritake), namely ‘LUB-CQ/amine_high’, ‘LUB-CQ/amine_low’, ‘LUB-TPO_high’, and ‘LUB-TPO_low’, respectively containing 2.0 wt% camphorquinone (CQ) and 2.0 wt% EDMAB (amine), 0.35 wt% CQ and 0.35 wt% amine, 2.0 wt% TPO, and 0.35 wt% TPO. For DC, each adhesive was applied onto glass or dentin prior to being cured (Bluephase 20i; Ivoclar Vivadent: “high mode”) for 10 s. DC was measured at 5 min, 10 min, 1 h, 24 h and 1 week using micro-Raman spectroscopy (SENTERRA; BrukerOptik). For mini-iFT, each adhesive was bonded to 320-grit SiC-paper ground dentin and covered with composite (Z100; 3 M ESPE). The restored teeth were cut in sticks (1.5 × 2.0 × 16 mm), after which a single-gradient notch was prepared at the adhesive-dentin interface using a 150-μm diamond blade. The micro-specimens were loaded until failure in a 4-point bending test and the mini-iFT in term of KQvM was calculated.Results
DC was higher on dentin than on glass. All adhesives were adequately polymerized at 1 week, except for LUB-TPO_low. DC at 5 min was significantly higher for LUB-TPO_high than for both CQ/amine-based adhesives. The highest and most reliable mini-iFT was measured for LUB-CQ/amine_high, despite its 5-min DC was relatively low. No correlation between DC and mini-iFT was found.Significance
Curing of TPO-based adhesives is faster, but the dark cure of the CQ/amine-containing adhesives is more efficient. The differences in curing profiles do affect the mechanical properties of the resultant interfaces at dentin. 相似文献4.
Nancy J. Lin Courtney Keeler Alison M. Kraigsley Jing Ye Sheng Lin-Gibson 《Dental materials》2018,34(5):776-785
Objective
Resin-based composites are known to elute leachables that include unincorporated starting materials. The objective of this work was to determine the effect of common dental monomers and initiators on Streptococcus mutans biofilm metabolic activity and biomass.Methods
S. mutans biofilms were inoculated in the presence of bisphenol A glycerolate dimethacrylate (BisGMA), triethylene glycol dimethacrylate (TEGDMA), camphorquinone (CQ), and ethyl 4-(dimethylamino)benzoate (4E) at 0.01 μg/mL up to 500 μg/mL, depending on the aqueous solubility of each chemical. Biofilms were evaluated at 4 h and 24 h for pH (n = 3–8), biomass via crystal violet (n = 12), metabolic activity via tetrazolium salt (n = 12), and membrane permeability for selected concentrations via confocal microscopy (n = 6). Parametric and non-parametric statistics were applied.Results
500 μg/mL TEGDMA reduced 24 h metabolic activity but not biomass, similar to prior results with leachables from undercured BisGMA-TEGDMA polymers. 50 μg/mL BisGMA reduced biofilm biomass and activity, slightly delayed the pH drop, and decreased the number of cells with intact membranes. 100 μg/mL CQ delayed the pH drop and metabolic activity at 4 h but then significantly increased the 24 h metabolic activity. 4E had no effect up to 10 μg/mL.Significance
Monomers and initiators that leach from resin composites affect oral bacterial biofilm growth in opposite ways. Leachables, which can be released for extended periods of time, have the potential to alter oral biofilm biomass and activity and should be considered in developing and evaluating new dental materials. 相似文献5.
Takayuki Ueda Keitaro Kubo Takeshi Saito Tomokuni Obata Takeshi Wada Koichiro Yanagisawa Kaoru Sakurai 《Journal of prosthodontic research》2018,62(4):422-425
Purpose
The objective was to investigate the influence of chemical and mechanical cleaning on the surface morphology of a silicone soft relining material.Methods
Three plate-shaped specimens were prepared for each group (Control, Hard and Soft) by laminating a 1.5-mm-thick silicone soft relining material. The Control group specimens were stored in water, and the Hard and Soft group specimens were cleaned with hard and soft bristle denture brushes, respectively. Abrasion testing with a toothbrush and immersion testing with an enzyme-containing peroxide denture cleanser were performed, simulating a period of approximately 4 months. The arithmetic mean roughness (Sa) and maximum height of the cross-section (Sz) were measured before and after abrasion and immersion testing.Results
Sa was 4.9 ± 0.9, 22.1 ± 4.2 and 44.2 ± 4.0 μm in the Control, Soft and Hard groups, respectively. Sz was 257.5 ± 31.7, 392.0 ± 23.8 and 452.2 ± 41.9 μm in the Control, Soft and Hard groups, respectively. After abrasion testing, Sa and Sz differed significantly between the Soft and Control groups and between the Hard and Control groups. Sa was 2.2 ± 1.2 μm before and after immersion, and Sz was 142.1 ± 81.4 μm before and after immersion. No significant difference was noted in either Sa or Sz in the Control specimens before or after immersion.Conclusions
Surfaces cleaned using a soft bristle brush were less likely to roughen than those cleaned with a hard bristle brush under the conditions of this study. Additionally, chemical cleaning using the enzyme + neutral peroxide denture cleanser did not roughen the surface of the silicone soft relining material. 相似文献6.
Ollie Yiru Yu May Lei Mei Irene Shuping Zhao Quan-Li Li Edward Chi-Man Lo Chun-Hung Chu 《Dental materials》2018,34(12):e344-e352
Objective
To evaluate the remineralising effect of the adjunctive application of 38% silver diamine fluoride (SDF) solution and 5% sodium fluoride (NaF) varnish on artificial enamel caries lesions.Methods
Forty-eight demineralised enamel specimens were allocated into four groups. Group 1 received 38% SDF and 5% NaF; Group 2 received 38% SDF; Group 3 received 5% NaF; and Group 4 received deionized water. After pH cycling, the surface morphology and fluoride content of the specimens were studied via scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS). The lesion depth and crystal characteristics were assessed using micro-computed tomography and X-ray diffraction (XRD) respectively. The crystallization reaction was performed by incubating hydroxyapatite powder with NaF or SDF for 48 h. The precipitates were studied via transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS).Results
SEM demonstrated the destruction of the enamel surface in Group 4. EDS revealed that the mean fluoride weight percentage of Groups 1–4 were 1.28 ± 0.15, 1.33 ± 0.19, 1.03 ± 0.09 and 0.87 ± 0.04 respectively. The mean lesion depths of Groups 1–4 were 129 ± 14 μm, 131 ± 16 μm, 153 ± 10 μm and 181 ± 21 μm respectively. The addition of NaF to SDF did not reduce the lesion depths (p = 0.779). XRD revealed that silver chloride formed as a main product in Groups 1 and 2. Meanwhile, TEM analysis indicated that silver nanoparticles were incorporated into hydroxyapatite crystal in SDF-treated hydroxyapatite. XPS spectra suggested that the chemical state of the silver was metallic.Significance
The adjunctive application of SDF and NaF varnish had a similar remineralising effect to that of SDF on enamel caries. 相似文献7.
Objective
This in-vitro study aimed to develop a technique to measure the frictional forces and determine the frictional coefficient (μ) associated with the rubbing of dental floss against teeth. Incorrect flossing technique and the etiology of grooves at the cementoenamel junction (CEJ) of proximal area of teeth has long been a controversial topic. We hypothesized that the μ between teeth surfaces and dental floss is affected by contact angulation.Materials and methods
Tests were conducted using two different types of dental floss (waxed and unwaxed nylon) on different surfaces (enamel, dentine, smooth and rough glass rods) under different moisture conditions (dry and wet). The μ generated by performing C-shape flossing was measured, using the Capstan equation, at constant load (100 g) over different flossing contact sliding angulations. In addition, the surface characteristics of intact and used nylon flosses were compared using a scanning electron microscope (SEM).Results
The mean μ was highest with a smooth glass rod (0.42 ± 0.11), followed by rough glass rods (0.30 ± 0.07), dry enamel (0.27 ± 0.08), wet enamel (0.23 ± 0.06), then dentine (0.18 ± 0.04). Moreover, higher μ was associated with waxed floss when used against dry enamel, smooth and rough glass rods (P < 0.001). At different moisture conditions, waxed floss demonstrated greater μ with dry surfaces (P < 0.03). No association was found between μ and dental floss contact angulation. Both floss types showed deterioration after usage; although waxed type exhibited markedly greater deterioration when used on dry surfaces. In conclusion, the magnitude of the μ was found to be influenced by surface roughness, moisture condition, and independent of the contact angulation area during sliding of dental floss.Significance
It is important to consider the potential side effects of frictional forces on both tooth surface and dental floss during clinical application. 相似文献8.
Objective
To evaluate the effect of different pH media on zirconia-reinforced lithium silicate glass ceramic and how they interact with opposing dentition after being aged in different pH cycling and high temperature conditions.Methods
Twenty-five rectangular shaped specimens were prepared from lithium silicate reinforced with zirconia blanks (Suprinity, Vita Zahnfabrick) and stored in different pH media (3 & 7.2) for different periods (24 h & 7 days) at temperature (55 °C). After their surface roughness (Ra) evaluation, aged ceramic specimens were subjected to cyclic abrasive wear with opposing natural teeth enamel for 150,000 cycles using a chewing simulator. Weight loss and Scanning Electron Microscope (SEM) images were used to evaluate the cyclic wear results.Results
After different pH storage, ceramic group stored at 3 pH for 1-W (1 week) gave significantly higher mean Ra value (0.618 μm ± 0.117) than control lowest mean value (0.357 μm ± 0.054) before cyclic wear. On the other hand, it caused the least significant weight loss value (0.004 gm ± 0.001) to opposing tooth enamel. There was significant tooth enamel weight loss (0.043 gm ± 0.004) when opposed with ceramic group stored in 3 pH media for 24 h (24-H). Their SEM images showed a prominent wear scar on enamel cusp tip. There was a significant increase in surface roughness Ra of ceramic material after abrasive cyclic wear.Significance
Great attention should be paid to Ra of this type of glass ceramic even if it is considered as minimal values. It can induce a significant amount of enamel tooth wear after a period equivalent to one year of intra-oral function rather than the significantly higher surface Ra of such ceramic type can do. 相似文献9.
Yang Yang Franz-Xaver Reichl Jianwei Shi Xiuli He Reinhard Hickel Christof Högg 《Dental materials》2018,34(2):201-208
Objective
Previously, single composite components were used to study cytotoxicity and induction of DNA double-strand breaks (DNA-DSBs) of dental composite resins. In the present study, cytotoxicity and induction of DNA-DSBs in human gingival fibroblasts (HGFs) were investigated with dental composite eluates consisting of multiple components. The eluates were qualified and quantified.Methods
The composites Esthet.X® HD, Venus®, X-tra fil®, CLEARFIL? AP-X, Admira® Fusion and QuiXfil® were polymerized and immersed into Dulbecco’s modified Eagle’s medium (DMEM) for 72 h. Subsequently, HGFs were incubated with the corresponding composite eluates. The cell viability of HGFs was obtained from an XTT assay. DNA-DSBs were determined using a γ-H2AX assay. The qualification and quantification of eluates were performed by gas chromatography/mass spectrometry (GC/MS).Results
HGFs exposed to the eluates of all investigated composites showed no significant loss of cell viability, compared to negative control. Significant DNA-DSBs induction could be found in HGFs exposed to the eluates of Esthet.X® HD (0.43 ± 0.05 foci/cell) and Venus® (0.39 ± 0.04 foci/cell), compared to control (0.22 ± 0.03 foci/cell). A total of 12 substances were detected from the investigated composite eluates. Five of them were methacrylates: tetraethyleneglycol dimethacrylate (TEGDMA), 2-hydroxyethyl methacrylate (HEMA), hydroxypropyl methacrylate (HPMA), ethyleneglycol dimethacrylate (EGDMA) and trimethylolpropane trimethacrylate (TMPTMA). The highest concentration of HEMA (110.5 μM), HPMA (86.08 μM) and TMPTMA (4.50 μM) was detected in the eluates of QuiXfil®. The highest concentration of TEGDMA was 1080 μM in Venus® eluates and the highest concentration of EGDMA was 3.18 μM in Esthet.X® HD eluates.Significance
Significant DNA-DSBs induction can be found in HGFs exposed to the eluates of Esthet.X® HD and Venus®. The interactive effects among released (co)monomers and additives may influence the cytotoxicity and induction of DNA-DSBs, compared to exposure with single composite component. 相似文献10.
Mohit Kothari Vibeke Louise Funch Madsen Eduardo E. Castrillon Jørgen Feldbæk Nielsen Peter Svensson 《Journal of prosthodontic research》2018,62(2):268-272
Patients
High or excessive parafunctional jaw muscle activity is a frequent complication of acquired brain injury (ABI) and may have some similarities to bruxism. Bruxism has been associated with increased tooth wear, masseter hypertrophy and headaches. The aim of this observational study was to identify the levels of jaw muscle activity from fourteen ABI patients having different functional and cognitive levels in their early phase of neurological rehabilitation (according to their Ranchos Los Amigos Scale (RLAS) score). Nine patients were severely cognitive impairement (RLAS score 1–3): with no or little response to any external stimuli due to low arousal and five patients were with RLAS score 4–8: depending on responses to stimuli and confusion level i.e. defining that patients had enough arousal to respond and react and therefore were able to follow the instructions. A single-channel electromyographic (EMG) device was used to assess the jaw muscle EMG activity in ABI patients for two hours continuously at two different days.Discussion
The mean (± SD) jaw muscle activity observed in patients with ABI was 46.9 ± 6.5 EMG events/h with a wide range between 1–163 EMG events/h but with no significant difference between days (P = 0.230).Conclusion
Irrespective of functional and cognitive ability scores patients with ABI had a wide range of EMG activity. The use of ambulatory single-channel EMG devices might open a path for further studies to determine levels of jaw muscle activity associated with potential side effects in ABI patients. 相似文献11.
Objective
This study evaluated the capability of profilometry, microhardness, Optical Coherence Tomography (OCT) and Tandem Scanning Confocal Microscopy (TSM) in characterising the early erosive lesion in polished and natural human enamel in vitro.Methods
Polished (n = 60) and natural (n = 60) human enamel surfaces, were immersed and agitated in 0.3% citric acid erosion at 0 s, 10 s, 30 s, 60 s, 120 s, and 300 s (n = 10). Changes in the surface were measured with 3D-step height change (μm), surface roughness (μm), surface microhardness (KHN), and images were assessed qualitatively with OCT and TSM.Results
Mean (SD) 3D-step height change (μm) was measurable for polished enamel at: 60 s (0.24 ± 0.1), 120 s (1.16 ± 0.71), 300 s (2.01 ± 0.47; p < 0.05); a step height change was not detectable on acid challenged natural enamel surfaces. Mean (SD) surface roughness (μm) of polished enamel was detected at 10 s (0.270 ± 0.013; p < 0.05) and all erosion periods; and in natural enamel detected after 120 s (0.830 ± 0.125) and 300 s (0.800 ± 0.140; p < 0.005). Polished enamel Mean (SD) microhardness (KHN) statistically significantly decreased at all time points (p < 0.001); this was unmeasurable for natural enamel. Qualitative image analysis of both surface types indicated erosive change at the surface level, with progression after increasing erosion time.Significance
The early erosive lesion in polished enamel could be characterised quantitatively surface roughness and microhardness and qualitatively using OCT and TSM; whilst in natural enamel only surface roughness could be utilised. Further investigation of early erosion in natural enamel is required to develop new more clinically relevant models. 相似文献12.
Keita Taguchi Keiichi Hosaka Masaomi Ikeda Ryuzo Kishikawa Richard Foxton Masatoshi Nakajima Junji Tagami 《Journal of prosthodontic research》2018,62(3):330-336
Purpose
The use of warm air-blowing to evaporate solvents of one-step self-etch adhesive systems (1-SEAs) has been reported to be a useful method. The purpose of this study was to evaluate the effect of warm air-blowing on root canal dentin.Methods
Four 1-SEAs (Clearfil Bond SE ONE, Unifil Core EM self-etch bond, Estelink, BeautiDualbond EX) were used. Each 1-SEA was applied to root canal dentin according to the manufacturers’ instructions. After the adhesives were applied, solvent was evaporated using either normal air (23 ± 1 °C) or warm air (80 ± 1 °C) for 20 s, and resin composite was placed in the post spaces. The air from the dryer, which could be used in normal- or hot-air-mode, was applied at a distance of 5 cm above the root canal cavity in the direction of tooth axis. The temperature of the stream of air from the dryer in the hot-air-mode was 80 ± 1 °C, and in the normal mode, 23 ± 1 °C. After water storage of the specimens for 24 h, the μTBS were evaluated at the coronal and apical regions. The μTBSs were statistically analyzed using three-way ANOVA and Student’s t-test with Bonferroni correction (α = 0.05).Results
The warm air-blowing significantly increased the μTBS of all 1-SEAs at the apical regions, and also significantly increased the μTBS of two adhesives (Estelink and BeautiDualBond EX) at coronal regions.Conclusions
The μTBS of 1-SEAs to root canal dentin was improved by using warm air-blowing. 相似文献13.
Benedikt C. Spies Alexander Fross Erik Adolfsson Aimen Bagegni Sam Doerken Ralf-Joachim Kohal 《Dental materials》2018,34(10):1585-1595
Objective
To investigate the long-term stability of a metal-free zirconia two-piece implant assembled with a carbon fiber-reinforced (CRF) screw by means of transformation propagation, potential changes in surface roughness, the gap size of the implant-abutment connection, and fracture load values.Methods
In a combined procedure, two-piece implants made from alumina-toughened zirconia were dynamically loaded (107 cycles) and hydrothermally aged (85°, 60 days). Implants made from titanium (Ti) and a titanium–zirconium (TiZr) alloy with a titanium abutment screw served as control. Transformation propagation (ATZ) and gap size of the IAC were monitored at cross-sections by scanning electron microscopy (SEM). Furthermore, changes in surface roughness of ATZ implants were measured. Finally, implants were statically loaded to fracture. Linear regression models and pairwise comparisons were used for statistical analyses.Results
Independent of the implant bulk material, dynamic loading/hydrothermal aging did not decrease fracture resistance (p = 0.704). All test and control implants fractured at mean loads >1100 N. Gap size of the IAC remained stable (<5 μm) or decreased. None of the CFR screws fractured during static or dynamic loading. Monoclinic layer thickness of ATZ implants increased by 2–3 μm at surfaces exposed to water, including internal surfaces of the IAC. No changes in surface roughness were observed.Significance
Combined hydrothermal aging and dynamic loading did not affect the above-mentioned parameters of the evaluated two-piece ATZ implant. Mean fracture loads >1100 N suggest a reliable clinical application. 相似文献14.
Hilton Riquieri Jaiane Bandoli Monteiro Diogo Cabecinha Viegas Tiago Moreira Bastos Campos Renata Marques de Melo Guilherme de Siqueira Ferreira Anzaloni Saavedra 《Dental materials》2018,34(10):1483-1491
Objectives
The aim of this study was to characterize the microstructure of two zirconia-reinforced lithium silicate (ZLS) glass-ceramics and evaluate their mechanical properties before and after the crystallization firing process (CFP).Methods
Field emission-scanning electron microscope (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses were performed for microstructural characterization. To evaluate the pattern of crystallization and the molecular composition of ZLS glass-ceramics, was used X-ray diffraction (XRD). Vickers hardness, fracture toughness by the indentation method, and biaxial flexural strength were also measured. One hundred and forty ceramic discs were produced (diameter = 12 mm; thickness = 1.2 mm) and allocated among four groups (n = 30): Sfir, Sunf-ZLS Vita Suprinity; and Cfir and Cunf-ZLS Celtra Duo; fired and unfired, respectively. Statistical analysis was performed and Weibull failure probabilities were calculated.Results
Cfir showed the highest characteristic strength (251.25 MPa) and hardness (693.333 ± 10.85 GPa). Conversely, Sunf presented the lowest characteristic strength (106.95 MPa) and significantly lowest hardness (597.533 ± 33.97 GPa). According to Weibull analysis, Sunf had the highest structural reliability (m = 7.07), while Sfir presented the lowest (m = 5.38). The CFP was necessary to crystallize zirconia in the partially crystallized ZLS glass-ceramics. Sfir had a lower percentage of crystallized zirconia than did Cfir. Fractographic analyses showed that all failures initiated from an inherent critical defect in Sunf and from processing defects in the remaining groups.Significance
The CFP had a direct influence on the flexural strength and microstructural characteristics of both ZLS materials. 相似文献15.
Monika Astasov-Frauenhoffer Stephanie Glauser Jens Fischer Fredy Schmidli Tuomas Waltimo Nadja Rohr 《Dental materials》2018,34(11):1702-1709
Objectives
Monolithic zirconia, polymer-infiltrated ceramic and acrylate polymer cemented with resin composite cement have recently been identified as prosthetic treatment options for zirconia implants. The aim of the present study is to determine in vitro, to what extent bacteria adhere to these materials.Methods
Disks made of zirconia (Vita YZ [YZ]), polymer-infiltrated ceramic (Vita Enamic [VE]), acrylate polymer (Vita CAD-Temp [CT]), self-adhesive cement (RelyX Unicem 2 Automix [RUN]) and of two different adhesive cements (RelyX Ulimate [RUL] and Vita Adiva F-Cem [VAF]) were produced. The biofilm formation of three bacterial species (Streptococcus sanguinis, Fusobacterium nucleatum, Porphyromonas gingivalis) on each material was assessed over 72 h using a flow chamber system. The biofilms were quantified by crystal violet staining (optical density 595 nm) and visualized using SEM. The inorganic composition of the different materials was analyzed and the wettability of the specimens was measured.Results
For the restorative materials lowest biofilm formation was found on CT: OD 0.5 ± 0.1, followed by VE: OD 0.8 ± 0.1 and YZ: OD 1.4 ± 0.3. The biofilm formation on resin composite cements was significantly lower on VAF: OD 0.6 ± 0.1 than for RUL: OD 0.9 ± 0.1 and RUN: OD 1.0 ± 0.1. A high wettability of the specimens with saliva/serum mixture tended to result in a higher biofilm formation. Correlations were obtained between the organic/inorganic composition of the materials and the polar/dispersive part of the surface free energy.Significance
Three-species biofilm formation on restorative and cement materials strongly relies on the materials composition. If the restorative material CT and cement VAF also prevent excessive biofilm formation in a clinical situation should be further investigated. 相似文献16.
Satoshi Yamaguchi Renshirou Kani Kazuma Kawakami Manami Tsuji Sayuri Inoue Chunwoo Lee Wakako Kiba Satoshi Imazato 《Dental materials》2018,34(10):1578-1584
Objective
The aim of this study was to evaluate long-term fatigue behavior using an in vitro step-stress accelerated life test (SSALT), and to determine the crack initiation point using in silico finite element analysis for computer-aided designed and manufactured (CAD/CAM) molar crowns fabricated from three commercial CAD/CAM resin composite blocks: Cerasmart (CS; GC, Tokyo, Japan), Katana Avencia Block (KA; Kuraray Noritake Dental, Niigata, Japan), and Shofu Block HC (HC; Shofu, Kyoto, Japan).Methods
Fifty-one mandibular first molar crowns luted on a resin core die were embedded in acrylic resin and covered with a polyvinyl chloride tube. Single compressive tests were performed for five crowns. SSALT was conducted for 36 crowns using three profiles and reliabilities at 120,000 cycles, and a Weibull analysis was conducted. The maximum principal strain of each CAD/CAM resin composite crown model was analyzed by three-dimensional finite element analysis.Results
Fracture loads of CS and KA (3784 ± 144 N and 3915 ± 313 N) were significantly greater than that of HC (2767 ± 227 N) (p < 0.05). Fracture probabilities at 120,000 cycles were 24.6% (CS), 13.7% (KA), and 14.0% (HC). Maximum principal strain was observed around the mesiolingual cusps of CS and KA and the distobuccal cusp of HC.Significance
CAD/CAM resin composite molar crowns containing nano-fillers with a higher fraction of resin matrix exhibited higher fracture loads and greater longevity, suggesting that these crowns could be used as an alternative to ceramic crowns in terms of fatigue behavior. 相似文献17.
Takuya Kobayashi Masafumi Kubota Toshiyuki Takahashi Ayaka Nakasato Taro Nomura Junichi Furuya Hisatomo Kondo 《Journal of prosthodontic research》2018,62(3):337-341
Purpose
One of the most prominent issues in a super-aging society is the rapid increase in dementia patients. Cross-sectional studies in dentistry have indicated that patients with dementia have worse oral health compared to healthy people. The purpose of this study was to clarify the influence of tooth loss on brain structure by comparing the volumes of gray matter (GM) and white matter (WM) between edentulous and dentulous subjects.Methods
Subjects were recruited from the Denture Clinic at Iwate Medical University Hospital Dental Center. Experiments were performed on edentulous (5 males, 8 females, 81.8 ± 1.24 years) and dentulous subjects (4 males, 7 females, 77.1 ± 4.25 years). Patients with dementia were excluded from this study. Brain volumes of GM and WM in edentulous and dentulous subjects were compared using intracranial volume, age, gender and history of hypertension as covariates. Analyzed brain areas were identified by transforming the Montreal Neurological Institute coordinate into the anatomical coordinate in edentulous subjects.Results
The analysis of WM structural images found no morphological differences between dentulous and edentulous subjects. However, significant atrophy of GM was observed in the hippocampus, caudate nucleus and temporal pole of the right hemisphere in edentulous subjects.Conclusions
The results of this study suggest that tooth loss was a causal factor for volume reduction in brain areas related to memory, learning and cognition. 相似文献18.
Dong-Yeon Kim Ji-Hwan Kim Hae-Young Kim Woong-Chul Kim 《Journal of prosthodontic research》2018,62(1):56-64
Purpose
To evaluate the marginal and internal gaps of cobalt–chromium (Co–Cr) alloy copings fabricated using subtractive and additive manufacturing.Methods
A study model of an abutment tooth 46 was prepared by a 2-step silicone impression with dental stone. Fifteen stereolithography files for Co–Cr alloy copings were compiled using a model scanner and dental CAD software. Using the lost wax (LW), wax block (WB), soft metal block (SMB), microstereolithography (μ-SLA), and selected laser melting (SLM) techniques, 15 Co–Cr alloy copings were fabricated per group. The marginal and internal gaps of these Co–Cr alloy copings were measured using a digital microscope (160×), and the data obtained were analyzed using the non-parametric Kruskal–Wallis H-test and post-hoc Mann–Whitney U-test with Bonferroni correction.Results
The mean values of the marginal, axial wall, and occlusal gaps were 91.8, 83.4, and 163 μm in the LW group; 94.2, 77.5, and 122 μm in the WB group; 60.0, 79.4, and 90.8 μm in the SMB group; 154, 72.4, and 258 μm in the μ-SLA group; and 239, 73.6, and 384 μm in the SLM group, respectively. The differences in the marginal and occlusal gaps between the 5 groups were statistically significant (P < .05).Conclusions
The marginal gaps of the LW, WB, and SMB groups were within the clinically acceptable limit, but further improvements in the μ-SLA and SLM approaches may be required prior to clinical implementation. 相似文献19.
Izabela Cristina Maurício Moris Yung-Chung Chen Adriana Cláudia Lapria Faria Ricardo Faria Ribeiro Alex Sui-Lun Fok Renata Cristina Silveira Rodrigues 《Dental materials》2018,34(8):e197-e204
Objective
This study aimed to evaluate the fracture load and pattern of customized and non-customized zirconia abutments with Morse-taper connection.Methods
18 implants were divided into 3 groups according to the abutments used: Zr — with non-customized zirconia abutments; Zrc — with customized zirconia abutments; and Ti — with titanium abutments. To test their load capacity, a universal test machine with a 500-kgf load cell and a 0.5-mm/min speed were used. After, one implant-abutment assembly from each group was analyzed by Scanning Electron Microscopy (SEM). For fractographic analysis, the specimens were transversely sectioned above the threads of the abutment screw in order to examine their fracture surfaces using SEM.Results
A significant difference was noted between the groups (Zr = 573.7 ± 11.66 N, Zrc = 768.0 ± 8.72 N and Ti = 659.1 ± 7.70 N). Also, the zirconia abutments fractured while the titanium abutments deformed plastically. Zrc presented fracture loads significantly higher than Zr (p = 0.009). All the zirconia abutments fractured below the implant platform, starting from the area of contact between the abutment and implant and propagating to the internal surface of the abutment. All the zirconia abutments presented complete cleavage in the mechanical test. Fractography detected differences in the position and pattern of fracture between the two groups with zirconia abutments, probably because of the different diameters in the transmucosal region.Significance
Customization of zirconia abutments did not affect their fracture loads, which were comparable to that of titanium and much higher than the maximum physiological limit for the anterior region of the maxilla. 相似文献20.