Department of Stomatognathic Physiology and Prosthetic Dentistry, University of Helsinki, Finland. Mauno.Kononen@Helsinki.Fi
Titanium is known as a useful biometal because of its good biocompatibility and mechanical performance. However, titanium is chemically an exceptional metal, reacting strongly with gaseous elements like oxygen, hydrogen, and nitrogen and also dissolving them extensively. This high reactivity causes problems, for example, when dental ceramics are fused to titanium. Commercial ceramic-titanium systems are increasingly used in prosthetic dentistry, but little is known about the microstructure and composition of the system. Better understanding of chemical reactions between ceramics and titanium is necessary if mechanically more compatible ceramic-titanium bonds are to be developed. This review deals with titanium as a metal, titanium's affinity for nonmetallic elements (especially oxygen), and reactions with other elements. Different aspects are discussed relative to the fusing of dental ceramics to titanium.
Acta Odontol Scand. 2010 Jan 25;: 20095949
Department of Prosthetic Dentistry, Faculty of Odontology, Malmö University, Malmö, Sweden.
Abstract Objectives. The aims of this literature review are to provide answers to questions on how to improve bonding between titanium and dental porcelain and how to further implement, in clinical practice, ceramic-veneered titanium as an alternative to conventional metal-ceramic systems. Material and methods. A literature search of PubMed and also among referenced published scientific papers was performed and 24 fulfilled the search criteria, namely mentions of titanium, ceramics and bond strength. These papers were compiled for comparison and evaluated regarding the bond strength achieved with different methods. Results. The results strongly indicate that there are possibilities to improve both the present materials and methods for titanium-ceramic veneering. Conclusions. The results indicate that present knowledge is sufficient to conclude that veneering titanium with low-fused porcelain for crowns and fixed partial dentures can be recommended for routine clinical use.
Dent Mater. 2008 Aug 19;: 18718654
Evaluation of interface characterization and adhesion of glass ceramics to commercially pure titanium and gold alloy after thermal- and mechanical-loading.
São Paulo State University, Department of Dental Materials and Prosthodontics, São José dos Campos, Brazil.
OBJECTIVES: This study evaluated the effect of thermal- and mechanical-cycling on the shear bond strength of three low-fusing glassy matrix dental ceramics to commercial pure titanium (cpTi) when compared to conventional feldspathic ceramic fused to gold alloy. METHODS: Metallic frameworks (diameter: 5mm, thickness: 4mm)(N=96, n=12 per group) were cast in cpTi and gold alloy, airborne particle abraded with 150mum aluminum oxide. Low-fusing glassy matrix ceramics and a conventional feldspathic ceramic were fired onto the alloys (thickness: 4mm). Four experimental groups were formed; Gr1 (control group): Vita Omega 900-Au-Pd alloy; Gr2: Triceram-cpTi; Gr3: Super Porcelain Ti-22-cpTi and G4: Vita Titankeramik-cpTi. While half of the specimens from each ceramic-metal combination were randomly tested without aging (water storage at 37 degrees C for 24h only), the other half were first thermocycled (6000 cycles, between 5 and 55 degrees C, dwell time: 13s) and then mechanically loaded (20,000 cycles under 50N load, immersion in distilled water at 37 degrees C). The ceramic-alloy interfaces were loaded under shear in a universal test machine (crosshead speed: 0.5mm/min) until failure occurred. Failure types were noted and the interfaces of the representative fractured specimens from each group were examined with stereomicroscope and scanning electron microscope (SEM). In an additional study (N=16, n=2 per group), energy dispersive X-ray spectroscopy (EDS) analysis was performed from ceramic-alloy interfaces. Data were analyzed using ANOVA and Tukey's test. RESULTS: Both ceramic-metal combinations (p<0.001) and aging conditions (p<0.001) significantly affected the mean bond strength values. Thermal- and mechanical-cycling decreased the bond strength (MPa) results significantly for Gr3 (33.4+/-4.2) and Gr4 (32.1+/-4.8) when compared to the non-aged groups (42.9+/-8.9, 42.4+/-5.2, respectively). Gr1 was not affected significantly from aging conditions (61.3+/-8.4 for control, 60.7+/-13.7 after aging)(p>0.05). Stereomicroscope images showed exclusively adhesive failure types at the opaque ceramic-cpTi interfacial zone with no presence of ceramic on the substrate surface but with a visible dark titanium oxide layer in Groups 2-4 except Gr1 where remnants of bonder ceramic was visible. EDS analysis from the interfacial zone for cpTi-ceramic groups showed predominantly 34.5-85.1% O(2) followed by 1.1-36.7% Al and 0-36.3% Si except for Super Porcelain Ti-22 where a small quantity of Ba (1.4-8.3%), S (0.7%) and Sn (35.3%) was found. In the Au-Pd alloy-ceramic interface, 56.4-69.9% O(2) followed by 15.6-26.2% Si, 3.9-10.9% K, 2.8-6% Na, 4.4-9.6% Al and 0-0.04% Mg was observed. SIGNIFICANCE: After thermal-cycling for 6000 times and mechanical-cycling for 20,000 times, Triceram-cpTi combination presented the least decrease among other ceramic-alloy combinations when compared to the mean bond strength results with Au-Pd alloy-Vita Omega 900 combination.
Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Thivon 2, Athens 115 27, Greece. firstname.lastname@example.org
OBJECTIVES To investigate the bond strength between cpTi and low fusing porcelains after different treatments. METHODS 72 patterns were covered with a ceramic coating and invested with phosphate-bonded material (group A), another 72 were invested with magnesia material (group B) and all cast with cpTi. 31 solid castings were selected from each group. The castings of group B were ground and sandblasted, while the castings of group A were only sandblasted. Aluminum content of the metal surface was determined by EDS and castings were submitted to a 3-point bending test to determine the modulus of elasticity (E). The porcelains Duceratin Plus, Noritake Ti22 and Triceram were applied respectively and specimens were submitted to a 3-point bending test. The fracture mode and the remaining porcelain were determined by optical microscopy and SEM/EDS. Bond strength and fracture mode were calculated by two-way ANOVA. RESULTS The E of groups A and B was 98.3 GPa and 98.6 GPa respectively. The bond strength was 26+/-3 MPa (Duceratin Plus), 28+/-3 MPa (Noritake Ti22), 27+/-2 MPa (Triceram) for group A and 24+/-1 MPa, 29+/-2 MPa, 27+/-1 MPa for group B respectively. No significant differences were found for the same porcelain between the two groups (p<0.05). A significant difference was found between Duceratin Plus and Noritake Ti22, for group B (p<0.05). The mode of failure was mainly adhesive for all specimens. A significant reduction in aluminum was recorded in all subgroups. SIGNIFICANCE The special coating of patterns makes the Ti casting procedure inexpensive, without reducing the metal-ceramic bond strength.
Mechanical and thermal cycling effects on the flexural strength of glass ceramics fused to titanium.
São Jose dos Campos Dental School, Department of Dental Materials and Prosthodontics, São Paulo State University, São Jose dos Campos, Brazil.
This study evaluated the effects of mechanical and thermal cycling on the flexural strength (ISO 9693) of three brands of ceramics fused to commercially pure titanium (cpTi). Metallic frameworks of 25 x 3 x 0.5 mm dimensions (N= 84) were cast in cpTi, followed by 150- microm aluminum oxide airborne particle abrasion at a designated area of the frameworks (8 x 3 mm). Bonder and opaque ceramic were applied on the frameworks, and then the corresponding ceramic (Triceram, Super Porcelain Ti-22, Vita Titankeramik) was fired onto them (thickness: 1 mm). Half of the specimens from each ceramic-metal combination were randomly tested without aging (only water storage at 37 degrees C for 24 hours), while the other half were mechanically loaded (20,000 cycles under 10 N load, immersion in distilled water at 37 degrees C) and thermocycled (3,000 cycles, between 5-55 degrees C, dwell time of 13 seconds). After the flexural strength test, failure types were noted. Mechanical and thermal cycling decreased the mean flexural strength values significantly (p<0.05) for all the three ceramic-cpTi combinations tested when compared to the control group. In all the three groups, failure type was exclusively adhesive at the opaque ceramic-cpTi interfacial zone with no presence of ceramic on the substrate surface except for a visible oxide layer.
Department of Prosthodontics, Araras Dentistry School, Herminio Ometto University, Uniararas, Rua Ipiranga 1034/12, CEP: 13400-480 Piracicaba, SP, Brazil. email@example.com
OBJECTIVES Titanium-ceramic restorations are currently used, despite the pending problem of titanium-ceramic bonding, which has only been partially solved. The surface treatment of the metal proposed by the manufacturer promotes lower bond strength between titanium and porcelain when compared to the conventional metal-ceramic systems. The objective of this study was to evaluate the influence of acid and caustic baths on the bonding characteristics of specific titanium porcelain bonded to cast commercially pure titanium (CP Ti). METHODS Eighty strips of cast CP Ti were obtained in dimensions of 25mm x 3mm x 0.5mm, and divided into eight groups (n=10) which were subjected to surface treatment by immersion in one of the follow solutions-group HF: HF 10%; group NaOH+HF: NaOH 50%-CuSO(4).5H(2)O 10% followed by HF 10%; group HCl: HCl 35%; group NaOH+HCl: NaOH 50%-CuSO(4).5H(2)O 10% followed by HCl 35%; group HNO(3): HNO(3) 35%-HF 5%; group NaOH+HNO(3): NaOH 50%-CuSO(4).5H(2)O 10% followed by HNO(3) 35%-HF 5%; control group: treated according to the manufacturer's instructions; NaOH+control group: treated according to the manufacturer's instructions followed by immersion in NaOH 50%-CuSO(4).5H(2)O 10%. Low fusion porcelain (Vita Titankeramik) was applied to the center of one of the sides of each CP Ti sample with dimensions of 8mm x 3mm x 1mm. All groups were submitted to a three-point flexure test. Scanning electron microscopy (SEM) photomicrographs were taken to characterize the failed surfaces at the titanium-porcelain interface. Anova and Tukey's multiple comparison tests were used to analyze the data at a 5% probability level. RESULTS All groups treated with NaOH 50%-CuSO(4).5H(2)O 10% solution showed significant superior values when compared to groups treated exclusively with acid solution. There were no significant differences between HF (21.2MPa) and HCl (23.4MPa) groups; control (25.2MPa), HCl (23.4MPa) and HNO(3)(26.6MPa) groups; NaOH+HF (29.9MPa) and NaOH+HCl (30.8MPa) groups; NaOH+HNO(3)(34.8MPa) and NaOH+control (32.1MPa) groups. SEM analysis indicated a combination of cohesive and adhesive fractures in NaOH+HNO(3) and NaOH+control groups, while mainly adhesive fractures were found in the other groups. SIGNIFICANCE Bond strength between porcelain and cast CP Ti can be increased by use of a caustic bath prior to porcelain firing.
Effects of sandblasting and electrical discharge machining on porcelain adherence to cast and machined commercially pure titanium.
Department of Prosthodontics, Faculty of Dentistry, University of Selcuk, Konya, Türkiye.
The aim of this study was to determine the effect of sandblasting and electrical discharge machining (EDM) on cast and machined titanium surfaces and titanium-porcelain adhesion. Twenty machined titanium specimens were prepared by manufacturer (groups 1 and 2). Thirty specimens were prepared with autopolymerizing acrylic resin. Twenty of these specimens (groups 3 and 4) were cast with commercially pure titanium and the alpha-case layer was removed. For control group (group 5), 10 specimens were cast by using NiCr alloy. Groups 2 and 4 were subjected to EDM while groups 1, 3, and 5 were subjected to sandblasting. Surface examinations were made by using a scanning electron microscope (SEM). A low-fusing porcelain was fused on the titanium surfaces, whereas NiCr specimens were covered using a conventional porcelain. Titanium-porcelain adhesion was characterized by a 3-point bending test. Results were analyzed by Kruskal-Wallis and Mann-Whitney U tests. Metal-porcelain interfaces were characterized by SEM. The bond strength of control group was higher than that of the titanium-porcelain system. There was no significant difference between cast and machined titanium groups (p > 0.05). There was no significant difference between EDM and sandblasting processes (p > 0.05). The use of EDM as surface treatment did not improve titanium-porcelain adhesion compared with sandblasting.(c) 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006.
Dent Mater. 2005 Aug ;21 (8):773-9 15876452
Department of Prosthodontics, Faculty of Dentistry, Cukurova University, Balcali, 01330 Adana, Turkey.
OBJECTIVES This study investigated the effect of silicon coating (SiO2) by magnetron sputtering on bond strength of two different titanium ceramics to titanium. METHODS Sixty cast titanium specimens were prepared following the protocol ISO 9693. Titanium specimens were divided into two test and control groups with 15 specimens in each. Test groups were silicon coated by the magnetron sputtering technique. Two titanium ceramics (Triceram and Duceratin) were applied on both test (coated) and control (uncoated) metal specimens. The titanium-ceramic specimens were subjected to a three point flexural test. The groups were compared for their bond strength. SEM and SEM/EDS analyses were performed on the delaminated titanium surfaces to ascertain bond failure. RESULTS The mean bond strength of Ti-Duceratin, Ti-Triceram, Si-coated Ti-Duceratin and Si-coated Ti-Triceram were 17.22+/-2.43, 23.31+/-3.18, 23.21+/-3.81 and 24.91+/-3.70 MPa, respectively. While the improvement in bond strength was 30% for Duceratin, it was statistically insignificant for Triceram. An adhesive mode of failure was observed in the Duceratin control group. In the silicoated Duceratin specimen, the bonded ceramic boundaries were wider but less than in the silicoated Triceram specimen. In the coated Triceram specimen, the ceramic retained areas were frequent and the failure mode was generally cohesive. SIGNIFICANCE Silicon coating was significantly effective in both preventing titanium oxide layer formation and in improving bond strength for Duceratin. However, it was of less value for Triceram.
Department of Materials Science and Engineering, Chonnam National University, Kwangju 500-757, South Korea.
The adhesion between titanium and dental porcelain is related to the diffusion of oxygen to the reaction layer formed on cast-titanium surfaces during porcelain firing. The diffusion of oxygen could be suppressed by coating the titanium surface with a thin gold layer. This study characterized the effects of gold coating on titanium-ceramic adhesion. ASTM grade II CP titanium was cast into a MgO-based investment (Selevest CB, Selec). The specimen surfaces were air abraded with 110-microm Al(2)O(3) particles. Gold coating was applied on titanium surfaces by three methods: gold-paste (Deck Gold NF, Degussa-Ney) coating and firing at 800 degrees C for three times, single gold-paste coating and firing followed by sputter coating (40 mA, 500 s), and sputter coating (40 mA, 1000 s). Surfaces only air abraded with Al(2)O(3) particles were used as controls. An ultra-low-fusing dental porcelain (Vita Titankeramik, Vident) was fused on titanium surfaces. Specimen surfaces were characterized by SEM/EDS and XRD. The titanium-ceramic adhesion was evaluated by a biaxial flexure test (N = 8), and area fraction of adherent porcelain (AFAP) was determined by EDS. Numerical results were statistically analyzed by one-way ANOVA and the Student-Newman-Keuls test at alpha = 0.05. SEM fractography showed a substantial amount of porcelains remaining on the gold-sputter-coated titanium surfaces. A new Au(2)Ti phase was found on gold-coated titanium surface after the firing. Significantly higher (p <.05) AFAP values were determined for the gold-sputter-coated specimens compared to the others. No significant differences were found among the other groups and the control. Results suggested that gold coatings used in this study are not effective barriers to completely protect titanium from oxidation during the porcelain firing, and porcelain adherence to cast titanium can be improved by gold-sputter coating used in the present study.
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Institute of Dentistry, University of Helsinki, P.O. Box 41, University of Helsinki, FIN-00014 Helsinki, Finland.
Clinical studies indicate that soft tissue responses around dental implants vary, depending on the material used. It is therefore also possible that there are differences in how epithelial cells attach to various biomaterial surfaces. We studied the adhesion of cultured epithelial cells to five different dental material surfaces and to glass. The efficacy of adhesion was evaluated by using scanning electron microscopy (SEM) and immunofluorescence microscopy (IF) with antibodies to vinculin and alpha(6)beta(4) integrin, two cell surface molecules that are functional in epithelial cell adhesion. Our results indicate that epithelial cells adhere and spread more avidly on metallic surfaces (titanium, Ti(6)Al(4)V titanium alloy, dental gold alloy) than on ceramic surfaces (dental porcelain, aluminum oxide). As revealed by SEM, cells on metallic surfaces had a flattened morphology and formed multicellular islands. On porcelain and aluminum oxide most cells were round and adhesion occurred as single cells. Surface coverage was over twofold on metallic surfaces as compared to ceramic surfaces. IF of cells grown on metallic surfaces revealed vinculin in well-organized focal contacts and alpha(6)beta(4) integrin in punctate patterns typical of prehemidesmosomes. On porcelain and aluminum oxide surfaces the cells were mostly round and showed less well-organized adhesion complexes. Our results indicate that smooth metallic biomaterial surfaces are optimal for epithelial cell adhesion and spreading. These findings may have clinical implications in the design of transgingival implant structures.
Department of Prosthetic Dentistry, University of Helsinki, Finland.
The objective of the investigation was to study the basic problems related to the firing of dental porcelain to commercially pure titanium. The firing of a low-fusing porcelain to sandblasted or electrolytically polished titanium was carried out in an ordinary dental furnace. The interfacial regions between the ceramic coatings and titanium were analyzed using scanning acoustic microscopy (C-SAM) and scanning electron microscopy (SEM) techniques. Thermal stresses in the joints were evaluated by means of a finite element model based on multilayer elastic strain analysis. The chemical reactions and their formation sequence at 750 degrees C was predicted thermodynamically and observed experimentally both at 750 and 800 degrees C. The C-SAM results gave evidence that the integrity of the porcelain-titanium joints are better in the sandblasted samples than in the electropolished ones, where defects were larger. SEM analyses of the same samples confirmed the C-SAM findings. Because the reaction layers are more continuous in the electropolished samples, cracks propagated more readily in these samples during the cooling procedure. Both thermodynamic calculations and experimental chemical analyses strongly indicate that the cause for the cracking of the reaction zone is thin layer of Ti (oxo)silicide and/or a relatively thick solid solution layer of Ti and oxygen.
Department of Prosthetic Dentistry, University of Helsinki.
The objective of the investigation was to compare the results obtained from examination of titanium-porcelain joints by means of both scanning acoustic microscopy (C-SAM) and scanning electron microscopy (SEM). A dental porcelain (Ducera, Dental GmbH) mechanically compatible with titanium was fired to sand-blasted or electrolytically polished commercially pure titanium (grade 1) specimens. The firing was carried out in an ordinary dental furnace according to manufacturer's instructions. There was a good correlation between the C-SAM and SEM methods regarding the ability to detect air-filled defects in the porcelain/titanium interface. The results show that the C-SAM method, being non-destructive as well as time-and-money-saving, can be useful in the testing of metal-ceramic joints.
Immunolocalization of proteins specific for adhaerens junctions in human gingival epithelial cells grown on differently processed titanium surfaces.
Department of Periodontology, University of Helsinki, Finland.
The localization of desmoplakins 1 and 2 (DP 1&2), components of desmosomes, vinculin, and actin, was studied in gingival epithelial cells grown on cell culture glass and on titanium plates with various surface topography. The results showed that epithelial cells attached and spread more readily on smooth than on rough, sandblasted titanium surfaces. Moreover, the cells appeared to develop more granular DP 1&2 immunoreactivity at their ventral surfaces when grown on smooth or etched titanium as compared to glass. In cells grown on sandblasted titanium surfaces, DP 1&2-specific immunoreactivity was primarily located at cell-cell contacts. Cells grown on smooth titanium surfaces harbored a fine network of actin filaments with apparent cell-to-cell organization. Vinculin was confined to cell-cell contact areas. No vinculin-containing focal adhesions could be detected, suggesting that the cells adhere either by means of close contacts, extracellular matrix contacts, or by means of hemidesmosomes. The findings suggest that smooth of finely grooved titanium surfaces could be optimal in maintaining the adhesion and specialized phenotype of gingival epithelial cells.
Effect of surface processing on the attachment, orientation, and proliferation of human gingival fibroblasts on titanium.
Department of Prosthetic Dentistry, University of Helsinki, Finland.
The adhesion, orientation, and proliferation of human gingival fibroblasts was studied on electropolished (elpTi), etched (etchTi), and sandblasted (sblTi) titanium surfaces. The texture, chemical state, and composition of the titanium surfaces were analyzed using a surface tracing instrument and electron spectroscopy for chemical analysis. Considerable differences were evident in the surface texture and chemical composition of the differently treated titanium plates. Electropolishing produced the smoothest and cleanest surface. Human gingival fibroblasts attached, spread, and proliferated on all titanium surfaces. However, cells on elpTi exhibited an extremely flat morphology and seemed to form cellular bridges with adjacent cells, whereas the etchTi and sblTi surfaces harbored both round and flat cells with many long processes. Cells on elpTi appeared to grow in thick layers with no specific orientation, whereas on etchTi surfaces they were migrating along the parallel, irregular minor grooves caused by mechanical polishing, and on sblTi surfaces they seemed to grow in clusters. Stress-fiber type actin bundles and vinculin-containing focal adhesions were present in cells spreading on elpTi and etchTi surfaces but not in cells spreading on sblTi surfaces. Cell shape, orientation, and proliferation appear to depend on the texture of the titanium surface and probably also on the properties of the oxide layer and adjacent bulk material. Our findings suggest that smooth or finely grooved titanium surfaces could be optimal in implants adjacent to soft tissues as they support the attachment and growth of human gingival fibroblasts.
J Oral Rehabil. 2012 Aug 17;: 22897247
Department of Prosthetic Dentistry and Stomatognathic Physiology, Institute of Dentistry, University of Oulu, Oulu, Finland; Institute of Dentistry, University of Eastern Finland, Kuopio, Finland; Department of Oral and Maxillofacial, Kuopio University Hospital, Kuopio, Finland.
Studies concerning the role of denture status on in temporomandibular disorders (TMD) are scarce. The aim of this study was to evaluate the association of tooth loss and denture status with clinical findings of TMD. The data were obtained from 6316 subjects aged ≥30 years from the Finnish Health 2000 Survey. The associations between clinically assessed TMD findings and number of teeth, wearing of removable dentures, need for denture repair and age of the dentures were analysed by means of chi-square test and logistic regression. Among women after adjusting for age, having fewer teeth or wearing complete dentures associated with restricted maximum interincisal distance and pain on palpation of the temporomandibular joints (TMJ) and masticatory muscles. After adding education level and depression in the model, the associations between TMJ pain and explanatory variables were weakened. Among men, having a higher number of teeth associated with occurence of TMJ crepitation. Subjective need for repair of dentures and having a denture aged ≥5 years associated with pain on palpation in masticatory muscles among women. Among men, both the objective and subjective need for denture repair and having at least one denture aged ≥5 years or been repaired during the past 5 years associated negatively with the presence of TMJ crepitation. It can be concluded that edentulousness, wearing of complete dentures and poor condition of dentures associate with pain-related TMD findings among women. Psychosocial factors have a modifying effect on these associations.
Sensorimotor, visual, and auditory cortical atrophy in Unverricht-Lundborg disease mapped with cortical thickness analysis.
Department of Clinical Radiology, Kuopio University Hospital, Puijonlaaksontie 2, FIN-70210 Kuopio, Finland. firstname.lastname@example.org
BACKGROUND AND PURPOSE EPM1, caused by mutations in the CSTB gene, is the most common form of PME. The most incapacitating symptom of EPM1 is action-activated and stimulus-sensitive myoclonus. The clinical severity of the disease varies considerably among patients, but so far, no correlations have been observed between quantitative structural changes in the brain and clinical parameters such as duration of the disease, age at onset, or myoclonus severity. The aim of this study was to evaluate possible changes in CTH of patients with EPM1 compared with healthy controls and to correlate those changes with clinical parameters. MATERIALS AND METHODS Fifty-three genetically verified patients with EPM1 and 70 healthy volunteers matched for age and sex underwent 1.5T MR imaging. T1-weighted 3D images were analyzed with CTH analysis to detect alterations. The patients were clinically evaluated for myoclonus severity by using the UMRS. Higher UMRS scores indicate more severe myoclonus. RESULTS CTH analysis revealed significant thinning of the sensorimotor and visual and auditory cortices of patients with EPM1 compared with healthy controls. CTH was reduced with increasing age in both groups, but in patients, the changes were confined specifically to the aforementioned areas, while in controls, the changes were more diffuse. Duration of the disease and the severity of myoclonus correlated negatively with CTH. CONCLUSIONS Cortical thinning in the sensorimotor areas in EPM1 correlated significantly with the degree of the severity of the myoclonus and is most likely related to the widespread stimulus sensitivity in EPM1.
Functional MRI and motor behavioral changes obtained with constraint-induced movement therapy in chronic stroke.
Department of Clinical Radiology, Kuopio University Hospital, Kuopio, Finland.
BACKGROUND The clinical benefits of intensive stroke rehabilitation vary individually. We used multimodal functional imaging to assess the relationship of clinical gain and imaging changes in patients with chronic stroke whose voluntary motor control improved after constraint-induced movement therapy (CIMT). METHODS Eleven patients (37.6 ± 36.8 months from stroke) were studied by functional MRI (fMRI), transcranial magnetic stimulation (TMS), and behavioral assessment of hand motor control (Wolf Motor Function Test) before and after 2 weeks of CIMT. Individual and group-level changes in imaging and behavioral parameters were investigated. RESULTS Increase in fMRI activation in the sensorimotor areas was greater amongst those subjects who had poor hand motor behavior before therapy and/or whose motor behavior improved notably because of therapy than amongst subjects with relatively good motor behavior already before therapy. The magnitude of CIMT-induced changes in task-related fMRI activation differed between lesioned and non-lesioned hemispheres, and the fMRI laterality index was different for paretic and non-paretic hand tasks. The corticospinal conduction time in TMS was significantly decreased after CIM therapy. CONCLUSIONS Alterations in sensorimotor cortical activations (fMRI) and corticospinal conductivity (TMS) were observed after intensive rehabilitation in patients with chronic stroke. Activation and functional changes in fMRI and TMS correlated significantly with the degree of clinical improvement in hand motor behavior. The present data advance the understanding of the functional underpinnings of motor recovery, which may be obtained even years after the stroke.
Awareness of tooth grinding and clenching from adolescence to young adulthood: a nine-year follow-up.
Institute of Dentistry, University of Helsinki, Helsinki, Finland.
Summary How bruxism develops from adolescence to early adulthood remains unclear. A previous database was revisited to evaluate the natural course of self-reported tooth grinding and clenching among young Finns aged 14-23 using four assessments. Overall, the self-reported frequencies of both grinding and clenching increased during the examination period: from 13.7% to 21.7% and from 9.2% to 14.8%, respectively. There were significant increases (without a statistically significant difference between genders) in both grinding (P = 0.002) and clenching (P = 0.015) between 15 and 23 years. A significant rise in grinding between 18 and 23 years was also found (P = 0.011). It is concluded that self-reported bruxism increases from adolescence to young adulthood. Moreover, there are large differences between individuals, and fluctuations may occur in the natural course of bruxism.
Atrophic Enlargement of CSF Volume after Subarachnoid Hemorrhage: Correlation with Neuropsychological Outcome.
Departments of Clinical Radiology, Neurosurgery, Neurology, Physics, and Clinical Neurophysiology, Kuopio University Hospital and University of Kuopio, Finland.
BACKGROUND AND PURPOSE: Ventricular dilation and sulcal enlargement are common sequelae after aSAH. Our aim was to quantify the late ventricular dilation and volumes of the CSF spaces after aSAH and to determine if they correlate with neurologic and cognitive impairments frequently detected in these patients. MATERIALS AND METHODS: 3D T1-weighted images needed for volumetry were available in 76 patients 1 year after aSAH, along with 75 neuropsychological assessments. Volumes of CSF segments and ICV were quantified by SPM in 76 patients and 30 control subjects to determine CSF/ICV ratios. The mCMI was calculated to roughly evaluate the ventricular dilation. The contributing factors for enlarged ventricles and CSF volumes were reviewed from radiologic, clinical, and neuropsychological perspectives. RESULTS: The mCMI was higher in patients with aSAH (0.23 +/- 0.06) compared with control subjects (0.20 +/- 0.04; P =.020). In line with these planimetric measurements, the SPM-based CSF/ICV ratios were higher in patients with aSAH (35.58 +/- 7.0) than in control subjects (30.36 +/- 6.25; P =.001). Preoperative hydrocephalus, higher HH and Fisher grades, and focal parenchymal lesions on brain MR imaging, but not the treatment technique, were associated with ventricular enlargement. The clinical outcome and presence of neuropsychological deficits correlated significantly with CSF enlargement. CONCLUSIONS: Ventricular and sulcal enlargement, together with reduced GM volumes, after aSAH may indicate general atrophy rather than hydrocephalus. Enlarged CSF spaces correlate with cognitive deficits after aSAH. A simple measure, mCMI proved to be a feasible tool to assess the diffuse atrophic brain damage after aSAH.
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Department of Biology, Section of Ecology, University of Turku, FI-20014 Turku, Finland.
Metals can cause oxidative stress by increasing the formation of reactive oxygen species (ROS), which render antioxidants incapable of defence against growing amounts of free radicals. Metal toxicity is related to their oxidative state and reactivity with other compounds. Our aim is to review the mechanisms on how metals cause oxidative stress and what is known about metal-induced oxidative stress in wildlife. Taking birds as model organisms, we summarize the mechanisms responsible for antioxidant depletion and give a view of how to detect metal-induced oxidative stress in birds by using different biomarkers. The mechanisms producing the harmful effects of oxidative stress are complex with different biomolecular mechanisms associated with ecotoxicological and ecological aspects. The majority of the studies concerning metals and ROS related to oxidative stress have focused on the biomolecular level, but little is known about the effects at the cellular level or at the level of individuals or populations.
Department of Mathematics, Shanghai University, Shanghai 200444, PR China.
Some biochemical processes do not occur instantaneously but have considerably delays associated with them. In the existed methods which solve these chemically reacting systems with delays, averaging over a great deal of simulations is needed for reliable statistical characters. Here we present an accelerating approach, called the "Delay Final All Possible Steps"(DFAPS) approach, which does not alter the course of stochastic simulation, but reduces the required running times. Numerical simulation results indicate that the proposed method can be applied to a wide range of chemically reacting systems with delays and obtain a significant improvement on efficiency and accuracy over the existed methods.
Renato Morales Joias, Rubens Nisie Tango, Jose Eduardo Junho de Araujo, Maria Amelia Junho de Araujo, Guilherme de Siqueira Ferreira Anzaloni Saavedra, Tarcisio Jose de Arruda Paes-Junior, Estevao Tomomitsu Kimpara
Department of Dental Sculpture, Occlusion, and Prosthodontics, Methodist University of Sao Paulo, Sao Bernardo do Campo, Sao Paulo, Brazil.
STATEMENT OF PROBLEM Different combinations of Co-Cr alloys bonded to ceramic have been used in dentistry; however, the bond strength of ceramic to metal can vary because of different compositions of these alloys. PURPOSE The purpose of this study was to evaluate the shear bond strength of a dental ceramic to 5 commercially available Co-Cr alloys. MATERIAL AND METHODS Five Co-Cr alloys (IPS d.SIGN 20, IPS d.SIGN 30, Remanium 2000, Heranium P, and Wirobond C) were tested and compared to a control group of an Au-Pd alloy (Olympia). Specimen disks, 5 mm high and 4 mm in diameter, were fabricated with the lost-wax technique. Sixty specimens were prepared using opaque and dentin ceramics (VITA Omega 900), veneered, 4 mm high and 4 mm in diameter, over the metal specimens (n=10). The shear bond strength test was performed in a universal testing machine with a crosshead speed of 0.5 mm/min. After shear bond testing, fracture surfaces were evaluated in a stereomicroscope under x25 magnification. Ultimate shear bond strength (MPa) data were analyzed with 1-way ANOVA and the Tukey HSD test (alpha =.05). RESULTS The mean (SD) bond strengths (MPa) were: 61.4 (7.8) for Olympia; 94.0 (18.9) for IPS 20; 96.8 (10.2) for IPS 30; 75.1 (12.4) for Remanium; 71.2 (14.3) for Heranium P; and 63.2 (10.9) for Wirobond C. Mean bond strengths for IPS 20 and IPS 30 were not significantly different, but were significantly (P<.001) higher than mean bond strengths for the other 4 alloys, which were not significantly different from each other. CONCLUSIONS Bond strength of a dental ceramic to a Co-Cr alloy is dependent on the alloy composition.
Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, USA.
The open-shell benzoylnitrene radical anion, readily generated by electron ionization of benzoylazide, undergoes unique chemical reactivity with radical reagents and Lewis acids in the gas phase. Reaction with nitric oxide, NO, proceeds by loss of N2 and formation of benzoate ion. This novel reaction is also observed to occur with phenylnitrene anion, forming phenoxide. Similar reactivity was observed in the reaction between benzoylnitrene radical anion and NO2, forming benzoate ion and nitrous oxide. Electronic structure calculations indicate that the reaction has a high-energy barrier that is overcome by the energy released by bond formation. Benzoylnitrene radical anion also transfers oxygen anion to NO and NO2 as well as to CS2 and SO2. In contrast, phenylnitrene anion reacts with carbon disulfide by C+ or CS+ abstraction, forming S- or S2-. Electronic structure calculations indicate that benzoylnitrene in the ground state resembles a slightly polarized benzoate anion, but with a free radical localized on the nitrogen.
Centre for Research in Molecular Modeling and Department of Chemistry and Biochemistry, Concordia University, 7141 Sherbrooke Street West, Montreal, Quebec H4B 1R6, Canada.
A comparative study of the concerted hydrolysis of H-, CF3-, CH3-, and Ph-substituted N-sulfinylamines (R-NSO) and isocyanates (R-NCO) was performed using B3LYP/6-31+G(2d,2p). The "two-water-molecule" model was found to be sufficient for a proper description of the hydrolysis reaction for both classes of compounds. Despite their overall similar reactivity, N-sulfinylamines react across both the N=S and the S=O bonds, whereas isocyanates hydrolyze predominantly through the N=C bond, in agreement with the proton affinities of the nitrogen and oxygen atoms. The charges on sulfur (N=S=O) and carbon (N=C=O) were found to correlate well with the activation enthalpy for hydrolysis. While the reactivity of an N-sulfinylamine toward water increases with increasing electron-withdrawing ability of the substituent, the substituent effect on isocyanates becomes notable only in the presence of the strongly electron-withdrawing CF3 group.
Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA. email@example.com
The binding of a dihydrogen molecule (H(2)) to a transition metal center in an organometallic complex was a major discovery because it changed the way chemists think about the reactivity of molecules with chemically "inert" strong bonds such as H H and C H. Before the seminal finding of side-on bonded H(2) in W(CO)(3)(PR(3))(2)(H(2)), it was generally believed that H(2) could not bind to another atom in stable fashion and would split into two separate H atoms to form a metal dihydride before undergoing chemical reaction. Metal-bound saturated molecules such as H(2), silanes, and alkanes (sigma-complexes) have a chemistry of their own, with surprisingly varied structures, bonding, and dynamics. H(2) complexes are of increased relevance for H(2) production and storage in the hydrogen economy of the future.
Service de prothèse fixe, Université de Liège, Institut de Dentisterie, policlinique L. Brull 45, Quai G. Kurth, 4020 Liège. firstname.lastname@example.org
Over the last years, current technologies in dental ceramics are strongly improved, constantly producing new materials for the restoration of the single or plural teeth. Feldspathic porcelains fused to a cast metal substructure, the so-called "metal-ceramic crown," has been long time the gold standard; this is primarily due to their predictable long-term strength characteristics. All-ceramic systems are a focus of interest, because they offer aesthetic results that may be difficult to achieve with metal-ceramic systems. Nowadays, the new ceramics associate aesthetic and good mechanical qualities, biocompatibility, accurate marginal fit and low invasive preparations. Thanks to the diversification of all-ceram processes, materials properties and clinical situations are now the prime criteria which determine the practitioner's choice. In this article, we try to summarize different clinical concepts for peripheric all-ceram restoration, such as crowns and bridges used in a daily dental practice.
Department of Chemistry, Malek-ashtar University of Technology, Shahin-shahr, P.O. Box 83145/115, Iran. mhkir@Yahoo.com
Two correlations are introduced for calculating Gurney velocity as a useful parameter for thermochemical estimation of explosive energy output. For CaHbNcOd explosives, only the chemical composition of high explosive as well as its condensed or estimated gas phase heat of formation, which later is calculated by group additivity rules, is needed for calculating Gurney velocity. The introduced simple correlations in the present work may be applied to any explosive that contains the elements of carbon, hydrogen, nitrogen and oxygen with no difficulties at any loading density. There is no need to use any assumed decomposition reaction in present work. Gurney velocity are calculated for different pure and explosive formulations and compared with measured Gurney velocity at specified loading density. The results show that the agreement is good for present method as compared to previous correlations.
Mimura Dental Clinic, Fujinomiya, Shizuoka, Japan.
The present study aimed at morphological and chemical characterization of the coating-substrate interface of a commercially available dental implant coated with plasma-sprayed hydroxyapatite (HA). For this purpose, elements in the chemically and mechanically exposed substrate surfaces were analyzed by EPMA and XPS. A thin titanium oxide film containing Ca and P was found at the interface. When the implant was subjected to mechanical stress, a mixed mode of cohesive and interfacial fractures occurred. The cohesive fracture was due to separation of the oxide film from the substrate, while the interfacial fracture was due to exfoliation of the coating from the oxide film bonded to the substrate. Analysis showed diffusion of Ca into the metal substrate, hence indicating the presence of chemical bond at the interface. However, mechanical interlocking seemed to play the major role in the interfacial bond.
Graduate School of Dentistry (Geriatric Dentistry), Osaka Dental University, 8-1 Kuzuhahanazono-cho, Hirakata-shi, Osaka 573-1121, Japan.
It is not known for certain that dental stone components influence titanium welding. In this study, we investigated metallurgical problems caused by laser welding on dental stones using wrought commercial pure (CP) titanium. A pulsed Nd:YAG laser irradiated a number of specimens' surfaces which were fixed on either a dental hard stone or a titanium plate. The metallurgical properties of the weld were evaluated using the Vickers hardness test, microstructure observation, fractured surface observation and quantitative analysis of oxygen and hydrogen. In the weld formed on the dental stone there was an increase in hardness, the existence of an acicular structure and a brittle fractured surface, and an increase in the oxygen and hydrogen concentrations compared with base metal. In the weld formed on the titanium plate, these changes were not observed. Therefore, it was demonstrated that laser welding on dental stones made the welds brittle.