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  • 1.
    Addi, Simon
    et al.
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Hedayati-Khams, Arjang
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Poya, Amin
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Sjögren, Göran
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Interface gap size of manually and CAD/CAM-manufactured ceramic inlays/onlays in vitro.2002Inngår i: Journal of Dentistry, ISSN 0300-5712, Vol. 30, nr 1, 53-58 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Objectives : To determine the fit of ceramic inlays manufactured using a recently introduced CAD/CAM-system (Decim) and of two types of laboratory-made heat-pressed ceramics (IPS Empress and Opc).

    Materials and methods : Extracted human premolars were prepared to receive mesio-occlusodistal (MOD) ceramic inlays, for which 10 Denzir, 10 IPS Empress, and 10 Opc were fabricated. The Denzir restorations were produced by the manufacturer of the CAD/CAM-system, and the IPS Empress and Opc by student dental technicians. Before luting the internal fit on the diestone models and on the premolars was determined using replicas. After luting on the premolars with a resin composite the marginal and internal fit were measured. The values were analyzed statistically using ANOVA and Scheffe's test at a significance level of p<0.05.

    Results : Before luting there were no significant differences ( p>0.05) in the internal gap width between the three systems studied when placed on their matching diestone models. When placed on the premolars a significant difference ( p<0.01) in the internal fit was seen between Empress and Opc before luting, whereas there were no significant differences ( p>0.05) between Empress and Denzir and between Opc and Denzir. Between the diestone models and the premolars there were significant differences ( p<0.01) in the internal fit, except for IPS Empress. After luting there were no significant differences ( p>0.05) between IPS Empress and Denzir, whereas the marginal gap width was significantly wider ( p<0.001) for Opc than for IPS Empress and Denzir. The internal fit was significantly ( p<0.001) wider for Opc than for IPS Empress, whereas there were no significant differences ( p>0.05) between IPS Empress and Denzir or between Opc and Denzir.

    Conclusion : After luting there were only slight differences in the fit between the restorations fabricated using the three different manufacturing techniques and ceramics. Therefore, long-term follow-up studies are needed to assess the clinical significance of the slight differences between the three systems.

  • 2.
    Ardlin, Berit
    et al.
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Lindholm-Sethson, Britta
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Effects of pH and Fluorides on Titanium2005Inngår i: Society for Biomaterials, 30th Annual Meeting & Exposition, Memphis,TN, USA: New Applications and Technologies, 2005Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Introduction: Titanium is used in dentistry both for crowns, fixed and removable partial dentures, suprastructures and for implants. In such applications, titanium may come in contact with fluorides. Prophylactic agents such as toothpastes and gels have effects on titanium that are dependent on their acidity and fluoride concentration. In order to obtain rapid bone growth and a strong bond between the implant and the bone, fluorides are used to modify the surfaces of titanium implants1. The aim of this investigation was to study the release of ions and the effects of fluorides on surfaces of titanium cp-II in saline solutions of different pF and pH using a) a brush test and b) electrochemical techniques including impedance spectroscopy2.

    Materials and Methods: Brush test. An electric toothbrush was used to brush the titanium electrodes for 2 min in aqua solutions of 0.9 % NaCl with 0, 0.3, 0.6 and 1 % NaF. The pH of the solutions was adjusted by adding ultra pure HNO3 and 1 M NaOH. In order to avoid interference with the chemical analyses, the solutions were not buffered. The solutions were divided into two all-embracing groups, pH 4.5 and pH>5.3, with respect to their acidity. An atomic absorption spectrophotometer equipped with a graphite atomizer with Zeeman effect background correction was used to detect titanium in the NaCl solutions.

    Electrochemical tests. Planar titanium electrodes with surface area of 0.28 cm2 served as working electrodes and were wet-ground with SiC paper through 1200 grit using standard metallographic procedures prior to exposure to the various electrolyte solutions. The solutions employed were similar to those used in the previous experiments, i.e. phosphate-buffered 0.9 % NaCl solutions with a pH between 4 and 7, containing 0, 0.3, 0.6 and 1 % NaF. An ordinary three-electrode setup was used with Ag/AgCl, sat KCl as a reference electrode and a platinum sheet as a counter electrode. The open circuit potential was recorded for 18–20 hours, and the electrode was then polarized to –0.18 V vs. ref. for five minutes. After this an impedance spectrum was recorded at –0.18 V vs. ref in the frequency range 100 000 Hz to 5 mHz and an amplitude of 10 mV peak to peak. Finally a linear anodic polarization curve was recorded from –0.5 V to 1 V vs ref at a sweep rate of 2 mV/sec.

    Results: The result of the brush tests is shown in Table 1. The highest amount of titanium was detected in the NaCl solutions with 0.6 or 1.0 % NaF at pH 4.5.

    Titanium remains passive in neutral solutions irrespective of the addition of fluoride and also at pH 4 without addition of fluoride. This is indicated in all three electrochemical experiments: the final electrode potential at open circuit is around -0.1 V vs ref after 18 hours, the impedance spectrum shows an almost pure capacitive behavior and the current at anodic polarization is very small. At low pH with addition of fluoride, titanium becomes active, as evidenced by a negative final electrode potential at open circuit of around -1.0 V vs ref after 18 hours, an impedance spectrum indicating a non-blocking electrode and a high current at anodic polarization. At medium pH and with an addition of fluoride the electrochemical experiments indicate the formation of a porous non-passivating surface film. In the latter case the final open circuit potential is around -0,5 V vs ref, the impedance spectra show a non-blocking electrode with a large charge-storing capacity and the current at anodic polarization is close to the values obtained for the active electrode at pH 4. The results of the electrochemical tests are summarized in Table 2

  • 3.
    Berglund, Anders
    et al.
    Umeå universitet, Medicinsk fakultet, Odontologi, Tandteknikerprogrammet.
    Hulterström, Anna Karin
    Umeå universitet, Medicinsk fakultet, Odontologi, Tandteknikerprogrammet.
    Gruffman, Ewa
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    van Dijken, Jan
    Umeå universitet, Medicinsk fakultet, Odontologi, Tandhygienistprogrammet.
    Dimensional change of a calcium aluminate cement for posterior restorations in aqueous and dry media.2006Inngår i: Dental Materials, ISSN 0109-5641, Vol. 22, nr 5, 470-476 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    OBJECTIVES: A calcium aluminate cement has recently been developed, with claims of being an alternative to dental amalgam and resin composites in posterior cavities. However, its' mechanical properties are not well evaluated and the aim of the study was therefore, to evaluate its' dimensional stability over time. METHODS: The dimensional changes of the cement, Doxadent, and two composite resins, Esthet-X and InTen-S, were tested during 360 d. The specimens were stored at 37+/-1 degrees C either in 100% air humidity (dry) or immersed in distilled water (wet), except for the first 24h when all specimens were stored at 100% air humidity and 37+/-1 degrees C. RESULTS: During the first 24h, Doxadent decreased in volume with 0.04%, while InTen-S and Esthet-X decreased with 1.60 and 1.75%, respectively. From d 1-360, the dry Doxadent specimens increased in volume with 2.0% and in weight with 5.5%, while the corresponding increase for the wet specimens were 4.1 and 6.3%, respectively. The volume of both composites increased 0.8% or less in dry and wet conditions, while the increase in weight for InTen-S was 1.2% for the wet specimens and 0.6% for the dry. The corresponding figures for Esthet-X were 0.7 and 0.2%. SIGNIFICANCE: Doxadent was less dimensionally stable than the composites tested. Doxadent increased 2 times more in volume immersed in water than in 100% air humidity, while the increase in weight was almost similar. The clinical implications of the results found in the present study are uncertain. A material that continues to absorb water during prolonged periods and continues to react is questionable for clinical use.

  • 4.
    Hedlund, Sven-Olof
    et al.
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Johansson, N Gunnar
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Sjögren, Göran
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    A retrospective study of pre-fabricated carbon fibre root canal posts.2003Inngår i: Journal of Oral Rehabilitation, ISSN 0305-182X, Vol. 30, nr 10, 1036-40 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although pre-fabricated carbon fibre posts have been used during the past decade clinical evaluations of the technique are still few. Using dental records and radiographs the clinical performance of 65 pre-fabricated carbon fibre posts (Composipost and Endopost) placed in 48 patients who regularly visited a general practice were evaluated in the present study. After an average time of 2.3 +/- 0.8 years (median 2.1 years, range 1-4.9 years) of clinical service the failure rate was 3%. Failure occurred in one tooth with a single crown restoration and in one tooth that was part of a cantilever fixed partial denture. Although the failure rate is lower than those mostly reported for metallic posts and cores more clinical studies are necessary to assess the suitability of pre-fabricated carbon fibre posts for routine use as an alternative to individually cast posts.

  • 5.
    Hedlund, Sven-Olof
    et al.
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Johansson, N Gunnar
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Sjögren, Göran
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Retention of prefabricated and individually cast root canal posts in vitro.2003Inngår i: British Dental Journal, ISSN 0007-0610, Vol. 195, nr 3, 155-158 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Objectives: The aim of the study was to evaluate the retention of prefabricated root canal posts made of a variety of materials that have recently been introduced into dentistry.

    Materials and methods: The posts studied were CosmoPost, Composipost carbon fibres, Composipost Æstheti-Plus, Composipost Light-Post, and Para Post Fiber White. The posts were luted in extracted human premolars and the cores were built up with the resin composites recommended by the manufactures. The retention of individually cast gold alloy posts luted with zinc-phosphate cement were used as reference. A universal testing machine was used to determine the retention of each cemented post. Data were compared using ANOVA supplemented with Fisher’s PLSD at a significance level of p < 0.05.

    Results: Only the CosmoPost system exhibited retention values that were significantly lower then for the conventionally cast gold alloy posts luted with zinc-phosphate cement. The force necessary to loosen the CosmoPost specimens was significantly less than that needed to loosen the Composipost Æstheti-Plus (p < 0.05) and the Composipost Light-Post systems (p < 0.001). The force necessary to loosen the Para Post Fiber White specimens was significantly less than for the Composipost Light-Post system (p < 0.01). Other combinations did not differ significantly (p > 0.05).

    Conclusions: When zirconium oxide ceramic posts are luted with resin composites the bonding between the ceramic and resin composite seems to be weak. Further studies are thus necessary to achieve improved retention of all-ceramic root canal posts.

  • 6.
    Håff, Anna
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Löf, Hanna
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Gunne, Johan
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Protetik.
    Sjögren, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    A retrospective evaluation of zirconia-fixed partial dentures in general practices: an up to 13-year study2015Inngår i: Dental Materials, ISSN 0109-5641, E-ISSN 1879-0097, Vol. 31, nr 2, 162-170 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Objectives: To evaluate zirconia-based fixed partial dentures (FPDs) after more than 8 years in clinical service.

    Methods: Patients treated between 2000 and 2004 with zirconia FPDs were identified from the records of a manufacturer of FPD substructures. Of the 45 patients who met the inclusion criteria 30 attended the appointment and 33 FPDs were evaluated using modified California Dental Association (CDA) criteria. In addition, plaque and the bleeding index were registered. Patient satisfaction with the restorations was evaluated using a 10-point visual analog scale (VAS).

    Results: All the FPDs were made using CAD/CAM and hot isostatic pressed yttria-tetragonal zirconia polycrystal (HIPed Y-TZP) ceramic (Denzir) and were placed within general practices. The mean observation period was 9.6 ± 1.6 years (range 3.0–13.1 years). The CDA rating was 90% satisfactory for the surface. Corresponding figures for anatomic form, color and margin integrity were 94%, 100% and 94%, respectively. Regarding surface three (9.7%) FPDs exhibited veneer chipping and were rated ‘not acceptable’. For margin integrity two (6.5%) were rated ‘not acceptable’ because of caries. For anatomic form two (6.1%) were rated ‘not acceptable’ due to two lost FPDs. No significant differences were seen between the FPDs and controls for plaque and bleeding. The Kaplan–Meier survival rate (still in clinical function) was 94%, the success rate (technical events accounted for) 91% and (biological events accounted for) 73%. Based on the VAS the mean value for patient satisfaction was 9.3 ± 1.2.

    Significance: Ninety-four percent of the FPDs were still in clinical function. HIPed Y-TZP could serve as an alternative for FPD treatments similar to those in the current study.

  • 7.
    Kou, Wen
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    On dental ceramics and their fracture: a laboratory and numerical study2010Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Background Surface treatments and irregularities in the surfaces may affect the fracture of ceramics. The effects of various treatments on the surface texture of different types of ceramic cores/substructures was therefore qualitatively, quantitatively and numerically evaluated. Since fractures in ceramics are not fully understood, the fracture behavior in dental ceramic core/substructures was also studied using both established laboratory methods and newly developed numerical methods.

    Methods The surfaces of dental ceramic cores/substructures were studied qualitatively by means of a fluorescence penetrant method and scanning electron microscopy, quantitatively evaluated using a profilometer and also numerical simulation. In order to study fracture in zirconia-based fixed partial denture (FPD) frameworks, fractographic analysis in combination with fracture tests and newly developed two-dimensional (2D) and three-dimensional (3D) numerical modeling methods were used. In the numerical modeling methods, the heterogeneity within the materials was described by means of the Weibull distribution law. The Mohr–Coulomb failure criterion with tensile strength cut-off was used to judge whether the material was in an elastic or failed state.

    Results Manual grinding/polishing could smooth the surfaces on some of the types of dental ceramic cores/substructures studied. Using the fluorescence penetrant method, no cracks/flaws apart from milling grooves could be seen on the surfaces of machined zirconia-based frameworks. Numerical simulations demonstrated that surface grooves affect the fracture of the ceramic bars and the deeper the groove, the sooner the bar fractured. In the laboratory tests the fracture mechanism in the FPD frameworks was identified as tensile failure and irregularities on the ceramic surfaces could act as fracture initiation sites. The numerical modeling codes allowed a better understanding of the fracture mechanism than the laboratory tests; the stress distribution and the fracture process could be reproduced using the mathematical methods of mechanics. Furthermore, a strong correlation was found between the numerical and the laboratory results.

    Conclusion Based on the findings in the current thesis, smooth surfaces in areas of concentrated tensile stress would be preferable regarding the survival of ceramic restorations, however, the surfaces of only some of the ceramic cores/substructures could be significantly affected by manual polishing. The newly developed 3D method clearly showed the stress distribution and the fracture process in ceramic FPD frameworks, step by step, and seems to be an appropriate tool for use in the prediction of the fracture process in ceramic FPD frameworks.

  • 8.
    Kou, Wen
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap. Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Kou, Shaoquan
    Department of Civil and Mining Engineering, Luleå University of Technology, Luleå, Sweden.
    Liu, Hongyuan
    Department of Civil and Mining Engineering, Luleå University of Technology, Luleå, Sweden.
    Sjögren, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Numerical modeling of the fracture process in a three-unit all-ceramic fixed partial denture2007Inngår i: Dental Materials, ISSN 0109-5641, E-ISSN 1879-0097, Vol. 23, nr 8, 1042-1049 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    OBJECTIVES: The main objectives were to examine the fracture mechanism and process of a ceramic fixed partial denture (FPD) framework under simulated mechanical loading using a recently developed numerical modeling code, the R-T(2D) code, and also to evaluate the suitability of R-T(2D) code as a tool for this purpose. METHODS: Using the recently developed R-T(2D) code the fracture mechanism and process of a 3U yttria-tetragonal zirconia polycrystal ceramic (Y-TZP) FPD framework was simulated under static loading. In addition, the fracture pattern obtained using the numerical simulation was compared with the fracture pattern obtained in a previous laboratory test. RESULTS: The result revealed that the framework fracture pattern obtained using the numerical simulation agreed with that observed in a previous laboratory test. Quasi-photoelastic stress fringe pattern and acoustic emission showed that the fracture mechanism was tensile failure and that the crack started at the lower boundary of the framework. The fracture process could be followed both in step-by-step and step-in-step. SIGNIFICANCE: Based on the findings in the current study, the R-T(2D) code seems suitable for use as a complement to other tests and clinical observations in studying stress distribution, fracture mechanism and fracture processes in ceramic FPD frameworks.

  • 9.
    Kou, Wen
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Li, Decong
    Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.
    Qiao, Jiyan
    Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.
    Chen, Li
    Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.
    Ding, Yansheng
    Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.
    Sjögren, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    A 3D numerical simulation of stress distribution and fracture process in a zirconia-based FPD framework2011Inngår i: Journal of Biomedical Materials Research. Part B - Applied biomaterials, ISSN 1552-4973, E-ISSN 1552-4981, Vol. 96B, nr 2, 376-385 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, a numerical approach to the fracture behavior in a three-unit zirconia-based fixed partial denture (FPD) framework was made under mechanical loading using a newly developed three-dimensional (3D) numerical modeling code. All the materials studied were treated heterogeneously and Weibull distribution law was applied to describe the heterogeneity. The Mohr-Coulomb failure criterion with tensile strength cut-off was utilized to judge whether the material was in an elastic or failed state. For validation, the fracture pattern obtained from the numerical modeling was compared with a laboratory test; they largely correlated with each other. Similar fracture initiation sites were detected both in the numerical simulation and in an earlier fractographic analysis. The numerical simulation applied in this study clearly described the stress distribution and fracture process of zirconia-based FPD frameworks, information that could not be gained from the laboratory tests alone. Thus, the newly developed 3D numerical modeling code seems to be an efficient tool for prediction of the fracture process in ceramic FPD frameworks.

  • 10.
    Kou, Wen
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Molin, Margareta
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Protetik.
    Sjögren, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Surface roughness of five different dental ceramic core materials after grinding and polishing2006Inngår i: Journal of Oral Rehabilitation, ISSN 0305-182X, E-ISSN 1365-2842, Vol. 33, nr 2, 117-124 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In clinical practice, core materials can be exposed after adjustments are made to previously-luted all-ceramic restorations. The purpose of this study was to evaluate the surface roughness of five different dental ceramic core materials after grinding and polishing. Five different ceramic core materials, Vita In-Ceram Alumina, Vita In-Ceram Zirconia, IPS Empress 2, Procera AllCeram, and Denzir were evaluated. Vita Mark II was used as a reference material. The surface roughness, Ra value (mum), was registered using a profilometer. The measurements were made before and after grinding with diamond rotary cutting instruments and after polishing with the Sof-Lex system. The surface of representative specimens was evaluated qualitatively using scanning electron microscopy (SEM). Results were statistically analysed using analysis of variance (anova) supplemented with Scheffe's and Bonferroni multiple-comparison tests. Before grinding, Procera AllCeram and Denzir had the smoothest surfaces, while IPS Empress 2 had the coarsest. After grinding, all materials except IPS Empress 2 became coarser. Polishing with Sof-Lex provided no significant (P > 0.05) differences between Denzir, Vita Mark II and IPS Empress 2 or between Procera AllCeram and In-Ceram Zirconia. There were no significant differences (P > 0.05) either between the ground and the polished Procera AllCeram or In-Ceram Alumina specimens. Polishing of Denzir, IPS Empress 2 and In-Ceram Zirconia made the surfaces smoother compared with the state after grinding, whereas the polishing effect on Procera AllCeram and In-Ceram Alumina was ineffective. The findings of the SEM evaluation were consistent with the profilometer readings.

  • 11.
    Kou, Wen
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Qiao, Jiyan
    Chinese Academy of Sciences, Beijing, China.
    Li, Decong
    Chinese Academy of Sciences, Beijing, China.
    Chen, Li
    Chinese Academy of Sciences, Beijing, China.
    Ding, Yansheng
    Chinese Academy of Sciences, Beijing, China.
    Sjögren, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    A 3-D numerical simulation of the fracture process in three-unit FPD frameworks2009Konferansepaper (Annet vitenskapelig)
  • 12.
    Kou, Wen
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap. Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Sjögren, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Fracture behaviour of zirconia FPDs substructures: fractographic analysis of zirconia2010Inngår i: Journal of Oral Rehabilitation, ISSN 0305-182X, E-ISSN 1365-2842, Vol. 37, nr 4, 292-299 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

     The purpose of this study was to evaluate the occurrence of superficial flaws after machining and to identify fracture initiation and propagation in three-unit heat-treated machined fixed partial dentures (FPDs) substructures made of hot isostatic pressed (HIPed) yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) after loaded to fracture. Four three-unit HIPed Y-TZP-based FPDs substructures were examined. To evaluate the occurrence of superficial flaws after machining, the surfaces were studied utilizing a fluorescent penetrant method. After static loading to fracture, characteristic fracture features on both mating halves of the fractured specimens were studied using a stereomicroscope and a scanning electron microscope. Grinding grooves were clearly visible on the surfaces of the machined FPDs substructures, but no other flaws could be seen with the fluorescent penetrant method. After loading to fracture, the characteristic fracture features of arrest lines, compression curl, fracture mirror, fracture origin, hackle and twist hackle were detected. These findings indicated that the decisive fracture was initiated at the gingival embrasure of the pontic in association with a grinding groove. Thus, in three-unit heat-treated machined HIPed Y-TZP FPDs substructures, with the shape studied in this study, the gingival embrasure of the pontic seems to be a weak area providing a location for tensile stresses when they are occlusally loaded. In this area, fracture initiation may be located to a grinding groove.

  • 13.
    Lindgren, Jon
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Smeds, Jens
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Sjögren, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Effect of Surface Treatments and Aging in Water on Bond Strength to Zirconia2008Inngår i: Operative dentistry, ISSN 0361-7734, Vol. 33, nr 6, 675-681 s.Artikkel i tidsskrift (Fagfellevurdert)
  • 14.
    Lindholm-Sethson, Britta
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Kemi.
    Ardlin, Berit
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Effects of pH and fluoride concentration on the corrosion of titanium2008Inngår i: Journal of Biomedical Materials Research Part A, ISSN 1549-3296, Vol. 86A, nr 1, 149-59 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this investigation was to confirm and summarize the corrosion behavior of titanium in saline solution at different pH and fluoride concentration, and to characterize the surface films and the stability of a passive and aged titanium surface using open circuit potential measurements, electrochemical impedance spectroscopy, and anodic polarization curves. The results from the electrochemical measurements were related to titanium released after 2-min brushing with saline solutions with different pH and fluoride concentration, that is, simulating tooth brushing with fluoride containing prophylactic substances. Titanium was analyzed using atomic adsorption spectrophotometry. The pH in the saline solution was varied between 4 and 7 with additions of sodium fluoride up to 1.0 wt %. The presence of fluoride in solution was unfavorable for the stability of titanium and led to corrosion and the release of titanium especially at low pH. The combination of low pH and presence of fluoride ions in solution destroyed a passive film on the titanium surface even after aging for 170 h in neutral saline solution. The results do not necessarily imply the occurrence of biological soft tissue related effects even if a physical contact between titanium and the surrounding milieu is prevalent. To provide a general understanding of electrochemical techniques in biomaterial research, much effort was put in the qualitative description of the results, with the intention to provide a broader understanding of especially the impedance method to other researchers. (c) 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007.

  • 15.
    Persson-Sjögren, Solveig
    et al.
    Umeå universitet, Medicinsk fakultet, Integrativ medicinsk biologi.
    Sjögren, Göran
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Effects of dental materials on insulin release from isolated islets of Langerhans2002Inngår i: Dental Materials, ISSN 0109-5641, Vol. 18, nr 1, 20-25 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Objectives: To investigate the possibility of using a whole organ model for evaluating the biological effects of dental restoration materials in vitro.

    Methods: The effect on insulin release of isolated Langerhans islets of a series of dental materials was examined. The islets were incubated for 1 h with extracts obtained from various dental materials and insulin was assayed radioimmunologically with crystalline mouse insulin. The results were analysed statistically using analysis of variance (ANOVA) and Scheffe's test at a significance level of p<0.05.

    Results: One dental ceramic, Vita VMK 95, significantly ( p<0.01) decreased the insulin release, whereas another dental ceramic, Empress ( p<0.01), a partly re-cast high-noble gold alloy ( p<0.001), a modified high-noble gold alloy ( p<0,05), and unalloyed copper ( p<0.001) significantly increased the release of insulin.

    Significance: The results demonstrate a new instance of examining the biological effects of dental restoration materials. The method provides information about the effect of different materials on organ level in vitro that can complement other in vitro tests.

  • 16.
    Persson-Sjögren, Solveig
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB).
    Sjögren, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Effects of glass ionomers and dental resin composites on viability of beta-cells and insulin release in isolated islets of Langerhans.2003Inngår i: Biomaterials, ISSN 0142-9612, E-ISSN 1878-5905, Vol. 24, nr 21, 3741-3746 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Information on the biocompatibility of glass ionomers and resin composites is sparse. To extend the scale of biological testing we evaluated the influence of those materials on insulin secretion at whole organ level in vitro. The effects on insulin secretion of three glass ionomers and two resin composites, aged for 1 week, were studied in isolated mouse islets of Langerhans at basal (5.5mM) and at stimulatory (11.1mM) D-glucose concentrations. In addition, viability of single mouse beta-cells was evaluated. The effect of glass ionomer specimens aged for 1 and 4 months on insulin secretion at 11.1mM D-glucose was also studied. None of the materials affected the viability of the beta-cells. At 5.5mM D-glucose none of the materials affected the insulin secretion. At 11.1mM D-glucose, the glass ionomers only decreased the secretion and glass ionomers aged for 1 month still decreased insulin release whereas after 4 months ageing only one of the glass ionomers affected the release. The result shows a dynamic effect on insulin release of the elements and/or compounds released from the specimens.

  • 17.
    Sjögren, G
    et al.
    Umeå universitet, Medicinsk fakultet, Odontologi, Odont materialvetenskap.
    Bergman, M
    Molin, M
    Umeå universitet, Medicinsk fakultet, Odontologi, Protetik.
    Bessing, C
    A clinical examination of ceramic (Cerec) inlays.1992Inngår i: Acta Odontologica Scandinavica, ISSN 0001-6357, Vol. 50, nr 3, 171-8 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two hundred and five Cerec ceramic inlays placed by 8 dentists in 72 patients were examined independently by 3 calibrated evaluators 12-24 months after insertion, using the criteria of the California Dental Association (CDA) and also certain periodontal variables. Proximal dental plaque and bleeding on probing were not seen more often on Cerec surfaces than on control homologous surfaces. Ten patients reported postoperative sensitivity after treatment with Cerec inlays. Excellent CDA ratings for Color and Surface were obtained in 57% and 26%, respectively, and for Anatomic Form and Margin Integrity in 55% and 83%, respectively. Obvious differences were seen among the participating dentists with regard to the clinical quality of Cerec inlays. At present, the long-term performance of the Cerec technique cannot be predicted.

  • 18.
    Sjögren, Göran
    et al.
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Hedlund, Sven-Olof
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Jonsson, Caroline
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Sandström, Anna
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    A 3-year follow-up study of preformed beta-quartz glass-ceramic insert restorations.2000Inngår i: Quintessence International, ISSN 0033-6572, Vol. 31, nr 1, 25-31 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    OBJECTIVE: The purpose of this study was to evaluate the clinical performance of preformed beta-quartz glass-ceramic insert restorations. METHODS AND MATERIALS: Nine Class I and 30 Class II beta-quartz glass-ceramic insert restorations were placed in 16 patients who were seen regularly by personnel at Umeå University Dental School. The California Dental Association criteria were used to evaluate the restorations at baseline, 6 months, and 1, 2, and 3 years after luting. The occurrence of postoperative sensitivity, the time taken to manufacture each restoration, and certain periodontal conditions were also evaluated. RESULTS: Sixty-nine percent of the restorations were rated satisfactory at the 3-year examination. During the follow-up period, 4 became loose and 7 were fractured or had flaking surfaces. Caries was registered in connection with 1 restoration. Excellent ratings were obtained for marginal integrity, anatomic form, surface, and color in 62%, 84%, 32%, and 44% of the restorations, respectively. There was no statistically significant difference in the occurrence of plaque and bleeding on probing in comparison with the controls. The mean overall time for placement was 38 minutes. The estimated survival rate (Kaplan-Meier) was 59% after 3.5 years. CONCLUSION: The quality of the beta-quartz glass-ceramic restorations in the present study was inferior to that presented in most earlier studies of ceramic or resin composite posterior restorations placed in patients treated at university clinics. Both the technique and the beta-quartz glass-ceramic inserts have to be evaluated in more long-term studies to assess the possibility of their serving as an alternative restorative technique.

  • 19.
    Sjögren, Göran
    et al.
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Lantto, Rolf
    Granberg, Åsa
    Sundström, Bengt-Olov
    Tillberg, Anders
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Clinical examination of leucite-reinforced glass-ceramic crowns (Empress) in general practice: a retrospective study1999Inngår i: International Journal of Prosthodontics, ISSN 0893-2174, Vol. 12, nr 2, 122-128 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    PURPOSE: The purpose of this study was to retrospectively evaluate leucite reinforced-glass ceramic crowns (Empress) placed in patients who regularly visit general practices. MATERIALS AND METHODS: One hundred ten Empress crowns, placed in 29 patients who visited a general practice on a regular basis, were evaluated according to the California Dental Association's (CDA) quality evaluation system. In addition, the occurrence of plaque and certain gingival conditions was evaluated. All crowns were luted with resin composite cement. The mean and median years in function for the crowns were 3.6 and 3.9 years, respectively. RESULTS: Based on the CDA criteria, 92% of the 110 crowns were rated "satisfactory." Eighty-six percent were given the CDA rating "excellent" for margin integrity. Fracture was registered in 6% of the 110 crowns. Of the remaining 103 crowns, the CDA rating excellent was given to 74% for anatomic form, 86% for color, and 90% for surface. No significant differences (P > 0.05) were observed regarding fracture rates between anterior and posterior crowns. With regard to the occurrence of plaque and bleeding on probing, no significant differences (P > 0.05) were observed between the Empress crowns and the controls. CONCLUSION: Most of the fractured crowns had been placed on molars or premolars. Although the difference between anterior and posterior teeth was not statistically significant with respect to the fracture rates obtained, the number of fractured crowns placed on posterior teeth exceeded that of those placed on anterior teeth. The difference between the fracture rates may have clinical significance, and the risk of fracture has to be taken into consideration when placing crowns on teeth that are likely to be subjected to high stress levels.

  • 20.
    Sjögren, Göran
    et al.
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Lantto, Rolf
    Tillberg, Anders
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Clinical evaluation of all-ceramic crowns (Dicor) in general practice.1999Inngår i: The Journal of prosthetic dentistry (Print), ISSN 0022-3913, Vol. 81, nr 3, 277-284 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    STATEMENT OF PROBLEM: There are few studies regarding all-ceramic full crowns placed by general practitioners; however, most dental restorations are carried out by general practitioners, and their clinical performance may be of particular interest. PURPOSE: Ninety-eight all-ceramic Dicor crowns placed in 46 patients regularly visiting a general practice were evaluated with the California Dental Association's (CDA) criteria. Mean and median ages of the crowns were 6.1 and 5.8 years, respectively (range 1.4 to 10. 9 years). Crowns were luted with either a glass ionomer, zinc phosphate, or resin composite cement. RESULTS. Of the 98 crowns, 82% were rated satisfactory. For marginal integrity, 51% were rated excellent. Fracture was registered in 14 all crowns, and 1 endodontically treated tooth with a Dicor crown was extracted because of root fracture; of the remaining 83 crowns, 55% were rated excellent for color. Corresponding figures for surface and anatomic form were 46% and 23%, respectively. The most common finding was slightly rough surfaces (64%). No statistically significant difference was observed for fracture rates obtained when the crowns luted with different luting agents were compared (P >.05). There was no more plaque or bleeding on probing (P >.05) in connection with the Dicor crowns than in the control surfaces.

  • 21.
    Sjögren, Göran
    et al.
    Umeå universitet, Medicinsk fakultet, Odontologi, Odont materialvetenskap.
    Molin, Margareta
    Umeå universitet, Medicinsk fakultet, Odontologi, Odont materialvetenskap.
    van Dijken, Jan
    Umeå universitet, Medicinsk fakultet, Odontologi, Odont materialvetenskap.
    A 10-year prospective evaluation of CAD/CAM-manufactured (Cerec) ceramic inlays cemented with a chemically cured or dual-cured resin composite2004Inngår i: International Journal of Prosthodontics, ISSN 0893-2174, Vol. 17, nr 2, 241-246 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    PURPOSE: The present follow-up study was carried out to evaluate the performance of Class II Cerec inlays after 10 years of clinical service. MATERIALS AND METHODS: Sixty-six Class II CAD/CAM ceramic inlays were placed in 27 patients. Each patient received at least one inlay luted with a dual-cured resin composite and one inlay luted with a chemically cured resin composite. At the 10-year recall, 25 (93%) patients with 61 (92%) inlays were available for evaluation using a slight modification of the USPHS criteria. RESULTS: Fifty-four (89%) of the 61 inlays reevaluated still functioned well at the 10-year recall. During the follow-up period, seven (11%) of the inlays required replacement because of: four inlay fractures, one cusp fracture, endodontic problems in one case, and postoperative symptoms in one case. All the replaced inlays had been luted with the dual-cured resin composite. The fractured inlays were all placed in molars. The estimated survival rate after 10 years was 89%, 77% for the dual-cured resin composite-luted inlays and 100% for the chemically cured resin composite-luted ones. The difference was statistically significant. CONCLUSION: Patient satisfaction with and acceptance of the Cerec inlays were high, and the performance after 10 years of clinical service was acceptable, especially regarding the inlays luted with the chemically cured resin composite. The properties of the luting agents seem to affect the longevity of the type of ceramic inlays evaluated.

  • 22.
    Sjögren, Göran
    et al.
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Sletten, Gaynour
    Scandinaivian Institute of Dental Materials, Haslum, Norway.
    Dahl, Jon E
    Scandinaivian Institute of Dental Materials, Haslum, Norway.
    Cytotoxicity of dental alloys, metals, and ceramics assessed by millipore filter, agar overlay, and MTT tests.2002Inngår i: The Journal of Prosthetic Dentistry, ISSN 0022-3913, Vol. 84, nr 2, 229-236 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Statement of Problem: Biocompatibility of dental materials is dependent on the release of elements from the materials. In addition, the composition, pretreatment, and handling of the materials influence the element release. Purpose: This study evaluated the cytotoxicity of dental alloys, metals, and ceramics, with specific emphasis on the effects of altering the composition and the pretreatment. Material and Methods: By using cells from a mouse fibroblast cell line and the agar overlay test, Millipore filter test, and MTT test, cytotoxicity of various metals, metal alloys, and ceramics for dental restoration were studied. Effects of altering the composition of a high noble gold alloy and of pretreatment of a ceramic-bonding alloy were also studied. In addition, the release of elements into the cell culture medium by the materials studied was measured using an inductively coupled plasma optical emission spectrophotometer. The results of the MTT test were analyzed statistically using ANOVA and Scheffé test at a significance level of P<.05. Results: Specimens manufactured from materials intended for dental restorations and handled in accordance with the manufacturers’ instructions were ranked from “noncytotoxic” to “mildly cytotoxic” according to the agar overlay and Millipore filter tests. For the MTT test, no significant differences were observed between these materials and controls, with the exception of JS C-gold and unalloyed titanium. The modified materials were ranked from “mildly cytotoxic” to “moderately cytotoxic” in the agar overlay and Millipore filter tests and from “noncytotoxic” to “moderately cytotoxic” in the MTT test. Thus, cytotoxicity was related to the alloy composition and treatment. The release of Cu and Zn seemed to be important for the cytotoxic effect. Conclusion: Alterations in the composition and the pretreatment can greatly influence the cytotoxicity, and the results stress the importance of carefully following the manufacturers’ instructions when handling dental materials.

  • 23.
    Sundh, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Zirconia as a biomaterial for odontological applications: effects of composition and manufacturing processes on fracture resistance2010Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Background: Ceramics have long been amongst the most biocompatible materials known but their mechanical properties have limited their use. During the past few decades zirconia has aroused particular interest as a biomaterial because of its greater flexural strength, fracture resistance and toughness compared to other bioceramics. Technological inventions and developments have made the processing of zirconia-based ceramics possible and thus also the successful processing of dental restorations constructed from this type of material. The properties of zirconia-based ceramics can, however, be affected by, for example, shape, composition, manufacturing processes and subsequent handling. It was, therefore, of particular interest to study in what way recently introduced zirconia-based ceramics intended for odontological applications could be affected by the shape, manufacturing process, composition, grinding and veneering.

    Methods: By means of newly invented and developed CAM-Software systems with improvements in grinding technology and strategy and hardware technology, cores for single crowns, fixed partial denture (FPD) frameworks and implant-supported abutments and copies were manufactured from a hot isostatic-pressed (HIPed) yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic. In addition, zirconia-based ceramics intended for odontological applications but made from other compositions and/or using different manufacturing techniques were studied. The effects were determined of shape, composition, manufacturing process, heat treatment and veneering of the cores/frameworks on the fracture or bending resistance of various types of ceramic single crowns, FPD frameworks and implant-supported abutments and copies.

    Results: Different thicknesses in different parts of HIPed Y-TZP cores improved the fracture resistance compared with cores of a uniform thickness resulting in a thicker veneer layer. Machining, heat treatment and veneering affected the fracture resistance of the zirconia-based ceramics studied. In addition, the quality of sintering and composition and type of veneering porcelain used influenced the fracture resistance of zirconia-based ceramics.

    Conclusion: The results obtained indicate that zirconia-based ceramics have the potential for use as a material in odontological applications. The mechanical properties of zirconia ceramics are, however, affected by, among other things, the shape, composition, manufacturing processes and subsequent handling of the material. These findings have to be taken in consideration in the production processes of zirconia-based ceramic restorations. To further improve their function more studies are needed to elucidate the effects of various manufacturing and handling techniques on the properties of zirconia-based ceramics.

  • 24.
    Sundh, Anders
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Molin, Margareta
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Protetik.
    Sjögren, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Fracture resistance of yttrium oxide partially-stabilized zirconia all-ceramic bridges after veneering and mechanical fatigue testing2005Inngår i: Dental Materials, ISSN 0109-5641, E-ISSN 1879-0097, Vol. 21, nr 5, 476-482 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    OBJECTIVES: Yttria-stabilized zirconia (Y-TZP) ceramic is a high-performance material with excellent mechanical properties suitable for fixed partial dentures. The purpose of this study was to evaluate after fatigue testing, the effect of heat-treatment and veneering on the fracture resistance of frameworks manufactured using sintered and subsequently hot isostatic pressed yttrium oxide partially-stabilized zirconia (Denzir).

    METHODS: The specimens were subjected to dynamic loading in water. Thereafter, using a universal testing machine, the fracture resistance of three-unit fixed partial dentures was determined; (i) of the frameworks as delivered after machining, (ii) after the frameworks had been subjected to heat-treatment similar to veneering with a glass-ceramic (Eris) or a feldspar-based ceramic (Vita D) and (iii) after the frameworks had been veneered with these ceramics. In addition, the fracture resistance of frameworks as delivered after machining not subjected to dynamic loading in water was determined.

    RESULTS: Cyclic loading in water did not significantly (p>0.05) affect the fracture resistance. The load necessary to fracture the frameworks as delivered after machining was significantly (p<0.001) higher than for the heat-treated and veneered specimens. No significant difference was seen between the specimens veneered with Eris and those veneered with Vita D (p>0.05). For all but three specimens the fractures were located in the loading point and through one of the connectors.

    SIGNIFICANCE: Heat-treatment and veneering reduce fracture resistance of hot isostatic pressed zirconia. Nevertheless, the results obtained indicate that it is an interesting material for potential in all-ceramic restorations.

  • 25.
    Sundh, Anders
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Sjögren, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    A comparison of fracture strength of yttrium-oxide-partially-stabilized zirconia ceramic crowns with varying core thickness, shapes and veneer ceramics2004Inngår i: Journal of Oral Rehabilitation, ISSN 0305-182X, E-ISSN 1365-2842, Vol. 31, nr 7, 682-688 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The fracture strengths of stylized all-ceramic crowns manufactured using an yttrium-oxide-partially-stabilized (Y-TZP) zirconia ceramic core (Denzir) veneered with lithium disilicate glass-ceramics (IPS Empress 2 or IPS Eris) were evaluated. The Denzir cores were manufactured in two ways: either with different thicknesses in different parts of the restoration, called an ‘adapted Denzir core’; or with a uniform core thickness of 0.5 mm. IPS Empress 2 all-ceramic crowns served as reference. There was no significant difference between the crowns with an ‘adapted Denzir core’ veneered with the two brands of glass-ceramics. No significant difference was seen between the crowns with a 0.5 mm Denzir core veneered with the two brands of glass-ceramics. The crowns with an ’adapted Denzir core’ exhibited significantly higher values than those with a 0.5 mm Denzir core and than the IPS Empress 2 crowns used as reference. No significant differences were seen among the IPS Empress 2 crowns used as reference and the crowns with a 0.5 mm Denzir core. The mode of failure varied among the Empress 2 crowns and the crowns with a core of a Y-TZP zirconia ceramic. Long-term studies are necessary to assess the clinical performance of this restorative system.

  • 26.
    Sundh, Anders
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Sjögren, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    A study of the bending resistance of implant-supported reinforced alumina and machined zirconia abutments and copies2008Inngår i: Dental Materials, ISSN 0109-5641, E-ISSN 1879-0097, Vol. 24, nr 5, 611-617 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    OBJECTIVES: The purpose of the present study was to evaluate the bending resistance of implant-supported CAD/CAM-processed restorations made out of zirconia or manually shaped made out of reinforced alumina.

    METHODS: Units of abutments and copies made of (i) a prefabricated hot isostatic pressed (HIPed) yttrium oxide partially-stabilized zirconia (Y-TZP) (Denzir), (ii) a prefabricated densely-sintered magnesia partially stabilized zirconia (Mg-PSZ) (Denzir-M) or, copies made of (iii) a prefabricated partially-sintered, porous reinforced alumina ceramic (RN synOcta-In-Ceram) were subjected to static loading perpendicularly at the long axis. The abutments were attached to either stainless steel analogs or titanium implant fixtures. The Y-TZP and Mg-PSZ copies were bonded onto the ceramic abutments with a dual-cured resin composite (Rely-X Unicem). Units of titanium abutment attached to a titanium implant fixtures were used as reference.

    RESULTS: The units comprising Denzir abutments as delivered (p<0.05) and heat-treated Denzir copies bonded to the Denzir abutments as delivered (p<0.01) and attached to stainless steel analogs exhibited significantly higher bending resistance than the control. The heat-treated Denzir copies bonded to the heat-treated Denzir M abutments attached to titanium implant fixtures and the In-Ceram specimens attached to stainless steel analogs showed significantly (p<0.05) lower bending resistance than the heat-treated Denzir copies bonded to the Denzir abutments as delivered and attached to stainless steel analogs. No statistically significant (p>0.05) differences were seen among the other groups studied.

    SIGNIFICANCE: All the ceramic abutments and copies exhibited values that were equal or superior to that of the control and exceeded the reported value, up to 300 N, for maximum incisal bite forces. To assess the clinical behavior long-term clinical studies should be conducted.

  • 27.
    Sundh, Anders
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Sjögren, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Fracture resistance of all-ceramic zirconia bridges with differing phase stabilizers and quality of sintering2006Inngår i: Dental Materials, ISSN 0109-5641, E-ISSN 1879-0097, Vol. 22, nr 8, 778-784 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    OBJECTIVES: The mechanical properties of zirconia ceramics are affected of stabilizing oxides and quality of sintering. The purpose of this study was to investigate the fracture resistance of frameworks manufactured using prefabricated zirconia blanks with differing stabilizing oxides and quality of sintering.

    METHODS: After dynamic loading in water, the fracture resistance was determined of stylized three-unit fixed partial dentures made of prefabricated homogenous ceramic green-body yttria-stabilized zirconia (Y-TZP) blanks (Vita YZ) or of densely-sintered magnesia partially stabilized zirconia (Mg-PSZ) blanks (Denzir-M); (i) as supplied from the manufacturer, (ii) after subjection to heat treatment in a way similar to veneering, and (Hi) after veneering with a feldspar-based ceramic.

    RESULTS: After veneering, the load at fracture of the Vita YZ specimens was significantly higher (p<0.05) than that of Denzir-M. The load necessary to fracture Denzir-M as supplied after machining was significantly (p<0.05) higher than that of heat-treated Denzir-M, Vita YZ as supplied and heat-treated Vita YZ specimens. There was no significant difference (p>0.05) between the heat-treated and veneered Denzir-M specimens. For Vita YZ the load at fracture of the veneered specimens was significantly (p<0.05) higher than of those as supplied or heat-treated, whereas no significant difference (p>0.05) was seen between heat-treated Vita YZ and Vita YZ specimens as supplied.

    SIGNIFICANCE: The fracture strength of the Vita YZ specimens increased considerably after veneering. Denzir-M and Vita YZ seem to be interesting alternatives for use as core materials in all-ceramic restorations. Long-term studies are, however, necessary before general clinical recommendations can be issued.

  • 28.
    Tillberg, Anders
    et al.
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Järvholm, Bengt
    Umeå universitet, Medicinsk fakultet, Folkhälsa och klinisk medicin, Yrkes- och miljömedicin.
    Berglund, Anders
    Umeå universitet, Medicinsk fakultet, Odontologi, Tandteknikerprogrammet.
    Risks with dental materials2008Inngår i: Dental Materials, ISSN 0109-5641, Vol. 24, nr 7, 940-943 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    OBJECTIVES: Dental materials are among the most used substitutes for biological tissue in the human body. The possible health effects of amalgam have been studied extensively and have sometimes been replaced with other less well-examined materials. The aim was to study the hazards of other dental materials than amalgam. METHODS: Toxicological information was collected from the Swedish Dental Materials Register 2003 (DentMr). The material safety data sheets (MSDS) included in the DentMR was examined regarding the given composition of the products, the occurrence of CAS-numbers and risk and safety phrases of the substances. Furthermore, complementary information about risk and safety phrases for substances with missing information in the MSDS was collected by using two easily available databases. RESULTS: There were 482 products that included 377 substances of which 219 could be identified. Only 26% of 219 substances had risk and safety phrases. However, via the Swedish Chemicals Inspectorate Classification Register and the Sigma-Aldrich product register, risk and safety phrases could be found for 37 substances. A literature search indicated that some of the listed substances had possible hazards, e.g. substances with embryotoxic and neurotoxic potential. SIGNIFICANCE: The information about hazards with dental materials seems insufficiently described in MSDS and there might be materials with side effects unknown to both patients and dental personnel. There is a need for stronger regulation of dental materials, at least substances that the patients will be exposed to for decades.

  • 29.
    Uo, Motohiro
    et al.
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Sjögren, Göran
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Sundh, Anders
    Goto, Mitsunari
    Watari, Fumio
    Bergman, Maud
    Effect of surface condition of dental zirconia ceramic (Denzir) on bonding2006Inngår i: Dental materials journal, ISSN 0287-4547, Vol. 25, nr 3, 626-631 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Yttria partially stabilized zirconia (YPSZ) ceramics are suitable for dental and medical use because of their high fracture toughness and chemical durability. The purpose of this study was to examine the bonding behavior of a dental YPSZ ceramic, Denzir. After being subjected to various surface treatments, Denzir specimens were bonded to each other using an adhesive resin composite, glass ionomer, or zinc phosphate cement. Bonding strength was then determined by the shearing test. No significant differences (p>0.05) were observed between SiC- and Al2O3-blasted specimens. In all surface treatments, the shear bond strength significantly (p<0.05) increased in the order of adhesive resin composite cement > glass ionomer cement > zinc phosphate cement. Moreover, silanization with methacryloxy propyl trimethoxysilane slightly increased the bonding strength of the adhesive resin composite cement.

  • 30.
    Uo, Motohiro
    et al.
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Sjögren, Göran
    Umeå universitet, Medicinsk fakultet, Odontologi, Odontologisk materialvetenskap.
    Sundh, Anders
    Watari, Fumio
    Bergman, Maud
    Lerner, Ulf
    Umeå universitet, Medicinsk fakultet, Odontologi, Oral cellbiologi.
    Cytotoxicity and bonding property of dental ceramics.2003Inngår i: Dental Materials, ISSN 0109-5641, Vol. 19, nr 6, 487-92 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Objectives . Yttria partially stabilized zirconia (YPSZ) ceramic is suitable for dental and medical use because of its high fracture toughness and chemical durability. The purpose of this study was to estimate the cytotoxicity and bonding property of zirconia ceramic compared to other dental ceramics.

    Methods . Eight commercial dental ceramics including Denzir (YPSZ) are used in this cytotoxicity test. The human gingival fibroblast (GF) cells were cultured using extraction solutions of ceramics. The cytotoxicity was estimated by two different methods. The bonding strength of Denzir was compared to Empress2 using zinc phosphate, glass ionomer, and adhesive resin cements. A brass plate was prepared with drilled tapered holes and ceramic specimens were prepared to fit the holes and bonded. The bonding strength was estimated by the punching test.

    Results . No significant ( p>0.05) cytotoxicity was observed in all ceramic extractions. The two evaluation methods showed no significant differences. Denzir and Empress2 showed similar bonding strength with zinc phosphate or glass ionomer cement bonding. For both Empress2 and Denzir the glass ionomer cement showed significantly ( p<0.001) higher bonding strength compared to the zinc phosphate cement. Empress2 showed significantly higher bonding strength with adhesive resin cement. However, the Denzir showed lower bonding strength with adhesive resin cement.

    Significance . No ceramic extractions showed any evidence of cytotoxicity. Therefore, the low in vitro cytotoxicity of ceramic extractions including Denzir was confirmed. Denzir showed a similar bonding strength to Empress2 with zinc phosphate or glass ionomer cement bonding with this testing method and lower bonding strength with adhesive resin cement than with Empress2.

  • 31.
    Åkesson, Joacim
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Sundh, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Sjögren, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Odontologisk materialvetenskap.
    Fracture resistance of all-ceramic crowns placed on apreparation with a slice-formed finishing line: Fracture resistance of all-ceramic crowns2009Inngår i: Journal of Oral Rehabilitation, ISSN 0305-182X, E-ISSN 1365-2842, ISSN 0305-182X, Vol. 36, nr 7, 516-523 s.Artikkel i tidsskrift (Fagfellevurdert)
1 - 31 of 31
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