Nordic Institute of Dental Materials

Oslo, Norway

Nordic Institute of Dental Materials

Oslo, Norway

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Ahlfors E.E.,University of Oslo | Ahlfors E.E.,Nordic Institute of Dental Materials | Dahl J.E.,Nordic Institute of Dental Materials | Lyberg T.,University of Oslo
Archives of Oral Biology | Year: 2012

The effect of a single time exposure of SLS to the buccal mucosa of mice was compared to one application of the hapten OXA (oxazolone), evaluated by routine histology, immunohistochemistry and ELISA quantifications of cytokines. The SLS concentrations (2%, 4% and 8%) resulted in epithelial surface necrosis at 1-6 h, after 2-6 h accumulation of intra-epithelial neutrophils and at 24 h the main inflammatory cells were mononuclear. Increased concentrations of SLS gave more severe damage. CD4 + T cells were found at 6 h and increased slightly up to 24 h and were most frequently seen at the lowest SLS dose. The CD8 + T cells were kept at a low number during the whole 24 h observation period, but increased proportionally to the CD4 + T cells. One application of 1% OXA did not raise the number of cells of either phenotype (2-24 h). Neither IL-2 nor IFN-γ demonstrated increased levels during the week of observation at any concentration of SLS, contrary to one application of OXA which caused increased IL-2 levels both at the local application site and in the regional and distant lymph nodes. Regardless of SLS concentration, a minor increase in regional lymph node weight was observed 8-12 h after substance application, quickly to subside whilst one OXA application gave a maximal weight increase at 48-72 h. We conclude that oral mucosa irritant SLS reactions gave early surface necrosis and neutrophil infiltrations and later mononuclear cell infiltrations dominated by CD4 + T cells. The cytokines IL-2 and IFN-γ and lymphocyte proliferation in the regional lymph nodes was not observed after SLS application, contrary to hapten application.


Wikene K.O.,University of Oslo | Rukke H.V.,Nordic Institute of Dental Materials | Bruzell E.,Nordic Institute of Dental Materials | Tonnesen H.H.,University of Oslo
European Journal of Pharmaceutics and Biopharmaceutics | Year: 2016

Natural deep eutectic solvents (NADES) are a newly discovered group of eutectics which has shown promise as a solvent in antimicrobial photodynamic therapy (aPDT). The purpose of this study was to investigate preparations of an anionic porphyrin, meso-tetra-(4-carboxyphenyl)-porphine (TCPP), solubilised in NADES, with regard to their physicochemical and antibacterial properties. The NADES CS (pH ∼ 0), ChX (pH ∼ 4) and MFG (pH ∼ 1) solubilised TCPP with absorption maximum ∼443 nm and emission maximum ∼678 nm, indicating formation of the TCPP dication. Dilution of TCPP-NADES > 1:1 (water) reduced the physical stability of the preparations. The photostability half-lives of TCPP in methanol, MFG, and CS were ∼9 h, 6.9 h and 3.2 h, respectively. Nanomolar concentrations of TCPP solubilised in diluted MFG combined with ≤27 J/cm2 blue light increased Gram-positive and Gram-negative bacterial phototoxicity, >99.98% and 96% bacterial reduction, respectively, compared to TCPP in PBS/ethanol under equivalent treatment conditions. TCPP solubilised in diluted CS was toxic to bacteria both in the absence (36-72% reduction) and presence of light. TCPP in CS, and in the CS component citric acid, induced a TCPP-concentration dependent increase in Gram-negative phototoxicity relative to controls, which was most pronounced for TCPP-CS. The mechanism behind the increased toxicity is unknown. © 2016 Elsevier B.V. All rights reserved.


PubMed | Nordic Institute of Dental Materials and University of Oslo
Type: | Journal: European journal of pharmaceutics and biopharmaceutics : official journal of Arbeitsgemeinschaft fur Pharmazeutische Verfahrenstechnik e.V | Year: 2016

Natural deep eutectic solvents (NADES) are a newly discovered group of eutectics which has shown promise as a solvent in antimicrobial photodynamic therapy (aPDT). The purpose of this study was to investigate preparations of an anionic porphyrin, meso-tetra-(4-carboxyphenyl)-porphine (TCPP), solubilised in NADES, with regard to their physicochemical and antibacterial properties. The NADES CS (pH0), ChX (pH4) and MFG (pH1) solubilised TCPP with absorption maximum 443nm and emission maximum 678nm, indicating formation of the TCPP dication. Dilution of TCPP-NADES>1:1 (water) reduced the physical stability of the preparations. The photostability half-lives of TCPP in methanol, MFG, and CS were 9h, 6.9h and 3.2h, respectively. Nanomolar concentrations of TCPP solubilised in diluted MFG combined with 27J/cm(2) blue light increased Gram-positive and Gram-negative bacterial phototoxicity, >99.98% and 96% bacterial reduction, respectively, compared to TCPP in PBS/ethanol under equivalent treatment conditions. TCPP solubilised in diluted CS was toxic to bacteria both in the absence (36-72% reduction) and presence of light. TCPP in CS, and in the CS component citric acid, induced a TCPP-concentration dependent increase in Gram-negative phototoxicity relative to controls, which was most pronounced for TCPP-CS. The mechanism behind the increased toxicity is unknown.


Cornelio R.B.,University of Tromsø | Wikant A.,University of Tromsø | Mjosund H.,University of Tromsø | Kopperud H.M.,Nordic Institute of Dental Materials | And 3 more authors.
Acta Odontologica Scandinavica | Year: 2014

Objective. The aim of this work was to assess the influence of the bis-EMA content on the degree of conversion (DC) and its effect on the water sorption and solubility. Materials and methods. In a polytetrafluorethylene (PTFE) mould, 30 samples (O = 5 mm, height = 2 mm) of four experimental dental composite resins were cured for 10 s, 20 s and 40 s. The DC was analysed by Fourier Transform (FT)-Raman spectroscopy. To analyse sorption and solubility, six samples (O = 15 mm and thickness = 1 mm) of each composite (n = 72) were stored in water at 37°C for different storage periods: 24 h, 7 days and 30 days. Results. When cured for 20 or 40 s the DC increased with the increasing content of bis-EMA. However, the presence of 15 wt% of bis-GMA did not affect the DC, except when cured with 10 s irradiation time. This study also found a correlation between the content of bis-EMA and the reduced values for sorption and solubility, for all storage times used, when the materials were cured with 20 s. Conclusions. The DC of mixtures with higher content of bis-EMA is affected by the presence of bis-GMA at lower energy density delivered from the curing device, suggesting that the restrictions caused by the presence of hydrogen bonds is dependent of the irradiation time used. © 2014 Informa Healthcare.


Samuelsen J.T.,Nordic Institute of Dental Materials | Kopperud H.M.,Nordic Institute of Dental Materials | Holme J.A.,Norwegian Institute of Public Health | Dragland I.S.,Nordic Institute of Dental Materials | And 2 more authors.
Journal of Biomedical Materials Research - Part A | Year: 2011

Methacrylate monomers that are found to leach from cured resin-based dental materials induce biological effects in vitro. The underlying mechanisms have not been fully elucidated although involvement of increased cellular reactive oxygen species (ROS) and DNA-damage has been suggested. In this in vitro study we have elucidated the impact of a commonly used methacrylate monomer, HEMA, on the level and oxidation state of cellular glutathione, intracellular ROS level, as well as the formation of complex between HEMA and glutathione. HEMA exposure rapidly led to increased level of ROS and reduced level of GSH (reduced form of glutathione). Antioxidants effectively counteracted the ROS increase, but had no effect on the GSH depletion. No change in glutathione-disulphide (GSSG; oxidized form of glutathione) concentration was detected in the HEMA treated cells, showing that oxidation of glutathione was not responsible for the reduced GSH concentration. Further we demonstrated spontaneous formation of a complex between HEMA and GSH. In conclusion, we showed that exposure to HEMA led to drop in cellular glutathione level probably caused by complex formation with HEMA. A similar covalent binding of HEMA to macromolecules combined with increased level of cellular ROS due to lower levels of GSH is suggested to be important factors triggering the toxic response. © 2010 Wiley Periodicals, Inc.


Price R.B.T.,Dalhousie University | Labrie D.,Dalhousie University | Bruzell E.M.,Nordic Institute of Dental Materials | Sliney D.H.,Fallston | Strassler H.E.,University of Maryland, Baltimore
Journal of Occupational and Environmental Hygiene | Year: 2016

Powerful blue-light emitting dental curing lights are used in dental offices to photocure resins in the mouth. In addition, many dental personnel use magnification loupes. This study measured the effect of magnification loupes on the “blue light hazard” when the light from a dental curing light was reflected off a human tooth. Loupes with 3.5x magnification (Design for Vision, Carl Zeiss, and Quality Aspirator) and 2.5x magnification (Design for Vision and Quality Aspirator) were placed at the entrance of an integrating sphere connected to a spectrometer (USB 4000, Ocean Optics). A model with human teeth was placed 40 cm away and in line with this sphere. The light guide tip of a broad-spectrum Sapphire Plus (Den-Mat) curing light was positioned at a 45° angle from the facial surface of the central incisor. The spectral radiant power reflected from the teeth was recorded five times with the loupes over the entrance into the sphere. The maximum permissible cumulative exposure times in an 8-hr day were calculated using guidelines set by the ACGIH. It was concluded that at a 40 cm distance, the maximum permissible cumulative daily exposure time to light reflected from the tooth was approximately 11 min without loupes. The weighted blue irradiance values were significantly different for each brand of loupe (Fisher's PLSD p < 0.05) and were up to eight times greater at the pupil than when loupes were not used. However, since the linear dimensions of the resulting images would be 2.5 to 3.5x larger on the retina, the image area was increased by the square of the magnification and the effective blue light hazard was reduced compared to without the loupes. Thus, although using magnification loupes increased the irradiance received at the pupil, the maximum cumulative daily exposure time to reflected light was increased up to 28 min. Further studies are required to determine the ocular hazards of a focused stare when using magnification loupes and the effects of other curing lights used in the dental office. © 2016 JOEH, LLC.


van Tol A.F.,University of Bergen | Tibballs J.E.,Nordic Institute of Dental Materials | Roar Gjerdet N.,University of Bergen | Ellison P.,University of Bergen
Journal of the Mechanical Behavior of Biomedical Materials | Year: 2013

Debonding of cemented bone implants is regarded as a major contributor to complications. The relationship between shear bond strength and surface roughness has been investigated, however there are inconsistencies in the trends reported in different studies. The shear strength between poly(methyl methacrylate) bone-cement and sand blasted cobalt-chromium and titanium alloy surfaces was measured to investigate the relationship between interfacial shear strength and surface topology. Surface roughness was quantified by a power law relationship fitted to Fourier spectra as well as three traditional parameters (arithmetical average roughness (Ra), volume of interdigitation (Rr), and RMS slope (Rdq). We found that the interfacial shear strength is directly proportional to the exponent of the surfaces power spectra (P2) and Rdq, but not to Ra and Rr. However, Rdq is shown to be critically dependent on sampling frequency, making it sensitive to measurement settings. P2 was found to be a robust measure of the surface roughness being independent of sampling frequency. © 2013 Elsevier Ltd.


Oilo M.,University of Bergen | Oilo M.,Nordic Institute of Dental Materials | Kvam K.,Nordic Institute of Dental Materials | Tibballs J.E.,Nordic Institute of Dental Materials | And 2 more authors.
Dental Materials | Year: 2013

Objectives Fracture strength measured in vitro indicates that most all-ceramic crowns should be able to withstand mastication forces. Nevertheless, fractures are one of the major clinical problems with all-ceramic restorations. Furthermore, the fracture mode of all-ceramic crowns observed in clinical use differs from that found in conventional fracture strength tests. The aim of the present study was to develop and investigate a method that simulates clinical fracture behavior in vitro. Methods 30 crowns with alumina cores were made to fit a cylindrical model with a molar-like preparation design. These crowns were randomly allocated to 3 tests groups (n = 10). The crowns in group 1 were cemented to abutment models of epoxy and subsequently fractured by occlusal loading without contact damage. The crowns in group 2 were fractured by cementation with expanding cement. The crowns in group 3 were cemented on an abutment model of epoxy split almost in two and fractured by increasing the diameter of the model in the bucco-lingual direction. The fractured crowns were analyzed by fractographic methods and compared to a reference group of 10 crowns fractured in clinical use. Results The fracture modes of all the in vitro crowns were similar to clinical fracture modes. The fracture modes in group 1 were most closely matched to the clinical fractures. These crowns also fractured at clinically relevant loads. Conclusion Laboratory tests that induce a distortion of the abutment model during occlusal loading without occlusal contact damage can simulate clinical fractures of all-ceramic crowns. © 2013 Academy of Dental Materials.


Ansteinsson V.,University of Bergen | Ansteinsson V.,Nordic Institute of Dental Materials | Solhaug A.,Norwegian Institute of Food | Samuelsen J.T.,Nordic Institute of Dental Materials | And 2 more authors.
Mutation Research - Genetic Toxicology and Environmental Mutagenesis | Year: 2011

The methacrylate monomer 2-hydroxyethyl methacrylate (HEMA) is commonly used in resin-based dental restorative materials. These materials are cured in situ and HEMA and other monomers have been identified in ambient air during dental surgery. In vitro studies have demonstrated a toxic potential of methacrylates, and concerns have been raised regarding possible health effects due to inhalation. In this study we have investigated the mechanisms of HEMA-induced toxicity in the human lung epithelial cell line BEAS-2B. Depletion of cellular glutathione (GSH) and an increased level of reactive oxygen species (ROS) were seen after 2. h of exposure, but the levels were restored to control levels after 12. h. After 24. h, inhibited cell proliferation and apoptotic cell death were found. The results of the Comet assay and the observed phosphorylation of DNA-damage-associated signalling proteins including Chk2, H2AX, and p53 suggest that the toxicity of HEMA is mediated by DNA damage. Further, the antioxidant trolox did not counteract the HEMA-induced cell-cycle arrest, which indicates that the DNA damage is of non-oxidative origin. © 2011 Elsevier B.V.


PubMed | Nordic Institute of Dental Materials and University of Bergen
Type: Journal Article | Journal: The Journal of prosthetic dentistry | Year: 2016

The effect of anatomic contour design in all or parts of zirconia crowns is uncertain regarding clinical reliability and survival rates.The purpose of this invitro study was to compare the load at fracture of monolithic, anatomic contour zirconia crowns with bilayered crowns with and without a cervical zirconia collar.Thirty zirconia crowns were fabricated for a shallow chamfer molar preparation, 10 with a normal core-veneer design, 10 with a core-veneer design with an additional cervical collar of zirconia, and 10 with a monolithic, anatomic contour design. Veneering ceramic was applied to the first 20 specimens to create an anatomic form. All crowns were cemented to epoxy abutments and loaded until complete fracture with a clinically relevant test method. The fracture modes and load at fracture were recorded.Statistically significant differences were found in the load at fracture and fracture modes among the test groups (P<.001). All fractures except one initiated in the crown margin, mostly in the proximal region. The mean load at fracture was 4091 N for the normal core-veneer design, 4712 N for the collar design, and 6517 N for the monolithic, anatomic contour design.Monolithic, anatomical contour design gave higher loads at fracture than traditional core-veneer design. Crowns with a cervical zirconia collar had higher load at fracture than the core-veneer design, but lower than the monolithic crowns.

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