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  • 1.
    Emami, Nazanin
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Söderholm, Karl-Johan
    Florida University.
    Cure kinetic behavior of light-cure dental composites2003In: Journal of Dental Research, ISSN 0022-0345, E-ISSN 1544-0591, Journal of Dental Research. Meeting abstracts: , no Suppl.Article in journal (Other academic)
    Abstract [en]

    Objective: To investigate differences in cure kinetic behaviours of different photo and co-initiator systems used in dental light-cure composites. Method: A resin system (50 wt.% of bisGMA and 50 wt.% of TEGDMA) was mixed with either campherquinone (CQ) or 1-phenyl-1,2-propanedione (PPD) as photo-initiator. N,N-dimethyl-p-aminobenzoic acid ethylester (DABE), N,N-cyanoethylmethylaniline (CEMA), N,N-diethanol-p-toluidine (DEPT) and 2-dimethylaminoethyl methacrylate (DMAEMA) were used as co-initiators respectively. Complex cure behaviour of 24 experimental mixtures made from 2 photoinitiators, 4 co-initiators, 3 curing light/time was studied with differential Scanning Calorimetery (DSC). Six specimens of each composition were cured either with 800 mW/cm2 for 40 s, soft start curing for 60 s or LED for 40 s. The DSC results were analysed using ANOVA and Duncan's multiple range test and regular t-test. Result: Rate of polymerisation was significantly (p<0.05) higher when materials were cured with 800 mW/cm2 compare to soft start and LED curing methods when the final degree of conversion values did not differ significantly (p>0.05). Compared to campherquinone, the photo-initiator PPD reduced the maximal DC% and rate of the polymerisation significantly (p<0.05). PPD was not a suitable photo-initiator when cured with LED since the blue spectra emitting from the used LED lamp does not cover the optimal activation wavelength for PPD properly. The highest DC% measured at the end of curing was for CQ & DABE 74%±1 cured with 800 mw/cm2 for 40s and the lowest was for PPD&DMAEMA 22%±1.1 when material was cured with LED for 40s. Use of DEPT resulted in significant decreases in degree of conversion (p<0.05). Conclusion: It was concluded that intrinsic slow cure might be obtained with certain compositions of photo & co-initiators and curing methods without impairing the final extent of degree polymerzation.

  • 2.
    Emami, Nazanin
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Söderholm, Karl-Johan
    Florida University.
    Berglund, Lars
    Kungliga tekniska högskolan, KTH.
    Effect of light intensities variations on bulk curing of dental composites2002In: Journal of Dental Research, ISSN 0022-0345, E-ISSN 1544-0591, Vol. 81, no Suppl. 1Article in journal (Refereed)
    Abstract [en]

    The light intensity used during curing of light curable dental composites is believed to affect the residual stress level. In this study we tested the hypothesis that low light intensity and long but clinically acceptable light curing time, can produce composites with physical/clinical properties (e.g. volumetric shrinkage, linear contraction stress, degree of conversion (DC%) and Young's modulus) comparable to those of high light intensity cured composites. Methods: Two dental composites, Z100 and Z250, were investigated. Specimens were cured with light intensities of 200, 450 and 800 mW/cm2 for 140, 60 and 35 s from a distance of 7 mm. Linear contraction strains were measured with strain-gages attached to stainless steel rings serving as molds (8 mm in diameter and 4 mm high). DC% was measured at the top and the bottom of samples as well through the bulk using FTIR. Volumetric polymerization shrinkage was determined using a water displacement method. Young's modulus was determined in tension on composite specimens with dimensions of 8 x 50 x 1 mm. Results: Polymerization stress level decreased significantly (p<0.05) when cured with 200 mW/cm2 rather than with 800 mW/cm2. Reduction in light intensity did not decrease the DC% values significantly, nevertheless the most dramatic differences existed between top and bottom surfaces (p<0.05) rather than among curing groups. Measured modulus and volumetric shrinkage values were no significantly different (p>0.05) between different light intensity groups. Conclusion: Low light intensity decreased the residual stress and DC% values (through the depth of cure) significantly (p<0.05), but did not significantly affect the Young's modulus and the volumetric shrinkage values. The lower residual stress values, reflected by lower strain levels in the metal rings used during measurement, suggest that more stress relaxation occurs in the low light intensity group during cure. Our results support the proposed hypothesis

  • 3.
    Emami, Nazanin
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Söderholm, Karl-Johan
    Florida University.
    Berglund, Lars
    Kungliga tekniska högskolan, KTH.
    Effect of light-intensity variations on bulk curing of dental composites2002In: Journal of Dental Research, ISSN 0022-0345, E-ISSN 1544-0591, Vol. 81, no Suppl 1Article in journal (Other academic)
  • 4.
    Emami, Nazanin
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Söderholm, Karl-Johan
    Florida University.
    Berglund, Lars
    How light-intensity and cure-time affect monomer conversion in light-cured composites2002In: Journal of Dental Research, ISSN 0022-0345, E-ISSN 1544-0591, Vol. 81, no Suppl 1Article in journal (Refereed)
1 - 4 of 4
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