Research Articles (Orthodontics)

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Browsing by Author "Grobler, Sias Renier"

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    Towards bioactive containing restorative materials: from design to testing in vitro approach
    (Symbiosis, 2015) Perchyonok, Tamara; Mulder, Riaan; Grobler, Sias Renier; Zhang, Shengmiao
    In any repair of a tooth with permanent restorative materials, the interface is always a sensitive region. The appearance of adhesive materials was a great step forward in dealing with the problems of this region and improving the overall performance of the restorations. However, contemporary adhesive materials do have a major disadvantage, namely that their durability is limited, a limitation which often arises due to their inadequate marginal adaptation. Restorative materials in the new era aim to be “bio-active” and long lasting. As part of our continuous interest in developing the novel bioactive containing restorative materials, we evaluated the effect of the additional bio-actives (such as chitosan, β-carotene, guar gum resin and the combination of the materials) to the commercially available flowable restorative materials such as Premise on the volumetric shrinkage, flexural strength, compressive strength, the surface hardness of the “bio-active” containing composite
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    Towards bioactive dental restorative materials with chitosan and nanodiamonds: evaluation and application
    (SciDoc Publishers, 2015) Mulder, Riaan; Grobler, Sias Renier; Moodley, Desi; Perchyonok, Tamara
    BACKGROUND/PURPOSES: Recently various articles showed beneficial effects of the addition of different the beneficial effect (bond strength and longevity) of the addition of different bioactive compounds towards dental materials. compounds towards dental materials. Therefore, the aim of this work was to evaluate the effect of the addition of bioactive materials and combination thereof (chitosan/nanodiamond or cyclodextrin/nanodiamond) to a dental composite. MATERIALS AND METHODS: The flowable composite Premise by Kerr was used as the standard control dental material. Premisewas also modified to contain: 10% nanodiamonds/Premise, 10% chitosan/nanodiamonds/Premise, 10% cyclodextrin/ nanodiamonds/Premise and 10% cyclodextrin/Premise and tested for their dentin bond strength, volumetric shrinkage, Vickers hardness and cytotoxicity. RESULTS AND CONCLUSION: Beneficial effects of the addition of different bioactive compounds towards dental materials were proved. A higher shear bond strength (p < 5%) was found after 3 months of Premise treated with nanodiamonds, chitosan, cyclodextrin (CD) and combinations thereof than the control Premise. The sequence for the Vickers hardness was: CD (32.5) < nano (34.8) < CD Nano (38.8) < Premise (39) < Chitosan Nano (42.2). Chitosan was found to increase the mouse 3T3 fibroblast cell survival rate (113%), while nanodiamonds (92%) and the combination of chitosan + nanodiamonds (93%) showed little cytotoxicity. The shrinkage was lower for all the additions than for Premise alone. Nanodiamonds and the combination chitosan + nanodiamonds showed little cytotoxicity towards mouse 3T3 fibroblast cells.
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    Volumetric change of flowable composite resins due to polymerization as measured with an electronic mercury dilatometer
    (Herbert Publications Ltd., 2013) Mulder, Riaan; Grobler, Sias Renier; Osman, Yusuf Ismail
    BACKGROUND: To determine the total volumetric change and the relative speed of shrinkage of bulk fill flowable composites during polymerization. MATERIALS AND METHODS: A specially designed electronic mercury dilatometer was used to determine the volumetric change. The light intensity was 500mW/cm2. The mercury dilatometer measured the volumetric change every 0.5 seconds during the 35 second irradiation exposure time. The materials tested were Z250 as standard and control. Four bulk fill flowable composites were tested. RESULTS: The sequence of total volumetric change was found to be: Z250 < Filtek bulk fill < Xtra-Base bulk fill < SDR < Venus bulk fill. The speed of shrinkage of the bulk fill flowables was faster than that of Z250, while the 2 flowables with the highest shrinkage speed (SDR and Venus) also had the highest total volumetric change. Of the different materials tested the volumetric change of Z250 (1.13%) was the lowest and significantly less (p<0.05) than that of SDR (1.55%) and Venus (1.72%). The material with the highest filler content (Z250) also showed the lowest shrinkage (1.13%) but this effect could not be seen in the flowables. In general, it was found that a 35 second irradiation period (with a light intensity of 500mW/cm2) was satisfactory for complete polymerization of the resins. CONCLUSIONS: The volumetric changes and speed of shrinkage were higher for all 4 bulk fill flowable composites than for Z250. SDR and Venus flowables had the fastest and highest volumetric shrinkage. Clinical significance: The manufacturers of bulk fill flowable composites advocate filling layers of 4mm. However, because of the high shrinkage values found in this study it should be suggested that the standard 2mm layer increments still be used.