Browsing by Subject "Resins"

Now showing 1 - 3 of 3
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    Comparison of Tensile Bond Strengths of Glass Ionomer Cements Using Hydroxyapatite Coated and Uncoated Orthodontic Brackets
    (1993) Ng, Richard I. Cheng Hin; Hohlt, William F.; Moore, B. Keith; Oshida, Yoshiki; Garetto, Lawrence P.; Roberts, W. Eugene; Shanks, James C.
    The use of glass ionomer cements (GIC) in orthodontics as a bonding agent has been receiving considerable attention due to its favorable properties, ie., physico-chemical adhesion to enamel, fluoride leaching capabilities and less traumatic bonding procedure to tooth structure. GIC ability to bond to the hydroxyapatite (HA) in the tooth enamel was tested utilizing an HA coated bracket developed by American Orthodontics. This study compared in vitro tensile bond strengths of four dental adhesives: Ketac-cem™ (KC), Vitrebond™ (VB), Transbond™ (TB) or Unite™ (UN), when used to bond to HA coated brackets and non-HA coated brackets. Bovine incisors were divided into eight groups of 20 specimens each. Each group included either an HA coated or non-HA coated bracket and one of the four adhesives. The brackets are manufactured with a Tricalcium Phosphate (TPC) coating, which is converted to an HA coating by the addition of -OH during autoclaving. The coated and non-coated brackets were bonded to the bovine teeth, which were embedded in epoxy resin blocks to fabricate the testing specimen. All of the specimens were stored in distilled water at room temperature for two weeks. This was followed by thermocycling after which the specimens were returned to water storage for an additional two weeks. The specimens were tested in tension on an lnstron Testing Machine until bond failure occurred. Mode of bond failure was determined visually by light microscope. The mean tensile bond strengths for KC and VB were each significantly less (p< 0.05) than the other three materials, while UN and TB were not significantly different. KC was the weakest at 0.68± 0.31 MPa, while UN was the strongest, 4.38±0.84 MPa. When comparing the GIG alone, there was a significant difference (p<0.0001) between the VB and the KC. The resins were not significantly different from each other. Differences between coated and non-coated were significant at p<0.05 with the noncoated brackets having the higher strength. Adhesive failure at the bracket interface for the two bracket types showed no difference for KC. TB and UN showed this type of failure significantly more with the coated brackets (p<0.05), and VB showed the opposite and more failure with non-coated brackets (p<0.01). The tensile bond strength of GIG continues to be significantly less than those of existing resins. The bond failure also revealed a high degree of within group variability. Trends relating failure mode to tensile bond strength could not be established. Greater bond strengths with the coated brackets and the GIG were not shown; however in the case of VB, the tendency for the coated brackets to fail less frequently at the bracket adhesive interface shows some promise. Further studies of these coated brackets are still warranted.
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    Recent Advances in Adhesive Bonding - The Role of Biomolecules, Nanocompounds, and Bonding Strategies in Enhancing Resin Bonding to Dental Substrates
    (Springer Nature, 2017-09) Münchow, Eliseu A.; Bottino, Marco C.; Biomedical Sciences and Comprehensive Care, School of Dentistry
    Purpose of review: To present an overview on the main agents (i.e., biomolecules and nanocompounds) and/or strategies currently available to amplify or stabilize resin-dentin bonding. Recent findings: According to studies retrieved for full text reading (2014-2017), there are currently six major strategies available to overcome resin-dentin bond degradation: (i) use of collagen crosslinking agents, which may form stable covalent bonds with collagen fibrils, thus strengthening the hybrid layer; (ii) use of antioxidants, which may allow further polymerization reactions over time; (iii) use of protease inhibitors, which may inhibit or inactivate metalloproteinases; (iv) modification of the bonding procedure, which may be performed by using the ethanol wet-bonding technique or by applying an additional adhesive (hydrophobic) coating, thereby strengthening the hybrid layer; (v) laser treatment of the substrate prior to bonding, which may cause specific topographic changes in the surface of dental substrates, increasing bonding efficacy; and (vi) reinforcement of the resin matrix with inorganic fillers and/or remineralizing agents, which may positively enhance physico-mechanical properties of the hybrid layer. Summary: With the present review, we contributed to the better understanding of adhesion concepts and mechanisms of resin-dentin bond degradation, showing the current prospects available to solve that problematic. Also, adhesively-bonded restorations may be benefited by the use of some biomolecules, nanocompounds or alternative bonding strategies in order to minimize bond strength degradation.
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    Torsional Bond Strengths of Metal Brackets Using a Glass Ionomer Cement, Light-Activated Resin, and Chemically Cured Composite Resin
    (1995) Ley, Marisa Anne; Arbuckle, Gordon R.; Baldwin, James J.; Hohlt, William F.; Katona, Thomas R.; Shanks, James C.
    Glass ionomer cements (GIC) and visible light-activated composite (VLC) adhesives offer several advantages over conventional autopolymerizing (CA) adhesives for orthodontic bonding. GIC adhere chemically to enamel thus eliminating the need for acid etching. Long-term fluoride release into the oral environment is another attractive property of the GIC in preventing enamel decalcification. VLC adhesives extend working time and result in more accurate bracket placement. The purpose of this study was to compare the torsional bond strengths of a GIC (Ketac-fil™) and a VLC (Sequence™) with a CA resin (System 1+™). Stainless steel brackets were bonded to 90 bovine teeth with one of the three adhesives according to the manufacturers' instructions. Following bonding, all specimens were stored in deionized water at 37° and then subjected to thermocycling (30 seconds in 5°C and 45°C water baths for a total of 2500 cycles).Two weeks following bonding, the samples were subjected to torsion using a MTS Bionix testing machine. GIC had a significantly (p=0.0001) lower torsional bond strength (195.3 N-mm) than VLC (349.3 N-mm) and CA resin (537.7 N-mm). The VLC had significantly (p=0.0001) lower torsional bond strength than CA resin. Although glass ionomer cements and visible light-activated composite adhesives offer advantages, these results suggest that the bond strengths are inferior to that of the conventional autopolymerizing adhesives. Discriminate use of these adhesives would be advised.