title: Temperature triggered shape memory effect of transpolyisoprene-based polymer.
abstract: BACKGROUND
  Pure gutta-percha (trans-1, 4-polyisoprene [TPI]) has been used extensively as a main component of gutta-percha for root canal filling. TPI has the interesting shape memory property by cross-linking, and this polymer was commercialized under the product name of SMP-2 (Kuraray Corp, Kashima, Japan). Therefore, the purpose of this study was to examine the thermal properties and the mechanism of the shape memory function of cross-linked SMP-2.
  
  
  METHODS
  The crystalline of the TPI was observed by x-ray diffraction. The effects of temperature on shape recovery, recovery stress, and relaxation modulus (Er[5]) were measured in cross-linked cylindrical specimens of SMP-2. Differential scanning calorimetry was used to monitor thermal events.
  
  
  RESULTS
  On heating, a pronounced increase in recovery stress, a marked decrease in Er(5), and endothermic DSC peaks were observed over the same temperature range (38°-51°C) with shape recovery. On the other hand, on cooling, a pronounced decrease in recovery stress, a marked increase in Er(5), and an exothermic DSC peak were observed over the same temperature range (27°-33°C).
  
  
  CONCLUSIONS
  The shape memory property of TPI is derived from its crystallinity and cross-linking ability. Fixing the deformed shape and shape recovery from the deformed shape to the original shape is relatively easy to achieve by changing the temperature of SMP-2. The shape memory function of the cross-linked SMP-2 was expected to be very useful as a root canal filling material by the modification of its some thermal properties.
authors.affiliation: Department of Restorative Dentistry and Endodontology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan. Electronic address: tsukada@dent.kagoshima-u.ac.jp.
authors.forename: Gakuji
authors.initials: G
authors.lastname: Tsukada
authors.affiliation: Department of Restorative Dentistry and Endodontology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Tokuda
authors.affiliation: Department of Restorative Dentistry and Endodontology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan.
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Torii
mesh_terms: D052160:Benzothiazoles / Q000737:chemistry; D002119:Calcium Carbonate / Q000737:chemistry; D002152:Calorimetry, Differential Scanning / Q000379:methods; D003432:Cross-Linking Reagents / Q000737:chemistry; D003461:Crystallography / Q000379:methods; D055119:Elastic Modulus; D045782:Hemiterpenes / Q000138:chemical synthesis / Q000737:chemistry*; D006801:Humans; D007840:Latex / Q000138:chemical synthesis / Q000737:chemistry*; D008422:Materials Testing; D010636:Phenols / Q000737:chemistry; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D012387:Root Canal Filling Materials / Q000737:chemistry; D013229:Stearic Acids / Q000737:chemistry; D013314:Stress, Mechanical; D013455:Sulfur / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature; D013893:Thiram / Q000737:chemistry; D014025:Titanium / Q000737:chemistry; D014961:X-Ray Diffraction / Q000379:methods; D015034:Zinc Oxide / Q000737:chemistry
chemical_list: D052160:Benzothiazoles; D003432:Cross-Linking Reagents; D045782:Hemiterpenes; D007840:Latex; D010636:Phenols; D011108:Polymers; D012387:Root Canal Filling Materials; D013229:Stearic Acids; D013893:Thiram; C009495:titanium dioxide; C031183:stearic acid; C028000:dibenzothiazyl disulfide; D013455:Sulfur; C455100:1,4-polyisoprene; D014025:Titanium; D002119:Calcium Carbonate; D015034:Zinc Oxide
keywords: 4-polyisoprene; Crystallinity; gutta-percha; root canal filling material; shape memory polymer; thermal property; trans-1