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. 2019 Jul 10;12(14):2216. doi: 10.3390/ma12142216

Table 7.

Articles included in the systematic review.

Article Author
(Year of Publication)		 Chemical Composition Application Type of Study Main Findings
Application of shape-memory polyurethane in orthodontic [40] Yung et al.
(2008)		 polyurethane copolymer [4,4′-methylene bis(phenylisocyanate) + poly(e-caprolactone)diol (PCL) + 1,4-butanediol
(4,4′methylene bis, polydiol, 1,4-butanediol)].		 Orthodontics in vitro
  • -

    polyurethane wire samples showed an average shape recovery of 80–85% at 30–50 hard segments wt.%;

  • -

    Shape recovery (%) is directly proportional to hard segments wt.%;

  • -

    the breaking stress (MPa) is inversely proportional to hard segments wt.%;

  • -

    the elongation-at-break (%) is inversely proportional to hard segments wt.%;

  • -

    the elastic modulus (MPa) is directly proportional to hard segments wt.%.
Development of an orthodontic elastic material using EMA-based resin combined with 1-butanol [41] Masuda et al.
(2011)		 polyethyl methacrylate (PEMA-TA/HX resin) + 1-butanol Orthodontics in vitro
  • -

    the modulus of compressive elasticity (MPa), instantaneous modulus of elasticity (MPa), retarded elasticity (MPa), and viscosity (MPa·s) are inversely proportional to 1-butanol wt.%;

  • -

    elastic (%) and permanent strain (%) are directly proportional to 1-butanol wt.%.
Effects of chitosan fiber addition on the properties of polyurethane with thermo-responsive shape memory [42] Kawaguchi et al.
(2016)		 polyether-based thermoplastic polyurethane (TPU), TPU + biomass nanofiber (BiNFi-s), TPU + glass fiber Orthodontics in vitro
  • -

    elastic modulus (MPa) is directly proportional to wt.% BiNFi-s;

  • -

    wt.% BiNFi-s did not influence the glass transition temperature.
Intraoral temperature triggered shape-memory effect and sealing capability of a transpolyisoprene-based polymer [4] Tsukada et al.
(2015)		 trans-1,4-polyisoprene (TPI)cross-linked SMP-2 (Kuraray Corp, Kashima, Japan) + cis-1,4-polyisoprene (CPI) + Zinc Oxide + stearic acid + sulfur + dicumyl peroxide Endodontics in vitro
  • -

    shape recovery temperature (°C) and the recovery stress (MPa) are inversely proportional to CPI wt.%;

  • -

    shape recovery temperature (°C) is inversely proportional to other cross-linking agents wt.%;

  • -

    the shape recovery stress (MPa) is directly proportional to other cross-linking agents wt.%;

  • -

    the relaxation modulus after 5s (MPa) is inversely proportional to CPI wt.% and directly proportional to other cross-linking agents wt.%;

  • -

    the sealing at 37° is directly proportional to other cross-linking agents wt.%;

  • -

    the shape recovery ratio (%) at 37° is directly proportional to other cross-linking agents wt.%.
Potential application of shape-memory plastic as elastic material in clinical orthodontics [44] Akihiko et al.
(1991)		 polynorbornen Orthodontics in vitro
  • -

    polynorbornen samples showed a permanent deformation of 9.5% after 24 h and a constant and adequate recovery force (MPa) at ~50°, stretched at ~0.5mm/sec;

  • -

    the recovery force (MPa) is directly proportional to % of stretching;

  • -

    recovery force (MPa) is influenced by the environmental temperature (decrease with temperature over 43°; increase with temperature under 25°).
Temperature triggered shape-memory effect of transpolyisoprene-based polymer [43] Tsukada et al.
(2014)		 cross-linked SMP-2 (Kuraray Corp, Kashima, Japan) + sulfur Endodontics in vitro
  • -

    shape recovery, recovery stress and relaxation modulus change as a function of temperature;

  • -

    shape recovery (%) is directly proportional to temperature (°C);

  • -

    the recovery stress (MPa) is directly proportional to heating (°C) and inversely proportional to cooling (°C);

  • -

    the relaxation modulus after 5s (MPa) is inversely proportional to temperature (°C).