title: Viscoelastic properties of orthodontic adhesives used for lingual fixed retainer bonding.
abstract: To evaluate the viscoelastic properties of two experimental BPA-free and one BisGMA-based orthodontic resin composite adhesives for bonding fixed retainers.
  
  
  
  A commercially available BisGMA-based (TXA: Transbond LR) and two bisphenol A-free experimental adhesives (EXA and EXB) were included in the study. The viscoelastic behavior of the adhesives was evaluated under static and dynamic conditions at dry and wet states and at various temperatures (21, 37, 50°C). The parameters determined were shear modulus (G), Young's modulus (E) under static testing and storage modulus (G1), loss tangent (tanδ) and dynamic viscosity (n*) under dynamic testing. Statistical analysis was performed by 2-way ANOVA and Bonferroni post-hoc tests (α=0.05).
  
  
  
  For static testing, a significant difference was found within material and storage condition variables and a significant interaction between the two independent variables (p<0.001 for G and E). EXA demonstrated the highest G and E values at 21°C/dry group. Dry specimens showed the highest G and E values, but with no significant difference from 21°C/wet specimens, except EXA in G. Wet storage at higher temperatures (37°C and 50°C) adversely affected all the materials to a degree ranging from 40 to 60% (p<0.001). For dynamic testing, a significant difference was also found in material and testing condition groups, with a significant interaction between the two independent variables (p<0.001 for G1and n*, p<0.01 for tanδ). Reduction in G1, and n* values, and increase in tanδ values were encountered at increased water temperatures.
  
  
  
  The apparent detrimental effect of high temperature on the reduction of properties of adhesives may contribute to the loss of stiffness of the fixed retainer configuration under ordinary clinical conditions with unfavorable effects on tooth position and stability of the orthodontic treatment result.
authors: Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Greece.
authors: D
authors: D
authors: Papadogiannis
authors: Department of Orthodontics, School of Dentistry, National and Kapodistrian University of Athens, Greece.
authors: A
authors: A
authors: Iliadi
authors: Section of Orthodontics, Developmental Sciences, School of Dentistry, Marquette University, Milwaukee, WI, USA.
authors: T G
authors: TG
authors: Bradley
authors: Dental Biomaterials Science, School of Dentistry, The University of Manchester, Manchester, UK.
authors: N
authors: N
authors: Silikas
authors: Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Greece.
authors: G
authors: G
authors: Eliades
authors: Clinic of Orthodontics and Paediatric Dentistry, School of Dental Medicine, University of Zurich, Zurich, Switzerland. Electronic address: theodore.eliades@zzm.uzh.ch.
authors: T
authors: T
authors: Eliades
mesh_terms: D003188:Composite Resins; D001840:Dental Bonding; D003738:Dental Cements; D008422:Materials Testing; D018704:Orthodontic Retainers; D019279:Resin Cements; D013314:Stress, Mechanical; D014783:Viscosity
chemical_list: D003188:Composite Resins; D003738:Dental Cements; D019279:Resin Cements
keywords: Adhesive; BPA-free; Dynamic properties; Fixed retention; Stiffness