title: Effect of thermocycling on hardness, absorption, solubility and colour change of soft liners.
abstract: OBJECTIVE
  The effect of artificial ageing on the hardness, absorption, solubility, and colour of soft denture liners was investigated.
  
  
  METHODS
  Liner materials based on acrylic resin (Trusoft) or silicone (Dentusil, Ufi Gel P, and Ufi Gel SC) were tested before and after 2000 thermal cycles. A total of 20 specimens of each material were tested. Half of the specimens were used for hardness and colour evaluation, and the remainder for absorption and solubility tests. The hardness evaluation was carried out using a Shore A durometer, while absorption and solubility tests were performed by storing samples in a desiccator and weighing daily until reaching constant mass (W1). After thermocycling, the samples were again weighed (W2) and dried (W3). Colour was measured using a spectrophotometer. Statistical analysis was performed using GraphPad InStat at the p < 0.05 level.
  
  
  RESULTS
  Thermocycling significantly affected the hardness of the specimens. The Trusoft material exhibited the highest absorption (1.48 ± 0.48), solubility (1.26 ± 0.28), and colour change (3.92 ± 0.33), significantly different from the other materials. There were no significant differences among the silicones in terms of absorption, solubility, and colour change, except for the colour of Dentusil, which changed (0.83 ± 0.11).
  
  
  CONCLUSIONS
  It can be concluded that silicone liners performed significantly better compared to acrylic resin.
authors.affiliation: Department of Dental Materials and Prosthodontics, UNESP-São Paulo State University, São Paulo, Brazil.
authors.forename: Daniela Nardi
authors.initials: DN
authors.lastname: Mancuso
authors.forename: Marcelo Coelho
authors.initials: MC
authors.lastname: Goiato
authors.forename: Bruna Carolina Rossatti
authors.initials: BC
authors.lastname: Zuccolotti
authors.forename: Amália
authors.initials: A
authors.lastname: Moreno
authors.forename: Daniela Micheline
authors.initials: DM
authors.lastname: dos Santos
authors.forename: Aldiéris Alves
authors.initials: AA
authors.lastname: Pesqueira
mesh_terms: D000042:Absorption; D000180:Acrylic Resins / Q000737:chemistry; D003116:Color; D003764:Dental Materials / Q000737:chemistry*; D003822:Denture Liners; D003890:Desiccation; D004129:Dimethylpolysiloxanes / Q000737:chemistry; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D008768:Methylmethacrylates / Q000737:chemistry; D019904:Polymethyl Methacrylate / Q000737:chemistry; D012826:Silicone Elastomers / Q000737:chemistry; D012995:Solubility; D013053:Spectrophotometry / Q000295:instrumentation; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors
chemical_list: D000180:Acrylic Resins; D003764:Dental Materials; D004129:Dimethylpolysiloxanes; D008768:Methylmethacrylates; D012826:Silicone Elastomers; C483158:Ufi gel; C009931:poly(ethylmethacrylate); D019904:Polymethyl Methacrylate