title: Evaluation of hardness and colour change of soft liners after accelerated ageing.
abstract: BACKGROUND
  Soft liners have been developed to offer comfort to denture wearers. However, this comfort is compromised when there is a change in the properties of the material, causing colour change, solubility, absorption and hardening. These characteristics can compromise the longevity of soft liners.
  
  
  OBJECTIVE
  The aim of this in vitro study was to investigate the effect of ageing on both the hardness and colour change of two soft liners following accelerated ageing.
  
  
  METHODS
  Two denture liners, one resin based (Trusoft, Bosworth, Illinois, USA) and one silicone based (Ufi Gel P, Voco GMBH, Cuxhaven, Germany), were tested in this study for both hardness (using the Shore A scale) and colour change (using the CIE L*a*b* colour scale), initially and after 1008 hours (6 weeks) of accelerated ageing. Statistical analysis was performed using the unpaired t-test with the Welch correction.
  
  
  RESULTS
  These indicated that both materials increased in hardness and underwent colour change after accelerated ageing. The initial hardness of Trusoft was far lower than that of Ufi Gel P (18.2 Shore A units vs 34.8 Shore A units). However, for Trusoft the changes for both hardness (from 18.2 to 52.1 Shore A units) and colour change (16.85 on the CIE L*a*b* colour scale) were greater than those for Ufi Gel P, for which hardness changed from 34.8 to 36.5 Shore A units and the colour change was 5.19 on the CIE L*a*b* colour scale.
  
  
  CONCLUSIONS
  Ufi Gel P underwent less hardness and colour change after accelerated ageing than Trusoft. On the other hand, the use of Trusoft may be preferable in cases where initial softness is a major consideration, such as when relining an immediate denture after implant surgery.
authors: Department of Dental Materials and Prosthodontics, UNESP, São Paulo State University, São Paulo, Brazil. daniela@advanceddentistry.co.uk
authors: Daniela Nardi
authors: DN
authors: Mancuso
authors: Marcelo Coelho
authors: MC
authors: Goiato
authors: Bruna Carolina Rossatti
authors: BC
authors: Zuccolotti
authors: Amália
authors: A
authors: Moreno
authors: Daniela Micheline
authors: DM
authors: dos Santos
mesh_terms: D000042:Absorption; D003116:Color; D003764:Dental Materials / Q000737:chemistry*; D003822:Denture Liners; D004129:Dimethylpolysiloxanes / Q000737:chemistry; D004548:Elasticity; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D019904:Polymethyl Methacrylate / Q000737:chemistry; D012464:Saliva, Artificial / Q000737:chemistry; D012826:Silicone Elastomers / Q000737:chemistry; D012995:Solubility; D013056:Spectrophotometry, Ultraviolet; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D014783:Viscosity
chemical_list: D003764:Dental Materials; D004129:Dimethylpolysiloxanes; D012464:Saliva, Artificial; D012826:Silicone Elastomers; C483158:Ufi gel; D019904:Polymethyl Methacrylate