title: Effects of a hindered amine light stabilizer and a UV light absorber used in maxillofacial elastomers on human gingival epithelial cells and fibroblasts.
abstract: BACKGROUND
  Ultraviolet light absorber (UVA) and hindered amine light stabilizer (HALS) retard sun-induced pigment degradation in silicone elastomeric maxillofacial prostheses. HALS inhibits polymer degradation and UVA dissipates UV radiation. Their effects on oral cells are unknown.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the effects of UVA and HALS on membrane integrity, viability, and proliferation of human gingival fibroblasts and epithelial cells.
  
  
  METHODS
  Tinuvin 123 (HALS) and Tinuvin 213 (UVA) were assessed for cytotoxicity, individually and in a 1:1 ratio (used in elastomers; HALS/UVA). The cells were exposed to HALS, UVA, or HALS/UVA (or control media containing only the diluent), and colorimetric assays measured membrane damage, viability, and proliferation. The data (% cytotoxicity or % control) were analyzed using 3-way cross-classified fixed effects ANOVA (alpha=.05).
  
  
  RESULTS
  HALS did not negatively affect either cell type. UVA or HALS/UVA (>or= approximately 0.004%) decreased viability by >or=90% in both cell lines; lower concentrations decreased activity in epithelial cells while increasing it in fibroblasts. UVA or HALS/UVA damaged membranes of both cell lines, but epithelial cells were more resistant. UVA or HALS/UVA inhibited proliferation of both cell types similarly. There was a slight synergistic effect of HALS and UVA on membrane damage in both cell lines, but generally not on other parameters.
  
  
  CONCLUSIONS
  Although it is unknown if HALS or UVA leaches from silicone elastomers in vivo, these data suggest that relative resistance of epithelial cells to UVA-induced membrane damage, and UVA's stimulation of fibroblast viability at some concentrations, might provide some protective effect.
authors.affiliation: Dental Research Center, Department of Periodontology, College of Dentistry, University of Tennessee Health Science Center, Memphis, TN 38163, USA. dtipton@utmem.edu
authors.forename: David A
authors.initials: DA
authors.lastname: Tipton
authors.forename: J West
authors.initials: JW
authors.lastname: Lewis