title: Evaluation of varying concentrations of nano-oxides as ultraviolet protective agents when incorporated in maxillofacial silicones: an in vitro study.
abstract: BACKGROUND
  A silicone prosthesis used to rehabilitate defects caused by cancer does not usually protect the underlying skin from ultraviolet light. Additives to the maxillofacial material may add ultraviolet protection.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the degree of ultraviolet protection after incorporating varying concentrations of nano-oxides in Cosmesil M511 medical grade silicone elastomer.
  
  
  METHODS
  Nanosized oxides of Zn and Ti were added in various concentrations (0.5%, 1.0%, 1.5%, 2.0%, and 2.5% by weight) to a silicone elastomer. Cosmesil M511 silicone without nano-oxides served as the control group for 11 experimental groups. All specimens were subjected to ultraviolet radiation with ultraviolet A (>315-400 nm) and ultraviolet B (>280-315 nm), and the percentage transmission was measured with an ultraviolet spectrophotometer. The ultraviolet protection factor was calculated. The Mann-Whitney U test was used to evaluate which of the groups differed significantly (α=.05). The Wilcoxon signed rank test was used to test the difference in values obtained for both ultraviolet ranges.
  
  
  RESULTS
  Spectrophotometric analysis indicated that the percentage-of-transmission values decreased for both the nano-oxide groups for the ultraviolet A and B ranges (P<.05) compared with the control group. The ultraviolet protection factor values increased considerably as the percentage concentration of nano-oxides was increased for both ultraviolet ranges (P<.05).
  
  
  CONCLUSIONS
  Compared with Ti nano-oxides (2% to 2.5%), Zn nano-oxides in lesser concentrations provided more significant and consistent ultraviolet protection in Cosmesil M511 elastomer.
authors.affiliation: Resident, Department of Prosthodontics, Sri Dharmasthala Manjunatheshwara College of Dental Sciences and Hospital, Dharwad, Karnataka, India.
authors.forename: Blessy Susan
authors.initials: BS
authors.lastname: Bangera
authors.affiliation: Professor, Department of Prosthodontics, Sri Dharmasthala Manjunatheshwara College of Dental Sciences and Hospital, Dharwad, Karnataka, India. Electronic address: drsatyabodh@yahoo.co.in.
authors.forename: Satyabodh S
authors.initials: SS
authors.lastname: Guttal
mesh_terms: D006801:Humans; D008422:Materials Testing; D008447:Maxillofacial Prosthesis; D053758:Nanoparticles / Q000737:chemistry*; D011474:Prosthesis Design; D012826:Silicone Elastomers / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013473:Sunscreening Agents / Q000737:chemistry*; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D014466:Ultraviolet Rays / Q000145:classification; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D012826:Silicone Elastomers; D013473:Sunscreening Agents; C044914:cosmesil; C009495:titanium dioxide; D014025:Titanium; D015034:Zinc Oxide