title: Mechanical behavior and color change of facial prosthetic elastomers after outdoor weathering in a hot and humid climate.
abstract: BACKGROUND
  A common reason for replacing a maxillofacial prosthesis is the deterioration of its properties.
  
  
  OBJECTIVE
  The purpose of this study was to compare the effect of weathering in a hot and humid climate on the tear strength, tensile strength, modulus of elasticity, elongation percentage, and color of 3 maxillofacial materials.
  
  
  METHODS
  Three silicone materials were tested. Specimens were exposed to outdoor weathering for 6 months in a hot and humid environment. Tear and tensile strengths were measured with a universal testing machine before and after outdoor weathering. Color change was evaluated by recording L*, a*, and b* values at base line and after outdoor weathering with a spectrophotometer. The ΔE, ΔL*, Δa*, and Δb* of the specimens were calculated. Data were analyzed with 2-way ANOVA and the post hoc Scheffé test (α=.05).
  
  
  RESULTS
  For all tested elastomers, outdoor weathering decreased the tear strength and modulus of elasticity values significantly (P<.001). Also, weathering reduced percentage elongation values significantly (P<.05). Tensile strength values were significantly reduced for TechSil S25 and MED-4210 specimens only (P<.05). The effect of weathering on the color of pigmented specimens was greater than the acceptable value (ΔE>3.0). The color change (ΔE) of pigmented specimens ranged from 4.31 to 6.68. A-2186 silicone elastomer experienced the greatest color changes (P<.05). Within nonpigmented specimens, none of the tested silicone elastomers showed significant color changes (P>.05).
  
  
  CONCLUSIONS
  Outdoor weathering in a hot and humid climate adversely affected the properties of silicone elastomers. The heat-polymerized TechSil S25 elastomer showed better mechanical durability and color stability compared with the room-temperature polymerized A-2186 and MED-4210 materials. TechSil S25 showed the greater values of tear and tensile strengths and elongation of specimens exposed to outdoor weathering conditions. It also showed the least amount of color change among the pigmented specimens exposed to outdoor weathering.
authors.affiliation: Associate Professor and Chairman of Substitutive Dental Sciences Department, University of Dammam, Dammam City, Kingdom of Saudi Arabia.
authors.forename: Fahad A
authors.initials: FA
authors.lastname: Al-Harbi
authors.affiliation: Associate Professor, Restorative Dental Sciences Department, University of Dammam, Dammam City, Kingdom of Saudi Arabia; Assistant Professor, Dental Biomaterials Department, Faculty of Dentistry, Mansoura University, Mansoura, Egypt.
authors.forename: Neveen M
authors.initials: NM
authors.lastname: Ayad
authors.affiliation: Professor, Substitutive Dental Sciences Department, University of Dammam, Dammam City, Kingdom of Saudi Arabia.
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Saber
authors.affiliation: Assistant Professor, Substitutive Dental Sciences Department, University of Dammam, Dammam City, Kingdom of Saudi Arabia.
authors.forename: Aws S
authors.initials: AS
authors.lastname: ArRejaie
authors.affiliation: Professor of Restorative Sciences and Biomaterialsm and Director, Division of Postdoctoral Prosthodontics, Boston University, Boston, Mass. Electronic address: smorgano@bu.edu.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Morgano
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D002980:Climate; D003116:Color; D004129:Dimethylpolysiloxanes / Q000737:chemistry; D055119:Elastic Modulus; D004548:Elasticity; D006358:Hot Temperature; D006801:Humans; D006813:Humidity; D008422:Materials Testing; D008447:Maxillofacial Prosthesis; D055595:Mechanical Phenomena; D018583:Pliability; D058105:Polymerization; D017797:Prosthesis Coloring; D011474:Prosthesis Design; D012826:Silicone Elastomers / Q000737:chemistry*; D013053:Spectrophotometry / Q000295:instrumentation; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: C076788:A 2186; D001672:Biocompatible Materials; D004129:Dimethylpolysiloxanes; D012826:Silicone Elastomers