title: Mechanical behavior of facial prosthetic elastomers after outdoor weathering.
abstract: OBJECTIVE
  The degradation of maxillofacial prosthetic elastomers that occurs during physical weathering is usually responsible for the replacement of prostheses. In this study the mechanical behavior of 4 non-pigmented facial prosthetic elastomers, exposed to outdoor weathering for 1 year, was investigated. The hypothesis investigated was that irradiation time did not affect the properties measured.
  
  
  METHODS
  The samples were exposed to solar radiation for 1 year in Thessaloniki (Greece). Three different types of polydimethyl siloxane (PDMS) and chlorinated polyethylene (CPE) samples were tested in this study. Mechanical tests (compressive-tensile) were performed using a universal type testing machine. Hardness tests were evaluated using a durometer tester. Simple mathematical models were developed to correlate the measured properties with irradiation time. The stress-strain data of compression and tensile tests were modeled using parameters such as maximum stress (sigma(max)), maximum strain (epsilon(max)), elasticity parameter (E), and non-linearity parameter (p), while the mathematical model used for hardness data involves initial hardness of materials (H(0)).
  
  
  RESULTS
  Two of the silicone prosthetics (Elastomer 42, TechSil 25) seem to become harder and more brittle contrary to the other silicone (M 511) and chlorinated polyethylene (CPE) samples that become softer and more ductile. Duration of exposure increases these phenomena.
  
  
  CONCLUSIONS
  The effect of irradiation time on the mechanical behavior was introduced through its effect on the models' parameters. The hypothesis was rejected since changes were observed in the model parameters.
authors.affiliation: Department of Chemical Engineering, National Technical University of Athens, Zografou Campus, Hroon Polytexneiou 9, 15780 Athens, Greece. peleni@central.ntua.gr
authors.forename: P N
authors.initials: PN
authors.lastname: Eleni
authors.forename: I
authors.initials: I
authors.lastname: Katsavou
authors.forename: M K
authors.initials: MK
authors.lastname: Krokida
authors.forename: G L
authors.initials: GL
authors.lastname: Polyzois
authors.forename: L
authors.initials: L
authors.lastname: Gettleman
mesh_terms: D000465:Algorithms; D019245:Compressive Strength; D004129:Dimethylpolysiloxanes / Q000737:chemistry / Q000528:radiation effects; D055119:Elastic Modulus; D020724:Elastomers / Q000737:chemistry* / Q000528:radiation effects; D005145:Face; D006244:Hardness; D006801:Humans; D006843:Hydrocarbons, Chlorinated / Q000737:chemistry / Q000528:radiation effects; D008422:Materials Testing; D019563:Mechanics; D008956:Models, Chemical; D020959:Polyethylene / Q000737:chemistry / Q000528:radiation effects; D019736:Prostheses and Implants; D011891:Rain; D013314:Stress, Mechanical; D013472:Sunlight; D013696:Temperature; D013718:Tensile Strength; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D004129:Dimethylpolysiloxanes; D020724:Elastomers; D006843:Hydrocarbons, Chlorinated; C013830:baysilon; D020959:Polyethylene