title: Effects of outdoor weathering on facial prosthetic elastomers.
abstract: Physical weathering is usually responsible for the degradation of maxillofacial prosthetic elastomers and the replacement of prostheses. The purpose of this study was to investigate the effects of outdoor weathering on the physical properties of four nonpigmented facial prosthetics after 1 year of exposure. In addition, simple mathematical models were developed to correlate the measured properties with irradiation time, including parameters with physical meaning. Three different medical-grade polydimethyl siloxanes (PDMSs) and an experimental chlorinated polyethylene (CPE) were examined in this study. The samples were exposed to solar radiation for 1 year in Athens, Greece. Mechanical tests (compression and tensile) were performed using universal-type testing machine, and hardness measurements were performed with a durometer (Shore A). Thermal tests were also performed with a differential scanning calorimeter. Simple mathematical models were developed to describe the examined properties. Changes observed in the properties of examined materials, before and after the exposure, reflected the effect of weathering. More specifically, two of the silicone prosthetics (Elastomer 42, TechSIL 25) seemed to become harder and more brittle, different from the other silicone (M511) sample and the CPE sample, which became softer and more ductile. Moreover mathematical models correlate the measured properties with irradiation time, and their constants indicate that duration of exposure seems to increase the degradation. Significant changes in the mechanical and thermal properties of the examined materials were observed as a result of outdoor weathering. The effect of weathering on samples' properties was introduced through its effect on the mathematical models' parameters.
authors.affiliation: Laboratory of Process Analysis and Plant Design, School of Chemical Engineering, National Technical University of Athens, Zografou Campus, 15780, Athens, Greece. peleni@central.ntua.gr.
authors.forename: Panagiota N
authors.initials: PN
authors.lastname: Eleni
authors.affiliation: Laboratory of Process Analysis and Plant Design, School of Chemical Engineering, National Technical University of Athens, Zografou Campus, 15780, Athens, Greece.
authors.forename: Magdalini
authors.initials: M
authors.lastname: Krokida
authors.affiliation: Division of Removable Prosthodontics, University of Athens, Dental School, Athens, Greece.
authors.forename: Gregory
authors.initials: G
authors.lastname: Polyzois
authors.affiliation: Department of Diagnostic Sciences, Prosthodontics, and Restorative Dentistry, School of Dentistry, University of Louisville, Louisville, KY, USA.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Gettleman
authors.affiliation: Department of Chemical Engineering, Mutah University-Kerak, Kerak, Jordan.
authors.forename: Gasan I
authors.initials: GI
authors.lastname: Bisharat
mesh_terms: D002152:Calorimetry, Differential Scanning / Q000295:instrumentation; D019245:Compressive Strength; D003799:Dental Stress Analysis; D004129:Dimethylpolysiloxanes / Q000528:radiation effects; D004548:Elasticity; D020724:Elastomers / Q000528:radiation effects*; D006244:Hardness; D006358:Hot Temperature; D008422:Materials Testing; D008447:Maxillofacial Prosthesis; D008962:Models, Theoretical; D011095:Polyethylenes / Q000528:radiation effects; D013472:Sunlight; D013718:Tensile Strength; D044366:Transition Temperature; D014783:Viscosity; D014887:Weather
chemical_list: D004129:Dimethylpolysiloxanes; D020724:Elastomers; D011095:Polyethylenes