RESUMO
OBJECTIVES: 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. CONCLUSION: 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.
Assuntos
Elastômeros/química , Face , Próteses e Implantes , Algoritmos , Força Compressiva , Dimetilpolisiloxanos/química , Dimetilpolisiloxanos/efeitos da radiação , Módulo de Elasticidade , Elastômeros/efeitos da radiação , Dureza , Humanos , Hidrocarbonetos Clorados/química , Hidrocarbonetos Clorados/efeitos da radiação , Teste de Materiais , Mecânica , Modelos Químicos , Polietileno/química , Polietileno/efeitos da radiação , Chuva , Estresse Mecânico , Luz Solar , Temperatura , Resistência à Tração , Fatores de Tempo , Raios UltravioletaRESUMO
The effect of UVA-UVB irradiation on the mechanical properties of three different industrial types of polydimethylsiloxane and chlorinated polyethylene samples, used in maxillofacial prostheses, was investigated in this study. Mechanical properties and thermal analysis are commonly used to determine the structural changes and mechanical strength. An aging chamber was used in order to simulate the solar radiation and assess natural aging. Compression and tensile tests were conducted on a Zwick testing machine. Durometer Shore A hardness measurements were carried out in a CV digital Shore A durometer according to ASTM D 2240. Glass transition temperature was evaluated with a differential scanning calorimeter. Simple mathematical models were developed to correlate the measured properties with irradiation time. The effect of UVA-UVB irradiation on compressive behavior affected model parameters. Significant deterioration seems to occur due to irradiation in samples.
Assuntos
Dimetilpolisiloxanos/química , Dimetilpolisiloxanos/efeitos da radiação , Hidrocarbonetos Clorados/química , Hidrocarbonetos Clorados/efeitos da radiação , Nylons/química , Nylons/efeitos da radiação , Polietileno/química , Polietileno/efeitos da radiação , Cirurgia Bucal/instrumentação , Força Compressiva , Módulo de Elasticidade , Teste de Materiais/métodos , Mecânica , Doses de Radiação , Energia Solar , Estresse Mecânico , Resistência à Tração , Raios UltravioletaRESUMO
Additional types of silicone biopolymers are widely used in maxillofacial prosthetics. Therefore, the knowledge of the solar radiation's effect on their structural stability is highly important. Four different industrially synthesized biomaterials were examined, called Episil Europe 1, Europe 2, Europe 3 and Africa 3, which were exposed to solar radiation (UVA, UVB) for eight different time periods (from 8 to 168 h). Structural damages due to irradiation exposure were investigated by mechanical tests (compression) and differential scanning calorimetry (DSC) methods. Simple mathematical models were developed, containing parameters with physical meaning such as maximum stress (sigma(max)), maximum strain (epsilon), elasticity parameter (E), and viscoelastic parameter (p), for the compression test, and melting temperature (T (m)) and Enthalpy in melting point (Heat) for DSC. With increasing irradiation time their maximum stress and strain decreased significantly, and the materials lost their elasticity and molecular stability. A decrement in their melting points and heats was observed as irradiation time was increasing. Finally, experimental results demonstrated that solar radiation has a severe effect on the structural stability of the examined biomaterials.
