Effect of non-thermal oxygen-DBD plasma treatment on reducing the phthalate leach and in improving the mechanical strength properties of polymethyl methacrylate denture base and denture liner

Abstract

Phthalates and esters of aromatic carboxylic acids are used as plasticizers in certain denture soft-lining materials and tissue conditioners. The presence of phthalates is of concern, because they may induce undesirable biological effects such as hormonal disorders, reproductive toxicity, hepatocellular tumours, genital disorders owing to a capacity to bind oestrogen receptors. Despite the potential risk posed by phthalates, their use in denture and denture liner is unavoidable due to the lack of efficient substituent material. Varied curing cycles, solvent wash, thermal plasma treatment/curing, etc., are some of the methods used to eliminate the phthalate content. The use of varied curing cycles, thermal plasma curing etc., will harm the polymer matrix of the acrylic denture resulting in further complication of the acrylic-liner interface bond architecture such as increased wettability, formation of pores, formation of gas pockets, micro fractures at the edges, etc. Hence, in order to overcome the above mentioned, curing of the materials under non thermal Oxygen dielectric barrier discharge (NT-O2/DBD) plasma is suggested. Sets of research samples prepared and lined with PDMS liners (as per ISO 178) were treated with NT-O2/DBD plasma. The treated samples were subjected to mechanical strength tests and calorimetric phthalate leach test. The results indicated that NT-O2/DBD plasma reduced the phthalate content remarkably and improved the overall mechanical strength properties when compared to the controls (thermal plasma treated and heat cured samples).