Effect of plasma treatment of acrylic denture teeth and thermocycling on the bonding strength to heat cured acrylic denture base material


Background: Acrylic resin polymer s used in prosthodontic treatment as a denture base material for several decades.Separation and debonding of artificial teeth from denture bases present a laboratory and clinical problem affectpatient and dentist. The aim of this study is to evaluate the effect of oxygen plasma and argon plasma treatment ofacrylic teeth and thermocycling on bonding strength to hot cured acrylic resin denture base material.Materials and Methods: Sixty denture teeth (right maxillary central incisor) are selected. The denture teeth are waxedonto the beveled surface of rectangular wax block according to Japanese standard for artificial teeth. The controlgroup consisted of 20 denture teeth specimen without any treatment. The oxygen plasma group consisted of 20denture teeth specimen treated with oxygen plasma for two minutes exposure time at plasma apparatus. The argonplasma group consisted of 20 denture teeth treated with argon plasma for two minuets exposure time. All thespecimens are undergone flasking and wax elimination procedure in the conventional way. All specimens stored indistilled water for 7 days at 37°C, then half of the specimens of all groups undergoes thermocycling between 5°C -55°C in 60 seconds cycles for three days and tested for shear bond strength using universal testing machine the datawas collected and analyzed statistically using analysis of variance and independent sample t-test.Results: The plasma treated groups showed the higher mean force required to fracture the acrylic teeth from theirheat cured acrylic resin denture bases, as compared to control group, and the oxygen plasma treatment groupshowed higher shear bond value than the argon plasma treatment. The thermocycling had a deleterious effect onbonding strength for control group while the plasma treated group showed an increase in bond strength followingthermocycling.Conclusion: Plasma treatment method was an effective approach for increasing the shear bond strength as a resultof surface oxidation and chemical etching effect of oxygen plasma and micromechanical interlocking effect ofargon plasma