Effect of atmospheric pressure plasma irradiation on adhesive penetration into gaps

This study evaluated the effects of atmospheric nitrogen plasma on shear load resistance (SLR), penetration distance, and penetration area of adhesives used in the partial repair of bonded lingual retainers. Bonding gaps of 50, 100, and 150 μm were prepared between bovine enamel and composite resin, followed by plasma irradiation, and the surface free energy of the gaps was assessed. After adhesive application to the gap followed by curing the adhesive, the SLR, adhesive penetration distance, and penetration area of the treated surfaces were measured. In addition, these measurements were statistically compared with those of the untreated group. At 150 μm, plasma treatment significantly increased SLR, particularly with the 4-META/MMA-TBB resin adhesive. For all gap thicknesses, plasma treatment significantly enhanced the penetration distance and penetration area of the adhesives. These results suggest that plasma irradiation is an effective process for the partial repair of bonded retainers.