ABSTRACT
OBJECTIVE@#To explore the conversion of resin monomer, the change of inorganic component and the influencing factors on the oxygen inhibition layer formed on the cured surface of resin cement.@*METHODS@#Three kinds of resin cement were divided into three groups: (1) light-cured group: RelyX Veneer, NX3 (light-cured), Variolink N; (2) dual-cured group: RelyX U200 Automix, NX3 (dual-cured), Multilink Speed; (3) chemically-cured group, and the above 3 types of dual-cured resin cement cured without illumination could be used as chemically-cured resin cement. Each sample was provided with and without oxygen exposure of two matching surfaces, cured respectively, and the variables of light intensity and illumination time were set in the light-cured group and the dual-cured group. Scanning electron microscopy was used to observe the samples' surface morphology. Energy dispersive spectrometer was used to analyze the samples' composition of surface elements. Confocal Raman spectroscopy was used to measure the monomer conversion of resin cement and to obtain the thickness of the oxygen inhibition layer.@*RESULTS@#(1) On the surface of cured resin cement, the weight percentage of oxygen element in the aerobic side was higher than that in the anaerobic side (P < 0.05), and the weight percentage of inorganic element was lower than that in the anaerobic side (P < 0.05). (2) The surface monomer conversion of the cured resin cement on the aerobic surface was significantly lower than that on the anaerobic surface (P < 0.05), and the surface monomer conversion on the aerobic surface and the anaerobic surface was the lowest in the chemically-cured group (P < 0.05), the dual-cured group was the highest (P < 0.05), and the light-cured group was between them. With the increase of light intensity or illumination time, the surface monomer conversion increased (P < 0.05). (3) The thickness of the oxygen inhibition layer was the thickest in the chemically-cured group [(40.27±2.81) μm](P < 0.05), the thinnest in the dual-cured group [(21.87±5.42) μm](P < 0.05) and light-cured group [(23.73±3.84) μm] was between them. With the increase of light intensity or illumination time, the thickness of the oxygen inhibition layer of resin cement decreased (P < 0.05).@*CONCLUSION@#When resin cement is exposed to oxygen, it will form an oxygen inhibition layer, its surface's inorganic filler is less, the surface monomer conversion is lower. The surface monomer conversion and the thickness of oxygen inhibition layer are affected by curing mode and illumination factors.
Subject(s)
Materials Testing , Oxygen , Resin CementsABSTRACT
This study was aimed to investigate whether an oxygen inhibition layer (OIL) is essential for the interfacial bonding between resin composite layers or not. A composite (Z-250, 3M ESPE) was filled in two layers using two aluminum plate molds with a hole of 3.7 mm diameter. The surface of first layer of cured composite was prepared by one of five methods as followings, thereafter second layer of composite was filled and cured: Group 1 - OIL is allowed to remain on the surface of cured composite; Group 2 - OIL was removed by rubbing with acetone-soaked cotton; Group 3 - formation of the OIL was inhibited using a Mylar strip; Group 4 - OIL was covered with glycerin and light-cured; Group 5 (control) - composite was bulk-filled in a layer. The interfacial shear bond strength between two layers was tested and the fracture modes were observed. To investigate the propagation of polymerization reaction from active area having a photo-initiator to inactive area without the initiator, a flowable composite (Aelite Flow) or an adhesive resin (Adhesive of ScotchBond Multipurpose) was placed over an experimental composite (Exp_Com) which does not include a photoinitiator and light-cured. After sectioning the specimen, the cured thickness of the Exp_Com was measured. The bond strength of group 2, 3 and 4 did not show statistically significant difference with group 1. Groups 3 and 4 were not statistically significant different with control group 5. The cured thicknesses of Exp_Com under the flowable resin and adhesive resin were 20.95 (0.90) um and 42.13 (2.09), respectively.