| Objective:The dentin bonding surface was pretreated with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide(EDC)and proanthocyanidins(PA).The bonding strength of dentin bonding specimens was measured.To evaluate the dentin bonding effect and compare the effects of different cross-linking agents on the dentin bonding,and to provide a basis for the selection of materials for clinical application.Methods:160 intact third molars without caries in vitro were collected and polished with hard tissue cutting machine under the condition of water cooling to remove the crown enamel,exposing the dentin surface.The dentin specimens were obtained by acid etching.A total of 160 dentin specimens were randomly divided into four groups: blank control group,negative control group,EDC group,and PA group.The dentin specimens were bonded by the same experimenter according to the corresponding specifications.The shear force and bond strength were measured using a universal testing machine,and the fracture mode was observed and recorded under a microscope.The other 16 dentin specimens in each group were divided into an immediate group and an aging group according to whether they were subjected to aging treatment.The specimens were immersed in collagenase and then weighed to calculate the amount of collagen degradation in the dentin mixed layer.Results:(1)In the shear strength test,the immediate shear strength of the blank control group,negative control group,EDC group,and PA group were(6.24±0.37)MPa,(7.05±0.45)MPa,(8.33±0.36)MPa,and(9.05±0.34)MPa,respectively.P<0.001 was compared between the immediate groups,indicating that the pretreatment agent had an effect on the immediate shear strength of dentin.The EDC group and the PA group were significantly different from the negative control group(P<0.05).The immediate shear strength of the PA group was higher than that of the EDC group,and the difference between the two groups was statistically significant(P<0.05).The shear strength of each group after aging treatment decreased,and the difference was statistically significant(P<0.05).The shear strength of the blank control group,the negative control group,the EDC group,and the PA group after aging were(4.07±0.86)MPa,(4.76±0.78)MPa,(6.63±1.03)MPa,and(7.81±1.64)MPa,respectively.P<0.001 between the aging groups,indicating that the pretreatment agent had an effect on the aging shear strength of dentin.There were significant differences between blank control group and EDC group and PA group(P<0.05),negative control group and EDC group and PA group(P<0.05),and EDC group and PA group(P<0.05).(2)In the fiber degradation capacity test,The fiber degradation of blank control group,negative control group,EDC group and PA group was(17.13±4.77)mg,(13.34±2.53)mg,(8.29±1.33)mg and(5.50±0.55)mg,respectively.P<0.001 was compared between the immediate groups,indicating that the pretreatment agent had an effect on the degradation capacity of dentin fiber.The difference between blank control group and EDC group and PA group was statistically significant(P<0.05),the difference between negative control group and PA group was statistically significant(P<0.05).After aging treatment,fiber degradation increased in all groups,and the difference between blank control group,negative control group and EDC group before and after aging treatment was statistically significant(P<0.05).The fiber degradation of blank control group,negative control group,EDC group and PA group after aging was(25.18±3.92)mg,(20.58±4.98)mg,(13.68±3.79)mg and(6.20±2.56)mg,respectively.P<0.001 for comparison between the aging groups indicated that the pretreatment agent had an effect on the degradation amount of dentine fiber after aging treatment.The difference between blank control group and EDC group and PA group was statistically significant(P<0.05),the difference between negative control group and PA group was statistically significant(P< 0.05).(3)The fracture modes of dentine bonding specimens in each group were observed under stereopicroscope(50×).It was found that the proportion distribution of fracture modes before and after aging treatment was basically the same,and the proportion of interfacial fracture increased.The fracture mode of blank control group and negative control group was mainly adhesive surface fracture,and the fracture mode of EDC pretreatment group and PA pretreatment group was mainly mixed fracture mode.Conclusion:(1)Using EDC and PA as preconditioning agents in dentin bonding can significantly enhance the bonding strength of dentin,improve the stability of collagen fiber,and enhance the resistance to enzyme degradation of collagen fiber.(2)PA crosslinking agent,as a dentin adhesive preconditioning agent,is stronger than EDC crosslinking agent in enhancing dentin adhesive strength and enhancing collagen fiber resistance to enzyme degradation.(3)Compared with the traditional bonding technique,the dentin bonding effect can be greatly improved by adding the steps of PA crosslinking agent pretreatment. |
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