Effect Of 3 Adhesive Systems To Glass Ceramic And Normal Dentin/caries-affected Dentin

Objective:To evaluate the effect of 3 dentin adhesives of different adhesive systems to glass ceramic and normal dental(ND)/caries-affected dentin(CAD).Methods:39 extracted human molars with medial coronal carious lesions invading into mid-dentin were selected.The softened carious dentin was removed using a slow-speed,round bur using Caries Maker as a guide.24 extracted human molars were selected and randomly distributed to 3 groups.Ceramic blocks were cemented on dentin surface using one of 3 resin cements [ Group A(Variolink N),Group B(Multilink N),Group C(Relyx Unicem)].Then the bonded speciments were embeded into custom-made mold and fixed in a universal testing machine for shear bond strength test.The fractured interfaces of the specimens after shear bond test were examined with a stereoscopic microscope(30x).15 extracted human molars were also ramdomly divided to 3 groups.Each tooth was sectioned into one CAD block and one ND block(2mm*2mm*4mm).Ceramic blocks were cemented on dentin surface using one of 3 resin cements [ Group A(Variolink N),Group B(Multilink N),Group C(Relyx Unicem)].After ammoniacal silver nitrate staining,the bonded specimens were subjected to nanoleakage evaluation using field emission SEM(FESEM).Results:1.Two-way ANOVA revealed a significant influence of both the type of dentin and the adhesive system tested on shear bond strength.And all the adhesives attained higher shear bond strength in ND [ group A :(23.04±4.79)MPa,Group B :(17.15±3.58)Mpa,Group C :(16.02±4.46)MPa] than in CAD [ group A :(18.00±3.45)MPa,Group B :(12.67±3.68)MPa,Group C :(10.88±2.88)MPa](P<0.05).Gruop B and group C demonstrated no significant difference in shear bond strength(P>0.05),while the group A revealed a significantly higher shear bond strength(P<0.05).2.Nanoleakage can be observed in all groups,but the distribution of silver deposition is different.The nanoleakage of group A and group B is concentrated at the bottom of the hybrid layer.And the hybrid layer is not observed in group C,and the nanoleakage was located between the adhesive layer and the dentin.The silver deposits in group A and B were distributed in a granular or agglomerated form,and the silver deposits in the C group were distributed in a strip.3.Two-way ANOVA revealed a significant influence of both the type of dentin and the adhesive system tested on the percentage of silver penetration.Silver nitrate uptake was higher in CAD [ group A :(0.600±0.193)%,Group B :(1.442±0.414)%,Group C :((0.802±0.223)% ] than in ND [ group A :(0.250±0.078)%,Group B :(0.630±0.132)%,Group C :(0.311±0.101)% ].Group B showed the highest percentage of silver penetration,and the percentage of silver penetration of Group C was lower than that of group B(P<0.05).Group A showed the lowest percentage of silver penetration(P<0.05).Conclusion:1.All resin conments showed significantly higher bond strength in ND than in CAD.Self-etch adhesive resin cement B and self-adhesive resin cement C demonstrated no significant difference in shear bond strength,while the total-etch adhesive resin cement A revealed a significantly higher shear bond strength.2.All three resin cements can not avoid nanoleakage completely.3.ND had better sealing ability than CAD.The total-etch adhesive resin cement A demonstrated a better sealing ability when compared with self-adhesive resin cement C,and the sealing ability of self-adhesive resin cement C was better than that of self-adhesive resin cement B.