Effects Of Gluma Desensitizer On The Nanoleakage And Shear Bond Strength Of Adhesive-dentin Interface

Objective: The aim of this paper was to observe the effects of Gluma desensitizer on the nanoleakage and shear bond strength of adhesive-dentin interface filled with resin in vitro,and to provided evidence for clinical application.Methods: Sixty intact,fresh human molars were prepared for the dentin specimens.The surrounding enamel of the crown of all the specimens was grinded with silicon carbide burs in a high-speed handpiece equipped with water spray in order to form a dentin faster with the size of 4×4mm2. Six specimens were randomly divided into group A and group B.Group A was respectively treated with Prime&Bond NT total-etch adhesives,Xeno Ⅲself-etching adhesive and AdperTM Easy One self-etching adhesive.Group B was desensitized by Gluma desensitizer before using various types of adhesives.After all the specimens had been filled with 4mm resin,sixty specimens were putted into 37 distilled water for 24 hours until the material ℃was completely cured.The apical foramen of all specimens were closed with wax,then the entire tooth,except for the restoration area and l mm of outside edge of the bonding interface,was coated with colorless nail varnish in twice,and mend them dry naturally.The specimens were immersed in a 50% ammoniacal silver nitrate solution for 24 hours in total darkness. They were exposed to a fluorescent light for 8 hours,so that the full reduction of silver ions to metallic silver.After removal from the developing solution,the specimens were rinsed thoroughly in running water for 5 min,until no visible liquid rinse black particles.All of the specimens were divided into two parts along the long axis of teeth with silicon carborundum discs in low-speed handpiece equipped with water spray.One half of specimens was for the observation of the nanoleakage on the axial section with the electron microscope,and the other half was used for shear bond strength tests.The specimens observed the nanoleakage were directioned from the center along the direction parallel with the long axis of the tooth sheet in order to formed two specimens with the width of 1mm.The specimens were followed to glossy with oil millstone of different surface size under running water.The specimens were maked a choice for the remaining length of microcracks or dentin more than 3mm by a microscope.Meet the requirements of specimens were produced to observe the nanoleakage in a scanning electron microscope(SEM).High magnification images of watching by scanning electron microscope were recorded.The sixty specimens for the shear bond strength test were fixed in self-curing resin,with exposing tooth surface and tooth long axis parallel with the ground.The specimen was fixed to the universal testing machine shearing fixture,the shear speed was 0.5mm/min,and the maximum shear stress values were recorded by the computer.Then the shear bond strength of each group was calculated as:MPa = N(Newton) / S(mm2).SPSSl6.0 statistical software was used to analyze the statistic results of the shear strength data.The t test was used to analyze different shear stress values between group A and group B.The analysis of variance was compared within group A and group B.As α =0.05,if P value <0.05,there was considered statistically significant.Results:1 Nanoleakage:Group A1,Group A2 and Group A3 of silver ions were leaked.Group B was significantly reduced compared with silver ion leakage of Group A.Compared with the close bond among each group,there was no obvious fracture.There was most serious nanoleakage in the mixed layer.Total-etch adhesives group showed much more silver nanoleakage than the group of self-etching adhesive.2 Shear bond strength:The average shear strength of group A1 was maximum in group A.The average shear strength of group B1 was maximum in group B.There was no significant difference between the group A1 and group B1.The average shear strength of group A2 was less than group B2,and between the two groups was statistically significant.The average shear strength of group A3 was less than group B3,and between the two groups was statistically significant.The average shear strength of group A1 was more than group A2,and between the two groups was statistically significant.The average shear strength of group A1 was more than group A3,and between the two groups was statistically significant.There was no significant difference between the group A2 and group A3.There were no significant difference between the groups of B.Conclusions:1 At present,the bonding material used in the clinic can not be completely avoided nanoleakage.Total-etch bonding system nanoleakage is higher than self-etching bonding system.Gluma desensitizing agents can reduce nanoleakage,especially for self-etching adhesive efficiency significantly.2 Total-etch bonding system bond strength is higher than self-etching bonding system.Gluma desensitizing agents can enhance or does not affect the shear strength,no adverse effects on the bonding effect.3 Self-etching adhesive,which is easy to operate,less post-operative sensitivity and less nanoleakage,needs to be further strengthened on bonding strength.