| Objective: The aim of this paper is to observe the effects of three desensitizer ,one base material and one pulp capping material treating dentin surface and filling with common stratified filling technique on the nanoleakage and sheer bond strength, and to provide experimental evidence for clinical use in the filling procedure of deep caries.Methods: Sixty intact, caries-free, subfissure-free, extracted human premolars were collected, cleaned and were preserved in distilled water of -20°C within three months.The occlusal and 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 sise of 3×4×3 mm3. The binding surfaces were determined at occlusal surface, the size of binding area was 3×4mm2. Before bonding, the dentin surface was treated with EDTA(0.5mol/L,pH=7.4) for l min. Sixty specimens were randomly divided into five experimental groups and one control group. The specimens were filled with six different materials as following.Group1. Spread iBond and Spectrum TPH resin (control group);Group2. Gluma system processing agent, Spread iBond and Spectrum TPH resin;Group3. BisBlock TM resin-based adhesive, Spread iBond and Spectrum TPH resin;Group4. Green or TM desensitizer, Spread iBond and Spectrum TPH resin;Group5. Ionosit-Baseliner light-cured glass-ionomer, Spread iBond and Spectrum TPH resin;Group6. Dycal, Spread iBond and Spectrum TPH resin; Group 2 to group 6 were used as experimental groups.After all the specimens had been filled, sixty specimens were putted into normal saline at ordinary temperature for 24 hours. Then, the teeth were putted into 5°C(±2°C) and 55°C(±2°C) water alternately 1min in each bath. A total of 720 cycles was used for all specimens. The apical foramen of all teeth were closed with wax, then the entire tooth, except for the restoration area and 1 mm of the tooth surface adjacent to the restoration area, was coated with nail varnish. The teeth were then placed in a 50% ammoniacal silver nitrate aqueous solution for 24 hours in total darkness. They were rinsed in running water and exposed to a fluorescent light for 8 hours. After removal from the developing solution, the teeth were rinsed thoroughly in running water for 5 min.All 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 the specimen was for the observation of the nanoleakage on the axial section with the electron microscope, and the other one was for the shere bond strength test. One specimen was chosen from every group for SEM observation. High magnification scanning electron microscope images were recorded. The 60 specimens for the shear 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, shear speed was 0.5 mm / min, and the maximum shear stress values were recorded by the computer.Kruskal-Wallis test was used to analyze different shear stress values among six groups; Wilcoxon test was used for multiple-comparison. Asα= 0.05, if p value is﹤0.05, there is difference statistically. The characters of five materials in this study were evaluated by Combining specimens noumenal pictures, scanning electronic micrographs and statistics results of the shear strength data.Results: From specimen noumenal pictures, any silver nanoleakage could hardly be seen in group 2. There was little silver staining in group 1 and 3. On the other hand, group 4, group 5 and group 6 showed much more silver nanoleakage. There was silver staining in materials and part of the axial section in group 4, and the nanoleakage in group 6 was the most serious, indicating that Green or/and Dycal had a weaker sealing function in dentin bonding.From high-power scanning electronic micrographs, nanoleakage could hardly be seen in dentinal tubules in group 1, group2, group3 and group5. Moreover, the combination between Gluma and dentin wad tight in group 2. A lot of silver nanoleakage like thick raindrops could be observed obviously in dentinal tubules in group 4 and group 6. The results indicated that there was the smalleat nanoleakage in group 2, so Gluma had a good sealing function in dentin bonding. BisBlock TM was similar to the control group in nanoleakage. A long strip of nanoleakage was obviously seen at the dentin-Ionosit interface in Group 5, though little silver grains permeated into the dentinal tubules, so Ionosit-Baseliner had a weaker sealing function in dentin bonding. It could be observed clearly that there was the most nanoleakage and the largest gap between material and dentin in group 4 and group 6, so Green or TM and Dycal had the weakest sealing function in dentin bonding.In the sheer bond strength test, the results of Kruskal-Wallis test showed there was a significant difference among the six groups (H = 46.984, p﹤0.05). The results of Wilcoxon test indicated that there were not difference statistically in the shear strength between group 1, group2 and group3 (p﹥0.003). The shear strength in group 4 was different from that in group 2, group5 and group 6(p﹤0.003). The shear strength between group 4, group 1 and group3 was not statistically significant (p﹥0.003). The shear strength of group 5 was different from the other five groups (p﹤0.003). The same was observed in group 6.Conclusion:1 There was the least nanoleakage in group Gluma. The nanoleakage in group BisBlock TM was similar to the control group. The nanoleakage in group Green or TM, Ionosit-Baseliner and Dycal were serious because of a large gap full of silver between materials and dentin. A lot of silver nanoleakage could be observed obviously in dentinal tubules in group Green or TM and Dycal.2 The shear strength in group Gluma and BisBlock TM was higher than the control group, and the shear strength in group Green or TM was similar to the control group. The shear strength in group Ionosit-Baseliner and Dycal was lower than the control group, and the shear strength in group Ionosit-Baseliner was a little higher than in group Dycal.3 There was less nanoleakage and higher shear strength in Gluma and BisBlock TM groups than in other groups. The nanoleakage in group Gluma was the least in all groups. The shear strength in group Gluma was higher than other groups. |
