| Recently, three new calcium-based desensitizers named NovaMin, CPP-ACP and Pro-Argin have been shown to be capable of occluding dentinal tubules to relieving hypersensitivity by forming dentin-like minerals. NovaMin is an bioactive glass, and CPP-ACP is the short name for casein phosphopeptide-amorphous calcium phosphate, and the Pro-Argin technique have been used in the desensitizing paste. However, there are no comparative results among these materials and it is unknown if use of NovaMin would affect the bonding strength between the bonding systems and dentine or not. In this study, the dentine discs treated by three desensitizers were observed by SEM/EDXA and the images were analyzed by the software of Image-Pro Plus 6.0. The microtensile test (MTT) was also done to investigate the effect of two calcium phosphate-based and fluoride-based materials on the microtensile bonding strengths between the dentine and the bonding systems.Objectives To evaluate the occluding effects of three new calcium desensitizers on dentinal tubules in vitro. Methods 25 dentin specimens with 1.00mm thick discs from freshly extracted third molars were divided into five groups randomly. After treatment with 6% citric acid, Group A was treated with distilled water, and group B~E were treated with NovaMin, Pro-argin, CPP-ACP and 75% NaF glycerin for 2min respectively. Then the teeth were vertically cleaved into two sections. The surfaces and cross sections of them were observed by the scanning electron microscope(SEM) and energy dispersive X-ray (EDXA), which also were treated by the Image-Pro Plus software.Results The percentage of dentin tubules filled were (81.6±6.1)%,(71.5±6.3)%,(43.2±2.6)%,(39.9±4.1)% for groups B,C,D and E, respectively, and the occluding depth were (30.33±2.26)μm,(24.55±2.58)μm,(16.10±4.65)μm,(8.9±1.51)μm. The difference between these groups were statistically significant (P<0.01) except for group B and C (P>0.05). However, there was no significant difference between all the groups for the Ca/P ratios (P=0.342). Conclusions NovaMin probably has better immediate occluding effects than other desensitizers and could deposit a dentin-like mineral.Aim: To evaluate the influence of calcium phosphate-based desensitizers on the microtensile bond strength(MTBS) of two different bonding agents used to bond composite resin to dentin.Methods: 24 freshly extracted intact human molars had the occlusal enamel removed and dentin ground flat under water cooling, then teeth were cut vertically in half and assigned to 2 groups of 24 according to the adhesive system: NT (Prime&Bond NT) and CS(Clearfil S~3 Bond). Each group was then randomly subdivided into 4 groups of 6, polished and treated with a different desensitizing agent (Group2:NovaMin, Group3:CPP-ACP, Group4:75% NaF glycerin), except for an untreated control Group1. Then two different agents were applied to each group and a resin composite buildup was made for each specimen about 4~5mm, which was then sectioned along its long axis to obtain 15 beams(1.0mm×1.0mm) every subgroup for the microtensile bond strength(MTBS) test. Fracture sites were observed using a light microscope Statistical analysis was performed using one-way ANOVA and Tukey's tests with the probability level set atα= 0.05Results: The mean MTBS(Mpa) for each group was, NT1: 24.45(S.D. 4.57); NT2: 17.14(3.79) ; NT3: 16.43(3.47) ; NT4: 17.68(4.79) ; CS1: 21.73(3.92) ; CS2: 20.80(3.46) ; CS~3: 20.88(3.29) ; CS4: 21.70(3.35). There were significant difference among all groups (P<0.001), but no significant difference among four CS groups (P=0.99). NovaMin showed significantly stronger dentinal tubule occlusion ability than other two groups(P<0.001). The results showed that the hybrid layer and the resin tag within the dentinal tubules could be observed on the bonding interface of all the 8 groups. The thickness of the hybrid layer in NT1 and CS1 groups were 4-7μm and 3-4μm respectively, and the resin tags of them was long and of high density. The resin tag of other groups was short and of low density with thin hybrid layer.Conclusion: The use of three desensitizers reduced significantly the dentin bond strength of Prime&Bond NT total-etch adhesive, but not that of Clearfil S~3 Bond one-step bonding system.
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