Electrical resistance of dental luting cements investigated by the impedance methodology related to their porosities and solubility

摘要

Introduction: Dentin hypersensitivity from oral galvanism does not happen to everyone but it could occur and be annoying. The dissimilar metals are believed to be reason of this problem. Dental luting cement is used to retain the dental prosthesis and is believed to serve as an insulator for pulpal tissue. Therefore, this study is aimed to investigate the electrical resistance of dental luting cements and the relation among the electrical resistance, their porosities and the solubility of dental luting cements. Materials and Methods: Five types of commercially available dental luting cements were used in this study including Hybond Zince Phosphate (Shofu, Japan), Fuji Ⅱ Glass lonomer (GC, Japan), Rely-X Unicem (3M, USA), Rely-X™ U-100 (3M, USA) and Superbond C&B (Sun Medical, Japan). Ten disk specimens from each dental luting cement type were prepared following manufacturer instructions and kept in the incubation for 2 weeks before testing. The porosities of all specimens were observed by Micro CT Scan before Impedance test. For the investigation of electrical resistance, all specimens were immersed in 0.1 M KCI solution at 37°C and the electrical resistance was then measured by the Impedance Methodology connected to an insulation tester. The solubility of dental luting cement was calculated from weight of specimens before and after Impedance test. All data was statistically analysed with independent t-test and one-way ANOVA at p-value of 0.05. Results: It was found that after 30 days, the electrical resistance of Hybond Zinc Phosphate cement was higher than Fuji Ⅱ Glass lonomer cement, 0.017×10~6 and 0.003×10~6 Ω, respectively. While, the electrical resistance of the other three resin dental luting cements including both types of Rely-X and Superbond C&B was still higher than capacity of measurement (over 2000 ×10~6 Ω). Additionally, the mean porosity of Superbond C&B was the significantly highest whereas there is no significant difference among the other four types of dental luting cements. Moreover, the solubility of three resin dental luting cements could not be detected. Unlike the other three resin cements, Hybond Zinc Phosphate and Fuji Ⅱ Glass lonomer cements exhibited some dissolving during testing. However, Hybond Zinc Phosphate and Fuji Ⅱ Glass lonomer cements showed no significant difference in term of solubility. This study also found no statistical correlation among the electrical resistance, the porosities and the solubility, regardless of dental luting cement types. Conclusion: Within the limitation of this study, it can be concluded that electrical resistance of dental luting cement is related to the chemical composition and setting reaction but does not relate to amount of porosity and degree of solubility. Fuji Ⅱ Glass lonomer cement showed the lowest mean electrical resistance following by Hybond Zinc Phosphate cement. While all resin dental cements showed very high electrical resistance, regardless of amount of porosities. This could imply that using resin dental luting cement could help to reduce the opportunity of dentin hypersensitivity from oral galvanism when dental prosthesis made from metals are planned.