The Effect Of Three Dentine Desensitizers On Bond Strength Of Luting Agents

Full crown restoration needs tooth preparation in order to obtain the space and the common insertion path for prosthesis. It has been shown that a lot of dentinal tubules were exposed after tooth preparation, which increased the potential of postoperative dentine sensitivity. What's more, many other factors can also induce hypersensitivity such as temporary crowns or final restorations of poor quality and marginal microleakage. According to the hydrodynamic theory which has been widely accepted, we can prevent hypersensitivity and protect pulp tissue by mechanical closure of exposed dentinal tubules. As a result, many desensitizers come into being. And a great number of clinical trials have proved that they can effectively reduce the extent of sensitivity. However, reports about the effect of desensitizers on bond strength of luting agents are few.Objective:The purpose of this study was to observe the microscopic characteristics of dentinal tubules after using desensitizers, to test their effect on the bond strength of cementing agents and to provide an experimental basis for the selection of desensitizers and adhesives in clinic.Methods:Freshly extracted human premolars were prepared with a speed handpiece and the dentinal tubules were exposed. After using Hybrid Coat, Prime&Bond NT, anti-sensitivity toothpaste in corresponding groups, the microscopic characteristics of dentinal tubules were observed with scanning electron microscopy. After all the dentine surfaces had been treated by the selected desensitizers, castings of cobalt-chromium alloy were bonded to them by glass ionomer cement(GIC), zinc polycarboxylate cement(PCC), resin adhesive(RC) respectively. The shear bond strength of each specimen was obtained using a universal testing machine.Results:1. Hybrid Coat, Prime&Bond NT could occlude almost all the exposed tubules while anti-sensitivity toothpaste could only seal the majority of tubules. Sediments were visible no matter which desensitizer was used.2. Hybrid Coat could significantly increase the shear bond strength of GIC, but had no effect on the bond strength of PCC and RC. Application of Prime&Bond NT reduced the shear bond strength when PCC was used, but did not affect the shear bond strength of GIC, RC. The use of anti-sensitivity toothpaste obviously enhanced the shear bond strength of RC and PCC, but had no negative impacts on the shear bond strength of GIC, RC. Among the selected luting agents, GIC had the lowest shear bond strength while RC had the highest.Conclusion:1. Hybrid Coat, Prime&Bond NT and anti-sensitivity toothpaste are able to seal dentinal tubules.2. When use GIC as adhesive agent, we shoud choose Hybrid Coat as dentine desensitizer; if we choose PCC, the use of Prime&Bond NT should be avoided; if RC or PCC is selected, anti-sensitivity toothpaste is applicable.