The Effect Of Cycling Mechanical Loading On The Bond Strength And Microleakage Between Dentin And Composite Resin Restoration

Objective:To study the effect of cycling mechanical loading on the bond strength and microleakage of dentin bonding interface in vitro. The further research of long-term clinical effect by different treatments under different bonding systems, provided some laboratory evidence for improving the properties of dentin adhesion agent.Methods:Selected360fresh premolars that was extracted for Orthodontic reasons, randomly divided into36groups, n=10. Divided them into two groups by the adhesion agent, the group of EasyOne (A group) and the group of Single Bond2(B group). Then this two groups were divided into6small groups, Aa, Ab, Ac and Ba, Bb, Be, according to the coating times (coating1time, coating2times, coating3times).Each group was randomly divided into3groups again, which is, one experimental group of cycling-loading10000times, one experimental group of cycling-loading60000times, one control group of non-cycling-loading.The microleakage and the bond strength were determined for each group. The experimental data was calculated and analysed by using SPSS18.0statistical analysing software. Result:1. Cycling mechanical loading could reduce the dentin bond strength and increase the microleakage of dentin interface.The bond strength of dentin bonding interface in the group of cycling-loading60000times is obviously less than the group of cycling-loading10000times and the group of non-cycling-loading with same adhesion agent coating same time, the difference is statistically significant (p<0.05), while the difference between the group of cycling-loading10000times and the group of non-cycling-loading is not statistically significant (p>0.05); the difference of microleakage between the group of cycling-loading10000times and the group of non-cycling-loading is not statistically significant (p>0.05), while the microleakage in the group of cycling-loading60000times is obviously larger than that of cycling-loading10000times and the group of non-cycling-loading, the difference is statistically significant (p<0.05).2. The effect of coating times on the bond strength and microleakage of dentin bonding interface.Comparing the group of coating1time to the group of coating2times within the same adhesion agent and cycling-loading times, the difference of the bond strength and microleakage of dentin bonding interface between the two groups is not statistically significant (p>0.05), while the microleakage in the group of coating3times is obviously larger, and its bond strength is obviously decreasing, comparing to the former two groups, the difference is statistically significant (p<0.05).3. The effect of two adhesion agent on the bond strength and microleakage of dentin bonding interface.on the condition of non-cycling-loading,Comparing the group of Easy One adhesion agent to the group of Single Bond2adhesion agent with the same coating times, the difference of the microleakage of dentin bonding interface between the two groups is not statistically significant (p>0.05), while the bond strength in the group of Single Bond2adhesion agent is obviously less and its bond strength is obviously larger than the group of Easy One adhesion agent with the same coating times (p<0.05). Comparing the group of Easy One adhesion agent to the group of Single Bond2adhesion agent with the same coating times, difference of the bond strength and microleakage of dentin bonding interface between the two groups is not statistically significant (p>0.05) on the condition of60000cycling-loading times. While on the condition of10000cycling-loading times, the microleakage in the group of Single Bond2adhesion agent is obviously less and its bond strength is obviously larger than the group of Easy One adhesion agent with the same conting times(p<0.05).4. It occurred that the fracture mode is mostly the mixed interfacial failure(74%), rarely the real interfacial failure(16%). Conclusion:1. The microleakage of the dentin bonding interface increases and the bond strength reduces with the increase of cycling mechanical loading times.2. The bond strength is ideal and the microleakage is less when coating1time or2times with either of the two adhesion agent. The bond strength significantly reduced and the microleakage significantly increased when coating3times.3. There is no difference observed in long-term efficacy when filling class I cavity with the fifth generation of adhesive system, Single Bond2, or the seventh generation of adhesive system, Easy One.