The Effects Of Water On Degradation Of The 10-methacryloyloxydecyldihydrogenphosphate Pretreated Zirconia-resin Bond

Objectives10-methacryloyloxydecyldihydrogenphosphate(MDP)is the most representative phosphate ester monomer in the Yttria-stabilized tetragonal zirconia polycrystals(Y-TZP)bonding fields,and plays an important role in improving the strength of zirconia-resin bond.However,there are still some problems that the bonding strength decrease after aging and the hydrolysis mechanism is not clear.This study evaluated systematically the effect of different types of MDP-containing products on the strength and durability of zirconia-resin bond,and clarified the role of water on degradation of the MDP pretreated zirconia-resin bond.MethodsSeven bonding strategies were used to prepare adhesive specimens.Ctr group bonded with conventional resin cement;CSL and PSLP groups bonded with MDP-containing self-adhesive resin cements;ZP and CCP groups: MDP-containing primers pretreated the Y-TZP plates and bonded with conventional resin cement;SBU and CUB groups: MDP-containing adhesives pretreated the Y-TZP plates and bonded with conventional resin cement.Half of the specimens were subjected to 24 hours water storage and the other to aging through 30,000 thermocycles plus 90 days water storage.Shear bond strength(SBS)was measured.The same bonding strategies were used to prepare the double layers adhesive specimens,and thenmicroleakage areas were evaluated through a methylene-blue dying technique.The MDP pretreated Y-TZP specimens were tested by X-ray photoelectron spectroscopy(XPS).The same bonding strategies were used to prepare the double layers adhesive specimens.Inductively coupled plasma-mass spectrometry(ICP-MS)was used to quantify the release of phosphorus at different times.ResultsDifferent bonding strategies and aging affected the SBS values.The results of SBS showed that the bonding strength of groups with MDP-containing primers,adhesives and resin cements were significantly improved.Thermocycling and water storage significantly decreased the SBS in all groups,with the exception of MDP-containing primer groups.Moreover,microleakage phenomenon was identified at the interfaces of all bonded specimens,and the dying areas of the MDP-containing primers,adhesives and resin cements groups were lower than that of the control group.The XPS results showed that MDP could react with Y-TZP ceramics and generated Zr-O-P chemical bonds.The results of ICP-MS showed that the released of phosphorus was detected in the MDP-containing primers,adhesives and resin cements groups.The amount of released phosphorus were time dependent within a certain time.Conclusions1.All types of MDP-containin products could enhance the bonding strength between Y-TZP ceramics and composite resins.But different types of MDP-containing products had different effects.MDP-containing resin cements showed the highest bonding strength,followed by MDP-containing adhesives,and MDP-containing primers showed lower bonding strength;2.After aging,MDP-containing primers had good bonding durability,but MDP-containing adhesives and resin cements had poor bonding durability;3.Microleakage phenomenon existed in all types of MDP-containing products groups;4.The formation of Zr-O-P chemical bonds between MDP and Y-TZP ceramics were the key to improve the bonding strength.Conversely,the hydrolysis of Zr-O-P chemical bonds led to the decreasing of bonding strength.