Effects Of Arginine-Calcium Carbonate Pretreatment On The Remineralizing And Bonding Performance Of Phosphorylated Dentin

Objectives:To evaluate the effects of Arginine-calcium carbonate（Arg-CaCO₃）paste pretreatment of phosphorylated dentin on remineralizing and bonding performance during direct and indirect restorations under pulpal pressure.Methods:Healthy third molars were collected and dentin slices with 1±0.1 mm thickness and 6.5±0.5 mm diameter were prepared.After confirming the crown enamel were completely removed,the dentin slices were acid etched and treated with 2.5%Sodium trimetaphosphate（STMP）（p H=7.4,9.5）for 3 min.The Attenuated total reflection fourier transform infrared spectroscopy（ATR-FTIR）before and after treatment was recorded.Each tooth was cut about 4 mm above and 2 mm below the cemento-enamel junction,then randomly assigned to 2 groups for remineralization and bonding performance tests.Under simulated pulpal pressure,dentin of healthy third molars were abraded and acid etched for 15 s,then randomly divided into 4 groups:negative control group,without pretreatment;Arg-Ca CO₃group,applied with 8%Arg-Ca CO₃paste for 1 min and washed off;2.5%Sodium trimetaphosphate（STMP）group,treated with 2.5%STMP（p H 9.5）for 3 min;S-A group,2.5%STMP for 3 min and washed off,followed by Arg-Ca CO₃ paste for 1 min and rinsed.Meanwhile,teeth were saturated with little deionized water in a tube to stay moist with liquid pressure caused by a 15 cm altitude difference.After 24 h and 7 d,remineralization and dentin tubular occlusion were assessed by ATR-FTIR,Micro-Raman spectroscopy,Vickers hardness,Field-emission scanning electron microscope（FESEM）and Energy X-ray dispersive spectrometer（EDS）.The liquid environment was the simulated body fluid（SBF）permeated from dentin tubules due to pulpal pressure.The pulpal pressure simulation started 24 h before bonding.Samples were abraded with 600-grit Si C paper under running water and the smear layer was removed by17%EDTA（p H=7.5）for 60 s.Teeth were randomly assigned to 2 groups:DG,direct restoration;IG,indirect restoration,cemented temporarily for 7 days.In DG,samples were then applied with Clearfil SE Bond self-etch adhesive and resin composite.In IG,combining with immediate dentin sealing（IDS）technique,samples were cemented with temporary restorations by zinc-carboxylate cement.After 7 d under simulated pulpal pressure,the temporary restorations were removed and samples were cleaned solely by pumice rubbing.One side of the indirect resin composite disks were abraded with Si C paper and aluminum oxide particles.The resin composite disks were bonded by Rely X Unicem resin cement.Specimens were tested for microtensile bond strength（μTBS）and interfacial silver nanoleakage.Data were analyzed by the Kruskal-Wallis test,Mann-Whitney test,Welch ANOVA or one-way ANOVA and Tukey post hoc test（p<0.05）.Results:1.ATR-FTIR showed that 2.5%STMP（pH=9.5）significantly phosphorylated the dentin collagen fibers within 3 min,whereas 2.5%STMP（p H=7.4）was ineffective.2.After 24 h pulpal pressure simulation,only the S-A group both significantly increased the relative mineral content in ATR-FTIR and Raman analyses（P<0.05）.All experimental groups significantly increased hardness compared to the control group（P<0.05）.Both Arg-Ca CO₃ and S-A groups in FESEM effectively plugged dentin tubules in cross section（P<0.05）,while the 2.5%STMP group did not differ from the control group（P>0.05）;the 2.5%STMP group in longitudinal section was the least effective in filling the acid-etched demineralized area.EDS indicated that the deposits in cross section consisted mainly of Ca and P,with the S-A group having the highest content.3.After 7 d pulpal pressure simulation,although Raman analysis did not show significant difference in the relative mineral amounts between groups（P>0.05）,the ATR-FTIR showed that the relative mineral amounts of the experimental groups were significantly higher than those of the control group（P<0.05）,with the S-A group being significantly higher than the Arg-Ca CO₃ group（P<0.05）.In terms of hardness,the S-A group was significantly superior to the other two experimental groups（P<0.05）.The dentin tubular occlusion rate（%）of all experimental groups were significantly higher than those of the control group（P<0.05）,with the S-A group being significantly higher than the Arg-Ca CO₃ group（P<0.05）.4.TheμTBS and nanoleakage of direct restorations did not differ significantly between groups（P>0.05）,while the S-A group significantly promotedμTBS and reduced nanoleakage in indirect restorations after 7 days（P<0.05）.Conclusions:Pretreatment with Arg-CaCO₃ paste applied to the phosphorylated dentin could improve intra-and extra-tubular mineralization,increase the bond strength of indirect restorations and reduce the nanoleakage of adhesion interface after 7 days.