Influence Of CPP-ACP Pretreatment On Resin-dentine Bonding

Background:Dentine hypersensitivity is commonly seen in clinic because of exposed dentine and patent dentinal tubules, including possible reason of adhesive agent. Management of hypersensitive dentine involves remineralization or occlusion of the patent dentinal tubules, and there are many different kinds of desensitizers which have different influence on bond strength as pretreatment prior to the bonding procedures. Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) has been reported to reduce sensitivity because of its capability of remineralization on dentine, but its effect on bond strength as pretreatment has been studied little.Objectives:To evaluate microtensile bond strength (μTBS) to dentine following application of a casein phosphopeptide-amorphous calcium phosphate paste (Tooth Mousse (TM)), and the effect of smear layer removal before paste application.Methods:Thirty-six intact non-carious human third molars were removed the occlusal enamel to obtain a flat dentine surface. Prior to the bonding procedures, all of the teeth were randomly divided into four groups according to whether the smear layer was removed by 15% EDTA and the surface was treated with CPP-ACP paste (Tooth Mousse, TM). Three adhesive systems (Clearfil SE Bond (CSE), G-Bond (GB) and Single Bond 2 (SB)) were applied for each group and composite resin crowns (3M ESPE Valux Plus) were constructed. The bonded teeth sectioned into slabs with a cross-sectional area of 1.0×1.0mm perpendicular to the adhesive-dentine interface and stressed in tension at a crosshead speed of 1 mm/min until failure. The data for each group was analyzed by ANOVA and LSD post hoc test at a confidence level of 95%. The debonded surfaces were examined by scanning electron microscopy (SEM).Results:1. Microtensile strength test:the resin cements, EDTA and CPP-ACP pretreatment had significant influence onμTBS (p＜0.05). Clearfil SE Bond had the strongest bond strength while G-Bond had the weakest bond strength. EDTA pretreatment could elevate microtensile bond strength (p＜0.05) of adhesive systems except G-bond. Based on EDTA pretreatment, CPP-ACP could elevate microtensile bond strength of Clearfil SE Bond and Single Bond 2 (p＜0.05).2. SEM examination:2.1 Clearfil SE BondGroup C1 (no EDTA and no CPP-ACP pretreatment):Most of the resin tags remained firmly embedded in the tubules, and collagen fibers were seen clearly.Group C2 (no EDTA and CPP-ACP pretreatment):Resin tags, collagen fibers and adhesive resin could be seen.Group C3 (EDTA and no CPP-ACP pretreatment):There are thick layers of adhesive resin above the dentine surface, and collagen fibers nearly could not be seen.Group C4 (EDTA and CPP-ACP pretreatment):Resin tags and thick layers of adhesive resin could be seen.2.2 G-Bond Group G1 (no EDTA and no CPP-ACP pretreatment):Resin tags were not obvious. Collagen fibers and small traces of adhesive resin could be seen clearly around the tubules.Group G2 (no EDTA and CPP-ACP pretreatment):Resin tags and adhesive resin were not obvious. Collagen fibers could be seen around the tubules.Group G3 (EDTA and no CPP-ACP pretreatment):Resin tags were absent in the dentinal tubules. There are thick layers of adhesive resin above the dentine surface, and collagen fibers nearly could not be seen.Group G4 (EDTA and CPP-ACP pretreatment):Resin tags were not obvious. There are thick layers of adhesive resin above the dentine surface, and collagen fibers could not be seen.2.3 Single-Bond 2Group S1 (no EDTA and no CPP-ACP pretreatment):Resin tags and peritubular collagen fibers were seen clearly.Group S2 (no EDTA and CPP-ACP pretreatment):Resin tags and peritubular collagen fibers could be seen. A thin layer of adhesive resin existed at the dentine surface.Group S3 (EDTA and no CPP-ACP pretreatment):Resin tags were seen clearly. Peritubular dentine was demineralized obviously and small traces of the adhesive resin.Group S4 (EDTA and CPP-ACP pretreatment):Resin tags and demineralized peritubular dentine were seen clearly. Adhesive resin nearly could not be seen.Conclusions:Clearfil SE Bond had the strongest bond strength while G-Bond had the weakest bond strength. EDTA pretreatment could elevate microtensile bond strength of adhesive systems except G-bond. Based on EDTA pretreatment, CPP-ACP could elevate microtensile bond strength of Clearfil SE Bond and Single Bond 2.