| Background:Resin-water replacement is not ideal during resin bonding process, causing incompletely resin-infiltrated interface, which affects composite resin bonding. Researches to avoid this "nanoleakage" resulting from "incompletely resin-infiltrated layer" have focused on the remineralization of denuded collagen fibers, using two biomimetic analogs of non-collagenous proteins to improve the remineralization of dentin hybrid layer.Objectives:To investigate remineralizating effect of dual biomimetic analogs polyvinylphosphoric acid and polyacrylic acid on resin-dentin interface, the three dentin adhesives were selected in this study: fluoro-Bond II (FL, Shofu, Japan), xeno III (xeno, Dentsply, Germany) and i Bond (ib, Heracus, Germany). The null hypothesis tested was that there are no differences in remineralized parameters of resin-infiltrated dentin specimens after1,2,3and4months immersion in either a simulated body fluid (SBF) or in a biomimetic remineralization medium(BRM).Methods:Ninety-six intact human promolars were removed occlusal enamel to obtain a flat dentine surface. Prior to the bonding procedures, all teeth were randomly divided into three groups. Three bonding agents were applied for each group and composite resin were constructed. Each tooth was then sectioned occluso-gingivally into0.9-mm-thick slabs, and two central slabs from each tooth were selected for the study, one for control group and the other for experimental group. Each experimental specimen slab was placed over Portland cement block (ca.1g) inside a sealed bottle that was filled with15mL biomimetic remineralization medium, while control specimens were similarly placed but with15mL SBF. Each group specimens were retrieved after1-4months (eight slabs per month). Each specimen examined with confocal laser scanning microscopy(CLSM) for the presence of porous zones within the hybrid layers that were permeable to an aqueous fluorescent dye. Then three parameters including fluorescence area (Area), average fluorescence(AF) and total fluorescence(TF) of each gotten images were measured by Image-Pro-Plus6.0software. The data were analyzed by ANOVA and Tukey HSD test with mean and standard deviation given.Results:1.CLSM images quantitative analysisThe biomimetic remineralization effect of remineralization medium containing dual biomimetic analogs on each group specimens at different immersion time was reflected by the change of fluorescence area of bonding interface.Fluorescence area of FL specimens were consistent after immersed in SBF for1-4months, with no significant difference (P>0.05). Fluorescence area of specimens immersed in BRM for1-3months had no significant difference (P>0.05) compared with those imersed in SBF, while until the4month the value was significantly decreased (P<0.05). It was prompted that interface of FL specimens happened remineralization after immersed for4months.Fluorescence area of xenoIII specimens immersed in SBF for1and2months increased significantly (P<0.05) and maintained a similar fluorescence area for3and4months. It suggested that the interface appeared to collagen degradation or substrate minerals demineralisation phenomena after2months. However, interface of specimens in BRM group maintained a similar fluorescence area throughout the immersion period (P>0.05). It showed that remineralization medium played the role of preventing substrate minerals lost or collagen degradated. Fluorescence areas of specimens for i Bond were consistent in SBF group for1-4months, with no significant difference (P>0.05). Fluorescent area of iBond significantly lower (P<0.05) in BRM group than in SBF group in2month, and continued to achieve the minimum area in3month, while area in4month was back to the level in2month. It was suggested that remineralization of hybrid layer had a certain self-limiting.2.CLSM images qualitative analysisFL specimens immersed in SBF after1-4months exhibited no remineralization in the hybrid layer over the entire examination period and Rhodamine B was readily identified throughout the entire hybrid layer with a thickness of20-30μm. FL specimens immersed in BRM in1,2and3months also exhibited no remineralization with a hybrid layer of25-30μm thick. Specimens in BRM group in4month showed remineralization in the hybrid layers with two narrow reduced fluorescence zones with15μm length in the middle portion. It was indicated mineral redeposition in specific zone.Xeno III specimens in SBF group in1-4months exhibited no remineralization in the hybrid layer. Rhodamine B was readily identified throughout the entire hybrid layer with significantly different thickness of7μm(1month) and10μm(2,3,4month). Xeno III specimens in BRM group in1-4months exhibited that Rhodamine B was identified through the hybrid laye with8μm thickness.I Bond specimens in SBF group in1-4months demonstrated no remineralization in the hybrid layer with20-30μm thickness. Specimens in BRM group in1month also exhibited no remineralization in hybrid layer with30μm thickness. Specimens in BRM group in2,3,4months showed remineralization in hybrid layer despite the same30pm thickness. Specimens in BRM group in2month were observed several reduced fluorescence zones in the middle or at the bottom of the hybrid layer, with half of thickness and full length of hybrid layer. Specimens in BRM group in3month demonstrated a number of reduced fluorescence zones with irregular shapes in the middle portion. Specimens in BRM group in3month showed significant reduced fluorescence zones were readily identified in the upper part with about10μm x80μm area, suggesting that distinct extents of mineral redeposition in specific zone.Conclusion: Different degrees of remineralization effects from the two biomimetic analogs on three bonding have been indicated. Remineralization effect on i Bond was most obvious, with the fastest emergence time while FL bonding was followed with a little later emergence time. Remineralization effect of xeno III bonding was not good, but played the role of preventing substrate minerals lost or collagen degradated. Therefore, the above analogues used in dental bonding to promote hybrid layer remineralization has a good prospect, which is worth further study. |
PDF Full Text Request