Complementary Mineral Analyses Of The Crystallite Behaviors In Deproteinized Dentin And The Effect On The Bonding Effectiveness Of Self-etching Adhesives

Part1Complimentary mineral analyses of deproteinized dentin by sodium hypochloriteObjectives:The purpose of this study was to investigate the effect of sodium hypochlorite (NaOC1) deproteinization on the dentin mineral phase, and to disclose the crystallites distribution and orientation related to deproteinized time and dentin spatial heterogeneity.Methods:The transversal and longitudinal dentin sections were harvested from the freshly extracted human upper first premolars, and treated by5.25%NaOC1for several specific time periods. The degree of dentin deproteinization was monitored by the attenuated total reflectance Fourier transform infrared (ATR-FTIR). X-ray microdiffraction was used to determine the mineral phase and dentin crystallite orientation. The morphological characteristics of deproteinized dentin were observed by the atomic force microscopy (AFM).Statistical analysis was carried out using SPSS version16.0(SPSS, Chicago, IL, USA).Results:The ATR-FTIR results showed that the collagen depletion was time-dependent, which achieved a plateau after deproteinization for30-180min. This plateau provided a relatively steady inorganic phase dominated surface beneficial to mineral analyses. The major inorganic phases were determined as hydroxyapatite (HAP). The crystallinity, average crystal size and crystal orientation showed obviously inhomogeneous reactions of dentin to deproteinization, depending on spatial distribution of dentin sections and NaOC1depleting time. Typical dentin tubules and intertubular dentin showed on AFM topography tended to be alternated.Conclusions:NaOC1deproteinization caused phase shifts of inorganic-organic dentin contents and the effect of dentin spatial heterogeneity and temporal deproteinization of NaOC1on the microzone crystallite behaviors was evident. Part2Effect of dentin deproteinization on the bonding effectiveness of self-etching adhesives containing functional monomersObjectives:To investigate the effect of dentin deproteinization on the bonding effectiveness of self-etching adhesives containing functional monomers.Methods:The crown dentin surfaces harvested from twenty-five freshly extracted molars were divided into two groups:control group and NaOC1-treated group (5.25%treated for60s). Three self-etching adhesives were selected:G-Bond (containing4-MET monomers), Clearfil S3Bond (containing10-MDP monomers), and Xeno-V (containing no functional monomers). Attaching ability of functional monomers to dentin was characterized using FTIR, while the evidence of possible chemical interactions was detected by film XRD. Microtensile bond strengths (MTBS) were also tested. Statistical analysis was carried out using SPSS version16.0(SPSS, Chicago, IL, USA).Results:FTIR showed the intensity of the peaks at1718cm-1assigned to CO-stretching band decreased (G-Bond> Clearfil S3Bond> Xeno-V). Film XRD results of Clearfil S3Bond showed characteristic peaks at2θ=2.5°,4.8°and7.1°, indicating the10-MDP-Ca salt formation. However, no obvious characteristic peaks were noted for the other two adhesives. The MTBS of G-Bond (containing4-MET monomers) and Clearfil S3Bond were not reduced significantly when bonding to dentin with or without NaOC1treatment (P<0.05), while the Xeno V (containing no functional monomer) showed the obviously strengths reduction.Conclusion:The self-etching adhesives containing functional monomers presented more attaching ability when interacting with dentin compared with the adhesive agent without functional monomers. The evidence of chemical interactions between dentin and functional monomers in adhesives was evident in Clearfil S3Bond groups, but showing no consistency to improve the bond strengths. Part3Effect of an8.0%arginine and calcium carbonate in-office desensitizing paste on the micro-tensile bond strength of self-etching dental adhesives to human dentinObjectives:To evaluate the effect of an8.0%arginine and calcium carbonate desensitizing paste in occluding open dentinal tubules in vitro and examine the effect of bonding between the adhesive agents and dentin after being pretreated with the8.0%arginine and calcium carbonate desensitizing paste.Methods:Two self-etching adhesives were used. Intact human premolars extracted for orthodontic reasons were used within3months of extraction. The occlusal enamel was removed and dentin slices were polished. The dentinal tubules were opened by etching with a1%citric acid solution for20s to simulate a postoperative sensitivity model. Then the specimens were randomly assigned into five groups. Group A:Specimens without any treatment served as control. Group B: Specimens were polished with the slurry of polishing powder whose component is SiO2for30s. Groups C, D and E:8.0%arginine and calcium carbonate desensitizing paste was applied. Specimens in Group C were polished for3s, and then repeated for another3s for a total of6s, according to the manufacturer’s instruction. Specimens in Group D were polished in the same way for a total of18s. Likewise, specimens in Group E were treated for an extended time as30s. Each group of specimens was randomly divided into two sub-groups in order to evaluate the effectiveness of two different adhesive agents. A one-step self-etching adhesive agent (G-Bond, GC, Japan) and a two-step self-etching adhesive agent (F1-BondⅡ, Shofu, Japan) were applied following the manufacturers’ instructions respectively. Then micro-tensile bond strengths of the ten groups were tested. SEM was used to evaluate the in vitro effect of the8.0%arginine and calcium carbonate desensitizing paste in occluding open dentinal tubules. Statistical analysis was carried out using SPSS version16.0(SPSS, Chicago, IL, USA). Results:The SEM observations showed that the8.0%arginine and calcium carbonate desensitizing paste could occlude the dentinal tubules effectively, thus may have potential benefits in preventing postoperative sensitivity based on the hydrodynamic theory. It was recommended to use an extended time of18seconds of applying when using the8.0%arginine and calcium carbonate desensitizing paste. Such treatment has no adverse effect on bonding performance to dentin when using self-etching adhesives containing functional monomers such as4-MET like G-Bond.Conclusion:The8.0%arginine and calcium carbonate in-office desensitizing paste was effective at occluding open dentinal tubules but did not affect the micro-tensile bond strength to dentin of the self-etching adhesives tested.