Dentin surface modification by MDP to improve dentin bonding stability: Topological enhancement and mineralization of collagen structure in hybrid layers.

Decades of research have been conducted on 10-Methacryloyloxydecyl dihydrogen phosphate (MDP) through numerous studies. The mechanisms by which its residual calcium salts benefit dentin bonding remain undetermined. The objective of the research was to investigate the role and process of remaining calcium salts in the priming procedure and their capacity for remineralization. The investigation focused on the variations in topological structure, mechanical properties, and chemical interactions between the main agent and the dentin surface. Two adhesive modes including prime-and-rinse(P&R) and prime-and-nonrinse (P&NR) utilized to evaluate the bonding performance and remineralization ability. The findings indicated that both P&R and P&NR methods could eliminate the smear-layer, uncover dentinal-tubules, and generate a textured/rough surface on the dentin. Collagen fibrils exhibited a greater presence of inorganic minerals in the P&NR mode. Compared to control group, both P&R and P&NR groups improved immediate and aging bond strength significantly (P < 0.05). AFM and 3D-STORM revealed MDP and its residual calcium salts distributed in collagen fibrils and expanded collagen matrix. In the P&NR group, TEM revealed that the dentin collagen matrix experienced some remineralization, and there was also mineralization within the collagen fibrils embedded in the bonding interface. Thus, MDP priming improved dentin bonding stability. Residual calcium salts of P&NR process can enhance topological structure of the collagen matrix and induce intrafibrillar mineralization.

Effect of the prism-interprisms three-dimension spatial microstructure on the enamel bond strength.

The prism-interprisms level of the enamel hierarchical microstructure is the largest degree of structural variation and most sophisticated structural adaptation. We studied the effect of the prism-interprisms three-dimension spatial microstructure on the enamel bond strength. We prepared 11 groups of enamel segments: longitudinally sectioned segments with or without a 45-degree bevel (group = 2), horizontally sectioned segments with or without a 45-degree bevel of three regions (the incisal, middle, and cervical) (group = 6), and tangential (labial) sectioned segments of three regions (the incisal, middle, and cervical) (group = 3). The finished surface of each segment was observed by scanning electric microscopy (SEM) before treatment with four self-etch adhesive systems and applied with four corresponding composite resins. Resin-bonded enamel samples were prepared in beams for microtensile bond strength (MTBS) tests. The results were analyzed with a three-way ANOVA followed by Tukey's post-hoc HSD multiple comparisons procedure. SEM observations revealed complex arrangements of prisms and interprisms. MTBS measurement showed that the longitudinally sectioned group had the lowest value, without significant differences between the groups with or without 45-degree bevel. Combining SEM observations and MTBS measurements, the prism-interprisms microstructure varied with the incisor regions, and different prism-interprisms microstructures allowed diverse sectioned surfaces, which could affect the enamel bonding.

Development and validation of a reversed-phase high-performance liquid chromatography-ultraviolet method for abemaciclib-related substance detection in bulk drugs.

Abemaciclib is an effective selective cyclin-dependent kinases 4 and 6 inhibitors for cancer therapy. The abemaciclib-related substances influence its efficacy and safety, and are important in process preparation studies and quality control. Thus, a reversed-phase high-performance liquid chromatography method was developed and validated for the detection of related substances in its bulk drug. The separation of abemaciclib and related substances was performed on a Phenomenon Gemini C18 column (4.6 × 250 mm, 5 µm) with a flow rate of 1.0 ml/min. The ultraviolet detection wavelength was 280 nm. Mobile phase A was composed of a mixed solution of aqueous solution and acetonitrile (9:1, v/v). The aqueous solution (pH 2.5) contained 0.025-mM potassium dihydrogen phosphate solution and 0.4% triethylamine. Mobile phase B was composed of acetonitrile. This novel method exhibits good system suitability, specificity, precision, stability, linearity (0.1-20 µg/ml), repeatability, and durability. Among abemaciclib and related substances, the lowest limit of detection and quantitation were 0.02 and 0.06 µg/ml, respectively, for abemaciclib. The recovery rates for related substances were above 95%. In addition, a novel degradation product was found during the process. In summary, a reliable reversed-phase high-performance liquid chromatography method was developed for abemaciclib-related substance detection in bulk drugs.

A novel porous silica-zirconia coating for improving bond performance of dental zirconia.

OBJECTIVES: To coat a zirconia surface with silica-zirconia using a dip-coating technique and evaluate its effect on resin-zirconia shear bond strength (SBS). METHODS: A silica-zirconia suspension was prepared and used to coat a zirconia surface using a dip-coating technique. One hundred and eighty-nine zirconia disks were divided into three groups according to their different surface treatments (polishing, sandblasting, and silica-zirconia coating). Scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and X-ray diffraction (XRD) were used to analyze the differently treated zirconia surfaces. Different primer treatments (Monobond N, Z-PRIME Plus, and no primer) were also applied to the zirconia surfaces. Subsequently, 180 composite resin cylinders (Filtek Z350) were cemented onto the zirconia disks with resin cement (RelyX Ultimate). The SBS was measured after water storage for 24 h or 6 months. The data were analyzed by two-way analysis of variance (ANOVA). RESULTS: SEM and EDX showed that the silica-zirconia coating produced a porous layer with additional Si, and XRD showed that only tetragonal zirconia was on the silica-zirconia-coating surface. Compared with the control group, the resin-zirconia SBSs of the sandblasting group and silica-zirconia-coating group were significantly increased (P<0.05). The silica-zirconia coating followed by the application of Monobond N produced the highest SBS (P<0.05). Water aging significantly reduced the resin-zirconia SBS (P<0.05). CONCLUSIONS: Dip-coating with silica-zirconia might be a feasible way to improve resin-zirconia bonding.

Enamel microstructural features of bovine and human incisors: A comparative study.

OBJECTIVE: Multiple dental researches show that bovine teeth are potential alternatives to human teeth. However, whereas cattle are herbivore, humans are omnivorous. Consequently, we sought to compare the enamel microstructures of bovine and human teeth in relation to their functional similarity. MATERIALS AND METHODS: Crowns of human and bovine teeth were first cut longitudinally, horizontally and tangentially. The appearance of enamel microstructures under the three dimensions were then analyzed using a scanning electron microscope (SEM). RESULTS: Human and bovine teeth have relatively different enamel microstructure. Bovine enamel exhibits transitional zones between adjacent HSBs bands. In addition, it has abundant interprisms interwoven with prisms. CONCLUSION: The teeth of the bovine and humans have a similar evolutionary origin, but the differences are attributed to dietary adaptation. Given the closeness of enamel microstructure of two animals' teeth, the bovine teeth could be utilized as an excellent alternative to human teeth in dental researches.

The effect of prime-and-rinse approach using MDP micellar solutions on extrafibrillar demineralization and dentin bond performance.

OBJECTIVE: This study investigated the effects of prime-and-rinse approach using 10-methacryloyloxydecyl dihydrogen phosphate (MDP) micellar solutions on extrafibrillar demineralization and dentin bond performance of etch-and-rinse adhesive. METHODS: The micellar solutions were prepared by adding 15% MDP in two ethanol-aqueous (75:25, 55:45 V/V%) solutions, referring to MDP/EtOH75 and MDP/EtOH55. After mid-coronal dentin surfaces were either etched (control) or conditioned with MDP/EtOH75 and MDP/EtOH55 and rinsed, they were applied with adhesive (Adpter Single Bond 2) in dry- or wet-bonding mode and placed with composite resin (Filtek Z350 XT). They were prepared into multiple micro-beams for micro-tensile bond strengths (MTBS) testing after storage in water for 24 h or subjecting to thermocycling. The other pretreated dentin surfaces were analyzed by TF-XRD, ATR-FTIR, HRTEM, FE-SEM, contact angle measurement and nanoindentation testing. The MTBS data was analyzed with two-way ANOVA followed by LSD post-hoc test. RESULTS: MDP/EtOH75 produced significantly greater MTBS values than MDP/EtOH55 and control after thermocycling aging in dry- or wet-bonding mode (P < 0.05). The ATR-FTIR spectrums shows that ratios of phosphate/monomer (1,034 cm-1/1,716 cm-1) on MDP/EtOH75-, MDP/EtOH55-treated dentin surfaces are 0.51 and 0.23, respectively. This is confirmed by HRTEM images and SAED pattern that intrafibrillar minerals were mostly preserved after treatment with MDP/EtOH75. MDP/EtOH75 produced significantly higher elastic modulus and nanohardness on pretreated dentin surface than MDP/EtOH55 (P < 0.05). TF-XRD pattern shows some MDP-Ca salts remained on the primed dentin surface. SIGNIFICANCE: Prime-and-rinse approach using MDP/EtOH75 micellar solution could produce mostly extrafibrillar demineralization, and greatly increase dentin bond durability in dry- or wet-bonding mode.

A novel prime-&-rinse mode using MDP and MMPs inhibitors improves the dentin bond durability of self-etch adhesive.

OBJECTIVES: The study investigated the effects of novel prime-&-rinse mode using MDP (10-methacryloyloxydecyl dihydrogenphosphate) and matrix metalloproteinase (MMPs) inhibitors on dentin microtensile bond strengths (MTBS) of self-etch adhesive, resin-dentin interface degradations, and activity of recombinant human (rh) MMP-8, -9. MATERIALS AND METHODS: Eight experimental primers were prepared using 5% and 15% of MDP ethanol-aqueous (1:1) solution in combination with/without MMPs inhibitors (1%benzalkonium chloride (BAC), 1000 µm/mL polyvinylphosphonic acid (PVPA) and 15%proanthocyanidin (PA)). Ninety human mid-coronal dentin surfaces were applied with the experimental primers, water-sprayed and gently air-dried (prime-&-rinse mode), or not (control, self-etch mode). The specimens were bonded with self-etch adhesive (Clearfil S3 Bond) and composite resin (Clearfil Majesty). The resin-bonded specimens were prepared into multiple micro-beams for MTBS tests after 24 h and 1 yr of water storage. The resin-dentin interfaces were analyzed with SEM/TEM. The inhibitory effects of eight primers on rhMMP-8, 9 were determined. The data were analyzed using two-way ANOVA and LSD multiple comparisons tests. RESULTS: Compared with control, all the primers used in prime-&-rinse mode could significantly improve long-term dentin MTBS (P < 0.05), while 5%MDP-BAC, 15%MDP and 15%MDP+MMPs inhibitors could significantly increase the short-term dentin MTBS (P < 0.05). The SEM/TEM findings revealed that the resin-dentin interfaces were stable over time when the prime-&-rinse mode used. Eight primers possessed the high inhibitory ratio of rh MMP-8, 9. CONCLUSIONS: The novel prime-&-rinse mode using 5%MDP-BAC, 15%MDP and 15%MDP+MMPs inhibitors could significantly increase the short- and long-term dentin MTBS of self-etch adhesive. This might be a supplement to contemporary dentin bonding strategies.

Effect of a novel prime-and-rinse approach on short- and long-term dentin bond strength of self-etch adhesives.

This study investigated the effects of the prime-and-rinse approach, using a 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-containing primer, on the short- and long-term dentin microtensile bond strengths (MTBSs) of mild self-etch adhesives. Half of sixty human midcoronal dentin surfaces were polished as control (self-etch approach), and the other half were polished and further treated with a 15% MDP-containing primer and thoroughly sprayed with water as prime-and-rinse approach. The dentin surfaces were treated with a self-etch adhesive, and a composite resin was placed on the surfaces. The following materials were used: Clearfil S3 Bond+Clearfil Majesty; G-Bond+Gradia Direct; Adper Easy One+Z250; and i Bond+Charisma. The MTBS was examined after 24 h and 14 months in water storage. The resin-dentin interfaces were analysed using scanning electron microscopy/transmission electron microscopy. Pretreated dentin surfaces were further analysed using scanning electron microscopy and micro-Raman spectroscopy. Compared with the self-etch approach, the prime-and-rinse approach significantly increased the dentin MTBS, regardless of the duration of storage. The scanning electron microscopy/transmission electron microscopy findings revealed that the prime-and-rinse approach removed most of the dentin smear layer. The Raman spectra of the MDP-treated dentin reveal the characteristic spectra of collagen, hydroxyapatite, and the monomer. Therefore, the prime-and-rinse approach using MDP-containing primers prior to the application of mild self-etch adhesives significantly increases the short- and long-term MTBS of dentin.

Effects of regional enamel and prism orientations on bovine enamel bond strength and cohesive strength.

This study investigated the regional microtensile bond strength (MTBS) and cohesive strength of bovine enamel. The crowns of bovine incisors were sectioned, either horizontally along incisal and cervical thirds to produce horizontal and tangential segments, or longitudinally along the midline to produce longitudinal segments. Half of the horizontal and longitudinal segments were prepared using a 45° bevel. Then, the differently sectioned enamel surfaces were treated with one- or two-step self-etch adhesives (Clearfil SE Bond or Clearfil S3 Bond) and a composite resin (Clearfil Majesty) was placed. Resin-bonded enamel samples were cut into beams for use in the MTBS tests. Labial horizontal and longitudinal segments of pure enamel beams were prepared for cohesive strength tests. Enamel microstructures were analyzed by scanning electron microscopy. Three-way anova followed by Tukey's post-hoc HSD multiple comparisons procedure showed that a 45° bevel cut did not statistically significantly improve enamel MTBS, which varied with the different regions. The longitudinally sectioned resin-bonded enamel samples had the lowest MTBS, and the horizontal enamel cohesive strength was weaker than that of the longitudinal enamel. The scanning electron microscopy fractographs indicated that rows of parallel prisms were detached from the fractured surfaces. In conclusion, the regional enamel MTBS and the cohesive strength are strongly related to the enamel microstructures and prism orientations.

[Effect of lipopolysaccharide and interleukin-1beta on the expression of inducible nitric oxide synthase gene in human periodontal ligament cells].

OBJECTIVE: To observe the effect of lipopolysaccharide(LPS) and interleukin-1beta (IL-1beta) on the expression of inducible nitric oxide synthase (iNOS) gene and nitric oxide (NO) in human periodontal ligament cells (hPDLCs). METHODS: After stimulating hPDLCs by LPS and IL-1beta, RT-PCR had been used to identify the expression of iNOS gene. The activity of iNOS in the culture was quantitated by enzyme-linked immune sorbent assay (ELISA). And the level of NO was determined by nitrate reductase method. RESULTS Slight amount of iNOS and NO had been detected in hPDLCs without sitimulation, but when stimulating with LPS and IL-1beta, the amount of the iNOS mRNA increased significantly in the cells in the time and dose dependent way (P<0.05). Under the stimulation with the same time or same dose, the productions of iNOS and NO stimulated by IL-1beta and in combination with LPS were larger than that stimulated with LPS (P<0.05). CONCLUSION: The expression NO and iNOS could be increased by stimulating hPDLCs with LPS and IL-1beta, which may contribute to the research on injecting LPS and IL-1beta at periodontal tissue of animal models.