1.
Quantitative/qualitative analysis of adhesive-dentin interface in the presence of 10-methacryloyloxydecyl dihydrogen phosphate.
Zhou, J, Wurihan, , Shibata, Y, Tanaka, R, Zhang, Z, Zheng, K, Li, Q, Ikeda, S, Gao, P, Miyazaki, T
Journal of the mechanical behavior of biomedical materials. 2019;:71-78
Abstract
Dental adhesive provides effective retention of filling materials via adhesive-dentin hybridization. The use of co-monomers, such as 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP), is thought to be crucial for hybridization owing to their ionic-binding to calcium and co-polymerization in the polymerizable adhesives. Optimal hybridization partly depends on the mechanical properties of polymerized adhesives, which are likely to be proportional to the degree of conversion ratio. This study assessed the correlation between polymerization quality and mechanical properties at the adhesive-dentin interfaces in the presence or absence of 10-MDP. In situ Raman microspectroscopy and nanoindentation tests were used concurrently to quantify the degree of conversion ratio and dynamic mechanical properties across the adhesive-dentin interfaces. Despite the excellent diffusion and apparent higher degree of co-polymerization, 10-MDP reduced the elastic modulus of the interface. The higher viscoelastic properties of the adhesive are suggestive of poor polymerization, namely polymerization linearity related to the long carboxyl chain of 10-MDP. Such reduced mechanical integrity of hybridization could also be associated with the inhibition of nano-layering between 10-MDP and mineralized tissue in the presence of hydroxyethyl methacrylate (HEMA). This potential drawback of HEMA necessitates further qualitative/quantitative characterization of adhesive-dentin hybridization using a HEMA-free/low concentration experimental 10-MDP monomer, which theoretically possesses superior chemical bonding potential to the current HEMA-rich protocol.
2.
Molecular mechanisms underlying phosphate sensing, signaling, and adaptation in plants.
Zhang, Z, Liao, H, Lucas, WJ
Journal of integrative plant biology. 2014;(3):192-220
Abstract
As an essential plant macronutrient, the low availability of phosphorus (P) in most soils imposes serious limitation on crop production. Plants have evolved complex responsive and adaptive mechanisms for acquisition, remobilization and recycling of phosphate (Pi) to maintain P homeostasis. Spatio-temporal molecular, physiological, and biochemical Pi deficiency responses developed by plants are the consequence of local and systemic sensing and signaling pathways. Pi deficiency is sensed locally by the root system where hormones serve as important signaling components in terms of developmental reprogramming, leading to changes in root system architecture. Root-to-shoot and shoot-to-root signals, delivered through the xylem and phloem, respectively, involving Pi itself, hormones, miRNAs, mRNAs, and sucrose, serve to coordinate Pi deficiency responses at the whole-plant level. A combination of chromatin remodeling, transcriptional and posttranslational events contribute to globally regulating a wide range of Pi deficiency responses. In this review, recent advances are evaluated in terms of progress toward developing a comprehensive understanding of the molecular events underlying control over P homeostasis. Application of this knowledge, in terms of developing crop plants having enhanced attributes for P use efficiency, is discussed from the perspective of agricultural sustainability in the face of diminishing global P supplies.
3.
Experimental ammonia-free phosphate-bonded investments using Mg(H2PO4)2 solution.
Takashiba, S, Zhang, Z, Tamaki, Y
Dental materials journal. 2002;(4):322-31
Abstract
In our previous study, we investigated ammonia-free phosphate-bonded investments using Mg (H2PO4)2 powder. The purpose of the present study was to attempt usage of 50 wt% Mg (H2PO4)2 solution instead of powder. Magnesium oxide (MgO) was prepared as a binder and cristobalite was selected as a refractory. After arranging six kinds of experimental investments (A-F) with different cristobalite/MgO ratios, the fundamental properties of the dental investments were examined. The properties of the molds were influenced by the amount of MgO. Decreases in MgO showed lower mold strengths, longer setting time and larger setting expansion. According to XRD analysis, the peaks of MgH(PO4)3 x 3H2O newly formed, cristobalite and MgO were detected in the A set, but MgO peaks in F set were reduced. On the other hand, the surface of F was entirely covered by phosphorus. From these results, it was found that the usage of Mg(H2PO4)2 solution was possible for ammonia-free investments.
4.
Experimental ammonia-free phosphate-bonded investments using Mg(H2PO4)2.
Zhang, Z, Tamaki, Y, Miyazaki, T
Dental materials journal. 2001;(4):339-44
Abstract
In previous study, we found that Mg(H2PO4)2 instead of NH4H2PO4 was available as a binder material for phosphate-bonded investments and possibly could be used to develop the phosphate-bonded investment without ammonia gas release. The purpose of the present study was to develop the experimental ammonia-free phosphate-bonded investments by investigating suitable refractories. Mg(H2PO4)2.nH2O and MgO were prepared as a binder. Cristobalite and quartz were selected as refractories. The power ratio of MgO/Mg(H2PO4)2.nH2O was set constant at 1.2 according to our previous findings. Fundamental properties of dental investment such as strength, manipulation and expansion were evaluated. Using cristobalite as the refractory material, further investigations were performed. The refractory/binder ratio was definitely effective. The increase of this ratio led to low mold strength and large mold expansion. The present findings suggested that C5 was desirable for dental investment.