Objectives

Although the functional monomer glycero-phosphate dimethacrylate (GPDM) has since long been used in several dental adhesives and more recently in self-adhesive composite cements and restoratives, its mechanism of chemical adhesion to hydroxyapatite (HAp) is still unknown. We therefore investigated the chemical interaction of GPDM with HAp using diverse chemical analyzers and ultra-structurally characterized the interface of a GPDM-based primer formulation with dentin.

Methods

HAp particles were added to a GPDM solution for various periods, upon which they were thoroughly washed with ethanol and water prior to being air-dried. As control, 10-methacryloyloxydecyl dihydrogen phosphate (MDP) was used. The molecular interaction of GPDM with HAp was analyzed using X-ray diffraction (XRD) and solid-state nuclear magnetic resonance (NMR) spectroscopy. Crystal formation upon application of GPDM onto dentin was analyzed using thin-film XRD (TF-XRD). Its hydrophobicity was measured using contact-angle measurement. The interaction of GPDM with dentin was characterized using transmission electron microscopy (TEM).

Results

XRD revealed the deposition of dicalcium phosphate dihydrate (DCPD: CaHPO₄·2H₂O) on HAp after 24 h. NMR confirmed the adsorption of GPDM onto HAp. However, GPDM was easily removed after washing with water, unlike MDP that remained adhered to HAp. Dentin treated with GPDM appeared more hydrophilic compared to dentin treated with MDP. TEM disclosed exposed collagen in the hybrid layer produced by the GPDM-based primer formulation. Significance: Although GPDM adsorbed to HAp, it did not form a stable calcium salt. The bond between GPDM and HAp was weak, unlike the strong bond formed by MDP to HAp. Due to its high hydrophilicity, GPDM might be an adequate monomer for an etch-and-rinse adhesive, but appears less appropriate for a ‘mild’ self-etch adhesive that besides micro-retention ionically interacts with HAp, or for a self-adhesive restorative material.

中文翻译：

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甘油磷酸二甲基丙烯酸酯（GPDM）与羟基磷灰石和牙本质的化学相互作用

目标

尽管功能性单体磷酸二甲基丙烯酸甘油酯（GPDM）长期以来一直用于几种牙科粘合剂中，最近已用于自粘复合胶粘剂和修复剂中，但其与羟基磷灰石（HAp）的化学粘合机理仍然未知。因此，我们使用各种化学分析仪研究了GPDM与HAp的化学相互作用，并超结构化地表征了基于GPDM的底漆配方与牙本质的界面。

方法

将HAp颗粒添加到GPDM溶液中不同的时间，然后将它们用乙醇和水彻底洗涤，然后风干。作为对照，使用了10-甲基丙烯酰氧基癸基磷酸二氢酯（MDP）。使用X射线衍射（XRD）和固态核磁共振（NMR）光谱分析了GPDM与HAp的分子相互作用。使用薄膜XRD（TF-XRD）分析了将GPDM施加到牙本质上的晶体形成。使用接触角测量法测量其疏水性。GPDM与牙本质的相互作用使用透射电子显微镜（TEM）进行了表征。

结果

XRD显示二水合磷酸氢钙的沉积（DCPD：CaHPO ₄ ·2H ₂O）24小时后在HAp上。NMR证实GPDM吸附在HAp上。但是，与保持粘附于HAp的MDP不同，用水洗涤后GPDM易于除去。与用MDP处理的牙本质相比，用GPDM处理的牙本质表现出更亲水性。TEM揭示了由基于GPDM的底漆配方产生的杂化层中暴露的胶原蛋白。意义：尽管GPDM吸附在HAp上，但它并未形成稳定的钙盐。GPDM和HAp之间的键很弱，这与MDP与HAp形成的强键不同。由于其高亲水性，GPDM可能是蚀刻和冲洗粘合剂的合适单体，但对于微保留与HAp离子相互作用的“温和”自蚀刻粘合剂或自粘粘合剂而言似乎显得不太合适。修复材料。