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

Constructing the Enamel-Like Dentin Adhesion Interface to Achieve Durable Resin-Dentin Adhesion

Enamel adhesion is acknowledged as durable; however, achieving long-lasting dentin adhesion remains a formidable challenge due to degradation of exposed collagen matrix after acid-etching of dentin. The idea of developing an enamel-like adhesion interface holds great promise in achieving enduring dentin adhesion. In this study, we constructed an enamel-like adhesion interface using a rapid remineralization strategy comprising an acidic primer and a rapid remineralization medium. Specifically, the acidic primer of 10-methacryloyloxydecyl dihydrogen phosphate (MDP) and epigallocatechin-3-gallate (EGCG) nanocomplex (MDP@EGCG primer) was utilized to partially demineralize dentin within 30 s, and the MDP@EGCG nanocomplex showed a strong interaction with exposed collagen, enhancing collagen remineralization properties. Then, the rapid remineralization medium containing polyaspartate (Pasp) stabilized amorphous calcium and phosphorus nanoclusters (rapid Pasp-CaP) was applied to modified dentin collagen for 1 min, which caused rapid collagen remineralization within a clinically acceptable time frame. This strategy successfully generated an inorganic rough and porous adhesive interface resembling etched enamel, fundamentally addressed issues of collagen exposure, and achieved durable dentin adhesion in vitro and in vivo while also ensuring user-friendliness. It exhibited potential in prolonging the lifespan of adhesive restorations in clinical settings. In addition, it holds significant promise in the fields of caries and dentin sensitivity treatment and collagen-based tissue engineering scaffolds.

Effect of dentin conditioners on dentin bond strength: A systematic review and meta-analysis

STATEMENT OF PROBLEM

Although composite resin restorations have been widely used for dental restorations, the durability of the bond affects the rate of restoration failure. However, how multiple strategies for enhancing the resin-dentin bond affect durability is unclear.

PURPOSE

The purpose of this systematic review and meta-analysis was to evaluate the impact of dentin conditioners on resin-dentin bond strength with different pretreatments before the application of adhesives.

MATERIAL AND METHODS

The PubMed, Web of Science, EMBASE, and Cochrane Library databases were searched from 2013 to July 2023 for in vitro studies that evaluated the impact of dentin conditioners on resin-dentin bond strength. The meta-analysis was conducted using a random-effects model with pooled effect as standardized mean differences (α=.05).

RESULTS

A total of 23 studies met the inclusion criteria for qualitative analysis, of which 15 were used for quantitative analysis. The results demonstrated that, under dry bonding conditions, selective extrafibrillar demineralization dentin conditioners significantly enhanced the immediate bond strength (P<.001). The long-term bond strength was limited by the sample size of the subgroup, but a significant effect was found after using selective extrafibrillar demineralization dentin conditioners (P<.001). However, metal salt-based dentin conditioners improved the immediate bond strength only under wet bonding conditions (P=.010). Notably, acid-based dentin conditioners significantly improved the long-term bond strength under both dry and wet bonding conditions (P<.001 and P=.006).

CONCLUSIONS

The application of acid-based dentin conditioners significantly improved resin-dentin bond durability under both wet and dry bonding conditions. Furthermore, selective extrafibrillar demineralization dentin conditioners demonstrated remarkable effectiveness in improving resin-dentin bond durability under dry bonding conditions; however, more data are needed to support their use.

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.

A glycol chitosan derivative with extrafibrillar demineralization potential for self-etch dentin bonding

OBJECTIVES

Extrafibrillar demineralization is an etching technique that removes only minerals from around the collagen fibrils for resin infiltration. The intrafibrillar minerals are left intact to avoid their replacement by water that is hard for adhesive resin monomers to displace. The present work reported the synthesis of a water-soluble methacryloyloxy glycol chitosan-EDTA conjugate (GCE-MA) and evaluated its potential as an extrafibrillar demineralization agent for self-etch dentin bonding.

METHODS

Glycol chitosan-EDTA was functionalized with a methacryloyloxy functionality. Conjugation was confirmed using Fourier transform-infrared spectroscopy. The GCE-MA was used to prepare experimental self-etch primers. Extrafibrillar demineralization of the primers was evaluated with scaning electron microscopy and transmission electron microscopy. The feasibility of this new self-etch bonding approach was evaluated using microtensile bond strength testing and inhibition of dentin gelatinolytic activity. The antibacterial activity and cytotoxicity of GCE-MA were also analyzed.

RESULTS

Conjugation of EDTA and the methacryloyloxy functionality to glycol chitosan was successful. The functionalized conjugate was capable of extrafibrillar demineralization of mineralized collagen fibrils. Tensile bond strength of the experimental self-etch primer to dentin was comparable to that of phosphoric acid-etched dentin and the commercial self-etch primer Clearfil SE Bond 2. The GCE-MA also inhibited soluble rhMMP-9. In-situ zymography detected minimal fluorescence in hybrid layers conditioned with the experimental primer. The GCE-MA was noncytotoxic and possessed antibacterial activities against planktonic bacteria.

SIGNIFICANCE

Synthesis of GCE-MA brought into fruition a self-etch conditioner that selectively demineralizes the extrafibrillar mineral component of dentin. A self-etch primer prepared with GCE-MA achieved bond strengths comparable to commercial reference adhesive systems.

The roles of 10-methacryloyloxydecyl dihydrogen phosphate and its calcium salt in preserving the adhesive-dentin hybrid layer

OBJECTIVES

10-Methacryloyloxydecyl dihydrogen phosphate (MDP) has been regarded as the most effective dentin-bonding monomer for more than 20 years. Although the dentin-bonding promoting effect of MDP has been well demonstrated, the mechanisms by which it benefits the stably of collagen within the adhesive-dentin hybrid layer are not currently fully understood. The objective of this study was to investigate the roles of MDP and its calcium salt in preserving the adhesive-dentin hybrid layer.

METHODS

MDP-conditioned collagen was investigated by Fourier-transform infrared spectroscopy, Ultraviolet-visible spectroscopy, and molecular docking. The structural changes to the dentin surface upon acid-etching and MDP-conditioning were observed by SEM. X-ray diffraction and nuclear magnetic resonance were used to investigate the chemical interactions between MDP and HAp. The collagen-protecting effects of MDP and its Ca salt were investigated using in-situ zymography, rhMMP-9 colorimetric assay, hydroxyproline assay, and molecular docking.

RESULTS

MDP forms a stable collagen-phosphate complex through hydrogen bonding with the collagen in dentin. Furthermore, it generates MDP-Ca salts that are deposited on the dentin collagen scaffold, protecting it from degradation. Moreover, both free MDP and the MDP-Ca salt inhibit matrix metallopeptidase and exogenous proteases, with the inhibitory effect of the calcium salt being significantly stronger than that of the free form.

SIGNIFICANCE

MDP-based adhesives preserve the collagen within the hybrid layer by simultaneously improving collagen's resistance to exogenous enzymes and inhibiting MMP activity, both of which contribute to the longevity of dentin-resin bonding.

Interactions of two phosphate ester monomers with hydroxyapatite and collagen fibers and their contributions to dentine bond performance

OBJECTIVES

To evaluate the interactions of two phosphate ester monomers [10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) and dipentaerythritol penta-acrylate phosphate (PENTA)] with hydroxyapatite and collagen and understand their influence on dentine bonding.

METHODS

Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, nuclear magnetic resonance, ultraviolet-visible, and molecular docking were applied for separately evaluating the interactions of two monomers with hydroxyapatite and collagen. Hydrophilicity tests and morphological observation were employed to characterize pretreated dentine. Microtensile bond strength (μTBS) and nanoleakage were investigated to evaluate the bonding performance. Hydroxyproline assay, in situ zymography, and matrix metalloproteinase-9 (MMP-9) activity assay were used to confirm the MMP inhibition.

RESULTS

Chemoanalytic characterization confirmed the interactions of 10-MDP and PENTA with hydroxyapatite and collagen. The interactions of PENTA were weaker than 10-MDP. PENTA possessed better dentine tubule sealing after etching than 10-MDP. Dentine treated with PENTA was more hydrophilic than 10-MDP. 10-MDP and PENTA treating significantly increased the initial μTBS than the control group without primer conditioning. μTBS decreased significantly during aging, and the decrease was more severe in the PENTA group than 10-MDP. The 10-MDP and PENTA groups exhibited relatively less fluorescence than the control. The relative inhibition percentages of MMP-9 decreased in the order of 10-MDP-Ca salt, 10-MDP and PENTA. The 10-MDP, PENTA, and 10-MDP-Ca salt groups showed significantly lower hydroxyproline contents than the control.

CONCLUSIONS

Although PENTA adsorbed on hydroxyapatite, it did not form a stable calcium salt. The interactions of 10-MDP with hydroxyapatite and collagen are different than those of PENTA.

CLINICAL SIGNIFICANCE

The sealing of dentinal tubules by PENTA and the inhibition of MMP by 10-MDP and its calcium salts contribute to improving the dentine bonding durability.