Effects of water-aging for 6 months on the durability of a novel antimicrobial and protein-repellent dental bonding agent

Biofilms at the tooth-restoration bonded interface can produce acids and cause recurrent caries. Recurrent caries is a primary reason for restoration failures. The objectives of this study were to synthesize a novel bioactive dental bonding agent containing dimethylaminohexadecyl methacrylate(DMAHDM) and 2-methacryloyloxyethyl phosphorylcholine(MPC) to inhibit biofilm formation at the tooth-restoration margin and to investigate the effects of water-aging for 6 months on the dentin bond strength and protein-repellent and antibacterial durability. A protein-repellent agent(MPC) and antibacterial agent(DMAHDM) were added to a Scotchbond multi-purpose(SBMP) primer and adhesive. Specimens were stored in water at 37 °C for 1, 30, 90, or 180 days(d).At the end of each time period, the dentin bond strength and protein-repellent and antibacterial properties were evaluated. Protein attachment onto resin specimens was measured by the micro-bicinchoninic acid approach. A dental plaque microcosm biofilm model was used to test the biofilm response. The SBMP + MPC + DMAHDM group showed no decline in dentin bond strength after water-aging for 6 months, which was significantly higher than that of the control(P < 0.05). The SBMP + MPC + DMAHDM group had protein adhesion that was only 1/20 of that of the SBMP control(P < 0.05). Incorporation of MPC and DMAHDM into SBMP provided a synergistic effect on biofilm reduction. The antibacterial effect and resistance to protein adsorption exhibited no decrease from 1 to 180 d(P > 0.1). In conclusion, a bonding agent with MPC and DMAHDM achieved a durable dentin bond strength and long-term resistance to proteins and oral bacteria. The novel dental bonding agent is promising for applications in preventive and restorative dentistry to reduce biofilm formation at the tooth-restoration margin.

Influence of dental restorative material properties on bond interface reliability： a finite element analysis

Background Varieties of restorative materials are widely used in dentistry. The aim of this study is to explore the influence of different dental restorative materials on bond interface reliability. Methods A two-dimensional finite element analysis method was adopted to simulate the shear-bond efficacy test. The influence of elastic modulus and Poisson＇s ratio were investigated separately. Several dental restorative materials including resins, metals, and ceramics were analyzed in this study. Results The deformation and peak equivalent stress level of the dentin-adhesive interface rose sharply following a decrease in the elasticity of restorative materials, especially those with a low elastic modulus range. The influence of the Poisson＇s coefficient was not significant. Ceramics and gold alloy were preferred to resin composite in restorations bearing extensive shear load during service. Conclusions Restorative materials with an elastic modulus similar to that of teeth are not always the best clinical choice. This research provides a helpful guide for the application of different restorative materials in clinical practice.

Bond strength of different adhesives to normal and caries-affected dentins

Background Currently, several systems of dentin substrate-reacting adhesives are available for use in the restorative treatment against caries. However, the bond effectiveness and property of different adhesive systems to caries-affected dentin are not fully understood. The objective of this study was to evaluate the bond strength of different adhesives to both normal dentin （ND） and caries-affected dentin （CAD） and to analyze the dentin/adhesive interracial characteristics. Methods Twenty eight extracted human molars with coronal medium carious lesions were randomly assigned to four groups according to adhesives used. ND and CAD were bonded with etch-and-rinse adhesive AdperTM Single Bond 2 （SB2） or self-etching adhesives Clearfil SE Bond （CSE）, Clearfil S3 Bond （CS3）, iBond GI （IB）. Rectangular sticks of resin-dentin bonded interfaces 0.9 mm2 were obtained. The specimens were subjected to microtensile bond strength （pTBS） testing at a crosshead speed of 1 mm/min. Mean pTBS was statistically analyzed with analysis of variance （ANOVA） and Student-Newman-Keuls tests. Interfacial morphologies were analyzed by Scanning Electron Microscopy （SEM）. Results Etch-and-rinse adhesive AdperTM Single Bond 2 yielded high bond strength when applied to both normal and caries-affected dentin. The two-step self-etching adhesive Clearfil SE Bond generated the highest bond strength to ND among all adhesives tested but a significantly reduced strength when applied to CAD. For the one-step self-etching adhesives, Clearfil S3 Bond and iBond GI, the bond strength was relatively low regardless of the dentin type. SEM inteffacial analysis revealed that hybrid layers were thicker with poorer resin tag formation and less resin-filled lateral branches in the CAD than in the ND for all the adhesives tested. Conclusion The etch-and-rinse adhesive performed more effectively to caries-affected dentin than the self-etching adhesives.