Effect of Self-adhesive Resin Cement and Tribochemical Treatment on Bond Strength to Zirconia

Aim To evaluate the interactive effects of different self- adhesive resin cements and tribochemical treatment on bond strength to zirconia. Methodology The following self-adhesive resin cements for bonding two zirconia blocks were evaluated： Maxcem （MA）, Smartcem （SM）, Rely X Unicem Aplicap （UN）, Breeze （BR）, Biscem （BI）, Set （SE）, and Clearfil SA luting （CL）. The specimens were grouped according to conditioning as follows： Group 1, polishing with 600 grit polishing paper; Group 2, silica coating with 110 μm Al2O3 particles which modified with silica; and, Group 3, tribochemical treatment - silica coating ＋ silanization. Specimens were stored in distilled water at 37℃ for 24 hours before testing shear bond strength. Results Silica coating and tribochemical treatment significantly increased the bond strength of the MA, UN, BR, B1, SE and CL to zirconia compared to #600 polishing. For both #600 polished and silica coating treatments, MDP- containing self-adhesive resin cement CL had the highest bond strengths to zirconia. Conclusion Applying silica coating and tribochemical treatment improved the bond strength of self-adhesive resin cement to zirconia, especially for CL.

Self-Healing,Self-Adhesive and Stable Organohydrogel-Based Stretchable Oxygen Sensor with High Performance at Room Temperature

With the advent of the 5G era and the rise of the Internet of Things,various sensors have received unprecedented attention,especially wearable and stretchable sensors in the healthcare field.Here,a stretchable,self-healable,self-adhesive,and room-temperature oxygen sensor with excellent repeatability,a full concentration detection range(0-100%),low theoretical limit of detection(5.7 ppm),high sensitivity(0.2%/ppm),good linearity,excellent temperature,and humidity tolerances is fabricated by using polyacrylamide-chitosan(PAM-CS)double network(DN)organohydrogel as a novel transducing material.The PAM-CS DN organohydrogel is transformed from the PAM-CS composite hydrogel using a facile soaking and solvent replacement strategy.Compared with the pristine hydrogel,the DN organohydrogel displays greatly enhanced mechanical strength,moisture retention,freezing resistance,and sensitivity to oxygen.Notably,applying the tensile strain improves both the sensitivity and response speed of the organohydrogel-based oxygen sensor.Furthermore,the response to the same concentration of oxygen before and after self-healing is basically the same.Importantly,we propose an electrochemical reaction mechanism to explain the positive current shift of the oxygen sensor and corroborate this sensing mechanism through rationally designed experiments.The organohydrogel oxygen sensor is used to monitor human respiration in real-time,verifying the feasibility of its practical application.This work provides ideas for fabricating more stretchable,self-healable,self-adhesive,and high-performance gas sensors using ion-conducting organohydrogels.

Effect of Different Pretreatments to Post-space on Bonding Strength of Fiber Posts Luted with a Self-adhesive Resin Cement

The effects of different post-space pretreatments on the retentive force of fiber posts cemented with a self-adhesive resin cement were investigated. Twenty-eight single-canal premolars were obturated by Resilon using warm vertical compaction and treated with distilled water, 2.5% NaOCl, 17% EDTA and 2.5% NaOCI; or 17% EDTA, 2.5% NaOCI, and ultrasonic agitation （U/E/N treatment）. Subsequently, radicular dentin surfaces were observed under scanning electron microscopy （SEM）. RelyX Fiber Posts were cemented in the treated canals by using RelyX U100, and thin-slice push-out test and SEM observation of coronal and apical regions of the specimens were performed. Data were analyzed using two-way ANOVA and Tukey＇s HSD post- hoc tests, and the percentage of failure type was calculated. Ultrasonic/EDTA/NaOC1 irrigation showed the maximum effectiveness in removing the smear layer and debris on the dentin surface. The apical bond strength of the experimental groups was significantly higher than that of the control group （P〈 0.05）. Adhesive failure between cement and dentin was the most common mode of failure. No obvious RDIZ or resin tag was detected. Chemical irrigants facilitated the bonding of these fiber posts, and ultrasonic activation improved retention. Future studies should evaluate the effectiveness of irrigation on fiber post push-out strength in fatigue cycling condition.

One-pot preparation and applications of self-healing,self-adhesive PAA-PDMS elastomers

A new family of transparent,biocompatible,self-adhesive,and self-healing elastomer has been developed by a convenient and efficient one-pot reaction between poly(acrylic acid)(PAA)and hydroxyl-terminated polydimethylsiloxane(PDMSOH).The condensation reaction between PAA and PDMS-OH has been confirmed by attenuated total reflection Fourier transform infrared(ATR-FTIR)spectra.The prepared PAA-PDMS elastomers possess robust mechanical strength and strong adhesiveness to human skin,and they have fast self-healing ability at room temperature(in^10 s with the efficiency of 98%).Specifically,strain sensors were fabricated by assembling PAA-PDMS as packaging layers and polyetherimide-reduced graphene oxide(PEI-rGO)as strain-sensing layers.The PAA-PDMS/PEI-rGO sensors are stably and reliably responsive to slight physical deformations,and they can be attached onto skin directly to monitor the body’s motions.Meanwhile,strain sensors can self-heal quickly and completely,and they can be reused for the motion detecting after shallowly scratching the surface.This work provides new opportunities to manufacture high performance self-adhesive and self-healing materials.

Rapid self-healing,self-adhesive,anti-freezing,moisturizing,antibacterial and multi-stimuli-responsive PVA/starch/tea polyphenol-based composite conductive organohydrogel as flexible strain sensor

The complexity of application environment stimulates the development of wearable devices based on functional hydrogels.Among all the promising performances,self-healing and self-adhesion properties are ideal for hydrogel sensors,which can guarantee good accuracy,comfort and long service life.However,it is still a challenge to achieve simultaneous self-healing and self-adhesion in different environments(in the air,underwater and at low temperatures).Herein,a feasible new strategy was successfully carried out to prepare a starch-based composite conductive organohydrogel based on the reversible borate ester bonds formed by complexing starch/polyvinyl alcohol(PVA)/tea polyphenol(TP)with borax,and multiple hydrogen-bond interactions among PVA,starch,TP and ethylene glycol(EG).Silver nanoparticles(Ag-NPs),reduced and stabilized by TP,and MWCNTs(multi-walled carbon nanotubes)were introduced into the cross-linking networks to endow the resulting PBSTCE organohydrogel with considerable antibacterial property and conductivity,respectively.The organohydrogel possessed rapid self-healing(HE(self-healing efficiency)=96.07%in 90 s,both in the air and underwater,also at-20℃),considerable self-adhesion(both in the air and underwater,also at-20℃),remarkable stretchability(814%of elongation),anti-freezing(-20℃)and moisture-retention abilities,antibacterial activity,sensitive pH/sugar-responsiveness,and plasticity.The strain sensor formed by the PBSTCE organohydrogel can not only effectively record large-scale human motions(e.g.finger/wrist/elbow bending,walking,etc.),but also accurately capture subtle motion changes(e.g.breathing,chewing,swallowing,speaking,smiling and frowning).Moreover,the self-healed organohydrogel sensor also exhibited almost invariable mechanical,electrical and sensing behaviors.This work demonstrates a feasible strategy to construct multifunctional starch-based organohy-drogels,and promotes their efficient,stable and eco-friendly application as flexible wearable devices.

Bioinspired hybrid patches with self-adhesive hydrogel and piezoelectric nanogenerator for promoting skin wound healing

Wound management is a crucial measure for skin wound healing and is significantly important to maintaining the integrity of skins and their functions.Electrical stimulation at the wound site is a compelling strategy for skin wound repair.However,there has been an urgent need for wearable and point-of-care electrical stimulation devices that have self-adhesive and mechanical properties comparable to wound tissue.Herein,we develop a bioinspired hybrid patch with self-adhesive and piezoelectric nanogenerator(HPSP)for promoting skin wound healing,which is composed of a mussel-inspired hydrogel matrix and a piezoelectric nanogenerator based on aligned electrospun poly(vinylidene fluoride)nanofibers.The device with optimized modulus and permeability for skin wear can self-adhere to the wound site and locally produce a dynamic voltage caused by motion.We show that the HPSP not only promotes fibroblast proliferation and migration in vitro,but also effectively facilitates the collagen deposition,angiogenesis,and re-epithelialization in vivo with the increased expressions of crucial growth factors.The HPSP reduces the wound closure time of full-thickness skin defects by about 1/3,greatly accelerating the healing process.This patch can serve as wearable and real-time electrical stimulation devices,potentially useful in clinical applications of skin wound healing.

Self-adhesive lubricated coating for enhanced bacterial resistance

Limited surface lubrication and bacterial biofilm formation pose great challenges to biomedical implants.Although hydrophilic lubricated coatings and bacterial resistance coatings have been reported,the harsh and tedious synthesis greatly compromises their application,and more importantly,the bacterial resistance property has seldom been investigated in combination with the lubrication property.In this study,bioinspired by the performances of mussel and articular cartilage,we successfully synthesized self-adhesive lubricated coating and simultaneously achieved optimal lubrication and bacterial resistance properties.Additionally,we reported the mechanism of bacterial resistance on the nanoscale by studying the adhesion interactions between biomimetic coating and hydrophilic/hydrophobic tip or living bacteria via atomic force microscopy.In summary,the self-adhesive lubricated coating can effectively enhance lubrication and bacterial resistance performances based on hydration lubrication and hydration repulsion,and represent a universal and facial strategy for surface functionalization of biomedical implants.

用于人机界面的具有类皮肤性质的环境稳定水凝胶

离子水凝胶基传感器已经成为制备可穿戴电子产品的热点.然而,皮肤与传感器之间弱的界面粘合力以及水凝胶较差的耐温性严重影响了传感器的灵敏度和可靠性.受皮肤结构和功能的启发,我们将胶原蛋白整合到化学交联的水凝胶中,设计出一种新型的可皮肤附着的且环境稳定的水凝胶.该水凝胶具有较低的模量、良好的拉伸性能和良好的弹性.此外,胶原蛋白的引入使水凝胶与包括皮肤在内的多种材料具有牢固的和紧密贴合的界面.因此,该水凝胶具有极高的灵敏度(GF=10.7)、快速响应性、可忽略的迟滞行为以及广泛的监测范围,可作为人机界面以采集可靠的心电图(ECG)信号和辨别各种人体动作.值得注意的是,模仿大多数生物体的耐温机制的水凝胶在零下或常温条件下具有持久的粘合性、导电性、传感性能和机械稳定性.这种以皮肤为灵感的策略为多功能材料的设计提供了一条有效途径,并有望应用于新一代电子产品中.