A novel strategy combining Mini-CEX and OSCE to assess standardized training of professional postgraduates in department of prosthodontics.

OBJECTIVE: Mini clinical evaluation exercise (mini-CEX) and objective structured clinical examination (OSCE) are widely acknowledged as effective measures of resident standardization training (RST) in European and American countries. However, in China primary mini-CEX and OSCE forms are mainly limited in undergraduate clinical examination. Little knowledge is available regarding the validity and right way of mini-CEX /OSCE evaluation system in advanced dental clinical education so far. This study aimed to explore whether combination of mini-CEX and OSCE represents a global-dimension assessment for postgraduate clinical competence in RST. METHODS: Postgraduates who received RST from June 2017 to June 2019 were selected and evaluated by modified mini-CEX/OSCE scales. Each student received evaluations at least twice in the initial and final stages of training (tested every 4 months). A questionnaire was conducted to investigate the satisfaction with the arrangement of RST. RESULTS: Mini-CEX/OSCE test results indicated that postgraduates have significantly improved their comprehensive competence in RST projects in the department of prosthodontics (P < 0.05). Compared to other master of Stomatology students, postgraduates taking up prosthodontics master's degree have made more progresses through a training period of up to 1 year and four sessions of face-to-face feedback tutoring (P < 0.05). Survey results revealed high level of satisfaction on clinical practice evaluation. CONCLUSION: Modified mini-CEX/OSCE combined evaluation system is an effective and reliable assessment tool for clinical comprehensive ability in the RST of professional graduates and can fully highlight their respective advantages on the improvement of students' clinical competency, especially after several rounds of assessments.

Investigation on Adsorption Mechanism of Peptides with Surface-Modified Super-Macroporous Resins.

Macroporous adsorption resins (MARs) have experienced rapid growth because of their unique properties and applications. Recently, it was discovered that a series of MARs with super-macroporous and diverse functional groups were synthesized to adsorb and enrich peptides; however, the detailed change mechanism of pore diameter and element composition and peptide adsorption mechanism have not yet been established. In this study, MARs and modified MARs were prepared by the surfactant reverse micelles swelling method and Friedel-Crafts reaction, and the pore diameter and element changes of these super-macroporous resin particles were accurately determined to elucidate formation processes of modified MARs. The adsorption mechanism of four peptides on different MARs was investigated. Sieving effect, electrostatic, hydrophobic, and hydrogen bonds interactions were found to play a major role in the adsorption process of peptides. Compared to that of the traditional resins, the adsorption capacity of super-macroporous MARs for peptides enormously increased. Electrostatic interactions have been explained perfectly by determining the isoelectric point. The molecular docking technology proved that the hydrogen-bonding receptor in MARs was a crucial factor for the adsorption capacity by autodock 4.26 and gromacs 5.14. These findings will enable selective adsorption of peptides by MARs, which also provides a theoretical basis for the construction of specific resin to adsorb different peptides.

Association of incisal overlaps with /s/ sound and mandibular speech movement characteristics.

INTRODUCTION: Modern anterior restorations are intended to achieve esthetic and functional reconstruction and coordination. The positioning of the anterior teeth can affect pronunciation, but the effect of anatomic factors on pronunciation after anterior restoration has not been critically tested. The purpose of this study was to provide possible references for the design of the anterior overlaps in future anterior restorations. METHODS: Thirty-nine subjects with normal occlusion (NO) participated. They completed questionnaires, were examined clinically, and were recorded pronouncing the /s/ sound. Links between overlaps with spectral features of the /s/ sound and mandibular movements during speech were investigated. RESULTS: When NO subjects pronounced the /s/ sound, the average fricative length was 202.54 ± 44.57 ms; the average noise peak was 4052.89 ± 445.80 Hz, which was in the high-frequency region; the center of gravity was 2452.85 ± 623.50 Hz; and the mean intensity was 40.61 ± 4.99 dB. The mandibular speech movements showed a slightly long and narrow backward and downward oblique path. Overbite positively correlated with the /s/ sound's noise peak frequency and negatively correlated with the maximum closing speed. Overjet negatively correlated with the maximum distance in the sagittal plane. CONCLUSIONS: This is the first attempt to correlate the spectral features of the /s/ sound and speaking movements with incisal overlaps. The results suggest that significant associations exist and that these associations can offer some references for esthetic anterior restoration.

Piezo Mediates the Mechanosensation and Injury-Repair of Pulpo-Dentinal Complex.

OBJECTIVES: The aim of this research was to investigate the functions of Piezo channels in dentin defect, including mechanical signalling and odontoblast responses. METHODS: Rat dentin-defect models were constructed, and spatiotemporal expression of Piezo proteins was detected in the pulpo-dentinal complex. Real-time polymerase chain reaction (rtPCR) was used to investigate the functional expression pattern of Piezo channels in odontoblasts. Moreover, RNA interference technology was employed to uncover the underlying mechanisms of the Piezo-driven inflammatory response and repair under fluid shear stress (FSS) conditions in vitro. RESULTS: Piezo1 and Piezo2 were found to be widely expressed in the odontoblast layer and dental pulp in the rat dentin-defect model during the end stage of reparative dentin formation. The expression levels of the Piezo1 and Piezo2 genes in MDPC-23 cells were high in the initial stage under FSS loading and then decreased over time. Moreover, the expression trends of inflammatory, odontogenic, and mineralisation genes were generally contrary to those of Piezo1 and Piezo2 over time. After silencing of Piezo1/Piezo2, FSS stimulation resulted in significantly higher expression of inflammatory, odontogenesis, and mineralisation genes in MDPC-23 cells. Finally, the expression of genes involved in the integrin ß1/ERK1 and Wnt5b/ß-catenin signalling pathways was changed in response to RNA silencing of Piezo1 and Piezo2. CONCLUSIONS: Piezo1 and Piezo2 may be involved in regulating the expression of inflammatory and odontogenic genes in odontoblasts stimulated by FSS.

A highly sensitive electrochemical immunosensor based on rGO-PEI-Ag nanocomposites for the detection of tilmicosin.

A label-free electrochemical immunosensor was developed to rapidly detect tilmicosin (TMC) residues in pork and milk. The immunosensor was constructed by immobilizing a high-affinity monoclonal antibody against TMC on an rGO-PEI-Ag nanocomposite-modified electrode. The rGO-PEI-Ag nanocomposites were prepared by mixing polyethyleneimine (PEI) modified reduced graphene oxide (rGO) with AgNO3 solution. The prepared rGO-PEI-Ag nanocomposites showed good redox activity and conductivity, as characterized by ultraviolet-visible spectroscopy (UV-Vis), transmission electron microscopy (TEM), and X-ray diffraction (XRD). During the preparation process, staphylococcal protein A (SPA) was added to targetedly bind the Fc segment of the monoclonal antibody. The immunosensor showed a low detection limit (LOD) of 0.0013 ng/mL, a linear range of 0.01-100 ng/mL, and recoveries ranging from 92.77 to 100.02% in pork and 92.26-101.23% in milk. Furthermore, the immunosensor exhibited good stability, reproducibility, and specificity in detecting TMC in pork and milk real samples.

The effect of transient proanthocyanidins preconditioning on the cross-linking and mechanical properties of demineralized dentin.

Proanthocyanidin-based preconditioners were prepared by adding powdered proanthocyanidins-rich grape seed extract to various solvents at different concentrations. Demineralized dentin specimens were preconditioned for 20, 30, 60 or 120 s, followed by the evaluation of their cross-linking degree, mechanical properties and micromorphology. The cross-linking degree of the demineralized dentin collagen exhibited concentration- and time- dependent increase after preconditioning treatment, irrespective of the preconditioner and the solvent. When treated for the same exposure time, specimens after 15% proanthocyanidins preconditioning resulted in the highest mean ultimate tensile strength compared with all the other groups tested. Five percent glutaraldehyde control group produced the highest cross-linking degree, but the ultimate tensile strength was lower than that of 15% proanthocyanidins group. The field emission scanning electron microscopy confirmed that the demineralized dentin collagen was in a homogeneous and regular arrangement after preconditioning and maintained expanding, regardless of the surface moisture conditions.

Fabrication of strontium-incorporated protein supramolecular nanofilm on titanium substrates for promoting osteogenesis.

The inherent biological inertness of Ti substrates is a general challenge in orthopedic and dental clinical application. In this study, the strontium-containing phase change lysozyme coating was prepared on titanium via a supramolecular self-assembly method for accelerating osseointegration. Successful preparation of the Sr-incorporated lysozyme nanofilm onto the Ti substrate (Ti-Ly-Sr) was proved by tests of scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Contact angle (CA). Furthermore, the results of cell morphology observation, cell viability assay, alkaline phosphatase staining and quantitative analysis showed that Ti-Ly-Sr substrate enhanced early adhesion, proliferation and osteogenic differentiation of bone marrow stromal cells (BMSCs). The quantitative real-time polymerase chain reaction (qRT-PCR) assays confirmed that Ti-Ly-Sr enhanced the expression of osteogenic related genes (BMP2, OPG, Runx2 and COL-1) of BMSCs at the molecular level. Moreover, Micro-CT and histological analysis proved that the strontium-incorporated lysozyme nanofilm modified Ti implants had significant capability of new bone formation in vivo after implantation for 4 weeks. We anticipate that the present system would provide a facile and effective means for surface modification of Ti-based implants. Relevant ideas and techniques in this study will contribute to the development of new implant devices.

Comparison and evaluation of the morphology of crowns generated by biogeneric design technique with CEREC chairside system.

OBJECTIVES: To better guide clinicians to choose the appropriate chairside system, we compared and evaluated the morphology of crowns generated by three different biogeneric design modes (biogeneric copy (BC), biogeneric individual (BI), and biogeneric reference (BR)) of the CEREC software. METHODS: Maxillary and mandibular casts were obtained from twelve volunteers and digital impressions were acquired. All ceramic crown preparations of all right maxillary central incisors were prepared and digital impressions were taken. Then, crowns were automatically designed under BC, BI and BR modes separately and their morphologies were evaluated by six doctors. The "optimal fitting alignment" and "3D analysis" functions of the Geomagic Qualify software were carried out between original teeth and auto-generated full crowns. The auto-generated crowns were modified by a technician according to clinical criteria and the adjustment time was recorded. The discrepancies between technician modified crowns and the auto-generated full crowns were evaluated with the same functions in the Geomagic Qualify software. RESULTS: The subjective evaluation results of BC group were significantly better than those of BI and BR group (p < 0.05). Compared with the original teeth and modified crowns, auto-generated crowns in BC group all had the smallest differences, followed by BR and BI group (p < 0.05). BC group needed the shortest adjustment time than BI and BR group (p < 0.05). CONCLUSIONS: Using crowns generated by BC mode is more aesthetic and suitable in clinics use than those generated by BI and BR modes and can reduce clinic adjustment time.

Microfluidic Chip for Odontoblasts in Vitro.

Odontoblast processes, which grow inside dentin tubules, are critical parts of odontoblasts, and they play an important role in dentin hypersensitivity. However, modeling the growth of odontoblast processes in vitro is difficult, which hinders the study of dentin hypersensitivity and other dental diseases. To our knowledge, no technique has yet been developed to induce the growth of odontoblast processes from a cell body in vitro. In the current study, we fabricated a microfluidic chip via soft lithography. The microchannels on the chip can mimic the microstructures of dentin tubules, and the microchambers that connect to the microchannels can be used for odontoblast culture. We successfully induced the growth of odontoblast processes from cell bodies by using this chip. In addition, we designed chips with different microchannel sizes (i.e., 2, 4, 6, and 8 µm) to investigate the relationship between the growth of odontoblast processes and the geometric constraint imposed by microchannels. Experimental results show that the growth of odontoblast processes can be successfully induced by 2 µm channels. However, odontoblasts will migrate in the 4, 6, and 8 µm channels. This finding indicates that 2 µm is the appropriate size for inducing the growth of odontoblast processes in vitro. This value is consistent with the size of dentin tubules in vivo. The fabricated microfluidic chip can serve as a powerful tool for investigating the physiology and pathology of odontoblast processes in the future and developing treatment solutions for dental diseases, such as dentin hypersensitivity.

In Vivo Rodent Models for Studying Dental Caries and Pulp Disease.

Dental caries is an infectious oral disease caused primarily by complex interactions of cariogenic oral flora (biofilm) with dietary carbohydrates on the tooth surface over time. Streptococcus mutans and Streptococcus sobrinus (S. mutans and S. sobrinus) are the most prevalent cariogenic species within the oral biofilm and considered the main etiological agents of caries. Pulp exposure and infection can be caused by trauma, carious lesion, and mechanical reasons. Pulp response to these exposures depends on the state of the pulp as well as the potential bacterial contamination of pulp tissue. Herein, we describe the process of using two in vivo rodent models to study the progression of dental caries and pulp disease: a nutritional microbial model and a pulp disease induction model. The progression of the carious lesion and pulpal infections in both models was assessed by micro-CT imaging and histomorphometric analysis. Moreover, the pulp disease induction models can be used to compare and assess the antibacterial and reparative properties of the different pulp capping materials.

Functional amyloid materials at surfaces/interfaces.

With the development of nanotechnology, functional amyloid materials are drawing increasing attention, and numerous remarkable applications are emerging. Amyloids, defined as a class of supramolecular assemblies of misfolded proteins or peptides into ß-sheet fibrils, have evolved in many new respects and offer abundant chemical/biological functions. These proteinaceous micro/nano-structures provide excellent biocompatibility, rich phase behaviours, strong mechanical properties, and stability at interfaces not only in nature but also in functional materials, displaying versatile interactions with surfaces/interfaces that have been widely adopted in bioadhesion, synthetic biology, and composites. Overall, functional amyloids at surfaces/interfaces have excellent potential applications in next-generation biotechnology and biomaterials.

Synthetic antigen-binding fragments (Fabs) against S. mutans and S. sobrinus inhibit caries formation.

Streptococcus mutans and Streptococcus sobrinus are the main causative agents of human dental caries. Current strategies for treating caries are costly and do not completely eradicate them completely. Passive immunization using nonhuman antibodies against Streptococcal surface antigens has shown success in human trials, however they often invoke immune reactions. We used phage display to generate human antigen-binding fragments (Fabs) against S. mutans and S. sobrinus. These Fabs were readily expressed in E. coli and bound to the surface S. mutans and S. sobrinus. Fabs inhibited sucrose-induced S. mutans and S. sobrinus biofilm formation in vitro and a combination of S. mutans and S. sobrinus Fabs prevented dental caries formation in a rat caries model. These results demonstrated that S. mutans and S. sobrinus Fabs could be used in passive immunization strategies to prevent dental caries. In the future, this strategy may be applied towards a caries therapy, whereby Fabs are topically applied to the tooth surface.

One-Step Assembly of a Biomimetic Biopolymer Coating for Particle Surface Engineering.

Advances in material design and applications are highly dependent on the development of particle surface engineering strategies. However, few universal methods can functionalize particles of different compositions, sizes, shapes, and structures. The amyloid-like lysozyme assembly-mediated surface functionalization of inorganic, polymeric or metal micro/nanoparticles in a unique amyloid-like phase-transition buffer containing lysozyme are described. The rapid formation of a robust nanoscale phase-transitioned lysozyme (PTL) coating on the particle surfaces presents strong interfacial binding to resist mechanical and chemical peeling under harsh conditions and versatile surface functional groups to support various sequential surface chemical derivatizations, such as radical living graft polymerization, the electroless deposition of metals, biomineralization, and the facile synthesis of Janus particles and metal/protein capsules. Being distinct from other methods, the preparation of this pure protein coating under biocompatible conditions (e.g., neutral pH and nontoxic reagents) provides a reliable opportunity to directly modify living cell surfaces without affecting their biological activity. The PTL coating arms yeasts with a functional shell to protect their adhered body against foreign enzymatic digestion. The PTL coating further supports the surface immobilization of living yeasts for heterogeneous microbial reactions and the sequential surface chemical derivatization of the cell surfaces, e.g., radical living graft polymerization.

Enzymatic Hydrophobic Modification of Jute Fibers via Grafting to Reinforce Composites.

Horseradish peroxidase (HRP)/H2O2 system catalyzes the free-radical polymerization of aromatic compounds such as lignins and gallate esters. In this work, dodecyl gallate (DG) was grafted onto the surfaces of lignin-rich jute fabrics by HRP-mediated oxidative polymerization with an aim to enhance the hydrophobicity of the fibers. The DG-grafted jute fibers and reaction products of their model compounds were characterized by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The results clearly indicated the grafting of DG to the jute fiber by HRP. Furthermore, the hydrophobicity of jute fabrics was determined by measuring the wetting time and static contact angle. Compared to the control sample, the wetting time and static contact angle of the grated fabrics changed from ~1 s to 1 h and from ~0° to 123.68°, respectively. This clearly proved that the hydrophobicity of jute fabrics improved considerably. Conditions of the HRP-catalyzed DG-grafting reactions were optimized in terms of the DG content of modified jute fabrics. Moreover, the results of breaking strength and elongation of DG-grafted jute/polypropylene (PP) composites demonstrated improved reinforcement of the composite due to enzymatic hydrophobic modification of jute fibers.

Anti-proteolytic capacity and bonding durability of proanthocyanidin-biomodified demineralized dentin matrix.

Our previous studies showed that biomodification of demineralized dentin collagen with proanthocyanidin (PA) for a clinically practical duration improves the mechanical properties of the dentin matrix and the immediate resin-dentin bond strength. The present study sought to evaluate the ability of PA biomodification to reduce collagenase-induced biodegradation of demineralized dentin matrix and dentin/adhesive interfaces in a clinically relevant manner. The effects of collagenolytic and gelatinolytic activity on PA-biomodified demineralized dentin matrix were analysed by hydroxyproline assay and gelatin zymography. Then, resin-/dentin-bonded specimens were prepared and challenged with bacterial collagenases. Dentin treated with 2% chlorhexidine and untreated dentin were used as a positive and negative control, respectively. Collagen biodegradation, the microtensile bond strengths of bonded specimens and the micromorphologies of the fractured interfaces were assessed. The results revealed that both collagenolytic and gelatinolytic activity on demineralized dentin were notably inhibited in the PA-biomodified groups, irrespective of PA concentration and biomodification duration. When challenged with exogenous collagenases, PA-biomodified bonded specimens exhibited significantly less biodegradation and maintained higher bond strengths than the untreated control. These results suggest that PA biomodification was effective at inhibiting proteolytic activity on demineralized dentin matrix and at stabilizing the adhesive/dentin interface against enzymatic degradation, is a new concept that has the potential to improve bonding durability.

[Effect of casein phosphopeptide-amorphous calcium phosphate on the stability of resin-dentin bonds against pH cycling].

OBJECTIVE: To investigate the effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on the stability of resin-dentin bonds against pH cycling. METHODS: Resin-bonded dentin specimens were prepared following manufacturers' instructions, and randomly divided into 3 groups. Among them, 2 groups experienced pH cycling, in which specimens applied CPP-ACP or distilled and deionized water (DDW) on the bonding interface, respectively. Microtensile bond strength (muTBS) testing, failure mode analysis, micromorphological and nanoleakage evaluation of bonding interface and elemental analysis within hybrid layer were performed after 15 days pH cycling. The other group was tested immediately after specimens' preparation without pH cycling. RESULTS: No significant differences were found in muTBS between no pH cycling and pH cycling/CPP-ACP group. Their muTBS were both significantly higher than that of pH cycling/DDW group (P < 0.05). Mixed fractures were the most prevalent failure mode. The quality of hybrid layer in pH cycling/CPP-ACP group was better than that of pH cycling/DDW group, and the nanoleakage was also less severe. Comparing with pH cycling/DDW group, the atomic percentages of Ca in the other two groups were both significantly higher, while those of Ag were statistically lower (P < 0.05). CONCLUSION: Local application of CPP-ACP can promote the stability of resin-dentin bonding interface against pH cycling and prolong bonding degeneration.

The role of grape seed extract in the remineralization of demineralized dentine: micromorphological and physical analyses.

OBJECTIVES: Grape seed extract (GSE) is known to have a positive effect on the demineralization and/or remineralization of artificial root caries lesions. The present study aimed to investigate whether biomodification of caries-like acid-etched demineralized dentine, using proanthocyanidins-rich GSE, would promote its remineralization potential. DESIGNS: Dentine specimens were acid-etched for 30s, then biomodified using proanthocyanidin-based preconditioners (at different concentrations and pH values) for 2min, followed by a 15-day artificial remineralization regimen. They were subsequently subjected to microhardness measurements, micromorphological evaluation and X-ray diffraction analyses. Stability of the preconditioners was also analyzed, spectrophotometrically. RESULTS: A concentration-dependent increase was observed in the microhardness of the specimens that were biomodified using GSE preconditioners, without pH adjustment. Field emission scanning electron microscopy revealed greater mineral deposition on their surfaces, which was further identified mainly as hydroxylapatite. The absorbances of preconditioner dilutions at pH 7.4 and pH 10.0 decreased at the two typical polyphenol bands. CONCLUSIONS: Transient GSE biomodification promoted remineralization on the surface of demineralized dentine, and this process was influenced by the concentration and pH value of the preconditioner. GSE preconditioner at a concentration of 15%, without pH adjustment, presented with the best results, and this may be attributed to its high polyphenolic content.

Biomodification to dentin by a natural crosslinker improved the resin-dentin bonds.

OBJECTIVES: Transient collagen cross-linking treatment by proanthocyanidins (PA), a natural crosslinker, was proved to increase the cross-linking degree and ultimate tensile strength of demineralised dentin. The present study aimed to investigate whether transient pretreatment by PA-based preconditioner can improve the resin-dentin bonds of various etch and rinse adhesives. The influence of solvent type, PA concentration and treatment duration were examined. METHODS: PA-based preconditioners were prepared by adding powdered grape seed extract, rich in PA, to various solvents at different concentrations. They were used on demineralised dentin before the application of the bonding agent. Bond strength, failure modes and degree of conversion were evaluated via microtensile testing, field emission scanning electron microscopy and Fourier transform infrared spectroscopy, respectively. RESULTS: Collagen cross-linking treatment by PA-based preconditioners presented a concentration- and time-dependent increase in dentin bond strength even in reduced, clinically applicable treatment duration. PA preconditioning improved bond strength of the tested water/ethanol-based adhesive better than the water/acetone-based system. Mixed fracture was the most prevalent failure mode happened on the top of the hybrid layer in PA-pretreated specimens, whilst at the bottom in non-treated controls. The degree of conversion was not significantly affected by PA pretreatment. CONCLUSIONS: Transient PA preconditioning improved resin-dentin bonds without compromise on the curing behaviours of the tested adhesives.

[The potential effect of proanthocyanidins on the stability of resin-dentin bonds against thermal cycling].

OBJECTIVE: To investigate the potential effect of proanthocyanidins (PA), a natural cross-linker, on the stability of resin-dentin bonds against thermal cycling. METHODS: Ten percent, 15% PA-based preconditioners, and 5% glutaraldehyde were prepared for the transient pretreatment of demineralized dentin before bonding. Specimens without pretreatment were used as negative controls (n = 4 teeth for each group). Microtensile bond strength, failure mode, micromorphologies of resin-dentin interface and the collagen degradation of bonded specimens after thermal cycling were evaluated. RESULTS: After thermal cycling, the microtensile bond strength values of resin-dentin bond in groups pretreated with 15% PA for 120 s and 60 s [(23.09 ± 3.19) and (21.88 ± 3.49) MPa] were significantly higher than that in control group [(15.47 ± 3.78) MPa] (P < 0.05). Mixed fractures were the most prevalent failure mode. Specimens with pretreatment presented compact hybrid layer, while some narrow gaps were found in hybrid layer of non-treated specimens. Collagen biodegradation rates in groups with pretreatment were significantly lower than that in control group (P < 0.05). Among them, specimens pretreated by 15% PA preconditioner for 120 s exhibited the lowest biodegradation rates [(0.316 ± 0.019) mg/g]. CONCLUSIONS: The application of natural cross-linker PA on demineralized dentin reduced the bond degradation against aging by thermal cycling, and can be helpful to create more durable bonds to dentin.