Medical students' intention to integrate digital health into their medical practice: A pre-peri COVID-19 survey study in Canada.

Objective: We aimed to explore the factors that influence medical students' intention to integrate dHealth technologies in their practice and analyze the influence of the COVID-19 pandemic on their perceptions and intention. Methods: We conducted a two-phased survey study at the University of Montreal's medical school in Canada. The study population consisted of 1367 medical students. The survey questionnaire was administered in two phases, that is, an initial survey (t0) in February 2020, before the Covid-19 pandemic, and a replication survey (t1) in January 2021, during the pandemic. Component-based structural equation modeling (SEM) was used to test seven research hypotheses. Results: A total of 184 students responded to the survey at t0 (13%), whereas 138 responded to the survey at t1 (10%). Findings reveal that students, especially those who are in their preclinical years, had little occasion to experiment with dHealth technologies during their degree. This lack of exposure may explain why a vast majority felt that dHealth should be integrated into medical education. Most respondents declared an intention to integrate dHealth, including AI-based tools, into their future medical practice. One of the most salient differences observed between t0 and t1 brings telemedicine to the forefront of medical education. SEM results confirm the explanatory power of the proposed research model. Conclusions: The present study unveils the specific dHealth technologies that could be integrated into existing medical curricula. Formal training would increase students' competencies with these technologies which, in turn, could ease their adoption and effective use in their practice.

Dentin interaction with universal adhesive containing isopropanol solvent studied by solid-state NMR spectroscopy.

OBJECTIVE: This study investigated the chemical and structural changes in the mineral phase and collagen of dentin during application of a mild universal adhesive. Particular attention was paid to the role of isopropanol and changes in water molecules. METHODS: In vitro application of the mild universal adhesive on dentin with two established etching modes (self-etch and etch-and-rinse) was studied using solid state nuclear magnetic resonance spectroscopy. RESULTS: It was evidenced that the etch-and-rinse mode leads to a decrease of the inorganic apatite and a reorganization of the residual mineral phase with a low amount of adhesive phosphate monoesters calcium salt formed, compared to the self-etch mode. In contrast, the adhesive interacts very similarly to the level of dentin collagen in both protocols, with a strong decrease in the amount of the free water molecules induced by the presence of isopropanol as the adhesive solvent, but without significant changes in the initial collagen structure. For both modes, the adhesive acrylates monomers remain mobile and can infiltrate the collagen. SIGNIFICANCE: Understanding the molecular interactions between dentin and adhesive solutions is a major challenge for designing products that lead to the formation of ideal dentin resin hybrid layer. Notably, one point considered essential is the presence of unbound water which, over time, is associated with a hydrolytic degradation of the organic matrix. Isopropanol, as an adhesive solvent, leads to a decrease in the amount of the less stable water molecules while the water molecules strongly attached to the collagen are retained, thus preserving the collagen structure.

Characterization of hydrogenated dentin components by advanced 1H solid-state NMR experiments.

Collecting information about molecular organisation on biological materials such as bone and dentin represents a major challenge in attaining a better understanding of their mechanical properties. To that end, solid state Nuclear Magnetic Resonance (ssNMR) spectroscopic study is an appropriate strategy to provide atomic structural details on these amorphous composite materials. However, species like water molecules and hydroxyl groups are usually observed through 1H magic angle spinning (MAS) ssNMR that suffers from poor resolution due to strong signal overlapping, making their identification difficult. This paper proposes a set of ssNMR experiments for 1H characterization of the main components of human dentin, based on homo- and hetero-nuclear dipolar couplings and composed mostly of fast 1D experiments. The 1H assignment is assisted by straightforward sample modifications: vacuum drying, deuterium exchange and demineralization. These experiments allow the hydrogen signal edition of dentin species like water molecules, HPO42- and OH- groups, depending on their localization (bound to the organic phase, linked to apatite or at the interface) and their dynamic behaviour. This ssNMR toolbox has the potential to provide important structural and dynamic information on chemical and physical modifications of biomaterials. STATEMENT OF SIGNIFICANCE: Molecular characterisation of apatitic biomaterials by biophysical techniques is extremely difficult due to their complex and amorphous nature. It is, however, crucial to obtain such information if we want to understand their mechanical properties in relation to their physical state, for example their hydration levels. In this article we used a set of solid state NMR experiments and sample modifications to distinguish 1H signal of human dentin components with a particular attention to water molecules, known for their major role in biomaterial structuring.

Educators and practitioners' perspectives in the development of a learning by concordance tool for medical clerkship in the context of the COVID pandemic.

BACKGROUND: The COVID-19 pandemic has forced medical schools to create educational material to palliate the anticipated and observed decrease in clinical experiences during clerkships. An online learning by concordance (LbC) tool was developed to overcome the limitation of students' experiences with clinical cases. However, knowledge about the instructional design of an LbC tool is scarce, especially the perspectives of collaborators involved in its design: 1- educators who wrote the vignettes' questions and 2- practitioners who constitute the reference panel by answering the LbC questions. The aim of this study was to describe the key elements that supported the pedagogical design of an LbC tool from the perspectives of educators and practitioners. METHODS: A descriptive qualitative research design has been used. Online questionnaires were used, and descriptive analysis was conducted. RESULTS: Six educators and 19 practitioners participated in the study. Important to the educators in designing the LbC tool were prevalent or high-stake situations, theoretical knowledge, professional situations experienced and perceived difficulties among students, and that the previous workshop promoted peer discussion and helped solidify the writing process. Important for practitioners was standards of practice and consensus among experts. However, they were uncertain of the educational value of their feedback, considering the ambiguity of the situations included in the LbC tool. CONCLUSIONS: The LbC tool is a relatively new training tool in medical education. Further research is needed to refine our understanding of the design of such a tool and ensure its content validity to meet the pedagogical objectives of the clerkship.

CONTEXTE: Face à la pandémie de la COVID-19, les facultés de médecine ont été contraintes à créer du matériel pédagogique pouvant pallier la diminution prévue et avérée de l'exposition clinique pendant les stages d'externat. Un outil numérique de formation par concordance (FpC) a été développé pour combler le manque d'exposition à des cas cliniques. Cependant, les connaissances sur la conception pédagogique des outils de FpC sont limitées, en particulier en ce qui concerne les perspectives des collaborateurs participant à leur réalisation : 1 ­ les éducateurs qui rédigent les questions des vignettes et 2 ­ les praticiens composant le groupe d'experts qui fournissent les réponses de référence aux questions de FpC. L'objectif de cette étude était de décrire les éléments clés qui ont étayé la conception pédagogique d'un outil FpC du point de vue des éducateurs et des praticiens. MÉTHODES: Il s'agit d'une recherche qualitative de type descriptif, pour laquelle on s'est servi de questionnaires en ligne et d'une méthode d'analyse descriptive. RÉSULTATS: Six éducateurs et 19 praticiens ont participé à l'étude. Dans la conception de l'outil FpC, les éducateurs ont attribué une importance particulière aux situations courantes ou à enjeu élevé, aux connaissances théoriques, aux situations professionnelles vécues par les étudiants et aux difficultés qu'ils ont perçues chez eux. Ils ont également tenu à faire en sorte que l'atelier qui précédait la conception favorise le débat entre pairs et contribue à solidifier le processus de rédaction. Les praticiens ont privilégié les normes de pratique et l'existence d'un consensus entre experts. Cependant, ils doutaient de la valeur pédagogique de leurs commentaires, compte tenu de l'ambiguïté des situations décrites dans l'outil FpC. CONCLUSIONS: Les outils FpC sont relativement nouveaux en éducation médicale. Des recherches plus poussées sont nécessaires pour affiner notre compréhension de la conception d'un tel outil et pour nous assurer de sa validité de contenu, pour bien répondre aux objectifs pédagogiques de l'externat.

Investigation of ethanol infiltration into demineralized dentin collagen fibrils using molecular dynamics simulations.

The purpose of this study is to investigate the interaction of neat ethanol with bound and non-bound water in completely demineralized dentin that is fully hydrated, using molecular dynamics (MD) simulation method. The key to creating ideal resin-dentin bonds is the removal of residual free water layers and its replacement by ethanol solvent in which resin monomers are soluble, using the ethanol wet-bonding technique. The test null hypotheses were that ethanol cannot remove any collagen-bound water, and that ethanol cannot infiltrate into the spacing between collagen triple helix due to narrow interlayer spacing. Collagen fibrillar structures of overlap and gap regions were constructed by aligning the collagen triple helix of infinite length in hexagonal packing. Three layers of the water molecules were specified as the layers of 0.15-0.22nm, 0.22-0.43nm and 0.43-0.63nm from collagen atoms by investigating the water distribution surrounding collagen molecules. Our simulation results show that ethanol molecules infiltrated into the intermolecular spacing in the gap region, which increased due to the lateral shrinkage of the collagen structures in contact with ethanol solution, while there was no ethanol infiltration observed in the overlap region. Infiltrated ethanol molecules in the gap region removed residual water molecules via modifying mostly the third water layer (50% decrease), which would be considered as a loosely-bound water layer. The first and second hydration layers, which would be considered as tightly bound water layers, were not removed by the ethanol molecules, thus maintaining the helical structures of the collagen molecules.

Water distribution in dentin matrices: bound vs. unbound water.

OBJECTIVE: This work measured the amount of bound versus unbound water in completely-demineralized dentin. METHODS: Dentin beams prepared from extracted human teeth were completely demineralized, rinsed and dried to constant mass. They were rehydrated in 41% relative humidity (RH), while gravimetrically measuring their mass increase until the first plateau was reached at 0.064 (vacuum) or 0.116 gH2O/g dry mass (Drierite). The specimens were then exposed to 60% RH until attaining the second plateau at 0.220 (vacuum) or 0.191 gH2O/g dry mass (Drierite), and subsequently exposed to 99% RH until attaining the third plateau at 0.493 (vacuum) or 0.401 gH2O/g dry mass (Drierite). RESULTS: Exposure of the first layer of bound water to 0% RH for 5 min produced a -0.3% loss of bound water; in the second layer of bound water it caused a -3.3% loss of bound water; in the third layer it caused a -6% loss of bound water. Immersion in 100% ethanol or acetone for 5 min produced a 2.8 and 1.9% loss of bound water from the first layer, respectively; it caused a -4 and -7% loss of bound water in the second layer, respectively; and a -17 and -23% loss of bound water in the third layer. Bound water represented 21-25% of total dentin water. Chemical dehydration of water-saturated dentin with ethanol/acetone for 1 min only removed between 25 and 35% of unbound water, respectively. SIGNIFICANCE: Attempts to remove bound water by evaporation were not very successful. Chemical dehydration with 100% acetone was more successful than 100% ethanol especially the third layer of bound water. Since unbound water represents between 75 and 79% of total matrix water, the more such water can be removed, the more resin can be infiltrated.

Fluid flow through dentin-self-etch resin interface during long term in vitro aging.

This work aimed at characterizing the interface between dentin and the resin-infiltrated dentin made following the etching procedure that prepares for the bonding of tooth-colored restorations. The non-destructive measurement of fluid flow through the dentin-self-etch resin interface was followed repeatedly during a two year aging period. Two self-etch adhesive systems were selected for experiments on the evolution of permeability and evaluation of infrared spectral changes following the 24 month aging period. The adhesives contained water and a co-solvent, namely acetone for iBond, and t-butanol for Xeno V. For both adhesive systems, the permeability decreased during the first 3 months after etching, reaching values of -66.9 and -70.5% for iBond and Xeno V, respectively. Afterwards, the fluid flow slowly increased but still remained below 50% of the initial value following the 2-year aging period. The slow degradation of the resin-dentin interface, attributed to water impregnated collagen hydrolysis, is evidenced by these variations in fluid flow, and is also noted by the increase in water-related infrared absorption bands at 3300 cm(-1) and at 1600 cm(-1). The results are discussed in terms of co-solvent hydrophobicity, evaporation rate and viscosity together with resin infiltration depth and affinity for water.

Depletion of water molecules during ethanol wet-bonding with etch and rinse dental adhesives.

The treatment of demineralized dentin with ethanol has been proposed as a way to improve hydrophobic monomer penetration into otherwise water saturated collagen fibrils. The ethanol rinse is expected to preserve the fibrils from collapsing while optimizing resin constituent infiltration for better long term adhesion. The physico-chemical investigations of demineralized dentin confirmed objectively these working hypotheses. Namely, Differential Scanning Calorimetry (DSC) measurements of the melting point of water molecules pointed to the presence of free and bound water states. Unfreezable water was the main type of water remaining following a rinsing step with absolute ethanol. Two different liquid water phases were also observed by Magic Angle Spinning (MAS) solid state Nuclear magnetic Resonance (NMR) spectroscopy. Infrared spectra of ethanol treated specimens illustrated differences with the fully hydrated specimens concerning the polar carbonyl vibrations. Optical microscopy observations as well as scanning electron microscopy showed an improved dentin-adhesive interface with ethanol wet bonding. The results indicate that water can be confined to strongly bound structural molecules when excess water is removed with ethanol prior to adhesive application. This should preserve collagen from hydrolysis upon aging of the hybrid layer.

Critical surface energy of composite cement containing MDP (10-methacryloyloxydecyl dihydrogen phosphate) and chemical bonding to hydroxyapatite.

Self-adhesive composite cements are increasingly used for cementing inlays/onlays, intraradicular posts, crowns and laminate veneers. Wider clinical acceptance is driven by simpler and faster handling procedures, much like observed for self-etching adhesives. 10-Methacryloyloxydecyl dihydrogen phosphate (MDP) is a bi-functional monomer incorporated as the reactive ingredient in a contemporary self-adhesive cement. We have examined the surface free energy parameters of this cement and studied the mode of action of the cement on dentine substrate by contact angle measurements to determine the critical surface energy of the cement. Retention of the infrared absorption bands characteristic of the acrylate moieties on the surface of hydroxyapatite particles suggests that MDP contributes to the overall bonding to dentine by forming ionic chemical bonds with surface calcium ions in dentine crystalites.

Solvent composition of one-step self-etch adhesives and dentine wettability.

OBJECTIVES: Our aim was to determine the wettability of dentine by four commercial self-etch adhesives and evaluate their spreading rate on the dentine surface. Any correlation with chemical composition was sought, particularly with the amount of solvent or HEMA present in the adhesive. The adhesives used were AdheSE One, Optibond All.In.One, Adper Easy Bond and XenoV. METHODS: Chemical compositions were determined by proton nuclear magnetic resonance (NMR) spectroscopy of the adhesives dissolved in dimethylsulfoxide. Apparent contact angles for sessile drops of adhesives were measured on dentine slices as a function of time for up to 180s. The water contact angles were determined for fully polymerised adhesives. RESULTS: All adhesives were water-based with total solvent contents ranging from 27% to 73% for HEMA-free adhesives, and averaging 45% for HEMA containing adhesives. The contents in hydrophobic groups decreased as water contents increased. No differences were found in the adhesive contact angles after 180s even though the spreading rates were different for the products tested. CONCLUSION: Water contact angles differed significantly but were not correlated with HEMA or solvent presence. Manufacturers use different approaches to stabilise acid co-monomer ingredients in self-etch adhesives. Co-solvents, HEMA, or acrylamides without co-solvents are used to simultaneously etch and infiltrate dentine. A large proportion of water is necessary for decalcification action.

Modifications of the organic and mineral fractions of dental tissues following conditioning by self-etching adhesives.

OBJECTIVES: Our objective was to analyse the acid strengths and concentrations in contemporary self-etch adhesives and test whether the adhesion/decalcification concept functions the same way for all products. METHODS: The self-etching adhesives were dissolved in a 50% water-ethanol solvent, these were reacted with biological apatite (HA) in the form of powder of human dentine in order to quantify calcium release and study the reaction products as a function of acid strengths and concentrations. The four self-etching adhesives investigated were AdheSE One (Ivoclar Vivadent, Schaan, Liechtenstein), Adper Easy Bond (3M ESPE, St Paul, MN, USA), Optibond All-In-One (KERR, Orange, CA, USA), Xeno V (Dentsply De Trey, Konstanz, Germany). RESULTS: Acid concentrations were found to span the range from 1 to 2 mmol/l, and the acid dissociation constants varied between apparent pKa values of 3.4 and 4.2. The pH values changed with time from values near 2.8 to 3.6, confirming the buffering action of HA. The stronger acids dissolved more calcium ions but left less organic matter attached to the tissue particles. Thermogravimetric and infrared analysis demonstrated that the weaker acids tended to bind to HA surfaces and increased significantly the organic to mineral ratios of the powders. CONCLUSION: Self-etching adhesives can be differentiated and classified in two types: weak acids attach to the mineral phase and leach little calcium; strong acids bind to the calcium ions, demineralize more and tend to debond from the dentinal hard tissues by forming more soluble calcium salts.

Water permeability, hybrid layer long-term integrity and reaction mechanism of a two-step adhesive system.

OBJECTIVES: Our aim was to investigate the reaction mechanism of formation of the hybrid layer by a HEMA-containing self-etch adhesive and to study fluid filtration, contact angle and interfacial ultrastructure by SEM following a 1 year ageing period. METHODS: Acidic behaviour and chemical interactions between Silorane System Adhesive and dentine were studied by potentiometric titrations, atomic absorption spectroscopy and infrared spectroscopy. The hydrophilicity of the adhesive was evaluated using the sessile drop method and dentine permeability by hydraulic conductance. The morphological study of the dentine/adhesive system interface was conducted using SEM. RESULTS: The Silorane System Adhesive behaved as a multi-acid with several different pK(a) values. When the adhesive was in contact with dentine, the acid was progressively consumed and calcium ions were released. The acrylate substituted phosphonate bound strongly to apatite crystals. The polyacrylic acid copolymer reacted with calcium ions and formed an interpenetrating polymer network (IPN). Water contact angle measurements showed rapid spreading on primer (angles reached 15 degrees at 30s) and larger contact angles when the Silorane bonding layer was added (from over 60 degrees to 44 degrees ). A thick, homogeneous hybrid layer was observed both initially and after 1 year of ageing, with a corresponding hydraulic conductance of -48.50% initially and -52.07% at 12 months. CONCLUSION: The Silorane System Adhesive is capable of both dissolving calcium ions and binding to apatite surfaces. The results showed the hydrophilicity of the adhesive, which formed an IPN-like hybrid layer that conserved adequate impermeability over a 1-year period.

HEMA reactivity with demineralized dentin.

OBJECTIVES: 2-Hydroxyethylmethacrylate (HEMA) was compared to its epoxy analogue, glycidoxypropylmethacrylate (GMA), for reactivity with 2,6-diaminohexanoic acid (Lysine), an amino acid present in collagen possessing a reactive amino side chain. The aim was to verify whether HEMA could chemically react with collagen fibers. METHODS: Capillary electrophoresis was used to analyse reaction products together with computer aided chemistry. Retention of HEMA in demineralized dentine particles was investigated by infrared spectroscopy. RESULTS: It was found by that HEMA does not form any new molecular species when contacted with lysine whereas GMA completely reacts to form the expected addition product. Computer aided chemistry confirmed this finding. Infrared spectroscopy showed that demineralized dentin has strong affinity for HEMA and retains this monomer despite extensive water washing. CONCLUSIONS: We interpret this behavior as demonstrating solvation of HEMA in the collagen polymer network.

Effects of dentine moisture on the permeability of total-etch and one-step self-etch adhesives.

OBJECTIVES: The aim of this study was to compare the technique sensitivity of a one-bottle total-etch adhesive and a self-etch primer adhesive to the moisture condition of the dentine substrate. METHODS: The methods used were hydraulic conductance, light microscopy and scanning electron microscopy. RESULTS: When the moisture conditions of the dentine surface are modified with respect to the standard, the bonded interfaces obtained with the one-bottle total-etch Adper Scotch Bond 1 XT (SB) and the all-in-one self-etch Adper Prompt L-Pop (AP) are morphologically highly perturbed. But, although this study also showed a significant (p<0.01) relationship between increases in permeability of resin-bonded dentine and variations of dentine moisture conditions with SB, a significant relationship was found only for the influence of the over-wet condition with AP. CONCLUSION: Within the limitations of this study, the self-etch primer tested gave a greater reduction in dentine permeability than the one-bottle adhesive, while being more tolerant to handling. Although excess water should be avoided with both these systems, air-drying can be an alternative to wet-bonding with the self-etch primers, thus reducing the sensitivity to technique.

Does strontium play a role in the cariostatic activity of glass ionomer? Strontium diffusion and antibacterial activity.

OBJECTIVES: The aim of this work was to evaluate the activity of strontium ions on the main pathogens of the oral flora. The leaching of strontium from resin modified glass ionomer cements (RMGIC) was evaluated together with its uptake by superficial dental enamel. METHODS: The antibacterial activity was measured by the growth inhibition method following exposure of supra- and sub-gingival bacteria to a range of strontium concentrations (0.19 moll(-1), 0.37 moll(-1), 0.74 moll(-1) and 1.11 moll(-1)). Strontium concentrations were analyzed chemically and migration at 5 microm and 15 microm depths was quantified by microprobe following Fuji Ortho LC application on the vestibular enamel of extracted teeth. RESULTS: Strontium was found in appreciable amounts (0.8 wt.%) in superficial enamel, but in insignificant concentrations deeper in. At the same time, 8% fluoroapatite was formed in the enamel. Under our experimental conditions, strontium had no significant antibacterial activity; only one log reduction of activity was observed at the highest concentrations tested. CONCLUSIONS: RMGIC releases strontium ions which are rapidly exchanged for calcium ions in the superficial enamel. No significant antibacterial activity was observed for strontium ions alone at the concentrations considered. However synergistic effects with fluoride could promote antibacterial activity.

Morphological study of fiber-reinforced post-bonding system-root dentin interface by evaluation of two bonding systems.

UNLABELLED: Morphological study of fiber post/bonding system/root dentin interface by evaluation of two bonding systems. OBJECTIVES: The aim of the study was to analyze the interfaces, and thus the seal, between root dentin and bonded fiber-reinforced posts. The interfaces were obtained by applying two enamel-dentin adhesive systems, a one-bottle system used after application of phosphoric acid and a self-etch system, both used with an adhesive cement. The interface was evaluated by SEM observation of the continuity of the hybrid layer and the morphology of the resin tags, in terms of length, density and presence of side branches, at the interface between the fiber-reinforced post, the bonding system and the root dentin. METHODS: Twenty-six anterior single-rooted teeth extracted for periodontal reasons were treated endodontically and then randomly separated into two groups of 13 teeth each: group 1: Excite DSC (Ivoclar Vivadent, Liechtenstein); group 2: AdheSE DC (Ivoclar Vivadent, Schaan, Liechtenstein). After preparation of the root canal and application of the adhesive, each specimen received a Postec translucent FRC post (Ivoclar Vivadent, Schaan, Liechtenstein) that was cemented in with Variolink II dual-curing luting composite (Ivoclar Vivadent, Schaan, Liechtenstein). The specimens were then prepared for SEM observation of the continuity of the hybrid layer and scoring of the morphology of the resin tags in each third of the root (at 1, 4.5 and 8mm from the coronal surface). RESULTS: There was no significant difference (at p<0.05) between the two groups in terms of continuity of the hybrid layer or morphology of the resin tags. The hybrid layer was present, unbroken and uniform in both the group where adhesive was used with a phosphoric acid total etch and the self-etch system group. Whatever the bonding system, the resin tags had side branches, and greater length and density in the cervical third than in the middle or apical thirds. Bubbles were found in the cement layer in most of the specimens. CONCLUSIONS: The one-bottle and self-etch bonding systems gave similar results in terms of interface morphology when a translucent fiber-reinforced post was cemented into the endodontically prepared roots.

Acrylophosphonic acid reactivity with calcium ions and biological apatite.

OBJECTIVES: Acrylophosphonic acid (H(2)L) was reacted with biological apatite originating from dental enamel powder in order to identify and study the reaction products formed during the use of self-etch monomers. Nuclear magnetic resonance spectroscopy (NMR) showed the formation of brushite and a calcium salt of acrylophosphonic acid. This Ca salt was further synthesized and characterized by NMR, Fourier transform-infrared (FT-IR) and chromatography coupled with potentiometric analysis. The results reveal that calcium ions form a compound with two mono-deprotonated acrylophosphonate anions at physiological pH values. Thus, dissolution of the biological apatite by the acid-etch releases phosphate and calcium ions that combine to form brushite. The remaining dissolved Ca neutralize the acrylophosphonic acid to form an ionic salt of formula Ca(HL)(2). SIGNIFICANCE: The stoichiometry of this calcium salt allows us to conclude that, following a self-etch procedure, dissolved Ca ions participate in the formation of crosslinks in the complex photopolymerized copolymer composite network of the hybrid layer.