Numerical and experimental study of echogenicity in 3D-printed tissue-mimicking materials.

The main focus of this work is the echogenicity of a 3D-printed synthetic composite material that mimics the acoustic properties of cardiac biological tissues to provide ultrasound images similar to those obtained during interventional cardiology procedures. The 3D-printed material studied is a polymer-based composite with a matrix-inclusion microstructure, which plays a critical role in ultrasound response due to ultrasound-microstructure interaction at the involved medical echography wavelengths. Both numerical simulations and experimental observations are carried out to quantitatively establish the relationship between the 3D-printed microstructure and its ultrasonic echogenicity, considering different microstructure characteristics, namely area fraction and size of the inclusion, and its actual printed shape.

A parametrical finite element analysis for functionally graded material overlay restoration.

The main cause of failure in bonded ceramic restorations is material fracture due to excessive stress concentration at the base of the prosthesis. The design of restorative functionally graded materials (FGM) could represent a major advance in dissipating mechanical stresses during occlusal contacts. The aim of this paper is to carry out a complete factorial design of finite element analyses to optimize a multilayer FGM introduced at the bottom of an overlay prosthesis.

Debonding of coin-shaped osseointegrated implants: Coupling of experimental and numerical approaches.

While cementless implants are now widely used clinically, implant debonding still occur and is difficult to anticipate. Assessing the biomechanical strength of the bone-implant interface can help improving the understanding of osseointegration phenomena and thus preventing surgical failures. A dedicated and standardized implant model was considered.

Use of Dental Defects Associated with Low-Dose di(2-Ethylhexyl)Phthalate as an Early Marker of Exposure to Environmental Toxicants.

Background: Markers of exposure to environmental toxicants are urgently needed. Tooth enamel, with its unique properties, is able to record certain environmental conditions during its formation. Enamel formation and quality are dependent on hormonal regulation and environmental conditions, including exposure to endocrine disrupting chemicals (EDCs).

The role of lateral branches on effective stiffness and local overstresses in dentin.

The 3D microstructure of dentinal tissue, the main tissue of the tooth, is the subject of an increasingly comprehensive body of knowledge. The relationship between this microstructure and the mechanical behaviour of dentinal tissue remains, nonetheless, under question. This article proposes an original SEM analysis of dentin microstructure, accounting for lateral branches, and a mechanical model based on these findings.

3D-printed protected face shields for health care workers in Covid-19 pandemic.

The coronavirus pandemic resulted in a shortage of protective equipment. To meet the request of eye-protecting devices, an interdisciplinary consortium involving practitioners, researchers, engineers and technicians developed and manufactured thousands of inexpensive 3D-printed face shields, inside hospital setting. This action leads to the concept of "concurrent, agile, and rapid engineering".

Strategies to optimize bonding of adhesive materials to molar-incisor hypomineralization-affected enamel: A systematic review.

Background: Children with first permanent molar affected by molar-incisor hypomineralization (MIH) show high treatment failure rate.

Aim: To conduct a systematic review on bonding of adhesive materials to MIH-affected enamel, so as to identify all the methods suggested to optimize it and to determine the best bonding protocol(s).

Design: An exhaustive literature search was conducted on MEDLINE/PubMed, the Cochrane Library, and Web of Science databases, up to October 2018.

Assessment of the interplay between scaffold geometry, induced shear stresses, and cell proliferation within a packed bed perfusion bioreactor.

By favoring cell proliferation and differentiation, perfusion bioreactors proved efficient at optimizing cell culture. The aim of this study was to quantify cell proliferation within a perfusion bioreactor and correlate it to the wall shear stress (WSS) distribution by combining 3-D imaging and computational fluid dynamics simulations.NIH-3T3 fibroblasts were cultured onto a scaffold model made of impermeable polyacetal spheres or Polydimethylsiloxane cubes.

Shear bond strength and interface analysis between a resin composite and a recent high-viscous glass ionomer cement bonded with various adhesive systems.

Objective: This study investigated the shear bond strength (SBS) and interface between a resin composite and a new high-viscous glass ionomer cement (HV-GIC), a HV-GIC, a resin-modified glass ionomer cement (RM-GIC), a bulk-fill flowable composite, and a regular flowable composite bonded with various adhesive systems.

Methods And Materials: A resin composite (Filtek Z350) was bonded to a new HV-GIC (EQUIA Forte Fil) using various adhesive systems, including a universal adhesive in self-etch and etch-and-rinse mode (Scotchbond Universal), a two-step etch-and-rinse adhesive (Scotchbond 1-XT), a one-step self-etch adhesive (Optibond All-in-one) tested also after silane application (Monobond Plus), and a coating material (EQUIA Forte Coat). The resin composite was also bonded to a HV-GIC (Fuji IX GP), a RM-GIC (Fuji II LC), a bulk-fill flowable composite (SDR), and a regular flowable composite (Tetric Evo Flow) with the universal adhesive in self-etch mode (Scotchbond Universal).

Mesoscale porosity at the dentin-enamel junction could affect the biomechanical properties of teeth.

In this paper, the 3D-morphology of the porosity in dentin is investigated within the first 350μm from the dentin-enamel junction (DEJ) by fluorescence confocal laser scanning microscopy (CLSM). We found that the porous microstructure exhibits a much more complex geometry than classically described, which may impact our fundamental understanding of the mechanical behavior of teeth and could have practical consequences for dental surgery. Our 3D observations reveal numerous fine branches stemming from the tubules which may play a role in cellular communication or mechanosensing during the early stages of dentinogenesis.

Bond strength and interfacial morphology of orthodontic brackets bonded to eroded enamel treated with calcium silicate-sodium phosphate salts or resin infiltration.

Objective:  To investigate the shear bond strength (SBS) of orthodontic brackets bonded to eroded enamel treated with preventive approaches and to examine the enamel/bracket interfaces.

Materials And Methods:  Ninety-one brackets were bonded to seven groups of enamel samples: sound; eroded; eroded+treated with calcium silicate-sodium phosphate salts (CSP); eroded+infiltrated by ICON; eroded+infiltrated by ICON and brackets bonded with 1-month delay; eroded+infiltrated by an experimental resin; and eroded+infiltrated by an experimental resin and brackets bonded with 1-month delay. For each group, 12 samples were tested in SBS and bond failure was assessed with the adhesive remnant index (ARI); one sample was examined using scanning electron microscopy (SEM).

Influence of CAD/CAM tool and material on tool wear and roughness of dental prostheses after milling.

Statement Of Problem: Computer-aided design/computer-aided manufacturing (CAD/CAM) machining influences the surface roughness of dental restorations and tool wear. Roughness must be suitable to meet clinical requirements, and the tool must last as long as possible.

Purpose: The purpose of this pilot study was to investigate the influence of the CAD/CAM tool-material couple on tool wear and surface roughness after milling.

A New Method Combining Finite Element Analysis and Digital Image Correlation to Assess Macroscopic Mechanical Properties of Dentin.

A literature review points out a large discrepancy in the results of the mechanical tests on dentin that can be explained by stress and strain assessment during the tests. Errors in these assessments during mechanical tests can lead to inaccurate estimation of the mechanical properties of the tested material. On top of that, using the beam theory to analyze the bending test for thick specimens will increase these experimental errors.

White spots on enamel: treatment protocol by superficial or deep infiltration (part 2).

In this 2nd part, the current treatment of white spot lesions by erosion/infiltration is presented, beginning with a reminder of the principle of superficial infiltration, which enables most early carious lesions, fluorosis and post-traumatic lesions to be treated. However, this technique has met with frequent failures in cases of MIH or deep lesions of traumatic origin or those associated with fluorosis. For this reason a new deep infiltration technique is proposed: thanks to its global treatment concept, this enables all white spots to be treated.

White defects on enamel: diagnosis and anatomopathology: two essential factors for proper treatment (part 1).

Early-stage caries (white spots), fluoroses, traumatic hypomineralizations and molar incisive hypomineralization (MIH) all present, to differing degrees, clinical symptoms involving white marks on the enamel. This article shows that proper diagnosis leads to better understanding of the three-dimensional aspects of the lesion, thereby ensuring the appropriate choice of a specific treatment.

Demineralized dentin 3D porosity and pore size distribution using mercury porosimetry.

Objectives: The objectives of this study were to assess demineralized dentin porosity and quantify the different porous features distribution within the material using mercury intrusion porosimetry (MIP) technique. We compared hexamethyldisilazane (HMDS) drying and lyophilization (LYO) (freeze-drying) in sample preparation.

Methods: Fifty-six dentin discs were assigned into three groups.