Self-assembled human osseous cell sheets as living biopapers for the laser-assisted bioprinting of human endothelial cells.

A major challenge during the engineering of voluminous bone tissues is to maintain cell viability in the central regions of the construct. In vitro prevascularization of bone substitutes relying on endothelial cell bioprinting has the potential to resolve this issue and to replicate the native bone microvasculature. Laser-assisted bioprinting (LAB) commonly uses biological layers of hydrogel, called 'biopapers', to support patterns of printed cells and constitute the basic units of the construct. The self-assembly approach of tissue engineering allows the production of biomimetic cell-derived bone extracellular matrix including living cells. We hypothesized that self-assembled osseous sheets can serve as living biopapers to support the LAB of human endothelial cells and thus guide tubule-like structure formation. Human umbilical vein endothelial cells were bioprinted on the surface of the biopapers following a predefined pattern of lines. The osseous biopapers showed relevant matrix mineralization and pro-angiogenic hallmarks. Our results revealed that formation of tubule-like structures was favored when the cellular orientation within the biopaper was parallel to the printed lines. Altogether, we validated that human osseous cell sheets can be used as biopapers for LAB, allowing the production of human prevascularized cell-based osseous constructs that can be relevant for autologous bone repair applications.

Self-perceived educational needs of junior assistant professors in Conservative Dentistry and Endodontics in France.

INTRODUCTION: Academic dental educators play a major role in training future dentists. They help students to develop medical knowledge and behavioural skills that improve the quality and rigor of their future practice. Therefore, their experience and knowledge are critical to ensure effective learning. However, a French national workshop revealed that most junior assistant professors lack educational skills at the beginning of their career. The aim of this study was to assess educational training needs of junior assistant professors in the Department of Conservative Dentistry and Endodontics. MATERIALS AND METHODS: An electronic survey was sent to junior assistant professors belonging to Departments of Conservative Dentistry and Endodontics within the 16 French dental schools in 2016. This survey was designed to collect data regarding their motivations, teaching expertise and interest in pedagogy. RESULTS: Sixty of the 69 junior educators turned in their answers, which represents a response rate of 87%. About 86.7% of respondents cited their attraction to teaching as one of the main reasons behind their application. The major difficulty encountered by junior faculty was related to course preparation. Only 15% had received educational training despite the fact that 98.3% were convinced of the usefulness of such a training for junior teachers. CONCLUSION: This study identified the motivations and difficulties encountered by junior assistant professors. This collection of educational needs should be considered when planning a national programme for educational training of dental faculty that will promote the acquisition of teaching skills and improve the education of dental students.

In vitro assessment of a collagen/alginate composite scaffold for regenerative endodontics.

AIM: To develop a biological scaffold that could be moulded to reproduce the geometry of a gutta-percha point with precision and allow the differentiation of mesenchymal stem cells into osteoblasts to be used as a regenerative endodontic material. METHODOLOGY: A collagen/alginate composite scaffold was cast into a sodium alginate mould to produce a gutta-percha point-like cone. Prior to gelation, the cone was seeded with human stem cells from the apical papilla (SCAPs) to evaluate cell/scaffold interactions. The reconstructed tissue was characterized after 8 days in culture. Elastic modulus, tissue compaction and cell differentiation were assessed. Student t-tests and the Mann-Whitney U test were performed. RESULTS: The fabrication method developed enabled the shape of a gutta-percha point to be mimicked with great accuracy and reproducibility (P = 0.31). Stem cells seeded into this composite scaffold were able to spread, survive and proliferate (P < 0.001). Moreover, they were able to differentiate into osteoblasts and produce calcified osseous extracellular matrix (P < 0.001). The construct showed no significant contraction after 8 days, preserving its shape and tip diameter (P = 0.58). CONCLUSIONS: The composite scaffold could present substantial benefits compared to synthetic materials. It could provide a favourable healing environment in the root canal conducive for regenerative endodontics and is therefore appropriate to be evaluated in vivo in further studies.

Effective parameters for film-free femtosecond laser assisted bioprinting.

Optimal conditions for femtosecond laser bioprinting setup are reported on in terms of numerical aperture and accuracy of focal spot location for different bioinks to deposit without using a metallic absorbing layer.

Root canal shaping using rotary nickel-titanium files in preclinical teaching.

AIMS: This study set out to evaluate the prevalence of iatrogenic events during preclinical teaching of endodontics, comparing manual stainless steel versus nickel-titanium (Ni-Ti) rotary techniques for shaping natural root canals. METHOD: Two groups of 13 inexperienced dental students were randomly made up and asked to shape 104 canals in natural teeth. Group R used Ni-Ti rotary files for shaping while Group M used a sequence of five manual stainless steel files. Occurrence of file breakage, loss of work length, and iatrogenic instrumentation on apical foramina were evaluated. RESULTS: Overall occurrence of adverse events during shaping did not differ between the groups, being 58% in Group R and 51% in Group M. Inter-group distribution of type of event differed significantly, however. File breakage (7.7%) and loss of working length of > 2 mm (6.7%) occurred only in Group R. Iatrogenic shaping on apical foramina showed the same frequency in each group. CONCLUSION: Manual instrumentation is safer than rotary instrumentation in the hands of inexperienced students. Acquiring skill in the use of Ni-Ti rotary instrumentation requires specific preclinical training to avert file breakage. These findings argue for the rethinking of theoretical and practical coursework in endodontics teaching, especially in dentistry schools where students are required to treat patients during their training.