Bioactive gelatin-sheets as novel biopapers to support prevascularization organized by laser-assisted bioprinting for bone tissue engineering

Despite significant advances in the management of patients with oral cancer, maxillofacial reconstruction after ablative surgery remains a clinical challenge. In bone tissue engineering, biofabrication strategies have been proposed as promising alternatives to solve issues associated with current therapies and to produce bone substitutes that mimic both the structure and function of native bone. Among them, laser-assisted bioprinting (LAB) has emerged as a relevant biofabrication method to print living cells and biomaterials with micrometric resolution onto a receiving substrate, also called 'biopaper'. Recent studies have demonstrated the benefits of prevascularization using LAB to promote vascularization and bone regeneration, but mechanical and biological optimization of the biopaper are needed. The aim of this study was to apply gelatin-sheet fabrication process to the development of a novel biopaper able to support prevascularization organized by LAB for bone tissue engineering applications. Gelatin-based sheets incorporating bioactive glasses (BGs) were produced using various freezing methods and crosslinking (CL) parameters. The different formulations were characterized in terms of microstructural, physical, mechanical, and biological properties in monoculture and coculture. Based on multi-criteria analysis, a rank scoring method was used to identify the most relevant formulations. The selected biopaper underwent additional characterization regarding its ability to support mineralization and vasculogenesis, its bioactivity potential andin vivodegradability. The biopaper 'Gel5wt% BG1wt%-slow freezing-CL160 °C 24 h' was selected as the best candidate, due to its suitable properties including high porosity (91.69 ± 1.55%), swelling ratio (91.61 ± 0.60%), Young modulus (3.97 × 104± 0.97 × 104Pa) but also its great cytocompatibility, osteogenesis and bioactivity properties. The preorganization of human umbilical vein endothelial cell using LAB onto this new biopaper led to the formation of microvascular networks. This biopaper was also shown to be compatible with 3D-molding and 3D-stacking strategies. This work allowed the development of a novel biopaper adapted to LAB with great potential for vascularized bone biofabrication.

Effect of Bioactive Glasses and Basic Fibroblast Growth Factor on Dental Pulp Cells

Ideal regeneration of hard tissue and dental pulp has been reported with the use of a combination of bioactive glass and basic fibroblast growth factor (bFGF). However, no previous study has investigated the molecular mechanisms underlying the processes induced by this combination in dental pulp cells. This study aimed to examine the cellular phenotype and transcriptional changes induced by the combination of bioactive glass solution (BG) and bFGF in dental pulp cells using phase-contrast microscopy, a cell counting kit-8 assay, alkaline phosphatase staining, and RNA sequence analysis. bFGF induced elongation of the cell process and increased the number of cells. Whereas BG did not increase ALP activity, it induced extracellular matrix-related genes in the dental pulp. In addition, the combination of BG and bFGF induces gliogenesis-related genes in the nervous system. This is to say, bFGF increased the viability of dental pulp cells, bioactive glass induced odontogenesis, and a dual stimulation with bioactive glass and bFGF induced the wound healing of the nerve system in the dental pulp. Taken together, bioactive glass and bFGF may be useful for the regeneration of the dentin-pulp complex.

Influence of practical and clinical experience on dexterity performance measured using haptic virtual reality simulator

INTRODUCTION

Development of dexterity, hand-eye coordination and self-assessment are essential during the preclinical training of dental students. To meet this requirement, dental simulators have been developed combining virtual reality with a force feedback haptic interface. The aim of this study was to assess the capability of the VirTeaSy^© haptic simulator to discriminate between users with different levels of practical and clinical experience.

MATERIALS AND METHODS

Fifty-six volunteers divided into five groups (non-dentists, 1st/3rd/final-year dental students, recent graduates) had three attempts to prepare an occlusal amalgam cavity using the simulator. Percentages of volumes prepared inside (%IV) and outside (%OV) the required cavity, skill index and progression rate, referring to the evolution of skill index between trials 1 and 3, were assessed. The dental students and recent graduates completed a questionnaire to gather their opinions about their first hands-on experience with a haptic simulator.

RESULTS

The results showed no significant difference between the groups at the first attempt. Following the third attempt, the skill index was improved significantly. Analysis of progression rates, characterised by large standard deviations, did not reveal significant differences between groups. The third attempt showed significant differences in skill index and %IV between 1st-year undergraduate dental students and both non-dentists and recent dental graduates. The questionnaire indicated a tendency for dental operators to consider the simulator as a complement to their learning and not a substitute for traditional methods.

CONCLUSION

This study did not show the ability of a basic aptitude test on VirTeaSy^© haptic simulator to discriminate between users of different levels of expertise. Optimisations must be considered in order to make simulation-based assessment clinically relevant.

In vitroandin vivocharacterization of a novel tricalcium silicate-based ink for bone regeneration using laser-assisted bioprinting

Grafts aside, current strategies employed to overcome bone loss still fail to reproduce native tissue physiology. Among the emerging bioprinting strategies, Laser-Assisted Bioprinting (LAB) offers very high resolution, allowing designing micrometric patterns in a contactless manner, providing a reproducible tool to test ink formulation. To this date, no LAB associated ink succeeded to provide a reproducible ad integrum bone regeneration on a murine calvaria critical size defect model. Using the CE approved BioRoot RCS® as a mineral addition to a collagen-enriched ink compatible with LAB, the present study describes the process of the development of a solidifying tricalcium silicate-based ink as a new bone repair promoting substrates in a LAB model. This ink formulation was mechanically characterized by rheology to adjust it for LAB. Printed aside Stromal Cells from Apical Papilla (SCAPs), this ink demonstrated a great cytocompatibility, with significant in vitro positive impact upon cell motility, and an early osteogenic differentiation response in the absence of another stimulus. Results indicated that the in vivo application of this new ink formulation to regenerate critical size bone defect tends to promote the formation of bone volume fraction without affecting the vascularization of the neo-formed tissue. The use of LAB techniques with this ink failed to demonstrate a complete bone repair, whether SCAPs were printed or not of at its direct proximity. The relevance of the properties of this specific ink formulation would therefore rely on the quantity applied in situ as a defect filler rather than its cell modulation properties observed in vitro. For the first time, a tricalcium silicate-based printed ink, based on rheological analysis, was characterized in vitro and in vivo, giving valuable information to reach complete bone regeneration through formulation updates. This LAB-based process could be generalized to normalize the characterization of candidate ink for bone regeneration.

Knowledge and Opinions of French Dental Students Toward Occlusal and Proximal Restorative Thresholds

PURPOSE

To investigate the practices, knowledge and opinions of French dental students (FDSs) in various domains of minimal intervention (MI) in cariology.

MATERIALS AND METHODS

A cross-sectional, questionnaire-based study was conducted in spring 2018 among all fifth-year French dental students (FDSs) from the 16 French dental schools. The present article focuses on restorative management. Statistical analyses (descriptive, chi-squared) were performed.

RESULTS

The response rate was 84.5%. Overall, 97.4% of respondents would have operatively intervened for proximal and 83% for occlusal carious lesions, respectively, while non-or micro-invasive intervention would have been possible. Interestingly, 15% would completely open the occlusal fissures. For both occlusal and proximal lesions requiring a restoration, composite resin was indicated by over 95% of the respondents. In a clinical case, 51.6% of FDSs who rightly diagnosed an enamel carious lesion would operatively intervene. When FDSs could not diagnose the type of carious lesions, a high proportion of invasive actions were also reported (40%). FDSs who read scientific articles were more likely to consider the high importance of not filling sound teeth unnecessarily (p = 0.033).

CONCLUSION

FDSs do not have sufficient awareness of MI guidelines regarding occlusal and proximal restorative thresholds. Efforts are required in dental schools to teach FDSs to postpone invasive/restorative strategies to later stages of carious progression. There is a need to strengthen prevention techniques and non-invasive options in the teaching of MI in cariology.

Knowledge and Opinions of French Dental Students in Operative Dentistry - Management of Deep Carious Lesions

PURPOSE

A questionnaire survey was recently undertaken among French dental students (FDSs) to investigate their practices, knowledge and opinions in various domains of minimal intervention (MI) in cariology. The present work focuses on management of deep carious lesions (DCLs).

MATERIALS AND METHODS

The questionnaire was administered (Spring 2018) to all the fifth-year students of the 16 French dental schools. Descriptive analyses were performed.

RESULTS

Among 1370 FDSs (response rate: 84.5%), hardness was the most commonly reported criterion for assessing the endpoint of carious tissue removal (53.9%), followed by firm dentin (40.0%). Regarding FDSs' opinion of leaving carious dentine under a restoration, 41.9% of the respondents agreed that carious tissues should always be removed completely. For an asymptomatic tooth with DCLs and exposed pulp, direct pulp capping was mainly chosen (93.9%). In a clinical case correctly diagnosed as a reversible pulpitis by 79.7% of respondents, nearly half of FDSs chose a one-step complete excavation (48.3%) followed by selective excavation (25.1%), then two-step complete excavation (20.9%) and a minority (5.7%) opted for pulpal therapy (biopulpotomy or endodontic treatment).

CONCLUSION

The present results suggest an inadequate dissemination of MI concepts among FDSs towards DCL management. The present results show the need for a harmonisation and a reinforcement of teaching evidence-based MI according to the latest European recommendations.

Knowledge and opinions of French dental students related to caries risk assessment and dental sealants (preventive and therapeutic)

OBJECTIVES

A national questionnaire study was performed to document knowledge and opinions of French dental students (FDSs) about minimal intervention (MI) in dentistry especially caries risk assessment (CRA) and dental sealants (DSs).

MATERIALS AND METHODS

A questionnaire was administered to the fifth-year dental FDSs (n = 1370) from the 16 French dental schools. Descriptive and statistical analyses were performed.

RESULTS

The response rate was 84.5%. A large majority of respondents (87.8%) linked MI with minimally invasive dentistry and 77.4% considered MI as a concept based on prevention. About 80% stated they use CRA in clinical practice, mostly without any specific form. If 80.4% of the respondents would base their treatment plans on CRA, only 55.1% would regularly plan preventive regimens according to individual risk level. However, while 96.6% declared they perform preventive DSs, only 44.3% considered therapeutic sealants as a routine treatment. Although 75.1% of FDSs stated that they had sufficient learning and training related to CRA, 55.9% thought that they need further education about preventive and therapeutic DSs.

CONCLUSION

Although FDSs seem to be aware of the importance of CRA and preventive strategies, this study shows the need to harmonize the teaching in cariology according to the latest European recommendations.

CLINICAL RELEVANCE

A national questionnaire study showed variability towards knowledge and opinions of FDSs related to MI in cariology. This may impact care provisions in their future professional life showing the urgent need to harmonize the teaching of MI in cariology in France.

In situ prevascularization designed by laser-assisted bioprinting: effect on bone regeneration

Vascularization plays a crucial role in bone formation and regeneration process. Development of a functional vasculature to improve survival and integration of tissue-engineered bone substitutes remains a major challenge. Biofabrication technologies, such as bioprinting, have been introduced as promising alternatives to overcome issues related to lack of prevascularization and poor organization of vascular networks within the bone substitutes. In this context, this study aimed at organizing endothelial cells in situ, in a mouse calvaria bone defect, to generate a prevascularization with a defined architecture, and promote in vivo bone regeneration. Laser-assisted bioprinting (LAB) was used to pattern Red Fluorescent Protein-labeled endothelial cells into a mouse calvaria bone defect of critical size, filled with collagen containing mesenchymal stem cells and vascular endothelial growth factor. LAB technology allowed safe and controlled in vivo printing of different cell patterns. In situ printing of endothelial cells gave rise to organized microvascular networks into bone defects. At two months, vascularization rate (vr) and bone regeneration rate (br) showed statistically significant differences between the 'random seeding' condition and both 'disc' pattern (vr = +203.6%; br = +294.1%) and 'crossed circle' pattern (vr = +355%; br = +602.1%). These results indicate that in vivo LAB is a valuable tool to introduce in situ prevascularization with a defined configuration and promote bone regeneration.

Micropatterning of endothelial cells to create a capillary-like network with defined architecture by laser-assisted bioprinting

Development of a microvasculature into tissue-engineered bone substitutes represents a current challenge. Seeding of endothelial cells in an appropriate environment can give rise to a capillary-like network to enhance prevascularization of bone substitutes. Advances in biofabrication techniques, such as bioprinting, could allow to precisely define a pattern of endothelial cells onto a biomaterial suitable for in vivo applications. The aim of this study was to produce a microvascular network following a defined pattern and preserve it while preparing the surface to print another layer of endothelial cells. We first optimise the bioink cell concentration and laser printing parameters and then develop a method to allow endothelial cells to survive between two collagen layers. Laser-assisted bioprinting (LAB) was used to pattern lines of tdTomato-labeled endothelial cells cocultured with mesenchymal stem cells seeded onto a collagen hydrogel. Formation of capillary-like structures was dependent on a sufficient local density of endothelial cells. Overlay of the pattern with collagen I hydrogel containing vascular endothelial growth factor (VEGF) allowed capillary-like structures formation and preservation of the printed pattern over time. Results indicate that laser-assisted bioprinting is a valuable technique to pre-organize endothelial cells into high cell density pattern in order to create a vascular network with defined architecture in tissue-engineered constructs based on collagen hydrogel.

Magnetic Resonance Imaging for tracking cellular patterns obtained by Laser-Assisted Bioprinting

Recent advances in the field of Tissue Engineering allowed to control the three-dimensional organization of engineered constructs. Cell pattern imaging and in vivo follow-up remain a major hurdle in in situ bioprinting onto deep tissues. Magnetic Resonance Imaging (MRI) associated with Micron-sized superParamagnetic Iron Oxide (MPIO) particles constitutes a non-invasive method for tracking cells in vivo. To date, no studies have utilized Cellular MRI as a tool to follow cell patterns obtained via bioprinting technologies. Laser-Assisted Bioprinting (LAB) has been increasingly recognized as a new and exciting addition to the bioprinting’s arsenal, due to its rapidity, precision and ability to print viable cells. This non-contact technology has been successfully used in recent in vivo applications. The aim of this study was to assess the methodology of tracking MPIO-labeled stem cells using MRI after organizing them by Laser-Assisted Bioprinting. Optimal MPIO concentrations for tracking bioprinted cells were determined. Accuracy of printed patterns was compared using MRI and confocal microscopy. Cell densities within the patterns and MRI signals were correlated. MRI enabled to detect cell patterns after in situ bioprinting onto a mouse calvarial defect. Results demonstrate that MRI combined with MPIO cell labeling is a valuable technique to track bioprinted cells in vitro and in animal models.

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.

Diagnosis and Management of Natal and Neonatal Teeth: Case Report of Three Newborns

Natal and neonatal teeth are rare features that can lead to various issues, from traumatic injuries and feeding difficulties to more severe problems, such as risk of aspiration due to excessive mobility of teeth. The purpose of this paper is to discuss the diagnosis and management of natal and neonatal teeth, and describe three cases of newborns with natal teeth. Decision processes and management are detailed regarding the specificity of each case. Periodic follow-up is recommended to maintain oral health and prevent any issues related to premature loss or eruption of primary teeth. A close collaboration between pediatricians and dentists should be considered in order to allow early diagnosis and efficient treatment.

Femtosecond versus picosecond laser pulses for film-free laser bioprinting

We investigate the properties of microjets in the context of film-free laser induced forward transfer in the femtosecond and picosecond regimes. The influence of the pulse duration (ranging from 0.4 to 12 ps) and the energy (ranging from 6 to 12 μJ) is systematically studied on the height, diameter, speed, volume, and shape of the jets. The 400 fs pulses generate thin and stable jets compatible with bioprinting, while 14 ps pulses generate more unstable jets. A pulse duration around 8 ps seems, therefore, to be an interesting trade-off to cover many bio-applications of microjets generated by lasers.

Efficacy of orally administered prednisolone versus partial endodontic treatment on pain reduction in emergency care of acute irreversible pulpitis of mandibular molars: study protocol for a randomized controlled trial

BACKGROUND

Irreversible pulpitis is a highly painful inflammatory condition of the dental pulp which represents a common dental emergency. Recommended care is partial endodontic treatment. The dental literature reports major difficulties in achieving adequate analgesia to perform this emergency treatment, especially in the case of mandibular molars. In current practice, short-course, orally administered corticotherapy is used for the management of oral pain of inflammatory origin. The efficacy of intraosseous local steroid injections for irreversible pulpitis in mandibular molars has already been demonstrated but resulted in local comorbidities. Oral administration of short-course prednisolone is simple and safe but its efficacy to manage pain caused by irreversible pulpitis has not yet been demonstrated. This trial aims to evaluate the noninferiority of short-course, orally administered corticotherapy versus partial endodontic treatment for the emergency care of irreversible pulpitis in mandibular molars.

METHODS/DESIGN

This study is a noninferiority, open-label, randomized controlled clinical trial conducted at the Bordeaux University Hospital. One hundred and twenty subjects will be randomized in two 1:1 parallel arms: the intervention arm will receive one oral dose of prednisolone (1 mg/kg) during the emergency visit, followed by one morning dose each day for 3 days and the reference arm will receive partial endodontic treatment. Both groups will receive planned complete endodontic treatment 72 h after enrollment. The primary outcome is the proportion of patients with pain intensity below 5 on a Numeric Scale 24 h after the emergency visit. Secondary outcomes include comfort during care, the number of injected anesthetic cartridges when performing complete endodontic treatment, the number of antalgic drugs and the number of patients coming back for consultation after 72 h.

DISCUSSION

This randomized trial will assess the ability of short-term corticotherapy to reduce pain in irreversible pulpitis as a simple and rapid alternative to partial endodontic treatment and to enable planning of endodontic treatment in optimal analgesic conditions.

TRIAL REGISTRATION

ClinicalTrials.gov, identifier: NCT02629042 . Registered on 7 December 2015. (Version n°1.1 28 July 2015).

Dental abnormalities and preventive oral care in Schimke immuno-osseous dysplasia

BACKGROUND

Schimke immuno-osseous dysplasia (SIOD) is a rare, severe, autosomal recessive disorder that results in spondyloepiphyseal dysplasia, renal dysfunction, immunodeficiency, facial dysmorphism and growth failure. Little is known about oral features associated with SIOD. Some of the dental anomalies encountered are specific to SIOD and have only been reported in individuals with SIOD.

CASE REPORT

This paper describes the clinical and radiographic dental manifestations of SIOD in two Caucasian brothers. Both lived to be about 10 years old. After a variety of symptoms were reported, a diagnosis of SIOD was finally made when the brothers were, respectively, 5 and 8 years old. At that time, dental anomalies, such as dyschromia, bulbous crowns, short and thin roots, had not been taken into account to establish the diagnosis. However, knowledge of the dental features characteristic of this disease could have helped make the diagnosis. Although both were caries- and periodontal disease-free, special attention was focused on prevention, including dietary counselling, plaque control, oral hygiene instructions and the use of fluoridated toothpaste.

FOLLOW-UP

The two patients were followed every 6 months, for over 2 years (until their death), by both a private dentist and a university hospital dentist, which helped them maintain good oral health. Oral hygiene was assessed at each appointment and fissure sealants were placed by the private practitioner on their first permanent molars.

CONCLUSION

This report describes dental anomalies specific to SIOD that could facilitate diagnosis. Clinicians and dentists should work in collaboration to diagnose and treat children with SIOD. These patients require regular and specific dental management because of their fragile health and their characteristic dental anomalies. Ideally, preventive visits should be scheduled every 6 months in addition to curative visits as needed.

Dental abnormalities in Schimke immuno-osseous dysplasia

Described for the first time in 1971, Schimke immuno-osseous dysplasia (SIOD) is an autosomal-recessive multisystem disorder that is caused by bi-allelic mutations of SMARCAL1, which encodes a DNA annealing helicase. To define better the dental anomalies of SIOD, we reviewed the records from SIOD patients with identified bi-allelic SMARCAL1 mutations, and we found that 66.0% had microdontia, hypodontia, or malformed deciduous and permanent molars. Immunohistochemical analyses showed expression of SMARCAL1 in all developing teeth, raising the possibility that the malformations are cell-autonomous consequences of SMARCAL1 deficiency. We also found that stimulation of cultured skin fibroblasts from SIOD patients with the tooth morphogens WNT3A, BMP4, and TGFβ1 identified altered transcriptional responses, raising the hypothesis that the dental malformations arise in part from altered responses to developmental morphogens. To the best of our knowledge, this is the first systematic study of the dental anomalies associated with SIOD.