Modification of national OSCE due to COVID-19 - Implementation and students' feedback.

AIM: The aims were to describe the development of a modified national online OSCE during COVID-19 and assess related student feedback. MATERIAL AND METHODS: The modified online OSCE comprising of eight question entities was organised simultaneously in all four dental institutes of Finland using the Moodle virtual learning environment. All fourth-year students (n = 179) attended the examination online at home. Student feedback was collected via an anonymous questionnaire with multiple-choice questions and open-ended questions concerning attitudes towards the modified online OSCE, as well as content and usability of the question entities in the examination. Means and standard deviations were calculated for multiple-choice questions. Content analysis was used for open-ended questions. RESULTS: Of 179 students, 119 (66%) consented to the study. Students experienced they had received adequate information (mean 3.8; SD 1.2), had a positive attitude before the examination (4.0; 1.0) and found the practice test useful (3.7; 1.1) (range 1-5). Technical implementation (2.7; 0.7) and the difficulty of the questions (2.9; 0.6) (range 1-4) were found to be good. The teaching students received during their studies was sufficient (3.2; 0.5) (range 1-4). Content (mean 3.2; 0.4) and usability (2.9; 0.4) of the question entities were good (range 1-4). The themes arising from open-ended questions were importance and practicality of the topic (in questions) in relation to the work of a dentist and gratitude for the rapid conversion of the OSCE into an online examination despite COVID-19. The themes arising from negative experiences included difficulties in completing the examination within the time allocated, and dissatisfaction with the model answers provided after the examination. CONCLUSION: The positive student feedback towards the modified online OSCE encourages including an online examination to complement the traditional OSCE.

Country and gender differences in the motivation of dental students-An international comparison.

PURPOSE: The objective of this study, conducted in Germany, Finland and Turkey, was to identify whether motivations to study dentistry varied by country, gender or year of study. METHODS: The multicentre pilot study was conducted in English language in 2014. Participants (n = 469 dental students) were either in the first or last year of study. The response rate was 91%. RESULTS: The sample comprised 63% females and 37% males, reflecting the common gender distribution in dental education. A total of 236 first year students (50.3%) and 233 final year students (49.7%) took part in the study. The participants were aged 21-25 years and of 15 different nationalities, mostly from Turkey, Germany and Finland. Considering who motivated them most to become a dentist, the most common answer was "self-motivated" (49.5%). 23.4% of the students stated having been motivated by a "family member or friend, who is a dentist," while 24.3% said they had been motivated by a "family member or friend, who is not a dentist." -Very few students (2.8%) recorded having been motivated by a "high school or college counsellor." Motivations for choosing dentistry as a career included "ability to help people," "self-employment," "income potential," "working with hands" and "status and prestige," all of which were rated as highly important. "Time management" and "career variety" were rated as moderately important. Significant statistical differences were observed by country and gender. For the German students, a dental relative was significantly more often relevant than for the Finnish and Turkish students, who were more often influenced by family members or friends not working in the dental field. "Time management" seemed to be significantly more important to female than to male students. CONCLUSION: In line with a feminisation of the workforce in dentistry, a well-structured working environment and well-thought-out time management may play an increased role in future work force planning (Gender dentistry: International vergleichende Studie zu Karrierewahl und Spezialisierungswünschen von Zahnmedizinstudenten. Ulm: Universität Ulm).

Blood and fibroblast responses to thermoset BisGMA-TEGDMA/glass fiber-reinforced composite implants in vitro.

OBJECTIVES: This in vitro study was designed to evaluate both blood and human gingival fibroblast responses on fiber-reinforced composite (FRC) aimed to be used as oral implant abutment material. MATERIAL AND METHODS: Two different types of substrates were investigated: (a) Plain polymer (BisGMA 50%-TEGDMA 50%) and (b) FRC. The average surface roughness (Ra) was measured using spinning-disk confocal microscope. The phase composition was identified using X-ray diffraction analyzer. The degree of monomer conversion (DC%) was determined using FTIR spectrometry. The blood response, including the blood-clotting ability and platelet adhesion morphology, was evaluated. Fibroblast cell responses were studied in cell culture environment using routine test conditions. RESULTS: The Ra of the substrates investigated was less than 0.1 µm with no signs of surface crystallization. The DC% was 89.1 ± 0.5%. The FRC substrates had a shorter clotting time and higher platelets activation state than plain polymer substrates. The FRC substrates showed higher (P < 0.01-0.001) amount of adhered cells than plain polymer substrates at all time points investigated. The strength of attachment was evaluated using serial trypsinization, the number of cells detached from FRC substrates was 59 ± 5%, whereas those detached from the plane polymer substrates was 70 ± 5%, indicating a stronger (P < 0.01) cell attachment on the FRC surfaces. Fibroblasts grew more efficiently on FRC than on plain polymer substrates, showing significantly higher (P < 0.01) cell metabolic activities throughout the experiment. CONCLUSIONS: The presence of E-glass fibers enhances blood and fibroblast responses on composite surfaces in vitro.

In vitro blood and fibroblast responses to BisGMA-TEGDMA/bioactive glass composite implants.

This in vitro study was designed to evaluate both blood and human gingival fibroblast responses to bisphenol A-glycidyl methacrylate-triethyleneglycol dimethacrylate (BisGMA-TEGDMA)/bioactive glass (BAG) composite, aimed to be used as composite implant abutment surface modifier. Three different types of substrates were investigated: (a) plain polymer (BisGMA 50 wt%-TEGDMA 50 wt%), (b) BAG-composite (50 wt% polymer + 50 wt% fraction of BAG-particles, <50 µm), and (c) plain BAG plates (100 wt% BAG). The blood response, including the blood-clotting ability and platelet adhesion morphology were evaluated. Human gingival fibroblasts were plated and cultured on the experimental substrates for up to 10 days, then the cell proliferation rate was assessed using AlamarBlue assay™. The BAG-composite and plain BAG substrates had a shorter clotting time than plain polymer substrates. Platelet activation and aggregation were most extensive, qualitatively, on BAG-composite. Analysis of the normalized cell proliferation rate on the different surfaces showed some variations throughout the experiment, however, by day 10 the BAG-composite substrate showed the highest (P < 0.001) cell proliferation rate. In conclusion, the presence of exposed BAG-particles enhances fibroblast and blood responses on composite surfaces in vitro.

Novel additive manufactured scaffolds for tissue engineered trachea research.

CONCLUSIONS: This study demonstrates proof of concept for controlled manufacturing methods that utilize novel tailored biopolymers (3D photocuring technology) or conventional bioresorbable polymers (fused deposition modeling, FDM) for macroscopic and microscopic geometry control. The manufactured scaffolds could be suitable for tissue engineering research. OBJECTIVES: To design novel trachea scaffold prototypes for tissue engineering purposes, and to fabricate them by additive manufacturing. METHODS: A commercial 3D model and CT scans of a middle-aged man were obtained for geometrical observations and measurements of human trachea. Model trachea scaffolds with variable wall thickness, interconnected pores, and various degrees of porosity were designed. Photocurable polycaprolactone (PCL) polymer was used with 3D photocuring technology. Thermoplastic polylactide (PLA) and PCL were used with FDM. Cell cultivations were performed for biocompatibility studies. RESULTS: Scaffolds of various sizes and porosities were successfully produced. Both thermoplastic PLA and PCL and photocurable PCL could be used effectively with additive manufacturing technologies to print high-quality tubular porous biodegradable structures. Optical microscopic and SEM images showed the viability of cells. The cells were growing in multiple layers, and biocompatibility of the structures was shown.

Biodegradable and bioactive porous scaffold structures prepared using fused deposition modeling.

Three-dimensional printing (3DP) refers to a group of additive manufacturing techniques that can be utilized in tissue engineering applications. Fused deposition modeling (FDM) is a 3DP method capable of using common thermoplastic polymers. However, the scope of materials applicable for FDM has not been fully recognized. The purpose of this study was to examine the creation of biodegradable porous scaffold structures using different materials in FDM and to determine the compressive properties and the fibroblast cell response of the structures. To the best of our knowledge, the printability of a poly(ε-caprolactone)/bioactive glass (PCL/BAG) composite and L-lactide/ε-caprolactone 75/25 mol % copolymer (PLC) was demonstrated for the first time. Scanning electron microscope (SEM) images showed BAG particles at the surface of the printed PCL/BAG scaffolds. Compressive testing showed the possibility of altering the compressive stiffness of a scaffold without changing the compressive modulus. Compressive properties were significantly dependent on porosity level and structural geometry. Fibroblast proliferation was significantly higher in polylactide than in PCL or PCL/BAG composite. Optical microscope images and SEM images showed the viability of the cells, which demonstrated the biocompatibility of the structures.

Osteoblast proliferation and maturation on bioactive fiber-reinforced composite surface.

The objective of this study was to evaluate the proliferation and osteogenic potential of bone-marrow derived osteoblast-like cells on fiber-reinforced composite (FRC) substrates with and without bioactive glass surface modification. Three FRC materials were fabricated for the study: (a) grit-blasted FRC, (b) grit-blasted FRC with bidirectional net reinforcement and (c) FRC with bioactive glass (BAG) coating. Rat bone-marrow derived osteoblast-like cells were harvested and cultured on experimental material plates and on cp. titanium plates (control) for 21 days. The materials' surfaces were characterized by roughness testing and scanning electron microscopy. Cell growth and differentiation kinetics were subsequently investigated by evaluating proliferation, alkaline phosphatase (ALP) activity, osteocalcin (OC) and bone sialoprotein (BSP) production. On day 14, the cell proliferation was significantly lower (P<0.05) on FRC-BAG than on titanium and FRC. The proliferation on the other three materials was equal throughout the experiment. The maximal ALP activities on FRC, FRC-Net, and titanium were observed on day 21, whereas FRC-BAG had already reached the maximal level on day 14. Expression of osteoblastic markers (OC, BSP) indicates that the fastest osteogenic differentiation takes place on FRC after 7 days. In contrast, a slower differentiation process was observed on titanium than on any other tested material (P<0.015) at 21 days, as was confirmed by increased mRNA expression of OC and BSP. It can be concluded that the proliferation and maturation of osteoblast-like cells on FRC appears to be comparable to titanium. Presence of BAG enhances cell maturation.

Mechanical properties of oligomer-modified acrylic bone cement.

The aim of this study was to determine the mechanical properties of acrylic bone cement modified with an experimental oligomer filler, based on an amino acid of trans-4-hydroxy-L-proline synthesized in the laboratory. The test specimens were tested either dry, or after being stored in distilled water or in simulated body fluid (SBF) for 1 week and then tested in distilled water. The three-point bending test was used to measure the flexural strength and flexural modulus of the cement, and the compression tests were used to measure the compression strength and modulus. One test specimen from each group was examined under a scanning electron microscope (SEM) to determine the nature of the oligomer filler in the polymethylmethacrylate-polymethylacrylate copolymer-based (PMMA-PMA/PMMA) polymer blend. In dry conditions, the flexural strength of the test specimens tested in air was 66 MPa, and the compression strength was 93 GPa (p<0.001) for the plain bone cement. For the test specimens including 20 wt% of oligomer filler, the flexural strength was 37 MPa, and the compression strength was 102 MPa(p<0.001) in dry conditions. The storage in wet conditions (in distilled water and the SBF) decreased the flexural strength of the test specimens with 20 wt% of oligomer filler (p<0.001) by 60% and the flexural modulus by 44% compared to the plain bone cement specimens stored in the same conditions. The reduction in compression strength in wet conditions was 32%, and that of the compression modulus was 30% (p<0.001). No significant differences were found between test specimens stored in distilled water or SBF (ANOVA, p<0.001). In the SEM examinations, random voids were observed in the oligomer-PMMA-PMA/PMMA polymer blend after water or SBF storage. The results suggest that both water and SBF storage decrease the mechanical properties of the PMMA-PMA/PMMA bone cement modified with oligomer, while at the same time, there was porous formation in the bone cement structure.