The improvement of biocompatibility of adhesives : The effects of resveratrol on biocompatibility and dentin micro-tensile bond strengths of self-etch adhesives.

OBJECTIVE: The aim of this in vitro study is to evaluate the effects of resveratrol (RES) addition on the cytotoxicity and microtensile bond strength (µTBS) of different adhesives. MATERIALS AND METHODS: Five self-etching adhesives (G-aenial Bond-GC, Optibond All in One-Kerr, Gluma Self Etch-Kulzer, Clearfil S3 Bond-Kuraray, and Nova Compo-B Plus-Imicryl) were tested. They were applied to L-929 cell culture by the extract method. In the test groups, 0.5 µM RES (Sigma-Aldrich) was added into the medium. Cell viability was assessed by MTT assay after 24 h. Human extracted third molars were used for µTBS test (n = 7). The adhesives with or without 0.5 µM RES addition were applied on dentin surfaces. A composite build-up was constructed. Then, the specimens were sectioned into multiple beams with the non-trimming version of the microtensile test and subjected to microtensile forces. Statistical analysis was performed using ANOVA and post hoc Tukey test (p Ë‚ 0.05). RESULTS: The extracts of all adhesives decreased the cell viability. However, RES addition increased the cell viability in all groups (p Ë‚ 0.05). RES addition did not cause any decrease in µTBS values of the adhesives compared to baseline. Optibond All in One showed the highest µTBS after RES addition. It was followed by Clerafil S3 Bond and Nova Compo-B Plus. No difference was determined between the Optibond All in One and Clearfil S3 Bond. There was difference between Optibond All in One and Nova Compo-B Plus (p Ë‚ 0.05). CONCLUSION: RES addition may improve the biocompatibility without causing negative influence on µTBS of the adhesives. CLINICAL RELEVANCE: RES addition has clinical applicable potential to overcome the adverse biocompatibility of adhesives.

Procrastination and predictor variables among a group of dental students in Turkey.

The aim of this study was to assess the prevalence of procrastination among a group of Turkish dental students and to determine the predictors and consequences of procrastination. A total number of 273 females and 179 males (aged between 18 and 28) were included in the study. Tuckman procrastination scale, Academic Life Satisfaction Scale, Concern over Mistake Scale, Poor Time Management Scale, Self-Doubt Scale, Irrational Beliefs about Studying Scale, Positive and Negative Affect Schedule and Life Satisfaction Scale were used to gather data. Results indicated that 50% of participants were more likely to procrastinate their academic assignments or tasks. Procrastination score did not differ according to gender. The findings suggested that procrastinating students had a higher level of poor time management, self-doubt and irrational beliefs about studying, and poor academic performance and well-being than their non-procrastinating counterparts. Preventive strategies are necessary to overcome procrastination which affects the academic achievement, satisfaction, and well-being of dental students.

Intrapulpal temperature changes during curing of different bulk-fill restorative materials.

The aim of this study was to evaluate the intrapulpal temperature changes during the curing of different bulk-fill restorative materials. Ten mandibular molar teeth were selected and occlusal surfaces were removed to obtain a standard 0.5 mm occlusal dentin thickness. Five bulk-fill restorative materials and a conventional resin composite (control) were applied. The intrapulpal temperature changes during the curing of these materials were determined by a device simulating pulpal blood microcirculation. The difference between the initial and maximum temperature values (Δt), was recorded. The data were statistically analyzed with one-way ANOVA and Tukey's HSD test (p<0.05). There were statistically significant differences between materials (p<0.001). The light-curing bulkfill restoratives exhibited the highest Δt values. Equia Forte showed the lowest Δt values among all the groups (p<0.05). Bulk-fill restorative materials causes significantly different temperature changes in the pulp chamber according to curing type. Therefore, clinicians should be considered when using these materials.

In vivo performance of different scaffolds for dental pulp stem cells induced for odontogenic differentiation.

This study was designed to determine the in vivo performance of three different materials as scaffolds for dental pulp stem cells (DPSC) undergoing induced odontogenic differentiation. An odontogenic medium modified by the addition of recombinant human bone morphogenetic protein 2 was used in the experimental groups to induce differentiation. Mesenchymal stem cell medium was used in the control groups. DPSC were transplanted onto the backs of mice via three scaffolds: copolymer of L-lactide and DL-lactide (PLDL), copolymer of DL-lactide (PDL) and hydroxyapatite tricalcium phosphate (HA/TCP). The expression levels of dentin sialo-phosphoprotein (DSPP), dentin matrix protein-1 (DMP1), enamelysin/matrix metalloproteinase 20 (MMP20) and phosphate-regulating gene with homologies to endopeptidases on X chromosome (PHEX) were analysed using RT-PCR. The expressions in the experimental groups were compared to those in the control groups. The transcript expressions at 6 and 12 weeks were significantly different for all scaffolds (p < 0.05), except for the expression of DSPP in the PLDL group with regard to the time variable. Although there was a decrease in the expression of enamelysin/MMP20 in PLDL and HA/TCP at 12 weeks, all other expressions increased and reached their highest level at 12 weeks. The highest DSPP expression was in the PDL group (p < 0.05). The highest expression of DMP1 was detected in the HA/TCP group (p < 0.05). The highest expression of PHEX was in the PLDL group (p < 0.05). Consequently, PLDL and PDL seemed to be promising scaffold candidates for odontogenic regeneration at least as HA-TCP, when they were applied with the DPSC induced for odontogenic differentiation.

Medium modification with bone morphogenetic protein 2 addition for odontogenic differentiation.

The aim of this study was to evaluate whether medium modification improves the odontogenic differentiation of human dental pulp stem cells (DPSC) in vitro and in vivo. DPSC isolated from human impacted third molar teeth were analysed for clusters of differentiation with flow cytometry. Odontogenic differentiation was stimulated by medium modification with the addition of bone morphogenetic protein 2 (BMP2). The expression of dentin sialophosphoprotein, dentin matrix protein 1, enamelysin/matrix metalloproteinase 20 and the phosphate-regulating gene with homologies to endopeptidases on the X chromosome of the cells were analysed with RT-PCR at 7, 14 and 21 days. Then, DPSC were transplanted on the back of immunocompromised mice via a hydroxyapatite tricalcium phosphate scaffold, and the structure of the formed tissue was investigated. The cells were identified as mesenchymal stem cells with a 98.3% CD73 and CD90 double-positive cell rate. The increase in mineralization capacity and expression of human enamel-dentin specific transcripts proportional to the culture period were determined after differentiation. Six weeks after transplantation, an osteo-dentin matrix was formed in the group in which odontogenic differentiation was stimulated, and the odontogenic characteristics of the matrix were confirmed by histological examination and RT-PCR analysis. Odontogenic differentiation of the isolated and characterized human DPSC was improved with medium modification by the addition of BMP2 in vitro and in vivo. The defined medium and applied technique have a potential use for forming reparative dentin in the future, but the effects of the method should be investigated in long-term studies.

Medium modification with bone morphogenetic protein 2 addition for odontogenic differentiation

Abstract The aim of this study was to evaluate whether medium modification improves the odontogenic differentiation of human dental pulp stem cells (DPSC) in vitro and in vivo. DPSC isolated from human impacted third molar teeth were analysed for clusters of differentiation with flow cytometry. Odontogenic differentiation was stimulated by medium modification with the addition of bone morphogenetic protein 2 (BMP2). The expression of dentin sialophosphoprotein, dentin matrix protein 1, enamelysin/matrix metalloproteinase 20 and the phosphate-regulating gene with homologies to endopeptidases on the X chromosome of the cells were analysed with RT-PCR at 7, 14 and 21 days. Then, DPSC were transplanted on the back of immunocompromised mice via a hydroxyapatite tricalcium phosphate scaffold, and the structure of the formed tissue was investigated. The cells were identified as mesenchymal stem cells with a 98.3% CD73 and CD90 double-positive cell rate. The increase in mineralization capacity and expression of human enamel-dentin specific transcripts proportional to the culture period were determined after differentiation. Six weeks after transplantation, an osteo-dentin matrix was formed in the group in which odontogenic differentiation was stimulated, and the odontogenic characteristics of the matrix were confirmed by histological examination and RT-PCR analysis. Odontogenic differentiation of the isolated and characterized human DPSC was improved with medium modification by the addition of BMP2 in vitro and in vivo. The defined medium and applied technique have a potential use for forming reparative dentin in the future, but the effects of the method should be investigated in long-term studies.

In vivo performance of different scaffolds for dental pulp stem cells induced for odontogenic differentiation

Abstract This study was designed to determine the in vivo performance of three different materials as scaffolds for dental pulp stem cells (DPSC) undergoing induced odontogenic differentiation. An odontogenic medium modified by the addition of recombinant human bone morphogenetic protein 2 was used in the experimental groups to induce differentiation. Mesenchymal stem cell medium was used in the control groups. DPSC were transplanted onto the backs of mice via three scaffolds: copolymer of L-lactide and DL-lactide (PLDL), copolymer of DL-lactide (PDL) and hydroxyapatite tricalcium phosphate (HA/TCP). The expression levels of dentin sialo-phosphoprotein (DSPP), dentin matrix protein-1 (DMP1), enamelysin/matrix metalloproteinase 20 (MMP20) and phosphate-regulating gene with homologies to endopeptidases on X chromosome (PHEX) were analysed using RT-PCR. The expressions in the experimental groups were compared to those in the control groups. The transcript expressions at 6 and 12 weeks were significantly different for all scaffolds (p < 0.05), except for the expression of DSPP in the PLDL group with regard to the time variable. Although there was a decrease in the expression of enamelysin/MMP20 in PLDL and HA/TCP at 12 weeks, all other expressions increased and reached their highest level at 12 weeks. The highest DSPP expression was in the PDL group (p < 0.05). The highest expression of DMP1 was detected in the HA/TCP group (p < 0.05). The highest expression of PHEX was in the PLDL group (p < 0.05). Consequently, PLDL and PDL seemed to be promising scaffold candidates for odontogenic regeneration at least as HA-TCP, when they were applied with the DPSC induced for odontogenic differentiation.

The protective effect of resveratrol against dentin bonding agents-induced cytotoxicity.

This study was designed to evaluate the cytotoxicity of four dentin bonding agents and the effects of an antioxidant addition. Group A: G-aenial Bond, Group B: Optibond All in One, Group C: Gluma Self Etch and Group D: Clearfil S(3) Bond were added to the medium using extract method. The cells were cultured with or without resveratrol (RES) addition. MTT, reactive oxygen species (ROS), DCF, Comet and 8-OHdG measurements were performed. The agents had a dose-dependent (1:1>1:10>1:20) cytotoxic effect. Considering 1:10 concentration; Group D at 1 h (p<0.01) and Group B and D at 24 h had the weakest cytotoxic effect (p<0.05). After RES addition, the highest cell viability was determined in Groups B+RES and D+RES at 1 h and in Groups A+RES and B+RES at 24 h (p<0.01). The dentin bonding agents induced ROS production and DNA damage regarding to their composition. However, RES addition decreased the indicated parameters.

The prevalence and consequences of burnout on a group of preclinical dental students.

OBJECTIVE: The aim of this study is to investigate the prevalence of burnout among a group of Turkish preclinical dental students, to compare the level of burnout and to determine the consequences in structural equation model. MATERIALS AND METHODS: Preclinical dental students (n = 329, 50.5% of females and 49.5% of males) aged between 18 and 24 took part in the study. Maslach burnout inventory student version, academic satisfaction scale, and personal information sheet were used to gather data. Pearson correlation analyses, t-test, and one-way ANOVA were used for statistical analysis. The proposed theoretical model was tested via observed variable path analysis using maximum likelihood parameter estimation with AMOS 7.0. RESULTS: About 22.3% of students had high level of emotional exhaustion, 16.7% of students had high level of cynicism, and 17.9% of students suffered from high level of reduced academic efficacy. While the students attending the first grade reported higher level of reduced academic efficacy, the students in the third grade reported higher level of emotional exhaustion. Academic workload played an important role in the development of burnout. As consequences of burnout, students with high levels of burnout intended to change their current major and did not to plan to continue to postgraduate education. Students with high level of burnout reported less level of academic satisfaction and academic achievement. CONCLUSIONS: Creating awareness on the burnout of dental students from the preclinical period may be useful for prevention and more compatible dental education environment.

Tideglusib protects neural stem cells against NMDA receptor overactivation.

BACKGROUND: N-methyl-d-aspartate (NMDA) receptors are major pharmacological targets to prevent or reduce the progression of neurodegenerative diseases. Successful therapy with NMDA receptor antagonists in humans has been limited by the severe side effects of complete receptor blockade. The aim of the present study was to investigate the possible protective effects of tideglusib against NMDA receptor overactivation in neural stem cells. METHODS: We measured the alteration in membrane integrity, free radical generation, intracellular Ca(2+) accumulation, mitochondrial membrane potential (MMP)/mitochondrial morphology and glycogen synthase kinase-3 (α/ß isoforms and phospho-GSK-3α/ß) protein expression levels following treatments. RESULTS: NMDA treatment, with or without d-serine, significantly increased LDH leakage and triggered cell death in neural stem cells. Reactive oxygen species (ROS) formation and intracellular Ca(2+) levels were increased following NMDA receptor overactivation. The significant reduction in MMP was found in NMDA/d-serine-treated cells. Tideglusib significantly decreased ROS production and membrane degradation, but did not change intracellular Ca(2+) levels following NMDA receptor activation. Both in the presence or in the absence of NMDA/d-serine, tideglusib increased MMP and the levels of phospho-GSK-3ß in NSCs. Moreover, GW9662 (a peroxisome-proliferator-activated receptor gamma (PPARγ) antagonist) treatment significantly inhibited the protective effect of tideglusib in NMDA/d-serine-treated cells. CONCLUSION: Our study provides the evidence that GSK-3ß and PPARγ may be directly involved in pathways leading to NMDA receptor-induced cell death and that the inhibitors including tideglusib may exert neuroprotective effect against these receptor overactivation.

Effects of resveratrol on hydrogen peroxide-induced oxidative stress in embryonic neural stem cells.

Resveratrol, a natural phenolic compound, has been shown to prevent cardiovascular diseases and cancer and exhibit neuroprotective effects. In this study, we examined the neuroprotective and antioxidant effects of resveratrol against hydrogen peroxide in embryonic neural stem cells. Hydrogen peroxide treatment alone increased catalase and glutathione peroxidase activities but did not change superoxide dismutase levels compared with hydrogen peroxide + resveratrol treatment. Nitric oxide synthase activity and concomitant nitric oxide levels increased in response to hydrogen peroxide treatment. Conversely, resveratrol treatment decreased nitric oxide synthase activity and nitric oxide levels. Resveratrol also attenuated hydrogen peroxide-induced nuclear or mitochondrial DNA damage. We propose that resveratrol may be a promising agent for protecting embryonic neural stem cells because of its potential to decrease oxidative stress by inducing higher activity of antioxidant enzymes, decreasing nitric oxide production and nitric oxide synthase activity, and alleviating both nuclear and mitochondrial DNA damage.

Replantation after traumatic avulsion.

The aim of this report is to present the case of an accidentally avulsed maxillary central incisor kept in saline solution from the moment of trauma until its replantation 3 h later in a 13-year-old girl. The avulsed tooth was replanted back into the alveolar socket and splinted with composite resin. Calcium hydroxide intracanal dressing was used to prevent inflammatory root resorption. Radiographic and clinical examinations were performed during 27 months follow-up. During the 15 months follow-up period, the tooth remained in a stable functional position and did not reveal replacement resorption. But mild infraocclusion and root resorption were developed 21 months after replantation. The amount of damage to tooth and supporting structures, emergency treatment and follow-up period play a role in the prognosis of the avulsed tooth. It can be recommended to keep the avulsed tooth in saline solution at least when more appropriate storage media are not on handle immediately.

Susceptibility of enamel treated with bleaching agents to mineral loss after cariogenic challenge.

Objectives. Controversial reports exist whether bleaching agents cause a susceptibility to demineralization. The aim of this study was to compare the calcium loss of enamel treated with different bleaching agents and activation methods. Method and Materials. The specimens obtained from human premolars were treated in accordance with manufacturer protocols; 10% carbamide peroxide, 38% hydrogen peroxide light-activated, 38% hydrogen peroxide laser-activated, and no treatment (control). After cariogenic challenge calcium concentrations were determined by Inductively Coupled Plasma Mass Spectrometry. Results. No differences were found between the calcium loss of the laser-activated group and 10% carbamide peroxide group (p > 0.05). However, the differences between laser-activated and control groups were statistically significant (p < 0.05). The differences between 10% carbamide peroxide and the control group were not significant (p > 0.05). On the other hand, the light-activated group showed a significantly higher calcium loss compared with the other groups (p < 0.05). Conclusions. The results show that bleaching agents may cause calcium loss but it seems to be a negligible quantity for clinical aspects.