Improving dental epithelial junction on dental implants with bioengineered peptides.

Introduction: The functionalization of titanium (Ti) and titanium alloys (Ti6Al4V) implant surfaces via material-specific peptides influence host/biomaterial interaction. The impact of using peptides as molecular linkers between cells and implant material to improve keratinocyte adhesion is reported. Results: The metal binding peptides (MBP-1, MBP-2) SVSVGMKPSPRP and WDPPTLKRPVSP were selected via phage display and combined with laminin-5 or E-cadherin epithelial cell specific peptides (CSP-1, CSP-2) to engineer four metal-cell specific peptides (MCSPs). Single-cell force spectroscopy and cell adhesion experiments were performed to select the most promising candidate. In vivo tests using the dental implant for rats showed that the selected bi functional peptide not only enabled stable cell adhesion on the trans-gingival part of the dental implant but also arrested the unwanted apical migration of epithelial cells. Conclusion: The results demonstrated the outstanding performance of the bioengineered peptide in improving epithelial adhesion to Ti based implants and pointed towards promising new opportunities for applications in clinical practice.

A Five-year Comparative Study of Perceived Stress Among Dental Students at Two European Faculties.

AIM: To compare the levels, causes and the impact of stress from cohort of fifthyear dental students in the Faculties of Dental Medicine in Plovdiv, Bulgaria and Montpellier, France. MATERIALS AND METHODS: The questionnaire we used comprised the modified version of the 56-item Dental Environment Stress (DES) questionnaire. It was completed by fifth-year undergraduate dental students in both faculties in 2011 and 2016, totaling 335 dental students. A five-point Likert scale was used to record the responses from the subjects. Statistical analysis was performed with STATA version 14.1 (StataCorp, College Station, USA) specialized software. RESULTS: The mean age of studied population was not significantly different between 2011 and 2016 (p=0.08). The common stress value per student was 1.74 (CI: 1.64; 1.84, range: 0.12; 4.50). It was higher in Plovdiv (1.79±0.81) than in Montpellier (1.63±0.66); it was statistically higher for girls (1.94±0.70) than for boys (1.49±0.77), and decreased between 2011 and 2016. A significant overall effect of the common mean stress was influenced by the town (p=0.008), year of study (p=0.003), gender (p=0.0001) and accommodation (p=0.01) of the student. CONCLUSION: Academicals and clinical factors of stress are prevailing stressors during education. The challenge is now to decrease the influence of both, without altering the quality of dental education. Regular discussions and debriefs about the clinical cases before and after clinical activity. Alternative methods of education and examination, such as interactive methods, could be considered in order to reduce the stress of theoretical exams.

Multiphoton Microscopy for Caries Detection with ICDAS Classification.

Dentin carious lesion is a dynamic process that involves demineralization and collagen denaturation. Collagen type I is the major protein in dentin and it has been investigated based on its optical properties. Multiphoton microscopy (MPM) is a nonlinear imaging technique that reveals the caries process using the collagen two-photon excitation fluorescence (2PEF) and its second-harmonic generation (SHG). Combining the histological and the International Caries Detection and Assessment System (ICDAS) classifications with nonlinear optical spectroscopy (NLOS), 2PEF and SHG intensities of enamel and dentin were highly altered during the caries process. It has been proven that the ratio SHG/2PEF is a relevant indicator of the organic matrix denaturation [Terrer et al.: J Dent Res 2016; 96: 574-579]. In the present study, a series of measurable signals is made to detect early stages of carious lesion according to the ICDAS classification and to explore the relationship between these measures and the ICDAS scale. Comparison of the efficiency of nonlinear optical signals for caries detection with the ICDAS classification is essential to evaluate their potential for clinical application. In our study, the use of the NLOS measured by MPM allowed us to monitor a quantitative parameter (SHG/2PEF ratio) according to the dentin carious lesion state (ICDAS and histological examination). Three coherent new groups were defined (ICDAS 0/1; ICDAS 2/3; ICDAS 4/5/6), where the carious process can be clearly described with a statistically significant decrease of the SHG/2PEF ratio.

Strategies For Immobilization Of Bioactive Organic Molecules On Titanium Implant Surfaces - A Review.

Numerous approaches have been used to improve the tissue-implant interface of titanium (Ti) and titanium alloy (Ti6Al4V). They all aim at increasing cell migration and attachment to the metal, preventing unspecific protein adsorption and improving post-implantation healing process. Promising methods for titanium and titanium alloy surface modification are based on the immobilization of biologically active organic molecules. New and interesting biochemical approaches to such surface modification include layer-by-layer deposition of polyelectrolyte films, phage display-selected surface binding peptides and self-assembled DNA monolayer systems. The present review summarizes the scientific information about these methods, which are at in vitro or in vivo development stages, and hopes to promote their future application in dental implantology and in oral and maxillofacial surgery.

Sprayed cells and polyelectrolyte films for biomaterial functionalization: the influence of physical PLL-PGA film treatments on dental pulp cell behavior.

Further development of biomaterials is expected as advanced therapeutic products must be compliant to good manufacturing practice regulations. A spraying method for building-up polyelectrolyte films followed by the deposition of dental pulp cells by spraying is presented. Physical treatments of UV irradiation and a drying/wetting process are applied to the system. Structural changes and elasticity modifications of the obtained coatings are revealed by atomic force microscopy and by Raman spectroscopy. This procedure results in thicker, rougher and stiffer film. The initially ordered structure composed of mainly α helices is transformed into random/ß-structures. The treatment enhanced dental pulp cell adhesion and proliferation, suggesting that this system is promising for medical applications.

Multiphoton imaging of the dentine-enamel junction.

Multiphoton microscopy has been used to reveal structural details of dentine and enamel at the dentin-enamel junction (DEJ) based on their 2-photon excited fluorescence (2PEF) emission and second harmonic generation (SHG). In dentine tubule 2PEF intensity varies due to protein content variation. Intertubular dentin produces both SHG and 2PEF signals. Tubules are surrounded by a thin circular zone with a lower SHG signal than the bulk dentine and the presence of collagen fibers perpendicular to the tubule longitudinal axis is indicated by strong SHG responses. The DEJ appears as a low intensity line on the 2PEF images and this was never previously reported. The SHG signal is completely absent for enamel and aprismatic enamel shows a homogeneous low 2PEF signal contrary to prismatic enamel. The SHG intensity of mantle dentine is increasing from the dentine-enamel junction in the first 12 µm indicating a progressive presence of fibrillar collagen and corresponding to the more external part of mantle dentine where matrix metallo-proteases accumulate. The high information content of multiphoton images confirms the huge potential of this method to investigate tooth structures in physiological and pathological conditions.

Perceived sources of stress in fifth year dental students--a comparative study.

INTRODUCTION: The term "stress" refers to the effect of certain external factors (physical or mental) on the individual's physical and psychological health. Stress is very high in dental medicine. It may well be generated by the process of training in dentistry. During their training dental students express high levels of stress and considerable stress-related symptoms such as physical problems, depression, obsessive-compulsive and personality disorders. The perceived stress can be dependent on socio-cultural factors. The type of personality, gender, emotional intelligence and other individual characteristics may also influence the stress effects. AIM: To determine the main sources of stress in students during their dental training and compare the level of stress fifth-year dental students experience in the Faculty of Dental Medicine, Plovdiv, Bulgaria and the Faculty of Dentistry in Montpellier, France. METHODS: We recruited in the study fifth-year students from the Faculty of Dental Medicine in Plovdiv, Bulgaria and the Faculty of Dentistry in Montpellier, France. The modified Dental Environment Stress (DES) questionnaire was used to assess the effect of the various stressors. The questionnaire survey was conducted between February and March 2008. RESULTS: The living arrangements domain indicates higher levels of stress in Bulgarian students compared to their French counterparts with significant statistical difference for all factors. In personal factors the highest levels of stress were found with respect to the reduced holidays during school year and financial problems. Exams were the highest stressor in academic work domain and for the survey as a whole. In educational environment factors the stressors with the highest significance were the interactions with patients, academic environment (for French students) and risk of cross transmitted infections (for Bulgarian students). The high stress during clinical work is related to completing the assigned clinical workload quota and the shortage of time for clinical work. CONCLUSIONS: The students from both faculties report the highest mean levels of stress are related to examinations and clinical factors. Bulgarian students experienced higher mean levels of stress compared to their French colleges. The differences in mean stress levels are associated with socio-cultural factors and variations in educational curriculums at both dental faculties.