Effect of degree of conversion on the surface properties of polymerized resin cements used for luting glass fiber posts.

STATEMENT OF PROBLEM: Lack of conversion of resin cements for luting glass fiber posts in deeper levels of the root canal may compromise clinical performance. PURPOSE: The purpose of this in vitro study was to evaluate the effect of the degree of conversion on the surface properties of dual-polymerized resin cements used for cemented glass fiber posts according to the root level. MATERIAL AND METHODS: Fifty maxillary central incisor teeth were endodontically treated, and glass fiber posts were cemented using the following systems: self-adhesive dual-polymerized resin luting cement (RelyX U200) and dual-polymerizing flowable core and a post luting system (Rebilda DC) with a self-etching adhesive (Futurabond DC). The degree of conversion was determined via attenuated total reflectance and Fourier transform infrared spectroscopy, and surface microhardness and cement film thickness were measured. The intraradicular fit was evaluated with microscopy. All tests were performed in the coronal, middle, and apical third of the root canal. Statistical analysis was done with ANOVA and the multiple comparison Tukey test (α=.05). RESULTS: The degree of conversion was higher in the coronal third using Rebilda DC (65.3 ±4.8%) than RelyX U200 (38.7 ±5.3%) (P<.05); on both resin cements, these values decreased from the coronal to the apical third (30.9 ±3.7%, 61.9 ±8.7%, respectively). The cement film thickness was higher for RelyX U200 in the 3 thirds than for Rebilda DC; significant differences (P<.05) were recorded in both cementing systems in the coronal and apical thirds. In the middle third, no significant differences were observed (P>.05). The mean surface microhardness values increased in the coronal thirds and decreased with increasing root canal depth. The marginal seal in the coronal thirds and the intraradicular fit in the middle thirds showed closer adaptation; however, some tags were observed in the interface resin cement and radicular dentin. Gap and tag formations were observed in the apical third. CONCLUSIONS: Depending on the root canal third, the surface properties of dual-polymerized resin cements are influenced by the degree of conversion.

Effect of short fiber-reinforced composite combined with polyethylene fibers on fracture resistance of endodontically treated premolars.

STATEMENT OF PROBLEM: Whether direct coronal restorations of endodontically treated teeth with short fiber-reinforced composite combined with polyethylene fibers provide adequate mechanical strength is unclear. PURPOSE: The purpose of this in vitro study was to compare the fracture strength of endodontically treated premolars with standardized mesio-occluso-distal (MOD) preparations restored with short fiber-reinforced composite (SFRC) combined with polyethylene Ribbond fibers (PRFs). MATERIAL AND METHODS: A total of 40 premolars were selected and distributed into 4 groups (n=10) as follows: group restored with SFRC (EverX Posterior), group restored with PRF (Ribbond fibers), and group restored with the combination PRF+SFRC, all followed by a conventional composite resin (IPS Empress Direct). MOD preparations and endodontic treatments were prepared except in the control group (intact teeth). MOD preparations and endodontic treatments were prepared except in the control group (intact teeth). Specimens were loaded using a universal testing machine until fracture occurred at a crosshead speed of 0.5 mm/min, and the failure type and fracture patterns was reported descriptively. The mean values of the groups were analyzed by using the Shapiro-Wilk test and 1-way ANOVA tests (α=.05). RESULTS: Restoration with PRF+SFRC provided the highest mean ±standard deviation fracture resistance (288.2 ±73.5 N). Restoration with just PRF had the lowest values (192.4 ±25.4 N), which were statistically different from those of SFRC and PRF+SFRC (P<.05). The predominant mode of failure was mixed, and all fracture patterns were favorable. CONCLUSIONS: Reinforcing endodontically treated premolars with MOD cavities with Ribbond fibers followed by a conventional composite resin enhanced fracture resistance and may be suitable for the direct coronal restoration of large posterior cavities in stress-bearing areas.

A homemade simulation model improves the impact of e-learning for the practical administration of dental anaesthesia.

INTRODUCTION: A simulation model improves the learning of dental anaesthesia in dental students. This study explored first, the making at home of a dental anaesthesia simulation model by dental students, and second, the impact of that simulation model on the learning of dental students following an online course. We compared the level of knowledge, the level of perception of confidence to perform the basic injection technique (BIT) of dental anaesthesia, and the level of attitude towards e-learning of the BIT between a group of dental students who had an online course with a home-made dental anaesthesia simulation model (HMDASM) and a group of dental students who did not use that model. MATERIALS AND METHODS: A group of participants (n = 28) used the HMDASM to learn the BIT with an e-learning course. Another group of participants (n = 28) followed the same e-learning course, but that group used a lemon to practise the BIT. The two groups answered questionnaires that explored the level of theoretical knowledge on the BIT, the level of perception of confidence to perform the BIT, and the level of attitude towards e-learning of the BIT. Questionnaire scores from each group were compared by a Student's t-test (p ≤ .05). RESULTS: The group that used the HMDASM had a level of knowledge similar to that of the other group (p > .05). The group that used the HMDASM had a level of perception of confidence to perform the BIT and a level of attitude towards online learning of the BIT higher than those of the group that did not use the simulation model (p < .05). CONCLUSION: The use of a HMDASM had a positive effect on dental students following an online course to learn the BIT.

Synthesis of a PVA drug delivery system for controlled release of a Tramadol-Dexketoprofen combination.

The local administration of analgesic combinations by means of degradable polymeric drug delivery systems is an alternative for the management of postoperative pain. We formulated a Tramadol-Dexketoprofen combination (TDC) loaded in poly(vinyl alcohol) (PVA) film. Films were prepared by the solvent casting method using three different molecular weights of PVA and crosslinking those films with citric acid, with the objective of controlling the drug release rate, which was evaluated by UV-vis spectrometry. Non-crosslinked PVA films were also evaluated in the experiments. Differential scanning calorimetry (DSC) analysis of samples corroborated the crosslinking of PVA by the citric acid. Blank and loaded PVA films were tested in vitro for its impact on blood coagulation prothrombin time (PT) and partial thromboplastin time (PTT). The swelling capacity was also evaluated. Crosslinked PVA films of higher-molecular weight showed a prolonged release rate compared with that of the lower-molecular-weight films tested. Non-crosslinked PVA films released 11-14% of TDC. Crosslinked PVA films released 80% of the TDC loaded (p < 0.05). This suggests that crosslinking films can modify the drug release rate. The blank and loaded PVA films induced PT and PTT in the normal range. The results showed that the polymeric films evaluated here have the appropriate properties to allow films to be placed directly on surgical wounds and have the capacity for controlled drug release to promote local analgesia for the control of postoperative pain.

Glass coatings to enhance the interfacial bond strength between veneering ceramic and zirconia.

The purpose of this study was to investigate the tensile bond strength (TBS) and shear bond strength (SBS) between a zirconia core and fluoroapatite-pressed ceramic after the application of glass 46SP6 and AP40 via the ISO-17095:2013 methodology. Sintered zirconia beams (n = 120) were divided into four groups: (a) control: no treatment; (b) ZirL: IPS-E max ceram ZirLiner coating; (c) glass AP40 coating; and (d) glass 46SP6 coating. A fluoroapatite ceramic (IPS e.max Zir Press, Ivoclar Vivadent) beam was injected perpendicularly on top of each zirconia (Zenostar, Wieland Dental) beam forming a cross-bonded specimen. All groups were sub-divided into two for tensile and shear bond strength tests using a universal testing machine. Data were analyzed using the Kruskal-Wallis, Pearson Chi2, and Mann-Whitney U test (α = 0.05). The failure modes were measured using a stereomicroscope for each group. Scanning electron and atomic force microscopy were also employed. Zirconia surface modification with glass AP40 showed higher TBS values followed by the ZirL group with statistical differences (p < 0.05). SBS values showed no statistical differences between the groups. AFM analysis showed higher roughness values (Ra) in the 46SP6 and AP40 groups (p < 0.05). Glass coating AP40 exhibited promising bond strength results between zirconia and fluorapatite veneering ceramic, making it better for chemical and mechanical interlocking which may improve bilayered restorations longevity.

Learning of the mental nerve block technique with dental anaesthesia simulation models builds motor skills and confidence in dental students.

INTRODUCTION: We compared the motor learning, self-confidence whilst performing an anaesthesia technique and the perception of confidence between a group of students trained (G1) with two distinct dental anaesthesia simulation models (DASM) and a group of students (G2) not trained with DASM. MATERIALS AND METHODS: The G1 students (n = 22) were trained with a learning protocol including a DASM for simulating a puncture and a DASM for simulating an injection of dental anaesthesia. The G2 students (n = 22) received no such training. Both groups performed the mental nerve block (MNB) in a clinical setting, after which the average working time (motor learning), number of times help was requested for performing the MNB (self-confidence) and the scores of a Likert Scale questionnaire (perception of confidence) between the groups were compared with a t test. RESULTS: Compared with G2, the G1 students showed a shorter average working time (G1, 7:30 ± 0:54 min; G2, 9:06 ± 2:27 min; P = .017). Hence, G1 students had better motor skills. They also requested help when performing the MNB fewer times than the G2 students (G1, 2.2 ± 0.5 times; G2, 4.6 ± 1.95 times; P < .001). On the other hand, the G1 students demonstrated better perception of confidence (Likert Scale questionnaire) when performing the MNB compared with the G2 students (P = .007). CONCLUSION: The learning protocol with two different DASMs had a positive effect on the motor skills and the confidence of dental students performing the mental nerve block.

Calcium sustained release, pH changes and cell viability induced by chitosan-based pastes for apexification.

We explored chitosan-based sustained release pastes for apexification. The study aimed to formulate chitosan-based pastes loaded with calcium hydroxide (CH) or with calcium chloride (CC), and to evaluate the sustained release of Ca2+ and pH changes in deionized water as well as the effect of the pastes on cell viability. The pastes were formulated by dissolution of the chitosan in 1% or 2% acetic acid (AAC) plus the addition of CH or CC, then were suspended in deionized water for 50 days; the released Ca(II) and pH were measured with an electrode probe. The effect of the pastes on viability of human dental pulp cells was evaluated with a MTS assay. The results showed that the pastes prepared with 1% and 2% AAC and loaded with CH released a 74.9% and a 76.1% of the Ca2+ content, respectively, while the pastes prepared with 1% and 2% AAC loaded with CC released a content of Ca2+ of 90.8% and 76.6%, respectively. A control paste (CH and polyethylene glycol) released a 95.4%; significant statistical differences were found between the percentage of the experimental pastes and the control. The CH-loaded pastes caused an alkaline pH at the starting of the study, but the pH became neutral at the ending. The pH of the CC-loaded pastes was neutral at the starting and was acid at the ending. The pastes no affected on the cell viability. The chitosan-based pastes showed a suitable sustained release profile and cytocompatibility.

Bioethical Issues in Conducting Pediatric Dentistry Clinical Research.

Pediatric clinical research on new drugs and biomaterials involves children in order to create valid and generalizable knowledge. Research on vulnerable populations, such as children, is necessary but only admissible when researchers strictly follow methodological and ethical standards, together with the respect to human rights; and very especially when the investigation cannot be conducted with other population or when the potential benefits are specifically for that age group. Clinical research in Pediatric Dentistry is not an exception. The aim of the present article was to provide the bioethical principles (with respect to the child/parents' autonomy, benefit/risk analysis, and distributive justice), and recommendations, including informed consent, research ethics committees, conflict of interest, and the "equipoise" concept. Current and future worldwide oral health research in children and adolescents must be conducted incorporating their perspectives in the decision-making process as completely as possible. This concept must be carefully considered when a dental clinical study research is going to be planned and conducted, especially in the case of randomized controlled trials, in which children will be recruited as participants.

Cell viability and hemocompatibility evaluation of a starch-based hydrogel loaded with hydroxyapatite or calcium carbonate for maxillofacial bone regeneration.

The objective of this study is to evaluate the cell viability and hemocompatibility of starch-based hydrogels for maxillofacial bone regeneration. Seven starch-based hydrogels were prepared: three loaded with 0.5, 1 and 2% calcium carbonate (Sigma Aldrich, St. Louis, MO, USA); three loaded with 2, 3 and 4% hydroxyapatite (Sigma Aldrich); and one not loaded as a control. A 10 M NaOH was then added to induce hydrogel formation. Human osteoblasts were cultured on each hydrogel for 72 h. An MTS assay (Cell Titer96; PROMEGA, Madison, WI, USA) was used to assess cell viability. Hemocompatibility testing was conducted with normal human blood in the following conditions: 100 mg of each hydrogel in contact with 900 µL of whole blood for 15 min at 37 °C under lateral stirring. Higher percentages of cell viability were observed in starch-based hydrogels loaded with hydroxyapatite as compared with the control. The hemolysis test showed a hemolysis level lower than 2%. Activated partial thromboplastin time and prothrombin time were unchanged, while platelet counting showed a slight decrease when compared with controls.

Sustained release of calcium hydroxide from poly(DL-lactide-co-glycolide) acid microspheres for apexification.

Calcium hydroxide (CH) loaded poly(DL-lactide-co-glycolide) acid (PLGA) microspheres (MS) might be used for apexification requiring a sustained release of Ca(2+). The aim of this study was to formulate and characterize CH-PLGA-MS. The CH-loaded MS were prepared by either oil-in-water (O/W) or water-in-oil/in-water (W/O/W) emulsion solvent evaporation technique. MS produced by the O/W technique exhibited a larger diameter (18.63 ± 7.23 µm) than the MS produced by the W/O/W technique (15.25 ± 7.37 µm) (Mann-Whitney U test P < 0.001). The CH encapsulation efficiency (E e) and Ca(2+) release were calculated from data obtained by absorption techniques. Ca(2+) release profile was evaluated for 30 days. To know the E e, the CH-loaded MS were dissolved in 1 M NaOH to release all its content and a Ca(2+) colorimetric marker was added to this solution. The reagent marked the Ca(2+) in blue color, which was then measured by a UV-Vis system (650 nm). The percentage of E e was calculated on the basis of the theoretical loading. The E e of the O/W-produced MS was higher (24 %) than the corresponding percentage of the W/O/W-produced MS (11 %). O/W- and W/O/W-produced MS released slower and lower Ca(2+) than a control CH paste with polyethylene glycol 400 (Kruskal-Wallis test). O/W-produced MS released higher Ca(2+) than W/O/W-produced MS (statistically significant differences; P < 0.05). In conclusion, the CH-PLGA-MS were successfully formulated; the technique of formulation influenced the size, encapsulation efficiency and release profile. The MS were better sustained release system than the CH paste.

Eugenol Toxicity in Human Dental Pulp Fibroblasts of Primary Teeth.

OBJECTIVE: The aim of the study was to determine the eugenol concentrations at which toxicity occurs in human dental pulp fibroblasts of primary teeth. STUDY DESIGN: Samples of primary dental pulp tissue were taken. Tissue samples were seeded by means of explant technique and used in the 4(th)-5th pass. Single Cell Gel Electrophoresis (Comet), phenazine MeThoSulfate (MTS), LIVE/DEAD Cell Viability/Toxicity and trypan blue assays for evaluation of the cytotoxicity of increasing concentrations of eugenol (0.06 to 810 µM) were performed. RESULTS: The results of toxicity tests showed toxic effects on dental pulp fibroblasts, even at very low concentrations of eugenol (0.06 µM). Very low concentrations of eugenol produce high toxicity in human dental pulp fibroblasts. CONCLUSIONS: All of the concentrations of eugenol that we evaluated produced high toxicity in human dental pulp fibroblasts of primary teeth.

Sensory Neuropeptides and Endogenous Opioids Expression in Human Dental Pulp with Asymptomatic Inflammation: In Vivo Study.

PURPOSE: This study quantified the expression of substance P (SP), calcitonin gene-related peptide (CGRP), ß-endorphins (ß-End), and methionine-enkephalin (Met-Enk) in human dental pulp following orthodontic intrusion. METHODS: Eight patients were selected according to preestablished inclusion criteria. From each patient, two premolars (indicated for extraction due to orthodontic reasons) were randomly assigned to two different groups: the asymptomatic inflammation group (EXPg), which would undergo controlled intrusive force for seven days, and the control group (CTRg), which was used to determine the basal levels of each substance. Once extracted, dental pulp tissue was prepared to determine the expression levels of both neuropeptides and endogenous opioids by radioimmunoassay (RIA). RESULTS: All samples from the CTRg exhibited basal levels of both neuropeptides and endogenous opioids. By day seven, all patients were asymptomatic, even when all orthodontic-intrusive devices were still active. In the EXPg, the SP and CGRP exhibited statistically significant different levels. Although none of the endogenous opioids showed statistically significant differences, they all expressed increasing trends in the EXPg. CONCLUSIONS: SP and CGRP were identified in dental pulp after seven days of controlled orthodontic intrusion movement, even in the absence of pain.

Poly(2-dimethylamino ethylmethacrylate)-based polymers to camouflage red blood cell antigens.

Poly(2-dimethylamino-ethylmethacrylate) (PDMAEMA) is a cationic polymer when dissolved in a 7.4 pH fluid. Owing to its ionic nature, this polycation interacts with the negatively charged cell membrane surface of red blood cells (RBCs). The electrostatic self-assembly of PDMAEMA on RBCs membrane can be employed for inducing the formation of a polymeric shield camouflaging blood group antigens on RBCs as a valuable strategy for developing "universal RBCs" for blood transfusion. The purpose of this research was to evaluate the camouflaging ability of PDMAEMA homopolymers and PDMAEMA-co-poly(ethylene glycol) copolymers differing in molecular weight and architecture. Surprisingly, the PDMAEMAs caused a partially masking, no masking, and sensitization of the same RBCs population. The MW and architecture of the polymers as well as temperature of PDMAEMA-RBCs treatment influenced the results observed. Herein, the very particular reactivity of PDMAEMAs and RBCs is analyzed and discussed.

Bacterial Percolation and Sealer Tubular Penetration in a Polymer-based Obturation System Compared with Warm Vertical Condensation Technique: An in Vitro Study.

Introduction: This study compared bacterial percolation and sealer penetration of a novel obturation technique with the ones of warm vertical condensation technique. Methods and Materials: A bacterial percolation test was carried out with 80 single rooted human teeth divided into 5 groups; A (n=20): warm vertical condensation and AH-Plus, B (n=20): CPoint with AH-Plus, C (n= 20): CPoint with EndoSequence BC, +ve Control (n=10): teeth with no canal obturation, -ve Control (n=10): teeth with no access cavity. The samples were inoculated with a multispecies bacterial incoulum. Bacterial percolation was evaluated by turbidity. Confocal laser scanning microscopy (CLSM) was used to observe the presence of gaps and voids. Further 48 extracted human mandibular single-canal premolars were used to determine the sealer penetration. Slices of the samples were observed by CLSM to evaluate tubules penetration of the sealer. Kaplan Meyer survival, ANOVA one way and Tuckey HSD test and a Wilcoxon signed-rank test were utilised. Results: A Kaplan-Meier test showed no significant difference overall (P>0.05) between groups A, B and C. At 43 days, the group B showed a significantly inferior ability to prevent bacterial passage (P<0.05). The group C showed a deeper sealer penetration than group A and B with statistically significant differences (P<0.05) for the total penetration (ANOVA one way and Tukey HSD). A Wilcoxon signed-rank test showed statistically significant differences for the penetration in the middle-and apical third of the 3 groups. Conclusion: Based on this in vitro study, the single polymer-cone obturation technique with a resin based- and bioceramic based-sealer behaved similarly to the warm vertical obturation technique in preventing bacterial passage. The bioceramic sealer showed the deepest penetration but did not fully prevent bacterial leakage.

The effect of Emdogain and 24% EDTA root conditioning on periodontal healing of replanted dog's teeth.

Controversies still exist as for the regenerative role of enamel matrix derivatives and the need for removal of the periodontal ligament in replanted teeth. The purpose of this study was to evaluate the effect of Emdogain and 24% ethylenediamine tetraacetic acid (EDTA) root conditioning on periodontal healing of replanted dog's teeth. Teeth were extracted, endodontically treated and preconditioned as follows: group 1, Emdogain; group 2, Emdogain + EDTA and group 3, EDTA. Teeth were replanted after 30 min extraoral time, splinted for 15 days and animals sacrificed after 8 weeks of observation. Histological evaluation was performed using hematoxylin/eosin and Masson trichrome and results scored based on previously reported criteria for histological evaluation. Replacement root resorption was histologically diagnosed in all groups except in the negative control. A parametric analysis showed no statistically significant differences between experimental groups. Root preconditioning with Emdogain alone or in combination with 24% EDTA showed no evidence of regeneration of collagen fibers and consequently did not prevent the development of replacement root resorption on replanted dog's teeth.

Knowledge and attitudes of Mexican dentists regarding COVID-19 / Conocimiento y actitudes de dentistas mexicanos sobre la COVID-19

Dentists have a high risk of contracting COVID-19, they needed to be aware of the major challenge that represents the dental practice and COVID-19. Accordingly, this study aimed: 1) to investigate the knowledge of dentists regarding COVID-19, 2) to investigate the attitudes of dentists concerning the use of personal protective equipment and, 3) to investigate the attitudes of dentists on stopping their dental practices in the framework of a contingency plan for the COVID-19 outbreak. An online cross-sectional survey was applied to dentists (n=822). Dentists in Mexico answered the survey, which was administered before the contingency plan for the COVID-19 outbreak. Results were analyzed with descriptive statistics and with a Chi-square test (P≤0.05). Of the respondents, 99% of dentists indicated knowing what COVID-19 is, knowing most, but not all, of its signs and symptoms and knowing its mode of transmission. The 89% of dentists indicated that they always used personal protective equipment. But they did not use always wear face masks, protective eyewear, face shields, disposable gowns, and caps. Dentists were aware of the risk of performing dental procedures during the COVID-19 outbreak. The 90% of dentists indicated that they would treat only patients requiring emergency treatment, and 10% indicated that they would not treat any patients. The dentists had limited knowledge about the COVID-19 disease. They did not use personal protective equipment consistently, and they indicated that they might continue working during the COVID-19 outbreak.

Durante la pandemia por COVID-19, los dentistas han tenido un alto riesgo de contraer COVID-19. Los dentistas mexicanos tuvieron la necesidad de enfrentarse a la COVID-19 en la práctica dental con un posible conocimiento limitado sobre la enfermedad. De acuerdo con esa problemática, los objetivos de este estudio fueron: 1) investigar el conocimiento de los dentistas sobre la COVID-19, 2) investigar las actitudes de los dentistas sobre el uso de equipo de protección personal, 3) investigar las actitudes de los dentistas para detener la práctica laboral frente a la pandemia. Una encuesta fue aplicada a dentistas mexicanos en el inicio de la contingencia por COVID-19 (n=822). Se analizaron los resultados de con una prueba de Chi cuadrada (P≤0.05). El 99% de los participantes conocieron qué es la COVID-19, pero no todos los signos y síntomas de la enfermedad ni los modos de transmisión. El 89% de los dentistas indicaron que siempre usan equipo de protección personal. Pero no usan siempre careta, lentes de protección, cubreboca, guantes deshechables y gorro. Los participantes tenían conocimiento del riesgo de contraer COVID-19. El 90% indicó que sólo atenderían urgencias dentales y el resto indicó que no atendería pacientes. Los dentistas tuvieron un conocimiento limitado sobre la COVID-19. No usaron equipo de protección personal de forma consistente. Además indicaron que estarían dispuestos a seguir trabajando durante la pandemia.

Knowledge about COVID-19 and perception of health safety among mexican dental students / Conocimiento sobre COVID-19 y percepción de seguridad en la salud de estudiantes mexicanos de odontología

This study aimed: 1) to investigate sources of information used by students to learn about COVID-19, 2) to investigate levels of knowledge about COVID-19 and about conditions for the treatment of patients during the COVID-19 lockdown, and 3) to evaluate students' perceptions of safety regarding their return to in-person activities at the School of Dentistry. Dental students answered a questionnaire (29 items; n=371) that explored the aims of the study, based on a Likert scale (Cronbach's alpha, 0.778). Data were tested with the Mann-Whitney U test and Kendall's Tau-c. Dental students received information about COVID-19 from the Mexican Health Ministry as their first source (45.28%). Students had good knowledge about the main characteristics of COVID-19, and 59.3% of students had excellent knowledge about the factors relevant to dental treatment of patients. Half of the students said they felt safe regarding a possible return to in-person activities at the dental school, while the other half did not. Statistically significant differences were noted between the students' scholar year and their level of knowledge (P<0.001) and between their perception of safety (very unsafe, unsafe, safe, and very safe) and scholar year (P=0.000). Dental students had good knowledge about COVID-19 and about the dental care for patients during the lockdown. Half of the dental students felt unsafe about a possible return to in-person school activities.

Los objetivos del estudio fueron 1) investigar que fuentes de información usaron los participantes para conocer sobre la COVID-19, 2) evaluar cuál es el nivel de conocimiento que tienen sobre COVID-19 y la atención a pacientes durante la contingencia, y 3) evaluar la percepción de seguridad sobre el regreso a actividades presenciales en la facultad. Estudio transversal. Se aplicó un cuestionario en línea (29 ítems; n=371) que exploró cada objetivo e incluyó una escala de Likert (Alfa de Cronbach de 0.778). Los datos fueron analizados con las pruebas de U de Mann Whitney y con Tau-c de Kendall. La mayoría de los participantes obtuvieron información sobre la COVID-19 a través de la Secretaría de Salud (45.28%), tuvieron un conocimiento bueno sobre las generalidades de la COVID-19 y el 59.3% tuvo un conocimiento excelente sobre la atención a pacientes. La mitad de los encuestados tuvo una percepción de inseguridad en un posible regreso a actividades en la facultad. Hubo diferencia estadística significativa para la asociación entre año escolar y grado de conocimiento (p<0.001) y entre la percepción en la seguridad en el regreso a actividades (muy inseguro, inseguro, seguro y muy seguro) y el grado escolar (P=0.000). Los participantes tuvieron buen conocimiento sobre las generalidades de la COVID-19 y sobre la atención a pacientes en situación de contingencia. La mitad de los EO sienten inseguridad sobre un posible regreso a actividades.

Impact of Two Distinct Dental Anesthesia Simulation Models on the Perception of Learning by Students / Impacto de dos distintos modelos de simulación para anestesia dental en la percepción del aprendizaje en estudiantes

ABSTRACT We evaluated an infiltration anesthesia simulation model (IAM) and a conduction anesthesia simulation model (CAM) on the perception of learning by Mexican dental students. Our aim was to compare the perception of learning by dental students trained with two distinct dental anesthesia simulation model (DASM) with dental students who were not trained with a DASM. 3 groups participated in the study: G1 (N=12 students) learned to block the mental nerve (BMN) by participating in a theoretical lecture (stage 1) and a clinical demonstration (stage 2); G2 (N=12 students) learned the BMN by participating in the stage 1, stage 2, and training with the CAM; G3 (N=12 students) learned the BMN by participating in the stage 1, stage 2, and training with the IAM. The groups performed the BMN in a clinical exercise. Working-time of all participants was timed. Perception of learning for all participants was evaluated with a 5-point Likert Scale. The results showed that statistically significant differences were found between score of G1 and score of G2 and score of G3 (P<0.05). No statistically significant differences were found between scores of G2 and scores of G3. G1, G2 and G3 showed an average working-time of 12:42 minutes, 9.75 minutes and 8:03 minutes, respectively (P<0.05). We concluded that the IAM and CAM showed a positive impact on the perception of learning, and the students trained with the IAM showed a shorter working time compared with the students trained with the CAM.

RESUMEN En este estudio se evaluó el impacto de un modelo de simulación de anestesia dental por infiltración (IAM) y de un modelo de simulación de anestesia dental por bloqueo (CAM) en la percepción del aprendizaje en estudiantes mexicanos en estomatología. El objetivo fue comparar la percepción en el aprendizaje de estudiantes que entrenaron empleando dos distintos modelos de simulación de anestesia dental con estudiantes que no recibieron entrenamiento empleando algún modelo de simulación de anestesia dental. Participaron 3 grupos en el estudio: G1 (n=12) aprendieron el bloqueo del nervio mentoniano (BNM) al participar en una clase teórica (sesión 1) y en una demostración clínica (sesión 2); G2 (n=12) aprendieron la técnica de anestesia del BNM al participar en la sesión 1, sesión 2 y entrenando con el CAM; G3 (n=12) aprendieron la técnica del BNM al participar en la sesión 1, sesión 2 y entrenando con el IAM. Los grupos aplicaron la técnica del BNM en un ejercicio clínico. Se midió el tiempo de trabajo de los participantes. La percepción del aprendizaje de los participantes se evaluó con una Escala de Likert de 5 ítems. Los resultados mostraron diferencias estadísticamente significativas entre los valores del G2 y del G3 en comparación con el G1. No se encontraron diferencias estadísticas entre los valores del G2 y del G3. El tiempo de trabajo para el G1, G2 y G3 fue respectivamente de: 12:42 minutos, 9.75 minutos y 8:03 minutos, (P<0.05). Se concluyó que el IAM y el CAM mostraron un impacto positivo en la percepción del aprendizaje; los estudiantes entrenados con el IAM mostraron un tiempo de trabajo más corto en comparación con los estudiantes entrenados con el CAM.

Evaluation of decellularized matrix and ß-tricalcium phosphate as biomaterials for bone neoformation: in vivo study / Evaluación de la matriz descelularizada y ß-fosfato tricálcico como biomateriales para neoformación ósea: estudio in vivo

The aim of this study was to evaluate histologically the effect of two biomaterials, a biomaterial derived from porcine Urinary submucosa Bladder Matrix (UBM) and beta-TriCalcium Phosphate (ß-TCP), on bone defects. Twenty male New Zealand rabbits were used; the models were divided in two groups: the UBM group; the ß-TCP group, and a Negative Control (NC) group. Five-mm defects were created in the femur of each model and then the different biomaterials were set in place depending on each group. At 4 and 8 weeks, the animals in the models were sacrificed and samples of the defect site were collected to perform a Hematoxylin and Eosin stain (H&E). Histologically, ß-TCP group at 4 and 8 weeks presented neoformation of bone-like and cartilage-like tissue, with the presence of inflammatory infiltrate; at 4 and 8 weeks, the UBM group presented neoformation of bone-like and cartilage-like tissue with a low presence of inflammatory infiltrate, and the NC group presented the formation of connective tissue and, in a low proportion, neoformation of bone tissue and cartilage. Both biomaterials, UBM and ß-TCP, exhibited the capacity to promote bone neoformation; however, the UBM-based biomaterial produced a better-organized tissue with a lower inflammatory response compared with the ß-TCP group.

El objetivo de este estudio fue evaluar histológicamente el efecto de dos biomateriales: derivado de matriz de submucosa de vejiga urinaria porcina (UBM) y b-fosfato tricálcico (ß-TCP) en defectos óseos. Veinte conejos macho de raza Nueva Zelanda fueron empleados para este estudio; los modelos fueron divididos en dos grupos: UBM, ß-TCP y un grupo control negativo. Se crearon defectos de 5 mm en el fémur de cada uno de los modelos y posteriormente se colocó el biomaterial correspondiente de acuerdo a cada uno de los grupos. A las 4 y 8 semanas los modelos fueron sacrificados y se tomaron muestras del sitio del defecto óseo para realizar una tinción de Hematoxilina y Eosina. Histológicamente el grupo de ß-TCP tanto a las 4 como a las 8 semanas mostró neoformación de tejido óseo y tejido cartilaginoso con presencia de infiltrado inflamatorio; el grupo de UBM a las 4 y 8 semanas presentó neoformación de tejido óseo, tejido cartilaginoso y un bajo infiltrado inflamatorio; el grupo control negativo presentó formación de tejido conectivo y en baja proporción neoformación de tejido óseo y cartílago. Ambos biomateriales, UBM y ß-TCP mostraron la capacidad de promover la neoformación de tejido óseo; sin embargo, el biomaterial basado en UBM produjo un tejido mejor organizado y un menor infiltrado inflamatorio en comparación con el ß-TCP.

Hemocompatibility assessment of poly(2-dimethylamino ethylmethacrylate) (PDMAEMA)-based polymers.

Poly(2-dimethylamino-ethylmethacrylate) (PDMAEMA), a cationic polymer, has been widely reported as a nonviral carrier. Despite the fact that the cytotoxicity of this polymer has been extensively studied, there is a lack of information about its blood compatibility. Hence, this work evaluates the hemocompatibility of free-form PDMAEMA homopolymers differing in molecular weight (Mw) with or without a poly(ethylene glycol) (PEG) sequence in the form of a palm tree-like structure. Poly(ethylenimine) (PEI) was used as a reference in order to compare its hemoreactivity. Hemagglutination, hemolysis, platelet number, blood coagulation, and the complement systems were assessed in normal human whole blood according to the ISO 10993-4. Results showed that Mw, concentration, and incubation time strongly affected the hemocompatibility of the polymers evaluated. Our in vitro observations highlight that PDMAEMA homopolymers interacted strongly with the surface of the red blood cells but not with the inner structure of the membrane, while PEI behaved in the opposite way. No clear correlation has been evidenced between PDMAEMA-induced hemagglutination, PEI-induced hemagglutination, and hemolysis. Interestingly, if these polyelectrolytes strongly affect the platelets and blood coagulation cascades in a dose dependent way, none of them significantly affects the complement system. Our work reveals new knowledge on the toxicology of 2 families of polycations largely explored for gene delivery and on their mechanisms of cellular and humoral interactions.