B.I. Cerda-Cristerna

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.

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 dogs 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 dogs teeth.

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.

Positive influence of a dental anaesthesia simulation model on the perception of learning by Mexican dental students

INTRODUCTION This study evaluated the influence of three-repetition training with a dental anaesthesia simulation model (DASM) on the perception of learning by dental students. MATERIALS AND METHODS Dental students who had never used a dental anaesthesia technique were randomly divided into two groups that were taught the anterior superior alveolar nerve infiltrative anaesthesia technique. Group 1 (G1; N = 10) followed a three-stage learning method: (i) theoretical lecture, (ii) clinical demonstration and (iii) DASM training, including three repetitions of the anaesthesia technique. Group 2 (G2; N = 10) followed only the 1st and 2nd stages. The students in both groups then performed the anaesthesia technique. The perception of the students was evaluated by four learning concepts. Each was evaluated with a 5-point Likert scale questionnaire. The average score of each item of the questionnaire for G1 was compared with that of G2. Statistically significant differences were identified with the Mann-Whitney test. The average working time of each group was timed and compared by Students t-test to identify possible statistically significant differences. RESULTS Students in G1 showed higher average scores of perception in controlling the handling of the dental syringe and confidence in performing the injection (P < 0.05) and showed an average working time shorter than that of the students in G2 (P < 0.05). CONCLUSION The DASM positively influenced the perception learning of the dental students; it increased their confidence and syringe handling ability, as well as skills to perform the injection of anaesthesia more quickly.

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), β-endorphins (β-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.

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.

Evaluation of Decellularized Matrix and ß-Tricalcium Phosphate as Biomaterials for Bone Neoformation: In vivo Study

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 ( β-TCP), on bone defects. Twenty male New Zealand rabbits were used; the models were divided in two groups: the UBM group; the β-TCP group, and a Negative Control (NC) group. Fivemm defects were created in the femur of each model and then the different biomaterials were set in place depending on each grou p. At 4 and 8 weeks, the animals in the models were sacrificed and samples of the defect site were collected to perform a Hematoxylin a nd E sin stain (H&E). Histologically, β-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 proporti n, neof rmation of bone tissue and cartilage. Both biomaterials, UBM and β-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 β-TCP group.