Diego Enrique Betancourt

The activity of matrix metalloproteinases (MMPs) plays a crucial role in the aging of the resin–dentin interface. The in situ action of MMP‐2 and MMP‐9 has been confirmed in the process of dentin‐collagen degradation. However, the involvement of dental pulp cells in MMP secretion as a response to oxidative stress induced by contact with resin monomers has not been fully elucidated. Myricetin (MYR), like proanthocyanidin (PAC), has antioxidant properties and may help prevent extracellular matrix degradation. The objective was to evaluate the effect of MYR on the MMP expression and activity in response to reactive oxygen species (ROS) increase induced by triethylene glycol dimethacrylate (TEGDMA) in human odontoblast–like cells (hOLCs). hOLCs differentiated from dental pulp mesenchymal stem cells were exposed to TEGDMA released from dentin blocks using a barrier model with transwell inserts for 18, 24, and 36 h. Intracellular oxidation was evaluated using the 2′,7′‐dichlorofluorescein probe. The effect of 600 μM MYR on the MMP‐2 and MMP‐9 expression was determined by reverse transcription‐quantitative polymerase chain reaction (RT‐qPCR). The extracellular MMP levels were quantified using enzyme‐linked immunosorbent assay, and their activation by means of a proteolytic fluorometric assay. The results were analyzed by one‐way analysis of variance and Tukey's post hoc test, p ≤ 0.05. TEGDMA exposure increased intracellular ROS and upregulated MMP‐2 and MMP‐9 mRNA in hOLCs (p < 0.001). The levels of MMPs increased significantly 24 h after TEGDMA exposure (p = 0.013). These secreted proteases exhibited high activation ability. MYR reduced ROS production and downregulated MMP expression and activity at both mRNA and protein levels, similar to the effect found for PAC, which was used as a control. A relationship was observed between MMP‐2 and MMP‐9 expression, secretion, and early activation with ROS increase due to TEGDMA exposure. MYR showed potential as a therapeutic strategy to control MMP expression and modulate redox imbalance, offering a protective effect on cellular response.

Background. The health emergency declaration owing to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has drawn attention toward nosocomial transmission. The transmission of the disease varies depending on the environmental conditions. Saliva is a recognized SARS-CoV-2 reservoir in infected individuals. Therefore, exposure to fluids during dental procedures leads to a high risk of contagion. Objective. This study aimed to develop an infection risk prediction model for COVID-19 based on an analysis of the settlement of the aerosolized particles generated during dental procedures. Materials and Methods. The settlement of aerosolized particles during dental aerosol-generating procedures (AGPs) performed on phantoms was evaluated using colored saliva. The gravity-deposited particles were registered using a filter paper within the perimeter of the phantom head, and the settled particles were recorded in standardized photographs. Digital images were processed to analyze the stained area. A logistic regression model was built with the variables ventilation, distance from the mouth, instrument used, area of the mouth treated, and location within the perimeter area. Results. The largest percentage of the areas stained by settled particles ranged from 1 to 5µm. The maximum settlement range from the mouth of the phantom head was 320cm, with a high-risk cutoff distance of 78cm. Ventilation, distance, instrument used, area of the mouth being treated, and location within the perimeter showed association with the amount of settled particles. These variables were used for constructing a scale to determine the risk of exposure to settled particles in dentistry within an infection risk prediction model. Conclusion. The greatest risk of particle settlement occurs at a distance up to 78cm from the phantom mouth, with inadequate ventilation, and when working with a high-speed handpiece. The majority of the settled particles generated during the AGPs presented stained areas ranging from 1 to 5µm. This model was useful for predicting the risk of exposure to COVID-19 in dental practice.

Background: The health emergency declaration owing to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has drawn attention toward nosocomial transmission. The transmission of the disease varies depending on the environmental conditions. Saliva is a recognized SARS-CoV-2 reservoir in infected individuals. Therefore, exposure to fluids during dental procedures leads to a high risk of contagion. Objective: This study aimed to develop an infection risk prediction model for COVID-19 based on an analysis of the dynamic behavior of aerosol particles generated during dental procedures. Materials and methods: The dispersion of aerosol particles during dental aerosol-generating procedures (AGPs) performed on phantoms was evaluated using colored saliva. The gravity-deposited aerosol particles were registered using filter paper within the perimeter of the phantom head and the settled particles were recorded in standardized photographs. Digital images were processed to analyze the stained area and the drops dimensions. A logistic regression model was built with the variables ventilation, distance from the mouth, instrument used, area of the mouth treated, and location within the perimeter area. Results: The largest percentage of aerosol particles ranged from 1 to 5 µm. The maximum settlement range from the mouth of the phantom head was 320 cm, with a high-risk cut-off distance of 78 cm. Ventilation, distance, instrument used, area of the mouth being treated, and location within the perimeter showed association with the amount of aerosol particles. These variables were used for constructing a scale to determine the risk of exposure to aerosol particles in dentistry within an infection risk prediction model. Conclusion: Contamination by disseminated aerosol particles represents a risk for the dental staff. Thus, it is advisable to improve ventilation and use biosafety measures. The need to implement new clinical and educational strategies was evident. This model is useful for predicting the risk of exposure to COVID-19 in dental practice.

Several studies have shown that the dentin-resin interface is unstable due to poor infiltration of resin monomers into the demineralized dentin matrix. This phenomenon is related to the incomplete infiltration of the adhesive system into the network of exposed collagen fibrils, mainly due to the difficulty of displacement and subsequent replacement of trapped water between interfibrillar spaces, avoiding adequate hybridization within the network of collagen fibrils. Thus, unprotected fibrils are exposed to undergo denaturation and are susceptible to cyclic fatigue rupture after being subjected to repetitive loads during function. The aqueous inclusions within the hybrid layer serve as a functional medium for the hydrolysis of the resin matrix, giving rise to the activity of esterases and collagenolytic enzymes, such as matrix metalloproteinases, which play a fundamental role in the degradation process of the hybrid layer. Achieving better interdiffusion of the adhesive system in the network of collagen fibrils and the substrate stability in the hybrid layer through different strategies are key events for the interfacial microstructure to adequately function. Hence, it is important to review the factors related to the mechanisms of degradation and stabilization of the hybrid layer to support the implementation of new materials and techniques in the future. The enzymatic degradation of collagen matrix, together with resin leaching, has led to seeking strategies that inhibit the endogenous proteases, cross-linking the denudated collagen fibrils and improving the adhesive penetration removing water from the interface. Some of dentin treatments have yielded promising results and require more research to be validated. A longer durability of adhesive restorations could resolve a variety of clinical problems, such as microleakage, recurrent caries, postoperative sensitivity, and restoration integrity.