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BACKGROUND: Primary Health Care (PHC) systems are pivotal in delivering essential health services during crises, as demonstrated during the COVID-19 pandemic. With varied global strategies to reinforce PHC systems, this scoping review consolidates these efforts, identifying and categorizing key resilience-building strategies. METHODS: Adopting Arksey and O'Malley's scoping review framework, this study synthesized literature across five databases and Google Scholar, encompassing studies up to December 31st, 2022. We focused on English and Persian studies that addressed interventions to strengthen PHC amidst COVID-19. Data were analyzed through thematic framework analysis employing MAXQDA 10 software. RESULTS: Our review encapsulated 167 studies from 48 countries, revealing 194 interventions to strengthen PHC resilience, categorized into governance and leadership, financing, workforce, infrastructures, information systems, and service delivery. Notable strategies included telemedicine, workforce training, psychological support, and enhanced health information systems. The diversity of the interventions reflects a robust global response, emphasizing the adaptability of strategies across different health systems. CONCLUSIONS: The study underscored the need for well-resourced, managed, and adaptable PHC systems, capable of maintaining continuity in health services during emergencies. The identified interventions suggested a roadmap for integrating resilience into PHC, essential for global health security. This collective knowledge offered a strategic framework to enhance PHC systems' readiness for future health challenges, contributing to the overall sustainability and effectiveness of global health systems.
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COVID-19 , Pandemias , Atención Primaria de Salud , Humanos , COVID-19/epidemiología , Atención Primaria de Salud/organización & administración , SARS-CoV-2 , Telemedicina/organización & administración , Liderazgo , Atención a la Salud/organización & administración , Resiliencia PsicológicaRESUMEN
BACKGROUND: Medical universities are responsible for educating and training healthcare workers. One of the fields significantly impacted by the pandemic is medical education. The aim of this study is to identify strategies for enhancing e-learning for active learning and finding solutions for improving its quality. METHODS: This mixed-method (quantitative-qualitative) research was conducted in 2023 at three selected universities in Mazandaran Province. In the quantitative phase, 507 students participated via stratified random sampling using a standard questionnaire. In the qualitative phase, data were collected through semi-structured interviews with 16 experts until data saturation was achieved. SPSS 21 and MAXQDA 10 software were used for data analysis. RESULTS: In the multivariate regression analysis, an increase of one point in the dimensions of student-teacher interaction, active time, immediate feedback, and active learning corresponded to an average increase in learning scores of 0.11, 0.17, 0.16, and 1.42 respectively (p≤0.001). After the final analysis in the qualitative phase, four main domains (infrastructure, resources, quantity of education, and quality of education) and 16 sub-domains with 84 items were identified. CONCLUSIONS: The greatest challenge in e-learning is the interaction and cooperation between students and teachers. The implementation of the identified strategies in this research could provide useful evidence for policymakers and educational administrators to implement interventions aimed at addressing deficiencies and enhancing e-learning.
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COVID-19 , Instrucción por Computador , Educación Médica , Humanos , COVID-19/epidemiología , Pandemias , Aprendizaje Basado en Problemas , Educación Médica/métodos , Docentes Médicos , Estudiantes de Medicina , Relaciones InterprofesionalesRESUMEN
BACKGROUND: This study aimed to evaluate the effect of dentin pretreatment by Dimethyl Sulfoxide (DMSO) on the bond strength and microleakage of a universal bonding agent to dentin. METHODS: Fifty-six dentinal discs (thickness = 2 mm) were obtained from the crowns of the human third molars. The disks were assigned into 4 groups and treated as follows; self-etch-control group: G-Premio universal adhesive was used in self-etch mode, total-etch-control: G-Premio universal adhesive was used in total-etch mode, self-etch-DMSO: Water-based DMSO (50% volume) was applied on the samples for 60 s followed by application of G-Premio universal adhesive in self-etch mode, and Total-etch-DMSO: The samples were etched, and then, water-based DMSO was applied on them for 60 s followed by the application of G-Premio universal adhesive in total-etch mode. Afterward, resin composite was placed on all samples and light-cured. The samples were kept in distilled water and subjected to 5000 thermal cycles. Microshear bond strength was measured using the universal testing machine and failure modes were analyzed using a stereomicroscope. Forty-eight human third molars were used for microleakage evaluation and a standardized class five cavity was prepared on the buccal surface of each tooth. The teeth were assigned into 4 groups and received aforementioned surface treatment and the cavities were filled with resin composite. After storing in water for 24 h, the samples were subjected to 5000 cycles of thermocycling and the microleakage level of the samples was evaluated using silver nitrate uptake at the bonded interface. Two-way ANOVA test was used to analyze the effect of bonding technique (self-etch/ total-etch) and DMSO pretreatment on the microshear bond strength and microleakage of G-Premio adhesive to dentin. RESULTS: Bonding technique had no effect on the bond strength values (p = 0.17) while DMSO pretreatment significantly decreased the microshear bond strength of the samples (p = 0.001). DMSO application increased microleakage significantly in total-etch (P-value = 0.02) while it had no effect in self-etch mode (P-value = 0.44). CONCLUSIONS: Pretreatment of dentin using 50% DMSO significantly reduced the bond strength of G-Premio Bond in both self-etch and total-etch modes. DMSO effect on microleakage depended on the etching technique; DMSO increased the microleakage level when the adhesive was used in total-etch mode while did not affect the microleakage in self-etch mode.
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Recubrimiento Dental Adhesivo , Cementos Dentales , Humanos , Dimetilsulfóxido/farmacología , Dimetilsulfóxido/química , Recubrimientos Dentinarios/química , Cementos de Resina/química , Recubrimiento Dental Adhesivo/métodos , Dentina , Resinas Compuestas/química , Agua/química , Ensayo de MaterialesRESUMEN
Due to their unique rheological and mechanical properties, bottlebrush polymers are inimitable components of biological and synthetic systems such as cartilage and ultrasoft elastomers. However, while their rheological properties can be precisely controlled through their macromolecular structures, the current chemical spectrum available is limited to a handful of synthetic polymers with aliphatic carbon backbones. Herein we design and synthesize a series of inorganic bottlebrush polymers based on a unique combination of polydimethylsiloxane (PDMS) and polyphosphazene (PPz) chemistry. This non-carbon-based platform allows for simple variation of the significant architectural dimensions of bottlebrush-polymer-based elastomers. Grafting PDMS to PPz and vice versa also allows us to further exploit the unique properties of these polymers combined in a single material. These novel hybrid bottlebrush polymers were cured to give supersoft, solvent-free elastomers. We systematically studied the effect of architectural parameters and chemical functionality on their rheological properties. Besides forming supersoft elastomers, the energy dissipation characteristics of the elastomers were observed to be considerably higher than those for PDMS-based elastomers. Hence this work introduces a robust synthetic platform for solvent-free supersoft elastomers with potential applications as biomimetic damping materials.
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BACKGROUND: Cancers, especially Upper Gastrointestinal Cancers (UGCs), pose a substantial burden on society, particularly in developing nations. Golestan province, Iran, is known for its high UGC rates globally. AIMS: This study delves into the disease burden of UGCs in the eastern part of Golestan province. METHODS AND RESULTS: This study was conducted using the results of the Golestan cohort study. 2711 patients participating in this cohort, who visited Atrak Clinic during 2001-2020, participated in this study. After excluding patients with incomplete records, 2481 patients were included in the study. To compute the metrics of years of life lost (YLL), years of life lived with disability (YLD), and disability-adjusted life years (DALY), we utilized the World Health Organization's standard life table, stratified by age and gender. The majority of UGC patients in our study were married (81.8%), had limited formal education (82.6%), and were predominantly male (61.1%). A substantial proportion resided in suburban areas (85.8%), and over half of the patients (52%) reported a history of drug addiction. The mean age at diagnosis for men was 65.76 years with a standard deviation of 11.34, while for women, it was 64.38 years with a standard deviation of 11.66. Regarding disease impact, YLL, YLD, and DALY for men were 21 240, 1956, and 23 196 (307.8 per 100 000), respectively. For women, these figures were 15 609 for YLL, 1367 for YLD, and 16 976 (223.1 per 100 000) for DALY. CONCLUSION: After the increasing trend of the burden of UGCs in Golestan province in the early years of the study, this rate has been decreasing in recent years. Effective strategies necessitate collaborative efforts across various sectors to alleviate this burden, focusing on preventive measures, timely diagnosis, and well-coordinated therapeutic interventions.
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Neoplasias Gastrointestinales , Humanos , Femenino , Masculino , Estudios de Cohortes , Neoplasias Gastrointestinales/epidemiología , Costo de Enfermedad , Irán/epidemiologíaRESUMEN
The aim of this study was to determine the challenges and opportunities of virtual education during the COVID-19 pandemic. This study was conducted in 2022-2023 with a mixed method. During the quantitative phase, we chose 507 students from Mazandaran Province medical universities (both governmental and non-governmental) by stratified random sampling and during the qualitative phase 16 experts were collected by purposive sampling until we reached data saturation. Data collecting tools consisted of questionnaires during the quantitative phase and semi-structured interview during the qualitative phase. Data was analyzed using SPSS21 and MAXQDA10. Mean scores of the total score was 122.28±23.96. We found a significant association between interaction dimension and background variables (P < 0.001). The most important privilege of virtual education is uploading the teaching material in the system so that students can access the material constantly and the most important challenge regarding virtual education is lack of proper network connection and limited bandwidth. Virtual education proved to be a suitable alternate to traditional methods of medical education during the COVID-19 pandemic in theoretical topics, we recommend that educational policymakers would take the necessary actions to provide the requirements and facilities needed to improve the quality of virtual education.
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COVID-19 , Educación a Distancia , Educación Médica , COVID-19/epidemiología , Humanos , Irán/epidemiología , Educación a Distancia/métodos , Encuestas y Cuestionarios , Educación Médica/métodos , Masculino , Femenino , Pandemias , SARS-CoV-2 , Adulto , Estudiantes de Medicina , Adulto JovenRESUMEN
Characterization of heterogeneous reservoirs such as multilayered or fractured systems is an important issue in different disciplines such as hydrology, petroleum and geothermal systems. One of the popular methods that can be used for this purpose is tracer tests. Better understanding of the mechanisms of mass transfer (convection-diffusion process) is essential for having a proper test interpretation. In this study, the solutions of different scenarios of tracer flow in a pair of high and low-permeable layered reservoirs including convection and diffusion mechanisms are discussed. Although analytical solutions generally provided exact solutions, they involve several assumptions and might be hard to use for complex problems. As a result, numerical methods are selected for the investigation of different scenarios and addressing cases that are beyond access of analytical methods. In this study, several scenarios of considering diffusion and convection in low and high permeable zones and effective parameters on tracer concentration are investigated. According to the results of this study, the higher the porosity ratio of low to high permeable layer, the more time is needed to get the final concentration value. Also, by increasing the value of the dispersivity coefficient, the time needed to increase the concentration decreases. In other words, the sharp increase in concentration for lower times is seen in higher dispersivity values. The concentration profile variation is affected by Peclet number. The difference among concentration profiles in different cases is considerable, especially in low Peclet numbers where the diffusion mechanism is dominant. This behavior is more common in low permeable mediums such as multilayered tight or shale reservoirs.
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BACKGROUND: Recently, the use of whitening dentifrice has increased among patients. However, these products might increase the surface roughness of composite restorations and make them more susceptible to discoloration and plaque accumulation. This study aimed to compare the effects of two charcoal-based dentifrices and other whitening dentifrices with different mechanisms of action on the surface roughness of an aged resin composite. METHODS: Forty-five composite specimens were made (2 × 7mm) and their initial surface roughness was obtained using a Profilometer. The specimens were subjected to the Accelerated Artificial Aging (AAA) process for 300 hours. Then, the surface roughness of the specimens was reevaluated using the Profilometer. The specimens were randomly divided into 5 groups (N.=9), namely Control (Gc), Bencer (Gb; Sormeh Company, Tehran, Iran), Perfect White Black (Gp), Colgate Total Whitening (Gt), and Colgate Optic White (Go) (Colgate-Palmolive Company, New York, NY, USA). The specimens were brushed for 14 minutes with respective dentifrices. In the Gc group, the specimens were only brushed with distilled water. The surface roughness of the specimens was measured again. The data were analyzed using repeated measure ANOVA at a significance level of 0.05. RESULTS: There was no significant difference in surface roughness parameters (Ra, Rq, Rz) between the groups, but in each group, the roughness parameters decreased after the aging procedure and increased after brushing significantly except for Rz parameter in Gb group which increased after aging and decreased after brushing. CONCLUSIONS: None of the whitening dentifrices used in the present study had an adverse effect on the surface roughness of an aged composite resin.
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Carbón Orgánico , Dentífricos , Anciano , Humanos , Envejecimiento , Carbón Orgánico/farmacología , Resinas Compuestas , IránRESUMEN
Aim: The present study investigated the effects of laser and conventional in-office bleaching, and polishing on the color of stained composite resin. Materials and Methods: A microhybrid composite (Clearfil AP-X) and a nanohybrid composite (Grandio) were selected. Twenty-four discs (2 × 10 mm) for each composite were prepared. The samples were immersed in coffee solution (25 g of coffee in 250 mL water) for seven days. Then the samples were divided into three groups (n = 8) and the stains were removed using bleaching (with Opalescence Xtra Boost), diode laser irradiation with Heydent material and a Sof-Lex polishing kit. The L ∗a ∗b ∗ color parameters were determined using a spectrophotometer before and after immersion and after stain removal procedures, and the overall color changes (ΔE) were calculated. The data were analyzed with two-way analysis of variance. Results: In the Clearfil composite resin group, the mean ΔE compared to the baseline using in-office bleaching, laser irradiation, and Sof-Lex polishing kit were 3.31, 3.35, and 4.93, respectively. These values with the Grandio composite resin were 3.31, 6.35, and 4.57, respectively. The highest capacity to remove stains was related to the conventional in-office bleaching method. Grandio composite resin underwent more color changes than Clearfil composite resin significantly (P-value < 0.05). Conclusion: Both composite resins exhibited color changes after immersion in the discoloring solution. However, after staining-removing procedures, the ΔE values decreased. Decreases in the ΔE values were not sufficient to restore the color to that before immersion in the discoloring solution with any stain-removing methods.
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Introduction: Recently, the application of laser-assisted bleaching has increased in dental practice. This method might affect the physical and chemical properties of resin composite and its monomer release. This study aimed to evaluate the effect of in-office, at-home, and laser-assisted bleaching on the monomer release (bisphenol A diglycidyl dimethacrylate (BisGMA), triethylene glycol dimethacrylate (TEGDMA), and urethane dimethacrylate (UDMA)) from aged nanohybrid (Grandio, Voco) and microhybrid (Clearfil AP-X Esthetics, Kuraray) resin composites. Methods: Thirty-two samples of each composite were prepared. The samples underwent aging procedure with UV light at 65°C for 100 hr. The samples were divided into 4 groups: OB: conventional in-office bleaching with Opalescence Boost PF 40% gel; HB: home bleaching with Opalescence PF 15% gel; LB: bleaching with JW Power bleaching gel followed by diode laser application; and C: control group without bleaching. Then, the samples were immersed in a solution containing 75% ethanol + 25% distilled water. The medium was renewed after 8, 16, 24 hr, and 7 days and was analyzed using high-performance liquid chromatography method to evaluate the monomer release. The data were analyzed using Two-way ANOVA and Post hoc Tukey test. Results: The bleaching method had no effect on TEGDMA and BisGMA release in both composites while it affected UDMA release in nanohybrid composite; UDMA release was significantly higher in LB compared to control and also higher in OB and LB compared to HB. No difference was observed in the microhybrid composite in this regard. Conclusion: Laser-assisted bleaching did not affect monomer release from microhybrid composite while it increased UDMA release from nanohybrid composite. The bleaching method had no effect on TEGDMA and BisGMA release.
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This study compares the cytotoxicity and antibacterial activity of five pulp capping liners. This in vitro study was conducted on Fuji II LC glass ionomer, Dycal, Calcimol LC, TheraCal LC, and ACTIVA BioACTIVE. For cytotoxicity, the (MTT) methyl thiazolyl tetrazolium assay was performed on 3 samples from each group of human dental pulp cells (HDPSCs) after 24 h of incubation. The direct contact test (DCT) for antibacterial activity, 6 samples (3 for each material, and 3 for negative control), from each liner were made to evaluate Streptococcus mutans (S. mutans), Lactobacillus casei (L. casei), and Lactobacillus acidophilus (L. acidophilus). Data were analyzed by one-way ANOVA and Tukey's post-hoc test (alpha = 0.05). Data analysis showed that the cytotoxicity of the materials was significantly different (p < 0.001). Fuji II LC and ACTIVA BioACTIVE showed strong cytotoxicity, TheraCal LC moderate cytotoxicity, and Dycal and Calcimol LC slight cytotoxicity. The analysis also revealed a significant difference among the materials regarding antibacterial activity (p < 0.001). Tukey's test showed that the mean percentage of reduction in colony count was significant for all liners compared with the positive control (p < 0.001). The mean percentage of reduction in colony count for Dycal was significantly greater than that of Fuji II LC (p = 0.014), Calcimol LC (p = 0.003), and TheraCal LC (p = 0.001). ACTIVA BioACTIVE did not significantly differ from the other materials as regards antibacterial activity. Dycal showed significantly higher antibacterial activity than the other materials.
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BACKGROUND: Electrical Impedance Tomography (EIT) is used as a fast clinical imaging technique for monitoring the health of the human organs such as lungs, heart, brain and breast. Each practical EIT reconstruction algorithm should be efficient enough in terms of convergence rate, and accuracy. The main objective of this study is to investigate the feasibility of precise empirical conductivity imaging using a sinc-convolution algorithm in D-bar framework. METHODS: At the first step, synthetic and experimental data were used to compute an intermediate object named scattering transform. Next, this object was used in a two-dimensional integral equation which was precisely and rapidly solved via sinc-convolution algorithm to find the square root of the conductivity for each pixel of image. For the purpose of comparison, multigrid and NOSER algorithms were implemented under a similar setting. Quality of reconstructions of synthetic models was tested against GREIT approved quality measures. To validate the simulation results, reconstructions of a phantom chest and a human lung were used. RESULTS: Evaluation of synthetic reconstructions shows that the quality of sinc-convolution reconstructions is considerably better than that of each of its competitors in terms of amplitude response, position error, ringing, resolution and shape-deformation. In addition, the results confirm near-exponential and linear convergence rates for sinc-convolution and multigrid, respectively. Moreover, the least degree of relative errors and the most degree of truth were found in sinc-convolution reconstructions from experimental phantom data. Reconstructions of clinical lung data show that the related physiological effect is well recovered by sinc-convolution algorithm. CONCLUSIONS: Parametric evaluation demonstrates the efficiency of sinc-convolution to reconstruct accurate conductivity images from experimental data. Excellent results in phantom and clinical reconstructions using sinc-convolution support parametric assessment results and suggest the sinc-convolution to be used for precise clinical EIT applications.
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Algoritmos , Procesamiento de Imagen Asistido por Computador/métodos , Fantasmas de Imagen , Radiografía Torácica/instrumentación , Tomografía/instrumentación , Impedancia Eléctrica , Humanos , Recién Nacido , Pulmón/diagnóstico por imagenRESUMEN
Background: The aim of the current study was to evaluate and compare the influence of Dycal, Lime-Lite, TheraCal LC, Biodentine, resin-modified glass ionomer cement (RMGIC), and Activa BioActive as the pulp capping material on the shear bond strength of resin composite to dentin. Methods: A total of 70 extracted caries-free molars were randomly assigned to seven groups. Six test groups were covered with various protective liners: Dycal, TheraCal LC, Lime-Lite, Activa BioActive, Biodentine, and RMGIC. The control group received no liner pretreatment. Each sample was bonded to resin composite using the total-etch Tetric N bond adhesive. The samples were then tested for shear bond strength using the universal testing machine at a cross-head speed of 1 mm/min until bond failure occurred. The data were analyzed using the one-way ANOVA test followed by the Tamhane post hoc test for pairwise comparisons of the groups. Results: Independent of the type of the applied liner, all groups exhibited inferior SBS to dentin compared to the control group. TheraCal and RMGIC showed significantly higher shear bond strength than Biodentine and Dycal, which showed the lowest shear bond strength. Lime-Lite and Activa also had significantly lower SBS results than TheraCal. The mode of fracture was predominantly cohesive in Dycal, Biodentine, and TheraCal and adhesive in Activa. Conclusion: This present study concludes that the bond strength of resin composite to dentin can be affected differently using various types of liners.
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Recubrimiento Dental Adhesivo , Cementos de Ionómero Vítreo , Resinas Compuestas/química , Dentina , Cementos de Ionómero Vítreo/química , Ensayo de Materiales , Diente Molar , Cementos de Resina/química , Resistencia al CorteRESUMEN
Fifth-generation (5G) cellular networks are state-of-the-art wireless technologies revolutionizing all wireless systems. The fundamental goals of 5G are to increase network capacity, improve data rates, and reduce end-to-end latency. Therefore, 5G can support many devices connected to the Internet and realize the Internet of Things (IoT) vision. Though 5 G provides significant features for mobile wireless networks, some challenges still need to be addressed. Although 5 G offers valuable capabilities for mobile wireless networks, specific issues still need to be resolved. This article thoroughly introduces 5G technology, detailing its needs, infrastructure, features, and difficulties. In addition, it summarizes all the requirements and specifications of the 5G network based on the 3rd Generation Partnership Project (3GPP) Releases 15-17. Finally, this study discusses the key specifications challenges of 5G wireless networks.
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Tecnología InalámbricaRESUMEN
PURPOSE: Considering the suggested advantages of cold atmospheric plasma (CAP) in increasing the fluoride uptake by the enamel, this study aimed to assess enamel erosion following the application of helium CAP and two types of fluoride varnishes. METHODS: The microhardness of 70 bovine enamel specimens was measured using a Vickers hardness tester. The specimens were randomly divided into 7 groups (n = 10): control, CAP (P), resin-containing fluoride varnish (RF), CAP + resin-containing fluoride varnish (PRF), fluoride varnish (F), CAP + fluoride varnish (PF), and erosion (E). The specimens in the control and erosion groups did not receive CAP or fluoride varnish. All specimens underwent erosive challenge 4 times/day using hydrochloric acid and artificial saliva except for the control specimens that remained in distilled water during the course of the study. After 5 days of erosive challenge, microhardness was measured again, and the percentage of microhardness change was calculated. Surface roughness of two specimens in each group was assessed by atomic force microscopy (AFM). Data were analyzed using one-way ANOVA followed by Tamhane's post-hoc test. RESULTS: The percentage of microhardness change in all groups was significantly higher than that of the control group. All groups showed significantly lower percentage of microhardness change compared with the E group except for the P group; no significant difference was noted in microhardness change of P and E groups. Other experimental groups had no significant difference with each other. Surface roughness was the highest in PRF and the lowest in the F group. CONCLUSION: CAP application had no significant effect on increasing the enamel resistance to erosion. However, enamel resistance to erosion increased significantly after fluoride varnish application alone or fluoride varnish application combined with CAP. No significant difference was noted between the two types of varnishes in this regard. CAP increased the surface roughness while fluoride varnish application alone decreased the roughness.
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Background: This study aimed to assess the effect of different whitening toothpastes containing activated charcoal, abrasive particles or hydrogen peroxide on the color of aged microhybrid composite. Materials and Methods: In this in vitro, experimental study, 45 composite discs (2 mm × 7 mm) were fabricated of a microhybrid composite. They underwent accelerated artificial aging for 300 h, corresponding to 1 year of clinical service. The composites were then randomly divided into five groups (n = 9). One group served as the control and underwent tooth brushing with distilled water. The remaining four groups underwent tooth brushing with Colgate Total whitening (Gt), Colgate Optic White (Go), Perfect White Black (Gp) and Bencer (Gb) toothpastes in a brushing machine The International Commission on Illumination values (Lm, am, bm) were determined using a spectrophotometer. Color change (ΔE) calculated based on this formula: ΔEm= ([ΔLm] 2 + [Δam] 2 + [Δbm] 2)½. The differences were defined by ΔE1 (after aging-baseline),ΔE2 (after brushing-after aging) and ΔE3 (after brushing-base line). ΔE1 were evaluated to ensure that color mismatch had occurred (ΔE1 > 5.5). Difference in (L, a, b) parameters after aging and after tooth brushing in each group, color parameter changes (ΔL2, Δa2, Δb2, ΔL3, Δa3, Δb3) and ΔE2 and ΔE3 were analyzed and compared using Wilcoxon test and independent sample median test at P = 0.05 level of significance. Results: The color parameter changes, ΔE3 and Δ E2 were not significantly different among the five groups (P > 0.05). In Gp and Gb charcoal a*, b*, and L* after tooth brushing (P < 0.05). In Colgate Optic group, the a* parameter significantly decreased while the L* parameter significantly increased (P < 0.05). Conclusion: The results showed that there is no significant difference in the color change of Spectrum composite following tooth brushing with different whitening toothpastes for two weeks. It should be noted that Δ E3 reached to <3.3 only in charcoal whitening toothpastes.
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OBJECTIVE: This study aimed to assess the effect of fluoride varnish on glass ionomer microhardness changes after endogenous acid erosion challenge. METHODOLOGY: In this study, 40 conventional glass ionomer (CGI; Fuji IX) and 40 resin-modified glass ionomer (RMGI; Fuji IILC) discs were fabricated and divided into 4 subgroups (n = 10) for immersion in synthetic gastric acid or saliva for 27 h with/without fluoride varnish application. The surface microhardness was measured at baseline and after immersion, and the change in microhardness was calculated. Data were analyzed using analysis of variance and T-test. RESULTS: A reduction in microhardness was noted in all subgroups following immersion. The lowest change in microhardness of both CGI and RMGI occurred in artificial saliva. In CGI groups, the highest reduction in microhardness occurred in synthetic gastric acid with fluoride varnish application, and the reduction was significantly different from that of the CGI group with fluoride varnish application (p value = .01). In RMGI groups, the highest reduction in microhardness was noted in synthetic gastric acid without fluoride varnish application, and the reduction was significantly different from that of the other groups (p value < .05). CONCLUSIONS: Exposure to synthetic gastric acid caused a significant reduction in microhardness of RMGI. Varnish application significantly decreased the acid susceptibility of RMGI, but not that of CGI.
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STATEMENT OF THE PROBLEM: Adequate compressive strength is an important characteristic for an ideal liner. PURPOSE: This study aimed to assess the compressive strength of several commonly used liners. MATERIALS AND METHOD: This in vitro, experimental study evaluated 120 samples fabricated of Dycal, Calcimol LC, Vitrebond, Activa Bioactive, and TheraCal LC (n=24) liners according to the manufacturers' instructions. The samples were fabricated using a cylindrical stainless steel mold with 6±0.1 mm height and 4±0.1 mm internal diameter. Half of the samples in each group (n=12) underwent compressive strength test immediately after completion of their primary setting while the other half (n=12) underwent compressive strength test after 24 h. During this period, the samples were immersed in deionized water (grade 3) and incubated at 37±1°C and 100% humidity for 24 h. The compressive strength was measured using a universal testing machine. Data were analyzed using two-way ANOVA followed by Tukey's post-hoc test. RESULTS: The compressive strength of the five liners was significantly different (p< 0.05). Calcimol LC showed maximum compressive strength both immediately after setting and after 24 h. The compressive strength at 24 h was significantly higher than the primary compressive strength in all groups (p< 0.05). CONCLUSION: Within the limitations of this study, it seems that Calcimol LC, Activa Bioactive Liner, and TheraCal LC have adequate compressive strength and can be used alone to provide adequate support for the restorative materials.
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PURPOSE: Debonding from the root canal dentin is the most common failure mode of fiber posts. This study aimed to assess the effects of cold atmospheric argon plasma (CAAP) and ethylenediaminetetraacetic acid (EDTA) on micro-push-out bond strength of fiber posts to root canal dentin. MATERIALS AND METHODS: Forty maxillary canine teeth were decoronated, underwent endodontic treatment, and were stored in an incubator for 7 days. After post space preparation, the teeth were randomly divided into four groups for different surface treatments: (I) saline, (II) 17% EDTA, (III) CAAP, and (IV) 17% EDTA + CAAP. Fiber posts (Whitepost no. 2, FGM) were cemented into the root canals using Panavia F2.0 resin cement, and 1 mm-thick sections were made at the coronal, middle, and apical thirds of the roots. The samples underwent micro-push-out bond strength test. The mode of failure was also determined under a stereomicroscope. Data were analyzed using three-way ANOVA and Tukey's post hoc test (α = 0.05). The mode of failure data were analyzed using the chi-square test. RESULTS: The mean micro-push-out bond strength of fiber posts was not significantly different in the four groups (P > 0.05). However, the bond strength values in the coronal third were significantly higher than the corresponding values in the apical third (P=0.01). There was no significant difference in the modes of failure between the groups (P > 0.05). CONCLUSION: Application of CAAP alone or in combination with 17% EDTA could not successfully increase the bond strength of fiber posts to root canal dentin.
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OBJECTIVES: The advantages of indirect composite restorations such as less crack formation during their computer-aided design/computer-aided manufacturing process, compared with ceramic restorations, have resulted in their growing popularity. However, restoration failure is a major concern with regard to the long-term clinical success of restorations and may occur as the result of propagation of a crack originated from an internal flaw in the restoration. This study aimed to compare the fracture toughness of three indirect composite resins. MATERIALS AND METHODS: In this in vitro experimental study, 10 specimens measuring 3 × 3 × 18 mm were fabricated of Gradia, Crios, and high impact polymer composite indirect composites. A single edge notch with a diameter < 0.3 mm and 0.3 mm length was created in the 9 mm longitudinal dimension of specimens using a no. 11 surgical scalpel. The specimens were then subjected to 4-point flexural strength test in a universal testing machine with a crosshead speed of 0.1 mm/s until failure. STATISTICAL ANALYSIS: Data were analyzed using IBM SPSS Statistics via one-way analysis of variance (ANOVA) and Tukey's HSD (honestly significant difference) test. The statistical power was set at p Ë 0.05. RESULTS: One-way ANOVA showed a significant difference in fracture toughness of the three composite groups (p = 0.000). According to the Tukey HSD analysis, the fracture toughness of HIPC was significantly higher than that of the other two composites. The fracture toughness of Gradia was significantly lower among all. CONCLUSIONS: Within the limitations of this study, the results showed that high temperature-pressure polymerization can increase resistance to crack propagation and subsequently improve the clinical service of indirect composite restorations. Although we do not know the filler volume percentage of HIPC, it seems that filler volume percentage of the composite is inversely correlated with fracture toughness.