The effect of home bleaching carbamide peroxide concentration on the microhardness of dental composite resins.

Bleaching is a conservative treatment for discolored teeth, but the effect of this treatment on newer, silorane-based composite resins is unclear. This study evaluated the effect of at-home bleaching on the microhardness of methacrylate- and silorane-based composites. Forty blocks each of a methacrylate-based composite and a silorane-based composite were prepared. The 80 specimens were tested in 8 groups (n = 10): 2 composites, each exposed to 3 different carbamide peroxide concentrations (10%, 16%, or 22%) as well as distilled water (control). The surface of the test specimens was covered daily with the bleaching gel at room temperature for the time period recommended by the manufacturer for each carbamide peroxide concentration. A Vickers hardness testing machine was used with a 100-g load for 20 seconds to register specimen microhardness prior to and after 2 weeks of bleaching. The load was applied at 3 points, and the mean microhardness was calculated. Repeated-measures analysis of variance, paired t test, and Tukey test were used to analyze the data. All bleaching concentrations significantly decreased the microhardness of the methacrylate-based composite resin groups, while microhardness was significantly increased in the silorane-based composite resin groups. There was no evident difference in effects among the different gel concentrations (P > 0.05).

Onset of Mucormycosis in Patients with COVID-19: A Systematic Review on Patients' Characteristics.

Mucormycosis has a significant impact on patients' standard of living and, therefore, a high clinical suspicion, prediagnosis, and rapid treatment are critical in easing patients' suffering and fast recovery. Our focus is to conduct an organized review based on various variables on the patients' characteristics having mucormycosis in severe novel coronavirus disease 2019 (COVID-19). We examined Embase, PubMed-Medline, LitCovid, Web of Science, Scopus, and the reference lists of included case reports up to September 20, 2021, using the Medical Subject Heading (MeSH) phrases and other keywords related to this topic. Subsequently, we investigated associated comorbidities, patient characteristics, position of mucormycosis, steroids use, body involvements, and outcomes. Overall, 77 studies were conducted and among these, 72 studies mentioned that the patients' age to be 48.13±14.33 (mean±standard deviation [SD]) years. Diabetes mellitus (DM) was reported in 77.9% (n=60) of cases. Studies showed that central nervous system (CNS) and bone involvement were reported in 62.3 (n=48) and 53.2% (n=41), respectively. More fatalities were observed in patients with mucormycosis with the active form of COVID-19. Also, men infected with mucormycosis significantly affected by COVID-19. In the end, mortality was higher in males with mucormycosis. As a result, a solid investigation into the root cause of mucormycosis, especially in COVID-19, should be included in the study plan. If the patient is COVID-19-positive and immunosuppressed, this opportunistic pathogen diagnostic test should not be overlooked.

A bibliometric and subject analysis of 3300 most-cited articles in dentistry.

OBJECTIVES: This study aims to analyze the publications that have studied top-cited articles in dentistry. MATERIAL AND METHODS: The study is applied research in terms of the purpose and scientometrics descriptive in terms of type, which has been done using the Retrospective Bibliometric Analysis. To retrieve the 100 most-cited studies in Scopus, an advance search was used. The search results indicate that 33 articles focused on analyzing the 100 most-cited publications on oral and dental subjects. The bibliographic information, including author, journal, country, institution, citation count, and citation density was analyzed. Then the full text of the articles was reviewed to identify the most productive journal, country, and institute in publishing the 100 most-cited articles and also article type, study design, level of evidence, and the most important subjects among the 100 most-cited papers. RESULTS: In these 33 articles, the topics of 3300 most-cited articles were introduced, as well as the introduction of the core journals, countries, and institutes in publishing top-cited articles. The most common research topics in the field of dentistry cover a range of dental public health and pediatric dentistry to adhesive restorative dentistry and implantology. Dental materials, oral medicine, and pathology seem like inseparable topics of common research in dentistry. J Dent Res, which was mentioned in nine articles, was introduced as the journal with the publication of articles of highest citation. J Clin Periodontol and Oral Surgery, Oral Medicine, Oral Pathology, and Oral Radiology were in the second place, being mentioned in five articles. The USA, and two institutions the University of Texas, and the University of Michigan are orderly core country and institute for the production of most-cited articles. CONCLUSION: Researchers and specialists can get familiar with the most productive author, journals, countries, and different institutes for publishing high-quality articles in the field of oral and dental subjects by the means of the results of this article. Furthermore, the results of this study ranked the most cited article topics, which are of interest for publication, demonstrating the future map road oral and dental research.

Effect of different concentrations of carbamide peroxide on the staining susceptibility of resin composites.

CONTEXT: Bleaching can affect the surface properties of resin composites. AIMS: The aim of this study was to evaluate the effect of three regimens of carbamide peroxide (CP) on staining susceptibility of silorane and methacrylate-based resin composites. METHODS: In this study, 80 composite disks were prepared from A2 shade of P90 and Z250 composite resins (40 each). Samples were divided into three test groups based on the CP concentration (10%, 16%, and 22%) and bleached for 14 days. Controls were kept in distilled water. Then, specimens were immersed in a tea solution for 14 consecutive days. A spectrophotometer was used to measure the specimen colors in CIE L*a*b system, initially and after staining. Data were analyzed using SPSS 16 software using two-way ANOVA, t-test, and Tukey honestly significant difference tests at α = 0.05. RESULTS: The color susceptibility of Z250 samples were significantly affected in groups bleached with 22% CP compared to the controls (P = 0.001). The different concentrations of CP did not affect the staining susceptibility of the P90 samples (P > 0.05). CONCLUSIONS: Bleaching of the tested resin composites did not increase their susceptibility to extrinsic staining in vitro except for the Z250 samples bleached with 22% CP.

Evaluating the Microshear Bond Strength and Microleakage of Flowable Composites Containing Zinc Oxide Nano-particles.

INTRODUCTION: Preventive resin restorations (PRR) are the conservative choice for the most common carious lesions in children. Thus, new age flowable resin composites with higher filler content are readily used. The aim of this study was to evaluate the microshear bond strength and microleakage of two flowable resin composites containing different percentages of nano zinc oxide (NZnO) particles, which have proven to have antimicrobial properties. METHODS: This experimental in-vitro study was carried out in the Dental Material Research Center of Babol University of Medical Sciences in 2015. One nanohybrid and one nanofill flowable resin composite were chosen and modified with the incorporation of 1% and 3% Wt NZnO particles. Six groups (n=10, 0%, 1%, and 3%) of resin composite sticks on dental enamel (2×2mm) were prepared to be placed in the microtensile tester. The microshear bond strength magnitude (MPa) was recorded at the point of failure. A class I box (3×0.8×1 mm) was prepared on 60 premolars and filled using the resin composites (6 groups, n=10). The specimens were immersed in a 5% basic fuschin solution and sectioned bucco-lingually to view the microleakage using a stereomicroscope. One-way ANOVA and Tukey tests for microshear and Wilcoxon and Kruskal-Wallis tests for microleakage were used to analyze the data in the IBM SPSS Statistics version 22 software. RESULTS: The bond strength of the 3% clearfill group significantly decreased while no significant change occurred in the bond strength in other groups. The Z-350 group had significantly lower microleakage as nanoparticles increased. No significant difference was observed in the clearfill group. CONCLUSION: Up to 3% Wt incorporation of NZnO particles will not diversely alter the bond strength, but it will be beneficial in providing antimicrobial effects with lower microleakage rates.

Coronal Discoloration Induced by Calcium-Enriched Mixture, Mineral Trioxide Aggregate and Calcium Hydroxide: A Spectrophotometric Analysis.

INTRODUCTION: The aim of this study was to compare the discoloration potential of calcium-enriched mixture (CEM) cement, white mineral trioxide aggregate (WMTA) and calcium hydroxide (CH), after placement in pulp chamber. METHODS AND MATERIALS: Access cavities were prepared in 40 intact maxillary central incisors. Then, a 2×2 mm box was prepared on the middle third of the inner surface on the buccal wall of the access cavity. The specimens were randomly assigned into four groups; the boxes in the control group were left empty, in groups 1 to 3, the boxes were filled with CH, WMTA and CEM cement, respectively. The access cavities and the apical openings were sealed using resin modified glass ionomer (RMGI). The color measurement was performed with a spectrophotometer at the following intervals: before (T0), immediately after placement of the filling material (T1), one week (T2), 1 month (T3), 3 months (T4) and 5 months (T5) after filling of the box and finally immediately after removing the material from the boxes (T6). Color change (Δ E) values were calculated using the sample Kolmogorov-Smirnov test to determine the normal distribution of data, followed by ANOVA, repeated measured ANOVA and post-hoc Tukey's tests. RESULTS: All materials led to clinically perceptible crown discoloration after 1 week. The highest ΔE value belonged to WMTA group. Discoloration induced by CEM cement was not significantly different from CH or the control group (P>0.05). CONCLUSION: CEM cement may be the material of choice in the esthetic region, specifically pertaining to its lower color changing potential compared to WMTA.