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Donya Jamshidi, Mohammad Reza Sazegar Department of Chemistry, Islamic Azad University, Tehran, IranCorrespondence: Mohammad Reza SazegarDepartment of Chemistry, Islamic Azad University, North Tehran Branch, Hakimiyeh, Tehran, IranTel +98-9381199151Email m_r_sazegar@yahoo.comIntroduction: A novel biocomposite chitosan/graphite based on zinc-grafted mesoporous silica nanoparticles (CGZM-bio) was synthesized and the antibacterial activities of this compound along with that of Zn-MSN nanoparticles were investigated.Methods: The CGZM-bio biocomposite was synthesized using sol–gel and post-synthesis method under UV radiation. The characterizations of the samples were carried out using FTIR, XRD, SEM, and nitrogen adsorption and desorption. The antibacterial activity was carried out against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) after 18 h at 310 K.Results: The suspension samples of the Zn-MSN and CGZM-bio (2– 100 μg.mL− 1) presented antibacterial activities against S. aureus and E. coli. The minimum inhibitory concentration (MIC) values against E. coli for the Zn-MSN and CGZM-bio samples were 10 and 5 μg.mL− 1, respectively, while the MIC against S. aureus for both nanomaterials was 10 μg.mL− 1.Discussion: The antibacterial activities of these materials are due to the generation of radical oxygen species such as •OH, H2O2, and O2 2- during the UV radiation via the generation of the electron–hole pairs which in turn damage the bacteria cells. These nanomaterials may be used in biomedical devices as antibacterial agents.Keywords: Zn-MSN, Staphylococcus aureus, Escherichia coli, antimicrobial activity, UV radiation, electron–hole pair

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Background and Objectives: Contemporary dentistry focuses on more conservative treatment options such as endocrown restorations and application of dental materials with higher resemblance to tooth structure. Polyether ether ketone (PEEK) polymer is a material used for the fabrication of endocrowns. This study aimed to compare the post-fatigue resistance (PFR) of mandibular first molars restored with PEEK and lithium disilicate (LS 2 ) endocrown restorations. Materials and Methods: This in vitro, experimental study was conducted on 20 human mandibular first molars with similar dimensions. The teeth were prepared for endocrown restoration and were assigned to two groups ( n  = 10) of PEEK and LS 2 endocrowns. After fabrication by the computer-aided design and computer-aided manufacturing (CAD-CAM) technique, the restorations were cemented with resin cement. Next, the teeth underwent 15,000 thermal cycles followed by cyclic loading with 600,000 cycles of compressive force (100 N, 4 Hz) and were then subjected to compressive load application in a universal testing machine. The load causing endocrown failure was recorded as the PFR of the respective restoration. The failure mode was also inspected under a light microscope. Data were analyzed by the independent t -test and also chi-square, Mann-Whitney, and Fisher's exact tests ( α  < 0.05). Results: The teeth with PEEK endocrowns showed significantly higher PFR than those with LS 2 endocrowns. Irreparable fractures were dominant in both groups. Conclusion: PEEK may serve as a suitable alternative to LS 2 for the fabrication of endocrown restorations., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2024 Mehrak Amjadi et al.)

Statement of the Problem: The success of root canal therapy depends on root canal irrigation, disinfection, and sealing of root canal. Wettability and roughness of root dentine surface are important factors in root canal disinfection and sealing., Purpose: This study aimed to assess the effect of chloroform application on roughness and wettability of the root canal walls in endodontic retreatment., Materials and Method: This in vitro experimental study evaluated 70 sound extracted human anterior teeth. The specimens were then randomly assigned to 7 groups as follows: Chloroform (group 1), 1g gutta percha+chloroform (group 2), 2g gutta percha+ chloroform (group 3), 1g gutta percha+ 1g sealer+ chloroform (group 4), 2g gutta perch+ 2g sealer+chloroform (group 5), 1g sealer + chloroform (group 6) and 2g sealer + chloroform (group 7). One drop of distilled water was placed on each tooth to measure the contact angle and wettability. Photographs were obtained of an area measuring 50×50 µm 2 in three directions under an atomic force microscope to measure the roughness. The tooth blocks were exposed to the abovementioned mixtures for 10 min, and then rinsed with saline. The roughness and wettability of each sample were measured before and after treatment. Data was analyzed using one-way ANOVA and Tukey's test., Results: The roughness of all groups significantly decreased following treatment, except for groups 1 and 4. The contact angle increased in all groups after treatment (except for the chloroform group), which indicated decreased wettability. The roughness and the contact angle have shown no correlation., Conclusion: Application of chloroform for removal of gutta-percha and sealer in endodontic retreatment decreases the roughness and wettability of dentine., Competing Interests: The authors declare that they have no conflict of interest., (Copyright: © Journal of Dentistry.)

Objective: This study aimed to assess the cytotoxicity and genotoxicity of triple antibiotic paste, double antibiotic paste and calcium hydroxide medicaments on human stem cells of the apical papilla., Methods: In this experimental study, stem cells were isolated from the apical papilla and cultured. They are treated with different concentrations 0.1, 0.5, 1, 10 and 100 mg/ml of medicaments for 24, 48 and 72 hours. The cytotoxicity and genotoxicity of the medicaments were determined using methyl thiazolyl tetrazolium assay and Comet test, respectively., Results: Results showed all tested concentrations of the calcium hydroxide had no significant effect on stem cells at any time point. Triple antibiotic paste showed cytotoxicity in 10 and 100 mg/mL concentrations at all-time points and in 1, 10 and 100 mg/ml concentrations at 72 hours. In addition, its genotoxicity was significantly higher than that of other groups (P<0.05). Double antibiotic paste showed cytotoxic effects only in 100 mg/ml concentration at 24 hours and 10 and 100 mg/ml concentrations at 48 and 72 hours. And also, its genotoxicity in these concentrations was significantly higher than that of control and calcium hydroxide groups (P<0.05)., Conclusion: In contrast to calcium hydroxide, triple antibiotic paste and double antibiotic paste, especially in their higher concentrations, induced cytotoxicity and genotoxicity on human stem cells of the apical papilla.

Introduction: Histologic examination of teeth after regenerative endodontic treatment (RET) shows that the type, quality, and quantity of tissues formed in the root canal space are not predictable. The aim of this study was to examine clinically, radiographically, and histologically the outcome of RET in immature noninfected human teeth using SynOss Putty (Collagen Matrix Inc, Oakland, NJ) as a scaffold., Methods: Three pairs of maxillary/mandibular first premolars in 3 patients scheduled for extraction were included. Sensibility tests confirmed the presence of vital pulps. After informed consent, anesthesia, and rubber dam isolation, the pulps were removed. RET was performed using the following scaffolds: SynOss Putty + blood in both teeth in patient #1, SynOss Putty with or without blood in patient #2, and SynOss Putty + blood or blood only in patient #3. After a follow-up period of 2.5-7.5 months, the teeth were clinically and radiographically evaluated, extracted, and examined histologically., Results: Patients remained asymptomatic after treatment. Radiographic examination of the teeth showed signs of root development after treatment. In teeth treated with SynOss Putty + blood, histologic examination showed formation of intracanal mineralized tissue around the scaffold particles solidifying with newly formed cementumlike tissue on the dentinal walls. The tooth treated with SynOss Putty without blood showed the formation of a periapical lesion. The tooth treated with a blood clot only showed tissues of periodontal origin growing into the root canal space., Conclusions: SynOss Putty + blood showed a predictable pattern of tissue formation and mineralization when used as a scaffold for RET in human immature noninfected teeth. The newly formed mineralized tissue solidifies with newly formed cementum on the dentinal walls., (Copyright © 2018 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: Immature necrotic teeth are at a high risk of fracture, especially at the cervical region, after treatment. This study aimed to compare the impact and fracture strength of immature permanent teeth treated with revascularization versus a mineral trioxide aggregate (MTA) plug and fiber post., Methods: This in vitro, experimental study was conducted on 160 maxillary central incisors, which were randomly divided into 10 groups. The groups included a fracture (F) and impact (I) negative control group, F and I positive control groups, F and I MTA groups, F and I revascularizing group, and F and I revascularized groups. Fracture strength was measured using a universal testing machine with a crosshead speed of 1 mm/min. Other tooth samples were then subjected to the Charpy impact test for impact strength measurements, and the amount of energy absorbed by the teeth was determined. Data were analyzed using the Kolmogorov-Smirnov test, analysis of variance, and the Tukey test., Results: The mean load to fracture of the negative, positive, MTA, revacularizing, and revascularized groups was 1931.8, 1350.1, 1003.8, 1262.5, and 1100.2 N, respectively, and the mean impact strength was 5.04, 3.6, 3.68, 3.16, and 3.65 J, respectively. The fracture and impact strength of the negative control group was significantly higher than that of the other groups (P < .05), but the other groups were not significantly different in this respect (P > .05)., Conclusions: Despite the limitations of this study, the results showed that none of the tested modalities could significantly increase the impact and fracture strength of simulated immature teeth., (Copyright © 2018 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: Taurodontism is an anomaly characterized by elongated crowns and consumedly apical location of the bifurcation area. This study aimed to determine the prevalence of taurodontism in molars based on digital panoramic radiographies in eight cities of Iran., Methods and Materials: This descriptive cross-sectional study was conducted on 2360 digital panoramic radiographs taken for different treatment purposes. Demographic information of patients was recorded and radiographs were evaluated for presence of taurodont molars. The prevalence rates were calculated and the data were analyzed using SPSS software version 18 via paired t -test, chi square test and ANOVA., Results: A total of 2360 panoramic radiographs (from 51.4% male and 48.6% female patients) were evaluated and the prevalence of taurodontism was reported 22.9% (22.6% in males and 23.3% in females) ( P >0.05). Its prevalence was 51.67% in the right and 48.33% in the left quadrants ( P >0.05), 34.1% in the mandible and 65.9% in the maxilla ( P =0.000) and 79.52% in the second and 20.48% in the first molar ( P =0.000). The prevalence of hypotaurodontism, mesotaurodontism and hypertaurodontism was 84.13%, 11.07% and 4.8%, respectively., Conclusion: The prevalence of taurodont molars was high in Iran and it was more common in the second molars and in the maxilla. Hypotaurodontism had the highest prevalence., Competing Interests: ‘None declared’.

Introduction: Many of highly-alkaline dental materials have some adverse effects on physical properties of dentin. As basic substances, mineral trioxide aggregate (MTA), calcium hydroxide (CH) and the new endodontic material, calcium-enriched mixture (CEM) cement, may adversely affect dentin. The purpose of this in vitro study was to evaluate the effect of long-term application of CEM cement, MTA and CH on flexural strength of bovine dentin., Materials and Methods: Three hundred and twenty bovine dentin samples were divided into 4 groups, which were either exposed to CEM cement, CH, MTA or normal saline (control group). Samples of each group were divided into 4 subgroups which were tested by means of Instron Universal Testing Machine for periods of 7, 30, 180 and 365 days after exposure to the test materials. The required force for sample breakage was recorded. The data were analyzed by the two-way ANOVA and Tukey tests., Results: The mean value of forces to break the samples in CEM cement and CH groups was significantly lower than the control group after 1 month (P<0.05). After 180 days, the samples of CEM cement group retrieved their strength but in MTA and CH groups the time interval weakened the samples. After one year of exposure to CH and MTA, flexural strength of the dentin reduced to 72% and 38.7%, respectively (P<0.05). Yet the flexural strength of samples in CEM cement group did not change significantly compared to control group., Conclusion: Following 365 days of application of experimental materials to bovine dentin, the CEM cement showed an interesting result and the samples in this group reached their initial strength during the first week of the study but the other materials caused a reduction in dentin strength at the end of the study.

Introduction: Some studies in dental literature have proposed that short term and long term exposure of root dentin to calcium hydroxide predisposes it to fracture. Mineral trioxide aggregate (MTA) and a recently introduced endodontic material, calcium-enriched mixture (CEM) cement may be used instead of calcium hydroxide and might have an effect on the strength of root dentin. Therefore, the aim of this in vitro study was to compare the short-term effect of calcium hydroxide, MTA and CEM cement on the strength of bovine root dentin., Materials and Methods: In this experimental study, 15 freshly extracted intact bovine incisors were selected. A cylinder with uniform wall thickness (internal diameter of 2.5 and external diameter of 5.5) was prepared. The cylinders were cut longitudinally into 4 symmetrical pieces. The 60 prepared samples were divided into four groups (n =15). The samples were placed in 4 petri-dishes containing calcium hydroxide, MTA, CEM cement and normal saline as the control group. They were then subjected to flexural forces applied by Instron universal machine. Data was analyzed using ANOVA and Tukey test., Results: The mean flexural force in the calcium hydroxide, MTA and CEM cement groups was significantly lower than that in the control teeth (77.9 N, 90.66 N, 94.40 N, compared to 125.12 N respectively, P=0.001). There were no significant differences between calcium hydroxide, MTA and CEM cement group., Conclusion: MTA and CEM cement decreased the flexural strength of bovine root dentin, like their counterpart calcium hydroxide. Further studies are required to determine the effect of these materials on human root dentin clinically.