Cytotoxicity of Two Experimental Epoxy Resin-Based Sealers

Introduction: Many endodontic sealers are available, but search for the ideal sealer continues. This study aimed to assess the cytotoxicity of two experimental endodontic sealers in comparison with AH-26 resin sealer. Methods and Materials: This in vitro study was conducted on conventional and experimental root canal sealers: AH-26, an epoxy resin experimental sealer A (ES-A) composed of calcium tungstate, zirconium oxide, aerosil, bismuth oxide, titanium oxide, hexamine and an epoxy resin and experimental sealer B (ES-B) with compositions similar to ES-A except for the presence of imidazoline as a catalyst. The experimental sealers containing nano-particles were mixed with 37.5% of an epoxy resin. The extraction of five samples of each experimental sealer (A, B) and AH-26 sealer were subjected to MTT assay in the form of set and fresh at 1, 24 and 72 h with 1, 10, 100% dilution according to the International Standard ISO:10993-2012. Data were analyzed using the one-way ANOVA. Results: The set ES-A had the least cytotoxicity from the first hour but the cytotoxicity of ES-B and AH-26 extraction decreased over time. In fresh form, except for 100% concentration, ES-A showed the least cytotoxicity compared to the other two sealers. Conclusion: All three sealers had high cytotoxicity in 100% concentration but had low cytotoxicity in 10% and 1% concentrations.Keywords: Cytotoxicity; Endodontics; Epoxy Resin; Seale

Physical Properties and Chemical Characterization of Two Experimental Epoxy Resin Root Canal Sealers

Introduction: The aim of this in vitro study was to evaluate the setting time, flow, film thickness, solubility, radiopacity and characterization analysis of three epoxy resin based sealers including two experimental sealers and AH-26. Methods and Materials: Five samples of each material were evaluated for setting time, flow, film thickness, solubility and radiopacity according to ISO 6876 Standard. Characterization of sealers was performed under the scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Statistical evaluation was performed using the Kruskal-Wallis test. Results: In this study, AH-26 showed more radiopacity and flow compared to two other experimental sealers (P<0.05). However, both sealers had lower setting time than AH-26 (P<0.05). No statistical differences were found regarding film thickness, solubility and radiopacity (P>0.05). The characterization analysis exhibited relatively similar microstructure of AH-26 sealer to the experimental root canal sealers. Conclusion: According to the result of this study, all tested root canal sealers had acceptable properties based on ISO 6876 standard criteria.Keywords: Epoxy Resin; Fourier Transform Infrared; Root Canal Sealer; Scanning Electron Microscopy; X-Ray Energy Dispersive Spectroscopy

Effects of Diode and Nd:YAG Laser Irradiation on Friction Forces Between Two Types of Ceramic Brackets and Rhodium-Coated Archwires

Introduction: Ceramic brackets have gained increasing popularity among dental clinicians and orthodontic patients but friction is a major concern when using them. This study sought to assess the effects of diode and Nd: YAG (neodymium-doped yttrium aluminum garnet) laser irradiation on friction forces between two types of ceramic brackets and rhodium-coated esthetic archwires.Methods: Thirty polycrystalline and 30 poly-sapphire brackets were divided into 6 groups (n=10) as follows: (I) control polycrystalline brackets (no laser irradiation), (II) polycrystalline brackets subjected to diode laser irradiation, (III) polycrystalline brackets subjected to Nd: YAG laser irradiation, (IV) control poly-sapphire brackets (no laser irradiation), (V) poly-sapphire brackets subjected to diode laser irradiation, and (VI) poly-sapphire brackets subjected to Nd: YAG laser irradiation. The bracket slots were laser-irradiated on a custom-made table. Sixty 5-cm pieces of rhodium-coated archwires were used for the friction test in a universal testing machine at a speed of 10 mm/min. Ten brackets from the six groups underwent scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX).Results: The frictional resistance value of polycrystalline brackets was significantly higher than that of poly-sapphire brackets, irrespective of laser type (P < 0.05). Irradiation of diode and Nd: YAG lasers, compared with the control group, had no significant effect on friction, irrespective of bracket type (P> 0.05).Conclusion: It appears that diode and Nd: YAG laser irradiation cannot significantly decrease friction. Future studies are warranted on different laser types with variable exposure. DOI: 10.34172/jlms.2021.1

Efficacy of Different Ibuprofen Formulations with Two Prescription Methods on Post Endodontic Pain of Teeth with Irreversible Pulpitis: A Randomized Clinical Trial

Introduction: Pain management during root canal therapy and after that is of great importance in endodontics. This study aimed to compare the effect of two non-steroidal anti-inflammatory drugs (NSAIDs); ibuprofen and ibuprofen lysine with two methods of prescription on pain after single-visit root canal treatment of first and second mandibular molar teeth with irreversible pulpitis. Materials and Methods: This randomized study recruited subjects experiencing moderate to severe pain from a tooth diagnosed with symptomatic irreversible pulpitis (n = 120). Subjects were randomized to receive 400 mg ibuprofen acid or 400 mg ibuprofen lysine regularly or on demand. The primary objective was to measure changes in pain scores at post-operative time frames of 6, 12, 18, 24, 48 and 72 hours after the root canal treatment on a 0-10 numerical rating scale (NRS).  Independent T-test, Non-parametric Kruskal-Wallis Test and Friedman Test were used to analyze the data. Results:  Kruskal-Wallis analysis showed a significant difference in NRS score between on-demand ibuprofen group and regular ibuprofen group and also between regular ibuprofen lysine group and regular ibuprofen group at 6 hours after the treatment (P<0.05). But no remarkable difference was observed in the recorded mean pain intensity of four study groups in the other time frames (P>0.05). Conclusions: Based on this randomized clinical trial, there was no significant difference in the pain intensity of patients using ibuprofen and ibuprofen lysine. Additionally, there was no significant difference in the degree of pain between the on-demand and regular groups, despite the fact that patients in the on-demand group used less medications. Due to the multiple negative effects of NSAIDs, it would be wise to prescribe ibuprofen on demand

Scanning Electron Microscope (SEM) Evaluation of Composite Surface Irradiated by Different Powers of Er:YAG Laser

Introduction: The aim of this study was to evaluate the composite surface treated by different powers of Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) laser in comparison with bur preparation via scanning electron microscope.Methods: Fourteen composite resin blocks with 15× 10 × 10 mm dimensions were used in this study. The samples were divided to seven groups as follow: Group 1 (power: 1 W, Energy: 50 mJ); Group 2 (power: 2 W, Energy: 100 mJ); Group 3 (power: 3W, Energy: 150 mJ); Group 4 (power: 4 W, Energy: 200 mJ); Group 5 (power: 5W, Energy: 250 mJ); Group 6 (power: 6 W, Energy: 300 mJ); Group 7: Diamond bur. Then, the samples were prepared for SEM examination.Results: The surface treated by Er:YAG laser showed irregular and micro porous surface.Conclusion: It seems that composite surface treatment by Er:YAG laser can be an alternative method for composite repair if suitable parameters are used.

The Effect of Remineralizing Agents With/Without CO2 Laser Irradiation on Structural and Mechanical Properties of Enamel and its Shear Bond Strength to Orthodontic Brackets

Introduction: Remineralizing agents may be used for the treatment of white spot lesions (WSLs) prior to bracket bonding. However, some concerns exist regarding their possible interference with the etching and bonding process, negatively affecting the bond strength. This study aimed to assess the effect of two remineralizing agents with/without CO2 laser irradiation on the mechanical properties and shear bond strength (SBS) of demineralized enamel to the orthodontic bracket.Methods: This study evaluated 60 premolar teeth in 6 groups (n=10) as follows: (I) sound enamel, (II) demineralized enamel, (III) Nupro remineralizing agent (N), (IV) Nupro and CO2 laser (N/L), (V) Teethmate remineralizing agent (T), and (VI) Teethmate and CO2 laser (T/L). The remineralizing agents were applied to the enamel surfaces after their immersion in a demineralizing solution for 5 days. In groups IV and VI, the CO2 laser with a 10.6 μm wavelength, 10 ms pulse duration, a 50 Hz repetition rate, 0.3 mm beam diameter and 0.7 W power was irradiated after applying the remineralizing agents. Brackets were bonded to the enamel surfaces and SBS was measured by a universal testing machine. For the assessment of enamel microhardness, 20 sections of molar teeth were divided into 4 groups (n=5; N, N/L, T, T/L) and their microhardness was measured before demineralization, after demineralization and after remineralization. X-ray diffraction (XRD) analysis, field-emission scanning electron microscopy (FESEM) and energy-dispersive spectrometry (EDS) were carried out to assess the formation of hydroxyapatite. The atomic percentages of the C, O, P, Ca, Na, Si, F and Ca/P ratio were determined by EDS analysis.Results: The SBS significantly decreased in group II (P < 0.001). There was no significant difference among the groups I, III, IV, V and VI (P < 0.05). This finding was similar to the microhardness results, which showed an increase in microhardness after remineralization (P < 0.05), with no difference among the remineralizing agents. The Ca/P ratio was the highest in the Nupro group and the lowest in the demineralized group.Conclusion: Remineralizing agents can significantly improve the microhardness and structural properties of demineralized enamel to a level similar to that of sound enamel with no adverse effect on SBS to orthodontic brackets

Efficacy of a Novel Bioactive Glass-Polymer Composite for Enamel Remineralization following Erosive Challenge

INTRODUCTION: Dental caries is the most common cause of tooth loss. However, it can be stopped by enhancing remineralization. Fluoride and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) are among the most important remineralizing agents. Recent studies have used bioactive glass as a remineralizing agent in different forms. This study aimed to assess the efficacy of a composite paste (prepared by mixing urethane polypropylene glycol oligomer with bioactive glass powder for easier application). MATERIALS AND METHODS: Enamel disks were cut out of the buccal surface of extracted sound third molars. The samples were randomly divided into 3 groups of 15 and underwent Vickers microhardness test. X-ray diffraction (XRD) and field emission scanning electron microscopy/energy dispersive X-ray spectroscopy (FESEM/EDS) were performed. All samples were immersed in a demineralizing solution for 14 days. The tests were then repeated. Next, bioactive glass paste, fluoride, and CPP-ACP were applied on the surface of the samples and they were then stored in an artificial saliva for 14 days. The tests were repeated again. The microhardness values were analyzed using repeated measures ANOVA followed by one-way ANOVA and Tukey's post hoc test (P < 0.05). RESULTS: The microhardness of the bioactive glass group was significantly higher than that of other groups (P < 0.05). XRD revealed an enamel structure more similar to sound enamel in the bioactive glass and CPP-ACP groups compared with the fluoride group. FESEM/EDS revealed higher hydroxyapatite deposition in the bioactive glass group than in the other two groups. CONCLUSIONS: All three remineralizing agents caused remineralization, but bioactive glass paste had a greater efficacy

Comparative evaluation of fracture resistance and failure modes in endodontically treated molars restored with zirconia endocrown and onlays

Introduction: Developments in dental materials, CAD/CAM technologies and adhesive dentistry have improved the application of conservative restorations such as endocrowns and onlays. Among ceramics, zirconia has properties such as high strength, transformation toughening, chemical and structural durability, and biocompatibility, which enable zirconia to be used in the posterior area. Aim: This study is a comparative evaluation of fracture resistance and failure modes in endodontically treated molars restored with zirconia endocrown and onlays. Materials and methods: This study was performed on 20 human mandibular first molars with similar dimensions. After root canal treatment, the samples were divided into two groups: endocrowns and onlays (n=10). Restorations were made using a CAD-CAM milling machine with zirconia CAD blocks and, after cementation, subjected to 10,000 thermocycling and 500,000 fatigue cycle procedures, respectively. Each specimen was placed on a Universal Testing Machine and subjected to axial compressive force applied at a crosshead speed of 0.5 mm/min. The mean loads of failure of each group were statistically compared using the Student t-test. Chi-square tests were used to compare frequencies of failure modes among groups. Results: Fracture resistance showed a statistically significant difference between endocrown (5374.6810±670.03445 N) and onlay (3312.5000±804.01428 N) (p0.05). Conclusions: The fracture resistance of endocrown is substantially higher than that of onlay, and failure type does not differ in both restorations. Zirconia is a reliable material to use in conservative restorations