Diamond Disc Research Articles

In vitro evaluation of bond strength of sealers after using various irrigants and Erbium-Yttrium-Aluminum-Garnet laser irradiation on radicular dentin surface: A SEM study

Aim: The aim of this in vitro study was to evaluate and compare the push-out bond strength of Adseal and mineral trioxide aggregate (MTA) Fillapex sealer after using various irrigants and Erbium-Yttrium-Aluminum-Garnet (Er:YAG) laser irradiation on radicular dentin surface. Materials and Methods: A total of 80 freshly extracted human permanent maxillary anterior teeth were sectioned transversally below the cemento-enamel junction. The remaining root portion was sectioned to get 4-mm thick dentin disc from coronal end of the root, with straight handpiece, and diamond disc. Root canal of specimens was prepared with bur to create space for sealer placement. Specimens were divided into eight groups of 10 samples each, as per irrigants and sealer used. In Group 1, 3, 5, and 7 specimens irrigated with distilled water, NaOCl, Ethylenediaminetetraacetic acid (EDTA), and Er:YAG laser, respectively, and obturated with Adseal sealer. In Group 2, 4, 6, and 8 irrigated with distilled water, NaOCl, EDTA, and Er:YAG laser, respectively, and obturated with MTA Fillapex sealer. After sealer setting, the force used to remove the sealer was evaluated using universal testing machine. Recorded force used to calculate the push-out bond strength in Megapascals and scanning electron microscopy examination was done for specimens. Results: Adseal sealer had significantly higher bond strength than MTA Fillapex sealer, irrespective of irrigant used. The highest bond strength was seen in specimens irrigated with EDTA and obturated with Adseal sealer and least in specimens irrigated with distilled water and obturated with MTA Fillapex sealer. Conclusion: Adseal sealer had significantly higher bond strength than the MTA Fillapex sealer. EDTA irrigation showed better smear layer removal, followed by Er:YAG laser irradiation, then NaOCl, least by distilled water.

Evaluation of Efficacy of Different Instrumentation for Removal of Gutta-percha and Sealers in Endodontic Retreatment: An In Vitro Study

The aim of the present study was to evaluate the efficacy of different instrumentation for removal of gutta-percha and sealers in endodontic retreatment. A total of single-rooted mandibular premolars were collected. Access opening was performed in all specimens. The working length was determined by reducing 1 mm from the length of instruments that were seen reaching the apex. All the canals were dried with paper points. Lateral condensation technique was used to obturate the canals with gutta-percha and zinc oxide eugenol was used as a sealer. The specimens were randomly segregated into three experimental groups. Group I: ultrasonic retreatment tip, group II: R-Endo retreatment files, group III: Mtwo retreatment files. Roots were grooved into two halves with a diamond disc in a longitudinal, buccolingual direction. A stereomicroscope with ×40 magnification was used to image the quantity of gutta-percha and sealer on canal walls. With ultrasonic retreatment tip, least amount (1.96 ± 0.32) of gutta-percha and sealer remained, followed by Mtwo retreatment files (2.84 ± 0.24) and R-Endo retreatment files (3.18 ± 0.63). A statistically significant inter-group difference among different instrumentation groups was demonstrated by ANCOVA analysis. In the present study, ultrasonic retreatment tip file systems was found to be more effective in the removal of root canal filling material, followed subsequently by Mtwo retreatment file system and R-Endo retreatment file system. Thorough removal of filling material from the root canals is essential during root canal retreatment for probable cleaning and shaping of canal morphology. Thus, clinicians should be aware of the suitable and better instrumentation system that provides a clean and sterile root canal system without any debris. How to cite this article: Agrawal P, Ramanna PK, Arora S, et al. Evaluation of Efficacy of Different Instrumentation for Removal of Gutta-percha and Sealers in Endodontic Retreatment: An In Vitro Study. J Contemp Dent Pract 2019;20(11):1269-1273.

Adaptation of Single-Cone Gutta-Percha in Curved Canals Prepared and Obturated with Protaper and Heroshaper Systems by Using Cone Beam Computed Tomography.

Objective:The aim of this study is to prepare and obturate the curved canals of the mesiobuccal root of maxillary first molar with four different file systems that is protaper hand files, rotary pro taper (RP) files, heroshaper hand files, and rotary hero shapers files and to evaluate the adaptation of their single-cone Gutta-percha by cone beam computed tomography (CBCT).Materials and Methods:Eighty teeth were selected and were divided into two groups (G1A1, G1A2 and G2A1, G2A2 as hand and RP file system, G1A3, G1A4 and G2A3, G2A4 as hand and rotary hero shaper files system) of fourth teeth each. After access opening working length of the mesiobuccal canal was established. The distobuccal and palatal roots of the samples were removed using the diamond disc at the furcation level. “Endoanalyser” software was used to measure Schneider's angle on the preoperative radiograph. This angle was measured by drawing two lines-one parallel to the long axis of the canal, in the coronal third, and the second line from the apical foramen to intersect the point where the first line left the long axis of the canal. The canals of each group were then prepared according to the manufacturer's instructions for protaper hand files, RP files, heroshaper hand files, and rotary hero shapers files systems. Direct digital radiography image of all the samples was obtained. And then, the samples were exposed to CBCT to evaluate their single-cone adaptations. The data were analyzed using SPSS 20, IBM, Armonk, NY, United States of America.Results:The null hypothesis that there will not be any gap area in the adaptation of their single-cone of different file system was rejected. Minimal gap area was seen in rotary hero shapers file system (0.001 mm2) and was maximum in hand protaper (HP) file system (0.015 mm2).Conclusion:CBCT is a useful tool in detecting the gap area after obturation in curved canals. The HP single-cone adaptation showed the maximum gap area and rotary heroshaper single-cone adaptation showed the minimum gap area.

Comparative evaluation of push-out bond strength of gutta-percha using different sealers with lateral condensation and thermoplasticized obturation technique: An in vitro study.

Aim:The study aimed to evaluate and compare the push-out bond strength of gutta-percha using AH plus, Endosequence BC, and Roeko seal sealer with lateral condensation and thermoplasticized obturation technique.Materials and Methods:Sixty single-rooted premolars were instrumented and samples were randomly assigned into three groups based on the sealer used (Group A-AH Plus, Group B-Endosequence BC, Group C-Roeko Seal) which were further divided into two subgroups-A1, B1, and C1 were obturated by the lateral condensation technique and A2, B2, and C2 using the thermoplasticized technique. Each sample was sectioned horizontally using a diamond disc, representing apical, middle, and coronal thirds, respectively. Root segments were then mounted on an acrylic block, and push-out bond strength of each sample was tested using the universal testing machine.Statistical Analysis:One-way ANOVA, Tukey's test, and unpaired t-test.Results:For mandibular premolar teeth with a single canal using lateral condensation technique, the highest push-out bond strength was found in the A1 group (7.30 ± 0.61 MPa) at the apical level. While using the thermoplasticized technique, the highest push-out bond strength was found in the B2 group (3.71 ± 0.81 MPa) at the apical level. Overall results showed that the lateral condensation technique showed significantly higher push-out bond strength than thermoplasticized technique (P < 0.028).Conclusions:The push-out bond strength of AH Plus sealer was higher than the Endosequence BC sealer and Roeko seal sealer. Lateral condensation technique has shown higher push-out bond strength than the thermoplasticized technique.

Effect of CO2 Laser and 1.23% Acidulated Phosphate Fluoride on Acid Resistance and Fluoride Uptake of Human Tooth Enamel: An In Vitro Assessment

To evaluate the effectiveness of CO2 laser treatment before applying 1.23% acidulated phosphate fluoride (APF), through topically applied 1.23% APF solution, and after applying 1.23% APF on acid resistance and fluoride uptake of the enamel. Sixty non-carious human premolars were extracted due to the orthodontic reason and stored in distilled water solution under refrigeration. Using a water-cooled diamond disc, enamel slabs of 4 mm × 4 mm × 1.5 mm were cut from the buccal surface of each tooth. Sixty samples were randomly divided into one control group and five test groups of 10 premolars each. Solution was prepared for wet chemical analysis followed by fluoride analysis that was carried out using a fluoride ion selective electrode (Thermo Scientific Orion 4-Star Plus ISE Meter). The weight of enamel (WE) was determined from the amount of calcium (Ca) etched away considering the fact that the Ca content of the human enamel is 37.4 wt%. The subgroups were statistically analyzed using ANOVA for fluoride determination and evaluation of acid resistance. There was a significant increase in acid resistance of enamel slabs when treated individually or in combination of a low-power CO2 laser and 1.23% APF solution. Application of 1.23% APF solution after low-power CO2 laser treatment showed maximum increase in acid resistance. Application of a low-power pulsed CO2 laser through topically applied 1.23% APF solution resulted in a detrimental effect of the human tooth enamel with resultant decrease in acid resistance. High fluoride uptake does not necessarily indicate increased acid resistance. The present study provides evidence that a low-power CO2 laser can be used effectively in combination with topically applied 1.23% APF solution in order to make the enamel more resistant to acid attack, thereby helping in controlling dental caries.

Safe technologies for cutting reinforced concrete structures by means of diamond tools

The advantages and the need to improve the safety of work when using modern diamond technologies for cutting concrete and reinforced concrete structures which are common during the dismantling and reconstruction of civil objects are shown. Improved organizational, structural and technological schemes of cutting these structures with diamond disc and wire saws with remote control are reasonably proposed. Preliminary fastening of cut elements on independent spatial scaffolding with screw jacks is a distinctive feature of the proposed schemes. In case of reconstruction by means of a device or an increase of the size of openings in load-bearing reinforced concrete and stone walls, a preliminary installation and commissioning of reinforcement steel frames provided for by the project are proposed, on them – guides of diamond disc, chain or wire saws and only then – cutting of reinforced concrete with its forced canting outside the working area for recycling.

The relationship between the storage methods and the formation of dentinal defects (cracks)

ABSTRACT Objective: This research study aims at conducting an in vitro evaluation of crack formation in freshly extracted teeth after undergoing different storage and decontamination methods. Methods: 60 erupted upper third molars conventionally extracted using forceps # 210h (quinelato surgical instruments, rio claro - sp) and randomly distributed in three groups (n = 30): group 1 - storage in dry environment for 30 days, group 2 - sterilization in autoclave and storage for 30 days in distilled water, and group 3 - 10% formaldehyde decontamination for 14 days and storage in distilled water for additional 30 days. after the storage period, teeth had their roots transversely sectioned at 2, 4 and 6 mm below the root apex using a low rotation diamond disk under constant cooling. the evaluation of fragments was performed using a 30-time magnification microscope. Results: Cracks were seen only in group 1 and the chi-square statistical test with 5% significance level showed a statistically significant difference comparing the dry storage group to the others. Conclusion: The storage of extracted teeth in a dry environment influences the formation of dentinal defects.

Influence of Diode Laser on the Bond Strength of Self-Etching Adhesive Systems to Human Dentin: An in vitro Study.

Introduction:The treatment of dental tissues before adhesive restorative procedures is an important step in the bonding protocol and determines the clinical success of restorations.Aim:The aim of this study is to evaluate in vitro the influence of diode laser on the shear bond strength of one- and two-step self-etch (SE) adhesives to dentin when the laser is applied over the adhesives before photopolymerization.Methodology:About 20 freshly extracted noncarious intact maxillary premolars were collected, and the buccal and lingual surfaces of the tooth were ground with the help of diamond disk under water coolant till dentin was exposed. The specimens were divided into two groups of 10 each. Buccal surfaces of all the specimens were exposed to diode laser before light curing (test/experimental group) act as control group. In Group I, Clearfil SE with laser was used on the buccal surface, whereas in Group II, G-bond SE adhesive with laser was used on the buccal surface. Shear bond test was measured using an universal testing machine and the values were obtained in megapascals (MPa).Results:P < 0.05 was considered statistically significant. According to the results, it was found that the mean bond strength values of the laser-treated groups were significantly higher than groups not treated with laser.Conclusion:Within the limitations of this study, it can be concluded that mean bond strength Clearfil SE with and without laser was significantly higher than G-bond with and without laser values.

New insight into the role of electronic apex locators in detecting simulated horizontal root fractures: An In vitro study

Aim and Objectives: The aim of this study is to check the accuracy of two different electronic apex locators (EALs): Canal Pro and Root ZX – in locating simulated horizontal root fractures (HRFs). Materials and Methods: Forty-five recently extracted, single-rooted, human permanent teeth were selected for the study. Endodontic access cavity was prepared, and canal patency was checked using no. 10-K file. Horizontal fractures were simulated using 0.2-mm thick diamond disk in coronal, middle and/or apical third of root by operator one, until half of the canal was exposed circumferentially. Using both the apex locators, all the fractures were detected by the second operator to confirm the accuracy of EALs. The actual length of the fractures was then measured under ×2.5 magnification, and results were subjected to statistical analysis. Results: Results were analysed using the one-way analysis of variance and Tukey's post hoc test, and the differences between all the test samples were analysed. All the measurements were compared to the actual values separately. A statistically significant difference was determined at 95% confidence level (P ≤ 0.05). Conclusion: Investigated both the EAL are capable of detecting simulated HRF and that the Canal Pro showed a higher accuracy rate.

Comparative Evaluation of Remineralization Potential of Two Varnishes Containing CPP-ACP and Tricalcium Phosphate: An In Vitro Study.

ABSTRACTAimThe aim of this study is to evaluate the remineralization potential of Clinpro XT varnish containing tricalcium phosphate (TCP) and MI varnish containing casein phosphopeptide (casein phosphopeptide–amorphous calcium phosphate, CPP–ACP).Materials and methodsThirty premolar teeth were taken and divided into three groups. Samples were sliced mesiodistally into buccal and lingual halves using a diamond disk bur. The buccal halves of the teeth were used for the study. Artificial caries like lesions were produced and evaluated with Diagnodent. The samples in each group were treated with the respective remineralizing agent (except for the control group) at every 24 hours for 7 days and the surfaces were assessed using Diagnodent to record the values after the remineralization procedure. The Diagnodent values obtained were tabulated and statistically analyzed using one-way ANOVA and Tukey's multiple comparison tests.ResultsThere was a significant difference between the values calculated before and after remineralization in all the three groups.ConclusionThe study findings showed that MI varnish containing CPP–ACP had the highest release of fluoride as compared to the Clinpro fluoride releasing varnish.Clinical significanceMI varnish is a 5% NaF varnish containing CPP–ACP to give an exceptional fluoride varnish that releases more bioavailable fluoride, calcium, and phosphate, hence, can be used successfully in remineralization of early carious lesions. CPP–ACP can be used in the clinical practice for reversing or arresting the early carious lesions.How to cite this articleVarma V, Hegde KS, et al. Comparative Evaluation of Remineralization Potential of Two Varnishes Containing CPP–ACP and Tricalcium Phosphate: An In Vitro Study. Int J Clin Pediatr Dent 2019;12(3):233–236.

Comparative evaluation of the effect of various endodontic irrigants on the push-out bond strength of endosequence, Biodentine™, and MTA Plus™ root repair materials: An in vitro study

Aim: This study aimed to evaluate and compare the effects of 2% chlorhexidine and 3% sodium hypochlorite (NaOCl) irrigating solutions on the push-out bond strength of EndoSequence, Biodentine™, and MTA Plus™ root repair materials. Materials and Methods: Teeth were decoronated, and the midroot was sectioned horizontally into slices with the thickness of 2.0 mm with the help of diamond discs. The canal space was enlarged to diameter of 1.4 mm with the help of Gates-Glidden Drill. The samples were divided into three groups (n = 12). EndoSequence, Biodentine™, and MTA Plus™ root repair materials were condensed in the canal space and allowed to set for 10 min. The three groups were further subdivided into two subgroups each. Each material was immersed in NaOCl and chlorhexidine gluconate (CHX), respectively, for 30 min, rinsed with distilled water, and allowed to set for 48 h at 37°C with 100% humidity in an incubator. The push-out bond strength value was then measured using a universal testing machine. Data obtained were statistically analyzed. Results: EndoSequence root repair material (ERRM) proved to have the highest push-out bond strength followed by Biodentine™ and MTA Plus™ root repair materials. In subgroups, CHX in contact with ERRM showed the highest push-out bond strength followed by NaOCl, whereas Biodentine™ when in contact with NaOCl showed more push-out bond strength than when in contact with CHX. MTA Plus™ in contact with CHX showed the least push-out bond strength. Conclusion: The push-out bond strength of ERRM significantly increased after exposure to NaOCl and has the highest push-out bond strength followed by Biodentine™, and MTA Plus™ has the least push-out bond strength.

“Efficiency of removal of debris from root canal system with help of different irrigation system:” An in vitro scanning electron microscope study

Aims and Objectives: The aim of this study was to determine the efficiency of EndoActivator, passive ultrasonic irrigation, side-vented needle, and syringe irrigation for removal of dentinal debris (smear layer) in root canals prepared with same master apical file sizes. Materials and Methods: Forty mandibular premolars with mature apices (extracted) were selected for this study. Each tooth was decoronated 2mm coronal to the cementoenamel junction with a diamond disk to facilitate straight-line access for instrumentation. Apical patency was determined by inserting an ISO # 08 K-file. Working length was determined by placing a size 15 K-file into the canal until it appeared at the apical foramen; this length was measured and the working length was set at 1mm short of this measurement. The roots were sealed with yellow sticky wax (DPI) to avoid apical extrusion during irrigation. The root canals were prepared to size 40, 0.02 taper, using step-back technique. After each instrument change, manual irrigation was performed with 2-mL NaOCl (3%) using a 26-gauge syringe. Then, a total of 40 samples were randomly distributed into four groups. According to group, root canals were irrigated with EndoActivator, passive ultrasonic irrigation, side-vented needle, and syringe irrigation. The roots were spilt and sent laboratory for examination under scanning electron microscope. Results: Ultrasonic irrigation had highest removal of the smear layer than the other irrigation systems followed by EndoActivator, side-vented needle, and syringe irrigation. Conclusion: Ultrasonic irrigation resulted in better removal of the smear layer in the apical third of root canals than EndoActivator, side-vented needle, and conventional needle irrigation.

Abrasive wear performance of zirconium diboride based ceramic composite

The present study focuses on the wear behavior of a pressure-less sintered ZrB2–20 vol% SiC composite in dry sliding interaction against the electroplated diamond disc. Pressure-less sintering was carried out at 2000 °C for 2 h in an argon atmosphere. Sintered composite possesses 98% of the theoretical density, and primarily microstructure contains ZrB2 and SiC phases. The sliding wear of the investigated composite has been studied in pin-on-disc equipment at room temperature at different combinations of loads and sliding speeds to examine the influences of the test parameters on wear mechanism. The results show that the elastic modulus, hardness and fracture toughness for ZrB2 20 vol% SiC are 442 ± 4.5 GPa, 16.5 ± 0.5 GPa, and 5.67 MPa√m, respectively. Results also show that the specific wear rate of the ZrB2-SiC composite increases continuously with increasing the applied loads whereas, it decreases with increasing sliding speed. XRD analyses of worn surfaces suggest that the phase transformation from ZrB2 to ZrO2 may occur due to frictional heating during sliding. The specific wear rates are in the order of ~10−6–10−8 cm2/Nm. The post wear test characterization suggests that oxidation dominates mild wear with low roughness values at low load and high sliding speed, whereas at high loads and low sliding speed severe wear mechanism is observed with high roughness values and deep grooves in surfaces. The mixed mode (oxidative–grain pullout-micro-cutting) wear mechanism is controlling the severe wear.

Load-Bearing Capacity of Monolithic Zirconia Fixed Dental Prostheses Fabricated with Different Connector Designs and Embrasure Shaping Methods.

To investigate the load-bearing capacity and failure mode of monolithic zirconia fixed dental prostheses (FDPs) fabricated with different connector designs and embrasure shaping methods. Seventy four-unit zirconia FDPs (with two premolar pontics) were fabricated and divided into seven groups (n = 10) according to the different connector designs gained by using different embrasure shaping methods. The groups were as follows: monolithic FDPs fabricated with sharp embrasures, monolithic FDPs fabricated with blunt embrasures, monolithic FDPs fabricated with blunt embrasures and no occlusal embrasures, two groups of monolithic FDPs fabricated with blunt embrasures and interproximal separations made with diamond discs at the soft stage and at the fully sintered stage, and monolithic FDPs fabricated with blunt embrasures and interproximal separation accentuated by localized porcelain build-up. A final group was used as a control group, where fully veneered traditional zirconia FDPs were fabricated with default milling settings. The FDPs were artificially aged and loaded to fracture. Load to fracture and failure modes were analyzed by one-way ANOVA, Tukey's post hoc test, and Fisher exact test (α = 0.05). The FDPs fabricated with interproximal porcelain separation showed significantly the highest load to fracture (1038 N ± 82) of all groups (p < 0.001), with no significant difference compared to the FDPs with no occlusal embrasures (934 N ± 175; p ˃ 0.29). The FDPs fabricated with blunt embrasures showed significantly higher load to fracture (873 N ± 115) compared to the FDPs in the control group (689 N ± 75) and the FDPs with sharp embrasures (417 N ± 87; p < 0.001). There were no significant differences between the FDPs with sharp embrasures (417 N ± 87) and the FDPs with interproximal disc separations (467 N ± 94; p ˃ 0.23). Failure mode of the FDPs fabricated with sharp embrasures and interproximal disc separations differed significantly compared to the FDPs in the other groups (p < 0.001). Sharp embrasures and interproximal separations made with diamond discs significantly decrease the load-bearing capacity of monolithic zirconia FDPs compared to FDPs made with blunt embrasures. Blunt embrasures in combination with localized porcelain build-up produce FDPs with high load-bearing capacity in relation to loads that might be expected under clinical use.

Pressure tests supporting the qualification of the ITER EC H&CD upper launcher diamond window

The Electron Cyclotron diamond window which is located inside the port cell serves, together with an isolation valve, as primary vacuum boundary between the ITER vacuum vessel, the transmission lines and the port cell atmosphere and it functions as confinement barrier. The window consists of an ultra-low loss Chemical Vapor Deposition (CVD) diamond disk brazed into a metallic housing and it has to guarantee the compliance with very stringent nuclear safety requirements and an adequate transmission capability for high power mm-waves (1.31 MW at 170 GHz). The design of the window unit is approaching its final phase including design validation analyses, the development of a dedicated qualification program and prototyping activities.In preparation of the testing of complete window prototypes, pressure tests were performed on a mock-up formed by a diamond disk (D = 80 mm, d = 1.11 mm) brazed to two copper cuffs. The scope of the experiments was to show both the capability of the joining between the disk and the cuffs to keep the required vacuum tightness as well as the integrity of the disk when exposed to pressure loads. Based on the requirements defined for the pressure scenarios during normal operation and off-normal events, a test program was developed accounting for cyclic tests at low pressure differentials and overpressure tests up to 2 bar pressure difference over the disk to simulate severe accidental conditions.This paper gives an outline of the ongoing development of the overall qualification program of the ITER torus window and reports specifically on the experimental set-up and the successful outcome of the pressure tests of the brazed diamond disk mock-up. The test program for the complete window prototype needs discussion and approval by F4E and ITER and will directly determine the final qualification program for the series diamond windows.

Thermal conductivity enhancement of phase change materials with 3D porous diamond foam for thermal energy storage

For thermal energy storage applications using phase change materials (PCMs), the power capacity is often limited by the low thermal conductivity (λPCM). Here, a three-dimensional (3D) diamond foam (DF) is proposed by template-directed chemical vapor deposition (CVD) on Cr-modified Cu foam as highly conductive filler for paraffin-based PCM. Results showed the foam substrate was completely covered by continuous diamond films with high quality. And it showed a faster thermal response than that of Cu foam (CF) and Cu disc, while only a little slower than that of free-standing diamond disc with the same thickness. The incorporation of interconnected diamond foam with the diamond volume fraction of only 1.3% in the composite phase change material represented a great thermal conductivity enhancement over the pure paraffin, CF/paraffin and diamond particles reinforced paraffin by a factor of 25.8, 1.62 and 13.88, respectively. The great enhancement of the thermal conductive property was mainly attributed to interconnected diamond networks with high thermal conductivity, which effectively reduced the phonon-phonon and phonon-boundary scatterings. Besides, the DF/paraffin composite PCM exhibited an improved shape stability and a fast heat charging rate with the latent heat of 124.7 J/g. The marriage of the excellent properties of diamond and the inherent advantages of the 3D interconnected structure makes the diamond foams potential components or act as reinforcements in the field of high-efficiency heat dissipation and thermal energy storage.

Effect of Trypsin/EDTA Conditioning on Marginal Microleakage of Class V Composite Restorations Bonded With a One-Step Selfetch Adhesive

Background: Sodium hypochlorite and EDTA solutions are used in the preparation of dentin surfaces, which may increase the bond strength of the composite restorations and decrease their microleakage scores. This in-vitro experimental study aimed to assess the effect of dentin surface conditioning with EDTA/trypsin solution prior to bonding procedure with Clearfil S3 Bond on the microleakage of class V composite restorations. Methods: Class V cavities were prepared on the buccal and lingual surfaces of 18 human premolars (n=18) and randomly assigned into two groups. In the control group, Clearfil S3 Bond was applied on the dentin surfaces. While in the experimental group, before applying Clearfil S3 Bond, the surfaces were conditioned with EDTA/trypsin solution. The cavities on the teeth were then incrementally filled with Filtek Z250 light-cure composite. Afterward, all the samples were thermocycled for 500 cycles. Next, the specimens were immersed in methylene blue solution for 72 hours. The restorations were sectioned buccolingually through the center of the restorations with a diamond disk. Then, microleakage at the tooth- restoration interface was evaluated in the enamel and dentin margins blindly using dye penetration under a stereomicroscope at ×40 magnification. Finally, data were statistically analyzed by Mann-Whitney U test. Results: The results showed no significant differences between two groups regarding the microleakage scores of the enamel and dentin edges. In addition, in all sections and edges of the experimental group, decreased microleakage scores were attained compared to the control specimens (P<0.03). Conclusions: Regarding the limitations of the present study, the preparation of dentin surfaces with EDTA/trypsin solution before applying Clearfil S3 Bond resulted in the decreased microleakage scores compared to unprepared surfaces.

Experimental grinding of cubic zirconia with grooved and non-grooved diamond discs

As a cubic crystalline form of zirconium dioxide , cubic zirconia (CZ) is hard, optically flawless, and usually colorless. This interesting mineral crystal has become a popular gem with its low cost, durability, and close visual likeness and the same fashion as diamond , and the cutting techniques for the preparation of cubic zirconia gems have received intensive attentions from diamond gemstone industry in recent years. Among the processes of gem cutting, the grinding process is not only the most time-consuming, but also the key process to determine product quality. However, mechanical characteristics such as the low strength, fracture toughness, and elastic of cubic zirconia make the grinding process much more challenging. In this work, a novel grooved and metal-bonded diamond disc was designed and employed in CZ grinding process to reduce the cutting forces and enhance the material removal rate. Experiments were conducted on an automatic faceting gem machine developed by our group to investigate the influences of intermittent vibro-impact in grinding gemstone. The comparison of some important parameters like the grinding force and the surface roughness obtained by grooved diamond disc and non-grooved diamond disc was carried out. Five rotational speeds of grinding disc, i.e., 1600, 1900, 2200, 2500, and 2800 rpm and five feed rates of 0.3, 0.5, 0.7, 0.9, and 1.1 mm/min were used respectively in this study. From the experimental results, it was observed that the normal grinding force with grooved disc was significantly smaller than that of non-grooved disc, which means under the same grinding force, the feed rate of grooved grinding plate disc is higher than that of non-grooved grinding disc. And the surface roughness of the CZ surface was also decreased with the use of the grooved disc compared with the non-grooved disc. Therefore, the present grooved disc could be a promising tool for cubic zirconia grinding to improve the processing efficiency while also ensures the surface quality.

Analysis of Ag(I) Biocide in Water Samples Using Anodic Stripping Voltammetry with a Boron-Doped Diamond Disk Electrode.

The electroanalytical performance of a new commercial boron-doped diamond disk and a traditional nanocrystalline thin-film electrode were compared for the anodic stripping voltammetric determination of Ag(I). The diamond disk electrode is more flexible than the planar film as the former is compatible with most electrochemical cell designs including those incorporating magnetic stirring. Additionally, mechanical polishing and surface cleaning are simpler to execute. Differential pulse anodic stripping voltammetry (DPASV) was used to detect Ag(I) in standard solutions after optimization of the deposition potential, deposition time and scan rate. The optimized conditions were used to determine the concentration of Ag(I) in a NASA simulated potable water sample and a NIST standard reference solution. The electrochemical results were validated by ICP-OES measurements of the same solutions. The detection figures of merit for the disk electrode were as good or superior to those for the thin-film electrode. Detection limits were ≤5 μg L-1 (S/N = 3) for a 120 s deposition period, and response variabilities were <5% RSD. The polished disk electrode presented a more limited linear dynamic range presumably because of the reduced surface area available for metal phase formation. The concentrations of Ag(I) in the two water samples, as determined by DPASV, were in good agreement with the concentrations determined by ICP-OES.

Prevalence of Different Types of Apical Root Canal Morphology and their Treatment Recommendations in an Institute

Canals can be of different shapes in cross section including round canals, oval canals, long oval canals or ribbon shaped canals. Recesses of nonround canals may not be included in the round preparation created by rotary instruments and thus they remain unprepared. The aim of this study included determination of shape and taper of the apical root canal based on diameter at different levels. Measurement of the diameter of the root canal at one, two and three mm cross sections from the apex of the tooth were done such that apical instrumentation in root canal treatment could be modified based on the results obtained. This was a cross sectional study which used convenient sampling technique to determine the sample size. Seventy extracted teeth were sectioned horizontally at one, two and three millimeter from the apex using the diamond disc which was observed under trinocular research microscope for the determination of diameter of root canal under 10x magnification. Digital images of the sections were taken by a camera attached to the research microscope and analysis done using DigiPro 4.0 software. The most common canal configuration was oval. The taper of the canals was 25% in mesial root and 20% in distal in bucco-lingual orientation and 14% in mesial root and 15% in distal in mesio-distal orientation. The most prevalent canal configuration in this study was non round, however, most of the rotary instruments tend to prepare root canals into round shape making their use questionable. The taper of the root canals was found to be higher in our study than what most of the shaping instruments have to offer. So it would be advisable to consider this fact while selecting instruments and preparing these non-round canals as far as the Nepalese subpopulation is considered.