Diamond Disc Research Articles

COMPARATIVE EVALUATION OF SHEAR BOND STRENGTH OF A BIOACTIVE COMPOSITE AND NANO-COMPOSITE: AN IN VITRO STUDY

Objectives: The aim of this study was to determine and compare the shear bond strength of activa bioactive restorative with and without adhesive and nano-composite. Materials and Methods: Sixty freshly extracted human premolars were used. The teeth were mounted vertically in a self-cure acrylic cylinder. A high-speed fine diamond disk with copious wa­ter spray was used to obtain a flat dentin of the labial surface. One clinician prepared all the teeth. The teeth were divided into three groups twenty teeth each, n=20 Group I : The flat dentin surfaces were acid-etched for 15 sec with 37% phosphoric acid, it washed and dry then application of bioac­tive composite into a plastic ring measuring 3mm width and 2 mm depth. Each specimen was light cured for 40 sec by LED light cure unit. Group II: The flat dentin surfaces were acid-etched and then two coats of bonding agent was applied over each specimen and light cured for 20 sec. then application of bioactive composite. Group III (Control): The flat dentin surfaces were acid-etched and application of bonding agent then nano-composite applicated into a plastic ring measuring 3mm width and 2 mm depth. Each specimen was light cured for 40 sec by LED light cure unit. All of the specimens were tested for shear bond strength and all of the data were analyzed by One way analysis of variance (ANOVA) and Tukey’s post hoc test. Results: Results showed that the highest mean value was detected in Nanocomposite, fol­lowed by bioactive composite with adhesive, the mean shear bond strength of Nanocomposite and composite with adhesive was significantly greater than bioactive composite without adhesive (p<0.0001). Conclusions: Nanocomposite showed higher shear bond strength followed by bioactive com­posite with adhesive, while bioactive composite without adhesive showed the lowest shear bond strength value

ITER ECRH Upper Launcher diamond window – Qualification and testing of a Protection Important Component

The diamond window is part of the ex-vessel waveguide system of the ITER ECRH Upper Launcher and consists of an ultra-low loss CVD diamond disk mounted in a system of metallic parts. On the one hand the window has to fulfil adequate transmission capability for high power mm-waves and on the other hand it serves, together with an isolation valve, as primary vacuum boundary of the ITER vacuum vessel, and has the function of tritium confinement. Therefore it is classified as Protection Important Component and high requirements for quality and safety apply. The window assembly cannot be entirely covered by codes and standards and thus an ad-hoc qualification program is required, including prototyping activities. The mm-wave transmission capability of the window, which is mainly defined by the dielectric loss of the diamond disk, has to be demonstrated as well as its structural integrity. For previous and current window prototypes, diamond disks with low dielectric losses have been chosen with a diameter of 80 mm and a thickness of 1.11 mm. This thickness satisfies the resonance condition (d = n*λeff/2) for the 170 GHz beam, ensuring a high transmission, but it also needs to be validated with respect to the mechanical loads, especially the expected pressure loads.Investigations on the flexural strength of diamond disks (D = 30 mm, d = 1.11 mm) have been performed using a ring-on-ring set-up and the results lead to an estimation of the failure behavior.In addition, pressure tests of a mock-up consisting of a diamond disk (D = 80 mm, d = 1.11 mm) brazed to a copper cuff are under examination. The dedicated test program includes cyclic tests at lower pressures and high pressure tests (up to 2 bar) allowing a simulation of the expected events.This paper will give an overview on the qualification activities for the ITER torus window with a focus on the qualification of the diamond disk and with respect to its mechanical properties. Respective parts of the test program, which need F4E and IO review and approval, will be described and first results will be presented.

Detection of simulated vertical root fractures; which is better multi-detector computed tomography or cone beam computed tomography?

ObjectivesMulti-detector computed tomography (MDCT) and cone beam computed tomography (CBCT) were compared regarding their ability to detect vertical root fractures. MethodsSixty four extracted posterior teeth were included in this study. Using a diamond disc, thirty six teeth were cut vertically to simulate a VRF. Twenty eight teeth were used as control. Fractured and non-fractured teeth were randomly positioned in 4 skulls and mandibles. Scanning was performed first on a 16 slice Siemens MDCT, then by i-CAT Next Generation CBCT. Two observers assessed the multiplanar images for vertical root fractures using a 3-point scale. The first observer repeated the assessment after 1 week. Later, the 2 observers re-assessed the images together to reach a consensus score. ResultsCBCT showed higher sensitivity, accuracy as well as negative predictive value compared to MDCT. The mean area under the curve was 0.917 for MDCT and 0.972 for CBCT. The difference in diagnostic accuracy between the 2 modalities was statistically significant P = .036. Inter-observer agreement was 0.971 for MDCT and 0.994 for CBCT, whereas intra-observer agreement was 0.981 for MDCT and 0.985 for CBCT. ConclusionUsing the specified scanners at the specified exposure parameters, the diagnostic accuracy of CBCT in detecting vertical root fractures was significantly higher than MDCT.

Evaluation of bioceramics and zirconia-reinforced glass ionomer cement in repair of furcation perforations: An in vitro study.

Aim:The aim and objective of this study was to evaluate and compare the sealing ability of EndoSequence BC RRM-fast set putty, Proroot mineral trioxide aggregate (MTA), and Zirconomer in the repair of furcal perforation by measuring dye leakage under stereomicroscope.Methodology:A standard access cavity was made on forty-eight extracted mandibular and maxillary first molars followed by creating a furcal perforation in the center of the pulp chamber by using No. 4 round bur (creating a perforation of 2 mm diameter). Teeth were categorized into 4 groups containing 12 samples in each group based on material used for furcation repair. Group 1 – Endosequence BC RRM-fast set putty; Group 2 – Zirconomer; Group 3-MTA (positive control); Group 4 – negative control. All groups were covered with two layers of clear varnish except for 2 mm around the perforation region. All the teeth were immersed in 2% methylene blue dye for 48 h for dye penetration. Teeth were sectioned buccolingually using a diamond disk. The sectioned teeth were examined under stereomicroscope with ×10 magnification for dye penetration.Results:Endosequence showed less microleakage than MTA but not statistically significant. Zirconomer showed statistically significant higher microleakage.Conclusion:Endosequence and MTA showed less microleakage hence can be used as furcation repair materials. Due to higher microleakage, Zirconomer should be avoided as furcation repair material. Due to its favorable cost, ready availability, and almost similar outcome as bioceramics, MTA is considered as an alternative to Endosequence and is the gold standard in furcation repair.

Effect of blood contamination on the push-out bond strength of four endodontic root perforation repair materials: An in vitro study

Aim: To evaluate the push-out bond strength of four endodontic root perforation repair materials on blood contamination. Materials and Methods: Freshly extracted 80 single-rooted human canine teeth were used. The crowns of all teeth were removed, and the mid-root dentin was sectioned horizontally into slices with a thickness of 1.0mm by using a diamond disk. In 40 samples, a 27-gauge syringe was used to inject blood into the perforated area, which was taken from the patient. Biodentine (Septodont, Pennsylvania, USA) liquid from a single dose container was emptied into a powder-containing capsule and mixed 30 seconds, was mixed in 10 samples; glass ionomer cement (GIC) (GC Fuji IX; GC, Tokyo, Japan) was mixed in 10 samples; ProRoot mineral trioxide aggregate (MTA) (DENTSPLY, Tulsa Dental Specialties, Tulsa, Oklahoma), hand mixed with sterile water at a powder to liquid ratio of 3:1 in accordance with the manufacturer’s instructions, was mixed in 10 samples; and Cavit (ESPE Dental Products, Ohio, USA) was mixed in 10 samples and placed in perforation area. In the remaining 40 samples, normal saline irrigation was performed before restoring 10 samples with Biodentine, 10 samples with GIC, 10 samples with ProRoot MTA, and 10 samples with Cavit. The samples were carried in wet gauze piece and placed in a closed container in an incubator at 370°C and 100% humidity until push-out bond strength was carried out. Results: The result was statistically analyzed using one-way analysis of variance (ANOVA) and Tukey’s post hoc tests. P <0.05 was considered as significant. Conclusion: Push-out bond strength of Biodentine was higher than that of ProRoot MTA, GIC, and Cavit on blood contamination.

Comparative evaluation of enamel abrasivity of different commercially available dentifrices – An In vitro Study

Background: Toothbrushing with toothpaste is a major contributor to dental abrasion. A number of factors such as abrasivity and concentration of the toothpaste, brushing frequency, brushing duration, force of brushing, and toothbrush bristle stiffness have a potential impact on the abrasion process of dental hard tissue. However, the abrasivity of the toothpaste is the most important parameter that affects the abrasion process of dental hard tissue. Aims: This study aims to evaluate the maximum and mean enamel abrasivity of commercially available dentifrices such as Colgate total®, Pepsodent whitening®, Vicco vajradanti®, Dabur red® in primary and permanent teeth. Materials and Methods: Human extracted 60 primary and 60 permanent teeth were randomly selected based on the inclusion criteria. Teeth were sectioned at cementoenamel junction using diamond disc and mounted in an acrylic resin blocks. Baseline profilometric measurements were recorded for all the samples. Four commonly used dentifrices were selected and labeled as Group A (Colgate Total®), B (Pepsodent Whitening®), C (Vicco Vajradanti®), and D (Dabur Red®). Toothpaste slurry was prepared. Tooth specimens were brushed in vitro using a customized brushing machine. After toothbrushing, profilometric measurements were obtained, and the differences in readings served as proxy measure to assess surface abrasion. Data were collected and analyzed using student t-test and ANOVA test. Student t-test was used to compare the enamel abrasivity prebrushing and postbrushing, and ANOVA was used to compare the enamel abrasivity among the four different commercially available toothpastes. Results: In permanent teeth, all the toothpastes were found to cause significant enamel abrasion (P = 0.000) and a significant variation was observed when maximum (P = 0.008) and mean (P = 0.036) enamel abrasivity of these toothpastes were compared. In primary teeth also, all the toothpastes caused significant abrasion (P = 0.000); however, when the maximum and mean abrasivity of these toothpastes were compared, no significant variation was observed (P = 0.438 and 0.163). Conclusions: All the commercially available toothpastes cause significant enamel abrasion. Colgate group caused more enamel abrasion whereas pepsodent caused the least enamel abrasion in permanent teeth.

Evaluating the efficacy of different techniques and irrigation solutions for removal of calcium hydroxide from the root canal system: A scanning electron microscope study.

Aim:The aim of this scanning electron microscope study was to compare the efficacy of two techniques (EndoVac and EndoActivator) and two irrigating solutions (5.25% NaOCl in combination with 17% ethylenediaminetetraacetic acid vs. Savlon™) for removal of calcium hydroxide (CH) from the root canal walls.Settings and Design:The study was carried out in the specialty of conservative dentistry and endodontics.Materials and Methods:Forty single-canal human teeth were used. The specimens were de-coronated to obtain a standardized root length of 15 mm using a diamond disk. The canals were instrumented till F3 ProTaper and CH intracanal medicament placed in the root canal. One week later, teeth were randomly divided into one control group and six experimental groups according to different irrigation protocols with different techniques.Statistical Analysis:Kruskal–Wallis test was conducted to analyze the effect of different treatment measures with respect to three regions of tooth.Results:The results indicated that there was no statistically significant difference between the two irrigation solutions and two techniques.Conclusion:To achieve the best adaptation of filling material after root canal treatment, it is crucial to remove intracanal medication from the root canal walls. However, none of the irrigation regimens and different techniques were able to completely remove the CH from the root canal wall.

A comparative evaluation of shear bond strength of composite resin to pulp chamber dentin treated with sodium thiosulfate and proanthocyanidin: An in vitro study.

Aim:Based on the importance of coronal sealing right after endodontic treatment, this in vitro study aimed to evaluate the difference of shear bond strength to pulp chamber dentin treated with sodium thiosulfate and proanthocyanidin (PA).Materials and Methods:Fifteen extracted mandibular molar teeth were decoronated at the level of cementoenamel junction horizontally. The individual teeth were then sectioned mesiodistally to expose the pulp chamber dentin using a diamond disc. The specimens were randomly divided into three groups (n = 10). Group A: control group, treated with 5.25% sodium hypochlorite (NaOCl) for 30 min followed by a final rinse with 17% ethylenediaminetetraacetic acid (EDTA) solution for 3 min; Group B: after pretreatment with NaOCl and EDTA, it is further treated with 5% sodium thiosulfate (Na2S2O3) for 10 min; and Group C: after pretreatment with NaOCl and EDTA, it is further treated with 6.5% PA for 10 min. After drying the specimens, a bonding agent namely One Coat Bond SL (SwissTEC, Coltene) was applied to the pulp chamber dentin followed by a composite restoration (SwissTEC, Coltene). Each specimen was then tested under a universal testing machine at the dentin/resin interface to determine the shear bond strength.Results:Both the groups in which 5% Na2S2O3 and 6.5% PA were used for 10 min showed bond strength that was found to be statistically higher than the positive control (P < 0.05).Conclusion:The use of Na2S2O3 and PA can significantly increase the bond strength of composite resin to NaOCl/EDTA-treated dentin, allowing adhesive restorations to be immediately applied after endodontic treatment.

Effect of CVD-Coated Diamond Discs on Pad Surface Micro-Texture and Polish Performance in Copper CMP

The effect of pad surface characteristics on the thermal, tribological and kinetic attributes of copper CMP was investigated. Three CMC D100 pads with very different surface micro-textures were generated using three very different CVD-coated diamond conditioning discs. Pad samples were collected after polishing and analyzed for their surface contact area and topography using confocal microscopy. The contact area, contact density, and asperity height increased with increasing conditioner aggressiveness. Copper removal rates and pad surface temperatures increased with increasing polishing pressure and sliding velocity for all pads albeit in a non-Prestonian manner. The pad generated by the most aggressive disc caused the highest removal rates yet it showed the lowest overall coefficient of friction (COF). The tall asperities, open pores, and adequate contact of this pad produced a greater removal rate than pad surfaces with shorter asperities and glazed pores produced by the less aggressive discs. Trends in COF, temperature and removal rate were successfully simulated using a two-step modified Langmuir-Hinshelwood model which also yielded values for the chemical and mechanical rate constants. The simulation results indicated that the process was chemically limited for all polishing conditions, and that the process became even more chemically limited as P × v increased.

Dry sliding wear response of ZrB2-20vol.% MoSi2 composite

Abrasive wear behavior of ZrB2- 20 vol.% MoSi2 composite has been studied using electroplated diamond disk as the counter facing body. The investigated composite has been prepared by hot pressing and it has been found to possess 97% of the theoretical density. The microstructure of the composite has been characterized using scanning electron microscopy (SEM), and results show that MoSi2 particles are uniformly distributed in the ZrB2 matrix. The Young’s modulus, Poisson’s ratio and fracture toughness of the investigated composite are 455 GPa, 0.11 and 4.7MPa√m, respectively. The effect of experimental conditions including applied load, sliding velocity and sliding distance on the tribological behavior of ZrB2- 20 vol.% MoSi2 composite have been investigated. Experimental results show that applied load and sliding velocity plays an important role on specific wear rate and surface roughness of worn surfaces. SEM is used to analyze the wear surface morphology and crack propagation to study the wear mechanism. The dominant mode of wear was identified as abrasion. Grain pullout and micro cracking control the prevailing wear mechanism.

Real-Time Shear and Normal Force Trends in Tungsten Chemical Mechanical Planarization with Different Conditioning Discs

In-situ conditioning is known to increase material removal rate (RR) during chemical mechanical planarization (CMP), because it roughens the pad surface that is in contact with the wafer. Previous studies have shown that the conditioning disc changes the pad surface micro-texture and affects the thermal, kinetic and tribological attributes of the CMP process. This study focuses on two different diamond discs for in-situ conditioning during tungsten CMP, and shows how real-time force data improves our understanding of the effects from using one disc versus the other. Shear and normal forces were analyzed through spectral analysis, variance and force scatter plots. Frequency signatures that appear regardless of the type of disc used were likely attributed to vibrations of the polisher and the harmonics of these vibrations. A new parameter, directivity (Δ), was employed, which highlighted the significant differences in shear force variance between the two discs. Above all, this study confirmed that high Δ correlated with high RR. Compared to a related study on copper CMP with these discs, the trends between Δ and RR seemed to continue to hold.

Effect of Proteolytic Agents on Microleakage of Etch and Rinse Adhesive Systems

Objective: this study aimed to assess the effect of treatment of phosphoric acid etched dentin surface with 5% bromelain enzyme and Nd:YAG laser prior to the use of etch and rinse adhesive systems on microleakage margins of class V composite restorations. Materials and Methods: sixty sound premolar teeth were selected. Standard class V cavities were prepared in the buccal and lingual surfaces of each teeth. Preparation in that way 1 mm of the cavity was above and 1 mm of it was below the cementoenamel junction. The teeth were then randomly divided into three groups including 20 teeth(40cavities in each gorup). Two ethanol base etch and rinse system (Adper Single Bond and OptiBond Solo) was applied in each group. In the control group, cavities were etched with 37% phosphoric acid. Adper Single Bond was applied to 20 and OptiBond Solo was applied to the remaining 20 cavities and they were restored with Z250 composite (n=40). The same procedures were performed in bromelain and Nd:YAG laser groups with the difference that prior to the application of adhesive, aqueous 5% bromelain was applied in bromelain group while Nd:YAG laser was irradiated in laser group. All teeth were thermocycled and their apices were sealed with sticky wax. The tooth surfaces were coated with nail varnish except for 1 mm around the restoration margins, and the teeth were then immersed in fuchsine and sectioned by a diamond disc into mesial and distal halves. Marginal microleakage at both sides was determined and scored under a stereomicroscope at x40 magnification. Then data were analyzed using the Kruskal Wallis and Mann Whitney tests (α=0.05). Results: according the result of Mann Whitney test, Cervical margins showed significantly higher microleakage than the occlusal margins (P=0.000) but no significant difference was noted in microleakage of occlusal (P=0.362) or gingival (P=0.147) margins among the three groups by Kruskal Wallis test. Conclusion: in conclusion, application of proteolytic agents(5% bromelain solution and Nd:YAG laser) on acid-etched dentin surface prior to the application of adhesive has no significant effect on marginal microleakage of class V composite restorations.

A Comparative Evaluation of Shear Bond Strength of Resin-modified Glass Ionomer and Zirconomer Incorporated with 1.5% Doxycycline: An In Vitro Study

Abstract: Aim: The purpose of this in vitro study was to evaluate the shear bond strength of Resin-Modified Glass Ionomer (RMGIC) and Zirconomer incorporated with 1. 5% Doxycycline. Materials and Methods: 40 freshly extracted human molars without any defects were collected. The teeth were mounted in plastic rings of 1 inch diameter with cold cure acrylic resin and the occlusal surfaces were ground flat using a diamond disc with a water coolant at slow speed to expose the dentin. The specimens were then divided into two groups with 20 specimens in each group according to the restorative material used. The restorative materials were mixed with 1.5% Doxycycline, condensed into cylindrically shaped plastic tubes with an internal diameter of 3 mm and a height of 4 mm. In group A, the samples were light cured for 40 seconds. Shear bond strength of all the samples were tested under Universal Testing Machine. Statistical analysis: The results were compared using unpaired‘t’ test to detect significance between groups using SPSS 17.0 software. Results: Statistical analysis showed that RMGIC with 1.5% Doxycycline shows highest shear bond strength (P < 0.05) when compared to Zirconomer with 1.5% Doxycycline. Conclusion: RMGIC with 1.5% Doxycycline showed highest shear bond strength when compared to Zirconomer with 1.5% Doxycycline. Keywords: Doxycycline; GIC; RMGIC; Zirconomer

A dual energy micro-CT methodology for visualization and quantification of biofilm formation and dentin demineralization

ObjectiveThe aim of this study was to induce artificial caries in human sound dentin by means of a microcosm model using human saliva as source of bacteria and to apply a novel dual-energy micro-CT technique to quantify biofilm formation and evaluate its demineralization potential. DesignEight sound third molars had the occlusal enamel removed by cutting with a diamond disk and five cylindrical cavities (±2mm diameter; ±1.5mm depth) were prepared over the dentin surface in each specimen (n=40 cavities). After sterilization, each specimen received the bacterial salivary inoculum obtained from individuals without any systemic diseases presenting dentin caries lesions and were incubated in BHI added of with 5% sucrose for 96h to allow biofilm formation. After that, two consecutive micro-CT scans were acquired from each specimen (40kv and 70kv). Reconstruction of the images was performed using standardized parameters. After alignment, registration, filtering and image calculations, a final stack of images containing the biofilm volume was obtained from each prepared cavity. Dentin demineralization degree was quantified by comparison with sound dentin areas. All data were analyzed using Shapiro-Wilk test and Spearman correlation using α=5%. ResultsDual-energy micro-CT technique disclosed biofilm formation in all cavities. Biofilm volume inside each cavity varied from 0.30 to 1.57mm3. A positive correlation between cavity volume and volume of formed biofilm was obtained (0.77, p<0.01). The mineral decrease obtained in dentin was high (±90%) for all cavities and all demineralized areas showed mineral density values lower than a defined threshold for dentin caries (1.2g/cm3). ConclusionDual-energy micro-CT technique was successful in the quantification of a microcosm human bacterial biofilm formation and to quantify its demineralization potential in vitro.

Sinus Augmentation with Biomimetic Nanostructured Matrix: Tomographic, Radiological, Histological and Histomorphometrical Results after 6 Months in Humans.

Background: Many bone substitutes have been applied for sinus regeneration procedures, such as autogenous bone, inorganic bovine bone, porous and resorbable hydroxyapatite, tricalcium phosphate, bioactive glass, and blood clots. The aim of the present study was a tomographic, histological and histomorphometrical evaluation in humans, of specimens retrieved from sinuses augmented with MgHA/collagen-based scaffolds, after a healing period of 6 months.Materials and Methods: Eleven healthy patients and a total of 15 sinuses were included in this study. The maxillary sinuses were filled with commercial MgHA/collagen-based scaffolds (RegenOss) with a porous three-dimensional (3D) structure (Fin-Ceramica Faenza S.p.A., Faenza, Italy). These grafts have a composite design, that replicate the organization of bone structure, obtained by a technique in which a specific hybrid organic–inorganic composite is spontaneously built by a biological mechanism. The CBCT scans were done before the procedure, after the surgical protocol (T1), and 6 months after sinus surgery (T2) for implantology. Bone specimens were stored in 10% formalin solution, embedded in a glycolmethacrylate resin and sectioned by a high-precision diamond disc. Histologic and histomorphometric analysis were carried out to evaluate the graft reabsorption and bone healing.Results: The mean volume after graft elevation, calculated for each of the 15 sinuses, was 2,906 mm3 in the immediate postoperative period (5–7 days), ranging from 2,148.8 to 3,146.4 mm3. In the late postoperative period (6 months) it was 2,806.7 mm3, ranging from 2,010.9 to 3,008.9 mm3. The sinuses were completely healed and no residual MgHA/collagen-based scaffolds were visible. Osteoblasts appeared actively secreting bone matrix and marrow spaces contained moderate numbers of stromal cells and vascular network. Osteoblasts were observed actively secreting osteoid matrix. The tissues present in the samples were composed of 1.9 ± 1.9% of lamellar bone, 36 ± 1% of woven bone and 58 ± 3.8% of marrow spaces.Conclusion: Mg-MgHA/collagen-based scaffolds can successfully be used for sinus augmentation procedures.

Applying glass ionomer cement to MTA flow™ and biodentine™ and its effects on the interface layer

This study compared the interface layer formation between Glass Ionomer Cement (GIC) with Biodentine™ and between GIC with MTA Flow™. There were 10 samples in each group. Biodentine™ and MTA Flow™ were filled with GIC in plastic molds then incubated at a temperature of 37 °C with 100% humidity for 24 hours. Samples were sectioned vertically with diamond discs and examined using a scanning electron microscope. The statistical analysis was performed using the Mann-Whitney Test. In group 1, 80% of the samples showed a score of 1 and 20% of the samples showed a score of 2. In group 2, 30% of the samples showed a score of 2 and 70% of the samples showed a score of 3. This clinical trial showed that the formation of interface layers in Biodentine™ and MTA Flow™ were significantly different.

The Research into the Effect of Conditions of Combined Electric Powered Diamond Processing on Cutting Power

The paper presents results of the investigation into efficiency of high-tensile composite materials grinding with metal bonded diamond abrasive tools, as well as it demonstrates the necessity to stabilize diamond disks cutting properties in order to reduce cutting power, since it is one of important economic indicators of processing. The comparative analysis of preliminary studies of various diamond processing methods reveals that the minimal cutting power is observed when using the combined method of electric powered diamond processing which includes electrochemical grinding and simultaneous continuous electrochemical dressing of the grinding disk surface. Further research into the suggested method reveals relevant mathematical dependences of metal-bonded diamond disks cutting power and electric modes. The analysis of the results shows that combining of hard-alloy surface electrochemical dissolution and electrochemical dressing of the disk surface facilitates mechanical cutting with high effectiveness and little effort. This leads to substantial reduction of cutting power as compared with other methods. The reasonable electric modes are discovered which provide the minimal cutting power without reducing efficiency of the process and quality of finished product.

Silicon exfoliation by hydrogen implantation: Actual nature of precursor defects

MeV energy hydrogen implantation in silicon followed by a thermal annealing is a very smart way to produce high crystalline quality silicon substrates, much thinner than what can be obtained by diamond disk or wire sawing. Using this kerf-less approach, ultra-thin substrates with thicknesses between 15µm and 100µm, compatible with microelectronic and photovoltaic applications are reported. But, despite the benefits of this approach, there is still a lack of fundamental studies at this implantation energy range. However, if very few papers have addressed the MeV energy range, a lot of works have been carried out in the keV implantation energy range, which is the one used in the smart-cut® technology. In order to check if the nature and the growth mechanism of extended defects reported in the widely studied keV implantation energy range could be extrapolated in the MeV range, the thermal evolution of extended defects formed after MeV hydrogen implantation in (100) Si was investigated in this study. Samples were implanted at 1MeV with different fluences ranging from 6×1016H/cm2 to 2×1017H/cm2 and annealed at temperatures up to 873K. By cross-section transmission electron microscopy, we found that the nature of extended defects in the MeV range is quite different of what is observed in the keV range. In fact, in our implantation conditions, the generated extended defects are some kinds of planar clusters of gas-filled lenses, instead of platelets as commonly reported in the keV energy range. This result underlines that hydrogen behaves differently when it is introduced in silicon at high or low implantation energy. The activation energy of the growth of these extended defects is independent of the chosen fluence and is between (0.5–0.6)eV, which is very close to the activation energy reported for atomic hydrogen diffusion in a perfect silicon crystal.

Putty Index for Tripoding.

Precise orientation and transfer of the selected path of insertion and removal is a critical step in cast removable partial denture prosthesis design. An easy technique for registering the same is described using addition silicon putty and a used diamond disk.

Atomic force microscopy analysis of enamel nanotopography after interproximal reduction.

Interproximal reduction (IPR) removes enamel and leaves grooves and furrows on the tooth surface, which may increase the risk of caries. The aims of this study were to assess the nanotopography of enamel surfaces produced by the most commonly used IPR instruments and to evaluate the effect of polishing after IPR. Enamel slabs were cut from the interproximal surfaces of healthy premolars and then treated with diamond burs, strips, or discs, or Sof-Lex polishing discs (3M ESPE, St Paul, Minn). All samples were cleaned by sonication in distilled water. The control group had no IPR performed and was subjected only to cleaning by sonication. The enamel surfaces were assessed using atomic force microscopy. The IPR instruments all produced surfaces rougher than the control sample; however, the samples that received polishing with Sof-Lex discs after enamel reduction were smoother than untreated enamel (P<0.05 for all comparisons). The larger grit medium diamond burs and medium strips generated rougher enamel surfaces than their smaller grit counterparts: fine diamond burs and fine strips (P<0.001). The difference in roughness generated by mesh and curved disks was not statistically significant (P=0.122), nor was the difference caused by fine strips and mesh discs (P=0.811) or by fine strips and curved discs (P=0.076) (surface roughness values for medium bur, 702±134nm; medium strip, 501±115nm; mesh disc, 307±107nm; fine bur, 407±95nm; fine strip, 318±50nm; curved disc, 224±65nm). The smoothest surfaces were created by use of the entire series of Sof-Lex polishing discs after the enamel reduction (surface roughness, 37±14nm), and these surfaces were significantly smoother than the control surfaces (surface roughness, 149±39nm; P=0.017). Different IPR instruments produced enamel surfaces with varied nanotopography and different degrees of roughness. Enamel surfaces treated with diamond-coated burs were the roughest, followed by diamond-coated strips and diamond coated discs. Polishing with Sof-Lex polishing discs after IPR reduced the enamel surface roughness, and this surface was even smoother than untreated enamel.