Polishing Sequence Research Articles

Effect of Finishing Protocol on Obtaining and Maintaining Gloss in Four Nanohybrid Resin Composites.

Within the clinical objectives of performing direct restorations with resin composites is the achievement of an optimal surface in mechanical terms, while also resembling the natural optical characteristics of dental enamel. The aim of this study is to compare the gloss levels achieved in four nanohybrid resins using four different finishing/polishing (F/P) protocols and assess the retention of gloss after an aging process. Forty-eight A2-colored samples from four commercial brands (Filtek Z250 XT, Tetric N-Ceram, Zafira, and Spectra Smart) were prepared, with 12 specimens per resin. The samples were divided into four subgroups based on the F/P treatment: T1 (clinical polishing sequence with ShapeGuard system), T2 (metallographic polishing sequence), T3 (clinical polishing sequence with PermaSeal), and T4 (final polymerization through glycerin and clinical polishing sequence). Gloss measurements were taken before and after aging.ANOVA one-way was done. Before aging, Z250 showed the highest average gloss in T1 (77.2 gloss units - GU), while Zafira (43.8 GU), Tetric (39.5 GU), and Spectra (33.5 GU) had lower values. In T2, Zafira (92.7 GU) and Spectra (87.4 GU) had the highest average gloss, and Tetric (75.7 GU) and Z250 (78.3 GU) had the lowest. No significant differences were found in T3, and in T4, Z250 had the highest average gloss (78.9 GU), followed by Tetric (74.7 GU) and Zafira (52.5 GU), with Spectra having the lowest (42.7 GU). Control group gloss levels ranged from 61.8 to 71.8 GU and remained consistent after aging, except for Tetric in T1 (p=0.045). The impact of F/P strategies on gloss retention varies with the material, even within the same resin composite classification. The initial gloss level appears to be a more critical factor for long-term gloss retention than the specific F/P protocol used.

Mudgagiri, a Pāla “Jayaskandhāvāra”: An Assessment of Recent Sculptural and Inscriptional Findings at Munger, Bihar

This article explores recently reported inscriptional and sculptural evidence from an early Medieval “Jayaskandhāvāra” i.e. the royal administrative headquarters of the Pāla dynasty, named Mudgagiri (present-day Munger), in Bihar, India. Xuanzang visited Mudgagiri during c. seventh century CE and mentioned the Buddhist vihāras and other sacred structures situated there. Sculptural evidence suggests that in addition to Buddhism, Brahmanical traditions including Śāktism, Vaiṣṇavism, and Śavism were also prevalent during the Pāla period. The practice of worshipping mainstream deities with local names is supported by inscriptional evidence. The depiction of several sculptures reflects the prevalence of revering warrior-like goddesses. The rare image of fleshy and serene Cāmuṇḍā presents one of the many forms of goddess sculpted in the eastern Indian context. The paper also analyses unfinished sculptures to understand the carving and polishing sequence employed by the śilpakāras. The present paper also aims to comprehend the role of “Jayaskandhāvāra” in the socio-political-economic milieu of the Pāla kingdom.

GA-AHP Method to Support Robotic Polishing Process Planning

The finishing stage of mould manufacturing is generally completed via mechanical polishing and manually conducted. Not only is this the most expensive phase of the process but also is currently struggling with a deficit of skilled workers. To address these issues, and support the wider needs of Industry 4.0, the manufacturing community has investigated robotic technologies to support the polishing process. The work reported here, investigating the polishing process planning and optimization for mould manufacture is part of a larger project aiming to automate 80% of the current manual process. Presented in this article is an optimization strategy for robotic polishing process sequencing aiming at satisfying polishing sequence rules and the shortest polishing time simultaneously. A hybrid approach combining both genetic algorithm (GA) and analytical hierarchical process (AHP) is proposed based on the specific characteristics of polishing process sequencing. A multi-objective fitness function is defined using AHP including the calculation of polishing time and evaluation of polishing process rules. The proposed GA-based process sequencing has been successfully demonstrated on test piece examples.

Analysis of surface characteristics of (Y, Nb)-TZP after finishing and polishing.

This in vitro study aimed to evaluate the surface characteristics of a full veneer crown fabricated chairside (CS) from a (Y, Nb)-TZP zirconia block in response to conventional zirconia grinding and polishing. Zirconia crowns (n = 40) were first prepared and divided into two groups of materials: Labside (LS) and CS, after which each specimen went through a five-step grinding and polishing procedure. Following each surface treatment, surface characteristics were analyzed using confocal laser microscopy (CLSM), average surface roughness (Ra) values were processed from the profile data through Gaussian filtering, and X-ray diffraction pattern analysis was performed to evaluate the monoclinic (M) phase content. Then, a representative specimen was selected for field-emission scanning electron microscopy (FE-SEM), followed by a final analysis of the roughness and X-ray diffraction of the specimens using the independent t-test and repeated measures analysis of variance (RM-ANOVA). In every group, polishing significantly reduced the Ra values (P < .001). There was no significant difference in Ra between the polished state CS and LS. Furthermore, CLSM and FE-SEM investigations revealed that even though grain exposure was visible in CS specimens throughout the as-delivered and ground states, the exposure was reduced after polishing. Moreover, while no phase transformation was visible in the LS, phase transformation was visible in CS after every surface treatment, with the M phase content of the CS group showing a significant reduction after polishing (P < .001). Within the limits of this study, clinically acceptable level of surface finishing of (Y, Nb)-TZP can be achieved after conventional zirconia polishing sequence.

Press-On Force Effect on the Efficiency of Composite Restorations Final Polishing—Preliminary In Vitro Study

The surface texture of dental restorations has a major influence on plaque accumulation and aesthetical appearance. The study aimed to evaluate the surface roughness of composite resins depending on the varying polishing sequences and applied forces. A total of 60 samples from two composite resins (Boston and Charisma) were polymerized using a lamp with 1200 mW/cm2 intensity and covering celluloid strip. The polishing sequence consisted of 12.6 mm OptiDisc (Kerr) – with increased disc per each subsequent step. Half of the samples were polished at 1N force, with the other half at 2N. The surface roughness examination was performed using a WYKO NT930 (Veeco) optical profilometer. The selected roughness parameters were compared by ANOVA with the significance level α = 0.05. The more complex polishing sequence affected on the composite smoothness. Higher roughness was identified in Charisma samples as compared to Boston. The specimens polished with 2N force contained a slightly rougher surface than those polished with 1N. However, these differences were not statistically significant. Despite the satisfactory visual effect obtained by polishing the composite samples, the profilometric examination revealed the roughness. Finishing is crucial for providing a smooth composite surface, allowing it to function properly in the oral environment.

Influência da polimerização adicional na microdureza de compósitos diretos para uso indireto: estudo in vitro

The aim of this study was to verify the effect of additional polymerization with microwave and autoclave on the microhardness of 3 different commercial brands of composite resin compared to the ceromere. Cylindrical specimens (6mm x 3mm) were made with a split matrix divided into 10 groups of 13 bodies, with: Photoactivation (LED light on the top surface-40s; photoactivation LED + microwave (500W per 3min) immersed in 100ml distilled water and Photoactivation LED + autoclave (full cycle). The Ceromere group was activated according to the manufacturer's recommendation. The specimens went through a finishing and polishing sequence being stored with a cotton moistened in distilled water for 24h. They were taken to the microhardness meter (three dentations, 50g/15s load). The analysis of variance (ANOVA) was performed with post hoc Games Howell at a level of 5%. It was verified that the ceromere did not differ from the groups Z250 photo and microwave, but was inferior to the Z250 group with autoclave, and the microhardness of this was higher than the other groups. The Tetric group was inferior to all other groups. It was concluded that the additional polymerization methods promoted an increase of the superficial microhardness of the Z250 resin and this did not present a difference of microhardness when compared to the Ceromere

Effect of fluorescent and nonfluorescent glaze pastes on lithium disilicate pressed ceramic color at different thicknesses

Statement of problemMaterials possessing fluorescent properties are assumed to emit sufficient visible light to change tooth color under daylight illumination. Fluorescent and nonfluorescent glaze pastes are available to finish the surface of a pressed lithium disilicate restoration. However, the effect of a fluorescent-glaze layer on the final color of the restoration remains unclear. PurposeThe purpose of this in vitro study was to measure the color dimensions of lithium disilicate glass-ceramic with different thicknesses and different surface treatments under daylight (D65) illumination conditions. Material and methodsA total of 120 pressed lithium disilicate glass-ceramic disks were fabricated with 4 different thicknesses: 0.7, 1.2, 1.7, and 2.2 mm. In each thickness, 3 different subgroups were created based on the surface treatment performed (n=10): polished (NG), clear glaze (CG), and fluorescent glaze (FG). For the NG group, disks were polished with 180-, 320-, 600-, 800-, and 1400-grit SiC papers and a polishing machine. For the glazed groups, the CG and FG groups, the specimens were polished with 180-grit SiC papers and the same polishing machine. After the polishing sequence, the final thickness was verified in all groups by using digital calipers (0.5, 1.0, 1.5, and 2.0 mm). Additionally, 20 μL of clear glaze or fluorescent glaze was applied on the CG and FL groups by using an electronic positive displacement repeating pipette. The glaze layer was crystallized in a furnace according to the manufacturer recommendations. Color measurements in the CIELab coordinates were made with a spectrometer coupled to an integrating sphere and a standardized photography gray card as a background. Color difference (ΔE) values were calculated by using the CIE76 and CIEDE2000 formulas. The Shapiro-Wilk test revealed that the data were normally distributed. Two-way ANOVA and the Bonferroni test for multiple comparisons were used to analyze the data (α=.05). ResultsStatistically significant differences were found among the groups for the L∗, a∗, and b∗ values for the different ceramic thicknesses and surface finishing treatments evaluated (P<.001), except for the b∗ value between the FG and CG groups (P=.988). The L∗ value on the polished group was significantly higher than that on the glazed specimens, followed by the fluorescent-glazed and then by the clear-glazed specimens (P<.001). The ΔE values using the CIE76 formula varied from 0.87 to 2.76 among specimen groups and from 0.32 to 2.34 using the CIEDE2000 among the tested groups. ConclusionsCeramic thickness and surface finishing treatment affected all color dimensions (L∗, a∗, and b∗ values) of lithium disilicate ceramic under daylight conditions. These differences resulted in a perceptible but acceptable color mismatch. The value (L∗ color dimension) of the lithium disilicate ceramic was higher on fluorescent-glazed than on not–fluorescent-glazed specimens.

(Invited) Recent Advances in SiC CMP

The need for high-quality single crystal SiC substrates continues to grow as the demand for SiC-based power and RF devices increases. The physical properties of SiC result in better thermal conductivity, higher breakdown voltage, faster switching performance and lower resistivity when compared to similar devices based on silicon. Even with the performance advantages, the adoption rate of SiC is slowed by high cost and inherent difficulty of processing the material. Conventional processing of SiC substrates involves double-sided batch lapping followed by batch diamond polishing then final polishing with a non-diamond slurry to achieve an epi-ready surface. This process flow involves multiple process tools and is fraught with issues including the need for wafer sorting to group wafers by thickness, manual loading and unloading of wafers, low yields, and unacceptable risk of batch loss (an entire batch of wafers may be scrapped if even one wafer cracks or breaks during process). This paper presents an improved process for single-wafer CMP during SiC substrate manufacturing or backside thinning. In contrast to batch polishing, key improvements include individual wafer processing, fully-automated handling, and elimination of the need for wafer sorting and grouping by thickness. Recent development efforts have achieved removal rates for the 4H Si face up to 2.5 µm/hour for the first step CMP. Removal rates for the C-face can be as much as 3-4x higher consistent with other findings in the industry. Fig 1 shows surface finish after the polishing sequence is complete which is consistently at or below 1 Å Ra as measured by AFM. The combination of an optimized grind followed by an optimized CMP process provides a viable path to both improving wafer yield and reducing costs for SiC wafer manufacturing or backside thinning process sequences. Figure 1

Toward site-specific dopant contrast in scanning electron microscopy.

Since semiconductor devices are being scaled down to dimensions of several nanometers there is a growing need for techniques capable of quantitative analysis of dopant concentrations at the nanometer scale in all three dimensions. Imaging dopant contrast by scanning electron microscopy (SEM) is a very promising method, but many unresolved issues hinder its routine application for device analysis, especially in cases of buried layers where site-specific sample preparation is challenging. Here, we report on optimization of site-specific sample preparation by the focused Ga ion beam (FIB) technique that provides improved dopant contrast in SEM. Similar to FIB lamella preparation for transmission electron microscopy, a polishing sequence with decreasing ion energy is necessary to minimize the thickness of the electronically dead layer. We have achieved contrast values comparable to the cleaved sample, being able to detect dopant concentrations down to 1×10(16) cm-3. A theoretical model shows that the electronically dead layer corresponds to an amorphized Si layer formed during ion beam polishing. Our results also demonstrate that contamination issues are significantly suppressed for FIB-treated samples compared with cleaved ones.

A project of reuse of reclaimed wastewater in the Po Valley, Italy: Polishing sequence and cost benefit analysis

Summary The paper presents a study carried out in the environmentally sensitive area of the Po Valley in northern Italy, with the aim of evaluating, from technical and economic perspectives, a project to reuse part of the final effluent from the Ferrara wastewater treatment plant for irrigation and to develop the site for recreational purposes. Although this area features plentiful supplies of surface water, the Ministry of the Environment has declared it to be at risk of environmental crises due to eutrophication and the drought recurring over the last decade. Thus the availability of fresh water, particularly for agricultural purposes, is threatened, and prompt water saving and protection measures are required. Hence, the possibility of reusing reclaimed wastewater from this plant was investigated, with the aim of exploiting the space around the WWTP, situated within a large urban park, to install natural polishing treatment systems and create green spaces for recreational use. Based on experimental investigation on a pilot plant (featuring both natural and conventional treatments), the study outlines the rationale behind the treatment train selected for the project, details the initial and ongoing costs involved, evaluates the benefits deriving from the project, and assesses public acceptance of the project by the contingent valuation method. A cost–benefit analysis completes the study, and various economic indicators (net present value, benefit–cost ratio, pay-back period, and internal rate of return) revealed that the proposed project was financially feasible.

Investigations to Remove Domes from Plastic Shells by Polishing

A problem often observed for thick wall plastic targets is the presence of surface domes. We have been successful in applying mechanical polishing to remove isolated surface domes from thick wall 2 mm shells during a preliminary investigation. The background surface roughness for polished shells was dramatically improved with final values typically around 10 nm RMS as measured by WYKO patch surface profiles. The polishing sequence applied was also examined using AFM spheremapper data that was obtained for shells after each polishing step. A two-step polishing approach was able to produce shells that had significant improvement in all AFM power modes except for modes (3.10). Further polishing development is needed to reduce AFM low and mid power modes for shells. Polishing of otherwise target quality 2 mm shells that have domes could be a future treatment for NIF targets.

Filter algorithm for influence functions in the computer controlled polishing of high-quality optical lenses

Computer controlled polishing (CCP) is widely used in the production of high-quality optical lenses. CCP enables surface error-profile-dependent calculation of polishing sequences prior to processing, and facilitates the cost-effective manufacture of high-quality optical surfaces. Calculation of an individual polishing sequence requires knowledge of the surface error-profile in addition to knowledge of the material removal characteristic (influence function) of the polishing tool. Measurement errors during both determination of the surface error-profile, and the influence function, may lead to an incorrect polishing sequence calculation, which in turn may result in an inadequate product quality. A new method has been developed which minimises the effects of measurement errors on the influence function. The resulting algorithm renders an influence function symmetrical and filters noisy data. Practical polishing tests with magnetorheological finishing have been performed to verify this new technique. The improvement of the peak-valley (PV) value of the surfaces polished with the symmetrical rendered influence function was observed to average 14% greater than that which related to the PV value improvement of those surfaces which were polished with the unmodified influence function. The algorithm developed is based on software and is easily implemented. Thus, artificial enhancement of an influence function is a straightforward technique to improve the result of the polishing process.

An evaluation of the effects of handpiece speed, abrasive characteristics, and polishing load on the flexural strength of polished ceramics

Many studies on the strengthening effects of grinding and polishing, as well as heat treatment on ceramics, are not well standardized or use commercially available industrial polishing systems. The reported effectiveness of these strengthening mechanisms on ceramics may not be applicable to clinical dentistry. The purpose of this study was to evaluate the effects of controlled polishing on the flexural strength of dental ceramics by using a custom-made machine that applied standardized loads and speeds that coincided with the mean loads and speeds used by experienced prosthodontists. A total of 140 aluminous dental ceramic bar-shaped specimens (Vitadur Alpha Enamel) measuring 1.5 x 2.0 x 25 mm were fabricated and divided into 12 groups (for most groups, n=10). Specimens were untreated, polished with different polishing systems, polished at different speeds, ground and autoglazed, polished and autoglazed, autoglazed and polished, polished with loose (paste) and bonded abrasives, or overglazed. Simulated clinical polishing was performed on the ceramic specimens by using a customized polishing apparatus that allowed independent control over the relevant polishing parameters (abrasive hardness, applied load, linear speed, rotational velocity, and wheel stiffness). Flexural strength (MPa) was measured with a 4-point bending test, and subjective surface roughness was assessed with scanning electron microscopy. Autoglazing was performed at various stages of the polishing sequence to determine the effects of polishing on surface stresses. Mean values, standard deviations, independent-sample t tests, 1-way and 2-way analyses of variance, Dunnett t tests and Kruskal-Wallis tests were applied to the data (alpha=.05). Under a clinical load of 0.6 N for a coarse polishing wheel, 1.0 N for a medium polishing wheel, and 1.3 N for a fine polishing wheel, a linear speed of 499 mm/min, and a rotational velocity of 10,000 rpm, the use of clinical polishing instruments did not affect the flexural strength of the aluminous ceramics studied (P=.274). At higher rotational velocity (20,000 rpm), specimens polished with the diamond polishing system produced statistically weaker specimens compared with those that had been polished at 10,000 rpm (P=.019). Autoglazing treatment of the diamond-polished specimens did not reverse the strength degradation (P=.125). Conversely, diamond polishing of the autoglazed specimens resulted in significant flexural strength reduction (P=.029). Fine-diamond-bonded abrasive significantly reduced flexural strength (P=.025). Simulated clinical polishing at 10,000 rpm did not appear to substantially strengthen or weaken the ceramic specimens. Polishing at 20,000 rpm reduced flexural strength of the ceramic bars.

Study on the planarization behaviour of copper CMP utilizing a dense pattern and a global step

AbstractThe major aim of CMP is not the removal of excess material but the planarization of the surface. Therefore the determination of the planarization length appears to be more important than the removal rate itself. It has been shown, that the planarization length is not a constant process parameter, but is related to the removal respectively to the polish time in a square root behaviour. Founded on models proposed by Boning, Ouma, et. al. we applied a sequential polish on a single quasi infinite step. The resulting profile could be simulated by a sequential convolution of the surface contour with a Gaussian transfer function.To come closer to the situation on a chip pattern we investigated the planarization behaviour on a specific pattern of the MIT854AZ copper CMP test chip, where a large area of unpatterned surface touches a pattern with a specific constant density.The 200 mm wafer samples consisted of RIE structured oxide films covered with 850 nm ECD copper. The polish was performed on a standard semiconductor manufacturing tool, using a commercial consumables set. The surface profiles were determined by a high resolution profiler within the polishing sequence. The densely patterned areas are removed within a certain polishing time while the transition point between the unpatterned and patterned area appears as a global step. The deposited copper thickness is sufficient to study the contour evolution in both phases, before and after removal of the dense pattern. The paper presents the experimental results on the contour evolution for the patterned fields as well as the global step.

Analysis of Microbiological Characteristics of Wastewater Along the Polishing Sequence of a Treatment Plant

Microbial populations were studied by plate counts and flow cytometry along the polishing sequence of a wastewater plant. The comparison between plate count and flow cytometry showed comparable trends, but plate counts detected less than 10% of the total intact bacteria counted by flow cytometry. Six months monitoring showed that, in spite of the high ozone doses, the disinfection effect of ozonation was insignificant. This is in agreement with the variability of ozone demand, not only related to chemical oxygen demand or total suspended solids. Membrane-intact bacterial population decreased after ozonation, slightly regrew between ozone and biological activated carbon (BAC), and sharply increased after BAC, probably for damaged bacteria regrowth and saprophytes release; BAC effluent had the highest bacterial counts. Preliminary investigations on the effluent microbial composition showed that the beta Proteobacteria subclass is the most represented in the BAC effluent, whereas the alpha subclass is the most sensitive to ozone effect.

Lifetime predictions of a titanium silicate glass with machined flaws

A dynamic fatigue study was performed on a Titanium Silicate glass to assess its susceptibility to delayed failure and to compare the results with those of a previous study. Fracture mechanics techniques were used to analyze the results for the purpose of making lifetime predictions. The material strength and lifetime was seen to increase due to the removal of residual stress through grinding and polishing. Influence on time-to-failure is addressed for the case with and without residual stress present. Titanium silicate glass otherwise known as ultra-low expansion (ULE)* glass is a candidate for use in applications requiring low thermal expansion characteristics such as telescope mirrors. The Hubble Space Telescope s primary mirror was manufactured from ULE glass. ULE contains 7.5% titanium dioxide which in combination with silica results in a homogenous glass with a linear expansion coefficient near zero. delayed failure . This previous study was based on a 230/270 grit surface. The grinding and polishing process reduces the surface flaw size and subsurface damage, and relieves residual stress by removing the material with successively smaller grinding media. This results in an increase in strength of the optic during the grinding and polishing sequence. Thus, a second study was undertaken using samples with a surface finish typically achieved for mirror elements, to observe the effects of surface finishing on the time-to-failure predictions. An allowable stress can be calculated for this material based upon modulus of rupture data; however, this does not take into account the problem of delayed failure, most likely due to stress corrosion, which can significantly shorten lifetime. Fortunately, a theory based on fracture mechanics has been developed enabling lifetime predictions to be made for brittle materials susceptible to delayed failure. Knowledge of the factors governing the rate of subcritical flaw growth in a given environment enables the development of relations between lifetime, applied stress and failure probability for the material under study. Dynamic fatigue is one method of obtaining the necessary information to develop these relationships. In this study, the dynamic fatigue method was used to construct a time-to-failure diagram for polished ULE glass.

Development of a sensor information integrated expert system for optimizing die polishing

This paper presents a polishing expert system integrated with sensor information which can modify the polishing sequence and conditions initially set by the system using the on-site polishing status detected. A practical system using AE sensors is developed for rotational and curved-surface polishing. A database and a knowledge base for polishing processes are established by using the results of experiments and also expert's experience. Evaluations are performed for a die of an automobile headlight lamp by using both the sensor-integrated expert system and the expert system without sensor. The results show that the sensor-integrated expert system provides more optimal polishing conditions since the proposed system takes advantage of the on-line sensor information.

The strength of Al 2O 3/SiC nanocomposites after grinding and annealing

Alumina matrix nanocomposites containing about 5 vol.% SiC of <100 nm mean particle size show a substantial increase in strength after machining and annealing. The final strength is controlled by the annealing process and achieves the same level after a coarse machining using 150-grit diamond as is achieved using a complex lapping and polishing sequence. In all cases the final anneal leads to an increase in strength. The nanocomposite retains a significantly higher residual surface-compression stress level than an equivalent grain size alumina after machining. A remnant stress, of about 20% of the initial level, is retained even after 10 h annealing at 1250°C. Hertzian indentation and measurements of Rayleigh wave velocity show that the nanocomposite surfaces contain defects of smaller size and density than are found in equivalent aluminas. Annealing appears to result in healing of existing surface defects thus increasing the nanocomposite strength while leaving its toughness unchanged. The crack-healing mechanism is associated with a chemical process on the nanocomposite surface which has been tentatively identified as an oxidation leading to amorphous mullite formation.

Enamel surfaces after orthodontic bracket debonding.

The enamel surfaces of extracted teeth were studied clinically and with a scanning electron microscope following debonding of orthodontic attachments and subsequent polishing. Excess orthodontic resin was removed with tungsten carbide burs and abrasive discs. Several combinations of polishing agents were evaluated. The no. 30 fluted tungsten carbide bur appeared to be the most efficient method of removing highly filled resin, and it produced the least amount of scarring. A polishing sequence was developed which used resin points and cups followed by a water slurry of fine pumice and brown and green cups. This procedure was tested clinically and appeared to return the enamel to an acceptable condition. This procedure is fast, efficient, and comfortable for the patient.

Dependence of the surface flashover properties of alumina on polishing abrasive parameters

Systematic investigations of the relationship between the surface finish, the polishing medium, and surface flashover properties of high purity polycrystalline alumina ceramics are reported. Samples polished with SiC abrasives displayed a linear behavior, with the breakdown strength increasing with decreasing surface roughness. The breakdown properties of the diamond polished samples were influenced significantly by the polishing sequence adopted; samples polished from coarser to finer finish exhibited erratic surface breakdown properties, whereas the breakdown properties of samples polished from finer to coarser finish varied linearly with respect to the particle size of the abrasive used in the final polishing. These results are discussed in terms of surface and subsurface defects that are formed during diamond polishing. The breakdown properties of the samples in relation to the abrasive type are also analyzed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>