Effect Of Different Polishing Methods Research Articles

Comparative study on the effects of different polishing methods on tooth surface microstructure and roughness following initial periodontal treatment.

To investigate the effects of different polishing methods on the surface microstructure and roughness of teeth following initial periodontal treatment. Teeth were divided into three groups (silica onegloss, polishing disc, and polishing strip) in vitro. Tooth surface microstructure was characterized via scanning electron microscopy. Roughness was measured by profilometry and laser scanning confocal microscopy (LSCM). According to the in vitro results, one group was chosen for further clinical trials. Effects of the chosen polishing method on patient plaque control and satisfaction were assessed via plaque staining and visual analog scale (VAS). Electron microscopy results revealed that the polishing disc group had smoother roots and crowns than did the other two groups. Roughness analysis revealed that the crown roughness with the polishing disc and silica onegloss was lower, and the root roughness with the polishing disc was the lowest (p < .05) The LSCM results showed that the pigment deposition depth with the polishing disc and silicon onegloss in the crowns and roots were significantly lower than those with the other two methods (p = .000). The polishing effect of the polishing disc was best among the three groups. Clinical trials were performed to verify the polishing disc effects. Plaque staining results showed that the decrease in plaque in the polishing disc group was greater than that ofthe rubber cup group (p = .020), which was similar to the results of LSCM. The VAS results showed that the polishing disc made teeth feel smoother, similar to the results of the roughness detection, and the procedure was more comfortable (p < .05). However, there was no significant difference between the two groups regarding foreign body sensation during pronunciation (p = .178). Combining in vitro and in vivo evaluations, the use of a polishing disc following periodontal treatment yielded superior polishing effects on teeth and was better accepted by patients.

The Effect of Different Polishing Methods and Dentifrices on of Resin Composite.

The Effect of Different Polishing Methods and Dentifrices on of Resin Composite.

Effect of different polishing methods applied to denture base materials on microbial adhesion and surface roughness

Aim: The aim of our study was to investigate the effect of various polishing processes applied to different types of PMMA (polymethyl methacrylate) denture base materials on the surface roughness and microbial adhesion of the base material. Methods: Sixty specimens each were prepared from heat-polymerized conventional PMMA (G), heat-polymerized injectable PMMA (E), and prepolymerized CAD/CAM PMMA (C) denture base materials. All sample surfaces were sanded with 800, 1000, 1200, and 2500 grit silicone carbide abrasives. The specimens of each denture base material were divided into three subgroups (n=20) in which different polishing methods were applied. The first group was mechanically polished (M), and the other two groups were chemically polished with light polymerized glaze liquids [Palaseal (Ps), Optiglaze Color (Og)]. A profilometer device was used to evaluate the surface roughness. Colony counting was performed to evaluate bacterial colonization after one day. The data obtained from all these measurements were evaluated using an analysis of variance, and Bonferroni corrected test was used for multiple comparisons of means (p=0.05). The interaction between surface roughness and bacterial colonization was examined by the Pearson correlation test. Regression analysis was performed to determine the relationship between them. Results: When PMMA base materials were compared, the lowest average surface roughness (Ra) values and bacterial colonization values were obtained in Group C. When polishing methods were compared, the lowest average surface roughness values were obtained in Group M. As a result of bacterial colonization measurement, lower colonization values were obtained with standardized mechanical polishing compared to other groups. Conclusion: There was no difference between the different PMMA base materials in terms of surface roughness, but there were statistical differences in bacterial colonization. The results of our study showed that mechanical polishing gave better results than light-activated glazing agents. How to cite this article: Yarar S, Değer Y, Tekin S. Effect of different polishing methods applied to denture base materials on microbial adhesion and surface roughness. J Med Dent Invest 2023; 4: e230351. https://doi.org/10.5577/jomdi.e230351

EFFECTS OF DIFFERENT POLISHING METHODS ON THE COLOR STABILITY OF PORCELAIN: AN IN-VITRO STUDY

Background and aim: As a result, an ongoing study is required to determine the effect of different polishing methods on the color stability of feldspathic porcelain surfaces exposed to four staining solutions at different time intervals in order to determine the most appropriate polishing method that results in better color stability for long periods, which was the goal of this study. Material and methods: This in-vitro study included 80 disc-shaped feldspathic porcelain specimens which were self-fabricated, all the specimens were auto glazed to close any pores, then randomly divided into 4 equal groups of 20 specimens. Specimens of the unpolished group (control group) underwent a removal of their glaze layer, another group was untreated (auto glazed), whereas the other two groups were prepared based on two polishing systems (over-glazed and polished). Specimens of each group (n=20) were divided into 4 groups (n=5) to be immersed in 4 staining solutions (distilled water as a control group, prepared khat extract, prepared red tea, Delsi soft drink). The color measurement of each specimen was assessed before immersion and after 1, 7 and 14 days of immersion. Results: The interaction between unpolished porcelain surfaces and khat extract or red tea showed significant higher increase in color change over time (p&lt;0.05), whereas their interaction with Pepsi or distilled water showed no significant differences (p&gt; 0.05). The interaction between over glazed or auto glazed porcelain surfaces and each stain showed no significant differences over time (p&gt;0.05). Conclusion: Time plays an important role in the discoloration of feldspathic porcelain. Khat has the highest staining ability followed by red tea; however, Pepsi has the lowest staining ability due to the lack of colorant. Over glazed and auto glazed groups showed better prolonged color stability of porcelain surfaces than the polished group; however, the polishing method can be an effective and more preferable alternative as it has acceptable ∆E values and is free from the limitations of glazing methods. Peer Review History: Received: 17 June 2023; Revised: 19 July; Accepted: 28 August, Available online: 15 September 2023 Academic Editor: Dr. DANIYAN Oluwatoyin Michael, Obafemi Awolowo University, ILE-IFE, Nigeria, toyinpharm@gmail.com Received file: Reviewer's Comments: Average Peer review marks at initial stage: 5.5/10 Average Peer review marks at publication stage: 7.0/10 Reviewers: Dr. Sheikh Abdul Khaliq, Department of Pharmacy Practice, Faculty of Pharmacy, Hamdard University, Karachi, Pakistan, drsheikh1974@gmail.com Dr. Bilge Ahsen KARA, Ankara Gazi Mustafa Kemal Hospital, Turkey, ahsndkyc@gmail.com

The effect of different polishing methods on the surface roughness of two scalpel finished resin composites

The effect of different polishing methods on the surface roughness of two scalpel finished resin composites

Effect of polishing methods on the surface roughness of different temporary restorative materials

Aim: The purpose of this study was to evaluate the effects of different polishing methods on the surface roughness of temporary prosthetic restorations. Methodology: In this study, 200 specimens were obtained from Structur 2, Imident, FSM Duo CAD, and Han Temp Crown. All specimens were sanded with 400-, 800-, and 1000-grit silicon carbide. Next, the specimens were divided into five subgroups (n = 10). The specimens in first group were sanded with 1200-, 1600-, and 2000-grit silicon carbide sandpaper. The second group was polished with an aluminum oxide-containing disc. The third group was polished with a diamond-containing pad. A glaze bond was applied to the specimens in the fourth group. The fifth group was glazed with a coat of nano-filled resin. Then, the surface roughness of all specimens was measured with a profilometer. A two-way ANOVA test was performed using SPSS 20.0. Finally, the microstructures of the surfaces were examined by a scanning electron microscope at 5000× magnification. Results: Statistically significant results were obtained between the temporary materials and polishing methods in terms of surface roughness (p &lt; 0.05). For the polishing method, the highest surface roughness values were observed in the control group (0.50 ± 0.15). The lowest surface roughness values were observed in the Equia Forte GC coat group (0.25 ± 0.10). Among the temporary crown materials, the highest roughness was observed in Imicryl specimens. (0.45 ± 0.17), while the least roughness was the polymethyl-methacrylate (PMMA) specimens (0.17 ± 0.10). Conclusion: Surface polishing and finishing procedures might positively affect the surface roughness of temporary materials. Furthermore, materials made via computer-aided design and computer-aided manufacturing (CAD-CAM) demonstrate structural advantages and may be preferable. How to cite this article: How to cite this article: Kavut İ, Uğur M, Tanrıkut ÖO. Effect of polishing methods on the surface roughness of different temporary restorative materials. Int Dent Res 2022;12(3):149-57. https://doi.org/10.5577/intdentres.2022.vol12.no3.7 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

The Effect of Different Polishing Methods on the Surface Roughness of Resin Composites (An In-Vitro Study)

The Effect of Different Polishing Methods on the Surface Roughness of Resin Composites (An In-Vitro Study)

Effect of Polishing on Electrochemical Behavior and Passive Layer Composition of Different Stainless Steels.

In the present paper, the effect of different polishing methods (mechanical and electrochemical) on passive layer chemistry and the corrosion behavior of stainless steels is investigated. It was found that CrNiMo austenites have a substantially better corrosion behavior than CrMnN ones. The nickel is enriched underneath the passive layer, while manganese tends to be enriched in the passive layer. It was also noted that immersion of manganese into an electrolyte preferentially causes its dissolution. It was found that high amounts of chromium (27.4%), molybdenum (3.3%), nickel (29.4%), with the addition of manganese (2.8%) after mechanical grinding, generates a better corrosion resistance than after electrochemical polishing. This is most likely because of the introduction of phosphates and sulfates into its structure, which is known for steels with a high amount of manganese. For highly alloyed CrNiMo steels, which do not contain a high amount of manganese, the addition of phosphates and/or sulphates via the electropolishing process results in a decrease in pitting corrosion resistance, which is also observed for high manganese steels. Electropolished samples show detrimental corrosion properties when compared to mechanically polished samples. This is attributed to substantial amounts of sulfate and phosphate from the electropolishing electrolyte present in the surface of the passive layer.

Effect of different polishing methods on surface roughness of provisional prosthetic materials

Purpose:To evaluate the surface roughness of bis-acrylic and acrylic resins submitted to different methods of polishing.Materials and Methods:Fifty samples of each provisional restorative material (Structur 2, Protemp 4, Duralay, and Dencrilay) were fabricated (10 mm × 2 mm) and divided into five groups (n = 10): (1) positive control group – polyester strip; (2) negative control – unpolished; (3) abrasive tips (Exa-Technique-Edenta); (4) goat hair brush and diamond polishing paste; and (5) silicone tips (Enhance). Each material was mixed and polymerized according to manufacturer's instructions. The parameter evaluated was the arithmetic mean of the surface roughness (Ra) determined using the rugosimeter SJ 301 (Mitutoyo, Japan). The data were analyzed with two-way analysis of variance (post hoc Tukey's test) (P < 0.05).Results:The lowest surface roughness values (0,22–0,90 μm) were observed in the Group 4 – goat hair brush and diamond paste, while the highest values (1,17–1,44 μm) were found in the Group 5 – silicone tips (enhance), with statistically significant differences between them, except for Dencrilay acrylic resin. There was statistically significant difference between bis-acrylic and acrylic resins in the Groups 1, 2, and 4.Conclusions:Within the limitations of this study, it was concluded that the most effective polishing system was the goat hair brush with diamond paste for both bis-acrylic and acrylic resins. The bis-acrylic resins exhibited significantly smoother surfaces than the acrylic resins.

Comparison of different polishing methods on the surface roughness of microhybrid, microfill, and nanofill composite resins.

The aim of the present study was to evaluate the effect of different polishing methods on the surface roughness of resin-based composites subjected to a thermocycling procedure. A total of 192 specimens were divided into 24 groups, according to composite materials (Filtek Z250, Point 4, Renamel Nanofill, Filtek Supreme Plus, Renamel Microfill, and Premise) and finishing and polishing systems (Sof-Lex Pop On, Super Snap, Flexidisc, and Flexidisc+Enamelize). The specimens were subjected to thermocycling (5000 cycles). Filtek Supreme Plus showed the lowest surface roughness values before thermocycling. After thermocycling, Filtek Supreme Plus continued to have the lowest surface roughness, with a statistically-significant difference for the other materials. After thermocycling, there was no statistically-significant difference among all the polishing techniques studied. The thermocycling was concluded as being able to change composite resins' surface roughness, whereas different finishing and polishing methods did not result in surface roughness changes after thermocycling.

Effects of three different bleaching agents on microhardness and roughness of composite sample surfaces finished with different polishing techniques.

BackgroundThe aim of this study was to evaluate effects of different polishing methods and whitening agents on surface hardness and roughness of nano-hybrid composite resin. Material and MethodsIn total, one hundred twenty disc-shaped specimens were prepared to nano-hybrid composite (Charisma Diamond). 60 samples were used for microhardness measurements and the others were used for the evaluation of surface roughness. Samples were divided randomly into two subgroups (n = 30 each). In first group a low-viscosity liquid polishing agent (Biscover LV) was applied. In the second group, nothing was applied. All the samples were stored in distilled water at 37°C for 24 h. After initial measurements were completed, samples were divided randomly into three subgroups for bleaching application. 10% carbamide peroxide (Opalescence PF), 45% carbamide peroxide (Opalescence PF Quick), 38% hydrogen peroxide (Opalescence Boost) was applied. Then microhardness and surface roughness measurements of samples were repeated and data were recorded as final values for each sample.ResultsWhen the polishing techniques were compared, no signicant difference was observed in surface hardness and roughness. When the bleaching agents were compared, the 10% carbamide peroxide and 38% hydrogen peroxide containing bleaching agent groups showed statistically significant differences between pre- and post-procedure hardness values (p<0.05).ConclusionsOffice-type bleaching agent containing CP was observed to be more secure for composite resins than other bleaching agents. No negative effect of glaze materials on the protection of surface roughness and hardness of composite resin was observed. Key words:Composite resin, bleaching, surface hardness, surface roughness.

Effect of surface sealant agents on the surface roughness and color stability of denture base materials

Statement of problemThe effects of surface sealant agents on the surface roughness and color stability of denture base materials are unknown. PurposeThe purpose of this in vitro study was to evaluate the effects of different polishing methods on the surface roughness and color stability of denture base materials. Material and methodsA total of 120 specimens were fabricated from 2 poly(methyl methacrylate) (PMMA) and 1 polyamide denture base materials and divided into 4 groups (n=10 in each group) according to the applied surface treatment procedure: conventional polishing (control) and 3 surface sealant coupling methods. Surface roughness average (Ra) values were measured using a profilometer. Color parameters were measured using a spectrophotometer before and after being stained with coffee. Color differences (CIEDE 2000 [ΔE00]) were calculated. Data were statistically analyzed using 2-way ANOVA and Tukey honest significant difference test (α=.05). ResultsNo statistically significant difference were found between surface roughness values of the control and those of the specimens treated using a surface sealant agent (P>.05). The highest color difference was calculated for the polyamide control group. Statistically significant differences were found between the control group and the group treated with the polyamide surface sealant agent (P<.05). ConclusionsAll specimens had a surface roughness value higher than the plaque accumulation threshold (0.20 μm). The color changes observed were clinically unacceptable, except for conventionally polished and one type of surface sealant applied microwave polymerized PMMA denture base material.

Effect of different surface treatment methods on the surface roughness and color stability of interim prosthodontic materials

Statement of problemThe effects of surface sealant agents on the surface roughness and color stability of interim crown materials are unknown. PurposeThe purpose of this in vitro study was to evaluate the effects of different polishing methods on the surface roughness and color stability of 4 interim crown materials. Material and methodsA total of 160 specimens were fabricated from 2 poly(methyl methacrylate) (PMMA; Tab 2000, Dentalon Plus) and 2 bis-acryl (Tempofit, Protemp 4) interim crown materials and divided into 4 groups (n=10) according to applied surface treatment procedures: conventional polishing (control) and 3 surface sealant (Palaseal, Optiglaze, Biscover) coupling methods. Surface roughness (Ra) values were measured with a profilometer. Color parameters were measured with a spectrophotometer before and after staining in coffee. Color differences (CIEDE 2000 [ΔE00]) were calculated. Data were statistically analyzed with 2-way ANOVA and the Tukey honest significant differences test (α=.05). ResultsThe Ra values of Tempofit with Biscover were significantly lower than their control group, Tab 2000 and Dentalon Plus control groups (P<.05). The highest ΔE00 was calculated for Tempofit control (P<.05). The Dentalon Plus control group had significantly higher ΔE00 values than the other groups, except for the Tempofit and Tab 2000 control groups.The Tab 2000 control ΔE00 was significantly higher than the other groups, except for Dentalon Plus with Palaseal and Dentalon Plus with Optiglaze. ConclusionsAll specimens had a surface roughness higher than the plaque accumulation threshold (0.20 μm). Smoother surfaces were observed for Tempofit with Biscover when compared with theTempofit control. The color change observed with the Dentalon Plus, Tab 2000, and Tempofit control groups was clinically unacceptable. Nonperceivable color changes were seen with Protemp 4 with Optiglaze, Tempofit with Optiglaze, and Tempofit with Biscover. Perceivable but clinically acceptable color changes were observed when sealants were used for all other test groups and Protemp 4 control.

Effect of Different Polishing Methods on Anodic Titanium Dioxide Formation

Among various methods of synthesis of nanostructured TiO2, a self-organized anodization is the most commonly used and discussed in the literature. However, different methods of pretreatment of Ti before anodic titanium dioxide (ATO) formation are not often addressed. Therefore, various polishing procedures based on mechanical, chemical, electrochemical, and combined electrochemical with chemical pretreatments were examined to establish whether they represent effective methods for smooth Ti surface preparation before anodization. The ATO layers were prepared via two-step anodization carried out in an ethylene glycol solution containing fluoride ions at 20°C and under the anodizing potential of 60 V. The influence of applied polishing method on the cell size, pore diameter, pore circularity, pore density, and porosity of the top ATO layer was studied. In addition, the effect of polishing procedure on cell arrangement in ATO films was also investigated. The quantitative analyses of the regularity of cell arrangement, based on the regularity ratio derived from bottom-view SEM images, showed that the type of polishing procedure does not affect the cell order.

Effects of Polishing Methods on Candida albicans Adhesion on Cast Pure Titanium Surfaces

To explore the effects of different polishing methods on Candida albicans adhesion to cast pure titanium surfaces. Pure titanium test specimens randomly divided into 4 groups: not specially treated (CT), manual polishing (MPT), electrolytic polishing (EPT), and centrifugal barrel polishing (CPT). Surface roughness was measured with surface profilometer. Contact angles of water, diiodomethane, and ethylene glycol on specimen surface were measured, and the free energy was calculated. Each group were immersed in a C. albicans suspension for 48 hours, and cell count of C. albicans adhesion were taken. Morphology of C. albicans adhesion was observed by SEM. Surface roughness (Ra) were in the following order: CT > EPT > MPT > CPT. The amount of C. albicans adhesion to the surface of CPT was significantly less than CT, MPT, and EPT by cells count (P < 0.05). In SEM, less C. albicans aggregation formed on the surface of CPT than other 3 groups. Specimens treated by the CPT method showed superior effect to the specimens treated with MPT and EPT methods in reducing the adhesion of C. albicans.

Effects of different polishing methods on color stability of resin composites after accelerated aging

The purpose of this study was to evaluate the effect of polishing procedures on the color stability of different types of composites after aging. Forty disk-shaped specimens (Ø10×2 mm) were prepared for each composite resin type (an ormocer, a packable, a nanohybrid, and a microhybrid) for a total of 160 specimens. Each composite group was divided into four subgroups according to polishing method (n=10): control (no finishing and polishing), polishing disk, polishing wheel, and glaze material. Color parameters (L*, a*, and b*) and surface roughness were measured before and after accelerated aging. Of the polishing methods, glazed specimens showed the lowest color change (∆E*), ∆L*, and ∆b* values (p<0.05). Of the composite resins, the microhybrid composite showed the lowest ∆E* value, whereas the ormocer showed the highest (p<0.05). For all composite types, the surface roughness of their control groups decreased after aging (p<0.05). In conclusion, all composite resins showed color changes after accelerated aging, with the use of glaze material resulting in the lowest color change.

Effects of polishing procedures on color stability of composite resins

The purpose of this study was to investigate the effect of different polishing methods on color stability of posterior, universal and nanohybrid composite resin restorative materials upon exposure to a staining agent. Twenty-five specimens were prepared for each of 5 different composite resins (Filtek Z250, Filtek P60, Quadrant LC, Grandio and Filtek Supreme). Specimens were divided into 5 groups and different polishing procedures, including polishing discs (Pd), polishing discs then diamond polishing paste (PdP), polishing discs then a liquid polishing system (Biscover) (PdB), and combinations of these (PdPB) were used. Unpolished specimens served as the control (C). The specimens were stored for 48 h in a coffee solution. The color of all specimens was measured before and after exposure with a colorimeter, and total color change ∆E*) were calculated. The data were analyzed with a two-way ANOVA and the means were compared by Tukey HSD test (α=0.05). The lowest color difference was observed in the groups PdP and C, while the highest color difference was observed in PdPB, and PdB. When comparing the five different restorative materials, no significant difference was observed between FiltekP60 and FiltekZ250, and these materials demonstrated significantly less color change than Quadrant LC and the nanohybrid materials (Grandio, Filtek Supreme). The posterior (Filtek P60) and universal (Filtek Z250) composite resin restorative materials, which do not contain tetraethyleneglycol dimethacrylate (TEGDMA), were found to be less stainable than the nanohybrid (Grandio, Filtek Supreme) and universal (Quadrant LC) composite resins, which contain TEGDMA. The use of diamond polishing paste after polishing with polishing discs significantly decreased staining when compared to the groups that used polishing discs alone, for all restorative materials tested. The highest color change values were obtained for the specimens that were polished with the Biscover liquid polish system (PdB and PdPB groups).

Effects of various finishing procedures on the staining of provisional restorative materials

The color stability of tooth-colored restorative materials for provisional restorations is of primary importance when provisional prostheses are worn long term. However, the effect of different polishing methods on the color difference of provisional restorative (PR) materials has not been completely clarified. The purpose of this study was to investigate the effect of different polishing methods on color stability of 2- and 3-component autopolymerized bis-acrylic composites, a light polymerized composite, and a methyl methacrylate-based PR material upon exposure to a staining agent. Material and methods Sixty cylindrical specimens (15 x 2 mm) were prepared for each of bis-acryl composites (Protemp II and Luxatemp), a light-polymerized composite (Revotek LC), and a methyl methacrylate-based (TemDent) PR material by using a brass mold. The specimens were divided into 6 groups (n=10), and different polishing procedures were used, including pumice (P), diamond polishing paste (Dpp), polishing discs (Pd), and combinations of these. Unpolished specimens served as the control. The specimens were stored for 48 hours at 37 degrees C in a coffee solution. The color of all specimens was measured with a colorimeter (Minolta CR-300) before and after exposure, and color changes (DeltaE) were calculated. The data were analyzed with a 2-way analysis of variance, and mean values were compared by the Tukey Honestly Significant Difference test (alpha=.05). The provisional materials, surface polishing procedures, and interaction were significant (P <.05). In the light-polymerized composite group, the lowest color difference (DeltaE) was observed in Group P-Dpp (4.9) and Group P (5.3), which were not significantly different from each other. In the autopolymerized bis-acryl composites and the methyl methacrylate-based provisional materials, the lowest color difference (DeltaE) was observed in Group P-Dpp. The largest color difference for the light-polymerized and autopolymerized composites was observed in Group Pd-Dpp and Group Pd, which were not significantly different from each other. In the methyl methacrylate-based material group, the largest color difference was observed in Group Pd. When comparing the 4 different PR materials, the methyl methacrylate-based material group demonstrated statistically significantly less color change than the other provisional material tested. The methyl methacrylate-based PR material (TemDent) was found to be more color stable than the autopolymerized (Protemp II and Luxatemp) and light-polymerized (Revotek LC) composites tested. The use of diamond polishing paste after polishing with pumice significantly decreased the staining of methyl metacrylate and bis-acryl composites tested. The highest color-change values were obtained in the groups polished with polishing discs, which were found to be significantly different compared to values obtained with other polishing techniques.

SEM investigation of polishing composite restorations

Proper finishing and polishing of composite restaurations are procedures that enhance the quality of restorations and reduce plaque accumulation. The purpose of this study was to evaluate with SEM analysis the effect of different polishing methods and instruments of composite surface after polishing. We used different instruments for finishing and polishing: carbide tungsten burs, diamond fissural burs, steel fissural burs, Lo-Flex Pop On discs, Sof-Lex Pop On discs, Hawe rubber cups, gray rubber cups, green rubber cups, polishing strips, polishing pastes. The results we obtained showed that the most efficient polishing of composite restorations was achieved after treatment with Sof-Lex discs, rubber cups and pastes. Treatment with carbide tungsten burs, was the least effective, producing the lowest smoothness of composite surface.

Effects of different polishing methods on the reflectance of silicon

Silicon, which was introduced as a reflectance standard by the COM in 1966, was withdrawn some years later following reports that its reflectance varied depending on how it was polished and how it was cleaned. For this reason, and because most of these standards were used in double-beam microscope-photometers, where measurements in oil are not made and cleaning is reduced to a minimum, the COM, at its meeting in Varna in 1982, approved their use in such instruments. Approval was withheld for their use in single-beam instruments. Prior to this it was decided to undertake an inter-laboratory study of the influence of different polishing procedures on the reflectance of silicon. A single crystal of silicon was cut into twenty pairs of samples. One of each pair was polished and the other lapped with 3 μm abrasive. Both were sent to the National Representatives of the COM. Fourteen of these completed the polish of the 3 μm lapped sample and measured its reflectance before returning it to the coordinator of the experiment together with their reflectance values for the other sample. The majority of those participating completed their polishing with abrasives of grain size of about 0.05 μm and reported reflectances at 546 nm of approximately 37% on these well polished samples — in keeping with values determined ellipsometrically and by two independent sets of reflectance measurements made in the coordinating laboratory. Where, in other laboratories, coarser grits were used for the final stage −3, 0.25, or 0.1 μm — the surfaces produced were decidedly scratched and reflecrances measured on them ranged from 39–44%. The inverse relationship between reflectance and the quality of the polished surface is contrary to that observed with most opaque minerals. The results of this experiment do not support the argument that water, compared with oil, as lubricant, inevitably reduces the reflectance of silicon, rather it is the grit size and quality of the polish that is most significant in this respect.