Corstai

Pinar Kursoglu, D

aAssociate Professor, Department ofbPhD student, Department of ProsthcProfessor, Department of Prosthodo

Kursoglu et al

relation of surface texture with thenability of ceramics

DS, PhD,a Pelin F. Karagoz Motro, DDS, MSc,b

and Ender Kazazoglu, DDS, PhDc

Faculty of Dentistry, Yeditepe University, Goztepe, Istanbul, Turkey

Statement of problem. Stainability is an important factor in the long-term clinical success of ceramic restorations. Contouradjustments on restoration surfaces cause differences in ceramic texture that may be affected differently by the staining agent.

Purpose. The purpose of this study was to evaluate the surface texture obtained by different surface treatments relevant to thestainability of heat-pressed leucite-reinforced ceramic disk-shaped specimens.

Material and methods. Sixty-six ceramic disks (IPS Empress Esthetic) (15�2 mm) were prepared, glazed, and then assignedto 6 groups. All disks were abraded with a diamond rotary cutting instrument except group GG (control), which was notsubjected to any procedure.Group R (rotary diamond cutting instrument) was left untreated after abrasion. Group PB was polished with an abrasivestone, a round polishing brush, and paste with felt wheels. Group PU was polished with 1.0- to 0.5-mm polishing pastes witha goat-hair brush. Group PS was polished with abrasive stone, silicon carbide polishers, and polishing paste with polishingdisks. Group GR was reglazed. Surface roughness was measured with a profilometer and evaluated with scanning electronmicroscopy. A spectrophotometer was used before and after 12 days of immersion in a coffee solution to assess colordifference. Data were analyzed by 1-way ANOVA, the Tukey honestly significant difference test, and the Pearson rankcorrelation tests (a¼.05).

Results. Ra values of groups from highest to lowest were, in order, R, PB, PU, PS, GR, and GG (P<.01). Scanning electronmicroscope images and Ra values were compatible. The color difference (DE) values of groups from highest to lowest were, inorder, R, PB, PU, PS, GR, and GG. A positive significant relationship of 65.6% between the Ra and DE values was found(P<.01).

Conclusions. Ceramic staining may be related to surface texture. The use of appropriate polishing materials with compatibleporcelain may reduce stainability. (J Prosthet Dent 2014;-:---)

Clinical ImplicationsThis study found that surface stainability is correlated with surfacetexture. Smooth surfaces, which can be obtained by reglazing orpolishing, are essential to avoid the staining of ceramic restorations.

The increased demand for estheticceramic restorations has been attributedto their superior optical properties, in-creased translucency, and improved es-thetics.1-3 Strong preferences for estheticdentistry and biocompatible materialshave increased the public demand forceramic restorations relative to othermaterials.4

Prosthododontics.ntics.

Ceramic surfaces are smooth be-cause of the glazing procedure used infinal finishing.5-7 However, the achieve-ment of acceptable occlusion may re-quire adjustment of the restoration withrotary cutting instruments after inser-tion.8-15 Such adjustment can removethe glazed layer, which exposes the poresof the ceramic material, producing

ontics.

a rough surface16 that may result indiscoloration of the restoration andrequire reglazing or polishing aftergrinding.17-22 The powder/liquid mixingratios used to produce porcelain slurrieswith layering techniques vary accordingto the technician’s experience.23 Thisratio affects the total porosity.24,25

Pressable materials (IPS Empress;

Table I. Surface treatment materials

Group Name Product Manufacturer

Group R (rotary diamondcutting instrument

group)

Red-ring 30-mm diamond rotarycutting instrument

Komet, Gebr BrasselerGmbH & Co KG

Group PB (polishinggroup Bredent)

Diagen-Turbo-GrinderAbraso-Fix (fine)

Diamant-PolierpasteFelt wheels 123

Bredent

Group PU (polishinggroup Ultradent)

Diamond Polish MintJiffy goat-hair brushes

Ultradent Products Inc

Group PS (polishinggroup Shofu)

Dura-Green stonesCeraMaster coarse

CeraMasterUltra II porcelain polishing paste

Super-Snap Buff Disk

Shofu Inc

Group GG (glazing group)Group GR (reglazing

group)

IPS Empress Universal Glaze andliquid IPS Empress Universal

Stain Liquid

Ivoclar Vivadent

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Ivoclar Vivadent) have been claimed toexhibit less porosity.26,27 In addition,pressing effectively eliminates pores incomparison with pre-pressing ceramicmaterials.28

An appropriate color combinationand color stability are important clin-ical factors in esthetic dental restora-tion.5-7 Color differences (DE) can bedetected either with the naked eye orwith the aid of instruments.29-33 Theuse of the Commission Internationalede l’Eclairage (CIE) L*a*b* color ordersystem has been reported frequently inthe dental literature.34-43 Several studieshave examined DE values, but no con-sensus on clinically acceptable limitshas been reached.39,44-49 Many studieshave evaluated ceramic color and colorstability by investigating the effects ofrepeated firing,50 ceramic aging,51 andceramic surface texture52 on color.However, few have reported the effectof surface roughness (Ra) on color inheat-pressed, leucite-reinforced ceramicmaterials after exposure to a stainingsolution.17,39,42

Thus, the purpose of this study wasto determine the effects of surface tex-tures obtained by using various surfacetreatments on the stainability of heat-pressed, leucite-reinforced ceramics.The null hypothesis of this study wasthat surface roughness is not correlatedwith the stainability of heat-pressed,leucite-reinforced ceramics.

MATERIAL AND METHODS

Wax pattern disks (15�2.0 mm)were fabricated. They were invested andheated, and 60 heat-pressed, leucite-reinforced ceramic disk specimens (IPSEmpress Esthetic ETC1; Ivoclar Viva-dent) were pressed to a thickness of2.0 mm and a core diameter of 15 mmin an EP600 press furnace (IvoclarVivadent), according to the manufac-turer’s instructions. Disk-shaped speci-mens were exposed to airborne-particleabrasion with 50-mm aluminum oxideat 0.2-MPa pressure.

The surfaces of the specimens werewet-ground with 220-, 320-, 500-, 600-,and 800-grit silicon carbide paper

The Journal of Prosthetic Dentis

(English Abrasives) and a grinding de-vice (Phoenix Beta). All specimens wereglazed (IPS Empress Universal Glazeand Stain Liquid; Ivoclar Vivadent) ac-cording to the manufacturer’s instruc-tions and then divided into 6 groups(n¼10; Table I). To imitate clinicaladjustment, specimens in all groupsexcept GG were abraded with a 30-mmdiamond rotary cutting instrument(Red-ring Komet; Gebr Brasseler GmbH& Co KG) with a high-speed handpieceat 20000 rpm under water cooling.

Specimens in group R were leftuntreated after abrasion with the dia-mond rotary cutting instrument. Thosein group PB were polished with anabrasive stone (Diagen-Turbo-Grinder;Bredent), round polishing brush (Abraso-Fix, fine; Bredent), and diamondpolishingpaste (Diamant-Polierpaste; Bredent)with felt wheels (Bredent). Specimensin group PU were polished with 1.0-mmand 0.5-mm polishing pastes (Dia-mond Polish Mint; Ultradent ProductsInc) and a goat-hair brush (Jiffy;Ultradent Products Inc). Those ingroup PS were polished in the fol-lowing order with an abrasive stone(Dura-Green Stone; Shofu Inc), coarsesilicon carbide polisher (CeraMaster,coarse; Shofu Inc), silicon carbidepolisher (CeraMaster; Shofu Inc), andpolishing paste (Ultra II; Shofu Inc)

try

with polishing disks (Super-Snap BuffDisks; Shofu Inc). The same investi-gator used all polishing instrumentswith a slow-speed rotating handpiece(KaVo K5plus; KaVo Dental GmbH) at10 000 rpm for approximately 20 sec-onds. Specimens in group GR werereglazed (IPS Empress Universal Glazeand Stain Liquid; Ivoclar Vivadent).Those in group GG were not subjectedto further treatment after glazing andserved as the control group.

All specimens were cleaned with asteam cleaner (Triton SLA; Bego) under0.3-MPa pressure and then placed in anultrasonic cleaner (CD-4800 DigitalUltrasonic Cleaner; Jeken) for 180 sec-onds. A profilometer (Mahr GmbH)was used to measure Ra in microme-ters. One specimen from each groupwas coated with gold-palladium alloyand examined by field-emission scan-ning electron microscopy (SEM) (JSM-6335F; JEOL) to evaluate the effects ofpolishing and glazing the porcelainsurfaces. SEM microphotographs weremade at �1000 magnification for vi-sual inspection.

Before and after immersion in acoffee solution, the color parameters ofeach specimen were measured with aspectrophotometer (CM-2600d; Kon-ica Minolta Sensing Inc) according tothe CIE L*a*b* color order system.

Kursoglu et al

Table II. Mean and SD of surface roughness (Ra) and differences betweengroups

Group Ra ±SD (mm) Difference*

R 1.32 �0.15 a

PB 1.15 �0.09 b

PU 0.83 �0.02 c

PS 0.56 �0.02 d

GR 0.05 �0.02 e

GG 0.04 �0.00 f

F¼1341.45

R, rotary diamond cutting instrument group; PB, polishing group Bredent; PU, polishing groupUltradent; PS, polishing group Shofu; GG, glazing group; GR, reglazing group; SD, standard deviation.*Different letters indicate statistically significant difference between groups (P<.01).

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The coffee solution was preparedaccording to the manufacturer’s in-structions by using 3.6 g of coffee and300 mL of hot water (Nescafe Classic;Nestle Turkiye). The solution was stir-red with a stick for 10 minutes andpassed through filter paper (Melitta;Melitta Haushaltsprodukte GmbH &Co Kg). In the interval between the2 color measurements, all specimenswere stored in coffee solution in anincubator (UM 400; Memmert GmbH)at 37�C for 12 days, which is equivalentto 1 year of coffee consumption.35,36,53

The solution was stirred every 12 �1hours. After 12 days, the specimenswere washed with tap water and driedwith tissue paper (Selpak; Eczacıbası).Software (SpectraMagic 3.1) was usedto calculate DE: DE2-1¼[([DL]2

þ[Da]2þ[Db]2)½.Comparisons among groups were

performed with 1-way ANOVA, and theTukey honestly significant difference(HSD) test was applied to any groupthat showed a discrepancy. The effectsof polishing technique on color varia-tion were evaluated with the Pearsonrank correlation test. Data were testedat a¼.05.

RESULTS

Surface roughness

The means and standard deviationsof Ra values (in micrometers) and theTukey HSD test results are shown inTable II. From the highest to lowest Ravalue, the groups were ordered as fol-lows: R, PB, PU, PS, GR, and GG. The1-way ANOVA results indicated thatsurface treatment affected Ra (P<.01).Ra values were highest in group R andlower in group PS than in the unglazedpolished groups (PS and PU; P<.01).These values were significantly higher ingroup GR than in group GG (P<.01).

Adjustment with a diamond rota-ry cutting instrument (group R) creat-ed the roughest surfaces. Polishingsmoothed the scratches left by thediamond rotary cutting instrument(groups PB, PU, PS). Smoother surfaceswere obtained with polishing materials

Kursoglu et al

and paste (Shofu Inc) than with otherpolishing materials. SEM microphoto-graphs showed that the smoothestsurfaces were obtained in group GG,followed by group GR (Figs. 1-6).

Color differences

The 1-way ANOVA and the TukeyHSD test results for the means andstandard deviations of DE values areshown in Table III (P<.01). From thehighest to lowest DE value, the groupswere ordered as follows: R, PB, PU, PS,GR, and GG. No significant differencein DE values was observed between theglazed groups (GG and GR) or amongthe polished groups (PB, PU, PS; bothP>.05). DE values were significantlylower in group GG than in groupsR (P<.01), PB (P<.01), PU (P<.01),and PS (P<.05). No significant differ-ence was found between group PS andgroup GR (P>.05). These values weresignificantly lower in group GR than ingroups R (P<.01), PU (P<.05), andPB (P<.05). DE values were signifi-cantly lower in group PS than in groupR (P<.05). No significant differencewas observed among groups R, PB, andPU (P>.05).

The Pearson correlation analysisfound a 65.6% positive significant rela-tionship between the Ra and DE values(P<.01; Fig. 7). The staining agentaffected rough surfaces more thansmooth surfaces. Group R showedthe most staining and the roughest

surfaces, whereas group GG showed theleast staining and the smoothestsurfaces.

DISCUSSION

This in vitro study measured thestainability of ceramic specimensfinished with different polishing tech-niques and glazing after immersion incoffee solution. Based on the results,the null hypothesis that Ra is notcorrelated with ceramic stainability wasrejected, because a 65.6% positive sig-nificant correlation was found betweenRa and color difference values.

The appropriate finishing of dentalrestorations is important to enhancethe esthetics and longevity of restoredteeth. Contour adjustments to varioussurfaces, for example, facial or incisal-occlusal surfaces, disrupt the glazedsurface. Some studies have foundthat glazing provides sufficient surfacesmoothness in ceramic restorations,8,19,20

and others have demonstrated thatpolishing with instruments such asdiamond rotary instruments and rub-ber abrasives can also provide clinicallyacceptable smoothness.18,20,22 The re-ported disadvantages of firing to reglazeceramics after adjustment include thetime-consuming nature of the procedure,resulting color changes, and porcelaindevitrification. Thus, the use of differentabrasive stones, abrasive rubber points,and pastes has been recommendedinstead of reglazing.8-11,19,21 The use

1 Scanning electron microscope microphotograph(�1000 magnification of group R, rotary diamond cuttinginstrument group).

2 Scanning electron microscope microphotograph(�1000 magnification of group PB, polishing groupBredent).

3 Scanning electron microscope microphotograph(�1000 magnification of group PU, polishing groupUltradent Products Inc).

4 Scanning electron microscope microphotograph(�1000 magnification of group PS, polishing groupShofu Inc).

4 Volume - Issue -

of polishing kits and systems has alsobeen recommended to obtain goodesthetics.18,20,22 The use of silicon car-bide rubber points produced a bettersurface than the use of polishing pasteand disks.12,13

Aykent et al14 evaluated the effectsof 4 surface treatments on Ra in Vita-blocks Mark II (Vita Zahnfabrik) andfound that the roughest surfaces wereproduced by abrasion with a diamondrotary cutting instrument, followedby the application of diamond paste,

The Journal of Prosthetic Dentis

silicon carbide rubber points (ShofuInc), and Sof-Lex abrasive disks (3MESPE). Sarikaya and Güler13 deter-mined the Ra values of 4 porcelainmaterials subjected to several surfacetreatments. They found that the use ofpolishing kits and disks reducedroughness more effectively than theapplication of polishing paste withdisks alone.

The findings of the present studyindicate that polishing did not achieveadequate surface smoothness in

try

comparison with glazed surfaces.Specimens that were left untreated afterabrasion with a diamond rotary cuttinginstrument (group R) showed theroughest surfaces, and SEM confirmedthat the diamond rotary cutting in-strument had scratched the surfaces.The use of polishing materials (groupsPB, PU, PS) reduced the severity ofthese scratches; the significantlysmoother surfaces observed in group PScan be attributed to the use of 2 siliconcarbide rubber points, which increased

Kursoglu et al

5 Scanning electron microscope microphotograph(�1000 magnification of group GR, reglazing group).

6 Scanning electron microscope microphotograph(�1000 magnification of group GG, glazing group).

Table III. Mean and SD of color changes (DE) and differences between groups

Group DE ±SD Difference*

R 1.55 �0.30 a

PB 1.37 �0.55 a, b

PU 1.37 �0.34 a, b

PS 1.01 �0.62 b, c

GR 0.81 �0.30 c, d

GG 0.42 �0.07 d

F¼10.933

R, rotary diamond cutting instrument group; PB, polishing group Bredent; PU, polishing groupUltradent; PS, polishing group Shofu; GG, glazing group; GR, reglazing group; SD, standarddeviation.*Different letters indicate statistically significant difference between groups (P<.05).

3.000

2.500

2.000

1.500

1.000

0.500

0.000

0.000 0.500 1.000 1.500 2.000

7 Pearson correlation analysis of relationship between meansurface roughness and mean color difference.

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Kursoglu et al

polishing time and may be relateddirectly to the reduction in Ra values.The higher Ra values in group PScompared with group PU can beattributed to the use of polishing pastewith disks alone, in agreement with thefindings of previous studies.12,13 Themanufacturers’ polishing procedureswere followed, and silicon carbiderubber points was used; thus, thehigher Ra values in group PB comparedwith groups PU and PS were likely dueto product differences. SEM imagesfrom the polished groups showedvarying degrees of scratch reductionthat paralleled the Ra values.

Ahmad et al15 reported that the useof clinical polishing instruments at arotational velocity of 10 000 rpm didnot affect the flexural strength ofceramic material, but that polishing at ahigher rotational velocity weakened theceramics in spite of achieving smooth-ness. In this study, polishing systemswere used at 10 000 rpm to avoid thisweakening effect.

Measurements obtained with in-struments such as spectroradiometers,spectrophotometers, and colorimeterspermit the quantitative assessment ofcolor deviation.29-33,43 In this study, aspectrophotometer was used to obtainprecise measurements. Although severalstudies have assessed DE values, noclinically acceptable limit has been

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established.39 O’Brien49 classifies colormatching tolerance DE values as fol-lows: 0, perfect; 0.5 to 1, excellent; 1 to2, good; 2 to 3.5, clinically acceptable;and >3.5, mismatch. One study45

suggested that DE values >0.4 aredetectable by the highly trained humaneye, whereas another study47 statedthat the mean color perceptibility was2.6 DE units. In this study, a differenceof 2.6 DE units was considered thecolor perceptibility limit, according toa previous study.47 Several studies haveexamined the stainability of restorativematerials after immersion in a solu-tion.34,35,37,39,40,42,52 Many beverages(for example, tea, coffee, and cola)have been used to evaluate discolor-ation.35,36,38,42 In this study, coffee wasused because it is commonly consumedin daily life.53

Atay et al42 evaluated the effects of4 beverages on the color of feldspathicporcelain subjected to 4 surface treat-ments. The polished group showedgreater stainability compared with theglazed, overglazed, and ion-exchangegroups. The authors also stated thatthe type of solution and immersiontime affected stainability, but differ-ences among groups were not signifi-cant. In agreement with their findings,the polished groups (PB, PU, PS) in thepresent study showed greater stain-ability than did the glazed group (GG).

Another study34 evaluated thestainability of 2 composite resin resto-rations and 1 porcelain restoration af-ter exposure to 4 beverages. Among thebeverages, coffee produced the moststaining of porcelain after 1 month(DE¼1.32), but this difference wasconsidered to be visually imperceptible.The results of that study cannot becompared with those of the presentresearch because of the differences inimmersion time.

Yilmaz et al39 compared color sta-bility in polished and glazed porcelainmaterials before and after immersion inmethylene blue. They reported greatercolor stability in glazed porcelainmaterials (DE¼0.10-0.26) than in pol-ished porcelain materials (DE¼0.48-0.69), although changes in both groups

The Journal of Prosthetic Dentis

were not clinically detectable. The re-sults of that study cannot be comparedwith those of the present researchbecause different solutions were used.

Sarikaya and Güler52 investigatedstainability in 4 porcelain materialssubjected to different surface treatmentsafter immersion in coffee for 48 hours.The highest DE value (2.142) was ob-tained with Ceramco III ceramic mate-rial (DeguDent/Dentsply Intl) andsurface treatment with polishing pastealone. The lowest DE value (0.912) wasobtained with glazed Vitablocks MarkII ceramic material (Vita Zahnfabrik).Among the 4 ceramic materials, glazingyieldedDE values of 0.912 to 1.022, andpolishing produced DE values of 1.6 to1.8. Stainability was significantly andmarkedly greater in polished than inglazed specimens. Compared with thosefindings, DE values in the polishedgroups (PB, PU, PS) were lower in thepresent study, and values in group PSapproached those in group GR, whichwas reglazed. Furthermore, althoughSarikaya and Güler52 used a shorterimmersion time than in the presentstudy, they obtained higher DE valuesin glazed and polished specimens thanin the corresponding groups in thisstudy. These discrepancies can beattributed to differences in ceramics andpolishing materials.

Porosity is undesirable in ceramicmaterials and is believed to affect es-thetics and longevity.25 Grinding ex-poses the closed pores on the surfaceof the material, producing a roughsurface16 that is susceptible to discol-oration.17,39,42 Albakry et al28 foundthat the pressing of IPS Empressceramic (Ivoclar Vivadent), a heat-pressed, leucite-reinforced material,effectively eliminated pores; smaller andfewer pores were found after pressing.Thus, with respect to stainability,pressable ceramics are more advanta-geous than feldspathic ceramics.

Motro et al17 demonstrated thatRa affected the stainability of theIPS e.max Ceram (Ivoclar Vivadent)feldspathic ceramic. Although the au-thors used methods identical to thoseused in this study, they obtained

try

different Ra and DE values becauseof the differences in the ceramic mate-rial. Stainability was higher in IPS e.maxCeram specimens that had been builtup by using a layering technique thanin the materials tested in this study.This result can be explained by surfacepore exposure caused by grinding ofthe layering ceramic (IPS e.max Ceram),which increased stainability. Conversely,the low degree of discoloration in spiteof a high Ra value observed for the IPSEmpress Esthetic material in the currentstudy may be attributed to the densestructure and low porosity of thispressable ceramic material. In spite ofthese differences, the results of theglazed and reglazed groups in the cur-rent study and in Motro et al17 weresimilar, indicating that glazing sealedthe pores on the ceramic surfaces.

In the current study, Ra values, butnot DE values, differed significantlybetween groups PS (polished) and GR(reglazed). Discoloration was similarin these 2 groups because of thedense structure of heat-pressed, leucite-reinforced ceramic material. Stainabilityin both of these groups was lower thanthe color perceptibility limit of 2.6 DEunits47 and within the range of “excel-lent,” according to the O’Brien classi-fication.49 These findings indicate thatstainability can be reduced by the use ofpolishing materials that are appropriatefor the ceramic material.

In this study, a single immersiontime and staining agent were used inall tests. Different solutions and im-mersion times have variable effectson ceramic color44 and stainability.42

Further studies should be performedwith a range of solutions and immer-sion times. Also, the lack of profilom-etry measurement after the abrasionof surfaces with rotary cutting in-struments and the lack of appliedpressure values while polishing theceramic disks are limitations of thisstudy.

CONCLUSIONS

Within the limitations of this in vitrostudy, the following conclusions can be

Kursoglu et al

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drawn. Ra significantly affected thestainability of ceramics. Polishing ma-terials from Shofu Inc yielded the bestresults among the polishing agentstested. Overall, none of the disks in thepressable ceramic group showed clini-cally perceptible discoloration.

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Corresponding author:Dr Pinar KursogluYeditepe University, Faculty of DentistryBagdat Cad. No. 238 Goztepe34728 IstanbulTURKEYE-mail: pinar.kursoglu@gmail.com

Copyright ª 2014 by the Editorial Council forThe Journal of Prosthetic Dentistry.

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