RESEARCH AND EDUCATION Effect of different surface treatment methods on the surface roughness and color stability of interim prosthodontic materials Aysegül Köroglu, DDS, PhD, a Onur Sahin, DDS, PhD, b Dogu Ömür Dede, DDS, PhD, c and Burak Yilmaz, DDS, PhD d Interim crown restorations pro- vide function and comfort, adequate esthetic appearance, easier oral hygiene, pulpal pro- tection and thermal insulation, stabilization against undesired tooth movements, and preven- tion of gingival overgrowth. They may also be used for diagnostic purposes. 1-4 The materials available for fabricating interim crowns by either direct or indirect tech- niques are poly(methyl meth- acrylate) (PMMA), polyethyl methacrylate (PEMA), polyvi- nyl methacrylate (PVMA), ure- thane dimethacrylate (UDMA), bis-acryl composite resin, and composite resin. 1,2,5,6 Acrylic resins are low-cost materials that can be easily smoothed and polished; however, the exothermic polymerization re- action and polymerization shrinkage of the material pre- sent challenges. 7-9 The development of bis-acryl materials has helped to eliminate some of these problems. 9 How- ever, their higher cost and low resistance to deformation are disadvantages. 9,10 Interim restorations should be smooth, and inade- quately finished restorations may promote biofilm adherence on their surface and adjacent intraoral struc- tures. 11-14 Compared with smooth surfaces, rough a Assistant Professor, Bülent Ecevit University, Faculty of Dentistry, Department of Prosthodontics, Zonguldak, Turkey. b Assistant Professor, Bülent Ecevit University, Faculty of Dentistry, Department of Prosthodontics, Zonguldak, Turkey. c Assistant Professor, Ordu University, Faculty of Dentistry, Department of Prosthodontics, Ordu, Turkey. d Associate Professor, Division of Restorative Science and Prosthodontics, The Ohio State University, College of Dentistry, Columbus, Ohio. ABSTRACT Statement of problem. The effects of surface sealant agents on the surface roughness and color stability of interim crown materials are unknown. Purpose. The 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 methods. A 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 [DE 00 ]) were calculated. Data were statistically analyzed with 2-way ANOVA and the Tukey honest significant differences test (a=.05). Results. The Ra values of Tempofit with Biscover were significantly lower than their control group, Tab 2000 and Dentalon Plus control groups (P<.05). The highest DE 00 was calculated for Tempofit control (P<.05). The Dentalon Plus control group had significantly higher DE 00 values than the other groups, except for the Tempofit and Tab 2000 control groups.The Tab 2000 control DE 00 was significantly higher than the other groups, except for Dentalon Plus with Palaseal and Dentalon Plus with Optiglaze. Conclusions. All specimens had a surface roughness higher than the plaque accumulation threshold (0.20 mm). 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. (J Prosthet Dent 2016;115:447-455) THE JOURNAL OF PROSTHETIC DENTISTRY 447
Effect of different surface treatment methods on the surfaceroughness and color stability of interim prosthodontic
materials
Aysegül Köro�glu, DDS, PhD,a Onur Sahin, DDS, PhD,b Do�gu Ömür Dede, DDS, PhD,c and
Burak Yilmaz, DDS, PhDd
ABSTRACTStatement of problem. The effects of surface sealant agents on the surface roughness and colorstability of interim crown materials are unknown.
Purpose. The purpose of this in vitro study was to evaluate the effects of different polishingmethods on the surface roughness and color stability of 4 interim crown materials.
Material and methods. A 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 anddivided into 4 groups (n=10) according to applied surface treatment procedures: conventionalpolishing (control) and 3 surface sealant (Palaseal, Optiglaze, Biscover) coupling methods. Surfaceroughness (Ra) values were measured with a profilometer. Color parameters were measured witha spectrophotometer before and after staining in coffee. Color differences (CIEDE 2000 [DE00])were calculated. Data were statistically analyzed with 2-way ANOVA and the Tukey honestsignificant differences test (a=.05).
Results. The Ra values of Tempofit with Biscover were significantly lower than their control group,Tab 2000 and Dentalon Plus control groups (P<.05). The highest DE00 was calculated for Tempofitcontrol (P<.05). The Dentalon Plus control group had significantly higher DE00 values than the othergroups, except for the Tempofit and Tab 2000 control groups.The Tab 2000 control DE00 wassignificantly higher than the other groups, except for Dentalon Plus with Palaseal and Dentalon Pluswith Optiglaze.
Conclusions. All specimens had a surface roughness higher than the plaque accumulationthreshold (0.20 mm). Smoother surfaces were observed for Tempofit with Biscover when comparedwith theTempofit control. The color change observed with the Dentalon Plus, Tab 2000, andTempofit control groups was clinically unacceptable. Nonperceivable color changes were seen withProtemp 4 with Optiglaze, Tempofit with Optiglaze, and Tempofit with Biscover. Perceivable butclinically acceptable color changes were observed when sealants were used for all other test groupsand Protemp 4 control. (J Prosthet Dent 2016;115:447-455)
Interim crown restorations pro-vide function and comfort,adequate esthetic appearance,easier oral hygiene, pulpal pro-tection and thermal insulation,stabilization against undesiredtooth movements, and preven-tion of gingival overgrowth.They may also be used fordiagnostic purposes.1-4
The materials available forfabricating interim crowns byeither direct or indirect tech-niques are poly(methyl meth-acrylate) (PMMA), polyethylmethacrylate (PEMA), polyvi-nyl methacrylate (PVMA), ure-thane dimethacrylate (UDMA),bis-acryl composite resin, andcomposite resin.1,2,5,6 Acrylicresins are low-cost materialsthat can be easily smoothedand polished; however, theexothermic polymerization re-action and polymerizationshrinkage of the material pre-
sent challenges.7-9 The development of bis-acryl materialshas helped to eliminate some of these problems.9 How-ever, their higher cost and low resistance to deformationare disadvantages.9,10
ofessor, Bülent Ecevit University, Faculty of Dentistry, Department of Prostofessor, Bülent Ecevit University, Faculty of Dentistry, Department of Prostofessor, Ordu University, Faculty of Dentistry, Department of Prosthodonticofessor, Division of Restorative Science and Prosthodontics, The Ohio Sta
L OF PROSTHETIC DENTISTRY
Interim restorations should be smooth, and inade-quately finished restorations may promote biofilmadherence on their surface and adjacent intraoral struc-tures.11-14 Compared with smooth surfaces, rough
hodontics, Zonguldak, Turkey.hodontics, Zonguldak, Turkey.s, Ordu, Turkey.te University, College of Dentistry, Columbus, Ohio.
Clinical ImplicationClinicians may choose the Biscover sealant agentwith the Tempofit material to obtain smoother andmore color-stable interim restorations and thetested sealant agents for more color-stable interimcrowns.
448 Volume 115 Issue 4
surfaces are more inclined to plaque accumulation.12,15-19
Ra average is a commonly reported parameter forroughness.20,21 Rmax value is defined as the maximum ofthe peak-to-valley heights of the measured section.21
Recent in vivo studies have suggested that a “thresholdRa” value above 0.2 mm in surface roughness is associatedwith increased plaque accumulation and bacterial reten-tion.22-24
Color stability is an important criterion whenselecting an interim crown material.25-27 Color alterationis multifactorial and generally related to incompletepolymerization, water sorption, oral hygiene, and thesurface smoothness of the restoration.28,29 Pigmentedbeverages such as coffee and tea also promote discol-oration.26,30 Various techniques have been used to finishand polish interim materials.3,30 Conventionally, afterfinishing with burs and abrasive stones, a polish is ob-tained with water and fine pumice, polishing paste, orliquid polish that contains aluminum oxide particles.31
Recently, surface sealant agents have been introducedto minimize surface porosity and obtain smooth sur-faces.32,33 However, the long-term performance of theseagents is uncertain.3,24,34
The purpose of this study was to evaluate differentsurface treatment methods on the surface roughness andcolor stability of interim crown materials. The null hy-pothesis of this study was that the surface sealantcoupling techniques would have no effect upon thesurface roughness and color stability of interim crown
Optiglaze Og Methyl methacrylate, multifunctional acryla
BisCover LV Bc Dipentaerythritolpentaacrylate, ethanol
THE JOURNAL OF PROSTHETIC DENTISTRY
materials and that their effect would not vary dependingon the type of resin material.
MATERIAL AND METHODS
Two autopolymerized polymethyl methacrylate and 2bis-acryl composite resin-based interim crown materialswere evaluated in this study (Table 1). Forty disk-shapedspecimens (10 mm in diameter and 2 mm in thickness)were prepared for each resin material by using stainlesssteel molds. Materials were mixed according to themanufacturers’ instructions. The specimens were thendivided into 4 groups (n=10) to provide different surfacetreatments as follows: 1 conventional laboratory polish-ing (control) and 3 surface sealant agent couplingmethods. Power analysis showed that to detect a mini-mum significant difference in surface roughness of 0.774mm (standard deviation [SD]=0.24) with b=.01 type IIerror, 5% type I error, and a=.05 probability level, aminimum of 9 specimens were necessary for each groupto achieve a 95% confidence interval and 99% power.The surface-sealing agents used in this study are shownin Table 2.
All specimens were finished with a tungsten carbidebur (S274 190 060; Horico) and wet ground with asanding machine (100 rpm for 15 seconds; Phoenix Beta;Buehler Ltd.) with 400-grit silicon carbide abrasive paper(English Abrasives). Control group specimens were pol-ished with a slurry of coarse pumice (Isler Pomza; IslerDental) and water with a bristle brush on a polishinglathe (P1000; Zubler) for 90 seconds at a rate of 1500rpm. These specimens were then subjected to fine pol-ishing with a polishing paste (dental plaster [Kargips;Knauf] plus pure alcohol) and a lathe flannel wheel(Blaudent; Anka Dental) for 90 seconds.31 For the 3experimental groups, each surface-sealant agent wasapplied with a soft brush in a thin and even layer in 1direction without any air bubble formation. Twenty sec-onds after application, the specimens coated with
Bc, BisCover LV; Dnt, Dentalon Plus; PMMA, poly(methyl methacrylate); Prt, Protemp; Ps,Palaseal; Og, Optiglaze; Ra, surface roughness; Tab, Tab 2000; Tmp, Tempofit.Results of Tukey post hoc comparisons are shown as superscript letters and values havingsame superscript letters were not significantly different (P>.05).
Bc, BisCover LV; Dnt, Dentalon Plus; PMMA, poly(methyl methacrylate); Prt, Protemp; Ps,Palaseal; Og, Optiglaze; Ra, surface roughness; Tab, Tab 2000; Tmp, Tempofit.*Results of Tukey post hoc comparisons shown as superscripts and values having same letterswere not significantly different (P>.05).
1.4
1.2
1.0 * * *
*
* *
* **
*
*
*
*
* *
xM
ean
Ra, S
D (µ
m)
0.8
0.6
0.4
0.2
Group
0
Tab_CTab_PsTab_O
gTab_BcDnt_C
Dnt_Ps
Dnt_O
gDnt_Bc
Prt_CPrt_PsPrt_O
gPrt_BcTm
p_CTm
p_PsTm
p_Og
Tmp_Bc
Figure 1. Mean Ra (±SD) values of test groups. Plaque accumulationthreshold levels (Ra=0.2 mm) are indicated as the X line. *Significantdifferences from threshold of Ra according to paired sample t test(P<.05).
April 2016 449
Palaseal and Optiglaze were polymerized for 90 secondsin a light-polymerizing unit (Dentacolor XS; HeraeusKulzer GmbH), whereas the specimens coated withBisCover LV were polymerized for 30 seconds with alight-emitting diode (LED) polymerization light (EliparFreeLigth 2; 3M ESPE) at a reading of 750 mW/cm2. Eachspecimen was then ultrasonically cleaned in distilledwater (Hygosonic; Dürr Dental AG) for 10 minutes,rinsed, and dried with oil-free air. One specimen for eachgroup was examined with a scanning electron micro-scope (SEM; Nova Nano SEM 450; FEI Co). The accel-eration voltage of the cathode was set to 15 kV and aworking distance of 13.3 mm.
Ra was assessed with a contact profilometer (Perth-ometer M2; Mahr). Three measurements were made foreach specimen by moving the instrument’s diamondstylus (NHT-6) across the specimen’s surface underconstant pressure. Mean Ra values were calculated andrecorded for each specimen in mm. The profilometer’sresolution was 0.01 mm, the interval (cut-off length) was0.8 mm, the transverse length was 5.5 mm, and the stylusspeed was 1 mm/s.
Color parameters (L*, a*, b*) of each specimenwere measured with a digital spectrophotometer (VitaEasy Shade;Vita Zahnfabrik) and recorded accordingto the Commission International de I’Eclairage (CIE)Lab 3-dimensional color space system. Initial color
Köro�glu et al
measurements were repeated 3 times for each specimen,and the means were recorded as L0*, a0*, b0*. Specimenswere embedded in wax plates to cover the unpolishedsurfaces. A staining solution was prepared by dissolving7.5 g of coffee (Nescafe Classic; Nestle) in 500 mL ofboiled distilled water, and the specimens were stored inthis solution at 37�C in a dark environment to simulateintraoral conditions for 7 days. The staining solution waschanged every 2 days throughout the test.35 After thestaining procedure, the specimens were washed underwater for 5 minutes and air-spray-dried before colormeasurements were made. Data were recorded as L1*,a1*, b1*. Color change values (discoloration) of thespecimens were determined by using the CIEDE2000(DE00) color difference formula31,36:
where DL0, DC0, and DH0 are the differences in lightness,chroma, and hue for a pair of specimens in CIEDE2000and RT is the rotation factor that accounts for the
THE JOURNAL OF PROSTHETIC DENTISTRY
Figure 2. Scanning electron micrograph analysis (×1000 magnification). A, Conventionally polished (note irregular surface texture). B, Palaseal.C, Optiglaze. D, BisCover LV coupled with Tab 2000 interim crown material.
450 Volume 115 Issue 4
interaction between chroma and hue differences in theblue region. SL, SC , SH adjust the total color difference forvariations in the location of the color difference pair inthe L0, a0, b0 coordinates and the parametric factors. KL,KC and KH are the terms for the experimental conditions.In the present study, the parametric factors of theCIEDE2000 color difference formula were set to 1. Also,the perceptibility threshold was set at DE00�1.30 units,and the clinical acceptability threshold was set atDE00�2.25 units.37-39
The data were statistically analyzed, and computa-tions were performed using statistical software (SPSSversion 17.0; SPSS Inc). The Levene test of homogeneitywas used to evaluate the distribution of the variables. Ra
and DE00 results were analyzed separately with the 2-way ANOVA test to evaluate the effects of interim ma-terial type, surface treatment techniques, and their in-teractions. Mean Ra and DE00 values were then comparedwith the Tukey HSD test. A comparison of mean Ra
values with plaque accumulation threshold levels(Ra=0.2) and also of mean DE00 values with clinicallyacceptability (DE00�2.25) and perceptibility threshold
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(DE00�1.30) levels were analyzed using the paired sam-ple t test (a=.05).
RESULTS
According to the 2-way ANOVA of both the Ra and DE00results, the effects of the interim material and surfacetreatment technique were statistically significant. Theirinteraction was significant only for color stability (P<.05)(Table 3). Mean ±SD Ra and DE00 values for the interimmaterial/surface treatment technique combinations areshown in Tables 4 and 5.
The Ra values for all groups (0.309 to 0.796 mm) weresignificantly higher than the plaque accumulationthreshold level (0.20 mm), except for Tmp_Bc (P=.089;P<.05) (Fig. 1). For all groups, even though interim ma-terials coupled with a surface sealant agent had lower Ra
values than conventionally polished materials, statisti-cally significant differences were observed only betweenthe Tmp control and Tmp_Bc (P=.026). No significantdifferences were found among the other groups (P>.05).The highest Ra value was observed in the Dnt control
Köro�glu et al
Figure 3. Scanning electron micrograph analysis (×1000 magnification). A, Conventionally polished (note rougher surface). B, Palaseal. C, Optiglaze.D, BisCover LV with Dentalon Plus interim crown material.
April 2016 451
group (0.796 mm), and the lowest Ra value was deter-mined for the Tmp_Bc group (0.309 mm) (Fig. 5). SEMimages of the Tab, Dnt, Prt, and Tmp interim materialsurfaces after the surface treatments are shown inFigures 2-5.
Mean color differences (DE00) for the conventionallypolished Tab, Dnt, and Tmp interim material groupswere above the clinical acceptability threshold level(DE00>2.25). However, only the DE00 values of Dnt_C(P=.002) and Tmp_C groups were significantly differentthan the acceptability threshold level according to thepaired sample t test results (P<.001). The DE00 valuesof the Prt_Og, Tmp_Bc and Tmp_Og groups werebelow the perceptibility threshold (DE00�1.30); how-ever, according to the paired sample t test results, thedifference was statistically significant only in theTmp_Bc test group (P=.023). All other DE00 valueswere within clinically acceptable limits (1.30� DE00 �2.25), but still in the range of visual perceptibility.Although the highest DE00 was observed in the Tmp_Cgroup (3.61), the lowest was seen in the Tmp_Bc group(1.20) (Fig. 6).
Köro�glu et al
When conventionally polished groups were com-pared, the highest DE00 values were obtained for Tmp(P<.001) and the lowest for the Prt group, which wassignificantly lower than those of Tmp (P<.001) and Dnt(P<.001). When the difference between the DE00 valuesof the control group and surface sealant agent groupswere compared, the greatest and most significant dif-ferences were observed for the Tmp, Dnt, and Tab groups(P<.05). No statistically significant difference was foundamong the surface sealant agent groups for all interimmaterials (P>.05).
DISCUSSION
The null hypothesis was rejected. Although the results ofthe surface treatment techniques and interim materialtype were significant on both surface roughness andcolor stability, their interaction had no effect on surfaceroughness. In the present study, Ra values ranged be-tween 0.309 and 0.796 mm. Although these values wereabove the threshold Ra of 0.2 mm that Bollen et al23
indicated, they were below the 10-mm limit of clinical
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Figure 4. Scanning electron micrograph analysis (×1000 magnification). A, Conventionally polished (note rougher surface). B, Palaseal. C, Optiglaze.D, BisCover LV with Protemp 4 interim crown material.
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undetectability identified by Kaplan et al.17 This situationshows that the single-phase surface treatment pro-cedures used in the current study could be suitable forshort-term interim restorations as previously stated byBorchers et al.24 Similar to the study findings of Ayuso-Montero et al,11 conventionally polished PMMA resinsshowed higher surface roughness values compared withthose of bis-acryl composite resins. In contrast, severalstudies8,14,24 noted the smoother surfaces of methacrylateresins compared with those of bis-acryl composite resinsand attributed this to the homogenous composition ofthe acrylic resin materials and the heterogenouscomposition of the composite resin materials. Regardlessof the surface polishing technique used, the inherentchemistry of the material, the initiator, the resin matrixcomposition, and the existence of filler particles, as wellas their size and distribution, affect polishability andsmoothness.8,19,24
Sealant agents are recommended for improving theoptimal properties and especially the surface smooth-ness of restorations by filling by capillary actionthe microfissures and microdefects that form after the
THE JOURNAL OF PROSTHETIC DENTISTRY
finishing/polishing procedures. However, the sealantagents can lead to problems such as low resistance toabrasion, weak retention to the underlying material, andpoor surface quality resulting from uneven spreading thatmay depend on high viscosity.24,32,33 In the presentstudy, even though not statistically significant, the use ofsurface-sealant agents resulted in lower Ra values for allinterim resin material groups compared with the con-ventional polishing method. For the Tab and Dnt resingroups, this may have occurred because the sealantagents decreased the surface roughness by increasing themolecular weight of the methacrylate components, aspreviously stated by Borchers et al.24
The preparation method of the interim crown mate-rial, automixed or hand-mixed, affects surface porositiesand defects. Hence, the surface roughness, water sorp-tion, and accordingly the color stability may be affectedby trapped air or unreacted monomer.40 SEM analysis inthe present study revealed greater porosity and air bub-bles on the conventionally polished Dnt specimen sur-face, which was prepared by hand mixing (Fig. 3). Thisimage was similar to the second type of pore formation
Köro�glu et al
Figure 5. Scanning electron micrograph analysis (×1000 magnification). A, conventionally polished (note rougher surface). B, Palaseal. C, Optiglaze.D, BisCover LV with Tempofit interim crown material.
April 2016 453
described by Kuhar and Funduk.31 Air may have beenincorporated at a later stage of mixing, such as after thethe monomer had completely perfused the acrylic resinpowder. SEM analysis showed that for all the resingroups, the application of the surface sealant agentreduced the surface roughness. The specimens whichrepresented the highest and the lowest Ra values hadSEM images consistent with the surface roughnessmeasurement results.
In the current study, coffee was used because of itshigh staining potential. Discoloration with coffee mayhave occurred through the absorption and adsorption ofpolar colorants into/onto the organic phase of resinmaterials.6,26,28 Depending on the composition of theinterim material and the type and degree of polymeri-zation, staining may vary. The chemical properties ofmaterials such as the size and distribution of the poly-methyl methacrylate particles, stability of pigments, po-larity of monomers, effectiveness of the initiator system,filler content, and cross-linking amount are importantfactors in the degree of polymerization, water sorption,and color stability. Most bis-acryl polymers are more
Köro�glu et al
polar than PMMA because they have a greater affinity towater and other polar liquids. In the present study, thedifferences regarding filler content, amount of cross-linking, and hence water sorption were the unknownparameters that may have affected the color results of thePMMA and bis-acryl resin material test groups. Also, thepresence of porosity and more dense filler particle con-tent seen in the SEM images of the Dnt and Tmp controlgroups may have caused higher DE00 values. Severalstudies have reported that larger filler particle size andhence the decreased amount of filler content results ingreater Ra values. Accordingly, an increase in the size offiller particles would result in surface irregularities,causing a difference in color.29,33 The difference betweenthe DE00 values of the Prt and Tmp control groups can beattributed to the variation in the amount, type, and sizeof filler particles and may be responsible for the differ-ences observed in the SEM images (Figs. 3, 4). Also, earlydiscoloration of materials is known to be associated withfinishing, polishing and, coating procedures and there-fore with surface roughness.7,8,27,33 For all groups in thepresent study, the application of surface sealant reduced
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5.00
4.00
*
ºº º º
º
º
º
ºº º
º º
º
º
º*
** *
*
X
Y
Mea
n ΔE
00, S
D
3.00
2.00
1.00
Group
0
Tab_CTab_PsTab_O
gTab_BcDnt_C
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Dnt_O
gDnt_Bc
Prt_CPrt_PsPrt_O
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p_CTm
p_PsTm
p_Og
Tmp_Bc
Figure 6. Mean (±SD) DE00 values of test groups. Perceptibility thresholdof color differences (DE00=1.30) indicated as X line values andacceptability threshold level (DE00=2.25) are indicated as Y line values.*Significant differences from perceptibility; ºacceptability threshold ofDE00 according to paired sample t test (P<.05).
454 Volume 115 Issue 4
the surface roughness and color difference comparedwith the control groups. The greatest color change valueswere obtained in the conventionally polished specimensfor all resin groups. Similar to the study findings of Dorayet al,3 the application of surface sealant on both bis-acrylresin groups generally resulted in better DE00 by reducingthe values below the perceptible threshold (in Prt_Ogand Tmp_Og groups) (DE00�1.30). The use of the sealantagents tested in the current study led to similar values forcolor differences for each resin group.
This in vitro study has limitations. The Vita EasyShade has a limited color library of LAB values, and theseresults should be corroborated with advanced colormeasuring instruments. Occlusal contacts, nutritionalhabits, tooth brushing, mouth rinsing, saliva, andopposing restorations should be considered in futureinvestigations. Also, further research is needed to eval-uate the long-term performance of the sealant agents oncandida or bacterial adhesion, wear resistance, and op-tical properties compared with different laboratory andchairside polishing techniques.
CONCLUSIONS
Within the limitations of this study, the following con-clusions were drawn:
1. All groups had a surface roughness higher than theplaque accumulation threshold (0.20 mm).
2. The use of the Biscover LV surface sealant agent onTempofit significantly decreased the surface rough-ness compared with the conventionally polishedTempofit specimens.
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3. Conventionally polished test specimens (except Prtgroup) exhibited a clinically unacceptable colorchange after staining (DE00>2.25).
4. For all interim resin groups, the application of sur-face sealant improved color stability and providedclinically acceptable color changes after staining.
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21. Lou MS, Chen JC, Li CM. Surface roughness prediction technique for CNCend-milling. Journal of Industrial Technology 1998;15:1-6.
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34. Lee YK, Lu H, Powers JM. Effect of surface sealent and stainingon the fluorescence of resin composites. J Prosthet Dent 2005;93:260-6.
35. Samra APB, Pereia SK, Delgado LC, Borges CP. Color stability evaluation ofaesthetic restorative materials. Braz Oral Res 2008;22:205-10.
36. Lee Y-K. Comparison of CIELAB DE* and CIEDE2000 color-differences afterpolymerization and thermocycling of resin composites. Dent Mater 2005;21:678-82.
37. Ghinea R, Perez MM, Herrera LJ, Rivas MJ, Yebra A, Paravina RD. Colordifference thresholds in dental ceramics. J Dent 2010;38:57-64.
38. Sharma G, Wu W, Dalal EN. The CIEDE2000 color-difference formula:implementation notes, supplementary test data, and mathematical observa-tions. Color Res Appl 2005;30:21-30.
39. Kürklü D, Azer SS, Yilmaz B, Johnston WM. Porcelain thickness and cementshade effects on the colour and translucency of porcelain veneering materials.J Dent 2013;41:1043-50.
40. Nomoto R, McCabe JF. Effect of mixing methods on the compressive strengthof glass ionomer cements. J Dent 2001;29:205-10.
Corresponding author:Dr Burak YilmazOhio State University College of DentistryDivision of Restorative Sciences and Prosthodontics305 W 12th AvenueColumbus, Ohio 43210Email: [email protected]
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