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Effect of polishing systems on stain susceptibility and surface roughness of nanocomposite resin material
Effect of polishing systems on stain susceptibility and surface roughness of nanocomposite resin material Haifa M. Barakah, MDSa and Nadia M. Taher, MDSb College of Dentistry, King Saud University, Riyadh, Saudi Arabia Statement of problem. Different polishing systems vary in their effect on reducing surface roughness and stain susceptibility of dental composite resin materials. Purpose. The purpose of this study was to compare the effect of 3 polishing systems on the stain susceptibility and surface roughness of 2 nanocomposite resins and a microhybrid composite resin. Material and methods. Forty-five disks (2 10 mm) each were fabricated of 2 nanocomposite resins (Filtek Supreme XT and Tetric EvoCeram) and 1 microhybrid composite resin (Z250). Both sides of the disks were wet finished, and 1 side was polished with PoGo, Astropol, or Hi-Shine (n¼5). Unpolished surfaces served as controls. The average roughness (Ra, mm) was measured with a profilometer, and the baseline color was recorded with a spectrophotometer. All specimens were incubated while soaking in a staining solution of coffee, green tea, and berry juice for 3 weeks. The color was recorded again, and the data were analyzed with 2-way ANOVA at a¼.05 and Tukey multiple comparison tests. Results. All polishing systems improved the staining resistance of Filtek Supreme XT and Z250 but did not affect that of Tetric EvoCeram. The surface color of Filtek Supreme XT was changed significantly and was the smoothest after polishing with PoGo, whereas Hi-Shine produced significantly rougher surfaces but with the lowest color change. Hi-Shine produced the highest color change in Z250. The surface roughness did not differ significantly between the other polishing systems. Tetric EvoCeram showed no significant differences in color change or surface roughness. Conclusions. Staining susceptibility and surface roughness depend mainly on material composition and on the polishing procedures. Polishing improves the staining resistance of composite resins. Nanocomposite resins did not exhibit better staining resistance or surface roughness than microhybrid composite resin. (J Prosthet Dent 2014;-:---)
Clinical Implications Polishing is recommended to improve the staining resistance of Filtek Supreme XT and Z250. Of the materials tested, Tetric EvoCeram had the greatest stain resistance with or without polishing.
Most recent restorative materials have been introduced to the dental profession to meet demands for better esthetics. Color matching and longlasting color stability of the material are 2 major factors that influence the failure or success of an esthetic restoration. Resin-based tooth-colored materials often become discolored because of intrinsic factors, including
the choice of material, the properties of the matrix, and the interface between the matrix and the fillers. These factors may directly affect color stability.1-7 Additionally, extrinsic factors resulting from the contamination of these materials with exogenous sources such as food, drink, and tobacco can cause various degrees of discoloration.3,6,8 Both coffee and cola cause significant
color changes in composite resins after 7 days of immersion.9,10 The surface texture of a toothcolored restoration influences plaque accumulation, discoloration, wear, and the esthetic appearance of the restoration.11 Therefore, proper finishing and polishing are critical procedures that enhance both the esthetics and the longevity of the restored teeth.12,13
Supported by the College of Dentistry Research Center and Deanship of Scientific Research at King Saud University, Riyadh, Saudi Arabia (research project NF 2138). a
Lecturer, Department of Restorative Dental Sciences. Professor, Consultant, Department of Restorative Dental Sciences.
b
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Volume Various polishing techniques have been used with different types of composite resin to produce a smooth surface.13-16 Different polishing protocols have been used over the years,17-19 ranging from multiple-step systems using fine and superfine diamond rotary cutting instruments, aluminum oxide abrasive disks such as Sof-Lex disks (3M ESPE), diamond- and silicon-impregnated soft rubber cups and disks such as Jiffy (Ultradent), Astropol (Ivoclar Vivadent), and OptiShine (Kerr Corp), to 1-step polishing systems20 containing diamond-impregnated cups such as PoGo (3M ESPE), aluminum and silicon oxide disks such as One Gloss (Shofu Inc), and silicon carbide brushes such as OptraPol (Ivoclar Vivadent) and ComposiPro one-step brush (Brasseler). Manufacturers purport that the 1-step polishing systems can be used as single instruments for both finishing and polishing procedures. Different surface finishing and polishing treatments may affect stain resistance by altering the surface roughness of resins.21-23 The most significant factors influencing the stain resistance of dental composite resin, including nanocomposite resin and microfilled and microhybrid composite resins, have been previously investigated.23 Coffee significantly influenced the discoloration of the dental
Table I.
composite resins tested, and discoloration increased as surface roughness increased, except in the case of microfilled composite resin.23 The authors concluded that dental composite resin restorations should be polished to achieve as smooth a finish as possible to increase stain resistance.24 They compared the susceptibility to staining of 3 types of composite resin surfaces (Clearfil Photo, SureFil, and Filtek P60) after polishing with 2 types of 1-step polishing systems (PoGo and One Gloss) and found that PoGo produced surfaces that were less susceptible to staining than those polished with One Gloss.24 Hybrid composite resins are characterized by favorable physical properties. In contrast, microfilled composite resins demonstrate superior esthetic qualities, but, because of their compromised mechanical properties, their application is restricted to non-stressbearing areas.25,26 With the introduction of nanotechnology, a new class of dental composite resin has been developed in recent years.27 Nanoparticle composite resins are purported to combine the mechanical strength of hybrid composite resin and the superior esthetic properties of microfilled composite resin.25 Previous studies have found that nanofilled and minifilled composite resin present a surface
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roughness comparable to a microfilled composite resin, independent of the polishing system used.18,28 In addition, composite resins based on nanofilled and microfilled technology gave the smoothest surfaces after polishing.29 The purpose of this study was to investigate the effect of 3 polishing systems on the stain susceptibility and surface roughness of 2 nanocomposite resins and a microhybrid composite resin. The null hypothesis was that different polishing systems would not affect the surface roughness and stain susceptibility of nanocomposite resins and microhybrid composite resins.
MATERIAL AND METHODS Three different composite resins were selected for this study: 2 types of nanocomposite resins, nanofilled composite (Filtek Supreme XT; 3M ESPE) and nanohybrid composite resins (Tetric EvoCeram; Ivoclar Vivadent), and 1 microhybrid composite resin (Filtek Z250; 3M ESPE) (Table I). The materials tested were prepared in the form of 45 disks (2 mm in height and 10 mm in diameter) by using a circular polytetrafluoroethylene mold (n¼15), which was placed on a transparent matrix strip supported by a glass slide and overfilled with composite resin. The top of the Teflon mold was then
Types of composite resins and manufacturer information
Composite Resin Filtek Supreme XT (3M ESPE)
Code Shade Type of Filler
Composition
FXT
A2
Tetric EvoCeram TEC (Ivoclar Vivadent)
A2
Nanohybrid (Lot L10973)
Matrix: UDMA, additives, catalysts, stabilizers, and pigments Filler: Barium glass, ytterbium trifluoride, mixed oxide, and prepolymers Particle size of the inorganic fillers between 40 nm and 3000 nm with a mean particle size of 550 nm.
A2
Microhybrid (Lot 20080813)
Matrix: BisGMA, UDMA, and BisEMA Filler: oxide, zircon/silica (0.01-3.5mm)
Filtek Z250 (3M ESPE)
Z
Nanofilled Matrix: BisGMA, TEGDMA, UDMA, and BisEMA (Lot 20070829) Filler: nonagglomerated nanosilica filler 20 nm, agglomerated zirconia/silica nanocluster 0.6-1.4 mm with primary particle size of 5-20 nm
Filler Content by Volume/by Weight (%) 59.5/78.5
54/75.5
61/78
BisGMA, bisphenol A-glycidyl methacrylate; BisEMA, ethoxylated bisphenol A-glycol dimethacrylate; TEGDMA, triethyleneglycol dimethacrylate; UDMA, urethane dimethacrylate.
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covered by another matrix strip and glass slide. Both the top and bottom surfaces of the disks were polymerized through the top of the glass slide with a high intensity source of blue light (400500 nm, Halogen Curing Light; Elipar 2500; 3M ESPE, M5560, serial 3021090). According to the manufacturer’s instructions for all the tested materials, they were polymerized for 20 seconds on one side (for 2 mm thickness) and then exposed to light for another 20 seconds on the other side to assure polymerization. The specimens were removed from their molds and immersed in distilled water at 37 C for 24 hours. Both the top and bottom surfaces of all specimens were subjected to wet finishing with 600-grit silicon carbide abrasive paper on a rotary polisher (Automata grinding and polishing unit, Jean Wirtz, serial 8.022869) for 30 seconds. Five specimens (n¼5) from each composite resin (n¼15) were assigned to receive polishing with 1 of the 3 polishing systems used in the study (Table II). Manufacturers’ instructions were followed during the polishing procedures. One side of each specimen was polished and marked with a 1-mm indentation. The other side was not polished and acted as a control. After polishing, each group of specimens was washed, then placed in individual vials
Table II.
containing 20 mL of distilled water and kept immersed for 24 hours at 37 C. All specimens were then subjected to surface roughness testing with a surface profilometer (Surtronic 10 Ra, Rank Taylor Hobson Ltd). Surface roughness (Ra) was recorded from 3 different positions selected on the top and bottom of each specimen. These points were located at equal distances from each other and from the disk periphery and then marked and numbered on the periphery of the specimen so the measurements were made at the same locations. The cutoff value for surface roughness was 0.8 mm, and the traversing distance of the stylus was 5.0 mm. The radius of the tracing diamond tip was 0.5 mm, the measuring force was 10 mN, and the speed was 2 mm/second. The machine was calibrated after every 5 specimens to assure reliable readings. The baseline color measurements, made using the CIE L*a*b* color space of the International Commission on Illumination (CIE), were recorded at another 3 points and marked on the top and bottom of the specimens in areas different from the points selected for surface roughness. The reason was that during the measurement of surface roughness the stylus head might cause minor scratches, which may take up more stain, invalidating the poststaining color measurement.
The color was measured by using a Color Eye 7000A Spectrophotometer (GretagMacbeth). After making baseline measurements, the specimens of each group were immersed in a mixture comprising equal amounts of 3 staining solutions (coffee, green tea, and berry juice) (Table III). The disks were placed vertically in plastic holders and were suspended in the solution. They were then incubated in the dark at 37 C for a total of 3 weeks. The staining solution was replaced with fresh solution every 24 hours during the storage period. Color was recorded for both surfaces of each disk at the end of the 3 weeks of staining. Before color measurement, the specimens were rinsed with distilled water for 1 minute and dried with an air spray.24 The baseline measurement served as the control for each specimen, which enabled the calculation of any color change. The following CIE formula was used to determine the total color difference, DE30: h i1=2 DE ¼ ðDL Þ2 þ ðDa Þ2 þ ðDb Þ2 ; where DL* ¼ (L*1 L*0), Da* ¼ (a*1 a*0), and Db* ¼ (b*1 b*0). Zero represents the baseline reading, whereas 1 represents the color reading after staining. To determine whether statistical differences existed among the groups, a
Polishing systems used and protocols
Polishing Systems
Lot No.
Composition
PoGo** (one step) Dentsply/Caulk
060723
Polymerized UDMA resin, fine diamond powder, and silicon oxide.
Step 1: light intermittent pressure at moderate speed for 1 minute, rinse, and dry Step 2: lightest pressure for 30 seconds, rinse, and dry.
Astropol* (multiple steps) Ivoclar Vivadent
LL0767
Silicon carbide, aluminum oxide, titanium oxide, and iron oxide. Astropol HP additionally contains diamond dust.
Step 1: polishing with Astropol P (green) will result in a very delicate surface finish. Step 2: polishing with microfine Astropol HP to get result in a high gloss. Speed: 7500-10 000 rpm with moderate pressure in conjunction with water.
Hi-Shine* (multiple steps) Polydentia SA
16070806
Synthetic rubber with polishing grains in various grits of the following: aluminum oxide, silicon carbide, and diamond powder.
Step 1: prepolish (pink) Step 2: polish (yellow) Maximum speed of 10 000 rpm
UDMA, urethane dimethacrylate. *Changed after single use. **Changed after two uses.
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Table III.
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Materials used to prepare staining mixture
Material
Brand Name
Preparation
Manufacturer
Coffee
Nescafé (classic)
15 g of coffee poured in 500 mL of boiled distilled water.
Nestlé España SA
Green tea
Lipton
5 tea bags were added to 500 mL of boiled distilled water.
Unilever Gulf FZE
Mixed berry juice
Almarai
51% juice to 49% water.
Almarai Co
Results of Tukey test comparing color change (DE*) and surface roughness (Ra) of composite resins tested between the polished and control surfaces (n¼15)
Table IV.
Composite Resins
Polishing System
Side
DE Mean (SD)
P
Ra Mean (SD)
P
Filtek Supreme XT
PoGo
Treatment
4.57 (2.14)
.20
0.21 (0.06)*
<.001*
Control
5.94 (3.40)
Astropol Hi-Shine
Tetric EvoCeram
Z250
PoGo
Treatment
4.91 (2.29)*
Control
7.14 (3.48)*
Treatment
2.74 (0.53)*
Control
4.88 (0.65)*
Treatment
2.67 (1.24)
Control
2.57 (0.82)
Astropol
Treatment
2.19 (1.38)
Control
2.16 (0.26)
Hi-Shine
Treatment
3.20 (0.66)
Control
3.23 (0.87)
PoGo
Treatment
2.68 (0.62)*
Control
3.26 (0.75)*
Astropol
Treatment
2.62 (0.52)*
Control
3.76 (1.15)*
Hi-Shine
Treatment
3.58 (0.96)*
Control
2.75 (0.66)*
0.30 (0.09)* .04*
0.25 (0.09)
.82
0.24 (0.06) <.001*
0.28 (0.07)
0.78
0.29 (0.05) .79
0.31 (0.10)
1.00
0.31 (0.08) .93
0.33 (0.10)*
.91
0.35 (0.09)*
<.001*
0.22 (0.04)* <.001*
0.26 (0.06)* .02*
0.28 (0.06)*
<.001*
0.33 (0.08)* <.001*
0.28 (0.05)
.48
0.29 (0.04) .01*
0.28 (0.06)
.78
0.28 (0.06)
SD, standard deviation. *Indicates statistically significant difference compared with other DE mean values (P<.05).
power analysis was performed to determine the number of specimens required in each test group. At a¼.05 and from similar previous studies, the standard deviation (SD) was determined as SD¼0.35 with a maximum mean difference of 1, and the power taken was .9. The sample size within each level was determined as 5 observations, with a total of 45 observations. The average surface roughness (Ra, mm) and the color readings were analyzed with statistical software (SPSS, version 16). Two-way ANOVA and the Tukey multiple comparison test
(a¼.05) were analysis.
used
for
statistical
RESULTS Color stability The Tukey multiple comparison test found that Filtek Supreme XT specimens underwent a significantly greater color change in their mean value (DE*¼4.081) at P<.05 compared with Tetric EvoCeram (DE¼2.691) and Z250 (DE¼2.966) (Table IV). No significant difference between Tetric EvoCeram and Z250 (see Table IV) was observed.
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The Filtek Supreme XT specimens that were polished with Hi-Shine recorded the lowest color change (DE¼2.746) (P<.05). No significant difference in color change values were recorded between specimens polished with Astropol (DE¼4.917) and those polished with PoGo (DE¼4.579; see Table IV). When Z250 was polished with Hi-Shine, it showed the greatest color change of 3.584, which was statistically significant (P<.05). Meanwhile, no significant difference was observed between the PoGo (DE¼2.682) and Astropol (DE¼2.629) polishing systems (see Table IV). No
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significant differences were noted in the mean color values obtained for Tetric EvoCeram specimens among the specimens polished with PoGo, Astropol, or Hi-Shine (see Table IV).
Effect of polishing systems on color stability of composite resins Comparing the color change of the polished surfaces with their respective unpolished surfaces (controls), the results showed that for Filtek Supreme XT, all of the polishing systems tested decreased stainability. A significant decrease was noted in the color change values of Filtek Supreme XT specimens when polished with Astropol (P<.05) and Hi-Shine (P<.05) (see Table IV). However, for Z250, Hi-Shine had a significant negative effect on its stainability. Hi-Shine increased the color change values (P<.05), whereas PoGo (P<.05) and Astropol (P<.05) decreased the staining effect (see Table IV). No significant changes were observed in the color of Tetric EvoCeram specimens when polished with the different polishing systems (see Table IV).
Surface roughness Tetric EvoCeram had significantly greater surface roughness (Ra¼0.333) (P<.05) than the mean Ra values of Filtek Z250 (Ra¼0.280) and Filtek Supreme XT (Ra¼0.251), as shown in Table IV. When Filtek Supreme XT was polished with HiShine, its surface roughness (Ra) was not significantly increased (Ra¼0.286) (P¼.054) and was greater than that of PoGo (Ra¼0.213) and that of Astropol (Ra¼0.253). Also no significant differences were noted among the different polishing techniques for Tetric EvoCeram or Z250 specimens (see Table IV).
Effect of polishing systems on surface roughness of composite resins Comparing the surface roughness of the polished surfaces with their respective unpolished surfaces (controls), the results showed that polishing decreased
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5 the surface roughness of Filtek Supreme XT and Z250. However, for Tetric EvoCeram, the different polishing systems did not affect its surface roughness, or even increased the Ra values (see Table IV). PoGo produced significantly smoother surfaces (Ra¼0.213) on Filtek Supreme XT specimens compared with the control surfaces (Ra¼0.300) (P<.05) (see Table IV). The same trend was observed for Z250, with polishing with PoGo producing a smoother surface (Ra polished¼0.280, Ra control¼0.333); however, these values were not significantly different (P>.05) (see Table IV). For Tetric EvoCeram, PoGo had no significant effect on its surface roughness, although Astropol (Ra¼0.333) and Hi-Shine (Ra¼0.353) both produced significantly greater surface roughness (Ra¼0.227, Ra¼0.260) than the control surfaces (P<.05) (see Table IV).
DISCUSSION The results of this study showed that the null hypothesis, which stated that different polishing systems would not affect the stain susceptibility and surface roughness of nanocomposite and microhybrid composite resins, should be rejected. Evidence exists that finishing and polishing procedures may influence the surface quality of composite resin and can therefore be related to the staining resistance of resin-based materials.23 In the present study, Filtek Supreme XT was found to exhibit the highest color change after staining (see Table IV), although it presented the smoothest surfaces compared with Tetric EvoCeram and Z250, regardless of the polishing technique used (see Table IV). It seems likely therefore that the color change of Filtek Supreme XT can be attributed to some intrinsic factors, whereby its color stability is directly related to the resin phase of the composite resin.3 The other possible factor is the porosity of the aggregated filler particles.5 Urethane dimethacrylate (UDMA) has been reported to be more stain
resistant than bisphenol A-glycidyl methacrylate (BisGMA) or triethyleneglycol dimethacrylate (TEGDMA).6 The discoloration of Filtek Supreme XT in the present study may depend on the reported hydrophilicity of the resin matrix in the presence of TEGDMA.5 Tetric EvoCeram was the least stained composite resin among the materials tested (see Table IV). This might be due to the omission of TEGDMA from its composition. Z250 showed a color change comparable with that of Tetric EvoCeram (see Table IV) since UDMA and ethoxylated bisphenol A-glycol dimethacrylate (bisEMA) have replaced TEGDMA in this composite resin.7 The low susceptibility to staining of both materials is probably related to the low water absorption rate of the hydrophobic resins.4 PoGo produced the smoothest surfaces on both Filtek Supreme XT and Tetric EvoCeram when compared with the other polishing systems used in the study (see Table IV). This finding is in agreement with that of several previous studies18,19,31 that reported that PoGo produced the highest gloss when used with different nanofilled composite resin. The superior effectiveness of PoGo as found in the present study could be related to its containing fine diamond abrasives.18,19,31 Tjan and Chan31 reported that for a finishing and polishing system to be effective, the abrasive particles must be relatively harder than the fillers. Otherwise, the polishing agent will only remove the soft resin matrix and leave the filler particles protruding from the surface. In the present study, PoGo produced the smoothest surfaces, but these did not prove to be the most color resistant (see Table IV), a finding in agreement with those of Türkün and Türkün20 and of Reis et al.7 These researchers also found that the smoothest surfaces were not necessarily the most stain resistant. For Filtek Supreme XT, Hi-Shine produced the roughest surfaces (Ra¼0.286 mm), but these exhibited the lowest discoloration (DE¼2.746; see Table IV). In contrast, the PoGo (Ra¼0.213 mm) and Astropol
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Volume (Ra¼0.253 mm) systems both produced smooth surfaces. However, they exhibited high mean color change values (DE¼4.579 and 4.917; see Table IV). These results appear to support the hypothesis that discoloration is most probably not dependent on extrinsic factors such as surface roughness alone. A strained surface of Filtek Supreme XT caused by the polishing procedure is more susceptible to staining.2 Astropol and PoGo might induce strain in the surfaces of the composite resin during the polishing process. As the strain increases the activity of atoms on the surface, it facilitates the accumulation of dye. Straining of the molecular arrangement of the resin matrix may detach the filler particles from the heat-softened resin.2 Generally, when comparing the surface roughness of the nano- and microhybrid composite resins tested in the study, it was noticed that although Tetric EvoCeram is a nanofilled composite resin, it produced significantly rougher surfaces than Filtek Supreme XT (nanofilled composite resin). Moreover, it produced significantly rougher surfaces than Z250, which is considered a microhybrid type (see Table IV). Meanwhile, comparable surface roughness values were recorded between Filtek Supreme XT and Z250 (see Table IV). The composition of the composite resin may have played an important role in this regard. Filtek Supreme XT demonstrates superior polishability over Tetric EvoCeram,19 which is in agreement with the current research. Filtek Supreme XT contains both nanofillers made of silica and nanoclusters made of silica/zirconia. Nanocluster filler particles consist of loosely bound agglomerates of nanosized filler particles. Ergücü and Türkün19 found that during the polishing of Filtek Supreme XT, the nanoparticles that form these clusters can be worn away, and the whole cluster particles do not need to be plucked from the resin itself. Moreover, by using scanning electron microscope images of Filtek Supreme XT, they found that no particles were dislodged. Ultimately, the
polished surfaces have smaller defects and better polish retention. In contrast, the same researchers also reported that composite resin containing glass fillers such as Tetric EvoCeram showed significantly rougher surfaces than Filtek Supreme XT when both materials were polished with the same polishing system. In the present study, Filtek Supreme XT and Z250, whose filler systems have a similar composition regardless of the filler sizes, presented comparable surface roughness, whereas Tetric EvoCeram, which is composed of different particles (glass), presented a rougher surface. For that reason, this study may relate surface roughness to the hardness of the filler system with polishing abrasives capable of abrading evenly to produce smoother surfaces.
CONCLUSIONS Within the limitations of this in vitro study, the following conclusions were drawn. Stain susceptibility and surface roughness depended mainly on the composition of the material and the polishing procedure. Among the materials tested, Filtek Supreme XT presented the smoothest surfaces and was considered the most stain-susceptible material. The best staining resistance of Filtek Supreme XT was obtained when polished with Hi-Shine. PoGo and Astropol produced the best staining resistance of Z250, whereas HiShine was the least effective. If Tetric EvoCeram is intended to be polished after finishing, Astropol or Hi-Shine should not be used, because they produced rougher surfaces than those obtained by finishing alone.
REFERENCES 1. Um CM, Ruyter IE. Staining of resin-based veneering materials with coffee and tea. Quintessence Int 1991;22:377-86. 2. Van Noort R, Davis LG. The surface finish of composite resin restorative materials. Br Dent J 1984;157:360-4. 3. Villalta P, Lu H, Okte Z, Garcia-Godoy F, Powers JM. Effects of staining and bleaching on color change of dental composite resins. J Prosthet Dent 2006;95:137-42.
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4. Douglas WH, Craig RG. Resistance to extrinsic strains by hydrophobic composite resin systems. J Dent Res 1982;61:41-3. 5. Iazzetti G, Burgess JO, Gardiner D, Ripps A. Color stability of fluoride-containing restorative materials. Oper Dent 2000;25: 520-5. 6. Khokhar ZA, Razzoog ME, Yaman P. Color stability of restorative resins. Quintessence Int 1991;22:733-7. 7. Reis AF, Giannini M, Lovadino JR, Ambrosano GM. Effects of various finishing systems on the surface roughness and staining susceptibility of packable composite resins. Dent Mater 2003;19:12-8. 8. Satou N, Khan AM, Matsumae I, Satou J, Shintani H. In vitro color change of composite-based resins. Dent Mater 1989;5: 381-7. 9. Patel SB, Gordan VV, Barrett AA, Shen C. The effect of surface finishing and storage solutions on the color stability of resin-based composites. J Am Dent Assoc 2004;135: 587-94; quiz 654. 10. Mohan M, Shey Z, Vaidyanathan J, Vaidyanathan TK, Munisamy S, Janal M. Color changes of restorative materials exposed in vitro to cola beverage. Pediatr Dent 2008;30:309-16. 11. Morgan M. Finishing and polishing procedures of direct posterior resin restorations. Pract Proced Aesthet Dent 2004;16:211-7; quiz 218. 12. Goldstein RE. Finishing of composites and laminates. Dent Clin North Am 1989;33: 305-18, 210-9. 13. Jefferies SR. The art and science of abrasive finishing and polishing in restorative dentistry. Dent Clin North Am 1998;42: 613-27. 14. Chung KH, Greener EH. Correlation between degree of conversion, filler concentration and mechanical properties of posterior composite resins. J Oral Rehabil 1990;17: 487-94. 15. Roeder LB, Tate WH, Powers JM. Effect of finishing and polishing procedures on the surface roughness of packable composites. Oper Dent 2000;25:534-43. 16. Reis AF, Giannini M, Lovadino JR, Santos Dias CT. The effect of six polishing systems on roughness of two packable composite resins. Am J Dent 2002;15:193-7. 17. St-Georges AJ, Bolla M, Fortin D, Muller-Bolla M, Thompson JY, Stamatiades PJ. Surface finish produced on three resin composites by new polishing systems. Oper Dent 2005;30:593-7. 18. Da Costa J, Ferracane J, Paravina RD, Mazur RF, Roeder L. The effect of different polishing systems on surface roughness and gloss of various resin composites. J Esthet Restor Dent 2007;19:214-24; discussion 225-6. 19. Ergücü Z, Türkün LS. Surface roughness of novel resin composites polished with onestep systems. Oper Dent 2007;32:185-92. 20. Türkün LS, Türkün M. The effect of one-step polishing system on the surface roughness of three esthetic resin composite materials. Oper Dent 2004;29:203-11.
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21. Patel SB, Gordan VV, Barrett AA, Shen C. The effect of surface finishing and storage solutions on the color stability of resin-based composites. J Am Dent Assoc 2004;135: 587-94; quiz 654. 22. Paravina RD, Boeder L, Lu H, Vogel K, Powers JM. Effect of finishing and polishing procedures on surface roughness, gloss and color of resin-based composites. Am J Dent 2004;17:262-6. 23. Lu H, Roeder LB, Lei L, Powers JM. Effect of surface roughness on stain resistance of dental resin composites. J Esthetic Restor Dent 2005;17:102-8; discussion 109. 24. Türkün LS, Leblebicioglu EA. Stain retention and surface characteristics of posterior composites polished by one-step systems. Am J Dent 2006;19:343-7.
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7 25. Walker R, Burgess JO. Comparing resinbased composites. Compend Contin Educ Dent 2004;25:424, 426, 428 passim. 26. Lu H, Lee YK, Oguri M, Powers JM. Properties of a dental resin composite with spherical inorganic filler. Oper Dent 2006;31:734-40. 27. Roberson TM, Helmann HO, Swift EJ Jr. Sturdevant’s art and science of operative dentistry. 4th ed.St Louis: Mosby; 2001. p. 190-6. 28. Ryba TM, Dunn WJ, Murchison DF. Surface roughness of various packable composites. Oper Dent 2002;27:243-7. 29. Joniot S, Salomon JP, Dejou J, Gregoire G. Use of two surface analyzers to evaluate the surface roughness of four esthetic restorative materials after polishing. Oper Dent 2006;31:39-46.
30. Wyszecki G, Stiles WS, Wyszecki GN. Color science: concepts and methods, quantitative data and formulae. 2nd ed.New York: John Wiley; 1982. p. 166-9. 31. Tjan AH, Chan CA. The polishability of posterior composites. J Prosthet Dent 1989;61:138-46.
Corresponding author: Dr Haifa M. Barakah PO Box 42615 Riyadh 11551 SAUDI ARABIA E-mail: [email protected] Copyright ª 2014 by the Editorial Council for The Journal of Prosthetic Dentistry.
Clinical Implications Polishing is recommended to improve the staining resistance of Filtek Supreme XT and Z250. Of the materials tested, Tetric EvoCeram had the greatest stain resistance with or without polishing.
Most recent restorative materials have been introduced to the dental profession to meet demands for better esthetics. Color matching and longlasting color stability of the material are 2 major factors that influence the failure or success of an esthetic restoration. Resin-based tooth-colored materials often become discolored because of intrinsic factors, including
the choice of material, the properties of the matrix, and the interface between the matrix and the fillers. These factors may directly affect color stability.1-7 Additionally, extrinsic factors resulting from the contamination of these materials with exogenous sources such as food, drink, and tobacco can cause various degrees of discoloration.3,6,8 Both coffee and cola cause significant
color changes in composite resins after 7 days of immersion.9,10 The surface texture of a toothcolored restoration influences plaque accumulation, discoloration, wear, and the esthetic appearance of the restoration.11 Therefore, proper finishing and polishing are critical procedures that enhance both the esthetics and the longevity of the restored teeth.12,13
Supported by the College of Dentistry Research Center and Deanship of Scientific Research at King Saud University, Riyadh, Saudi Arabia (research project NF 2138). a
Lecturer, Department of Restorative Dental Sciences. Professor, Consultant, Department of Restorative Dental Sciences.
b
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Volume Various polishing techniques have been used with different types of composite resin to produce a smooth surface.13-16 Different polishing protocols have been used over the years,17-19 ranging from multiple-step systems using fine and superfine diamond rotary cutting instruments, aluminum oxide abrasive disks such as Sof-Lex disks (3M ESPE), diamond- and silicon-impregnated soft rubber cups and disks such as Jiffy (Ultradent), Astropol (Ivoclar Vivadent), and OptiShine (Kerr Corp), to 1-step polishing systems20 containing diamond-impregnated cups such as PoGo (3M ESPE), aluminum and silicon oxide disks such as One Gloss (Shofu Inc), and silicon carbide brushes such as OptraPol (Ivoclar Vivadent) and ComposiPro one-step brush (Brasseler). Manufacturers purport that the 1-step polishing systems can be used as single instruments for both finishing and polishing procedures. Different surface finishing and polishing treatments may affect stain resistance by altering the surface roughness of resins.21-23 The most significant factors influencing the stain resistance of dental composite resin, including nanocomposite resin and microfilled and microhybrid composite resins, have been previously investigated.23 Coffee significantly influenced the discoloration of the dental
Table I.
composite resins tested, and discoloration increased as surface roughness increased, except in the case of microfilled composite resin.23 The authors concluded that dental composite resin restorations should be polished to achieve as smooth a finish as possible to increase stain resistance.24 They compared the susceptibility to staining of 3 types of composite resin surfaces (Clearfil Photo, SureFil, and Filtek P60) after polishing with 2 types of 1-step polishing systems (PoGo and One Gloss) and found that PoGo produced surfaces that were less susceptible to staining than those polished with One Gloss.24 Hybrid composite resins are characterized by favorable physical properties. In contrast, microfilled composite resins demonstrate superior esthetic qualities, but, because of their compromised mechanical properties, their application is restricted to non-stressbearing areas.25,26 With the introduction of nanotechnology, a new class of dental composite resin has been developed in recent years.27 Nanoparticle composite resins are purported to combine the mechanical strength of hybrid composite resin and the superior esthetic properties of microfilled composite resin.25 Previous studies have found that nanofilled and minifilled composite resin present a surface
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roughness comparable to a microfilled composite resin, independent of the polishing system used.18,28 In addition, composite resins based on nanofilled and microfilled technology gave the smoothest surfaces after polishing.29 The purpose of this study was to investigate the effect of 3 polishing systems on the stain susceptibility and surface roughness of 2 nanocomposite resins and a microhybrid composite resin. The null hypothesis was that different polishing systems would not affect the surface roughness and stain susceptibility of nanocomposite resins and microhybrid composite resins.
MATERIAL AND METHODS Three different composite resins were selected for this study: 2 types of nanocomposite resins, nanofilled composite (Filtek Supreme XT; 3M ESPE) and nanohybrid composite resins (Tetric EvoCeram; Ivoclar Vivadent), and 1 microhybrid composite resin (Filtek Z250; 3M ESPE) (Table I). The materials tested were prepared in the form of 45 disks (2 mm in height and 10 mm in diameter) by using a circular polytetrafluoroethylene mold (n¼15), which was placed on a transparent matrix strip supported by a glass slide and overfilled with composite resin. The top of the Teflon mold was then
Types of composite resins and manufacturer information
Composite Resin Filtek Supreme XT (3M ESPE)
Code Shade Type of Filler
Composition
FXT
A2
Tetric EvoCeram TEC (Ivoclar Vivadent)
A2
Nanohybrid (Lot L10973)
Matrix: UDMA, additives, catalysts, stabilizers, and pigments Filler: Barium glass, ytterbium trifluoride, mixed oxide, and prepolymers Particle size of the inorganic fillers between 40 nm and 3000 nm with a mean particle size of 550 nm.
A2
Microhybrid (Lot 20080813)
Matrix: BisGMA, UDMA, and BisEMA Filler: oxide, zircon/silica (0.01-3.5mm)
Filtek Z250 (3M ESPE)
Z
Nanofilled Matrix: BisGMA, TEGDMA, UDMA, and BisEMA (Lot 20070829) Filler: nonagglomerated nanosilica filler 20 nm, agglomerated zirconia/silica nanocluster 0.6-1.4 mm with primary particle size of 5-20 nm
Filler Content by Volume/by Weight (%) 59.5/78.5
54/75.5
61/78
BisGMA, bisphenol A-glycidyl methacrylate; BisEMA, ethoxylated bisphenol A-glycol dimethacrylate; TEGDMA, triethyleneglycol dimethacrylate; UDMA, urethane dimethacrylate.
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covered by another matrix strip and glass slide. Both the top and bottom surfaces of the disks were polymerized through the top of the glass slide with a high intensity source of blue light (400500 nm, Halogen Curing Light; Elipar 2500; 3M ESPE, M5560, serial 3021090). According to the manufacturer’s instructions for all the tested materials, they were polymerized for 20 seconds on one side (for 2 mm thickness) and then exposed to light for another 20 seconds on the other side to assure polymerization. The specimens were removed from their molds and immersed in distilled water at 37 C for 24 hours. Both the top and bottom surfaces of all specimens were subjected to wet finishing with 600-grit silicon carbide abrasive paper on a rotary polisher (Automata grinding and polishing unit, Jean Wirtz, serial 8.022869) for 30 seconds. Five specimens (n¼5) from each composite resin (n¼15) were assigned to receive polishing with 1 of the 3 polishing systems used in the study (Table II). Manufacturers’ instructions were followed during the polishing procedures. One side of each specimen was polished and marked with a 1-mm indentation. The other side was not polished and acted as a control. After polishing, each group of specimens was washed, then placed in individual vials
Table II.
containing 20 mL of distilled water and kept immersed for 24 hours at 37 C. All specimens were then subjected to surface roughness testing with a surface profilometer (Surtronic 10 Ra, Rank Taylor Hobson Ltd). Surface roughness (Ra) was recorded from 3 different positions selected on the top and bottom of each specimen. These points were located at equal distances from each other and from the disk periphery and then marked and numbered on the periphery of the specimen so the measurements were made at the same locations. The cutoff value for surface roughness was 0.8 mm, and the traversing distance of the stylus was 5.0 mm. The radius of the tracing diamond tip was 0.5 mm, the measuring force was 10 mN, and the speed was 2 mm/second. The machine was calibrated after every 5 specimens to assure reliable readings. The baseline color measurements, made using the CIE L*a*b* color space of the International Commission on Illumination (CIE), were recorded at another 3 points and marked on the top and bottom of the specimens in areas different from the points selected for surface roughness. The reason was that during the measurement of surface roughness the stylus head might cause minor scratches, which may take up more stain, invalidating the poststaining color measurement.
The color was measured by using a Color Eye 7000A Spectrophotometer (GretagMacbeth). After making baseline measurements, the specimens of each group were immersed in a mixture comprising equal amounts of 3 staining solutions (coffee, green tea, and berry juice) (Table III). The disks were placed vertically in plastic holders and were suspended in the solution. They were then incubated in the dark at 37 C for a total of 3 weeks. The staining solution was replaced with fresh solution every 24 hours during the storage period. Color was recorded for both surfaces of each disk at the end of the 3 weeks of staining. Before color measurement, the specimens were rinsed with distilled water for 1 minute and dried with an air spray.24 The baseline measurement served as the control for each specimen, which enabled the calculation of any color change. The following CIE formula was used to determine the total color difference, DE30: h i1=2 DE ¼ ðDL Þ2 þ ðDa Þ2 þ ðDb Þ2 ; where DL* ¼ (L*1 L*0), Da* ¼ (a*1 a*0), and Db* ¼ (b*1 b*0). Zero represents the baseline reading, whereas 1 represents the color reading after staining. To determine whether statistical differences existed among the groups, a
Polishing systems used and protocols
Polishing Systems
Lot No.
Composition
PoGo** (one step) Dentsply/Caulk
060723
Polymerized UDMA resin, fine diamond powder, and silicon oxide.
Step 1: light intermittent pressure at moderate speed for 1 minute, rinse, and dry Step 2: lightest pressure for 30 seconds, rinse, and dry.
Astropol* (multiple steps) Ivoclar Vivadent
LL0767
Silicon carbide, aluminum oxide, titanium oxide, and iron oxide. Astropol HP additionally contains diamond dust.
Step 1: polishing with Astropol P (green) will result in a very delicate surface finish. Step 2: polishing with microfine Astropol HP to get result in a high gloss. Speed: 7500-10 000 rpm with moderate pressure in conjunction with water.
Hi-Shine* (multiple steps) Polydentia SA
16070806
Synthetic rubber with polishing grains in various grits of the following: aluminum oxide, silicon carbide, and diamond powder.
Step 1: prepolish (pink) Step 2: polish (yellow) Maximum speed of 10 000 rpm
UDMA, urethane dimethacrylate. *Changed after single use. **Changed after two uses.
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Table III.
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Materials used to prepare staining mixture
Material
Brand Name
Preparation
Manufacturer
Coffee
Nescafé (classic)
15 g of coffee poured in 500 mL of boiled distilled water.
Nestlé España SA
Green tea
Lipton
5 tea bags were added to 500 mL of boiled distilled water.
Unilever Gulf FZE
Mixed berry juice
Almarai
51% juice to 49% water.
Almarai Co
Results of Tukey test comparing color change (DE*) and surface roughness (Ra) of composite resins tested between the polished and control surfaces (n¼15)
Table IV.
Composite Resins
Polishing System
Side
DE Mean (SD)
P
Ra Mean (SD)
P
Filtek Supreme XT
PoGo
Treatment
4.57 (2.14)
.20
0.21 (0.06)*
<.001*
Control
5.94 (3.40)
Astropol Hi-Shine
Tetric EvoCeram
Z250
PoGo
Treatment
4.91 (2.29)*
Control
7.14 (3.48)*
Treatment
2.74 (0.53)*
Control
4.88 (0.65)*
Treatment
2.67 (1.24)
Control
2.57 (0.82)
Astropol
Treatment
2.19 (1.38)
Control
2.16 (0.26)
Hi-Shine
Treatment
3.20 (0.66)
Control
3.23 (0.87)
PoGo
Treatment
2.68 (0.62)*
Control
3.26 (0.75)*
Astropol
Treatment
2.62 (0.52)*
Control
3.76 (1.15)*
Hi-Shine
Treatment
3.58 (0.96)*
Control
2.75 (0.66)*
0.30 (0.09)* .04*
0.25 (0.09)
.82
0.24 (0.06) <.001*
0.28 (0.07)
0.78
0.29 (0.05) .79
0.31 (0.10)
1.00
0.31 (0.08) .93
0.33 (0.10)*
.91
0.35 (0.09)*
<.001*
0.22 (0.04)* <.001*
0.26 (0.06)* .02*
0.28 (0.06)*
<.001*
0.33 (0.08)* <.001*
0.28 (0.05)
.48
0.29 (0.04) .01*
0.28 (0.06)
.78
0.28 (0.06)
SD, standard deviation. *Indicates statistically significant difference compared with other DE mean values (P<.05).
power analysis was performed to determine the number of specimens required in each test group. At a¼.05 and from similar previous studies, the standard deviation (SD) was determined as SD¼0.35 with a maximum mean difference of 1, and the power taken was .9. The sample size within each level was determined as 5 observations, with a total of 45 observations. The average surface roughness (Ra, mm) and the color readings were analyzed with statistical software (SPSS, version 16). Two-way ANOVA and the Tukey multiple comparison test
(a¼.05) were analysis.
used
for
statistical
RESULTS Color stability The Tukey multiple comparison test found that Filtek Supreme XT specimens underwent a significantly greater color change in their mean value (DE*¼4.081) at P<.05 compared with Tetric EvoCeram (DE¼2.691) and Z250 (DE¼2.966) (Table IV). No significant difference between Tetric EvoCeram and Z250 (see Table IV) was observed.
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The Filtek Supreme XT specimens that were polished with Hi-Shine recorded the lowest color change (DE¼2.746) (P<.05). No significant difference in color change values were recorded between specimens polished with Astropol (DE¼4.917) and those polished with PoGo (DE¼4.579; see Table IV). When Z250 was polished with Hi-Shine, it showed the greatest color change of 3.584, which was statistically significant (P<.05). Meanwhile, no significant difference was observed between the PoGo (DE¼2.682) and Astropol (DE¼2.629) polishing systems (see Table IV). No
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significant differences were noted in the mean color values obtained for Tetric EvoCeram specimens among the specimens polished with PoGo, Astropol, or Hi-Shine (see Table IV).
Effect of polishing systems on color stability of composite resins Comparing the color change of the polished surfaces with their respective unpolished surfaces (controls), the results showed that for Filtek Supreme XT, all of the polishing systems tested decreased stainability. A significant decrease was noted in the color change values of Filtek Supreme XT specimens when polished with Astropol (P<.05) and Hi-Shine (P<.05) (see Table IV). However, for Z250, Hi-Shine had a significant negative effect on its stainability. Hi-Shine increased the color change values (P<.05), whereas PoGo (P<.05) and Astropol (P<.05) decreased the staining effect (see Table IV). No significant changes were observed in the color of Tetric EvoCeram specimens when polished with the different polishing systems (see Table IV).
Surface roughness Tetric EvoCeram had significantly greater surface roughness (Ra¼0.333) (P<.05) than the mean Ra values of Filtek Z250 (Ra¼0.280) and Filtek Supreme XT (Ra¼0.251), as shown in Table IV. When Filtek Supreme XT was polished with HiShine, its surface roughness (Ra) was not significantly increased (Ra¼0.286) (P¼.054) and was greater than that of PoGo (Ra¼0.213) and that of Astropol (Ra¼0.253). Also no significant differences were noted among the different polishing techniques for Tetric EvoCeram or Z250 specimens (see Table IV).
Effect of polishing systems on surface roughness of composite resins Comparing the surface roughness of the polished surfaces with their respective unpolished surfaces (controls), the results showed that polishing decreased
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5 the surface roughness of Filtek Supreme XT and Z250. However, for Tetric EvoCeram, the different polishing systems did not affect its surface roughness, or even increased the Ra values (see Table IV). PoGo produced significantly smoother surfaces (Ra¼0.213) on Filtek Supreme XT specimens compared with the control surfaces (Ra¼0.300) (P<.05) (see Table IV). The same trend was observed for Z250, with polishing with PoGo producing a smoother surface (Ra polished¼0.280, Ra control¼0.333); however, these values were not significantly different (P>.05) (see Table IV). For Tetric EvoCeram, PoGo had no significant effect on its surface roughness, although Astropol (Ra¼0.333) and Hi-Shine (Ra¼0.353) both produced significantly greater surface roughness (Ra¼0.227, Ra¼0.260) than the control surfaces (P<.05) (see Table IV).
DISCUSSION The results of this study showed that the null hypothesis, which stated that different polishing systems would not affect the stain susceptibility and surface roughness of nanocomposite and microhybrid composite resins, should be rejected. Evidence exists that finishing and polishing procedures may influence the surface quality of composite resin and can therefore be related to the staining resistance of resin-based materials.23 In the present study, Filtek Supreme XT was found to exhibit the highest color change after staining (see Table IV), although it presented the smoothest surfaces compared with Tetric EvoCeram and Z250, regardless of the polishing technique used (see Table IV). It seems likely therefore that the color change of Filtek Supreme XT can be attributed to some intrinsic factors, whereby its color stability is directly related to the resin phase of the composite resin.3 The other possible factor is the porosity of the aggregated filler particles.5 Urethane dimethacrylate (UDMA) has been reported to be more stain
resistant than bisphenol A-glycidyl methacrylate (BisGMA) or triethyleneglycol dimethacrylate (TEGDMA).6 The discoloration of Filtek Supreme XT in the present study may depend on the reported hydrophilicity of the resin matrix in the presence of TEGDMA.5 Tetric EvoCeram was the least stained composite resin among the materials tested (see Table IV). This might be due to the omission of TEGDMA from its composition. Z250 showed a color change comparable with that of Tetric EvoCeram (see Table IV) since UDMA and ethoxylated bisphenol A-glycol dimethacrylate (bisEMA) have replaced TEGDMA in this composite resin.7 The low susceptibility to staining of both materials is probably related to the low water absorption rate of the hydrophobic resins.4 PoGo produced the smoothest surfaces on both Filtek Supreme XT and Tetric EvoCeram when compared with the other polishing systems used in the study (see Table IV). This finding is in agreement with that of several previous studies18,19,31 that reported that PoGo produced the highest gloss when used with different nanofilled composite resin. The superior effectiveness of PoGo as found in the present study could be related to its containing fine diamond abrasives.18,19,31 Tjan and Chan31 reported that for a finishing and polishing system to be effective, the abrasive particles must be relatively harder than the fillers. Otherwise, the polishing agent will only remove the soft resin matrix and leave the filler particles protruding from the surface. In the present study, PoGo produced the smoothest surfaces, but these did not prove to be the most color resistant (see Table IV), a finding in agreement with those of Türkün and Türkün20 and of Reis et al.7 These researchers also found that the smoothest surfaces were not necessarily the most stain resistant. For Filtek Supreme XT, Hi-Shine produced the roughest surfaces (Ra¼0.286 mm), but these exhibited the lowest discoloration (DE¼2.746; see Table IV). In contrast, the PoGo (Ra¼0.213 mm) and Astropol
6
Volume (Ra¼0.253 mm) systems both produced smooth surfaces. However, they exhibited high mean color change values (DE¼4.579 and 4.917; see Table IV). These results appear to support the hypothesis that discoloration is most probably not dependent on extrinsic factors such as surface roughness alone. A strained surface of Filtek Supreme XT caused by the polishing procedure is more susceptible to staining.2 Astropol and PoGo might induce strain in the surfaces of the composite resin during the polishing process. As the strain increases the activity of atoms on the surface, it facilitates the accumulation of dye. Straining of the molecular arrangement of the resin matrix may detach the filler particles from the heat-softened resin.2 Generally, when comparing the surface roughness of the nano- and microhybrid composite resins tested in the study, it was noticed that although Tetric EvoCeram is a nanofilled composite resin, it produced significantly rougher surfaces than Filtek Supreme XT (nanofilled composite resin). Moreover, it produced significantly rougher surfaces than Z250, which is considered a microhybrid type (see Table IV). Meanwhile, comparable surface roughness values were recorded between Filtek Supreme XT and Z250 (see Table IV). The composition of the composite resin may have played an important role in this regard. Filtek Supreme XT demonstrates superior polishability over Tetric EvoCeram,19 which is in agreement with the current research. Filtek Supreme XT contains both nanofillers made of silica and nanoclusters made of silica/zirconia. Nanocluster filler particles consist of loosely bound agglomerates of nanosized filler particles. Ergücü and Türkün19 found that during the polishing of Filtek Supreme XT, the nanoparticles that form these clusters can be worn away, and the whole cluster particles do not need to be plucked from the resin itself. Moreover, by using scanning electron microscope images of Filtek Supreme XT, they found that no particles were dislodged. Ultimately, the
polished surfaces have smaller defects and better polish retention. In contrast, the same researchers also reported that composite resin containing glass fillers such as Tetric EvoCeram showed significantly rougher surfaces than Filtek Supreme XT when both materials were polished with the same polishing system. In the present study, Filtek Supreme XT and Z250, whose filler systems have a similar composition regardless of the filler sizes, presented comparable surface roughness, whereas Tetric EvoCeram, which is composed of different particles (glass), presented a rougher surface. For that reason, this study may relate surface roughness to the hardness of the filler system with polishing abrasives capable of abrading evenly to produce smoother surfaces.
CONCLUSIONS Within the limitations of this in vitro study, the following conclusions were drawn. Stain susceptibility and surface roughness depended mainly on the composition of the material and the polishing procedure. Among the materials tested, Filtek Supreme XT presented the smoothest surfaces and was considered the most stain-susceptible material. The best staining resistance of Filtek Supreme XT was obtained when polished with Hi-Shine. PoGo and Astropol produced the best staining resistance of Z250, whereas HiShine was the least effective. If Tetric EvoCeram is intended to be polished after finishing, Astropol or Hi-Shine should not be used, because they produced rougher surfaces than those obtained by finishing alone.
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4. Douglas WH, Craig RG. Resistance to extrinsic strains by hydrophobic composite resin systems. J Dent Res 1982;61:41-3. 5. Iazzetti G, Burgess JO, Gardiner D, Ripps A. Color stability of fluoride-containing restorative materials. Oper Dent 2000;25: 520-5. 6. Khokhar ZA, Razzoog ME, Yaman P. Color stability of restorative resins. Quintessence Int 1991;22:733-7. 7. Reis AF, Giannini M, Lovadino JR, Ambrosano GM. Effects of various finishing systems on the surface roughness and staining susceptibility of packable composite resins. Dent Mater 2003;19:12-8. 8. Satou N, Khan AM, Matsumae I, Satou J, Shintani H. In vitro color change of composite-based resins. Dent Mater 1989;5: 381-7. 9. Patel SB, Gordan VV, Barrett AA, Shen C. The effect of surface finishing and storage solutions on the color stability of resin-based composites. J Am Dent Assoc 2004;135: 587-94; quiz 654. 10. Mohan M, Shey Z, Vaidyanathan J, Vaidyanathan TK, Munisamy S, Janal M. Color changes of restorative materials exposed in vitro to cola beverage. Pediatr Dent 2008;30:309-16. 11. Morgan M. Finishing and polishing procedures of direct posterior resin restorations. Pract Proced Aesthet Dent 2004;16:211-7; quiz 218. 12. Goldstein RE. Finishing of composites and laminates. Dent Clin North Am 1989;33: 305-18, 210-9. 13. Jefferies SR. The art and science of abrasive finishing and polishing in restorative dentistry. Dent Clin North Am 1998;42: 613-27. 14. Chung KH, Greener EH. Correlation between degree of conversion, filler concentration and mechanical properties of posterior composite resins. J Oral Rehabil 1990;17: 487-94. 15. Roeder LB, Tate WH, Powers JM. Effect of finishing and polishing procedures on the surface roughness of packable composites. Oper Dent 2000;25:534-43. 16. Reis AF, Giannini M, Lovadino JR, Santos Dias CT. The effect of six polishing systems on roughness of two packable composite resins. Am J Dent 2002;15:193-7. 17. St-Georges AJ, Bolla M, Fortin D, Muller-Bolla M, Thompson JY, Stamatiades PJ. Surface finish produced on three resin composites by new polishing systems. Oper Dent 2005;30:593-7. 18. Da Costa J, Ferracane J, Paravina RD, Mazur RF, Roeder L. The effect of different polishing systems on surface roughness and gloss of various resin composites. J Esthet Restor Dent 2007;19:214-24; discussion 225-6. 19. Ergücü Z, Türkün LS. Surface roughness of novel resin composites polished with onestep systems. Oper Dent 2007;32:185-92. 20. Türkün LS, Türkün M. The effect of one-step polishing system on the surface roughness of three esthetic resin composite materials. Oper Dent 2004;29:203-11.
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21. Patel SB, Gordan VV, Barrett AA, Shen C. The effect of surface finishing and storage solutions on the color stability of resin-based composites. J Am Dent Assoc 2004;135: 587-94; quiz 654. 22. Paravina RD, Boeder L, Lu H, Vogel K, Powers JM. Effect of finishing and polishing procedures on surface roughness, gloss and color of resin-based composites. Am J Dent 2004;17:262-6. 23. Lu H, Roeder LB, Lei L, Powers JM. Effect of surface roughness on stain resistance of dental resin composites. J Esthetic Restor Dent 2005;17:102-8; discussion 109. 24. Türkün LS, Leblebicioglu EA. Stain retention and surface characteristics of posterior composites polished by one-step systems. Am J Dent 2006;19:343-7.
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7 25. Walker R, Burgess JO. Comparing resinbased composites. Compend Contin Educ Dent 2004;25:424, 426, 428 passim. 26. Lu H, Lee YK, Oguri M, Powers JM. Properties of a dental resin composite with spherical inorganic filler. Oper Dent 2006;31:734-40. 27. Roberson TM, Helmann HO, Swift EJ Jr. Sturdevant’s art and science of operative dentistry. 4th ed.St Louis: Mosby; 2001. p. 190-6. 28. Ryba TM, Dunn WJ, Murchison DF. Surface roughness of various packable composites. Oper Dent 2002;27:243-7. 29. Joniot S, Salomon JP, Dejou J, Gregoire G. Use of two surface analyzers to evaluate the surface roughness of four esthetic restorative materials after polishing. Oper Dent 2006;31:39-46.
30. Wyszecki G, Stiles WS, Wyszecki GN. Color science: concepts and methods, quantitative data and formulae. 2nd ed.New York: John Wiley; 1982. p. 166-9. 31. Tjan AH, Chan CA. The polishability of posterior composites. J Prosthet Dent 1989;61:138-46.
Corresponding author: Dr Haifa M. Barakah PO Box 42615 Riyadh 11551 SAUDI ARABIA E-mail: [email protected] Copyright ª 2014 by the Editorial Council for The Journal of Prosthetic Dentistry.