Microsc. Microanal. 20, 1234–1239, 2014 doi:10.1017/S1431927614001299
© MICROSCOPY SOCIETY OF AMERICA 2014
Effects of Immersion Media and Repolishing on Color Stability and Superficial Morphology of Nanofilled Composite Resin Ana Luísa Botta Martins de Oliveira,1,* Ana Carolina Botta,2 Juliana Álvares Duarte Bonini Campos,1 and Patrícia Petromilli Nordi Sasso Garcia1 1 2
Department of Social Dentistry, Araraquara School of Dentistry, University of Sao Paulo State, Sao Paulo 14801-903, Brazil Stony Brook School of Dental Medicine, Department of General Dentistry, NY 11794, USA
Abstract: This study evaluated the inﬂuence of ﬂuoride mouth rinses and repolishing on the superﬁcial morphology and color stability of nanoﬁlled resin. About 150 specimens were prepared and polished using aluminum oxide discs for 15 s with a pressure of 2 kg. The experimental groups were divided according to the immersion medium (artiﬁcial saliva, 0.5% sodium ﬂuoride, Fluordent Reach, Oral B, Fluorgard) and repolishing procedure (without and with). The specimens were continuously immersed for 1 week. Thereafter, half of each sample was repolished. A color reading was performed after 24 h of immersion in the artiﬁcial saliva baseline, after continuous immersion, and after repolishing. The superﬁcial morphology was examined using scanning electron microscopy (SEM) in a qualitative way. Color change (ΔE) data were submitted to a mixed analysis of variance using a Shapiro–Wilk test (p > 0.05 for the different immersion media) and Sidak’s test (p < 0.05 for the differences between groups). In the interaction between the repolishing and the immersion media, Fluorgard showed a statistical difference between the ΔE values with and without repolishing (p < 0.0001). On the SEM observations, both Fluordent Reach and Fluorgard caused degradation of the superﬁcial resinous matrix of the composite after continuous immersion. This matrix was removed after repolishing. Key words: ﬂuorine, composite resins, color, dental polishing, SEM, microscopy
I NTRODUCTION The success and longevity of a restoration are related to its color stability. Intrinsic and extrinsic factors may inﬂuence the susceptibility of esthetic restorative materials to staining. The routine use of ﬂuoride solutions for daily mouth rinsing can be considered an extrinsic factor because these can change the color and superﬁcial morphology of composites because of their chemical composition (Garcia et al., 2002). Staining is one of the main causes of esthetic restoration replacement (Anfe et al., 2011). Thus, repairing stained restorations is an alternative to the early replacement of a restoration that is still functional (Turkun & Turkun, 2004; Mathias et al., 2010; Mundim et al., 2010; Anfe et al., 2011; Garoushi et al., 2013). There are several ways to remove superﬁcial staining: brushing with toothpaste, repolishing procedures, and the use of bleaching agents. According to Turkun & Turkun (2004) and Garoushi et al. (2013), the beneﬁt of brushing is highly dependent on the pressure and the type of abrasive used, and it is a slower process. Bleaching agents should preferably be used only with extensive restorations, so that they do not touch the dental structure. Thus, repolishing may be a more viable option for removing the superﬁcial layer of the composite resin in order to recover the initial Received January 21, 2014; accepted May 5, 2014 *Corresponding author. [email protected]
color or to reduce the perception of a negative effect in composites without severe color changes (Anfe et al., 2011). Various studies have been conducted to determine the effect of repolishing in stain removal (Turkun & Turkun, 2004; Mathias et al., 2010; Mundim et al., 2010; Anfe et al., 2011). However, the association of color stability with the superﬁcial characteristic of a material after repolishing procedures needs to be better investigated. Therefore, the objective of this study was to evaluate the effects of different ﬂuoride solutions and repolishing on changes in the color and superﬁcial morphology of a nanoﬁlled composite resin.
Experimental Design This research consists of a double-blind experimental in vitro study. The dependent variable was the color stability, and the independent variables were the repolishing procedure (two levels: without and with) and immersion medium (ﬁve levels: artiﬁcial saliva, manipulated ﬂuoride solution, Fluordent Reach, Oral B, Fluorgard). Fifteen samples were used for each experimental condition (n = 150). The prepared samples were randomly distributed in each experimental group. The nanoﬁlled composite resin Filtek Z350XT (3M ESPE, St. Paul, MN, USA), shade B1E, was used in each specimen’s preparation from a stainless steel matrix, with
Red Colgate, Sao Bernardo do Campo, SP, Brasil Fluorgard
Blue Mint Gillette, Sao Paulo, SP, Brazil Oral B
0.05% sodium ﬂuoride, water, glycerin, ethyl alcohol, poloxamer 407, methylparaben, mint aroma, dibasic sodium phosphate, sucralose, monobasic sodium phosphate, cetylpyridinium chloride, propylparaben, yellow food coloring 5, FD&C Food Coloring No. 1 0.05% sodium ﬂuoride, water, glycerin, PEG-40 hydrogenated castor oil, methylparaben, 0.053% monohydrated cetylpyridinium chloride, sodium saccharin, sodium benzoate, propylparaben, FD&C Blue No. 1 0.05% sodium ﬂuoride, water, sorbitol, polysorbate 20, potassium sorbate, sodium biphosphate, phosphoric acid, red coloring, aromatic composition
Santa Paula Pharmacy, Araraquara, SP, Brazil Johnson & Johnson, Sao Jose os Campos, SP, Brazil
Potassium chloride (0.96 g), sodium chloride (0.67 g), magnesium chloride (0.04 g), potassium phosphate (0.27 g), calcium chloride (0.12 g), nipagin (0.01 g), nipasol (0.1 g), carboxymethyl cellulose (8.0 g), sorbitol (24.0 g), and water (1,000 ml) 0.05% sodium ﬂuoride Colorless Flavorless
Sodium ﬂuoride—manipulated Fluordent Reach
Color change readings were performed using a spectrophotometer for colorimetry (color guide 45/0, PCB 6807; BYK-Gardner GmbH, Gerestsried, Germany), with wavelengths ranging from 400 to 700 nm through direct transmission with a standard D65 illuminant on a white background (Vichi et al., 2004; Mundim et al., 2010; Sarac et al., 2006), with appropriate calibrations (ΔL = 0.90; Δa = 0.75; Δb = 0.95).
Santa Paula Pharmacy, Araraquara, SP, Brazil
Color Stability Assessment
For half of the samples, after immersing the specimens for a week in the solutions, the polishing procedures described above were repeated using the same material.
For the staining process, the specimens were continuously immersed for 1 week (10,080 min), individually in different media: artiﬁcial saliva, a solution of 0.05% sodium ﬂuoride, Fluordent Reach, Oral B, and Fluorgard. The amount of solution used was 5 ml. Characteristics of the immersion media used are listed in Table 1.
Identiﬁcation and Characteristics of Immersion Media.
four circular holes with a diameter of 10 mm and a thickness of 2 mm (Botta et al., 2008; Oliveira et al., 2012). The material was inserted into the matrix in a single increment and covered by a 10-mm-wide polyester strip (K-Dent; Quimidrol, Com. Ind. Importação Ltda, Joinville, SC, Brazil) and a glass plate. A 1 kg stainless steel weight was applied for 30 s to allow the removal of excess material and make the surface smooth and standardized (Badra et al., 2005). After this period, the applied weight and glass plate were removed, and photopolymerization was performed for 40 s using an UltraLume LED 5 (Ultradent) apparatus, with an irradiance of 790 mW/cm2, which was constantly monitored using a radiometer (Curing Radiometer Model 100; Demetron Research Corp., Danbury, CT, USA). The sample was subjected to ﬁnishing and polishing procedures using aluminum oxide discs (Super-Snap®; Shofu Dental Corp., Kyoto, Japan), which were 12 mm in diameter, in descending sequence of granulation. Each disc was used on the surface for 15 s (Guler et al., 2005). The ﬁnishing and polishing procedures were performed using a standardized pressure of 2 kg in a stainless steel matrix with central height regulation (Botta et al., 2008; Oliveira et al., 2012). Between polishing with each granulation, the specimens were washed with air–water jets for 5 s. At the end of the process, they were placed in water in an Ultrasonic Cleaner 1440 Plus (Odontobras; Comércio de Eq. MedicosOdontologicos LTDA, Ribeirao Preto, SP, Brazil) for 30 min, with the objective of removing any impurities deposited on the surface. Then, the specimens were immersed in artiﬁcial saliva and stored in a bacteriological incubator (EBC1), where they were kept at a temperature of 37 ± 1°C for 24 h.
Inﬂuence of Immersion Media and Repolishing
Ana Luísa Botta Martins de Oliveira et al.
After 24 h of immersion in artiﬁcial saliva, an initial color measurement (baseline) was performed for each specimen. Subsequent readings were performed after the specimens were continuously immersed in the solutions for 1 week (ΔE1) and after the repolishing procedures (ΔE2). The color change value ΔE* was calculated according to the following formula (Wyszecki & Siles, 1982): ΔE* = [(ΔL*)2 + (Δa*)2 + (Δb*)2]1/2, where L* stands for lightness, a* for green–red (− a = green; + a = red) and b* for blue– yellow ( − b = blue; + b = yellow).
Scanning Electron Microscopy (SEM) Specimens were prepared for SEM analysis after reﬁnishing procedures. To remove debris on the surface, specimens were washed in distilled water followed by washing in deionized water in an ultrasonic bath (Sonic Clean; D.M.C. Equipamentos, Sao Carlos, SP, Brazil) for 10 min. The samples were coated with 10 nm of gold in a metallizer, Coating System Bal-Tec Med 020 (Bal-Tec, Liechtenstein) and kept in a desiccator until the time of analysis. SEM photomicrographs were obtained at the Instrumental Chemical Analysis Center of São Carlos (CAQI/IQSC/USP) with Zeiss Leo 440 (Cambridge, England) with an Oxford detector (model 7060), operating at an accelerating voltage of 20 kV. Images were obtained by backscattered electron imaging, using the Four Quadrant Backscattered Electron Detector Type 400.
Statistical Analysis Effects of the repolishing and immersion media on color stability were tested after 1 week of continuous immersion in solutions (ΔE1) and after repolishing (ΔE2), using a mixed analysis of variance, after validating the normality assumption using a Shapiro–Wilk test (p >0.05 for the different immersion media). The differences between groups were evaluated by Sidak’s test, with a signiﬁcance level of 5%. Analysis of SEM micrographs was qualitative, so a descriptive image method was employed in this study.
RESULTS Table 2 lists the mean and standard deviation of the color stability (ΔE) values of the specimens for the different immersion media and repolishing conditions. It was observed that the immersion medium (p < 0.0001; F = 9.450; η2p = 0.351; π = 0.999), repolishing condition (p < 0.0001; F = 14.430; η2p = 0.314; π = 1.000), and their interaction (p < 0.0001; F = 11.880; η2p = 0.404; π = 1.000) had statistically signiﬁcant differences. Before repolishing, Fluorgard presented a statistically different color change from the others (p < 0.0001), whereas, after repolishing, there was no statistical difference between the immersion media (p = 1.000). In the interaction between the repolishing and immersion media, the only solution that showed a statistically signiﬁcant difference in
Table 2. Mean and Standard Deviation of Color Change (ΔE) of Filtek Z350XT Composite Resin Specimens on Immersion Media and Repolishing. ΔE Immersion Media Artiﬁcial saliva Manipulated ﬂuoride Oral B Fluordent Reach Fluorgard Total
2.08 ± 0.75 2.16 ± 0.82aA 2.77 ± 0.76aA 2.71 ± 0.55aA 4.43 ± 1.64bA 2.83 ± 1.28 aA
2.26 ± 0.61aA 2.04 ± 0.56aA 2.10 ± 0.57aA 2.23 ± 0.46aA 2.42 ± 0.77aB 2.21 ± 0.60
Sidak’s post-test: equal lowercase and uppercase letters indicate statistical similarity in lines and columns, respectively.
the ΔE values with and without repolishing was Fluorgard (p < 0.0001). The results obtained from SEM of the studied composite resins are shown in Figures 1–5. According to the SEM observations, both Fluordent Reach and Fluorgard caused degradation of the superﬁcial resinous matrix of the composite resin after continuous immersion in these solutions. It was found that this degraded superﬁcial resinous matrix was removed after repolishing, which increased the exposure of inorganic particles.
DISCUSSION Composite resins have been improved over time but still have some deﬁciencies that limit their longevity, such as susceptibility to staining (Elhamid & Mosallam, 2010; Mathias et al., 2010; Mundim et al., 2010; Domingos et al., 2011; Anfe et al., 2011; Gonulon & Ylmaz, 2012). This study demonstrated that after the staining process, Fluorgard was the only immersion medium that caused a clinically visible color change (p < 0.0001) in Filtek Z350XT resin. This ﬂuoride solution contains phosphoric acid in its composition, which can dissolve and erode an organic matrix, leaving it susceptible to pigmentation (Aliping-Mckenzie et al., 2004; Mundim et al., 2010). This was observed in the superﬁcial morphology analysis (Fig. 5). For the specimens immersed in Fluordent Reach, SEM revealed (Fig. 4) that the organic matrix also suffered superﬁcial degradation, although the color stabilities of specimens immersed in this solution were not affected. This degradation can be explained by the presence of alcohol in its composition, which causes organic matrix softening (Asmussen, 1984; Setembrini et al., 1995; Diab et al., 2007). Both a clinically visible color change (ΔE > 3.3) (Iazetti et al., 2000; Patel et al., 2004; Turkun & Turkun, 2004; Vichi et al., 2004) and an alteration of the superﬁcial morphology of a composite resin interfere with the restoration quality, and thus its longevity (Anfe et al., 2011; Mundim et al., 2010). Therefore, in order to avoid the premature replacement of a restoration without recurring caries, repolishing can be a viable alternative (Anfe et al., 2011; Mundim et al., 2010).
Inﬂuence of Immersion Media and Repolishing
Figure 1. Composite resin immersed in artiﬁcial saliva according to reﬁnishing procedure: material observed by scanning electron microscopy (1,500 × ).
Figure 2. Composite resin immersed in manipulated sodium ﬂuoride according to reﬁnishing procedure: material observed by scanning electron microscopy (1,500 × ).
Figure 3. Composite resin immersed in Oral B according to reﬁnishing procedure: material observed by scanning electron microscopy (1,500 × ).
The color stability analysis showed that repolishing of the specimens immersed in Fluorgard transformed the ΔE values from clinically visible to imperceptible. Mundim et al. (2010) observed that repolishing after staining signiﬁcantly reduced the ΔE values of specimens immersed in coffee to clinically acceptable levels. Turkun & Turkun (2004) obtained lower ΔE values for composite resin specimens immersed in both tea and coffee after repolishing. Rutkunas & Sabaliauskas (2009) veriﬁed that repolishing was effective
at improving the esthetic appearance of the provisory materials used in prostheses, partially removing the pigments on the surface of the restoration. Garoushi et al. (2013) evaluated specimens immersed in tea, coffee, Pepsi, and water, and noticed a decrease in the ΔE values after repolishing. In the superﬁcial morphology analysis, it was observed that repolishing removed the degraded resinous matrices of the specimens immersed in Fluorgard and Fluordent Reach.
Ana Luísa Botta Martins de Oliveira et al.
Figure 4. Composite resin immersed in Fluordent Reach according to reﬁnishing procedure: material observed by scanning electron microscopy (1,500 × ).
Figure 5. Composite resin immersed in Fluorgard according to reﬁnishing procedure: material observed by scanning electron microscopy (1,500 × ).
It may be suggest that the staining depth of the Filtek Z350XT composite resin, when immersed in Fluorgard, was superﬁcial (