|Year : 2016 | Volume
| Issue : 1 | Page : 40-45
Degradability of nanocomposites after cyclic immersion in red and white wines
Saijai Tanthanuch, Boonlert Kukiattrakoon
Department of Conservative Dentistry, Dental Materials Research Unit, Prince of Songkla University, Hat Yai, Songkhla, Thailand
|Date of Web Publication||6-May-2016|
Assoc. Prof. Boonlert Kukiattrakoon
Department of Conservative Dentistry and Dental Materials Research Unit, Faculty of Dentistry, Prince of Songkla University, Hat Yai, Songkhla
Source of Support: None, Conflict of Interest: None
Aims: To investigate surface microhardness of nanocomposites after cyclic immersion in red and white wines. Materials and Methods: Seventy-two specimens of each resin composite were prepared. Before immersion, baseline data of Vicker's microhardness were recorded and surface characteristics were examined using scanning electron microscopy (SEM). Three groups of discs (N = 23) were then alternately immersed in red wine, white wine, and deionized water (as a control) for 25 min and artificial saliva for 5 min over four cycles. The specimens were then stored in artificial saliva for 22 h. This process was repeated for 5 days following immersion in artificial saliva for 2 days. Subsequently, the process was repeated. After immersion, specimens were evaluated and data were analyzed by two-way repeated analysis of variance (ANOVA) and Tukey's honest significant difference (HSD) (α = 0.05). Results: Microhardness values significantly decreased after being immersed in the red and white wines (P < 0.05). SEM photomicrographs presented surface degradation of all groups after immersion in red and white wines. Conclusion: The effect of red and white wines on surface microhardness of nanocomposite restorative materials depended on the physical and chemical compositions of the materials and the types of wine.
Keywords: Erosion, hardness, resin composite, wine
|How to cite this article:|
Tanthanuch S, Kukiattrakoon B. Degradability of nanocomposites after cyclic immersion in red and white wines. J Orofac Sci 2016;8:40-5
|How to cite this URL:|
Tanthanuch S, Kukiattrakoon B. Degradability of nanocomposites after cyclic immersion in red and white wines. J Orofac Sci [serial online] 2016 [cited 2019 Dec 10];8:40-5. Available from: http://www.jofs.in/text.asp?2016/8/1/40/181928
| Introduction|| |
Currently, many people are interested in drinking wine. Some people drink wine during their meal or some people enjoy a glass of wine in social drinking. Several studies recommend that wine consumption in moderation can help benefit health in several ways by reducing coronary heart disease as well as preventing cancer and Alzheimer's disease. ,, Producing quality wine requires tests of quality, after that human tests are performed by a wine taster. However, a number of studies showed that dental erosion occurred in wine tasters due to the frequency of tasting wine and the acidity of the wine. ,, Drinking of wine, acidic food, soft drinks, coffee or tea can result in tooth surface damage and decrease hardness, aesthetic quality, and other properties of these materials.  In addition, wine tasters were found to have stained teeth as a result of their work.  Some studies have reported the effects of wine on surface roughness, erosion, and the staining of tooth-colored filling materials,  which decreases aesthetic results. 
At present, aesthetics plays a major role in the development of aesthetic restorative dentistry. One of the most significant developments in the contemporary era has been the use of nanotechnology to improve new resin-based composites (RBCs). Nanocomposites are a new class of RBCs that have been developed and marketed during the recent years and widely used in anterior and posterior teeth restorations. Nanocomposites are presented as nanofill types, comprising nanomers (nano-sized filler particles) and agglomerations of these particles. These agglomerate described as "nanoclusters" and as nanohybrid types comprising milled glass fillers and nanoparticles (25-75 nm).  Nanocomposites have increased mechanical properties, improved optical properties, better gloss retention, and reduced wear. ,,,
However, there are a number of studies reporting that consumption of acidic food, fruit juices, soft drinks, coffee, tea, or wine can result in surface damage and decrease the hardness, aesthetic quality, and other properties of resin composite ,,, but no study has been conducted reporting the effects of wine on surface hardness of nanocomposites. Therefore, the objectives of this study were to compare the effects of red and white wines on surface hardness of nanocomposites and hybrid resin composite. The null hypothesis was that there would be no surface hardness difference in nanocomposites and hybrid resin composite after the immersion period in red and white wines.
| Materials and Methods|| |
A total of 72 disc-shaped specimens of nanohybrid and nanofilled resin composites (shade A2, [Table 1]) were prepared (10.0 mm in diameter and 2.0 mm in thickness) in a polytetrafluoroethylene cylindrical mold on a glass plate. A mylar matrix strip was covered on the cylindrical mold. A second glass plate was then placed over the mylar strip. A static load of approximately 200 g was applied to extrude excess resin composites and to achieve a smooth and flat surface on each specimen. The specimens were then polymerized for 40 s with a light-activated polymerization unit (Elipar 2500, 3M ESPE, St. Paul, MN, USA). The light intensity was verified with a measuring device (Cure Rite, L.D. Caulk, Milford, DE, USA). After polymerization, the mylar strip and the glass plate on the top and bottom of the mold were removed. The specimen was then removed from the cylindrical mold. No mechanical preparation or abrasion of the specimens were performed.
The pH measurements
Red and white wines (their compositions are shown in [Table 2]) were used in this study. The pH of each wine was determined using a pH meter (Orion 900A, Orion Research, Boston, MA, USA). Ten pH readings of each beverage were acquired so as to give a mean pH measurement.
|Table 2: The mean pH and standard deviation (SD) and titratable acidity (volume of NaOH (mL) to bring the pH to 5.5, 7.0 and 10.0) in the wine tested|
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Storage agent immersions and microhardness testing
Seventy-two discs of nanohybrid and nanofilled resin composites were divided into three groups of 23 specimens for immersion in red wine, white wine, and deionized water (served as a control); the rest of the three samples (before immersion) were subjected to scanning electron microscopy (SEM) (JSM model 5800LV, JEOL, Tokyo, Japan) observations. Each group was subjected to surface microhardness measurement to obtain a baseline value. The hardness value (kg/mm2) of each specimen was determined using a microhardness tester (Micromet II, Buehler, Lake Bluff, IL, USA) with a diamond Vickers indenter (Micromet II, Buehler, Lake Bluff, IL, USA). A load of 1 N was applied to the surface for 10 s. Five indentations, equally spaced over a circle, were made on the surface of each specimen.
The specimens were then alternately immersed in 25 mL of a storage agent for 25 min and in 25 mL of artificial saliva for 5 min conducted over four cycles at room temperature (about 25°C).  After the cyclic immersion, the specimens were returned to the artificial saliva (daily changed) and kept overnight at 37°C. This process was repeated for 5 days following immersion in artificial saliva for 2 days. Subsequently, the entire process was repeated. After immersion, the specimens were evaluated (on day 7 and day 14). The same protocol was used with the different storage agents in this study. In order to maintain the original pH level of the storage agents, the agents were refreshed daily throughout the experiment. After the immersion sequence was completed, the specimens were rinsed with deionized water, blotted dry against filter paper, and subjected to postimmersion surface microhardness measurement. Gradual changes in surface microhardness were recorded at each time interval.
Surface micromorphology analysis
Using SEM, the effects of each agent on the surface micromorphology of the materials before and after immersion were determined. At day 14, three specimens of each restorative material were examined.
Surface microhardness values were tested for significant differences (at α = 0.05) using two-way analysis of variance (ANOVA) with repeated measurement, Tukey's honestly significant difference (HSD), and a t-test for multiple comparisons.
| Results|| |
White wine had the lowest pH (2.98 ± 0.03) and red wine had the highest pH (3.31 ± 0.03). The surface microhardness and erosion values of the materials used before and after immersion are presented in [Table 3]. Before immersion, all groups of each material showed no statistically significant difference in microhardness values (P > 0.05). Overall, red wine significantly decreased microhardness values more than did white wine and deionized water (P < 0.05). Nanohybrid resin composites had significantly more of a decrease in microhardness values than nanofilled resin composites (P < 0.05).
|Table 3: Mean microhardness and standard deviations (SDs) of materials tested immersed in different agents at different times|
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SEM photomicrographs of the nanofilled and nanohybrid resin composite before and after the 14-day immersion period in the different agents are presented in [Figure 1] and [Figure 2], respectively. The red wine groups produced the roughest specimen surface. Nanohybrid groups also produced the roughest specimen surface.
|Figure 1: SEM photomicrographs of nanocomposites after 7 days immersion in storage agents (Í300). Row A = Before immersion, B = Immersion in red wine, C = Immersion in white wine, and D = Immersion in deionized water. Column E = Filtek Z350XT, F = Estelite Sigma Quick, G = Premise, and H = Herculite Ultra|
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|Figure 2: SEM photomicrographs of nanocomposites after 14 days immersion in storage agents (Í300). Row A = Before immersion, B = Immersion in red wine, C = Immersion in white wine, and D = Immersion in deionized water. Column E = Filtek Z350XT, F = Estelite Sigma Quick, G = Premise, and H = Herculite Ultra|
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| Discussion|| |
On the basis of the data, the null hypothesis of this present study should be rejected. This study showed that after being soaked in red and white wines, the surface hardness of all groups significantly decreased (P < 0.05). Microhardness values of all groups decreased from the initial week of immersion until the end of the 14-day period and the greatest change in hardness occurred within the first 7 days. The surface hardness of the specimens was decreased by a chemical reaction or dissolution; it was not exposed to any mechanical force.
The decrease in surface hardness is related to the pH, the titratable acidity, and the alcohol in the beverages. The result of this study showed that wine's acidity has a pH ranging 2.98-3.31, which is similar to previous studies.  White wine has a lower pH than red wine. Wine is composed of 1-5 g/L tartaric acid, 1-4 g/L maleic acid, and other acids including succinic acid, lactic acid, citric acid, and acetic acid.  One study has shown that a low pH in acidic food and drink influences erosive wear in restorative materials. 
Surface degradation of resin composites from an acidic beverage is not absolutely dependent on its pH but it is not strongly related to the titratable acid content in the beverages. , The pH values show only a quantity of the free hydrogen ion concentration. It does not present the hydrogen ion residual in an undissociated form. The potential surface degradation of resin composite from acidic beverages should be measured for both the pH value and titratable acidity. However, citric acid has been presented to be erosive for dental hard tissues and RBC materials.  Acidity might dissolve and soften the resin matrix and then result in dislodging the filler particles and reducing the load resistance of RBC materials and therefore, decreasing the surface hardness of RBCs. 
Although white wine has a lower pH than red wine, red wine is composed of 13.5% alcohol by volume, more than white wine that has 12.5% alcohol by volume. McKinney and Wu  reported that alcohol in drinks soften polymer matrixes and dislodge filler particles, resulting in increases in the degree of erosion and decreases in the surface hardness of RBCs. The results of this present study showed that surface hardness decreased from the first week until the end of the 14-day period of immersion in red wine, white wine, and deionized water. The effect of water uptake can degrade RBCs  because water absorption of RBCs causes hydrolysis of coupling agents and loss of chemical bond between the resin matrix and filler particles, causing filler particles to dislodge from the outer surface, resulting in surface roughness and reduction of surface hardness of RBCs.  The types of resin influence water absorption of RBCs. Hydroxyethylmethacrylate absorbs more water than Bis-GMA. Moreover, filler loading may affect the water absorption of RBCs: The higher the filler loading, the lower the water absorption.  However, Herculite Ultra has a filler load of 78% by volume while Premise and Estelite Sigma quick have a filler load of 70 and 71% by volume, and Z350XT is a nanofilled resin composite that has a filler load of 55.6% by volume.
All the materials tested became rougher after soaking in the red and white wines as seen from SEM photomicrographs. Nanohybrid resin composite groups became rougher than nanofill resin composite because of filler particle size. Filtek Z350XT is a nanofilled resin composite comprising 20 nm silica and 4-11 nm zirconia particles. Premise, Estelite, and Herculite Sigma Quick are nanohybrid resin composites. The average filler particle size of Premise is 0.4 μm, Estelite sigma quick is 0.3 μm, and Herculite contains an average filler particle size of 0.6 μm.
This study has limitations as it was an in vitro study and an incomplete replication of the complex oral environment. While further studies may show the in vivo effects of beverages and completely replicate the complex oral environment, this study at least confirms the erosive potential of red and white wines, which can potentially degrade RBCs. The public should be aware of this fact.
| Conclusion|| |
Within the limitations of this study, the following conclusions were drawn. The red and white wine used significantly reduced the surface hardness of the nanocomposites, particularly at the end of the 14 days immersion period. Immersion in red wine caused greater reduction in surface hardness over time than white wine. Moreover, the effect of red and white wine on the surface hardness of nanocomposites also depended upon the exposure time and chemical composition of the restorative materials and type of wines.
Financial support and sponsorship
Faculty of Dentistry Research Fund, Prince of Songkla University.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]