Surface roughness and erosion of nanohybrid and nanofilled resin composites after immersion in red and white wine.

AIMS: This study aimed to investigate the effects of red and white wine on the surface roughness and erosion of nanohybrid and nanofilled resin composites.
MATERIALS AND METHODS: Sixty specimens of each resin-based composite (RBC) were prepared. Before immersion, baseline data roughness values were recorded using a profilometer. Three groups of discs (n = 20) 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, the specimens were evaluated and data were analyzed by two-way repeated analysis of variance (ANOVA) and Tukey's honestly significant difference (HSD) (α = 0.05).
RESULTS: Red wine caused significantly greater roughness and erosion than did white wine and deionized water (P < 0.05). Nanohybrid resin composites were significantly rougher than nanofilled resin composites (P < 0.05).
CONCLUSION: The effects of red and white wine on the surface roughness and erosion of resin composite restorative materials depended upon the physical and chemical composition of the restorative materials and the types of wine.

INTRODUCTION

Over the past 3-4 years, wine consumption has dramatically increased across most markets and wine sectors. There are many people who drink wine between meals or in social drinking. Several studies showed that wine tasters have dental erosion due to the frequency of tasting wine and that erosion is related to the acidity of wine.[1] Additionally, drinking wine may affect the esthetic and physical properties of resin-based composite (RBC) restorations.[2]

Currently, RBCs are widely used in esthetic restorative dentistry. Nanocomposites are the latest types of RBCs. Nanocomposites are occur in two subtypes, nanofilled and nanohybrid. They are becoming very popular in esthetic restorative dentistry because of the many advantages of their material compositions, in terms of the physical and mechanical properties, and they are widely used in restoring both anterior and posterior teeth.[34] Nanofilled RBCs contain nanomers and nanoclusters. The particle size of nanomers is in the range of 5-75 nm. Nanoclusters are 0.6-1.4 μm and they are agglomerates of primary zirconia/silica nanoparticles (5-20 nm in size) fused together at points of contact, and the resulting porous structure is infiltrated with silane.[4] Nanohybrid RBCs consist of nanoparticles (40-50 nm) and milled glass fillers.[3]

The longevity of the materials used is one of the main factors for the success of esthetic restoration. Surface roughness may be one of the factors used to predict the longevity of the restoration due to surface degradation and erosive properties.[5] Alcohol composition in wine may affect the esthetic and physical properties of the RBC restorations[2] because alcohol is also thought to act as a plasticizer of the polymer matrix.[6] When RBC restorations are eroded, the teeth may sustain loss of anatomy, marginal discrepancy of restoration, secondary caries,[7] and an increase in the surface roughness of restorations. Surface roughness of restoration results in plaque and staining deposits at restoration, tissue irritation, possible gingivitis,[8] and reduced longevity of restorations.[910]

There are a number of studies presenting the erosive effects of wine on tooth structure,[11112] and red wine on microhybrid and nanofilled resin composites,[131415] but only a few studies reported the effects of wine on the surface roughness and erosion of nanofilled and nanohybrid RBCs. Therefore, the objective of this in vitro study was to investigate the effects of red and white wine on the surface roughness and erosion of nanofilled and nanohybrid RBCs, and to investigate the pH and titratable acidity of different beverages. The null hypothesis was that there would be no surface roughness and erosion difference between the nanohybrid and nanofilled resin composites after the immersion period in red wine and white wine.

MATERIALS AND METHODS

Specimen preparations

A total of 60 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. The cylindrical mold was covered with a mylar matrix strip. 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 obtain 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, and the specimen was then removed from the cylindrical mold. No mechanical preparation or abrasions of the specimens were performed.

Table 1

Resin composite materials used in this study

The pH measurements

Red and white wine were used in this study; their compositions are shown in Table 2. 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 obtained so as to give a mean pH measurement.

Table 2

Wine and their compositions used in this study

Storage agent immersions and surface roughness measurements

Sixty discs of nanohybrid and nanofilled resin composites were divided into three groups of 20 specimens for immersion in red wine, white wine, and deionized water (serving as a control), respectively. Each group was subjected to a surface roughness measurement for baseline data (before immersion). Surface roughness determinations were measured by a profilometer (Surfcorder model SE-2300, Kosaka Laboratory Ltd., Tokyo, Japan). The cutoff value for surface roughness was 0.8 mm and the traversing distance of the stylus was 4 mm. The radius of the tracing diamond tip was 5 μm, and the measuring force and speed were 4 mN and 0.5 m/s, respectively. The surface roughness values (Ra, the arithmetical average of surface heights, for surface roughness and Rmax, the magnitude of the peak-to-valley height in all cutoff lengths, for erosion measurement[16]) of each specimen were obtained in five different positions (1.5 mm apart), each before and after immersion in the storage agents.

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).[17] After the cyclic immersion, specimens were returned to the artificial saliva (changed daily) and kept overnight at 37°C. This process was repeated for 5 days following immersion in artificial saliva for 2 days (1 trip). Subsequently, the entire process was repeated again (for a total of 2 trips). After immersion, specimens were evaluated (on day 7 for 1 trip and day 14 for 2 trips). 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 roughness measurement.

Statistical analysis

The surface roughness and erosion values were subjected to two-way analysis of variance (ANOVA) and Tukey's honestly significant difference (HSD) for multiple comparisons (at α = 0.05).

RESULTS

White wine had the lowest pH (2.97 ± 0.02) and red wine had the highest pH (3.32 ± 0.02). The surface roughness and erosion values of the materials used before and after immersion are presented in Figures 1 and 2. Overall, red wine caused significantly rougher surfaces than did white wine and deionized water (P < 0.05). Nanohybrid RBCs were significantly rougher than nanofilled RBCs (P < 0.05).

Figure 1

Ra mean values and standard deviations of each resin composite immersed in red and white wines at different times. *Indicates statistically significant difference between before and at 7 days, and at 7 and 14 days for each parameter and resin composite. †,‡indicates statistically significant difference among materials for each storage agent. A-EIndicates statistically significant difference among materials and storage agents for 7 and for 14 days

Figure 2

Rmax mean values and standard deviations of each resin composite immersed in red and white wines at different times. *Indicates statistically significant difference between before and at 7 days, and at 7 and 14 days for each parameter and resin composite. †,‡Indicates statistically significant difference among materials for each storage agent. A-EIndicates statistically significant difference among materials and storage agents for 7 and for 14 days

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 roughness (Ra) and erosion (Rmax) of all groups significantly increased, which is similar to a previous study.[18]

With the demand for esthetic restorations and the improvement of RBCs, nanohybrid and nanofilled RBCs have become very popular choices for restoration. However, there are limitations on the longevity of the esthetic restoration.[5] The surface roughness and erosion of materials also play an important role in replacement in esthetic areas.

This study indicated that wine's acidity has a pH ranging 2.97-3.32, which is similar to a previous study.[19] The types of wine used contained 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.[20] There are a number of studies that have reported that acids might change the physical properties of RBCs under acidic conditions over time. In one study, RBCs presented a surface roughness with voids which showed that the acidity might have had a greater softening effect on the resin matrix or hydrolysis of the silane coupling agent and could promote dislodgement of filler particles, resulting in facilitating the erosion of RBCs.[2122]

Red wine used in this study contained 13.5% alcohol by volume, while white wine contained 12.5% alcohol by volume. Alcohol in beverages causes significant increases in surface roughness and erosion in resin composite because alcohol is also thought to act as a plasticizer of the polymer matrix to soften and dislodge filler particles, resulting in a rapid increase in surface roughness and erosion.[61823] The softening effect of alcohol on the RBCs may be due to the susceptibility of bisphenol A-glycidyl methacrylate (Bis-GMA) and urethane dimethacrylate (UDMA)-based polymers.[24] This study showed that after soaking the specimens in red wine, the surface roughness and erosion of all groups significantly increased more than for white wine because red wine has a higher ethanol concentration (13.5 vol%) than white wine (12.5 vol%). This result corresponds to the results of previous studies[131415] that evaluated the effect of red wine on microhybrid and nanofilled resin composites.

In addition, water absorption of the RBCs was an important factor in changing the surface roughness and erosion of RBCs.[25] When RBCs absorb water, a coupling agent causes hydrolysis and a loss of chemical bonding between filler particles and the resin matrix. Filler particles dislodge from the outer surface of the RBCs, causing the surface to become rougher and erode.[26] The types of resin matrix in RBCs are also influenced by the water absorption of RBCs. Soderholm et al.[27] reported that Bis-GMA absorbs less water than the resin made by triethylene glycol dimethacrylate (TEGDMA), but absorbs more water than the resins made by UDMA and Bis-EMA. RBCs used in this study showed that nanohybrid resin composites composed of TEGDMA, while nanofilled resin composite (Filtek Z350 XT) did not.

The filler particle size has been correlated to the surface roughness and erosion of RBCs. Large filler particles will have rougher surfaces than smaller filler particles.[282930] The RBCs used in this study were Filtek Z350 XT (nanofilled resin composite), which have an average filler particle size 0.005-0.02 microns smaller than the nanohybrid resin composites (Estelite Sigma Quick 0.2 micron, Premise 0.4 micron, and Herculite Ultra 0.4 micron). The results of this study showed that nanohybrid resin composites presented greater surface roughness and erosion than nanofilled resin composites after immersion in red wine and white wine.

The results of this study showed that the alcohol composition in wine may affect the surface roughness and erosion of nanocomposites. However, this study evaluated only in vitro effects, with some limitations. The dilution effects of saliva, including the pH change in the oral cavity, should also be considered. Therefore, further studies are required to examine the effects of wines in vivo.

CONCLUSION

Within the limitations of this study, the following conclusions could be drawn. Red and white wine significantly increased the surface roughness and erosion of nanofilled and nanohybrid resin composites after evaluation at the end of the 14 days’ immersion period. The effects of red and white wine on the surface roughness and erosion of resin composite restorative materials depend upon the physical and chemical composition of the restorative materials and the types of wine.

Financial support and sponsorship

Faculty of Dentistry research fund, Prince of Songkla University.

Conflicts of interest

There are no conflicts of interest.