Semi-nutritious Liquids effect on Shear Bond Strength of Repaired Composite with Universal bonding
Subject Areas : Restorative and Aesthetic DentistrySomayeh shiyasi 1 , Parvin Mirzakouchaki 2 , Mina Ahmadi 3
1 - school of dentistry, Islamic Azad University, Isfahan (khorasgan) Branch, Isfahan, Iran
2 - Department of Operative dentistry, Faculty of dentistry, Isfahan (khorasgan) Branch, Islamic Azad university, Isfahan, Iran
3 - Department of Operative Dentistry, School of Dentistry, Islamic Azad University, Isfahan (Khorasgan) Branch, Isfahan, Iran
Keywords: Composite, Shear Bond Strength, G-premium bond and Non-nutrient Liquids,
Abstract :
Background: Composite resins undergo changes in properties due to various oral irritations over time. This study analyzed the effect of semi-nutritious liquids on the shear bond strength of repaired composite with universal bonding Materials and methods: This laboratory experiment used 80 samples of rectangular cubes made of Z250 composite. The samples were subjected to Thermocycling in an incubator and divided into four experi-mental groups, one control group, and stored in different solutions for seven days. After the aging process, the samples were roughened, bonding was applied, and a composite cylinder was placed on the previous composite. The bond strength was then calculated with an Instron device, and the data were analyzed using one-way ANOVA and Bonferroni's post hoc test (α=0.05). Results: Maximum average of bond strength in semi-nutrient liquids was recorded in descending order 25.53MPa for saliva , distilled water (20.24MPa), ethanol (18.04 MPa), citric acid (16.24 MPa), and Hep-tane (9.83 MPa), respectively. Conclusions: Artificial saliva yielded the highest average bond strength, while distilled water, ethanol, citric acid, and heptane resulted in decreasing bond strength.
Semi-nutritious Liquids effect on Shear Bond Strength of Repaired Composite with Universal bondings
Background: Composite resins are affected by many irritations in the oral environment,their properties change with aging. The aim of this study was to analysis the effect of Semi-nutritious Liquids on Shear Bond Strength of Repaired Composite with Universal bondings .
Materials and methods: this laboratory experimental study has 80 samples of rectangular cubes of Z250 composite. The samples were subjected Thermocycling procedure in an incubator. They were divided into five 16-item categories; 4 experimental groups and one control group (distilled water). Samples were stored in distilled water solutions, citric acid 2%, Heptane, Bioethanol 75%, and artificial saliva (in the incubator) at the temperature of 37°c for 7 days. After aging process, samples roughed and bonding were applied and a composite cylinder was put on the previous composite using a plastic washer mold of the same diameter and height and cured. Then, an Instron device with a vertical force and a speed of 0.5 per minute was used to separate the composites from the connection area. The bond strength was calculated in Mega-Pascal. The data were analyzed with one-way ANOVA and Bonferroni's post hoc test (α = 0.05).
Results: Maximum average of bond strength in semi-nutrient liquids was recorded for artificial saliva (25.53MPa), distilled water (20.24MPa), ethanol (18.04 MPa), citric acid (16.24 MPa), and Heptane (9.83 MPa), respectively.
Conclusions: maximum average bond strength was in artificial saliva. The bond strength is reduced in distilled water, ethanol, citric acid, and Heptane, respectively.
Key Words: Composite, Shear Bond Strength, G-premium bond and Non-nutrient Liquids
INTRODUCTION
Resin composite is one of the most frequently used direct restorative materials in clinical practice due the combination of favorable mechanical properties and excellent optical properties that mimic the tooth structure. However, resin composites have limitations related to long-term degradation and polymerization shrinkage, which influences the restoration longevity and often result in a repetitive restorative cycle. In cases where the imperfections of a composite restoration are minor, such as a slight loss of anatomical shape or external discoloration, it might not be necessary to entirely replace the restoration. The repair technique, however, may also serve as an alternative procedure to address these minor issues(1).
A wide range of composite materials including hybrid, nano filled, silorane,ormocer and compomers are available for the direct restoration of teeth(2).. Distinct mechanical properties of these materials are due to the type of monomer system, the composition of filler, the chemical structure of the filler coupling agents, and the resin matrix (silane), leading to the differential resistance of these composites against mechanical forces and chemical degradation (3).
One of the most prevalent problems in restorative dentistry is associated with the degradation and quality reduction of resin composite, which is caused by the interaction of these materials with saliva, food, and beverages(4). This is a serious problem due to the widespread use of composites (5-8). Changes in pH or moisture in the oral cavity may deteriorate the structure of composites over time (9). Previous studies have indicated that certain diets and beverages can cause surface deterioration of dental materials (10). Components of these foods can soften the organic components of the composites and cause the initiation of dispersed phase instability and consequently change in the surface microhardness (11).
Dental bondings are compounds that, in the restoration process, are applied to the tooth structure before placing the composite. The many features and quality of restoration depends on the procedure and properties of composite bonding to the tooth. The composition of the materials and their properties are determinant factors in the application of dental materials (12).
The eighth-generation bondings are composed of hydrophilic and hydrophobic monomers (13). The hydrophilic groups interact with dental tissue and the hydrophobic group with restorative materials (due to composites’ hydrophobicity). The chemical composition of these bondings includes activators, stabilizers, solvents, and, in some cases, inorganic reinforcement materials (14).
Studies have shown that alcohol-containing mouthwashes can affect the hardness of composite restorations and cause them to soften (15). Given the relationship between food ingredients and surface chemical degradation and composite erosion their application has been restricted (16, 6). Failure to address this problem, the hardness of the composites in the mouth will decrease over time and this will reduce the lifetime of restoration and recurrence of tooth decay (17). Several studies have been conducted to determine the impact of food-simulating liquids on different types of composites. Semi-food liquids such as 25, 50, and 70 percent ethanol and heptane are substances that are being used to simulate the effects of food ingredients on dental composites (5, 8).
In a study by Ghavam and colleagues (6), heptane increased the surface microhardness of Gradia (GC) and P60 (3M ESPE) composites. Torres et al. (9) also showed a significant reduction in the surface microhardness of composites subjected to solutions (e.g., artificial saliva, citric acid, ethanol, heptane), with the largest reduction observed in the heptane group.
The composition of the resin matrix and filler in terms of volume, particle size, distribution, and adhesion to the resin matrix can affect the level of microhardness of a composite (7, 18-20).
Several studies have investigated the effect of organic acids and food liquids on some of the surface properties of methacrylate-based composites such as abrasion, hardness, and surface roughness(21-25). However, the effect of these liquids on composites repaired with universal bonding agents has not been evaluated. This study aimed to determine the effect of food-simulating liquids on the microshear bond strength of composite to composite by universal bondings.
MATERIALS AND METHODS
In this experimental study, Z250 universal composite (3M ESPE, USA) was used (Figure. 1) .80 rectangular cubes were prepared by radiological films with dimensions of 17×17 mm and a height of 15 mm. At the center of each acrylic cube, a hole with a diameter of 6 and a depth of 2 mm was created and filled with the desired composite (Figure 2). Then they were pressed by a glass slide, and without removing the slides, they were exposed to the light (curing light - Dentamerica, Litex 695, Taiwan) for 20 seconds. Then, the glass slide was removed from the surface of the samples and the composites were exposed to the light for another 20 seconds.
To simulate clinical conditions, the samples were subjected to 3400 cycles of Thermocycling procedure in an incubator with a temperature range between 5 and 55 °C .
Samples were divided into 5 groups of 16, including 4 experimental and one control group (immersion in distilled water). The samples in each experimental group were stored in either 2% citric acid, heptane, 75% ethanol, or artificial saliva at 37 °C for 7 days.
After aging process completed the surface of the samples were roughed by Opti Disc (Kerr Co, USA), a universal bonding agent (G-premium bond - GC Corporation, Tokyo, Japan) was applied according to the manufacturer's instructions. In brief, samples were etched with phosphoric acid for 10-15 seconds, then washed and a bonding agent was applied to the samples using micro-brush. Afterward, the surface of the samples was dried for 5 to 10 seconds with gentle air pressure. For polymerization, the samples were exposed to curing light for 20 seconds and a composite cylinder with a diameter of 4 mm and a height of 2 mm was placed on the previous composite and the surface was polished. The samples were exposed to curing light for 20 seconds, and then the matrix was removed from the cylinders.
Then, the samples mounted in acrylic were placed in the Universal Testing Machine (SANTAM STM-20, Iran), and vertical force was applied at the speed of 0.5 mm/min until the separation of the upper composite from the junction point. The maximum force (Newton) was recorded and the bond strength (MPa) was calculated by dividing the obtained force (Newton) to the surface unit area (mm) at the interface of two composites.
Considering the normality of the data distribution by Shapiro-wilk test, the data was analyzed with one-way ANOVA and Bonferroni post hoc test and SPSS software version 25. A significant level of 0.05 was considered.
RESULTS
The mean of band strength (MPa) in the studied experimental groups had a significant difference (P < 0.001) (Table 1. The mean of bond strength in the experimental groups was as follows: artificial saliva with the highest strength (25.53), distilled water (20.24), ethanol (18.04), citric acid (16.24) and heptane with the least strength (9.83) (Figure1).
In a two-by-two comparison of groups, the mean bond strength of samples subjected to heptane was substantially lower compared to all other experimental groups (P < 0.001). The mean bond strength of samples subjected to artificial saliva was significantly higher compared to other experimental groups (P <0.001). There was no significant difference in mean bond strength
between the saliva and control (distilled water) groups (p= 0.136) (Table 2).
DISCUSSION
The findings of this study revealed that artificial saliva has the highest mean bond strength among experimental groups. The bond strength of the composites subjected to distilled water, ethanol, citric acid, and heptane, was reduced respectively. Interestingly, heptane had the greatest effect on reducing the bond strength of the universal bonding agent in repaired composites. Therefore, it can be concluded that artificial saliva has the least and heptane has the greatest effect on the bond strength of the composite. Compared to artificial saliva, the bond strength of the composite in distilled water was lower despite the lack of solutes and a neutral environment. The resin matrix composites can potentially be damaged by organic solutions such as heptane (26). In addition, the degradation of inorganic filler particles plays a role in reducing the mechanical properties of a composite (27).
In a study by Irari et al. (28), the effect of artificial saliva on shear bond strength in aged and fresh composites was investigated. The finding of this study showed that the shear bond strength of aged composite at the repair interface is significantly reduced, which is inconsistent with the results of the present study. This discrepancy could be due to the use of different composites in our study. A study by Sideridou et al. (29), also evaluated the sorption properties of Food simulating liquids by Kalore GC nanohybrid composite. The results indicated that the sorption characteristics of a composite depend on the composite structure and its surrounding fluid, such that, absolute ethanol, artificial saliva, and heptane respectively had the highest to lowest sorption effect on the composite. This finding was inconsistent with the results of our study. Similar to the study by Sideridou et al. (29), we used nano-hybrid composites. However, in our study, the bond strength of the Z250 composite in artificial saliva was substantially higher than ethanol. In the study by Sideridou et al. (29), only the effect of sorption on the composite was investigated while in the present study, the effect of liquid sorption was explored on the bond strength of universal bondings and the composite. Additionally, in the study by Irari et al. (28), a 7th-generation bonding agent was used whereas in our study the 8th-generation bonding agent (universal bondings) was used.
The effect of Food simulating liquids on the hardness and surface roughness of restorations by Z250 hybrid and CM nanohybrid composites was also explored by Kooi et al. (30). In this study, the composites were subjected to normal air, distilled water, 50% ethanol alcohol, and citric acid (0.02 N). The results indicated that except citric acid, all other Food-simulating liquids reduced the bond strength of the composites. In this study, the effect of distilled water has been reported on the smoothness of the composite surface, which is in contrast with our study. In our study, distilled water after artificial saliva preserved the highest bond strength compared to other Food-simulating liquids. In the study by Kooi et al. (30), the hardness and surface roughness of the composites were investigated while in our study the bond strength was explored.
In a study by Yap et al. (19), Food simulating liquids did not affect the surface characteristics of Dyract AP, Spectrum TPH, F2000 but Bis-GMA-based composites (P50, Z100, and Cylox Plus) were susceptible to softening due to exposure to Food simulating liquids. In another study, it has been mentioned that ethanol solution is more effective on softening of the composite surface compared to other Fo-simulating liquids (22).
In another study by Yap et al. (31) the effect of food solvents on the strength of a Filtek supreme nanofilled composite, a type of Ormocer admira (Vocco), compomer (F2000), and Z250 (3M) composite and Ketac molar, a high viscosity glass ionomer, was explored. The findings showed that the strength of these materials was not affected by food solvents. This is inconsistent with the results of our study which was performed on a different type of composite.
CONCLUSION
Artificial saliva had the highest effect on reducing bond strength, followed by distilled water, citric acid and heptane respectively.
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Table 1. Bond strength (MPa) in different experimental groups
Groups | Mean | Sd division | P value |
distilled water | 20.24 | 10.76 | 0.001 |
citric acid | 16.24 | 4.40 | |
artificial saliva | 25.53 | 4.83 | |
ethanol | 18.04 | 4.08 | |
Heptane | 9.83 | 3.65 |
Table 2. Comparison of bond strength (MPa) in different experimental groups
| Distilled water | Citric acid | Artificial saliva | ethanol | heptane |
Distilled water | - | 0.601 | 0.136 | 1.00 | 0.001∗ |
Citric acid | 0.601 | - | 0.001∗ | 1.00 | 0.001∗ |
Artificial saliva | 0.136 | 0.001∗ | - | 0.006∗ | 0.001∗ |
ethanol | 1.00 | 1.00 | 0.006∗ | - | 0.001∗ |
heptane | 0.001∗ | 0.001∗ | 0.001∗ | 0.001∗ | - |
∗ p<0.05
Figure 1. Z250 composite
Figure 2. Prepared samples
Figure 3. Mean bond strength (MPa) in different experimental groups