Journal of Dental Research and Review

ORIGINAL ARTICLE
Year
: 2018  |  Volume : 5  |  Issue : 4  |  Page : 111--115

Effect of artificial aging environment and time on mechanical properties of composite materials


Efe Çetin Yilmaz1, Recep Sadeler2,  
1 Department of Mechanical Engineering, Faculty of Engineering, Kilis 7 Aralık University, Kilis, Turkey
2 Department of Mechanical Engineering, Faculty of Engineering, Ataturk University, Erzurum, Turkey

Correspondence Address:
Efe Çetin Yilmaz
Department of Mechanical Engineering, Faculty of Engineering, Kilis 7 Aralık University, Kilis
Turkey

Abstract

Aim: The purpose of this study was to evaluate the Vicker's hardness and surface roughness of eight different composite materials immersed artificial saliva and distill water. Materials and Methods: Five standardized disc shape specimens (2mm diameter X 2mm height) were prepared from eight composite materials (Grandio, Estelite Flow, Filtek Bulk-fill, Charisma, Clearfil, Ultimate, Quadrant and G-aenial for each artificial aging environment. Specimens were immersed during 7, 90 and 180 days in artificial saliva and distill water at 37 °C respectively. The Vicker's hardness and surface roughness values of the samples were measured after each artificial aging period. Mean values and standard deviations were calculated and statistical analysis was performed using one-way ANOVA. Results: In this study Vicker's hardness and surface roughness values of all samples significantly increased after both in artificial saliva and distill environment 7 days aging period. Conclusion: In this study, suggested the similar to mechanical behavior of the bulk-fill and resin-based composite materials both artificial saliva and distill aging periods. However, in this study no linear relationship was found between filler volume and surface roughness both in artificial saliva and distill aging environment.



How to cite this article:
Yilmaz EÇ, Sadeler R. Effect of artificial aging environment and time on mechanical properties of composite materials.J Dent Res Rev 2018;5:111-115


How to cite this URL:
Yilmaz EÇ, Sadeler R. Effect of artificial aging environment and time on mechanical properties of composite materials. J Dent Res Rev [serial online] 2018 [cited 2019 Feb 16 ];5:111-115
Available from: http://www.jdrr.org/text.asp?2018/5/4/111/250785


Full Text



 Introduction



Recent years, the use of composite materials is increasing in the field of dentistry. In clinical studies that it is known that the long-lasting treatment processes of composite restoration materials depend on the durability, wear resistance, interface integrity, and surface roughness of the composite material.[1] Therefore, surface fillers have been developed to maintain or improve the properties of direct restorative materials.[2] Composite materials generally consist of a polymerizable resin matrix and filler particles chemically bonded with silane coupling agents.[3] Composite materials can be classified nano, micro, bulk-fill, etc., depending on the filler structure. In addition, the differences between these composites in relation to the monomer structure, filler composition and matrix-filler chemistry of the composite materials may explain different mechanical performances and may also determine the behavior of the composites in the mechanical and chemical degradation environment.[4] It has been reported that damage to the composite material in the oral tribology may be caused by matrix and filler structure of the composite material or microcracks caused from environmental mechanical loads, which may reduce the suitable of the composite material surviving on the in vivo study.[5] Dental composite of aging resistance is important in order for it to remain suitable in the mouth environment for a long time. Some properties of dental composite material, such as surface roughness, water absorption, and solubility, are important to estimate the aging resistance in the oral environment.[6] Surface roughness behavior of composite material is an important property. This is because both the esthetic and mechanical properties can be negatively affected from the increase in the surface roughness of the composite material. In the literature, it has been reported that a smooth surface, which composite material, both improve the aesthetic properties of material and reduces plaque retention.[6],[7] The purpose of this study was to evaluate the Vicker's hardness, and surface roughness of eight different composite materials immersed artificial saliva and distill water using four different aging time protocols.

 Materials and Methods



The chemical and mechanical properties of the eight different composite materials tested in this study are shown in [Table 1] (information provided by the manufacturer company). Five standardized disc shape specimens (2 mm diameter × 2 mm height) were prepared from eight composite materials (Grandio, Estelite Flow, Filtek Bulk-fill, Charisma, Clearfil, Ultimate, Quadrant and G-aenial for each artificial aging environment. Composite specimens were immersed during 7, 90, and 180 days in artificial saliva and distill water at 37°C, respectively. [Table 2] shows the chemical components of the saliva solution used in this study.[8] The Vicker's hardness and surface roughness values of the samples were measured using 2D and 3D profilometer after each artificial aging period. In addition to a random specimen was selected from each test group and scanning electron microscope images were taken for the analysis of microstructure degradation.{Table 1}{Table 2}

Determination of surface roughness and Vicker's hardness

In this study, the surface roughness (Ra) of the composite specimens was measured use with 3D noncontact profilometer after each artificial aging protocols (Bruker-Contour GT 3D). A load of 0.5 kg was applied for 60 s using a pyramidal mold; the depth of the measure represents the hardness of the specimen. It is known, Vicker's Hardness is proportional to the applied force and part of the measurement surface which is part of a pyramid with a square base. The pyramid and impression were thought to have the same surface angles. As a result of the Vicker's hardness of the composite materials was calculated using the following formula.

VH = (0.102 × F × sin136°/2)/d2

where F represents the force (9.81 m/s 2 × mass in kg) and d represents the diagonal of the pyramid basement.

 Results



[Figure 1] shows the surface roughness of composite materials tested in this study in distill water and artificial saliva ambient at 37°C temperature, respectively. When the surface roughness values of composite materials were examined, it will be seen that surface roughness values of all composite materials increased after 7 days of aging [Figure 2] and three shows the Vicker's hardness of composite materials in this study in distill water and artificial saliva ambient at 37°C temperature, respectively. When [Figure 2] and [Figure 3] are examined, it will be seen that all composite materials show a significant increase in hardness values especially after 7 days of artificial aging immersed distill water. The rate of increase was the highest in the Filtek Bulk-Fill composite material and the least increase was in the Charisma composite material. However, the 90 and 180 days artificial aging times generally did not change the hardness value of the composite materials. [Figure 4] shows the example of the mechanism of degradation of the artificial aging process in the microstructure of the composite material.{Figure 1}{Figure 2}{Figure 3}{Figure 4}

 Discussion



The particle size of the composite restorative material produced a chemical composition containing two different particles. These composite materials are referred to as micro or nano-hybrid resin composites depending on the micro-or nano-particle size and content.[9],[10] Commercially, it is often difficult to distinguish micro and nanostructural derivatives of composite restorative materials because these composite materials are very similar in structure to both microstructure and mechanical behavior.[11] In this study, distill water and artificial saliva medium at 37°C temperature were used to simulate the in vivo oral aging environment. Many studies in the literature have chosen these environments for artificial aging.[3],[12],[13] Examination of [Figure 2] and [Figure 3] reveals that composite materials behave similar to the aging process in distill water and artificial saliva medium. This can be explained by the fact that the aging environment on the hardness and surface roughness of the materials tested in this study is not significant. In the literature, Hahnel et al. reported that Filtek Supreme, Filtek Silorane, Exp Orcomer, CeramX, and Quixfil composite materials exhibited similar behaviors in distill water and artificial saliva solution aging media.[3] In this study, it was seen that composite materials exhibit surface roughness behavior due to their different types of organic matrix and filler structure during the aging process. Especially, ultimate composite material has higher surface roughness value than other composite materials in all aging periods. As a result, the organic matrix structure of ultimate composite material was concluded as being more susceptible to the mechanism of hydrolytic degradation of triethylene glycol dimethacrylate (TEGDMA). Dental composites having a tri-ethylene glycol dimethacrylate or TEGDMA structure as a matrix component may be more susceptible to matrix degradation.[14],[15] Due to the composite material has this structure, which allows the water to more easily penetrate to the matrix structure.[14]

Composite materials tested in this study showed similar hardness behavior in both distill water and artificial saliva environments irrespective of period process. The highest hardness value was measured in Grandio composite material while the lowest hardness value was measured in Filtek Bulk-Fill composite material immersed all artificial aging protocols. It is possible to say that the monomer structure contained in Grandio composite material is effective. In this study, it has been observed that all of the composite materials tested had significant increases in hardness values after 7 days of artificial aging period. Water absorption has an effect on the mechanical properties of dental composite materials. It has been observed that this stored period affects the mechanical properties of the material such as wear resistance, hardness, and tensile strength. Previous study reported that the specimens is significantly increased three-body wear resistance and hardness in the 7 days stored distil water compared to the after 24 h exposure to distil water only.[14],[16],[17] According to Chadwick et al.[18] no significant differences in wear after 1 week and 1 year of water storage of composite resins was found.[18] Therefore, it can be assumed that the composite material is completely saturated with 1 week distill water stored.

 Conclusion



Within the limitation of the present laboratory study, the following conclusion can be drawn:

In this study, Vicker's hardness and surface roughness values of all samples significantly increased after both in artificial saliva and distill environment 7 days aging periodThis study suggested the similar to mechanical behavior of the bulk-fill and resin-based composite materials both artificial saliva and distill aging periods. However, in this study, no linear relationship was found between filler volume and surface roughness both in artificial saliva and distill aging environmentAmong the composite materials tested in this study, bulk-fill and resin-based composite materials have similar mechanical behavior after all artificial aging medium and time protocol process.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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