## 1 Introduction  
Maxillofacial prosthetics is a branch of prosthodnotics that focuses on treating and managing maxillofacial abnormalities [1]. Extraoral maxillofacial prostheses are frequently utilized to restore facial components that have been lost due to congenital defects, trauma, or surgical removal. These prostheses serve to restore both functional and aesthetic aspects, thereby greatly enhancing the overall quality of life for patients [1; 2; 3; 4; 5; 6; 7]. Silicone, also known as polydimethylsiloxane, is frequently utilized in the fabrication of the extraoral sections of the maxillofacial prosthesis. For more than half a century, it has been utilized in the fabrication of facial prosthetics for patients because of its longevity, resistance, biocompatibility, and ease of manipulation [4; 8; 9; 10; 11; 12; 13; 14; 15]. In spite of this, there are specific worries regarding the durability of silicone prostheses, in addition to the maintenance that is required for them [16; 17; 18; 19]. The color stability of prostheses made with silicone elastomer is only guaranteed for a period of six to twelve months [20; 21]. The discoloration of the silicone elastomers is the primary factor that leads to the need for the replacement of facial prostheses [7; 19; 22; 23; 24]. The color change of the facial prosthesis is brought on by a combination of factors, including exposure to ultraviolet (UV) radiation, air pollution, pigments that are naturally present in the material, and the use of cleaning solvents [7; 25; 26; 27; 28]. Even though ultraviolet light only makes up a very small percentage of the total radiation that is emitted by the sun, it has a significant influence on the facial prostheses' ability to maintain their color. All wavelengths that fall between 100 and 400 nanometers are included in the definition of ultraviolet radiation. To simulate the conditions of the natural environment, a large number of researchers have constructed artificial weathering or aging chambers. These chambers are helpful for determining the overall deterioration of materials and have been widely used [25; 27; 29]. Polymers, such as silicone materials, have the ability to absorb the energy of UV photons, which can lead to the breakdown of polymeric chains and the production of new radicals that can cause additional damage to polymer networks. Polymers also have the ability to produce new radicals that can cause additional damage to polymer networks. As a result of this process, the surface might develop cracks, it might lose its shine; it might turn a different color; or it might fade. In addition, there is a possibility that the material's molecular weight will decrease, as well as its elasticity [30]. In the process of defining color notations, the CIE-Lab system is frequently applied. This system was developed by the Commission Internationale de L'Eclairage (CIE). \(\Delta\)E* is the notation that is used in this system to refer to the overall color difference caused by all changes in color coordinates. It has been stated that the perceptibility threshold for silicone maxillofacial prosthetics with light skin tone is \(\Delta\)E* of 1.1, while the acceptability threshold is \(\Delta\)E* of 3.0 [31; 32]. Nano-oxide particles have been incorporated into various polymers so that they can provide protection against ultraviolet (UV) rays and also function as a strengthening agent. The strengthening mechanism of the particles can be traced back to an increasing chemical reactivity of the particles themselves. The increased chemical reactivity exhibited by these particles confers upon them the capacity to engage in reactions with polymer chains, thereby imparting stabilization to the chains. There is a hypothesis suggesting that the minuscule dimensions of nano-oxides play a role in enhancing their ability to absorb ultraviolet (UV) light and facilitate the scattering of UV photons. As a consequence, this leads to a reduction in the overall absorption of UV energy by the polymer network.