## 4 Discussion  
The hypothesis of the study was rejected based on the obtained data. Significant differences were found among all composites statistically in terms of bottom/top microhardness, FT-IR, and DSC values. The characterization of restorative materials is crucial for their clinical performance and longevity. In this study, the microhardness, degree of conversion (DSC), and Fourier-transform infrared spectroscopy (FT-IR) analyses were conducted to evaluate the properties of Neo Spectra, Omnichroma, and Myra restorative materials. The term \"hardness\" denotes the resistance of a material's surface to penetration and abrasion, as well as its ability to withstand scratches. Various tests, such as Vickers, Knoop, Rockwell, Brinell, or Barcol, are employed to determine the hardness of restorative materials [22]. In the dental literature, the Vickers and Knoop tests are the most commonly used, with the Vickers test being a non-destructive method. In the Vickers test, the area of the shape formed by the diamond indenter on the surface is digitally calculated to measure the materials' microhardness values. Previous studies have shown that microhardness tests have been conducted using different loads and durations (holding times) [21; 23; 24]. Following the ISO standard (ISO 4049) established in this field and considering the available literature, microhardness values were measured in the present study using a Vickers test apparatus, with the indenter applying a force of 300 g for 15 s [21; 25]. The top and bottom surface microhardness values for Omnichroma and Neo Spectra were higher compared to Myra. It has been reported that Myra may contain nanoparticles in its structure, hence exhibiting slightly better microhardness values compared to its counterparts such as Pergamon and Parion [21]. According to the literature, Neo Spectra has demonstrated average performance compared to other nanofluybrids [26]. The presence of spherical pre-polymerized fillers in Neo Spectra and silico-zircon fillers in Omnichroma may have contributed to the better performance of Neo Spectra and Omnichroma compared to Myra, especially in terms of top surface microhardness values. According to the manufacturer, Neo Spectra features a unique patented technology called SphereTEC, which includes a  
Figure 13: SEM image of Omnichroma. high filler content [27]. Its advanced micro-granular structure has been proven to exhibit superior performance in various physical and mechanical tests [28]. Due to its recent introduction, there are limited publications available in the literature regarding Myra [21]. While it does exhibit statistically significantly lower microhardness values compared to the other two composite materials in this study, it is noteworthy that the values are relatively close. Microhardness values provide insights into the material's resistance to indentation and wear, which are critical for its durability in clinical applications. The highest microhardness values observed for Neo Spectra on both top and bottom surfaces suggest its superior mechanical properties compared to Myra. The finding of no significant difference between Neo Spectra and Omnichroma on the bottom surface indicates comparable performance in load-bearing regions. Resin-based restorative materials can be subjected to material content analysis at various depths and layers, either destructively or non-destructively, using a range of spectroscopic techniques including FT-IR, Raman, ultraviolet light, X-ray, or DSC [29]. Among these methods, FT-IR is commonly favored in the dental literature for assessing DC values. FT-IR analysis allows for the evaluation of the degree of conversion of monomers into polymer chains during polymerization, reflecting the material's curing efficiency [29; 30]. Employing the spectroscopic approach of FT-IR allows for the non-destructive examination of dental materials with minimal material consumption [31].