# Surface Gloss, Radiopacity and Shear Bond Strength of Contemporary Universal Composite Resins
###### Abstract  
The surface gloss, radiopacity and enamel/dentin shear bond strengths (SBS)s of five commercially available contemporary universal composite resins (CRs) were examined. The tested universal CRs were as follows: G-aenial A'CHORD (GA), Charisma Diamond (CD), Neo SpectraTMST(NS), Filek(F) and Estelite Asteria(EA). Twelve cylindrical specimens per group were fabricated and gloss measurements were performed using a gloss meter after polishing and darkening. Five specimens of each group were radiographed using a CMOS sensor alongside an aluminum stepwedge, human enamel and dentin. The mean gray values were measured with a computer program. A total of 120 bonded human enamel and dentin specimens were subjected to SBS test. To analyze surface gloss, radiopacity and SBS we used [PERSON], Wilcoxon signed rank, Welch tests and one-way ANOVA. [PERSON], [PERSON]'s HSD tests, and [PERSON]'s multiple comparisons were used for multiple comparisons (\(p<0.05\)). In terms of gloss units of the materials after polishing and darkening, the highest surface gloss was achieved with GA, followed by NS, F, CD and EA (\(p<0.001\)). All the tested CRs showed significantly higher radiopacity values in comparison with dentin (\(p<0.05\)). CD and NS presented higher radiopacity values, while other CRs were, in decreasing order; F, GA and EA (\(p<0.001\)). The SBS ranking varied for enamel and dentin, and the adhesive failure was detected at a higher rate. Commercially available contemporary universal CRs display different surface gloss, radiopacity and SBS properties.  
universal composite resins; surface properties; radiology; shear bond strength; conservative and dentistry +
Footnote †: journal: Applied Sciences  
term [6]. The radiopacity of CR is also important for radiographic diagnosis, as materials with sufficient radiopacity provide an opportunity to diagnose recurrent dental caries [7].  
Aesthetic, mechanical properties and surface characteristics of new generation universal CRs are still under investigation [8; 9]. Among the esthetic factors, the surface gloss is of great importance. This property is often related to deterioration or wear of materials and leads to unsuitable optical properties of restorations and the need for re-polishing, repair or restoration replacement. A recent study evaluated the surface gloss of some universal CRs and reported changes in the surface gloss following thermal cycles [10]. [PERSON] et al. [11] also investigated the surface roughness, microhardness, color change, and translucency of universal nanohybrid CRs and stated that mechanical and optical properties of universal CRs with different compositions showed variations.  
Since the masticatory process is more of a shearing phenomenon, shear bond strength indicates the adhesive strength of the restorative material at the tooth-restoration interface. The increasing demand for simplified universal adhesives has led to many in vitro/in vivo studies [12; 13; 14]. Reviews about universal adhesives have suggested that bond strength may vary according to tissue and material [15; 16], though manufacturers often claim, as part of their marketing strategies, that using their composites with their own adhesives will result in a better performance.  
Currently, a small number of new universal CRs are available on the market promising clinicians to combine advanced features in a syringe with the claim of long-lasting gloss and to optimize the radiographic follow-up with their radiopacities over time. On the other hand, there have been very few studies that evaluate multiple different properties of contemporary universal resin composites and that shed light on clinicians from different perspectives. Therefore, the aim of this in vitro study was to evaluate and compare the aesthetic, radiographic and bonding properties of five commercially available contemporary universal CRs. The null hypothesis stated that there would be no significant differences among the tested CRs in terms of (1) surface gloss, (2) radiopacity, and (3) SBS to enamel and dentin.