Comparative Evaluation of the Effect of Different Oxygen Layer Inhibitors on the Thickness of the Oxygen-Inhibited Layer on Nanohybrid Resin Composite and Its Surface Microhardness: An In Vitro Study.

Background This study aimed to evaluate and compare the effect of oxygen layer inhibitors such as DeOx (Ultradent Products, Inc.), Mylar strip (Unident Denmed), and post-polymerization polishing (Shofu Super-Snap Rainbow Technique Kit) on the thickness of the oxygen-inhibited layer (OIL) on nanohybrid resin composite (Ivoclar Vivadent Tetric N-Ceram Syringe Refill Universal Composite Resin) and its microhardness. Methodology A total of 40 nanohybrid resin composite samples were shaped as discs of 6 mm diameter and 4 mm thickness. Oxygen layer inhibitors were divided into Group 1 (DeOx, n = 10), Group 2 (Mylar strip, n = 10), Group 3 (post-polymerization polishing, n = 10), and Group 4 (Control, n = 10). The samples were polymerized for 20 seconds with a light-emitting diode curing unit. The samples were then measured for OIL thickness at 50× magnification using a three-dimensional optical profilometer. Furthermore, each group of samples was evaluated for surface microhardness using an electronic Vickers hardness tester applying a 100 gf load for 10 seconds on the surface at different equidistant points and maintaining a minimum distance of 1 mm adjacent to the margins of the sample. The diagonal length of each notch was measured directly using a graduated ocular lens at 40× magnification. Data were analyzed using one-way analysis of variance, and Tukey's post hoc test was applied for multiple pairwise comparisons. A p-value of less than 0.05 was considered statistically significant. Results The highest OIL film thickness was seen in the Control group (283.35 μm), followed by post-polymerization polishing (79.02 μm), Mylar strip (41.60 μm), and DeOx (23.09 μm). The DeOx group (86.48 VHN) demonstrated the highest mean microhardness values, followed by Mylar strip (78.36 VHN), post-polymerization polishing (62.88 VHN), and Control (51.64 VHN). These differences in values were statistically significant. Conclusions OIL thickness and surface microhardness were significantly affected by the application of DeOx, Mylar strip, and post-polymerization polishing. In this study, the application of DeOx resulted in reduced thickness of OIL and increased surface microhardness of the nanohybrid resin composite, followed by Mylar strip and post-polymerization polishing.