Comparison of aging-dependent microhardness of anterior region composite resins

Aim: The aim is to evaluate in vitro the surface hardness values of universal restorative materials used in the anterior region when exposed to acid and artificial saliva using two different polishing techniques. Materials and Methods: In our study, 2 different polishing methods (Shofu One Gloss and EVE Diacomp Plus) were applied to 5 different restorative materials (Essentia Universal Shade-GC, Omnichroma-Tokuyama, Charisma Diamond One-Kulzer, ZenChroma-President Dental and Essentia HiFlo-GC). Afterwards, the samples were exposed to 3 different aging methods (artificial saliva, orange juice and orange juice-artificial saliva). A total of 240 samples were prepared using molds of 8 mm diameter and 2 mm thickness to make the composite samples (n = 8). The samples were divided into subgroups according to polishing and aging methods. The restorative materials were placed in a Teflon mold and polymerized. After Vicker's hardness measurements (Matsuzawa® MHT2, High Quality Microhardness Tester, Matsuzawa SEIKI Co; Ltd, Tokyo, Japan) were made on the samples before aging, they were kept in artificial saliva, orange juice and orange juice-artificial saliva for 24 hours for aging. After aging, Vicker's hardness measurements were taken again. The upper surfaces of the samples were analyzed by SEM (JEOL JSM 7001F, Japan) before and after aging. Statistical analyzes of the data were performed using the SPSS v.19 package program (IBM SPSS Statistics for Windows, Version 27.0. Armonk, NY: IBM Corp, USA). Results: When the initial hardness values of the composites were compared, a statistically significant difference was observed. The highest initial hardness value was observed in Charisma Diamond One (89.578), while the lowest was observed in Essentia HiFlo (54.830) (p<0.05). When the initial and Day 1 hardness differences of all composites were compared, no statistically significant difference was observed. The maximum decrease in hardness value after aging; It was observed by keeping Zenchroma in orange juice after EVE Diacomp Plus polishing application (-2.82±1.51). Minimum decrease in hardness values after aging; It was observed in the artificial saliva + orange juice cycle after EVE Diacomp Plus polishing application to Omnichroma (-0.64±0.84) (p>0.05). Conclusion: When composite resin restorations were kept in liquids with different pH at certain rates, they were affected by these liquids at different rates. It has been noted that there are changes in the surface hardness values of resin-based restorative materials due to the effects of acidic drinks and artificial saliva. Except for a few of the composites used in the study, the hardness values after aging showed statistically lower results than the hardness values before aging. Key Words: Composite resin, Vickers, aging, polishing systems, microhardness.