In vitro evaluation of the fracture strength and microleakage properties of young permanent teeth restored using composite resin with different fiber content and different application methods

In this study, it was aimed to compare the tubercle fracture strength and microleakage values under in vitro conditions of restorations made with and without the use of polyethylene fiber along with nanohybrid composite resin material applied with the incremental technique, and restorations made with a short fiber reinforced composite resin applied with the bulk fill technique. In this study, it was aimed to compare the tubercle fracture toughness and microleakage values under in vitro conditions of restorations made with and without the use of polyethylene fiber along with nanohybrid composite resin material applied with the incremental technique, and restorations made with a short fiber reinforced composite applied with the bulk fill technique. 60 premolar teeth were used in the study. After the surfaces of the teeth were cleaned, MOD cavities were prepared. Following this, the teeth were divided into 3 groups. Group GP, G-Aenial Posterior (Control Group); Group EXP, EverX Posterior; Group R was restored using different techniques with Ribbond and G-Aenial Posterior restorative materials. After the fracture strength samples were prepared, force was applied to the samples with a universal testing device (Shimadzu, Tokyo, Japan). After the microleakage samples were kept in 2% methylene blue solution for 24 hours, they were divided into two equal parts in the mesio-distal direction with a low-speed precision cutting device (Buehler Precision Saw, Düsseldorf, Germany) and a diamond cutting disc (Isomet-Buehler, Düsseldorf, Germany) under water cooling and were scored. Analysis of the data was carried out statistically. As a result of the findings obtained from the study, it was seen that the restorative material and technique used had different effects on the cuspid fracture strength and microleakage of MOD cavity teeth. When the groups in which the fracture resistance was examined were compared, it was determined that the EverX Posterior group showed the highest fracture resistance. When the fracture types were examined, no statistically significant difference was found between the groups in terms of restorability. When microleakage values are examined; no significant difference was found between groups in occlusal microleakage classification. In the gingival microleakage classification, it was determined that the highest microleakage was in the G-Aenial Posterior group and the lowest microleakage was in the Ribbond group. As a result of these findings, according to the results of laboratory tests of composite resin restorations made using fiber in the restorative treatment of premolar teeth with extensive material loss, it is seen that the use of fibers in the restorations of MOD cavities provides an advantage to composite restorations when evaluated in terms of cuspid fracture durability, fracture types and microleakage. It is clear that such studies, in which the success of these materials are evaluated through in vitro tests, will make meaningful contributions to the literature on the subject. However, it was concluded that longer-term clinical studies are needed to evaluate long-term success. Keywords: Fibre, Fracture Strength, Microleakage