Erciyes University Clinical Research Ethics Committee

Composite resins have been widely used in the last years to restore teeth due to increases in patients' esthetic expectations. Therefore optical and mechanical properties of composite resins were being developed day by day. Composite resin restorations have the main advantages such as conservative cavity preparation, preserving healthy dental tissue, and strengthening the remaining tooth structure. Furthermore, according to clinical studies, high clinical performance and good longevity have been reported. Traditionally, the composite resins are placed in increments of 2 mm that are cured separately (incremental technique. The incremental technique provides sufficient light penetration and monomer conversion. However, there are many disadvantages to the incremental technique. For instance, bonding failure, blood, or saliva contamination of between layers, the difficulty of application in limited access in small cavities, and to be time-consuming. Because of these, manufacturers have presented a "bulk-fill composites", which could be polymerized in a single layer up to 4-5 mm thick to the market. Bulk-fill composites can be described as composites that are sufficiently polymerizable in a single layer up to 4 mm thick. Bulk-fill composites that were introduced in recent years can be manipulated faster and more convenient in the cavity compared to conventional hybrid composites. In addition, these materials present good mechanical properties such as marginal adaptation, sealing properties, fracture strength, wear-resistance, and long-term clinical success. Clinical studies are required to clearly describe the clinical behavior of the materials. Although there have been many in vitro studies about bulk-fill composite in the literature, the number of clinical trials is insufficient. Therefore, the aim of this study was to evaluate the clinical performance of bulk-fill composite about placement technique (bulk-filling and incremental techniques) in Class II carious lesions using the criteria of the World Dental Federation (FDI) and the United States Public Health Service (USPHS)