The aim of this study was to investigate the clinical effectiveness of direct resin composite restorations placed with different placement techniques (incremental or bulk) and with different flowable linings (conventional or bulk-fill flowable) used in open-sandwich technique, in endodontically treated Class II cavities (mesio-occlusal or disto-occlusal), in a randomized controlled comparison.

Forty-seven pairs Class II (mesio-occlusal or disto-occlusal) composite restorations were placed in 37 patients. In all cavities, Adper Single Bond 2 was used. In one of the cavities of each pair, a conventional flowable composite, Aelite Flo, was applied in approximately 2mm thick, and the remaining cavity was restored incrementally with GrandioSO. In the second cavity, a bulk-fill flowable composite, x-tra base, was applied in approximately 4 mm thick in bulk increments and the remaining 2mm occlusal part of the cavity was restored with GrandioSO. All cavities were restored with open-sandwich technique by the same operator. At baseline and after 6-month, 1-, 2- and 3-year follow-up visits, restorations were evaluated by Modified USPHS criteria.

Inclusion Criteria:

• Permanent premolars and molars without any restorations were included in the study. Every tooth included in the study had neighboring teeth and were in occlusion to antagonistic teeth.

Exclusion Criteria:

• Patients were excluded who needed indirect restorations due to significant loss of tooth structure, known allergies to product ingredients, had poor oral hygiene and a history of bruxism.