ABSTRACT Objective The aim of this study was to evaluate the clinical performance of one microhybrid and two bulk-fill resin composites in Class II cavities for up to two years.

Materials and methods In total, 75 Class II restorations were made in 25 patients, using three restorative materials: two nanohybrid bulk-fill resin composites, Sonic Fill (SF) and x-tra fil (XF), and a microhybrid composite, Filtek Z-250 (FZ). The restorations were blindly evaluated by two examiners at baseline and at 6, 12, and 24 months, using U.S. Public Health Service (USPHS) criteria. The restoration groups for each category were compared using the Pearson chi-square test, and the Cochran Q-test was used to compare the changes across different time points within each restorative material (p <0.05).

Inclusion Criteria:

• Patient in need of restoration of caries lesion (diagnosed with bitewing radiograph and clinical examination);
• teeth in need of restoration to be first or second molars or permanent premolars;
• at least three Class II restorations required in each patient and the number of restorations of each material to be equal in each patient;
• the antagonist and adjacent tooth in contact;
• pulp vitalized and free of painful symptoms; teeth involved not to have undergone direct pulp capping;
• no history of hypersensitivity in the teeth to be restored;
• permanent dentition;
• good oral health and absence of periodontal disease;
• patients not to have suffered from systemic diseases or allergies;
• absence of deleterious habits, xerostomia, and bruxism.

Exclusion Criteria:

• Fewer than 20 teeth;
• history of existing tooth sensitivity;
• known allergy to resin-based materials or any of the other materials used in this study;
• pregnancy or breastfeeding;
• chronic use of anti-inflammatory drugs, analgesic, and/or psychotropic drugs;
• non-vital teeth;
• abutment teeth for fixed or removable prostheses.

one year