Universal adhesive solutions have just entered the market, allowing dentists to choose an adhesive strategy based on the needs of patients and clinical situations. Theses adhesives contain a primer/adhesive resin mix in a single bottle for multi-mode etch-and-rinse or self-etch applications. The aim of this study was to evaluate the clinical performance of composite resins with diffent adesive agents on Class II cavities.

This study was a double-blind (evaluator and patient) randomized controlled clinical study with six study groups with an equal allocation. Two composite materials with two universal and one two-step self-etch adhesives were compared in Class II restorations.

The treated patients were called back for controls after one week, six months, and eighteen months. Restorations were evaluated clinically according to modified FDI criteria. In terms of esthetic property, marginal discoloration; in terms of function properties, fracture and retention, and marginal adaptation; in terms of the biological characteristics, post-operative sensitivity, and secondary caries criteria were examined.

Clinical evaluation was performed by two qualified clinicians. Bite-wing radiographs were taken from the patients who were called for controls at 6-moth and 18-month to evaluate the formation of secondary caries.

Differences between adhesives at each time period were evaluated using Fisher's Exact test. The effect of time on restorations was evaluated using the Friedman test (p < 0.05).

Inclusion Criteria:

• Individuals without systemic disease
• Individuals with good oral hygiene
• Must be a minimum of one carious defect
• Must be at least 18 years old
• Must have vital teeth in antagonist and proximal contact.

Exclusion Criteria:

• Pregnant or breastfeeding women
• Receiving orthodontic treatment
• Bruxism habit
• Direct or indirect pulp coverage
• Allergy to resin-based products

Teeth with primary caries, including at least one-third of the dentin (MO or DO), were included in the study.