Nowadays, most composite resins require the use of an adhesive material prior to application. For this purpose, etch & rinse (ER) and self-etch (SE) systems have been used for many years. While many in-vitro studies have been conducted in the literature comparing three adhesive systems, the number of clinical studies is less and inadequate. Therefore, the aim of this study was to investigate the effect of 3 different adhesive systems commonly used in clinics on the success of class I composite restorations using the criteria of the World Dental Federation (FDI) and the United States Public Health Service (USPHS).

Nowadays, most composite resins require the use of an adhesive material prior to application. For this purpose, etch & rinse (ER) and self-etch (SE) systems have been used for many years. Compared to SE systems, which are simplified and very easy to use, requiring less technical precision, traditional ER systems are still very popular and preferred by dentists. However, current researchers indicate that ER systems are more effective on enamel than dentin and that this effect is better than SE systems. SE systems are approaches in which the acid application and washing step are eliminated clinically and the possibility of making mistakes during the application and manipulation is reduced. An important advantage of these systems is that demineralization and resin infiltration occurs at the same time. Clinically, the application times are shorter than traditional systems. Two-steps SE systems have been used for a long time. In this system, the need for a separate acidic primer application has needed clinicians reason to search for single-steps bonding agents. And, in recent years, single-step SE systems also called "all in one", have been developed that include all steps of pickling, primer application, and adhesive agent application. However, there are studies showing that these systems do not perform as well as two-step SE systems. While many in-vitro studies have been conducted in the literature comparing three adhesive systems, the number of clinical studies is less and inadequate. Therefore, the aim of this study was to investigate the effect of 3 different adhesive systems commonly used in clinics on the success of class I composite restorations using the criteria of the World Dental Federation (FDI) and the United States Public Health Service (USPHS).

Inclusion Criteria:

• At least 3 Class-I caries lesions
• Good health
• Acceptable level of oral hygiene

Exclusion Criteria:

• Did not have four caries lesions at least
• Did not have Class-II caries lesions
• Deep caries reaching the pulp
• The patients are not 18-22 years old
• Bruxism
• Periodontal disease
• Refused to participate