The aim of the present study was to evaluate the effect of caffeic acid phenethyl ester (CAPE) pretreatment used as matrix metalloproteinase (MMP) inhibitor on microtensile bond strength (µTBS) of nanohybrid resin restorations applied with total-etch or self-etch adhesive systems. A total of 10 patients aged between 12 and 18 years old (4 males, 6 females, mean age:15) received 40 composite restorations. The patients who had contralateral pairs of caries-free premolars which were planned to be extracted for orthodontic treatment were enrolled in the study. This study was performed with a protocol approved by the Ethical Committee for Clinical Studies, Faculty of Medicine, University of Ege, Izmir, Turkey (04.10.2012; no:12-8/6). The treatments were performed after the informed consents were received both from the parents and the patients. Included teeth were in function and no anomalies were found neither in teeth nor in occlusion. Two standard cavities (3 x 3 x 4 mm) with continuous enamel cavosurface margins were prepared on the occlusal surfaces of each premolar tooth.Totally four cavities in each patient were randomly assigned into four treatment groups (n=10); Group TC: CAPE and total-etch adhesive (Syntac; Ivoclar Vivadent AG), Group T: Total-etch adhesive (control), Group SC: CAPE and self-etch adhesive (AdheSE; Ivoclar Vivadent AG), Group S: Self-etch adhesive (control). All cavities were restored incrementally with a nano-filled hybrid composite resin (Tetric-N-Ceram, Ivoclar Vivadent AG) in which polymerization in each layer was performed for 40 seconds with a light-curing unit (BluePhase Ivoclar Vivadent AG) exceeding an energy output of 500mw/sec.