Matrix metalloproteinases (MMPs); activated by the application of adhesive systems on dentin cause degradation of the collagen proteins and loss of bond strength in adhesive restorations. Caffeic acid phenethyl ester (CAPE) showed inhibitory activities on dentinal MMPs. It is hypothesised that dentin pretreatment with CAPE, as an MMP inhibitor, would be beneficial for the bonding of resin material and tooth substrate over the course of time. This study evaluated the effect of 5 % CAPE pretreatment on the microtensile bond strength of a nanohybrid resin restoration applied with total-etch or self-etch adhesive systems on 10 patients (12-18 yrs). Two standard cavities (3 x 3 x 4 mm) prepared on the occlusal surfaces of one of the two premolar teeth in each patient were randomly assigned into four treatment groups (n=10); 5% CAPE pretreatment and total-etch adhesive (TC), Total-etch adhesive (control) (T), 5% CAPE pretreatment and self-etch adhesive (SC), Self-etch adhesive (control) (S) followed by restoration and 3 months of intra-oral functioning. After teeth extraction, the specimens were stored in distilled water+thymol solution at 4°C to inhibit microbial growth and used in one week period. Dentin-composite sticks were obtained from each restoration for µTBS tests and scanning electron microscopy (SEM) evaluation. Failure mode analysis was performed microscopically. Data were analysed statistically using Repeated Measure ANOVA (p < 0.05). Dentin pretreatment with CAPE solution (5%) for 60 seconds significantly increased the composite resin restorations' bond strengths to dentin applied with either total-etch or self-etch adhesive system. Thus it can be used as an MMP inhibitor prior to the the resin restorations. However further long term clinical studies are needed to support the use of CAPE pretreatment along with self-etch and total-etch adhesive systems.