A comparison of the effect of chlorhexidine and collagen cross-linking agent (oak extract) used for different times on composite-dentine micro tensile bond strength

Introduction
he chief goal of restorative dentistry is to provide resin-dentin bond strength. Several materials have been proposed to strengthen the bond. External cross-link factors are a group of materials that improve the collagenic cross-links. Proanthocyanidins are a class of polyphenols found in a variety of plants including oak. Aim of the research: To compare the effect of chlorhexidine and collagen cross-linking agent (oak extract) used for different times on composite-dentine micro tensile.

Material and methods
In the in vitro study, oak fruit was collected and used to make 33% oak extract. After that, 14 molar teeth were used, enamel was removed, and dentin was exposed. Then, 5 different protocols were used to prepare the teeth: 1. Using oak extract for 90 s, 2. Using oak extract for 180 s, 3. Using oak extract and chlorhexidine for 90 s, 4. Using oak extract and chlorhexidine for 180 s, and 5. Control group. Finally, the bonding strength was compared between the groups.

Results
The maximum and minimum of bond strength were found in control and group 1 (24.86 vs. 19.49), respectively. All 4 intervention groups showed significant lower bonding strength than did the controls. The level of significance was lower than 0.0001. The least mean differences with controls (4.75) were seen in group 4.

Conclusions
Our findings indicated that treatment with oak extract led to a decrease of the resin-dentin bond strength.