Evaluation of bond strength of cinnamon essential oil-modified composite resin to dentin: an in vitro study

Introduction
In phytodentistry, essential oils are renowned for their antimicrobial and anticariogenic proper­ties, and can be used in modifying and enhancing the antimicrobial activity of composite resins (CR) without influencing mechanical properties. Therefore, researchers should conduct studies investigating the effect of these natural alternatives on the mechanical properties of CR.

Objectives
This study aimed to investigate the shear bond strength of cinnamon oil-modified CR to dentin.

Material and methods
Eighty extracted molars with exposed dentin were embedded in acrylic molds, and divided into four groups according to oil concentration (each group, n = 20): group 1 (negative control, no oil), group 2 concentration (1 μl/2 g CR), group 3 concentration (2 μl/2 g CR), and group 4 concentration (5 μl/2 g CR). After the mixing procedure, plastic molds were fixed, and the flowable composite was applied and cured. A shear bond strength test (SBS) was performed to evaluate the bond strength.

Results
The mean SBS value for group 4 was 19.81 ± 2.47, which was significantly lower than that of group 1 with a mean of 22.07 ± 2.95 (p = 0.027). In contrast, the mean SBS values for group 2 (21.63 ± 2.45) and group 3 (21.78 ± 2.23) were not significantly lower than that of group 1 (p > 0.05).

Conclusions
Within the limitations of this study, CR modified with less than 5 μl cinnamon oil demonstrated acceptable shear bond strength, suggesting potential for use in restorative applications. Essential oils appear to be promising agents to replace synthetic compounds in contemporary dentistry, but further studies are required.