**Core Concept**
Zinc oxide eugenol (ZOE) cement is a widely used dental restorative material that combines the properties of zinc oxide, a filler, with eugenol, a solvent and an antiseptic. The addition of synthetic resins to ZOE cement aims to improve its mechanical properties and biocompatibility.

**Why the Correct Answer is Right**
The incorporation of synthetic resins into ZOE cement enhances its dimensional stability, strength, and resistance to wear and tear. This is achieved through the formation of a polymer matrix that binds the zinc oxide particles together, thereby improving the cement's mechanical properties. The resins also reduce the solubility of the cement in saliva and other oral fluids, making it more durable and long-lasting.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the addition of synthetic resins to ZOE cement does not primarily aim to reduce its setting time. While the resins may influence the setting reaction, their primary purpose is to improve the cement's mechanical properties.

**Option B:** This option is incorrect because the incorporation of synthetic resins into ZOE cement does not primarily aim to increase its toxicity. In fact, the resins are designed to improve the cement's biocompatibility and reduce its potential for adverse reactions.

**Option C:** This option is incorrect because the addition of synthetic resins to ZOE cement does not primarily aim to reduce its antibacterial properties. While the resins may influence the cement's antibacterial activity, their primary purpose is to improve its mechanical properties.

**Clinical Pearl / High-Yield Fact**
When using ZOE cement with synthetic resins, it's essential to ensure proper mixing and handling to avoid introducing air bubbles or other defects that can compromise the cement's strength and durability.

**Correct Answer: C.**