**Core Concept**
The ideal finish line configuration for a porcelain veneer is critical to ensure adequate support, prevent chipping or fracture, and facilitate proper cementation. A well-designed finish line should ensure a strong bond between the veneer and the tooth, while also minimizing the risk of tooth decay or sensitivity.

**Why the Correct Answer is Right**
The correct finish line configuration for a porcelain veneer is a Chamfer finish line. This design features a 90-degree angle between the tooth surface and the finish line, with a rounded or beveled edge to reduce stress concentrations. The Chamfer finish line provides a strong mechanical bond between the veneer and the tooth, while also allowing for easy cementation and minimizing the risk of tooth decay or sensitivity.

**Why Each Wrong Option is Incorrect**
* **Option A:** A Shoulder finish line is not ideal for porcelain veneers as it can create a ledge for plaque accumulation and increase the risk of tooth decay.
* **Option B:** An Over-contoured finish line can compromise the structural integrity of the veneer and increase the risk of chipping or fracture.
* **Option C:** An Under-contoured finish line can lead to inadequate support for the veneer, resulting in instability and increased risk of tooth decay or sensitivity.

**Clinical Pearl / High-Yield Fact**
When designing a finish line for a porcelain veneer, it's essential to consider the individual patient's needs and the specific requirements of the veneer. A well-designed finish line can significantly impact the longevity and success of the veneer, and a Chamfer finish line is generally considered the most ideal configuration.

**Correct Answer: C. Chamfer finish line**