**Core Concept**
The core concept being tested here is the proper placement technique for dental restorations, specifically the avoidance of complications that can arise when this technique is not followed. In dentistry, restorations such as dental veneers or crowns are bonded to the tooth using a strong adhesive to restore its shape, size, and function.

**Why the Correct Answer is Right**
Proper placement technique involves careful etching of the tooth surface, application of bonding agents, and precise placement of the restoration. If this technique is not followed, the restoration may not adhere properly to the tooth, leading to debonding or separation of the restoration from the tooth. This can occur due to inadequate etching, poor bonding agent application, or incorrect placement of the restoration. The lack of proper bonding can result in the restoration coming loose over time, compromising its effectiveness and requiring additional dental work to repair or replace it.

**Why Each Wrong Option is Incorrect**
* **Option A:** Tooth sensitivity is a common complication of dental restorations, but it is not directly related to improper placement technique. Sensitivity can be caused by a variety of factors, including the type of restorative material used, the presence of decay or cracks in the tooth, or the exposure of the pulp.
* **Option B:** Wear of opposing teeth can occur due to a variety of factors, including improper bite alignment, grinding or clenching habits, or the use of restorations that are too thin or poorly designed. However, it is not a direct consequence of improper placement technique.
* **Option D:** Healthy gingiva is a desirable outcome of dental restorations, but it is not a direct consequence of improper placement technique. In fact, improper placement technique can lead to a range of problems, including gingival irritation, inflammation, or recession.

**Clinical Pearl / High-Yield Fact**
When placing dental restorations, it is essential to follow a proper placement technique to ensure a strong, durable bond between the restoration and the tooth. This involves careful etching of the tooth surface, application of bonding agents, and precise placement of the restoration. Failure to follow this technique can result in debonding or separation of the restoration, compromising its effectiveness and requiring additional dental work to repair or replace it.

**✓ Correct Answer: C. Debonded restoration.**