## **Core Concept**
The use of pins in dental amalgam restorations is a technique to enhance retention in cases where the tooth structure is severely compromised. The pins help in mechanically retaining the amalgam within the tooth. However, the interaction between the pins and the amalgam can affect the physical properties of the amalgam.

## **Why the Correct Answer is Right**
The correct answer, **C. decreases**, is right because the incorporation of pins into the amalgam restoration can disrupt the homogenous structure of the amalgam, creating stress concentrations and potentially weakening the restoration. The pins can act as sites for crack initiation under stress, thereby reducing the overall strength of the amalgam.

## **Why Each Wrong Option is Incorrect**
- **Option A: increases** - This option is incorrect because while pins do provide additional retention, they do not inherently increase the strength of the amalgam itself. In fact, they can have the opposite effect by introducing defects.
- **Option B: remains same** - This option is incorrect because the presence of pins does alter the mechanical properties of the amalgam. It does not simply leave the strength unchanged.
- **Option D: increases in compression and decreases in tension** - This option, although partially correct in describing specific stress conditions, is not the best answer because it does not directly address the general effect on strength as asked by the question.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that pins are used in amalgam restorations primarily for retention in teeth with significant structural loss. However, their use comes with potential drawbacks, including the risk of weakening the amalgam and the possibility of pulpal damage or pin perforation. Clinicians must weigh these risks against the benefits.

## **Correct Answer:** C. decreases.