## Core Concept
Nickel-titanium (Ni-Ti) alloys, also known as Nitinol, are a type of shape-memory alloy used in various medical applications, including orthodontics. These alloys exhibit unique properties such as superelasticity and shape-memory effect, making them suitable for orthodontic wires. The introduction of Ni-Ti alloys in orthodontics revolutionized the field by providing wires that could apply consistent forces over a range of activations.

## Why the Correct Answer is Right
George A. M. Andreasen introduced Nickel-titanium alloy as an orthodontic wire. This alloy was notable for its superelastic properties, which allowed it to return to its original shape after deformation, providing a consistent force to the teeth. This characteristic made Ni-Ti wires highly desirable in orthodontics for tooth movement.

## Why Each Wrong Option is Incorrect
* **Option A:** While there are many contributors to orthodontics, the specific introduction of Nickel-titanium alloy is attributed to a particular individual.
* **Option B:** Similarly, another figure in orthodontics, but not credited with the introduction of Ni-Ti alloy.
* **Option D:** This option is also incorrect as it does not correspond with the historical introduction of Nickel-titanium alloy in orthodontics.

## Clinical Pearl / High-Yield Fact
The introduction of Nickel-titanium alloys in orthodontics is a significant milestone. These alloys are widely used today due to their beneficial properties, such as reduced friction, biocompatibility, and the ability to deliver light, continuous forces. A key point to remember is that Ni-Ti wires are especially useful in the initial stages of orthodontic treatment for aligning teeth.

## Correct Answer: B. George A. M. Andreasen