**Core Concept**
Night guard bleaching is a type of at-home teeth whitening technique that utilizes a custom-fitted mouthguard to apply a bleaching agent to the teeth. This method is often recommended for patients with mild to moderate discoloration and is particularly effective for removing stains that are extrinsic (outside the tooth).

**Why the Correct Answer is Right**
The process involves creating a custom-fitted mouthguard that is worn over the teeth while sleeping. The mouthguard is saturated with a peroxide-based bleaching gel, which is then activated by the heat and moisture generated during sleep. As the patient sleeps, the bleaching agent penetrates the tooth enamel and breaks down chromogens (colored molecules) that cause tooth discoloration. This results in a gradual whitening of the teeth over several nights.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the use of a custom-fitted mouthguard, which is a key component of night guard bleaching.
**Option B:** This option is incorrect because it is too vague and does not accurately describe the night guard bleaching technique.
**Option C:** This option is incorrect because it is a different type of teeth whitening technique that involves the use of a high-concentration bleaching agent in a dentist's office.

**Clinical Pearl / High-Yield Fact**
It's essential to note that night guard bleaching is most effective for patients with mild to moderate discoloration and may not be suitable for those with severe stains or intrinsic discoloration.

**Correct Answer: B. Night guard bleaching is a type of at-home teeth whitening technique that utilizes a custom-fitted mouthguard to apply a bleaching agent to the teeth.**