**Core Concept**
The question is testing the student's knowledge of the appropriate dental brush for maintaining healthy gingiva. The correct answer is based on the principle of gentle yet effective plaque removal without causing trauma to the gingival tissues.

**Why the Correct Answer is Right**
The correct answer is a soft-bristled toothbrush, which is designed to remove plaque and bacteria from the teeth without causing damage to the gingiva. Soft-bristled brushes are generally preferred over hard-bristled brushes because they are gentler on the gums and can help prevent gingival recession. The soft bristles are also less likely to cause bleeding or irritation, making them an ideal choice for patients with sensitive teeth or gums.

**Why Each Wrong Option is Incorrect**
* **Option A:** A hard-bristled toothbrush is too aggressive for normal healthy gingiva, as it can cause bleeding, irritation, and gingival recession. Hard bristles can also damage the enamel on the teeth.
* **Option B:** An electric toothbrush is not necessarily the best choice for normal healthy gingiva, as it can be too abrasive if not used properly. However, an electric toothbrush can be beneficial for patients with poor manual dexterity or those who have a hard time removing plaque with a manual toothbrush.
* **Option C:** An ultrasonic toothbrush is not typically recommended for normal healthy gingiva, as it is usually used for patients with periodontal disease or other conditions that require a more intense cleaning.

**Clinical Pearl / High-Yield Fact**
When choosing a toothbrush, it's essential to select one with soft bristles and a small head to effectively clean the teeth and gums. Patients should also be instructed to replace their toothbrush every 3-4 months or sooner if the bristles become frayed.

**Correct Answer:** C. An ultrasonic toothbrush is not typically recommended for normal healthy gingiva.