**Core Concept**
High-speed instrumentation in dentistry refers to the use of advanced technologies like air-abrasion systems and ultrasonic devices to remove tooth structure and restore dental tissues. This concept is crucial in understanding the advantages and disadvantages of high-speed instrumentation in dental procedures.

**Why the Correct Answer is Right**
High-speed instrumentation offers several benefits, including efficient removal of tooth structure, reduced vibration, and improved control. However, one significant disadvantage is the potential for **over-preparation** of dental tissues. Over-preparation can lead to excessive removal of healthy tooth structure, compromising the longevity of the restoration and increasing the risk of post-operative sensitivity.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because high-speed instrumentation does not typically result in **under-preparation** of dental tissues. In fact, the opposite is true: high-speed instrumentation can lead to over-preparation of dental tissues.
* **Option B:** This option is incorrect because high-speed instrumentation does not typically result in **poor control** over the removal of tooth structure. Instead, high-speed instrumentation often provides improved control and precision in dental procedures.
* **Option C:** This option is incorrect because high-speed instrumentation does not typically result in **inadequate removal** of tooth structure. In fact, high-speed instrumentation is often used to efficiently remove tooth structure and restore dental tissues.

**Clinical Pearl / High-Yield Fact**
One important consideration when using high-speed instrumentation is to maintain a **fine control** over the device and to use it judiciously to avoid over-preparation of dental tissues.

**Correct Answer: D. Over-preparation of dental tissues.**