Fibres which transmit fast pain from pulp are

**Core Concept**
The transmission of pain from the pulp of a tooth is mediated by the trigeminal nerve, which has different types of nerve fibers responsible for transmitting various types of pain. These fibers can be classified based on their conduction velocity, which determines the speed at which they transmit pain signals.

**Why the Correct Answer is Right**
Fast pain from the pulp is transmitted by A-delta fibers, which are a type of unmyelinated nerve fiber. These fibers have a conduction velocity of 12-25 meters per second, making them the fastest type of pain-transmitting fibers in the body. They are responsible for transmitting sharp, stabbing pain, which is characteristic of pulpitis.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because A-beta fibers, which are another type of nerve fiber, are responsible for transmitting touch and pressure sensations, not fast pain.
* **Option B:** This option is incorrect because C-fibers, which are a type of unmyelinated nerve fiber, are responsible for transmitting slow, dull pain, not fast pain.
* **Option D:** This option is incorrect because B-fibers do not exist as a distinct type of nerve fiber; the correct classification is A-delta, A-beta, A-gamma, and A-alpha fibers.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the transmission of pain from the pulp is a complex process that involves multiple types of nerve fibers. A-delta fibers are responsible for transmitting fast pain, while C-fibers transmit slow pain.

**Correct Answer: A. A-delta fibers.**