## Core Concept
Toothache relief with cold water is related to the dental condition causing the pain. This phenomenon is often associated with **pulpitis**, specifically **irreversible pulpitis** or **reversible pulpitis**, where the pulp's response to thermal stimuli can provide diagnostic clues.

## Why the Correct Answer is Right
The correct answer, **D. reversible pulpitis**, is right because reversible pulpitis often presents with pain that can be relieved by cold water. Cold water can reduce inflammation and decrease the metabolic rate of the pulp, thereby reducing pain. In reversible pulpitis, the pulp is inflamed but still has the potential to heal. Cold stimuli can sometimes alleviate the pain temporarily by reducing the inflammatory process.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is incorrect because it does not specify a condition related to toothache and cold water relief.
- **Option B:** This option is incorrect as it does not relate to the typical dental conditions associated with toothache relief by cold water.
- **Option C:** This option is incorrect because it does not accurately represent a dental condition that would be specifically relieved by cold water.

## Clinical Pearl / High-Yield Fact
A key clinical pearl is that **cold water relief** in the context of toothache often points towards **pulpitis**. However, the specificity of this symptom can vary, and a thorough clinical examination, including thermal tests, is essential for diagnosis. Remember, reversible pulpitis might be reversible with proper dental intervention, making early diagnosis crucial.

## Correct Answer: D. reversible pulpitis