23/07/2025
Why a tooth with deep caries hurts so badly?
When a cavity goes deep into the tooth, the pain it causes is not just due to damage — it’s because the decay reaches the tooth’s nerve center, known as the dental pulp. This inner core contains blood vessels and sensitive nerve fibers that are directly connected to the brain.
As bacteria from the cavity invade the pulp, they trigger inflammation. But since the pulp is trapped inside a hard tooth structure, the swelling has nowhere to go. This builds pressure inside the tooth, causing the nerves to become compressed and irritated — leading to sharp, throbbing, or lingering pain.
The pain signal travels through the trigeminal nerve — the main nerve that connects your face, jaw, and teeth to the brain. Once this signal reaches the brainstem and sensory centers, it’s processed as severe tooth pain. This is also why pain from a single tooth can sometimes feel like it’s spreading to the jaw, ear, or head.
There are two main types of nerve fibers inside the pulp. The fast-acting A-delta fibers cause sharp, quick pain — like a shock from cold water. The slower C-fibers create a deeper, more constant ache — like a dull throb that doesn’t go away. When both are activated due to deep decay or infection, the pain becomes intense and difficult to manage.
This level of toothache usually means the pulp is infected or dying. At this point, a filling is no longer enough. The tooth may require root canal treatment to remove the damaged nerve and prevent further complications.
Understanding this connection between deep cavities, nerves, and the brain helps explain why dental pain can be so intense — and why early treatment is critical.
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