Filling or Root Canal? How Dentists Decide

A common question patients ask after an X-ray is why one cavity gets a simple filling while another needs a full root canal. The answer comes down to how deep the decay has gone, not how big the cavity looks from outside. The tooth's layers A tooth has three layers: enamel on the outside, dentin underneath, and the pulp at the centre, which contains nerves and blood vessels. Decay that stays within enamel and dentin can usually be cleaned out and filled. Once decay reaches the pulp, filling alone will not solve the problem, because the nerve inside is now infected or dying. Signs the pulp is involved Persistent pain, especially pain that lingers well after eating something hot or cold, pain that wakes you up at night, or visible darkening of the tooth are all signs the pulp may be affected. A dentist confirms this with an X-ray and sometimes a cold test to check how the nerve responds. Why filling alone would not work If the pulp is infected and only a filling is placed, the infection continues underneath, often leading to an abscess, swelling, or worse pain later. A root canal removes that infected tissue, cleans the canal, and seals it so no bacteria remain, allowing the filling or crown placed afterward to actually last. What if you catch it early? This is exactly why regular check-ups matter. A cavity caught while it is still small and confined to enamel is a routine filling, quick and inexpensive. The same cavity left untreated for a year can progress to needing a root canal, simply because it had time to reach the pulp. If you have a tooth that is sensitive or aching, message us on WhatsApp and we will examine it and tell you plainly which treatment it actually needs.