The deciding question is whether the pulp is still healthy
A tooth has an outer layer of enamel, a softer layer of dentine beneath it, and the pulp at its centre, which holds the nerve and blood supply. A filling replaces the enamel and dentine lost to decay. A root canal removes the pulp itself when it can no longer recover.
So the choice is not about how big the hole is on the surface. A large cavity can still have a healthy nerve, and a small-looking one can hide decay that has tracked sideways to the pulp. This is why an X-ray is part of the decision. For more on how cavities progress, see our guide on cavities in teeth.
Signs that usually point to a filling
A short, sharp twinge to cold, sweet food or air that goes within a few seconds of the trigger being removed. Food catching in a visible hole. A dark spot or rough patch that does not hurt. These suggest the pulp is irritated but able to recover once the decay is removed and the tooth is sealed.
Different filling materials suit different teeth, and types of dental fillings compares them. Costs and details are on our tooth fillings page.
Signs that usually point to a root canal
Pain that lingers for minutes after hot or cold has gone. Throbbing or spontaneous pain, particularly at night. Pain on biting, a swollen or tender gum, a pimple on the gum, or a tooth that has darkened. These suggest the pulp is inflamed beyond recovery or has died, often with infection at the root tip.
Treating this with a filling alone does not work, because the infection stays inside the tooth. The sequence of treatment is described in root canal treatment steps, and the pillar page is root canal treatment.
The grey area, and what the dentist does about it
Sometimes a deep cavity leaves the dentist unsure whether the pulp will survive. One approach is to remove the decay, place a protective lining over the nearest point to the nerve and fill the tooth, then review. If the tooth settles, a root canal is avoided. If lingering pain starts, root canal is the next step.
Be wary of a pain that has stopped suddenly without treatment. When a nerve dies, pain can disappear while infection continues quietly, and it may return as swelling. A tooth that stops hurting should still be examined.
Delay usually moves a filling toward a root canal. A filling in Lucknow costs ₹500 to ₹3,000, and a root canal ₹3,000 to ₹9,000 plus a crown on a back tooth, so early treatment is usually the cheaper path. Details are on our root canal cost in Lucknow page.
Common questions
Can a deep filling turn into a root canal later?
Yes. If decay was very close to the nerve, the pulp can stay inflamed after the filling and later die. Lingering pain, night pain or a tooth that becomes tender to bite are the signs that a root canal may now be needed.
Can a root canal be avoided by taking painkillers?
No. Painkillers mask the symptom without treating the cause. A pulp that is infected will not heal on its own, and the infection can spread into the bone and face. Painkillers are for the short gap before the appointment.
Does sensitivity to cold mean I need a root canal?
Not usually. Brief sensitivity that fades in seconds often means a cavity, exposed root or worn enamel that a filling or desensitising treatment can handle. Pain that lingers for minutes, or wakes you at night, is the pattern that suggests the pulp is involved.
Is a root canal always followed by a crown?
On back teeth, almost always, because the tooth is weakened and prone to fracture. Front teeth with a small opening can often be restored with a filling alone. The dentist decides based on how much tooth remains.
How do I know if the infection has spread?
Swelling of the face or gum, fever, or a bad taste with a pimple on the gum suggest spreading infection. Seek care the same day. If swelling affects breathing or swallowing, go to a hospital emergency department immediately.
About this page
This page is general information, not a diagnosis or a quotation. Prices are prevailing Lucknow market ranges. Your own treatment and cost are determined after an examination. For questions about your own case, call +91 83036 12717.