Hi .. a decayed tooth with symptoms of pain, sensitivity suggests the decay is deep. A deep cavity with pain etc suggests the need for a root canal treatment. Sometimes, the infection is too severe and pain is absent..so pain is not the only criteria.Not getting appropriate treatment can spread the infection beyond the tooth and into the bone!

Absence of pain does not always indicate absence of infection. Not getting the treatment done in time can definitely cause the symptoms to aggravate in the future. And this may even lead to a condition where the tooth becomes non restorable and will require extraction only. The degree of decay can be accessed by the clinical condition of the tooth as well as an x-ray to evaluate the depth of the cavity. Regards.