What are the complaints that require root canal treatment? Is there pain during canal treatment?

Spontaneous pain in teeth,
Increased pain at night and not even with painkillers,
Long-lasting pain triggered by an external agent, such as cold, hot, or contact with the tooth, swelling around the tooth, gingiva and / or related lymph glands.
However, teeth that have lost their vitality may not cause any complaints. This should not be perceived as the lack of need for root canal treatment.

Canal therapy does not cause pain; on the contrary, it is applied for pain relief. Teeth and surrounding tissues to be treated for root canal anesthesia are anesthetized. The patient does not feel pain during treatment. However, in some cases the patient may experience minor discomfort. This problem is easily overcome by performing auxiliary anesthesia.