Local Anesthesia Pain: Why Root Canal and Palate Injections Hurt and How to Reduce the Pain

Why does root canal anesthesia hurt so much?

Root canal anesthesia can hurt especially badly because, at the moment the anesthetic directly reaches a nerve that is already severely inflamed and painful, a brief, intense jolt can occur [1][2]. When DentStat analyzed 420 comments in the local anesthesia pain cluster, patients described this pain with strong expressions such as “like being struck by lightning” and “an electric shock,” and these experiences emerged as a root reason people seek sedation [3]. However, anesthetizing the adjacent gum first and then approaching the root canal can sometimes reduce the pain, so the pain felt for the same procedure may differ depending on the dentist’s technique [1].

If the inflammation is severe, will stronger anesthesia work?

In severely inflamed areas, simply increasing the strength does not make anesthesia work well [1]. Inflamed tissue becomes acidic, which makes it hard for local anesthetic to penetrate fully to the nerve [1]. In such cases, the inflammation is sometimes calmed first, or supplemental anesthesia such as a nerve block placed near the nerve trunk is added [1]. Rather than forcing treatment while acute pain is severe, controlling the inflammation first is a route to less pain [1].

Do palate injections and lower molar anesthesia always hurt?

Some areas can feel very painful, but saying they “always hurt” is an overgeneralization [1]. The tissue of the palate is firm and sensitive to pain, so the injection can feel intense, but applying topical anesthetic first, injecting slowly, or adding supplemental anesthesia by another route can sometimes ease it [1]. Lower molars are harder to anesthetize because of thick bone and the position of the nerve, but nerve blocks or additional supplemental anesthesia can sometimes manage it [1]. Comments repeatedly claimed that “lower molars can’t be numbed” [3], but this is something technique can address [1].

What are the ways to reduce local anesthesia pain?

Reducing pain begins before the injection [1]. Numbing the tissue with a topical anesthetic before the injection and keeping the injection speed slow and steady are known to reduce injection pain [1]. In root canal treatment, anesthetizing the adjacent gum first and then approaching the root canal is used to ease pain, and nerve blocks and supplemental anesthesia are combined depending on the area [1]. Even with these methods, pain does not disappear completely, and results vary by area and by person [1].

Common myths and facts

Some believe that stronger anesthesia works even with severe inflammation, but anesthetic does not penetrate inflamed areas well, so treatment sometimes waits until the inflammation calms [1]. The idea that root canal anesthesia always hurts that much is also a misconception, since pain differs with pre-anesthesia and technique [1]. The belief that the injection itself is always the worst part is likewise not fixed, as topical anesthetic and slower injection can reduce it. The causes of pain and how to deal with them differ by area [1][3].

For the difference between “painless anesthesia,” which reduces injection pain, and sedation, which lowers consciousness and anxiety, see the sedation dentistry and anesthesia guide. For dental clinics by region, see Find a Dentist.