Will my root canal hurt?
The honest answer is: a properly performed root canal in 2026 should not hurt. The hard part isn't the procedure — it's getting you fully numb when the tooth is already inflamed. Here's what we do about that.
Written by Dr. Jason C. Kung, DDS, MS — Specialist Endodontist, Sunnyvale CA
First author of Articaine vs Lidocaine in Irreversible Pulpitis: A Systematic Review and Meta-analysis (Kung, McDonagh, Sedgley — Journal of Endodontics, 2015) — the meta-analysis other endodontists cite when choosing anesthetic for difficult cases.
Why anesthesia sometimes fails (and how we plan for it)
When a patient says "I had a root canal once and it hurt," the cause is almost never the procedure itself — it's that the tooth was never fully anesthetized to begin with. There's a well-documented reason this happens, and a well-documented set of solutions.
Inflamed pulp tissue is biochemically resistant to local anesthetic. The sodium channels on inflamed nerves respond differently — a dose that completely numbs a healthy tooth may leave a "hot" tooth only partially numb. This is especially true for lower (mandibular) molars, where the standard inferior alveolar nerve block has a documented failure rate of roughly 20–40% in patients with symptomatic irreversible pulpitis.
Most general dentists know this in theory. The difference in a specialist office is that we plan for it before we touch the tooth.
- ·Anesthetic selection. We use articaine for difficult mandibular cases as a supplemental buccal infiltration. The evidence base for this — including Dr. Kung's own meta-analysis — is what guides modern endodontic practice.
- ·Supplemental techniques. If the primary block doesn't take, we use intraosseous, intraligamentary, or intrapulpal anesthesia — not "let's just start and see how it goes."
- ·Test before we start. We confirm full pulpal anesthesia with a cold test (Endo-Ice) before we open the tooth. If you can still feel cold sharply, you're not numb enough. We wait, supplement, and re-test.
- ·Permission to stop. If anything sharp comes through during treatment, raise your left hand. We stop, add anesthetic, and resume only when you're fully comfortable. This is a standing rule, not a special favor.
What you'll actually feel — minute by minute
Minutes 0–5: The injection
Topical numbing gel first. Then the actual injection is slow — a fast injection is what hurts, not the needle itself. You'll feel pressure and a pinch. Most patients describe it as "less than I expected."
Minutes 5–15: Waiting for numbness
Lip and cheek tingle and feel heavy. We test the tooth with cold to confirm pulpal anesthesia before we start. If you're not fully numb, we wait or supplement.
Minutes 15–60: The procedure itself
You'll feel pressure, vibration from the handpiece, and water rinsing. You'll hear the suction. You should not feel sharp pain. If you do, raise your hand — we stop.
After the appointment: 2–4 days of soreness
Mild tenderness when biting is normal as the surrounding tissue heals. Ibuprofen 600 mg with acetaminophen 1000 mg, taken together every 6 hours, controls this for almost everyone — the combination outperforms most opioids for dental pain. Severe pain is uncommon and we want to know about it.
A specialist endodontist performs root canals all day, every day. Dr. Kung completed three additional years of full-time residency training in endodontics at Oregon Health & Science University after dental school — including hospital-based training at St. Barnabas Hospital, a Level 1 Trauma Center. Most general dentists do a handful of root canals per month; we do 10–20 per week, with the equipment and training to handle the difficult cases other offices refer out.
Common questions
Will I feel anything during the root canal?
You should feel pressure and movement, but not sharp pain. If you do, tell us — we add anesthetic right away. We don't ask you to 'tough it out.'
Why do some people say their root canal hurt?
Almost always one of three things: (1) the tooth had severe pre-treatment infection that made anesthesia harder to achieve, (2) the dentist relied on a single inferior alveolar nerve block on a hot lower molar (a setup with known failure rates), or (3) the procedure was rushed. We address all three: we plan for difficult anesthesia ahead of time, use supplemental techniques when needed, and reschedule rather than push through if a tooth won't get fully numb.
What about after the appointment — will I be in pain?
Most patients have mild soreness for 2–4 days that responds to ibuprofen and acetaminophen taken together (the combination is more effective than either drug alone, and more effective than most opioids for dental pain). Severe post-op pain is uncommon and usually means we need to see you back — not that you should suffer through it.
Do you use sedation?
Yes — for anxious patients we offer both nitrous oxide (laughing gas) and oral sedation. Nitrous is mild, takes effect in minutes, wears off in minutes, and you can drive yourself home afterward. Oral sedation (a single pill taken before the appointment) provides deeper relaxation; you'll need someone to drive you to and from the visit. Many patients don't need either — the local anesthesia itself, done well, is what controls pain — but if anxiety is a concern, tell us at intake and we'll plan for it. We don't currently offer IV sedation.
I'm pregnant / nursing / on blood thinners — is the anesthesia safe?
Yes, in nearly all cases. The local anesthetics we use have decades of safety data in pregnancy and breastfeeding. If you're on blood thinners or have other medical concerns, tell us at intake and we'll coordinate with your physician if needed.
I have a needle phobia. What can you do?
Topical numbing first, slow injection, distraction, and conversation throughout. Many patients with needle phobia tell us afterward they didn't feel the injection. If anxiety is severe, talk to us before scheduling — both nitrous oxide (laughing gas) and oral sedation are available and very effective for taking the edge off. We'll figure out together which option fits you best.
Why does my tooth still hurt a week after my root canal?
Some tenderness for 3–5 days is normal — the tissue around the root tip is healing. The American Association of Endodontists' post-treatment patient guidance notes that mild discomfort lasting a few days is expected, but pain that intensifies or persists beyond 1–2 weeks warrants follow-up. Common causes of lingering discomfort are a high spot on the bite that needs adjustment, inflammation that simply needs more time, or a hairline crack we should re-evaluate. Persistent infection is rare but is the reason we follow up with you.
Can I take ibuprofen and acetaminophen (Tylenol) together after a root canal?
Yes — combined ibuprofen 600 mg + acetaminophen 1000 mg every 6 hours is the most effective non-opioid pain regimen and is the recommended first-line approach in the 2024 ADA Clinical Practice Guideline on the Pharmacologic Management of Acute Dental Pain (endorsed by the AAE). Take them on schedule for the first 24–48 hours rather than waiting for pain. Skip ibuprofen if you have kidney disease, are on blood thinners, or in the third trimester of pregnancy — acetaminophen alone is the safer choice.
Is a root canal more painful than just having the tooth pulled?
No. With modern anesthesia and microscope-guided technique, root canal treatment is comparable in discomfort to a routine filling during the procedure, and recovery is typically milder than after a surgical extraction (no socket healing, no dry-socket risk). The American Association of Endodontists' patient education ("Myths About Root Canals") notes that patients who have had both procedures consistently rate root canal treatment as the more comfortable experience.
Dr. Kung's research on root canal anesthesia
While at Oregon Health & Science University, Dr. Kung was the first author on a systematic review and meta-analysis published in the Journal of Endodontics — the field's leading peer-reviewed journal — on whether articaine offers an advantage over lidocaine in patients with symptomatic irreversible pulpitis (the medical term for the kind of severe toothache that brings most patients to an endodontist).
The paper is one of the references the American Association of Endodontists points to in its own guidance to specialists on local anesthesia. It's read and cited by other endodontists worldwide. When you're treated in this office, the anesthesia plan reflects that evidence — applied by the person who helped write it.
Read the abstract on PubMedKung J, McDonagh M, Sedgley CM. Does Articaine Provide an Advantage over Lidocaine in Patients with Symptomatic Irreversible Pulpitis? A Systematic Review and Meta-analysis. Journal of Endodontics. 2015;41(11):1784–1794.
Root canal treatment — serving 30+ Bay Area cities
Dr. Jason Kung provides root canal treatment to patients across Silicon Valley from our Sunnyvale office. Evening and weekend hours, same-day emergencies, free on-site parking.
Ready to get the tooth taken care of?
Most patients walk out of our office saying "that was nothing like what I expected." We'd like to be the office where that's true for you, too.
Related: Watch: Does a root canal hurt? · How do I know if I need a root canal? · Can I be sedated for a root canal? · Is it safe to get a root canal while pregnant? · Root Canal Treatment · Why a root canal sometimes won't go numb · After Your Root Canal · About Dr. Kung
