A missed canal in the original treatment
Upper first molars have a fourth canal (MB2) in ~90% of cases that is invisible without a microscope. Missed canals are the single most common cause of late-onset root canal failure.
Second opinions · CBCT review · Honest assessment
The Bay Area's specialist for failed root canals
A previous root canal that's still painful, swollen, or showing signs of infection on X-ray can almost always be saved — if the cause of failure is correctly diagnosed. Dr. Jason Kung performs microscope-guided, CBCT-planned retreatment for patients across the Bay Area, with the same honest pre-treatment assessment we'd want for our own family.
Medically reviewed by Dr. Jason Kung, DDS, MS · Specialist Endodontist · UCLA DDS · OHSU MS ·
Why root canals fail
Failure has four common causes, and the right treatment depends entirely on which one applies to your tooth. CBCT 3D imaging usually identifies the cause within minutes.
Persistent or re-entered bacteria
New decay under a leaking crown, a fractured restoration, or incomplete disinfection of complex anatomy can allow bacteria to re-colonize the canal system months or years after the original treatment.
A vertical root fracture
About 5–10% of 'failed' root canals are actually fractured roots that can't be saved. CBCT 3D imaging and microscope-guided crack tracing are the only reliable ways to distinguish a salvageable tooth from one that isn't — before you spend money on retreatment.
An undiagnosed extra-radicular infection
Some lesions don't resolve with non-surgical retreatment because the infection sits outside the root, in the surrounding bone. These cases need apicoectomy (microsurgery) rather than retreatment — a distinction CBCT usually makes obvious.
What we do differently
Most general dentists and many endodontists do not have CBCT or a surgical microscope. Both are considered standard of care for retreatment under contemporary AAE clinical guidelines.
- CBCT 3D imaging on every retreatment evaluation — not just X-rays. CBCT changes the treatment plan in ~30% of cases compared to 2D imaging alone.
- Carl Zeiss surgical operating microscope at 4×–25× magnification used through the entire procedure — required for locating missed canals and detecting fractures.
- Honest pre-treatment assessment. If the tooth isn't salvageable, we tell you before you commit to retreatment. About 1 in 8 patients who arrive for retreatment leave with a different recommendation — extraction + implant, apicoectomy, or 'leave it alone and monitor.'
- Direct written report to your referring or general dentist within 24 hours, with annotated CBCT images and a clear restoration plan.
- Saturday and Sunday availability for patients traveling from Cupertino, Mountain View, Palo Alto, San Jose, and across the Peninsula.
Frequently asked questions
Do you charge for a second-opinion evaluation on a failed root canal?+
We charge a standard consultation and CBCT fee — typically $250–$450 depending on whether 3D imaging is needed. Most PPO plans reimburse a portion of this. We give you the CBCT images and a written report to take with you, regardless of where you decide to have the work done.
Should I just have the tooth extracted and get an implant instead?+
Modern non-surgical retreatment succeeds in 78–87% of cases (Sabeti et al., Journal of Endodontics 2024). Implants survive at ~95% over 10 years, but the comparison isn't apples-to-apples: implants don't preserve the periodontal ligament, don't transmit chewing forces the same way, and require bone grafting in many failed-root-canal sites because the infection has already destroyed bone. For most patients, retreatment is the more conservative, less expensive, and biologically superior first step — extraction can always be done later if retreatment fails.
Patients drive to you from Cupertino, Mountain View, and Palo Alto — how is that worth the trip?+
Most general dentists and many endodontists do not have CBCT 3D imaging or a surgical operating microscope. Both are considered standard of care for retreatment by the American Association of Endodontists' contemporary clinical guidelines. Patients drive 20–40 minutes for the same reason they would drive to see an oral surgeon or orthodontist — sub-specialty cases benefit measurably from sub-specialty tooling.
How long does a retreatment appointment take?+
Most retreatments are completed in a single 90–120 minute appointment. Complex cases (multi-canal molars with calcified canals, separated instruments, or post-and-core removal) may require two visits. CBCT review and treatment planning happen at the consultation visit before any treatment is scheduled.
Will my general dentist or previous endodontist be offended that I came for a second opinion?+
No. Sub-specialty referrals are a normal part of dental practice. We send a respectful written report back to your referring dentist explaining what we found and what we recommend. The vast majority of GPs welcome the additional information — they want what's best for the patient.
Can you do retreatment on a weekend?+
Yes. We're open Saturday and Sunday from 9 AM to 3 PM. Weekend retreatment fees are identical to weekday fees. Call (669) 234-2354 to confirm availability.
Does insurance cover retreatment?+
Most PPO dental insurance covers retreatment as a major service (typically 50–80% after deductible), using ADA codes D3346 (anterior), D3347 (premolar), and D3348 (molar). Coverage is identical to a first-time root canal in nearly all plans. We are out-of-network for most PPO carriers but submit claims directly so you receive your full PPO benefits at our negotiated fees.
Patients travel from
SunnyvaleCupertinoMountain ViewSanta ClaraSan JosePalo AltoLos AltosSaratogaCampbellMilpitasRedwood CityMenlo ParkFremont
Bring us the X-ray. We'll tell you the truth.
If retreatment is the right answer, we'll tell you. If it isn't, we'll tell you that too — and refer you to whoever can help.
Related on this site
- Retreatment procedure detailsStep-by-step explanation of what retreatment involves.
- Apicoectomy (microsurgery)Surgical option when non-surgical retreatment isn't appropriate.
- Root resection & hemisectionSaving a multi-rooted molar by removing one diseased root — when it works and when it doesn't.
- Second-opinion consultationsWhat to bring, what to expect, and what we'll tell you.
- Weekend availabilitySaturday and Sunday appointments for traveling patients.
- Why CBCT mattersHow 3D imaging changes treatment plans in ~30% of cases.